High Efficiency Evaporator Coils for Medium Temperature Cases

1. High Efficiency Evaporator Coils for Medium Temperature Cases • Dustin Bailey, Engineer • PECI • Jan 5, 2010

2. Acknowledgements • We would like to thank the following utilities for support • BPA • PSE • AVISTA

3. Purpose • Deemed measure approval for upgrading evaporator coils from standard to high efficiency in new MT cases. • Upgrading the coils provides savings independent of other component measures. • Energy savings should be deemed based off total case load going to compressor system, independent of climate zones.

4. Agenda • Background • Description of Measure • Compressor System Interaction • Auxiliary Load Sensitivity • Energy Savings • Adjustments for Energy Savings • Unitized Energy Savings • Floating Suction Interactivity • Energy Savings and Payback • Measure Life • Terms and Conditions • Conclusion

5. Background - Measure Description • Current measures are for complete case replacement. This causes the following problems: • only one baseline condition can get savings as defined as a “standard case” • efficient evaporator coil savings are often ignored • Proposing measure for high efficiency evaporator coils for the critical case independent of other case component measures • Modeled in eQUEST using the PECI GrocerSmart model as the template

6. Background - Efficient Coil • Description of Proposed Scenario • An efficient coil has more area than a standard coil allowing for the same heat transfer with a lower ΔT • Q=U*A*ΔT • An efficient coil allows the suction group temp of the compressor rack to rise 3 deg F • Depending on the type of product in the case, efficient coils allow for varying increases of saturated suction temperature (SST). • 3 deg F is the smallest average increase and was chosen to be conservative.

7. Background - Compressor System Energy Gap • Compressor Discharge By allowing the SST of the compressor to rise, the power the compressor must exert is reduced. Energy savings is calculated for a multiplex system as shown below: • Compressor Suction

8. Background - MT Refrigeration System

9. Background - Model Data • Description of Pre and Post Scenario • Savings = 13,000 kWh

10. Background - Auxiliary Sensitivity • Description of Baseline • Different baselines with different auxiliary loads: • Lamp (T12, T8, LED) • Doors (Door, No Door, Efficient Door (no/low ASH)) • Evaporator Motors (SP, ECM, PSC) • Conclusion: Since savings was independent of different baselines, T8 ND-ECM was chosen to be the representative case as it is a common retrofit case

11. Adjustments for Energy Savings • By increasing the SST of the critical load, the power of the compressor will decrease resulting in system energy savings. • Key assumptions • The compressor set point (suction group set point) is 2 deg F less than needed by the critical case • Efficient coils will decrease the TD by 3 degrees (averaged data from various manufacturers) • Floating suction control is present on 26.9% of all refrigeration systems,and 21% (conservative) of the MT cases have doors (EnergySmart audit data) • Results were modeled using eQUEST with T8 ND ECM on the critical case in the PECI GrocerSmart Model

12. Unitized Energy Savings Before Floating Suction Interactivity Compressor power scaling with the reduction of suction load Savings for various weather zones in the PNW without floating suction control

13. Floating Suction Interactivity Floating suction reduces available energy savings from the efficient coil measure Effect of doors on the evaporator savings for a multiplex system with floating suction control.

14. Energy Savings and Payback • Total system MBH difficult to quantify • Quantify saving per linear foot of total display case associated with compressor group • Using GrocerSmart model as the prototypical grocery store: • T8 ND-ECM model: • Assuming $0.10 per kWh this results in a savings of $2.75/ln ft of total system case length • Cost data was collected from a variety of manuf for the coil upgrade and adjusted according to copper commodity prices • The conservative estimate for cost is $42.5/ ln ft • EnergySmart audit data shows that the median number of cases replaced is 82 ft for a cost of $3,485 • Therefore, the typical store’s simple payback period can be calculated:

15. Typical Case Replacement Lengths • Payback is proportional to the length of case replaced with HE coils and case length can vary from store to store.

16. Measure Life Assumptions • Measure Life/Effective Useful Life is assumed to be the same as evaporator motors which have a life of 15 years • Southern California Edison1, PG&E2 and BPA3 program all use 15 year measure life for ECMs • 1Energy Savings Potential for Commercial Refrigeration Equipment. June 1996. U. S. Department of Energy. Arthur D. Little. p 5-51 • 2CALMAC Protocols, Appendix F, Effective Useful Live Values for Major Energy Efficiency Measures, September 2000 • 3Council Plan 1996; 15 year EUL used for all Retrofit HVAC Systems & Controls including motor retrofits

17. Terms and Conditions • Must replace an existing medium temperature evaporator standard coil with a high efficiency coil on the critical case(s) to result in a compressor suction group saturated suction temperature rise of at least 3 degrees. This is done through case replacement and several cases may need to be replaced to ensure the resulting critical case(s)’ coil(s) are replaced. A design review is required by the program to confirm the which cases must be replaced. The savings of this measure are independent of other case component measures and those measures may be claimed separately. If several suction groups exist this measure may be applied to each individually.

18. Conclusion • Measure provides large opportunity for savings through more efficient operation of a refrigeration compressor system • Efficient evaporators coils must be in the critical case • The calculated savings is for a multiplex system with a rise of 3 degrees of SST • Floating suction controls reduce available energy savings efficient evap coils • factored into the unitized energy savings • Cost variability—based on the total length of the critical case replaced • Requesting approval for high efficiency evaporator coils for medium temperature cases as a measure