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Estimating Efficiency and Establishing Baselines for Verifying the Energy Saving Benefits Associated with Servicing Air

Estimating Efficiency and Establishing Baselines for Verifying the Energy Saving Benefits Associated with Servicing Air Conditioners. Todd M. Rossi, Ph.D. Field Diagnostic Services, Inc. Presentation. Estimating efficiency economically on a large scale Benchmark for comparison

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Estimating Efficiency and Establishing Baselines for Verifying the Energy Saving Benefits Associated with Servicing Air

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  1. Estimating Efficiency and Establishing Baselines for Verifying the Energy Saving Benefits Associated with Servicing Air Conditioners Todd M. Rossi, Ph.D. Field Diagnostic Services, Inc.

  2. Presentation • Estimating efficiency economically on a large scale • Benchmark for comparison • Selling service based on energy savings payback

  3. Important Technology • A/C consumes much energy • Efficiency sensitive to service • First technology relating service effectiveness to energy savings deployed on large scale “You can’t fix what you can’t measure”

  4. Define Efficiency

  5. Electric Heated Evaporator

  6. DX Evaporator - Air side

  7. Refrigerant Side Measurement

  8. Compressor Performance Data

  9. Estimating Efficiency

  10. Required Measurements

  11. Instrument palm comp AMB RWB LT ST LP/DP CT SP ET

  12. Practical Measurements • Commonly used in the field for diagnostics • Field personnel comfortable with concepts and required instruments • Special apparatus speeds up measurement process

  13. Data Collection Tool

  14. Efficiency Benchmark for Service • Same unit serviced to achieve: • “benchmark” • “ideal” • “as new” • No design changes

  15. A/C Units Respond to their Environment • Characterized by: • AMB - Outdoor Drybulb Temperature • RWB - Evaporator Entering Air Wetbulb • Assumptions • Air cooled, DX Equipment • Water condensing on Evaporator

  16. Characterizing Performance • Evaporating Temperature • ET(AMB,RWB) • Suction Line Superheat • SH(AMB,RWB) • Standard Charging Chart - Fixed Orifice • Condensing Temperature Over Ambient • COA(AMB,RWB) • Liquid Line Subcooling • SC(AMB,RWB)

  17. Getting the Benchmark • Measure the driving conditions (AMB, RWB) • Evaluate expected ET, SH, COA, SC for current AMB and RWB • “Ideally” these are the values measured when the unit was new and installed properly under the current conditions.

  18. Estimating Benchmark Efficiency • Feed expected values (no faults, current conditions) of ET, COA, SH, SC into the same COP calculation as the measured values.

  19. Efficiency Index • “Efficiency of the unit as it is currently operating relative to how it could be performing if serviced to “like new” under the same operating conditions”

  20. Example - Dirty Condenser

  21. Advantages of EI • Same compressor model used to calculate actual and expected performance - reduces sensitivity to model errors • Intrinsic value - does not scale with size of unit

  22. Field Measurement - EI * based on a sampling of 506 units

  23. Creating Customer Value • Get from EI to $ by considering: • Nominal capacity (tons) • SEER/EER rating • Utility rates (e.g $/kwh) • Annual runtime hours • Estimate $/year wasted because of degraded equipment performance

  24. Service Decisions • $/year in wasted energy • Compare to cost of service to enhance performance • Making service decisions (e.g. when to clean coils) based on energy savings payback. • Other criteria also exist in making service decisions

  25. Service Strategically • Assess all units in portfolio • Prioritize units with most compelling service needs (e.g. energy payback) • Target service for maximum effect • Verify expected performance

  26. Prioritize Sites

  27. Energy Savings Example Case study: • Big box retail store • 14 RTU’s, 11 with two stages (25 cycles)

  28. Results: All stages all units Before Tune-up: 318 kW 46,917 hours of cooling • After Tune-up: 268 kW 37,738 hours of cooling • Savings: 50 kW (15.8%) 9,179 hours (19.6%)

  29. Payback • Total costs of service: US$ 4,300 • Estimated energy savings in one year: US$ 21,000

  30. How the $ add up • Give a tech a tool • He applies it to 1000 tons • 100x10 ton units, 200x5 ton units • Units run between 300 and 2500 hours/year • 1 kW/ton - 12 EER • 10 cents/kwh

  31. How the $ add up • That tech is responsible for roughly $100,000 in energy spent annually. • 10% improvement because of strategic application of the same resource based on better information • $10,000 saved each year • How much would you pay for this information?

  32. Benefits • Quick measurements • It doesn’t have to cost much more or require high skill • Measure and Document Efficiency • Target Service Strategically • Verify Effectiveness

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