|ESA-073-2 Public Report (J.R. Simplot, Nampa)|
|Written by USDOE Energy Efficiency & Renewable Energy|
|Friday, 15 July 2011 10:18|
ESA-073-2 Public Report
The JR Simplot plant in Nampa, Idaho, produces frozen potato products, including patties, triangles, and French fries. Potatoes are cleaned, peeled, cut (slices, wedges, fries, or shredded), fried, quick frozen, packaged, and shipped. Primary process equipment includes peelers, cutters, defect removal, fryers, freeze tunnels and packaging equipment. Boilers, air compressors, and 2-stage ammonia refrigeration compressors support the process.
Objective of ESA:
The objective of the ESA is to model your compressed air system using the AIRMaster+ software tool and to use the tool to identify savings from several measures that would improve system efficiency. It is not the objective of the ESA to look at all potential plant improvement opportunities. The JR Simplot plant has an objective to reduce electricity use by 10% and natural gas by 2%, aggressively reduce energy consumption at each of their facilities.
Focus of Assessment:
The focus of the ESA is for plant personnel to understand how the appropriate DOE tool can be effectively applied in the plant. The focus of this ESA is the main compressed air system.
The compressed air system includes 3 compressors: two 150 hp Gardner Denver lubricated screw compressors with turn- valve and unloading controls and one 75 hp Gardner Denver lubricated screw compressor with throttle control. Typically two compressors operate depending on load. One compressor operates during down days. An AirTek twin tower desiccant dryer has an electric heater and dew-point control to improve efficiency and is operating properly. The plant air compressors currently cost approximately $37,000/yr to operate.
The air distribution system has three (3) 650 gallon receivers and one (1) 120 gallon receiver. There is approximately 1750 feet of 2” through 4” header piping throughout the plant that adds an additional 365 gallons of storage capacity. The piping system is efficient with approximately 2 psi drop from the centrally-located compressor room to the far ends of the plant.
Approach for ESA:
The two compressors with turn valve controls were not operating properly at the time of the site visit. The local air service company ordered parts and installed them the following week. The service company believes that they are now operating properly although both compressors appear to be operating below rated power.
Note what you would expect would be Near Term, Medium Term, Long Term opportunities. See definitions below:
1. Reduce Air Leaks (savings 0.14% of plant electricity use, 4.6% of compressor use, Near Term)
Solution: Tag and repair air leaks. An air leak generally costs around $800/year at $0.05/kWh by the time it can be heard. Fixing leaks is generally low cost in both time and materials, with paybacks typically less than one-year
Savings: The plant air system operates 8,760 hours/year. AirMaster calculates savings to be $1,680/yr
2. Reduce System Pressure (savings 0.07% of plant electricity use, 2.3% of compressor use, Near Term)
Solution: Recommend reducing the discharge pressure at the compressors by 5 psi initially, and more in smaller increments if there are no problems. If a problem arises, consider the cost of resolving the problem versus the savings from reducing pressure. For example, adding a secondary receiver near the end use to meet an intermittent load, or adding a dedicated or booster compressor to satisfy a critical or higher pressure load.
Savings: Savings from reducing system pressure 5 psi are approximately $850/yr
3. Improve End Use Efficiency (savings 0.02% of plant electricity use, 0.7% of compressor use, Near Term) Situation: A pneumatic diaphragm pump uses approximately 15 scfm to move waste water to an adjacent filter with
Solution: Replace the diaphragm pump with an electric pump. We estimated flow and pressure to determine air use from the manufacturer’s specs at approximately 15 scfm. This would require approximately 3 compressor hp to produce. Since electric motors are approximately 10 times as efficient as pneumatic motors, including the compressor efficiency, estimate that the motor would need to be approximately 1/3 hp.
Savings: AIRMaster calculates savings to be approximately $300/yr. We estimated the cost of an electric pump and electric service to be $2,000 for a 6.5 year payback. Don’t recommend this measure due to the payback. It was included as an example of how to calculate savings from replacing less efficient compressed air uses with other methods, such as electric motors, fans, vacuum pumps, or mechanical methods. For example, the plant has several compressed air venturis that pump chemicals for cleanup water.
4. Use Unloading Controls (savings 1.13% of plant electricity use, 39% of compressor use, Near Term)
Solution:I recommend using the existing automatic unloading feature and overrun timer to turn off compressor #4 if it is not needed. This allows significant energy savings from turning a compressor off, while returning to operation immediately and automatically if it is needed.
Savings: Savings from turning off #4 compressor when it is not needed are approximately $14,500, 39% of current air system use.
5. VSD Compressor (savings 0.09% of plant electricity use, 3.1% of compressor use, Near Term)
Solution: Replace it with, or add, a more efficient compressor at part loads (swing compressor). There are several strategies to achieving this objective. One is a load-unload compressor with adequate storage capacity to avoid short- cycling. Another is a Variable Speed Drive (VSD) compressor. Both operate at similar part load efficiencies.
Savings: Savings are relatively small because the small compressor currently only operates on down days (48/year). However, an efficient swing compressor might find more use as plant loads change in the future. Many utilities now have incentive programs to support system improvements such as this one. AIRMaster calculates savings to be approximately $1,000/yr at a cost of approximately $35,000 before incentives.
Management Support and Comments:
Plant management has recently started a comprehensive corporate energy conservation plan (March 2007). The plan will evolve and become more robust as they move forward.