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Thermal Energy Storage: Putting Green Solutions on Site

Fortnightly Magazine - August 1996

for its "Energy Star" programs, such as Green Lights. This program has committed a number of business partners in California to installing high-efficiency lighting in 90 percent

of their floor space over a 5-year period when the internal rate of return exceeds 20 percent. California could develop a "Competitive Electricity Environmental Partnership" program for TES modeled along the same lines. Such a partnership would position California businesses to benefit from a competitive electricity market and help clean the air as well. Alternatively, perhaps TES could be included as a priority cooling technology in the second phase of the Energy Star program (em which moves from lighting to heating and air-conditioning system improvements.

TES is now poised for full

commercialization. Institutional policies, such as those identified above, should be pursued to increase TES's market penetration. t

John E. Flory is principal in charge of the Western Division of Tabors Caramanis and Associates and lead author of the TES Collaborative's report, Source Energy and Environmental Impacts of Thermal Energy Storage. Loren W. McCannon is the founder and president of the International Thermal Storage Advisory Council and editor of the Council's newsletter. Until recently, Stan Tory managed the Thermal Energy Storage Program for PG&E and represented the utility within the Collaborative. Donald L. Geistert represented SCE's interests with the TES Collaborative, as SCE's lead TES engineer. James Patterson is an associate energy specialist with the California Energy Commission. He coordinates the TES Collaborative and researches other new technologies.

1. The "incremental energy" method applies the state's official method (as used by the California Public Utilities Commission, CEC, and utilities) for marginal-cost calculations and resource planning (including demand-side management programs such as TES) to the state's official guidelines for source energy analysis to develop time-differentiated source energy impacts. These impacts allow the determination of source energy savings by shifting electricity usage from day to night with TES. For more details see the report, Source Energy and Environmental Impact of Thermal Energy Storage.

2. The "marginal plant" method is similar to the state's official method with one exception. It has a different way of computing marginal-source fuel use in different time periods.

3. The method used in this study assumes that TES is operated under conventional time-of-use (TOU) rates. Some studies have found that thermal storage, operating with intelligent control systems under hourly varying real-time pricing (RTP), almost doubles the utility's marginal energy cost savings (and presumably source energy savings) as compared to thermal storage operating under conventional TOU rates. (See, B. Darayanian, L. K. Norford, and R.D. Tabors, ORTP Based Energy Management Systems: Monitoring, Communication, and Control Requirements for Buildings under Real-Time Pricing." ASHRAE Transactions 1992, V.98, Pt.1) (American Society of Heating, Refrigeration, and Air Conditioning Engineers). The CPUC recommends RTP as the dominant pricing in a competitive or restructured electric power industry. Therefore, the source energy savings of TES under the increasingly more common RTP could be significantly higher than the source energy savings reported here.

4. An interest Pacific Gas & Electric Study, "Offpeak Cooling Market Potential Study, conservatively estimates 20 percent as an