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Whole Building Recommissioning in Retail: Energy Optimization Approach

This regional forum on April 7th, 2009 explores a whole-building approach to energy savings in commercial retail facilities. Key topics include project methodology, market potential, and benefits. Learn about the origins of this approach, energy savings methodology, and the verification of savings process. Discover the importance of persistence monitoring and the quantification of energy savings. With a focus on leveraging investments, capacity building, and driving a market towards systems approach, this event provides valuable insights for optimizing buildings and ensuring long-term energy efficiency.

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Whole Building Recommissioning in Retail: Energy Optimization Approach

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  1. Regional Technical ForumRecommissioning commercial retail facilities:A whole building approach to energy savingsApril 7th, 2009Presented by:Jeremy LitowJamie AnthonyMark Effinger

  2. Recommissioning commercial retail facilities:A whole building approach to quantifying energy savings • Overview • Goal today: RTF provisional approval of approach for pilot projects • In brief: • Project approach and value • Market potential and benefits • In detail • Origins • Energy savings methodology • Next steps

  3. Project approach and value • What is whole building recommissioning? • Optimize all building systems, 80%+ of usage • Why is it a useful approach? • Missed opportunities • Why now? Evolution • Market • Energy cost • Technology • Program • Technical approach • Persistence

  4. Overview - project approach • Interval metering at the building level, pre and post • Pre inspection and documentation, sensors and logs • Recommissioning process • Post inspection and documentation • Energy savings quantified (more later) • Persistence monitoring (three year)

  5. Market potential • Building types – refrigeration is important • Convenience stores • Grocery stores and standard supermarkets • Large stores • Savings range • Average of 7-10% annual savings • Typical range 5-15% • 1 in 10, 20% or more possible

  6. Benefits of taking a whole building approach • Big picture • Leveraging AMI investments • Leadership • Capacity building • Drive market to systems approach • Measurement to determine savings more powerful than estimation • Local picture - Optimized buildings • Systems approach • No missed opportunities • Persistence monitoring (3 years)

  7. Origins of the whole building approachand basis of the methodology • Long history, 1980s PRISM • IPMVP, 1997 • ASHRAE Guideline (GL) 14-2002 • ASHRAE Research project 1050, 2002 • California Commissioning Collaborative – Guideline for Verifying Existing Building Project Savings Using Interval Data Energy Models: IPMVP Options B and C, 2008 • “Verification of Savings” methodology • Whole building energy use • Many, interactive ECMs

  8. Verification of whole building approach:normalized savings • Acquire baseline data, utility or logged • Model energy use as function of variable(s) (e.g. DB) for pre ReCx • Estimate savings and savings uncertainty and required post period • Acquire post-ReCx data, utility or logged • Model energy use as function of variable(s) for post • Drive each model with “normal” conditions (TMY or influential variables) to determine annualized pre and post energy use • Savings = modeled annualized baseline - modeled, annualized post-ReCx • Evaluate overall uncertainty using ASHRAE GL 14

  9. Energy use Ambient Temp Energy use C B2 B1 B3 B1 C Verification of Savings (VoS) methodology: discussion of the method, 1 VoS is a proven method • Change point model, all hourly power data points with corresponding DB temperature • We also looked at other methodologies Ambient Temp 2 Parameter model 4 Parameter model

  10. Verification of savings methodology: discussion of the method, 2 Example follows a proven method among several options • Method uses statistics to determine accuracy • R2: proportion of variability in a data set that is accounted for by the statistical model • 0 to 1 range, >.7 considered “good” • CV (RMSE): differences between values predicted by a model and the values actually observed from the thing being modeled • %, <7% “good” • R2: provides a measure of how well future outcomes are likely to be predicted by the model. • CV (RMSE): evaluates the relative closeness of the predictions to the actual values

  11. Verification of savings methodology: discussion of the method, 3 Example follows a proven method among several options • Range of post data to see temp variation, typically over swing season • Latent loads (case infiltration/defrost) accounted for? • DB is proven for other building types • DB is provides best correlation to power vs. WB, RH, DP, W • Will look at other variables, evaluate if DB is best for PNW CZ and refrigeration • Need to field test • Estimated savings uncertainty–CCC meets approach, ASHRAE GL 14 requirements • 68% confidence with < or = to 50% uncertainty ok

  12. Example: Verification of savings methodology • Sample site • Grocery 100,000 ft2 • ReCx and retrofits • 591 days of interval data • 411 pre • 180 post • OATDB 1F to 110F • Average 56F • RH 4.5-100% • Average 53% • Observed OAT 73% of TMY range

  13. Pre change point Post change point Energy savings calculation methodology • Change point on all data, DB R squared: .74 and .64 CV (RMSE): 5.5% and 5.2% Annual savings: 541,520 kwh

  14. Energy savings calculation methodology • Method comparisons • Change point on all data, DB • Change point on all data, WB • Linear on all data, DB • Linear on all data, WB • 2nd degree polynomial, averaged power vs. weather bin, DB • 2nd degree polynomial on all data, DB • 2nd degree polynomial on all data, WB

  15. Energy savings calculation methodology • Other areas of interest • Post period perspectives • Post ReCx duration • Season very important, range of temperatures needed • Period can be shorter if timed right • Estimated savings uncertainty

  16. Change point for this building, this CZ Post period duration and timing 1+ year pre project: R2 .72 and CV RMSE 5.7%

  17. Post period duration and timing 2 months post project Dec 07-Jan 08: R2 .27 and CV RMSE 6.7%

  18. Post period duration and timing 2 months post project Mar-Apr 08: R2 .69 and CV RMSE 4.2%

  19. Post period duration and timing 3 months post project Dec 07-Feb 08: R2 .36 and CV RMSE 6.2%

  20. Post period duration and timing 3 months post project Feb-Apr 08: R2 .67 and CV RMSE 4.8% Nearly as good as 5th mos post!

  21. Post period duration and timing 4 months post project Dec 07- Mar 08: R2 .49 and CV RMSE 5.8%

  22. Appropriate change point visible Post period duration and timing 5 months post project Dec 07- April 08: R2 .60 and CV RMSE 5.6%

  23. Energy savings calculation methodology • Uncertainty – using CCC Verification of Savings method

  24. Conclusions on methodology • Use change point models with driving variable(s) • Look for importance of latent loads in pilots • Post required will vary with season • Shorter in the spring than in the winter • Uncertainty – follows VoS guidance, meets ASHRAE GL 14

  25. Next steps – pilots • Provisional approval to claim savings using this approach • Pilots on several facilities • Refine approach • Present findings to RTF

  26. Recommissioning commercial retail facilities:A whole building approach to energy savings Discussion

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