Jan 06 2010

The Power of Numbers

Posted by: Jonathan Marshall

They say there's power in numbers. Well, PG&E has just proven that the cliche is literally true.

With the help of two thousand customers who participated in an experiment this summer, the utility has shown that voluntary reductions in electricity use, particularly for air conditioning, can reliably replace expensive and polluting peak power generators for balancing supply and demand on the electric grid.

As described previously in NEXT100, this pilot test of the utility's ability to work with customers to shape their demand in a timely and predictable fashion addressed what the chairman of the Federal Energy Regulatory Commission has called "the 'killer application' for the smart grid."

Programs to reduce peak loads can save money (by avoiding the need for generators that sit idle most of the year), reduce the risk of system overloads and cut down on air pollution, including greenhouse gas emissions.

Equally important, utilities could use such programs to support the integration of more renewable resources, by synchronizing demand with the fluctuations of wind and solar energy.

PG&E's voluntary SmartAC program provides customers with free radio-controlled thermostats or on-off switches that can be directed to turn down air conditioners during periods of peak energy demand, usually without sacrificing customers' comfort.

Until now, however, operators of the state grid could not be confident that the program would deliver load reductions quickly or reliably enough to replace traditional peak generation.

Working with Lawrence Berkeley National Laboratory this summer, PG&E recruited 2,000 SmartAC customers in Antioch, Fairfield and Fresno for a test.

PG&E also invested in sophisticated telemetry infrastructure to monitor, in near real-time, the impact of air conditioner controls on system loads. This was a critical addition to the SmartAC program, needed to prove its true value as a resource for balancing supply and demand.

Among the test customers, PG&E turned down their air conditioners for 15 minutes twice each weekday during the months of August and September--a total of 71 times.

The results were significant: "the average load reduction per device across all events was 0.65 [kilowatt] per device." That may not sound like much--but if extended across all 135,000 SmartAC-controlled devices, the program could replace as much as 80 MW of generation on most summer days, and up to 180 MW of generation during system peaks (equivalent to about two peak power plants).

Equally important, the pilot proved that the load reductions could be fast and reliable enough to meet the demanding requirements of state grid operators who must balance supply and demand.

Last but not least, despite the repeated curtailment of their air conditioning, almost nine in ten customers who took part in the pilot were satisfied with PG&E and only 17 percent even noticed that their air conditioning was affected.

The potential environmental and economic implications are huge.

As Reuters columnist John Kemp noted recently, if the California electric grid "could reduce demand on just the 2 percent of peak hours each year, it could avoid . . . the need to maintain more than 5,000 MW of idle [generating] capacity. [That] explains why demand response strategies designed to curb power use at peak periods have become one of the highest priorities for governments and system engineers on both sides of the Atlantic."

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