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DOE F 241.3 (2-01) p. 1 of 4

UNITED STATES DEPARTMENT OF ENERGY (DOE)
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Assistance Recipients and Non-M&O/M&I Contractors PART I: STI PRODUCT DESCRIPTION (To be completed by Recipient/Contractor H. Sponsoring DOE Program Office US DOE I. Subject Categories (list primary one first) 01 Coal, lignite, and peat J. Description/Abstract Energy savings assessment of a coal mine K. Intellectual Property/Distribution Limitations (must select at least one; if uncertain contact your Contracting Officer (CO)) UNLIMITED ANNOUNCEMENT (available to U.S. and non-U.S. public; the Government assumes no liability for disclosure of such data) COPYRIGHTED MATERIAL: Are there any Yes No restrictions based on copyright?
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2. DOE AWARD/CONTRACT NUMBER(s) DE-FC36-04Go14034 3. OTHER IDENTIFYING NUMBER(s) none B. Recipient/Contractor Powder River Coal Co. C. STI Product Title Powder River Coal Plant Wide Assessment D. Author(s) Glenn B. fosmo

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DOE F 241.3 (2-01) p. 2 of 4

UNITED STATES DEPARTMENT OF ENERGY (DOE)
Scientific and Technical Information (STI) For Financial

OMB Control No. 1910-1400

ANNOUNCEMENT

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PART II: STI PRODUCT MEDIA/FORMAT and LOCATION/TRANSMISSION (To be completed by Recipient/Contractor) A. Media/Format Information: 1. MEDIUM OF STI PRODUCT IS: Electronic Document Computer medium Audiovisual material Paper No full-text 2. SIZE OF STI PRODUCT 64 pages 3. SPECIFY FILE FORMAT OF ELECTRONIC DOCUMENT BEING TRANSMITTED, INDICATE:
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Final Technical Report Powder River Coal Company Plant Wide Assessment
The following report contains information pertaining to a Plant Wide Assessment done by Powder River Coal Company, through the use of a Rockwell Automation Power and Energy Management Solutions group (PEMS) and employees of North Antelope Rochelle Mine (NARM). A scope of work was determined by NARM personnel and the Rockwell PEMS group to analyze existing systems and energy uses, along with suggestions and solutions for Energy Conservation Measures (ECM).

Scope of Work:
Description of the existing facility and operation of 3 mines Description of the existing processes and operation of 3 mines A summary of the data gathered during the process of 3 mines Utility Data kWh consumption and cost kW demand and cost Load Factor Power Factor Summary of the Energy Conservation Measures, ECM’s found during the survey including: ♦ Estimate of the energy savings for each ECM ♦ Identify specific corrective actions that will address these ECM’s ♦ Operational Changes ♦ Capital Projects ♦ Cost estimate for the recommended ECM’s ♦ Return on investment estimate for each ECM ♦ An engineering design document illustrating an architecture and component system to accomplish manual demand management ♦ Completion of a power study on the effects of the shovels and draglines synchronizing with each other and what it does to the demand of the mine. ♦ Completion of a power study showing RPC inadequacies and trail cable lengths.

Upon completion of this scope of work it was hoped to achieve the following energy savings: ♦ Through low cost and or no cost operational changes it is intended that 603,000 KW demand out of 40.2 MW demand every month, and 232,000 KWH out of 15.5 MWH every month will be conserved. ♦ Through capital funded projects it is intended that 1 MW demand out of 40.2 MW demand every month and 387,000 KWH out of 15.5 MWH every month will be conserved. ♦ Through the assessment process for future expansion, 1% energy conservation due to new technologies and the installation of energy efficient equipment is expected.

Findings and Significant Information:
In comparing some of the differences between a large mine such as NARM, and a smaller mine such as Rawhide, is that the fixed portion of electrical energy usage is 52% of total electrical energy usage at NARM as compared to Rawhide which has a fixed component of only 9%, which in turn creates a higher electrical cost per production unit at Rawhide than at NARM. ♦ First, this translates into the fact that if Rawhide were to increase tonnage, the cost per production unit would decrease significantly. For NARM, if production were to drop off, a substantial increase in cost per production unit would be seen. ♦ Secondly, this indicates that much of the fixed electric energy can be associated with equipment that is constantly running whether systems are loaded or not. So, there must be some operational changes that could take place to relieve this equipment from usage if not being used for production such as, the turning off or slowing down of unused equipment at non productive times. ie… Conveyor belts, pumps, air compressors, crushers, and lighting.

♦ ♦

♦

♦

In the latter case, variable frequency drives (VFD) for conveyor belts pumps, and crushers seem to be a viable option. In this case the option of VFD’s for the 4160v conveyors are very expensive and an engineered scheme of how coal has to flow through gates and chutes at certain speeds could be quite involved that the payback for these devices does not meet normal standards. But, when engineering new conveyor systems with the thought of VFD’s for motor control and the correct design for coal flow can be resolved before construction, the idea has much merit. In fact, NARM has already used this premise to engineer a new plant and control scheme for an additional 20mty coal processing system. And VFD’s have been installed on existing crusher motors to help with times when production tons are low or unexpectedly low. Findings associated with RPC (Reactive Power Compensation) and cable lengths used on shovels, showed minimal impact on demand and usage. The RPC components of 9 shovels would have an impact if total kVAR components were taken into account. Each machine has the ability to inject approximately 6mVARs into the power system. Each machine uses a step method of approximately 850 kVARs to accomplish this. This is very small compared to total kVAR generation throughout the mine such as what the draglines produce at any one time of approximately 9 to 10 mVARS. Throughout the past couple of years, an attempt to repair RPC components immediately on these machines has lessened the affect of kVAR mismanagement on the entire system. Findings associated with the draglines running in synchronization with each other and the affects on the overall demand of the power system has shown that a demand controller could save some power costs. Base load of the mine without the draglines shows to be approximately 15.5mW. As the draglines are in production, the demand raises to an average level of 20mw. When the draglines are in sync with other, which happens many times per day, but only about 9 times on the average per month long enough to cause the demand to rise above 25mW, there would seem to be an ample opportunity to capture this time and make some changes to either the operation of the draglines or the base load to offset the overall demand.

The attached reports on overall mine power usage were compiled by Rockwell Automation PEMS group and explain findings. The other attached facts and figures on Shovels and Draglines were compiled by mine personnel.

Mine Energy Assessment – Supplemental Report

Peabody Energy Company Gillette, Wyoming

Report # DE-FG36-40GO14034 October 31, 2005

For personal assistance regarding your report contact: Steve Nalbandian 6261 Katella Avenue, Suite 1B Cypress, CA 90630 Phone: 714 816-6316 Email: sjnalbandian@ra.rockwell.com

Visit us at: http://www.ab.com/PEMS/ Systems/Products/Communications/Applications

Supplemental Report
Mine Energy Assessment Table of Contents

Page 6

INTRODUCTION NORTH ANTELOPE ROCHELLE ENERGY ANALYSIS
Statistics Load Modeling Pit Model Overburden Coal Operation in the Pits East Plant Model Hopper Feed and Crusher Coal Conveyance Model – Technical Approach Analysis E-21 60” Hopper Reclaim E-43 48” Silo Feed E-343 60” Silo Feed E-102 Slot Feed Slot Reclaim Slot Storage and Reclaim Silos Transfer Building and Auxiliaries Complete East Plant Model West Plant Model Old Hopper Feed and Crusher OLC Hopper Feed and Crusher Coal Conveyance Model W-680 OLC Belt W-801 Old Silo Feed Belt Silos and Trippers Auxiliaries Complete West Plant Model East and West Support Facilities HVAC Loads Natural Gas Usage Lighting Miscellaneous Loads Complete Mine Model Analysis by Area and Department

8 9
9 11 11 11 12 12 13 14 14 15 16 17 18 19 20 20 20 21 23 23 24 25 25 26 26 26 27 29 29 29 30 30 30 32

Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

Plant-Wide Energy Assessment Rockwell Automation Power & Energy Management Solutions

DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2

Supplemental Report
Mine Energy Assessment DISCUSSION
Major Belt Motors and Operating Practices No-Load Operating Practices Power Factor Correction Variable Frequency Drives for Major Belts Belt Power Requirements Variable Frequency Drives for Deep Water Wells Compressed Air Lighting The Bottom Line on Lighting Electric Demand Control

Page Table of Contents 7 34
34 34 34 34 35 35 36 36 37 37

APPENDIX A – MONTHLY DATA FOR STATISTICAL ANALYSIS

38

Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

Plant-Wide Energy Assessment Rockwell Automation Power & Energy Management Solutions

DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2

Supplemental Report
Plant-Wide Energy Assessment
Introduction

Page NAR Energy Analysis 8

This report includes a comprehensive analysis of energy requirements and usage at the North Antelope Rochelle (NAR) mine. Electricity usage information from an existing energy metering/accounting system was available to augment, validate and support traditional analysis of electric/gas bills, production data, weather data and an equipment rating survey. This allowed a complete top-down and bottom-up analysis as described in the next section. Models used to understand process energy requirements were validated using NAR data. This report includes those models. Benefits of this report include: • A heightened awareness and understanding of how and where energy is used in the mining process. This should lead to additional insight and ideas for work practice changes and process design changes that will significantly reduce cost. Specific information on energy usage by department that demonstrates the value of continuing to use and develop the existing energy accounting system, including more reports and regular review of data. Eventually, targets should be set and report-by-exception used to manage energy and drive cost out of the process. A mathematical model that can be used to study the impact of proposed changes to the process and extended to other mines Better understanding of slot-storage energy costs per ton of coal Specific recommendations related to major belt drives, lighting, demand management and other aspects of energy usage at the mine Guidance to be considered as NAR evolves and expands, from simple lighting change-out to alternative major belt drive designs

•

• • • •

Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

Plant-Wide Energy Assessment Rockwell Automation Power & Energy Management Solutions

DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2

Supplemental Report
Plant-Wide Energy Assessment
North Antelope Rochelle Energy Analysis

Page NAR Energy Analysis 9

The purpose of this section is to understand energy usage for present operations. This understanding form the basis for identifying and evaluating changes intended to improve energy performance (lower energy cost per ton of coal produced). There are two (2) approaches to energy analysis; top-down and bottom-up. 1. 2. Top-Down or Statistical Analysis – regression analysis of usage as a function of production and weather data Bottom-up or Load Modeling – estimating usage based on equipment configuration, ratings and operating procedures

Energy usage is best understood by approaching the analysis from both directions and then reconciling the differences with actual recorded data. The resulting understanding and system model are very useful in predicting the impact of proposed changes. This section of the report contains the statistical analysis and model development for North Antelope Rochelle Mine. It also includes the reconciliation based on actual data recorded in an RSEnergyMetrix database. An appendix includes a lot of the detailed supporting information.

Statistics
The period of time used for this analysis is January 1, 2003 through July 30, 2005. The following data were required and available over this time period: • • • Coal production [tons] Electricity usage [kWh] Outdoor temperature [heating degree-days (HDD) and cooling degree days(CDD)]

Actual monthly data used in the analysis are given in Appendix – A. The regression analysis involves finding a best-fit straight line for electric energy usage (kWh) as a function of coal production and weather. The result was as follows: Energy [kWh] = 7,100,000 + 910 x production [1000 tons] + 650 x heating [HDD] This expression can be used to calculate historical electric energy usage at NAR, given production and weather data. It indicates a fixed component of 7.1 million kWh each month, independent of production level or weather. Further, it indicates that 910 kWh are added for each 1000 tons of coal produced, and 650 kWh for each heating degree day. Cooling degree days have no significant impact. The following table shows how accurate the expression is in calculating historical usage: Line Ref. # 1 2 3 4 5 6 7 8 9 10 11 12
Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

Error [+/%] 0 1 2 3 4 5 6 7 8 9 10 Total

Number of Months 5 5 7 4 4 1 4 0 0 0 1 31

Cumulative Number of Months 5 10 17 21 25 26 30 30 30 30 31

Percentage 16% 16% 23% 13% 13% 3% 13% 0% 0% 0% 3%

Cumulative Percentage 16% 32% 55% 68% 81% 84% 97% 97% 97% 97% 100%
DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2

Plant-Wide Energy Assessment Rockwell Automation Power & Energy Management Solutions

Supplemental Report
Plant-Wide Energy Assessment NAR Energy Analysis

Page 10

There are a total of 31 months in the time period studied. The error table indicates the following: • • • • Line #1 – In 5 of the 31 months studied (16% of the sample), the expression correctly predicts energy usage with a very small error (a few tenths of a %) Line #2 – In another 5 of the 31 months studied (16% of the sample), the expression predicts actual energy usage within +/- 1%. Including line #1 and line #2, the expression predicts actual usage within +/- 1% 32% of the time. The expression predicts actual energy usage within +/-6% error in 30 of the 31 samples (97%) Line #11 indicates there is one statistical outlier which happens to be November 2004. In this month, the expression has an error of 10%

Annual results are as follows: Year 2003 2004 2005 (Jan - July) Actual Energy 160,815 MWh 168,756 94,496 Predicted Energy 163,009 MWh 164,437 95,945 Error -2,194 MWh 4,319 -1,449 Error % -1% 3% -2%

As expected, the expression becomes more accurate as the period of time is extended. When applied to November, 2004 the expression had an error of 10%. However, the error is reduced to 3% for the entire 2004 calendar year. By definition, the average error over the entire study period (31 months) is zero. This is a fundamental characteristic of regression analysis. If applied to individual days, the errors would be greater. However, the results are very useful in understanding energy usage and the impact of weather and production. The following are important observations: 1. The fixed portion (7,100 MWh per month) is 52% of total usage in a typical year. Energy usage in a mining operation is usually a stronger function of production. In other words, the fixed usage is relatively high. There are surely opportunities to reduce usage by looking for production equipment running unnecessarily and thus becoming part of the fixed load. The high fixed usage also implies that the cost of energy per unit of production will increase at lower production. The fixed usage must be allocated to each unit of production, so lower production will mean significantly higher energy cost per unit of production. High ambient temperature does not impact usage significantly. This northern location of this mine, at high altitude is not expected to have a significant cooling load.

2.

3.

Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

Plant-Wide Energy Assessment Rockwell Automation Power & Energy Management Solutions

DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2

Supplemental Report
Plant-Wide Energy Assessment NAR Energy Analysis

Page 11

Mine Energy Model
weather 3%

production 45%

fixed 52%

Additional information and all the source data are given in Appendix – A.

Load Modeling
Total usage is the sum of each individual electric load in the mine. The purpose of this “bottom-up” analysis is to understand usage at different points in the process. The process is broken down into the following for analysis: 1. 2. 3. Pits a. b. Plants a. b. Support a. b. c. d. Overburden Coal East West East Administration East Shop West Administration West Shop

The goal is to develop a model that “explains” the known (metered) energy consumption in each step of the process.

Pit Model
The pit model is based on RSEnergyMetrix data and estimates based on equipment ratings and known operating procedures. Electric energy measurements for overburden and coal activities over a period of time are divided by coal production over the same period of time. Equipment ratings and hours of operation are also used for estimates. Overburden Overburden activity does not directly result in coal delivered to the hopper. However, over a period of several months, the energy used for overburden work is expected to correlate to production. The following equipment is classified for this study as overburden equipment.

Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

Plant-Wide Energy Assessment Rockwell Automation Power & Energy Management Solutions

DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2

Supplemental Report
Plant-Wide Energy Assessment
Unit# 103* 104 105 106 107 108 109 120 154 157 Equipment Description P/H 4100A Shovel P/H 4100 Shovel P/H 4100 Shovel P/H 4100A Shovel P/H 4100A Shovel P/H 4100A Shovel P/H 4100XPB Shovel Bucyrus 2570 Dragline Marion 8200 Dragline Bucyrus 395

Page NAR Energy Analysis
* Note that unit 103 began service in August 2004 and was used to replace unit 104 which was moved to coal service at that time. From June 1, 2004 to May 31, 2005 NAR produced 83,660 ktons of coal. During that period of time, overburden activities used 81.2 GWh of electric energy. That translates to about 971 kWh or $ 30.10 per 1000 tons of coal. The draglines consume about 50% of the overburden energy. Cumulative net energy is used for the analysis in order to account for

12

momentary regeneration by the draglines. Unit# 103 105 106 107 108 109 120 154 157 Equipment Description P/H 4100A Shovel P/H 4100 Shovel P/H 4100A Shovel P/H 4100A Shovel P/H 4100A Shovel P/H 4100XPB Shovel Bucyrus 2570 Dragline Marion 8200 Dragline Bucyrus 395 Total Period Energy* 4,589 MWh 5,258 5,932 5,913 5,894 9,446 22,700 18,000 3,493 81,225 MWh Percent 6% 6 7 7 7 12 28 22 4 100 %

*Energy values in the above table are from June 1, 2004 to May 31, 2005. Coal Operation in the Pits Coal operation energy is required primarily by shovels engaged in coal movement, including the following equipment: Unit# 104* 152 155 156 158 Equipment Description P/H 4100 Shovel P/H 2800 XPA Shovel Bucyrus 290B Shovel P/H 4100A Shovel Bucyrus 295 Shovel * Note that unit 104 was moved to coal service in August 2004 when unit 103 arrived for overburden work.

From June 1, 2004 to May 31, 2005 NAR produced 83,660 ktons of coal. During that period of time, coal activities used 25.2 GWh of electric energy. That translates to about 302 kWh or $ 9.35 per 1000 tons of coal. Unit# 104 152 155 156 158 Equipment Description P/H 4100 Shovel P/H 2800 XPA Shovel Bucyrus 290B Shovel P/H 4100A Shovel Bucyrus 295 Shovel Total Period Energy* 5,576 MWh 6,566 3,045 7,113 2,940 25,240 MWh Percent 22 % 26 12 28 12 100 %

*Energy values in the above table are from June 1, 2004 to May 31, 2005.

East Plant Model
Elements of the East Plant model are: 1. 2. 3. 4. 5. Hopper feed and crusher Reclaim belt (E-21) Transfer building Slot Storage Silo feed (E-43 and E-343) 6. 7. Silos Auxiliaries

Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

Plant-Wide Energy Assessment Rockwell Automation Power & Energy Management Solutions

DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2

Supplemental Report
Plant-Wide Energy Assessment Rawhide Energy Analysis

Page 13

Hopper Feed and Crusher The connected motor load is 1375 hp. This includes 1200 hp for the crusher and 175 hp for hydraulics, air compressor, wash down, sump, etc. The crusher motors are estimated to run at 72 to 78% of rated load while processing coal at 5000 TPH, and are estimated to draw 15% of rated load when no coal is being processed. Auxiliary motors are assumed to draw 72% of rated load independent of production. Based on measurements at the West Plant, these estimates may be a little high. However, based on RSEnergyMetrix data and field measurements, average motor load in the East Plant runs about 70% of rating. With a small addition to account for lighting and miscellaneous loads, the hopper feed and crusher load at 5000 TPH is 820 kW and 212 kW when idle (spinning with no coal throughput.) The following graphs are based on this model and $ 0.031 / kWh average cost of electricity.

East Plant Hopper and Crushers
$30.00 Electricity Cost $25.00 $20.00 $15.00 $10.00 $5.00 $0.00 $ / hour $ / 1000 tons

This model for the hopper and crusher will help form an overall model for the East Plant. The next set of important components to be modeled is the major belts.

Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

0 50 0 10 00 15 00 20 00 25 00 30 00 35 00 40 00 45 00 50 00
Production Rate [TPH]
Plant-Wide Energy Assessment Rockwell Automation Power & Energy Management Solutions DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2

Supplemental Report
Plant-Wide Energy Assessment Rawhide Energy Analysis

Page 14

Coal Conveyance Model – Technical Approach The purpose of this section is to understand the energy and power requirements associated with coal conveyors. Major belts in the East Plant are included in the analysis. Conveyor power has three (3) components: 1. 2. 3. no-load conveyor friction power: needed to overcome belt and roller friction whether or not there is coal on the belt load friction power: needed to overcome additional friction caused by the weight of coal on the belt lift: needed to lift the coal to a higher elevation

Total Power = no-load friction + load friction + lift Each of the major belts were analyzed to determine power requirements for the above components. Field measurements were used from belt E-21 to check the analysis and also to determine the coefficient of friction. Analysis The following information is given for each major belt. Number E-21 E-43 E-343 E-102 E-112 E-113/4 Description 60” Hopper Reclaim 48” Silo Feed 60” Silo Feed Slot Feed Slot Reclaim Steep Angle Capacity [TPH] 5300 3200 5300 4000 3000 3200 Length [ft] 2200 2500 2500 650 425 250 Lift [ft] 31 183 183 80 0 80 Speed [fpm] 1228 881 1230 872 872 882

A variety of calculations are then performed with these given numbers. Tons of Coal on the Belt – The total weight of coal on the belt at any point in time is needed to calculate lifting power. This determines how much power is required for lift. The weight of coal, combined with the coefficient of friction, also determines the load friction power. No-load Friction – The belt and rollers have friction that requires power even when the belt is empty. This value was determined by field measurement of motor load with no coal on the belt. Load Friction – As the belt is loaded, additional friction is created and more power is required to overcome it. A coefficient of friction was determined by measuring motor load with the belt loaded. Friction loss (power) is determined by the weight of coal normal to the belt, belt speed and the coefficient of friction. Friction loss (in hp) is equal to the weight normal to the belt (lbs) x belt speed [fps] x coefficient of friction. Lift Power – Lift power is determined by the speed at which the coal is lifted and the weight of the coal. One horsepower is required to lift 550 lbs of coal 1 foot in 1 second. So lift power (in hp) is equal to (lbs. of coal delivered per second) x (lift in feet) / 550. Total Power – Coal conveyors require power to overcome friction and lift the coal if the conveyor delivery end is at a higher elevation than the supply end. Total power is equal to the sum of no-load power, load friction power, and lift power. For each of the major belts, this analysis results in an understanding of belt power components over a range of loads (tons per hour).

Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

Plant-Wide Energy Assessment Rockwell Automation Power & Energy Management Solutions

DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2

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Plant-Wide Energy Assessment Rawhide Energy Analysis

Page 15

E-21 60” Hopper Reclaim This belt is relatively long (2200 feet) and has a small lift (31 feet). The analysis results are as follows.

E-21 60" Hopper Reclaim
600 500

Power [hp]

400 300 200 100 0 0 1000 2000 3000 4000 5000 lift load friction no load friction

Load [TPH]
Motor power of 237 hp is required to move the belt without coal. This no-load friction result is based on actual field measurements and is considered reliable. The power to overcome additional friction caused by the coal load and power required to lift the coal are about equal. The resulting total power at rated load of 5300 TPH is 580 hp. Based on the average cost of electricity and drive/motor efficiency, it costs $2.81 to move 1000 tons of coal across this belt. The cost of running the belt unloaded (no coal) is $6.09 / hour.

Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

Plant-Wide Energy Assessment Rockwell Automation Power & Energy Management Solutions

DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2

Supplemental Report
Plant-Wide Energy Assessment Rawhide Energy Analysis

Page 16

E-43 48” Silo Feed This belt is relatively long (2500 feet) and has a large lift to the top of the silos (183 feet). The analysis results are as follows.

E-43 48" Silo Feed
1,200 1,000

Power [hp]

800 600 400 200 0 0 500 1000 1500 2000 2500 3000 lift load friction no load friction

Load [TPH]
Motor power of 200 hp is required to move the belt without coal. This no-load friction result is based on actual field measurements and is considered quite reliable. The power to overcome additional friction caused by the coal is only about half the power required to lift the coal. The resulting total power at rated load of 3200 TPH is 1087 hp. Based on the average cost of electricity and drive/motor efficiency, it costs $5.27 to move 1000 tons of coal across this belt. The cost of running the belt unloaded (no coal) is $5.14 / hour.

Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

Plant-Wide Energy Assessment Rockwell Automation Power & Energy Management Solutions

DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2

Supplemental Report
Plant-Wide Energy Assessment Rawhide Energy Analysis

Page 17

E-343 60” Silo Feed This belt is relatively long (2500 feet) and has a large lift to the top of the silos (183 feet). The analysis results are as follows.

E-343 60" Silo Feed
1,800 1,600 1,400 1,200 1,000 800 600 400 200 0

Power [hp]

lift load friction no load friction

0

1000 2000 3000 4000 5000

Load [TPH]
Motor power of 236 hp is required to move the belt without coal. This no-load friction result is based on actual field measurements and so regarded as quite reliable. The power to overcome additional friction is only about half what is required to lift the coal. The resulting total power at rated load of 5300 TPH is 1672 hp. Based on the average cost of electricity and drive/motor efficiency, it costs $8.10 to move 1000 tons of coal across this belt. The cost of running the belt unloaded (no coal) is $6.09 / hour.

Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

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DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2

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Plant-Wide Energy Assessment Rawhide Energy Analysis

Page 18

E-102 Slot Feed This is a short belt (650 feet) that uses most of its power requirement to lift the coal to the top of the slot storage facility. The analysis results are as follows.

E-102 Slot Feed
500 450 400 350 300 250 200 150 100 50 0

Power [hp]

lift load friction no load friction

0

1000

2000

3000

4000

Load [TPH]
Motor power of 70 hp is required to move the belt without coal. This no-load friction result is estimated based on measurements of other belts. As expected, the power to lift coal is three (3) times the power required to overcome load friction. The resulting total power at rated load of 4000 TPH is 484 hp. Based on the average cost of electricity and drive/motor efficiency, it costs $3.11 to put 1000 tons of coal in the slot on this belt. There are other electric loads in the slot storage area. See the analysis section on page 17 for complete information on the cost of slot storage. The cost of running this belt unloaded (no coal) is $1.80 / hour.

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Slot Reclaim Slot reclaim includes three (3) belts (E-112, 113 and 114). This analysis is based on the combination of all three (3) belts. The lift is 80 feet on the steep-angle belts. As expected, lift power is a significant component in the total.

Slot Reclaim Total
450 400 350 300 250 200 150 100 50 0

Power [hp]

lift load friction no load friction

0

500 1000 1500 2000 2500 3000

Load [TPH]
Motor power of 100 hp is required to move the belts without coal. The power to lift the coal is more than double the friction load. The resulting total power at rated load of 3000 TPH is 413 hp. Based on the average cost of electricity and drive/motor efficiency, it costs $3.54 to reclaim 1000 tons of coal from the slot. This does not include other significant slot electric loads. See the analysis on page 17 for a complete discussion on slot storage. The cost of running the belts unloaded (no coal) is $2.57 / hour.

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Slot Storage and Reclaim In addition to belt energy moving coal in and out of slot storage, the facility itself has equipment with significant loads (tripper, rotary plows, etc.) In order to model the “round trip” cost of slot storage, this section includes the belt energy and also the additional loads. Consider the cost of running 1000 tons of coal in and out of slot storage. The slot feed belt will run for about 15 minutes and use electricity costing $3.11 The reclaim belts will run for about 20 minutes getting the 1000 tons of coal out of storage and will cost $3.54 Miscellaneous and support equipment (tripper, rotary plows, etc) will also run during this time and cost $ 2.16 Therefore, a round trip through the slot costs $ 8.81 per 1000 tons.

Slot Storage Cost $ 8.81 / 1000 tons

$2.16 $3.11 slot feed slot reclaim tripper, plow

$3.54

Silos The silos have a variety of hydraulic equipment, a shuttle belt and air compressor. The total connected load is about 310 hp, plus miscellaneous lighting and space conditioning (ac and heat in the control room) load. Although some variation in energy usage is expected from when a train is being loaded versus when no trains are being loaded. This model is based on the assumption of constant load. Based on the connected load and average motor utilization in the silos of 78%, the silo load is 220 kW or about $ 6.20 / hour based on the average cost of electricity. Transfer Building and Auxiliaries The final piece to the East Plant model must account for transfer belts and auxiliary equipment including water pumps, wash down and the sampling systems.

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Equipment Sample System 1 Sample System 1 Sample System 1 Sample System 2 Wash down Wash down Wash down Wash down Deep well #1 Deep well #2 Mine #1 water Mine #2 water Potable water #1 Potable water #2 Transfer Shuttle Transfer Shuttle Total Connected Load [hp] 10 30 40 10 40 25 25 25 100 290 100 100 7.5 7.5 125 100 1035 hp

Page Rawhide Energy Analysis 21

This table details the miscellaneous equipment. Duty cycles established from RSEnergyMetrix data indicate this equipment represents an idle load of about 370 kW. Using the average cost of electricity, this is a fixed cost of $11.45 per hour. If the transfer belts are running, the cost increases to $ 15.50. The transfer shuttle belts are not major loads. So, for this model, an average cost is used without attempting to account for idle and production periods separately. This completes the component analysis for the East Plant. It is now possible to construct a complete picture of electricity usage and cost as a function of plant production.

Complete East Plant Model The East Plant model is the sum of the components as follows. Component Hopper feed and crusher Reclaim belt E-21 Transfer and auxiliaries Silo feed E-43 and E-343 Silo Total Fixed Load 212 186 370 171 220 1159 Variable Load 122 51 0 215 0 388

By definition, the fixed load is present whether or not coal is being processed. The variable load coefficient times the load [in 1000 tons per hour] gives the additional electric load directly associated with moving coal. From this table, it is established that average electric load for the East Plant can be estimated by the following expression: Average electric load [kW] = 1,159 + 388 x Production [1000 tons / hour] Based on the average cost of electricity, this translates into the following cost per hour: East plant electric cost [$/hour] = $35.93 + $12.03 x Production [1000 tons / hour]

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East Plant Model
$120 Electricity Cost $100 $80 $60 $40 $20 $0
0 50 0 10 00 15 00 20 00 25 00 30 00 35 00 40 00 45 00 50 00

$ / hour $ / 1000 tons

Production Rate [TPH]
Because of the large fixed component, East Plant energy usage [kWh per 1000 tons] will vary depending on the production rate. An analysis of 2004 production data on a 15-minute basis reveals the following summary statistics. Average (mean) production rate Standard deviation model is derived. This model does not include a trip through slot storage. Recall from the previous analysis (on page 17) that the cost of such a trip is $ 8.81 per 1000 tons. As an example, consider the cost of moving 1000 tons of coal at the rate of 4000 TPH. Itinerary East Plant hopper to silos Round trip through slot storage Hopper through slot to silos Slot excursion premium Cost per 1000 tons $ 21.01 $ 8.81 $ 29.82 42% Production Rate Tons / Hour Average 4020 + 1 Std Deviation 5662 – 1 Std Deviation 2378 Used for Model Energy Usage 676 kWh / 1000 tons 593 875 705 4020 tons per hour 1642 At the average production rate of 4020 TPH, the East Plant uses 676 kWh / 1000 tons. The following table summarizes how the East Plant

From this table, it can be concluded that an excursion through slot storage increases the cost by $ 8.81 per 1000 tons for additional electricity. This represents a 42%increase in electricity cost within the East Plant.

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West Plant Model
Elements of the West Plant model are: Old and OLC hopper feeds and crushers Belt E-680 Belt E-801 Silos, including trippers Auxiliaries Old Hopper Feed and Crusher The connected motor load is 1757 hp. This includes 1600 hp for the crushers and 157 hp for hydraulics, air compressor, wash down, sump, etc. Four (4) 200-hp crusher motors averaged 133 hp each while processing coal at 3200 TPH (field measurement), and are estimated to draw 15% of rated load when no coal is being processed. Auxiliary motors are assumed to draw 72% of rated load independent of production. The following graph is based on this model, assuming all eight (8) motors are equally loaded and $ 0.031 / kWh average cost of electricity. 1. 2. 3. 4. 5.

West Old Hopper and Crushers
$25.00 Electricity Cost $20.00 $15.00 $10.00 $5.00 $0.00 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500
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$ / hour $ / 1000 tons

Production Rate [TPH]

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OLC Hopper Feed and Crusher The connected motor load is 780 hp. This includes 700 hp for the crusher and 80 hp for auxiliaries. Based on field measurements, these crusher motors draw 331 kW while processing coal at 4100 TPH. They are estimated to draw 15% of rated load when no coal is being processed. Auxiliary motors are assumed to draw 72% of rated load independent of production. The following graph is based on this model and $ 0.031 / kWh average cost of electricity.

West OLC Hopper and Crushers
$18.00 $16.00 $14.00 $12.00 $10.00 $8.00 $6.00 $4.00 $2.00 $0.00

Electricity Cost

$ / hour $ / 1000 tons

While crushing loads are based on field measurements, the allocation of auxiliary loads associated with the crushers are estimates. This includes hydraulics, air compressor, wash down, sump, etc. The purpose is to understand hopper/crusher loads as compared to conveyors, silos, etc.

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50 0 10 00 15 00 20 00 25 00 30 00 35 00 40 00 45 00 50 00
Production Rate [TPH]
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0

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Coal Conveyance Model The following information is given for each major belt. Number E-680 E-801 Description Overland Coal (OLC) Old Silo Feed Capacity [TPH] Length [ft] Lift [ft] Speed [fpm]

5500 4000

5250 1300

310 323

1230 872

W-680 OLC Belt This is the longest belt at the mine (5250 feet) and has a large lift to the top of the silos (310 feet). The high lift power is evident in the graph below. The analysis results are as follows.

680 OLC
3,000 2,500

Power [hp]

2,000 1,500 1,000 500 0 0 1000 2000 3000 4000 5000 6000 lift load friction no load friction

Load [TPH]
Motor power of about 400 hp is required to move the belt without coal. When loaded with coal, the power to overcome additional friction is only about 25% of what is required to lift the coal. The resulting total power at rated load of 5500 TPH is 2540 hp. Based on the average cost of electricity and drive/motor efficiency, it costs $11.87 to move 1000 tons of coal across this belt at rated load. The cost of running the belt unloaded (no coal) is $10.28 / hour.

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W-801 Old Silo Feed Belt This is a relatively short belt (1300 feet) but it has the highest lift at the mine (323 feet). The high lift power as compared to friction power is evident in the graph below. The analysis results are as follows.

West 801
1,800 1,600 1,400 1,200 1,000 800 600 400 200 0

Power [hp]

lift load friction no load friction

0

1000

2000

3000

4000

Load [TPH]
Motor power of about 135 hp is required to move the belt without coal. The power to overcome additional friction is only about 33% of what is required to lift the coal. The resulting total power at rated load of 4000 TPH is 1571 hp. Based on the average cost of electricity and drive/motor efficiency, it costs $10.09 to move 1000 tons of coal across this belt at rated load. The cost of running the belt unloaded (no coal) is $3.47 / hour. Silos and Trippers The silos have hydraulic equipment, tripper belts, etc. The auxiliary connected load is about 320 hp plus 700 hp for the tripper belts. Miscellaneous load includes lighting and space conditioning (ac and heat in the control room). Although some variation in energy usage is expected based on whether or not a train is being loaded. For this model, it is assumed the load is constant. Alternatively, the tripper belt loads could be included in the silo feed belt loads. However, for this model, they are included as part of the silo load. Based on the connected load, and average motor utilization in the silos of 78%, the silo load is 380 kW or about $ 11.78 / hour based on the average cost of electricity. Auxiliaries The final piece to the West Plant model must account for auxiliary equipment including water pumps, wash down and the sampling systems.

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Equipment Connected Load [hp]

Page Rawhide Energy Analysis 27

OLC TD water 25 OLC DH water 25 OLC air comp. 25 Old air compressor 25 OLC samples 30 Old sample 40 OLC sump 40 Water 100 Well 100 Pond 100 Deep well 100 Total 610 hp By definition, the fixed load is present whether or not coal is being processed. The variable load coefficient times the load [in 1000 tons per hour] gives the additional electric load directly associated with moving coal. From this table, it is established that average electric load for the West Plant can be estimated by the following expression:

This table details the miscellaneous equipment. Duty cycles established from RSEnergyMetrix data indicate this equipment represents a load of about 220 kW. Using the average cost of electricity, this is a fixed cost of $6.82 per hour. This completes the component analysis for the West Plant. It is now possible to construct a complete picture of electricity usage and cost as a function of plant production.

Complete West Plant Model The West Plant model is the sum of the components as follows. Component Hopper feed and crushers OLC W-680 W-801 Silo Auxiliaries Total Fixed Load 160 314 106 380 220 1180 Variable Load 80 306 282 0 0 668

Average electric load [kW] = 1,180 + 668 x Production [1000 tons / hour] Based on the average cost of electricity, this translates into the following cost per hour: East plant electric cost [$/hour] = $36.58 + $20.71 x Production [1000 tons / hour

West Plant Model
$160 $140 $120 $100 $80 $60 $40 $20 $0

Electricity Cost

$ / hour $ / 1000 tons

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0 50 0 10 00 15 00 20 00 25 00 30 00 35 00 40 00 45 00 50 00
Production Rate [TPH]
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Similar to the East Plant, the West Plant energy usage [kWh per 1000 tons] will vary depending on the production rate. An analysis of 2004 production data on a 15-minute basis reveals the following summary statistics. Average (mean) production rate Standard deviation model is derived. It is more expensive to process coal through the West Plant compared to the East Plant. While the fixed cost is essentially the same, the variable cost is much higher in the west. This is due primarily to the length of the OLC belt and higher lifts. Production Rate Tons / Hour Average 5350 + 1 Std Deviation 7565 – 1 Std Deviation 3135 Used for Model Energy Usage 889 kWh / 1000 tons 824 1044 910 kWh / 1000 tons 5350 tons per hour 2215 At the average production rate of 5350 TPH, the West Plant uses 889 kWh / 1000 tons. The following table summarizes how the West Plant

The West Plant also operates more often at less than rated capacity, because of the fixed energy component; this causes the usage per unit of production to be higher.

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East and West Support Facilities
There are a number of facilities such as shop, maintenance and administration buildings that support the mining operation. They require energy for lighting, heating, cooling and miscellaneous loads such as small tools and computers. Clearly, these loads are not correlated directly to coal production. They are mostly fixed loads. However, the heating and cooling portion is expected to correlate to outside weather conditions. HVAC Loads The following table summarizes the HVAC energy analysis based on building size, type of construction and uses. Energy for heat is primarily provided by natural gas, and cooling is an electric load. One exception is the building that houses the fire truck which has electric heat. Floor Area [sq ft] 10,000 14,400 55,300 6,900 9,600 11,200 22,500 2,500 2,400 7,200 10,000 24,600 32,000 Design Load Heating Cooling [kBtu/hr/F] [tons/F] 7.5 10.8 207.4 7.8 10.8 10.9 16.9 3.8 2.9 8.1 16.5 92.3 144.0 0.50 0.72 2.77 0.35 0.48 0.56 1.13 0.13 0.12 0.36 0.50 1.23 1.60 Annual Energy Heating Cooling [MBtu] [kWh] 1,260 1,814 34,839 1,304 1,814 1,835 2,835 630 484 1,361 2,772 15,498 24,192 90,638 10,080 14,515 1,739 11,290 22,680 2,419 1,814 1,008 3,720 323 69,588

Building Description Business Unit RC Admin / Miners Changing East Truck Shop East M&E North Shop NA Administration West Change House Fire Truck First Aid West M&E Central Warehouse West Shop Caterpillar Shop Total

The Fire Truck building has electric heat, so the total annual electric usage is the entire cooling load plus the Fire Truck building heat load. (70,218 kWh per year) Information is also available from RSEnergyMetrix to help model the total facility load.

Natural Gas Usage Most of this report is focused on electric energy. However, here is an opportunity to examine natural gas usage. Gas is used for space heating and hot water. Based on recent billing, the mine uses about 94,600 3 MCF each year. Using an average heating value of 1025 Btu / ft , and 92% boiler efficiency, that represents 89,200 MBtu per year. Based on the HVAC model, facilities require 90,638 MBtu for heat. This is a satisfactory reconciliation of actual gas usage and calculated facilities heating load. Based on an average cost per MCF of $4.00, the following table gives estimated heating cost by facility.

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Annual Heating Energy Energy Cost [MBtu] 1,260 1,814 34,839 1,304 1,814 1,835 2,835 630 484 1,361 2,772 15,498 24,192 90,638 $5,040 $7,256 $139,356 $5,216 $7,256 $7,340 $11,340 $2,520 $1,936 $5,444 $11,088 $61,992 $96,768 $362,552

Page 30

Building Description Business Unit RC Admin / Miners Changing East Truck Shop East M&E North Shop NA Administration West Change House Fire Truck First Aid West M&E Central Warehouse West Shop Caterpillar Shop Total

Floor Area [sq ft] 10,000 14,400 55,300 6,900 9,600 11,200 22,500 2,500 2,400 7,200 10,000 24,600 32,000

Lighting Lighting data is repeated here from the original survey done at various support facilities. The estimated lighting load will be subtracted from total facility load along with HVAC energy to provide an estimate of the miscellaneous loads. Building Description Business Unit RC Admin / Miners Changing East Truck Shop East M&E North Shop NA Administration West Change House Fire Truck First Aid West M&E Central Warehouse West Shop Caterpillar Shop Total Lighting Power [kW] 12.5 18 84.5 7.4 8.3 14 28 3.2 2.9 13.3 16.6 69.5 36.8 315 kW

Miscellaneous Loads Miscellaneous loads such as tools and computers can be estimated from RSEnergyMetrix data, the model, and other considerations. Now all the components are available to assemble the complete mine model.

Complete Mine Model
All of the model components are now assembled into the complete model as follows.

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Component Overburden Coal – Pit East Plant West Plant Administration

Page Rawhide Energy Analysis
Usage [kWh / 1000 tons] 971 302 705 950 54

31

The final step is to use production, weather and total mine usage data to check the bottom-up model. For reference, the top-down model results are also given in the following table. Coal Production Year 2003 2004 2005* East 35,308 35,370 20,189 West 45,144 46,860 19,919 Total 80,452 82,230 40,108 Weather Heating Cooling [HDD] [CDD} 7074 750 6781 385 4197 390

* The present year of 2005 is a partial year with results through July 31, 2005. Comparison of Top-Down and Bottom-Up Results Year 2003 2004 2005 Actual [MWh] 160,815 168,757 94,496 Bottom-up Model Result Error 174,540 9% 178,570 6% 86,380 -9% Top-down Model Result Error 163,010 1% 164,436 -3 % 95,945 2%

Having modeled energy usage from the top-down (statistical) and from the bottom-up (load modeling), agreement this close indicates the models are sufficient for use as energy conservation measure (ECM) evaluation. The following is a graphical representation of overall mine energy usage in a typical year with total production of 82,000,000 tons of coal, 58% processed by the West Plant, and 42% processed by the East Plant. No slot storage activity is included. The first figure indicates the percentage of electric energy used in each department. The second figure gives electricity cost for each department per 1000 tons of coal produced.

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Electric Energy [MWh]

West Plant, 24.5%

Administration, 2.5% Overburden, 45.1%

East Plant, 13.8%

Coal, 14.0%

Electric Energy [$ / 1000 tons]]

West Plant, $15.54

Administration, $1.59 Overburden, $28.60

East Plant, $8.72

Coal, $8.89

Analysis by Area and Department
For a typical year, real and reactive electric energy can be allocated to departments based on the model and using RSEnergyMetrix data for validation as follows.

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Area Department

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Average Power Factor 98% 87% (lead) 95% 84% 82% 88% 85%

33

Main Electric Supply Pits Plants Overburden Coal East West OLC Admin and Shops

Real Energy [MWh] % 167,550 100 % 75,640 23,530 23,070 15,210 25,900 4,200 45 % 14 % 14 % 9% 15 % 3%

Support

Remember that the estimates can have several percentage point errors based on the model and available data for validation.

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Discussion

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There are a number of topics for which additional information was requested. This section provides that additional information and discussion on the topics assigned to this supplemental report.

Major Belt Motors and Operating Practices
The energy model quantifies requirements associated with fixed friction, load friction and (coal) lift. Belt performance is an integral part of mine operations. Any proposed energy-saving action must not compromise belt performance. Three (3) areas are considered for belt energy savings; no-load operating practices, power factor correction, and control under load conditions. The first refers to times when the belt is presently operated with no coal on the belt, such as during shift changes. The second is aimed at correcting power factor at each motor as currently installed. The third is where drives are often mentioned as a possibility. First, consider no-load operating practices. No-Load Operating Practices There are significant amounts of time when the belts are running but not transporting coal. There are also operating constraints that may prohibit belt shutdown during some periods of time. There do appear to be times, such as during shift changes, when the belts could be shut down. The energy model and the original study report quantify the expected savings. Changes in work practices to include staggering operations are recommended as a means of reducing empty belt time and energy expense. Power Factor Correction These large motors require reactive power. The overall mine power factor as seen from the utility meter is near unity. So reactive power requirements are presently supplied elsewhere in the mine by capacitor banks or controlled synchronous loads. Correcting the power factor at the motor load will not reduce the price paid for electricity because the reactive power comes from within the mine; there is no power factor penalty. The only savings would be associated with reduced distribution losses. A small amount of real energy is required to get the reactive power from the source to the motor load. There is an opportunity to add power factor correction capacitor banks at each of the existing motors. This option would correct poor power factor caused by induction motors. However, the savings earned by this option would be minimal. Variable Frequency Drives for Major Belts Major belts are run continuously at constant supply frequency (no drives). There would appear to be an opportunity for energy savings associated with motor speed control (variable frequency drives). This section makes use of actual belt load measurements and motor drive performance data to examine the installation of drives. Rated Load [tons/hr] 5,300 3,200 5,300 4,000 5,500 Horsepower @ average @ no load load 500 237 801 200 1374 236 1653 400 894 135

Belt E-21 E-43 E-343 W-680 W-801

@ rated load 580 1087 1672 2540 1571

Connected 1250 2 x 450 2 x 1250 3 x 900 2 x 1500

The load model and field measurements indicate that several of the major belt drive motors are typically under-loaded. However, this is a conveyor application where variable speed is likely to interfere with performance. For example, these belts move coal, and running them at 50% speed to save energy is just not practical The brake horsepower delivered to the conveyor drive shaft is a function of rotational speed and torque. There is presently a mismatch between the conveyor requirements and the motor capability. Conveyor Requirements – The conveyor power requirement is a function of lift, coal load and friction. Since lift and coal load cannot be changed, the opportunity for reduced requirement is friction. The model quantifies the friction load and allows for estimates of potential savings from low-friction bearings, etc.
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Motor Capability – Each motor has a speed-torque characteristic and efficiency associated with various operating points. As the motor is unloaded, the power factor and efficiency decrease. Power factor decreases because reactive current requirements decrease by a small amount while real current is proportional to mechanical load and decreases significantly. The application of drives or other motor changes will not impact brake horsepower requirements at a given delivery [TPH]. The only savings would result from the motor being able to supply the conveyor requirement more efficiently. In theory, a transmission between the motor and conveyor could be used to allow the motor to run at reduced speed while maintaining belt speed. While technically feasible, this is not considered a viable option. The cost could rival that of replacing the motor. There are also benefits to the larger motors. The extra power could be needed from time to time under extreme conditions to get the belt moving, or when one of several motors is out of service. Therefore, savings associated with changes to the motor/drive assets must come from increased motor efficiency and/or reduced reactive power requirements (power factor closer to unity.) The available savings is relatively small. Another consideration is the possibility of reducing the number of motors in operation. In some cases, there are several motors and the belt requirements could be met without all motors in operation. A detailed analysis would be required over a period of time to verify belt requirements and the practicality of this option. Belt Power Requirements One challenge in sizing major belt motors is the trade off between operating efficiency and the occasional need for extra power. Factors such as static friction, load momentum (accelerating coal), icing, etc. can require extraordinary torque and power. Unfortunately, that extra motor capacity then remains on-line for the vast majority of the time when operations are normal. In future designs, consideration should be given to this issue. Other methods of providing temporary, extra torque/power should be considered.

Variable Frequency Drives for Deep Water Wells
There are number of large motors at the mine that operate well pumps or otherwise move water as follows. An additional deep well was being installed at the time of this report. Factors that affect the efficiency of pumping Connected include matching the pump and motor Load [hp] characteristics (speed – torque). This allows both Deep well #1 East 100 pieces of equipment to operate in their most Deep well #2 East 290 efficient range. Impellor selection/trim is Mine #1 water East 100 important. Unless the flow rate and/or hydraulic head are Mine #2 water East 100 significantly different than anticipated during the Potable water #1 East 7.5 design process, the motor-pump match is probably Potable water #2 East 7.5 correct. Water West 100 Other factors that impact efficiency include pump Well West 100 maintenance, specifically impeller condition, and Pond West 100 water distribution piping and valves. A partiallyDeep well West 100 closed value in the distribution network being used to throttle water flow is a source of inefficiency. It is better to slow the pump with a variable-speed drive than to operate at full speed and throttle the flow (essentially increase the head) with partially-closed valves. Description Serving Variable speed control comes with a price, and it is unlikely the investment could be justified for these pumps. Any significant mismatch between pump and motor should first be addressed by considering impeller trim or changing the motor.

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Page 36

Compressed Air
Obvious measures to be taken include a leak repair program and a periodic review of work practices and the necessity to use compressed air as an energy supply. The cost and magnitude of leakage is commonly underestimated. It is interesting to evaluate compressed air usage during idle times to quantify the leakage problem. Compressed air is a very expensive energy source. Less than 10% of the electric energy used to drive the air compressor actually arrives at the end-use device and does useful work. A variety of alternatives are available and often cost effective. This includes the use of small electric motors and air amplifiers (venture devices) for blow-off. Air compressors, like water pumps, have a speed-torque characteristic. Efficiency is lost as load is reduced. Given a certain air requirement, it is desirable to have all compressors operating in an efficient range. More specifically, all air compressors should be operated at the same incremental cost of air. In other words, the cost (in additional kW) to output one additional increment of air flow (scfm) should be equal for all machines on-line. Centrifugal and screw compressors will have different operating characteristics. This economic dispatch algorithm is typically used for industrial air supplies with four (4) or more large (>1000 cfm) compressors. Usually, the large centrifugal units are base-loaded and one or more screw units modulate pressure. The usefulness of economic dispatch at NAR is limited (probably not cost-effective). The air requirements are modest and dispersed around the mine. After the obvious leak program and use review, the recommendation is to evaluate each significant compressor to be sure it is operating in an efficient range. As a benchmark, Industrial compressed air supplies should average over 4 scfm delivered per drive motor horsepower.

Lighting
The model estimates total annual lighting cost of about $70,000. Knowing that number helps put potential savings estimates in perspective. Savings would result from more diligent lighting control (turned off when not needed) and upgrading to high-efficiency lighting. For the purpose of estimating savings, it is not correct to use the average cost of electric energy ($ 0.031 kWh) because changes may not reduce demand. In particular, lighting control usually does not impact demand. So estimates must use only the energy charge component ($ 0.019 / kWh) for savings calculations. Lights in the West Shop, East Shop, North Shop, Caterpillar Shop and Slot Storage burn all the time and represent about 575,000 kWh per year of potential energy savings. The annual savings associated with this control is about $ 11,000. High efficiency lighting should also be considered. The following table summarizes the potential savings. The savings are based on the assumption that lighting control is implemented. In other words, there is no double counting of savings that results when the analyst fails to consider that a high-efficiency lamp uses no less energy than a low-efficiency lamp when turned off. Existing Fixtures 1000-Watt 400-Watt Totals Replacement 468-Watt 242-Watt Number of Fixtures 208 170 Energy Savings 827 MWh 222 MWh Value of Savings $ 15,700 $ 4,200 $ 19,900 Installed Cost $ 92,000 $ 58,250 $ 150,250

The above figures are based on a ballast factor of 1.15, energy cost of $0.019 per kWh and estimated 6500 hours of operation per year. Installed cost is based on $400 per fixture ($300 for the smaller ones) plus 32 minutes of installation time with a crew-hour priced at $ 80.00. However, the above costs are driven primarily by the cost of the fixtures (they represent about 90% of the cost.) Also, consideration should be given to adjusting the number of fixtures to meet specific illumination requirements. It may be possible to eliminate some fixtures entirely.
Powder River Coal Company Gillette, Wyoming A Peabody Energy Company Plant-Wide Energy Assessment Rockwell Automation Power & Energy Management Solutions DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2

Supplemental Report
Plant-Wide Energy Assessment Discussion

Page 37

The Bottom Line on Lighting Peabody Energy could invest about $150,000 in lighting upgrades to save an estimated $20,000 per year. The simple payback is 7.5 years. The decision whether or not to make this investment should be based on the cost of capital and other investment opportunities. Even without additional information or analysis, this does not appear to be a very attractive investment. However, consideration should be given to a change-out program that is implemented as fixtures and lamps require maintenance or replacements.

Electric Demand Control
Electricity prices have two (2) major components; energy and demand. Most of the analysis is based on the average cost of $0.031 per kWh. Inherent is the assumption that all loads contribute equally to the overall demand, and therefore, demand will be reduced proportional to energy. In the case of lighting control, only the energy component ($ 0.019 per kWh) was used. It is known that demand will not be significantly affected by lighting control. Using the lower cost figure yields a conservative estimate.

The mine load factor averages 75%. It ranges from 66% to 84% in any given month. The following table summarizes the estimated contribution of each department to overall billing demand. Area Department Peak Demand [kW] % 24,500 100 15,000 4,400 2,300 2,500 300 61 18 10 10 1

Main Electric Supply Pits Plants Support Overburden Coal East West / OLC Administration

It would appear that opportunities for demand management are presented by the draglines and shovels. It is estimated that pit operations account for 79% of the billing demand. However, nine (9) shovels offer significant diversity just due to random variations in operation. It is unlikely that demand management would make a significant difference in shovel contribution to billing demand. Two (2) draglines do not have the same statistical advantage. In other words, random variation between two (2) draglines does not yield much demand reduction from diversity. So coordinated dragline control might be worth consideration. The original draft of this report questioned the practicality of such control. This was based on a concern for maintaining smooth operations. However, electrical engineers from Peabody Energy report success with similar control at Kayenta/Black Mesa. So there is direct evidence that demand control can be acceptable to operations and result in significant savings. Billing demand is determined by the highest interval usage for the billing period. Draglines could be coordinated for 29 days of the month and then negate all savings with one uncoordinated interval if it occurs during peak demand at the mine. So the demand controller must be properly designed and implemented. Peabody Energy has reported success at another mine and this analysis does not uncover any technical reason why the result would not transfer to NAR as well.

Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

Plant-Wide Energy Assessment Rockwell Automation Power & Energy Management Solutions

DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2

Supplemental Report
Plant-Wide Energy Assessment
Appendix A – Monthly Data for Statistical Analysis

Page Discussion 38

Production [1000 tons] Energy [kWh] 14,280,000 12,411,000 12,348,000 12,957,000 13,251,000 12,978,000 13,629,000 13,398,000 13,524,000 13,899,305 13,566,000 14,574,000 160,815,305 14,952,000 13,377,000 13,209,000 13,608,000 13,881,000 13,986,000 14,238,000 14,357,712 13,832,000 14,224,000 14,756,000 14,336,000 168,756,712 14,336,000 13,552,000 14,588,000 13,104,000 13,188,000 12,376,000 13,352,260 94,496,260 East 2896 2601 2422 2840 3071 3109 3136 3254 3079 3032 2798 3070 35,308 2845 2727 2898 3073 2681 2990 3106 3150 3143 2931 2879 2947 35,370 2827 2893 3103 3035 2813 2644 2874 20,189 West 3724 3266 3513 3541 3990 3575 3829 3646 3834 3971 3939 4316 45,144 4224 3637 3791 2799 4103 3962 4165 4369 4238 4341 3310 3921 46,860 Total 6620 5867 5935 6381 7061 6684 6965 6900 6913 7003 6737 7386 80,452 7069 6364 6689 5872 6784 6952 7271 7519 7381 7272 6189 6868 82,230 2827 2893 7626 7089 6060 6003 7610 40,108

Degree Days Heating 1108 1187 993 493 403 185 0 17 275 440 872 1101 7,074 1233 1007 746 560 362 155 23 70 210 506 866 1043 6,781 1221 919 846 600 448 151 12 4,197 Cooling 0 0 0 0 19 30 307 351 38 5 0 0 750 0 0 0 0 3 40 205 91 46 0 0 0 385 0 0 0 0 1 105 284 390

January February March April May June July August September October November December Total 2003 January February March April May June July August September October November December Total 2004 January February March April May June July Total 2005

4523 4054 3247 3359 4736 19,919

Weather data was taken from a National Weather Service weather station at the Gillette Campbell County Airport (GCC) in Gillette, Wyoming.

Month

Energy [kWh] Actual Predicted

Error [kWh] [%]

Production Total

Degree Days Heating

Supplemental Report
Plant-Wide Energy Assessment
January February March April May June July August September October November December Total 2003 January February March April May June July August September October November December Total 2004 January February March April May June July Total 2005 14,280,000 12,411,000 12,348,000 12,957,000 13,251,000 12,978,000 13,629,000 13,398,000 13,524,000 13,899,305 13,566,000 14,574,000 160,815,305 14,952,000 13,377,000 13,209,000 13,608,000 13,881,000 13,986,000 14,238,000 14,357,712 13,832,000 14,224,000 14,756,000 14,336,000 168,756,712 14,336,000 13,552,000 14,588,000 13,104,000 13,188,000 12,376,000 13,352,260 94,496,260 13,844,400 13,210,520 13,146,300 13,227,160 13,787,460 13,302,690 13,438,150 13,390,050 13,569,580 13,758,730 13,797,470 14,536,910 163,009,420 14,334,240 13,545,790 13,671,890 12,807,520 13,508,740 13,527,070 13,731,560 13,987,790 13,953,210 14,046,420 13,294,890 14,027,830 164,436,950 14,326,440 13,488,590 14,589,560 13,940,990 12,905,800 12,660,880 14,032,900 95,945,160

Page Discussion
435,600 -799,520 -798,300 -270,160 -536,460 -324,690 190,850 7,950 -45,580 140,575 -231,470 37,090 -2,194,115 617,760 -168,790 -462,890 800,480 372,260 458,930 506,440 369,922 -121,210 177,580 1,461,110 308,170 4,319,762 9,560 63,410 -1,560 -836,990 282,200 -284,880 -680,640 -1,448,900 3% -6% -6% -2% -4% -3% 1% 0% 0% 1% -2% 0% -1% 4% -1% -4% 6% 3% 3% 4% 3% -1% 1% 10% 2% 3% 0% 0% 0% -6% 2% -2% -5% -2% 6620 5867 5935 6381 7061 6684 6965 6900 6913 7003 6737 7386 80,452 7069 6364 6689 5872 6784 6952 7271 7519 7381 7272 6189 6868 82,230 7069 6364 7626 7089 6060 6003 7610 40,108

39
1108 1187 993 493 403 185 0 17 275 440 872 1101 7,074 1233 1007 746 560 362 155 23 70 210 506 866 1043 6,781 1221 919 846 600 448 151 12 4,197

Mine Energy Assessment –

Supplemental Report
Plant-Wide Energy Assessment Discussion

Page 40

Rawhide Report

Peabody Energy Company Gillette, Wyoming

Report # DE-FG36-40GO14034 March 13, 2006

For personal assistance regarding your report contact: Steve Nalbandian 6261 Katella Avenue, Suite 1B Cypress, CA 90630 Phone: 714 816-6316 Email: sjnalbandian@ra.rockwell.com

Visit us at: http://www.ab.com/PEMS/ Systems/Products/Communications/Applications

Rawhide Mine
Energy Assessment Table of Contents

Page 41

Table of Contents

INTRODUCTION........................................................................................................... 43
Comparison ................................................................................................................................................................44

BACKGROUND ............................................................................................................ 46
Facility Overview.......................................................................................................................................................46 General Layout .......................................................................................................................................................47 Lighting...................................................................................................................................................................48 Electric Distribution................................................................................................................................................48 Mining Process Equipment.......................................................................................................................................49 Pits ..........................................................................................................................................................................49 Plant ........................................................................................................................................................................50 Electricity ...................................................................................................................................................................50 Usage Analysis ...........................................................................................................................................................53 Plant ........................................................................................................................................................................53

ENERGY ANALYSIS .................................................................................................... 55
Statistics......................................................................................................................................................................55

DISCUSSION................................................................................................................ 58
OLC Belt Motors and Operating Practices .............................................................................................................58 Variable Frequency Drives for Major Belts............................................................................................................58 Belt Power Requirements .......................................................................................................................................59 Variable Frequency Drives for Deep Water Wells .................................................................................................59 Lighting ......................................................................................................................................................................59 Electric Demand Control ..........................................................................................................................................59

APPENDIX A – MONTHLY DATA FOR STATISTICAL ANALYSIS ............................ 60 APPENDIX B – MISCELLANEOUS LIGHTING DATA ................................................ 62 APPENDIX C – FINDINGS ........................................................................................... 63

Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

Energy Assessment Rockwell Automation Power & Energy Management Solutions

DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2.0

Rawhide Mine
Energy Assessment Table of Contents

Page 42

Lighting Control ........................................................................................................................................................63 Reduce Running Time of Select Equipment By 1 Hour per Day ..........................................................................63

Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

Energy Assessment Rockwell Automation Power & Energy Management Solutions

DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2.0

Rawhide Mine
Energy Assessment
Introduction

Page Introduction 43

The Powder River Coal Company (a Peabody Energy company) has engaged Rockwell Automation – Power & Energy Management Solutions (PEMS) to provide an energy assessment at two (2) surface coal mines in the Southern Powder River Basin. The mines are all located within 65 miles of Gillette, Wyoming. North Antelope – Rochelle Mine Rawhide Mine North Antelope Rochelle ships about 85 million tons of coal each year. The other mine are growing, and collectively ship about 30 million tons per year. The most significant operating costs are diesel fuel, blasting materials/services, and electricity. The annual cost of electricity for all three mines is over $7,000,000.

This is a report for the Rawhide Mine. It includes a statistical (top-down) analysis of electric energy consumption as a function of production and outdoor temperature, and a generalized discussion based on information and observations from all the mines.

Rawhide Typical Electricity Requirements

Peak Demand Annual Energy Monthly Cost Unit Cost Demand Charge Energy Charge Load Factor

6,700 14,500 $830,000 $ 0.057 $ 6.79 $ 0.018 25

kW MWh

per kWh per kW per month per kWh % per ton

Cost per Production $ 0.33

Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

Energy Assessment Rockwell Automation Power & Energy Management Solutions

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Rawhide Mine
Energy Assessment Introduction

Page 44

Comparison
It is interesting to compare the electrical energy requirements of the various mines. Consider the following summary:

Mine Metric NAR Peak Demand Annual Energy Monthly Cost Unit Cost Demand Charge Energy Charge Load Factor Annual Production Cost per Production 24,700 162,500 $ 5,100k $ 0.031 $ 6.79 $ 0.019 75 85 $ 0.06 Rawhide 6,700 14,500 $ 830k $ 0.057 $ 6.79 $ 0.018 25 3 $ 0.33 per kWh per kW per month per kWh % million tons per ton kW MWh Units

Rawhide has higher electricity cost per ton, and also per kWh, because of low load factor. Also, Rawhide has significantly lower total production. This also contributes to higher cost per ton because of the fixed load and also economy of scale.

The load factor at Rawhide is much lower because there is only one work shift. Load factor is based on 8,760 hours per year. With only one work shift, there is little opportunity to level the load.

This comparison will change dramatically if Rawhide goes to 24-hour operation. In that case, load factor will increase to perhaps 50% or more. The price paid per kWh could decrease by as much as 50%. The mine can be expected to use additional energy in proportion to production, however energy cost per ton will drop significantly because of the lower price paid per kWh.
Powder River Coal Company Gillette, Wyoming A Peabody Energy Company Energy Assessment Rockwell Automation Power & Energy Management Solutions DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2.0

Rawhide Mine
Energy Assessment Introduction

Page 45

Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

Energy Assessment Rockwell Automation Power & Energy Management Solutions

DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2.0

Rawhide Mine
Energy Assessment
Background

Page Background 46

Facility Overview
The Rawhide operation consists of two (2) shovels and eight (8) trucks delivering coal from one pit to one plant at an average rate of 20,000 tons per hour. The initial entry point for the coal is a doublewide hopper located near the pit. It contains a set of primary crushers that feed coal to hydraulically-driven drag belts that meter coal at a set rate onto the main belt (DC915). These hydraulic pick lines feed the coal onto the overland conveyor (OLC) using a hydraulic pump system as the prime mover.

The distance between the feed hopper and plant is about 1.5 miles which requires an OLC with three large motors (1750 hp, 4160 V). This conveyor delivers coal into an 11,000-ton surge hopper at a maximum rate of 6,500 TPH. This surge hopper in turn feeds into what is known as the ‘Old Plant’.

The Old Plant starts with a hopper including a secondary set of crushers and apron feeder which deposits coal onto a reclaim belt (CV201). This acts as a metering control for deliveries to the Old Plant. The maximum throughput is 4,200 TPH.

CV-201 transfers coal through a sampling system and then to four of the six silos via belts CV301, CV302, and CV401. The filling of the four 11,000 ton silos is done with a tripper conveyor. The other two 13,000-ton silos receive coal via transfer belt CV450 and reversing belt CV451. A small feeder conveyor attached to the bottom of each silo delivers coal to two topper silos. This is used during the train loading process where an initial ‘bulk’ load is delivered to the car via a pneumatic controlled batching system attached to the silos. The required balance of the load is delivered via the hydraulically controlled ‘topper’ silos.

Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

Energy Assessment Rockwell Automation Power & Energy Management Solutions

DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2.0

Rawhide Mine
Energy Assessment Background
General Layout

Page 47

RAWHIDE MINE:
2.5MILLION TONS '03
SINGLE PIT FACILITY SEPERATED INTO PLANT / PIT

EXTRACTION CHARACTERISTICS: COAL AND OVERBURDEN
SHOVEL / TRUCK PLANT: HOPPERS - BELTS - SILOS - LOADING HOPPERS (2): OLC AND OLD PLANT

NOTES:
COAL QUALITY (8250-8300 BTU) PIT: SHOVELS AND LOADERS TO TRUCKS DRAG LINES (0): SHOVELS (2): ELECTRIC TRUCKS (8): CAT797 400TON (8)

Total Plant / Pit Output: 15-20K tons/hr

SILO 250' TALL 15k TON CAPACITY (6) TOPPERS (2) BELTS: (6) MAIN & COAL LIFT (12) TRANSFER AND TOPPER

MINING EQUIPMENT:
COAL SHOVELS: (2)

HP , VOLTAGE, KW 800HP, 4160V, 1.0 MW AVE. 800HP, 4160V, 1.0 MW AVE.
(1) UTILITY FEED AT 69kV 4 FIXED SUBSTATIONS PRIMARY SUBSTATION UNIT 1/6.2MVA PRIMARY SUBSTATION UNIT 2 /6.2MVA SUBSTATION 10 CRUSH AREA SUBSTATION 11 MAIN DRIVE 5MVA 7.5MVA

NOTES:

BUSYRUS 295 P/H 4100 Shovel
ELECTRICAL DISTRIBUTION:

CONTROLS: RSVIEW32, RSPOWER32,
CLOGIX, SLC500

Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

Energy Assessment Rockwell Automation Power & Energy Management Solutions

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Rawhide Mine
Energy Assessment
Lighting

Page Background 48

Building Lighting
Maintenance Old Plant Sample Building Silos

Location

Usage Type
HPS

Equip Type
High Bay Bay

Total # of fixtures
98 21 27 85 66

Watts per Fixture
1000 250 150 150 150

Watts per location 98,000 5,250 4,050 12,750 9,900 8,000 752

Ballast Factor 1.15 1.15 1.00 1.00 1.00 1.15 1.15

Input watts per location 112,700 6,038 4,050 12,750 9,900 9,200 865

Total kWc 112.7 6.0375 4.05 12.75 9.9 9.2 0.8648

Location Total kWc 113

Apron Feeders to CV 201

HPS Incandescent Incandescent Incandescent

10 13

Silo Connection Belt Topper Silos

HPS HPS

20 8

400 94

19 1

Major Electric HP or Tons Processes Lighting Maintenance Old Plant Sample Building Silos Topper Silos

kWc 113 10 13 19 1

% Diversity 100% 100% 100% 100% 100%

kWd 113 10 13 19 1

Hrs/day 10 10 10 10 10 10

Run days per wk 7.00 7.00 7.00 7.00 7.00

Wks/yr 52 52 52 52 52

hrs/yr 3640 3640 3640 3640 3640

kWh/year 410,228 36,719 46,410 69,524 3,148

Process Total kWh

Process Total kW

566,028

156

Electric Distribution

ELECTRICAL DISTRIBUTION: Name
PRIMARY SUBSTATION UNIT 1 PRIMARY SUBSTATION UNIT 2 SUBSTATION 10 CRUSH AREA SUBSTATION 11 MAIN DRIVE

1 UTILITY FEED AT 69kV SUBSTATIONS from 69Kv to 4160V

Type Fixed Fixed Fixed Fixed

Voltage 69kV-4160V 69kV-4160V 69kV-4160V 69kV-4160V

kVA 6250 6250 5000 7500

Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

Energy Assessment Rockwell Automation Power & Energy Management Solutions

DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2.0

Rawhide Mine
Energy Assessment Background

Page 49

Mining Process Equipment
Pits
Major Electric HP or Tons Processes Coal Shovels Bucyrus 295 800 P/H 4100 800
Run days per wk 7.00 7.00 Process Total kWh Process Total kW

kWc 597 597

% Diversity 70% 70% 70%

kWd 418 418

Hrs/day 6 6 6

Wks/yr 52 52

hrs/yr 2184 2184

kWh/year 912,388 912,388

1,824,776

836

Powder River Coal Company Gillette, Wyoming A Peabody Energy Company

Energy Assessment Rockwell Automation Power & Energy Management Solutions

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Rawhide Mine
Energy Assessment
Plant
Major Electric Processes Plant
PRIMARY CRUSHER 1A PRIMARY CRUSHER 2A PRIMARY CRUSHER 1B PRIMARY CRUSHER 2B

Page Background 50

HP or Tons

kWc

% Diversity 67%

kWd

Hrs/day 6

Run days per wk

Wks/yr

hrs/yr

kWh/year

Process Total kWh

Process Total kW

250 250 250 250

187 187 187 187 93 93 93 93 37 45 93 1,306 1,306 1,306 149 30 30 187 187 187 187 373 373 187 373 373 187 75 112 7 7 7 7 7 7 56 93 30 30

67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67% 67%

125 125 125 125 62 62 62 62 25 30 62 875 875 875 100 20 20 125 125 125 125 250 250 125 250 250 125 50 75 5 5 5 5 5 5 37 62 20 20

6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6

7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00 7.00

52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52 52

2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184 2184

272,902 272,902 272,902 272,902 1,091,607 500 136,451 136,451 136,451 136,451 54,580 600,384 275 65,496 136,451 201,947 92 1,910,312 1,910,312 1,910,312 5,730,936 2,624 218,321 43,664 43,664 272,902 272,902 272,902 272,902 545,803 545,803 272,902 545,803 545,803 272,902 109,161 4,235,435 1,939 163,741 10,916 10,916 10,916 10,916 10,916 10,916 81,871 136,451 43,664 43,664 534,887 12,395,196 245 5,675

Primary Crusher
PICK LINE HYD PMP1 PICK LINE HYD PMP2 PICK LINE HYD PMP3 PICK LINE HYD PMP4 FOGGER AIR COMP.

125 125 125 125 50 60 125 1750 1750 1750 200 40 40 250 250 250 250 500 500 250 500 500 250 100

Pick Line
WELL PUMP DEEP WELL PUMP

Water Pumping
OLC MOTOR1 OLC MOTOR2 OLC MOTOR3

OLC Motors
RECLAIM CONV APRON FEEDER A APRON FEEDER B FEED CRUSHER A1 FEED CRUSHER A2 FEED CRUSHER B1 FEED CRUSHER B2 CV201 A CV201 B CV301 CV302 A CV302 B CV450 CV451

Feed Crusher
SILO AIR COMPRESSOR SILO TOPPER FEED1 SILO TOPPER FEED2 SILO TOPPER FEED3 SILO TOPPER FEED4 SILO TOPPER FEED5 SILO TOPPER FEED6 TOPPER MAIN FEED 1 TOPPER MAIN FEED 2 HYDRAULIC PUMP T1 HYDRAULIC PUMP T2

150 10 10 10 10 10 10 75 125 40 40

Silo Toppers Plant

Electricity
The Powder River Energy Corporation supplies electricity on the Large Power Transmission Level (LPT) Rate Schedule. The cost of electricity for the 12 months ending February 2004 was $832,637. The monthly billing demand averaged 6,656 kW --- ranging from a low of 6,158 kW in July of 2003 to a high of 7,315 kW in February of 2004.

The overall average price $0.057 per kWh. The demand component of the electric bill was $553,506 and averaged $6.79 per kW per month and the energy component of the bill was
Powder River Coal Company Gillette, Wyoming A Peabody Energy Company Energy Assessment Rockwell Automation Power & Energy Management Solutions DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2.0

Rawhide Mine
Energy Assessment Background

Page 51

$282,925 and averaged $0.018 per kWh. The hours use of demand for the year was 2,176 representing an average electric load factor of 25%.

Historical purchases of electricity are summarized from invoices in the following table.
Rawhide
Large Power Transmission (LPT)
Demand Charge Transmission, per kw Generation, per kw Total Demand Charge
Mar-03 Winter $1.05 $5.88 $6.93 Apr-03 Winter $1.05 $5.88 $6.93 May-03 Winter $1.05 $5.88 $6.93 Jun-03 Summer $1.05 $5.88 $6.93 Jul-03 Summer $1.05 $5.88 $6.93 Aug-03 Summer $1.05 $5.88 $6.93 Sep-03 Summer $1.05 $5.88 $6.93 Oct-03 Winter $1.05 $5.88 $6.93 Nov-03 Winter $1.05 $5.88 $6.93 Dec-03 Winter $1.05 $5.88 $6.93 Jan-04 Winter $1.05 $5.88 $6.93 Feb-04 Winter $1.05 $5.88 $6.93 12-Month Total/Ave

Energy Charge Generation, per kWh $0.01954 Billing Demand (kW) Actual kWh Demand Charge Energy Charge Basic Charge Power Cost Adjustment Total Monthly Charge Averages
Demand ($/kW) --- w/adj. Energy ($/kWh) --- w/ adj. Ave Cost per kWh 6,840 1,197,000 $47,401 $23,383 $600 ($857) $70,528 $6.86 $0.018 $0.059 175

$0.01954 6,839 1,197,000 $47,394 $23,383 $600 ($840) $70,538 $6.86 $0.018 $0.059 175

$0.01954 6,370 1,022,000 $44,144 $19,965 $600 ($717) $63,992 $6.86 $0.018 $0.063 160

$0.01954 6,402 994,000 $44,366 $19,418 $600 ($698) $63,686 $6.86 $0.018 $0.064 155

$0.01954 6,158 1,008,000 $42,675 $19,691 $600 ($708) $62,258 $6.86 $0.018 $0.062 164

$0.01954 6,172 994,000 $42,772 $19,418 $600 ($698) $62,092 $6.86 $0.018 $0.062 161

$0.01954 6,839 1,085,000 $47,394 $21,195 $600 ($762) $68,428 $6.86 $0.018 $0.063 159

$0.01954 7,000 1,330,000 $48,510 $25,982 $600 ($901) $74,190 $6.86 $0.018 $0.056 190

$0.01954 6,769 1,456,000 $46,909 $28,443 $600 ($1,022) $74,930 $6.86 $0.018 $0.051 215

$0.01954 6,349 1,239,000 $43,999 $24,204 $600 ($870) $67,932 $6.86 $0.018 $0.055 195

$0.01954 6,818 1,442,000 $47,249 $28,169 $600 ($1,423) $74,595 $6.86 $0.018 $0.052 211

$0.01954 7,315 1,519,000 $50,693 $29,674 $600 ($1,499) $79,468 $6.86 $0.018 $0.052 208 6,656 14,483,000 $553,506 $282,925 $7,200 -$10,995 $832,637 $6.79 $0.018 $0.057 2,176

Hours use of Demand

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Rawhide Mine
Energy Assessment Background

Page 52

Monthly Billing Demand (kW) -- Rawhide
7,600 7,400 7,200 7,000 6,800 6,600 6,400 6,200 6,000 5,800 5,600 5,400
7,315 7,000 6,840 6,839 6,370 6,402 6,158 6,172 6,839 6,769 6,349 6,818

Mar- Apr- May- Jun03 03 03 03

Jul03

Aug- Sep- Oct- Nov- Dec- Jan- Feb03 03 03 03 03 04 04

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Rawhide Mine
Energy Assessment Background

Page 53

Usage Analysis
Electricity Consumption Estimate by Application -- 12 Months Ending February 2004 Rawhide
Process Contribution To Billing Demand (kW) Annual kWh Annual Demand Annual Energy Total Annual Cost @ Cost @ Cost $6.79 per kW per Month Plant Coal Shovels Lighting 5,675 836 156 12,395,196 1,824,776 566,028 $462,532 $68,092 $12,673 $225,955 $33,264 $10,318 $688,487 $101,356 $22,991 $0.018 per kWh

Total (Estimate) Total Actual

6,666 6,656

14,786,000 14,483,000

$543,297 $553,506

$269,538
$282,925

$812,834
$832,637

Electric Cost By Application --- Rawhide --12 Months Ending February 2004
$800,000 $700,000 $600,000 $500,000 $400,000 $300,000 $200,000 $100,000 $0
Plant Coal Shovels
Plant
$101,356 $22,991 $688,487

Lighting

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Rawhide Mine
Energy Assessment Background

Page 54

Electricity Consumption Estimate by Application -- 12 Months Ending February 2004 Rawhide Plant
Process Contribution To Billing Demand (kW) Annual kWh Annual Demand Annual Energy Total Annual Cost @ Cost @ Cost $6.79 per kW per Month OLC Motors Feed Crusher Primary Crusher Pick Line Silo Toppers Water Pumping Total (Estimate) 2,624 1,939 500 275 245 92 5,675 5,730,936 4,235,435 1,091,607 600,384 534,887 201,947 12,395,196 $213,852 $158,047 $40,734 $22,404 $19,960 $7,536 $462,532 $104,471 $77,209 $19,899 $10,945 $9,751 $3,681 $225,955 $318,323 $235,256 $60,633 $33,348 $29,710 $11,217 $688,487 $0.018 per kWh

Electric Cost By Application --- Rawhide --12 Months Ending February 2004
$350,000 $300,000 $250,000 $200,000 $150,000 $100,000
$60,633 $235,256 $318,323

$50,000 $0
OLC Motors Feed Crusher Primary Crusher

$33,348

$29,710 $11,217

Pick Line

Silo Toppers

Water Pumping

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Rawhide Mine
Energy Assessment
Energy Analysis

Page Energy Analysis 55

This section includes a top-down analysis of electrical usage at the Rawhide mine. The purpose of the analysis is to understand energy usage for present operations. This is a “top-down” or Statistical Analysis which is a regression analysis of usage as a function of production and weather data at the Rawhide mine.

Statistics
The period of time used for this analysis is April 1, 2004 through December 31, 2005. The following data were required and available over this time period: • • • Coal production [tons] Electricity usage [kWh] Outdoor temperature [heating degree-days (HDD) and cooling degree days(CDD)]

Actual monthly data used in the analysis are given in Appendix – A. The regression analysis involves finding a best-fit straight line for electric energy usage (kWh) as a function of coal production and weather. The result was as follows: Energy [kWh] = 156,700 + 1,903 x production [1000 tons] + 163 x heating [HDD] This expression can be used to calculate historical electric energy usage at Rawhide, given production and weather data. It indicates a fixed component of about 156,700 kWh each month, independent of production level or weather. Further, it indicates that 1,910 kWh are added for each 1000 tons of coal produced, and 163 kWh for each heating degree day. Cooling degree days have no significant impact on Rawhide energy usage. The following table shows how accurate the expression is in calculating historical usage: Cumulative Cumulative Number of Percentage Months 0 3 3 14% 1 2 5 24% 3 1 6 29% 4 1 7 33% 5 1 8 38% 6 2 10 48% 7 1 11 52% 20 7 18 95% There are a total of 21 months in the time period studied. The error table indicates the following: Error [+/%] Number of Months • • • In 6 of the 21 months studied (29% of the sample), the expression correctly predicts energy usage within +/- 3% In another 5 of the 21 months studied (24% of the sample), the expression predicts actual energy usage within +/- 7%. Including line #1 and line #2, the expression predicts actual usage within +/7% 52% of the time. There are 3 statistical outliers in 2004 (August, September and December). In these month, the expression has an error of greater than 20%

Detailed results are given in the Appendix. Note that 2005 follows the model much better than 2004. Compared to other studies of this type, the model has higher errors than normal. This could be a result of some data collection errors, or other operational factors that affect energy side from coal production and weather. Annual results are as follows:
Powder River Coal Company Gillette, Wyoming A Peabody Energy Company Energy Assessment Rockwell Automation Power & Energy Management Solutions DOE: DE-FG36-40GO14034 RA Project Number: P1830-0932 Revision: 2.0

Rawhide Mine
Energy Assessment
Year 2004 (Apr–Dec) 2005 Actual Energy 12,278,327 27,058,723

Page Energy Analysis
Predicted Energy 12,726,081 26,621,022 Error 447,754 437,700 Error % - 4% 2%

56

As expected, the expression becomes more accurate as the period of time is extended. When applied to September 2004 the expression had an error of 25%. However, the error is reduced to 4% for the last 9 months of 2004. By definition, the average error over the entire study period (21 months) is zero. This is a fundamental characteristic of regression analysis. Rounding errors result in a non-zero total of 2%. If applied to individual days, the errors would be greater. However, the results are somewhat useful in understanding energy usage and the impact of weather and production. The following are important observations: 4. Energy usage in a mining operation should be a strong function of production, as is the case at Rawhide. Note that the fixed portion (156,700 kWh per month) is only 9% of total energy usage in a typical year. Compare this to NAR which has a fixed component of 52%. The fixed portion is quite small at Rawhide; most energy usage is a function of production. For this reason, energy cost per unit of production is expected to change only a small amount as production is increased or decreased. Energy cost per ton will increase slightly at lower production and decrease slightly at higher production; provided that single-shift operation is maintained. An additional work shift at Rawhide (24-hour operation) will dramatically change the equation and reduce energy cost per ton. Load factor will increase from 25% to perhaps 50% or more. This could reduce the price paid for electricity (per kWh) by as much as 50%. High ambient temperature does not impact usage significantly. The northern location of this mine, at high altitude is not expected to have a significant cooling load.

5.

6.

7.

Mine Energy Model

weather fixed 5% 9%

production 86%

Additional information and all the source data are given in Appendix – A. A graphical depiction of the regression analysis (production against energy) showing the strong correlation is given on the next page.

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Rawhide Mine
Energy Assessment Energy Analysis

Page 57

3000

Monthly Energy [MWh

2500 2000 1500 1000 500 0 0 200 400 600 800 1,000 1,200 1,400

Monthly Production [ktons]

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Rawhide Mine
Energy Assessment
Discussion

Page Discussion 58

OLC Belt Motors and Operating Practices
Three (3) areas should be considered for belt energy savings; no-load operating practices, power factor correction, and control under load conditions. The first refers to times when the belt is presently operated with no coal on the belt, such as before and after the work shift. The second is aimed at correcting power factor at each motor as currently installed. The third is where drives are often mentioned as a possibility. This one-shift operation does not have the same issue as other mines with equipment running unloaded during shift changes. However, it was noted that approximately one (1) hour of unloaded operation each day could possibly be eliminated by changing start-up and shutdown procedures. The resulting annual savings is estimated at $35,000. This assumes less run time for the OLC as well as related coal transport equipment. Variable Frequency Drives for Major Belts The OLC belt is run continuously at constant supply frequency (no drives). There would appear to be an opportunity for energy savings associated with motor speed control (variable frequency drives). Based on the detailed analysis at NAR, the following loads are estimated for the OLC belt. Rated Load [tons/hr] 6,500 Horsepower @ average @ no load load 1,500 135

Belt OLC

@ rated load 2,500 – 3,000

Connected 3 x 1,750

The load model and field measurements from NAR indicate that major belt drive motors are typically underloaded. However, this is a conveyor application where variable speed is likely to interferer with performance. For example, these belts move coal, and running them at 50% speed to save energy is just not practical The brake horsepower delivered to the conveyor drive shaft is a function of rotational speed and torque. There is presently a mismatch between the conveyor requirements and the motor capability. Conveyor Requirements – The conveyor power requirement is a function of lift, coal load and friction. Since lift and coal load cannot be changed, the opportunity for reduced requirement is friction. The NAR model quantifies the friction load and allows for estimates of potential savings from low-friction bearings, etc. Motor Capability – Each motor has a speed-torque characteristic and efficiency associated with various operating points. As the motor is unloaded, the power factor and efficiency decrease. Power factor decreases because reactive current requirements decrease by a small amount while real current is proportional to mechanical load and decreases significantly. The application of drives or other motor changes will not impact brake horsepower requirements at a given delivery [TPH]. The only savings would result from the motor being able to supply the conveyor requirement more efficiently. In theory, a transmission between the motor and conveyor could be used to allow the motor to run at reduced speed while maintaining belt speed. While technically feasible, this is not considered a viable option. The cost could rival that of replacing the motor. There are also benefits to the larger motors. The extra power could be needed from time to time under extreme conditions to get the belt moving, or when one of several motors is out of service. Therefore, savings associated with changes to the motor/drive assets must come from increased motor efficiency and/or reduced reactive power requirements (power factor closer to unity.) The available savings is relatively small. Another consideration is the possibility of reducing the number of motors in operation. In the case of OLC, there are three (3) motors and the belt requirements could be met without all motors in operation. A detailed analysis would be required over a period of time to verify belt requirements and the practicality of this option.
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Rawhide Mine
Energy Assessment Discussion
Belt Power Requirements

Page 59

One challenge in sizing major belt motors is the tradeoff between operating efficiency and the occasional need for extra power. Factors such as static friction, load momentum (accelerating coal), icing, etc. can require extraordinary torque and power. Unfortunately, that extra motor capacity then remains on-line for the vast majority of the time when operations are normal. In future designs, consideration should be given to this issue. Other methods of providing temporary, extra torque/power should be considered.

Variable Frequency Drives for Deep Water Wells
There are number of large motors at the mine that operate well pumps. Factors that affect the efficiency of pumping include matching the pump and motor characteristics (speed – torque). This allows both pieces of equipment to operate in their most efficient range. Impellor selection/trim is important. Unless the flow rate and/or hydraulic head are significantly different than anticipated during the design process, the motor-pump match is probably correct. Other factors that impact efficiency include pump maintenance, specifically impeller condition, and water distribution piping and valves. A partially-closed value in the distribution network being used to throttle water flow is a source of inefficiency. It is better to slow the pump with a variable-speed drive than to operate at full speed and throttle the flow (essentially increase the head) with partially-closed valves. Variable speed control comes with a price, and it is unlikely the investment could be justified for these pumps. Any significant mismatch between pump and motor should first be addressed by considering impeller trim or changing the motor.

Lighting
The study estimates total annual lighting cost of about $ 26,000. Knowing that number helps put potential savings estimates in perspective. Savings would result from more diligent lighting control (turned off when not needed) and upgrading to high-efficiency lighting. For the purpose of estimating savings, it is not correct to use the average cost of electric energy ($ 0.057 kWh) because changes may not reduce demand. In particular, lighting control usually does not impact demand. So estimates must use only the energy charge component ($ 0.018 / kWh) for savings calculations. The annual savings associated with lighting control is about $ 2,000. A small automatic control system (timers) or simple work practice changes (turn them on/off manually as needed) are recommended for consideration. High efficiency lighting could also be considered. The recommendation is to install high-efficiency fixtures as the opportunity arises during normal maintenance. A wholesale replacement of fixtures is unlikely to have an acceptable return on the investment. This is based on findings at other mines such as NAR.

Electric Demand Control
Electricity prices have two (2) major components; energy and demand. Analysis is usually based on the average cost of $0.057 per kWh. There is an assumption that all loads contribute equally to the overall demand, and therefore, demand will be reduced proportional to energy. In the case of lighting control, only the energy component ($ 0.018 per kWh) was used. It is known that demand will not be significantly affected by lighting control. Using the lower cost figure yields a conservative estimate. The mine load factor averages 25% which is low considering that other mines average 65 to 80%. However, this mine is operated with one work shift. Since load factor includes all 8,760 hours in a year, a low load factor is expected.

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Rawhide Analysis
Energy Assessment
Appendix A – Monthly Data for Statistical Analysis

Page Appendix A 60

Month April May June July August September October November December Total 2004 January February March April May June July August September October November December Total 2005

Energy [kWh] 1,460,361 1,610,292 1,542,411 1,579,144 990,561 1,088,397 1,316,522 1,457,295 1,233,345 12,278,327 2,175,336 1,906,971 2,543,795 2,279,424 2,358,437 1,951,586 2,054,244 2,201,995 2,179,036 2,448,187 2,704,819 2,254,893 27,058,723

Production Total [ktons] 485 678 587 665 657 614 633 651 651 5,620 831 720 1,173 1,063 1,117 987 956 1,032 1,035 1,161 1,199 1,131 12,407

Heating DD 560 362 155 23 70 210 506 866 1043 3,795 1221 919 846 600 448 151 12 56 162 496 807 1197 6,915

Cooling DD 0 3 40 205 91 46 0 0 0 385 0 0 0 0 1 105 285 140 57 9 0 0 597

Weather data was taken from a National Weather Service weather station at the Gillette Campbell County Airport (GCC) in Gillette, Wyoming.

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Energy Assessment Appendix A

Page 61

Month April May June July August September October November December Total 2004 January February March April May June July August September October November December Total 2005

Energy [kWh] Actual 1,460,361 1,610,292 1,542,411 1,579,144 990,561 1,088,397 1,316,522 1,457,295 1,233,345 12,278,327 2,175,336 1,906,971 2,543,795 2,279,424 2,358,437 1,951,586 2,054,244 2,201,995 2,179,036 2,448,187 2,704,819 2,254,893 27,058,723 Predicted 1,171,235 1,505,331 1,298,665 1,425,392 1,419,269 1,358,721 1,444,648 1,537,582 1,565,239 12,726,081 1,938,359 1,676,221 2,527,407 2,278,129 2,356,315 2,059,996 1,978,743 2,130,467 2,153,392 2,446,863 2,570,612 2,504,520 26,621,022

Error [kWh] 289,126 104,961 243,746 153,752 -428,708 -270,323 -128,126 -80,287 -331,894 447,754 236,978 230,751 16,388 1,295 2,122 -108,410 75,501 71,528 25,644 1,324 134,207 -249,627 437,700 [%] 20% 7% 16% 10% -43% -25% -10% -6% -27% - 4% 11% 12% 1% 0% 0% -6% 4% 3% 1% 0% 5% -11% 2%

Production Total 485 678 587 665 657 614 633 651 651 5,620 831 720 1,173 1,063 1,117 987 956 1,032 1,035 1,161 1,199 1,131 12,407

Degree Days Heating 560 362 155 23 70 210 506 866 1,043 6,781 1,221 919 846 600 448 151 12 56 162 496 807 1,197 6,915

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Rawhide Mine
Energy Assessment
Appendix B – Miscellaneous Lighting Data

Page Appendix B 62

Building Maintenance Old Plant Sample Building Silos

Location Apron Feeders to CV 201

Silo Connection Belt

Type HPS HPS Incandescent Incandescent Incandescent HPS

No. 98 21 27 85 66 20

Power (W) 1000 250 150 150 150 400

Ballast Factor 1.15 1.15 1 1 1 1.15

Total kW 112.7 6.0 4.1 12.8 9.9 9.2

Hour Usage / Yr 8760 8760 8760 8760 8760 8760 Totals

Demand Cost $662.68 $35.50 $23.81 $74.97 $58.21 $54.10 $909.27

Energy Cost / Yr $19,285.97 $1,033.18 $693.06 $2,181.86 $1,694.15 $1,574.36 $26,462.59

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Rawhide Mine
Energy Assessment
Appendix C – Findings

Page Appendix B 63

As part of the effort, an energy auditor has provided the following suggestions, included here for the record.

Lighting Control
The following table identifies lights that are presently on 24/7 that can be turned off at least 12 hours per day. Turning these lights off will not reduce the billing demand, however annual energy consumption will be reduced by 125,651 kWh for a savings of $2,279 at $0.018 per kWh.
Turn Select Lights Off When Not Needed
kW 29 off hours per year 4,380 kWh Savings 125,651

Energy Savings $2,279
Total # of fixtures Watts per Fixture Watts per location Ballast Factor Input watts per location

Building Lighting

Location

Usage Type

Equip Type

Total kWc lights not needed 24/7 lights not needed 24/7 lights not needed 24/7

Old Plant Sample Building Silos

Apron Feeders

HPS Incandescent Incandescent

Bay

21 85 66

250 150 150

5,250 12,750 9,900

1.15 1.00 1.00

6,038 12,750 9,900

6.0375 12.75 9.9

Reduce Running Time of Select Equipment By 1 Hour per Day
Rawhide operates one work shift. The following table identifies motor load that is running unnecessarily during the shift start-up and shut-down. It is estimated that the following motor load totaling 5,338 kW can be shut down for at least 1 hour each day. As with lighting, the demand charge is not affected, however energy will be reduced by 1,948,398 kWh annually for a savings of $35,518 at $0.018 per kW

Reduce Running Time of Select Equipment By 1 Hour per Day -- Plant
Plant Primary Crusher Pick Line OLC Motors Feed Crusher Total Shut Down kWd 500 275 2624 1939 5,338 1 365 365 1,948,398 $0.018

kWd hours per day days per year hours per year kWh per year Energy cost per kWh

Annual Savings $35,518

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Rawhide Mine
Energy Assessment Appendix B

Page 64

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