Evaluation results of twelve commercial air-conditioning energy efficiency programs

Ean Jones and Robert Mowris, Robert Mowris & Associates, USA
Kathleen Carlson, Verified, Inc., USA

Keywords

international performance measurement and verification, protocol, monitoring, measurement, evaluation, verification, commercial air conditioners, air conditioning, cooling towers, energy efficiency, thermal storage, packaged air conditioners, chillers, cooling towers, controls, evaporative pre-coolers, ground source heat pumps

Abstract

Monitoring and evaluation results and costs are provided for twelve commercial air conditioning energy efficiency programs implemented by eleven California public utilities. The programs provided incentives for energy efficient packaged air conditioners, ground-source heat pumps, variable-frequency drive chillers, energy management systems, chiller and cooling tower optimization controls, wine thermal storage, evaporative pre-coolers, and refrigerant charge and airflow tune-ups. Seven large custom projects accounted for 84 % of total kWh savings and 75 % of peak demand savings. Data loggers were installed to monitor pre- and post-retrofit peak demand and energy use for chillers, cooling towers, controls, and packaged units. Peak kW savings are based on 15‑minute kW measurements of pre- and post-retrofit conditions. Energy savings are based on engineering analysis, regression analysis, building energy simulations, utility billing data, and short-term field measurements consistent with the International Performance Measurement and Verification Protocols (IPMVP).

The ex-ante gross savings are 5,645,055 kWh/yr and 2,482 kW. The ex-post net savings are 3,944,622 ± 225,177 kWh/yr and 2,142 ± 156 kW. The ex post net lifecycle savings are 58,498,564 ± 3,370,974 kWh. The net-to-gross ratio is 96 % indicating 4 % of the measures would have been purchased without incentives. The net realization rates are 0.70 ± 0.04 for kWh savings and 0.86 ± 0.06 for kW savings. The utilities haven’t previously conducted evaluations and were unfamiliar with tracking accomplishments and measuring results. Future evaluations should include the following requirements: tracking database, net savings including precision and error bounds, process evaluation, independent study management, adequate time, and evaluation contractors experienced with IPMVP measurement procedures. Chiller tower optimization is the most cost effective measure followed by EMS, VFD chiller, evaporative pre-cooler, thermal storage, AC tune-up, and high efficiency packaged AC. The average cost of conserved energy is $ 0.022/kWh and $ 619/kW. The program cost is $ 988,748 and the evaluation study cost is $ 46,456.

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