SoCalEd DR Demo Finds Resource

Southern California Edison (SCE) ran a DR pilot project last summer to show it can take part in the California ISO's non-spinning reserve ancillary-services market. A similar PG&E pilot (SGT, Jan-13 5 kw -- to prove its point.) focused on three high-load commercial consumers but SCE's used 3,255 air conditioners -- mostly in homes and each using less than

Predicting the amount of power that can be shed by a utility-controlled curtailment is harder with many small devices than with a few large ones, Larry Oliva, SCE's director of tariff programs and services, told us Tuesday. Still, “overall, the pilot worked out very well,” he said.

SCE already had a DR program in place with 350,000 air conditioners, all but 10,000 of them in homes. But it had not sold the DR into the market before. The pilot used a subset of those 350,000 air conditioners to determine whether it could do so.

It recruited 3,255 homes at Ft Irwin, northeast of Barstow, Calif, since summer temperatures there are consistent and all the customers are served by a single substation, Oliva said. All the test homes' air conditioning compressors -- though not their fans -- were controllable by the utility, using the Alhambra Control System of one-way, VHF-controlled cycling switches, SCE said in its feasibility report on the pilot.

The California ISO (CAISO) requires that participants in its non-spinning reserve ancillary-services market be able to show available load within four seconds and be capable of five-minute metering intervals. But even the smart meters SCE is installing can offer data only every 15 minutes. To satisfy the requirement, SCE and its contractor, KEMA, in May installed telemetry equipment from BPL Global at 555 of the 3,255 test homes, Oliva said.

BPL Global's Power SG equipment uses a wireless mesh network, with each endpoint load sensor communicating to a data collector via 2.4 GHz radio over a line-of-sight range up to 600 feet. Each collector supports up to 5,000 endpoint sensors and uses a GPRS modem to connect to a commercial cellular network.

KEMA helped SCE extrapolate from the 555 telemetry-equipped homes the total air conditioner load from the 3,255 homes taking part in the pilot. That data was fed to CAISO and the ISO in July said the system was good enough to let SCE bid into the market. The pilot's total air conditioning load was about 5 mw.

SCE also used SCADA equipment -- that delivers load data within three seconds -- at the substation serving the test homes. Indoor temperature sensors were used to assess the cuts' impact on customers but were not involved in monitoring or dispatching power.

From June through October, SCE conducted 32 tests, each time for periods of 5, 10, 15 or 20 minutes. It measured loads at participating houses before and during the tests. Of those 32 tests, 12 were coordinated with CAISO and were bid into its day-ahead market. At the appointed moment, SCE turned off all 3,255 air conditioners “basically by pushing a button,” Oliva reported.

“The pilot was successful, in that we could measure with accuracy the load reductions we expected,” he said. “We were able to bid into the California market for ancillary services successfully with this equipment.”

Participating homes warmed by an average of less than 1°F even during a 20-minute compressor outage, showing “you can do this kind of program and not affect the comfort of the residents,” Oliva said. Ft Irwin got $100 for each of the switchable air conditioners taking part.

The experience also taught SCE a few important lessons, Oliva said.

Each bid required three days' preparation including a number of manual steps. Many of the pilot's power-dispatch procedures were manual and that created “some challenges and delays,” SCE wrote in its report. For example, phone calls among various offices at CAISO and SCE sometimes crossed or were delayed by other matters or by multiple calls arriving simultaneously.

Both the bidding and dispatch processes “will require significant development and automation to support any potential future programs,” SCE wrote. Specifically, it said, automation should be used to:

• Tell all parties when a DR bid has been submitted, accepted and dispatched;

• Process data on weather and historical loads for submission to the utility's scheduling system;

• Track the acceptance or rejection of bids by CAISO;

• Monitor loads before bids are made, tell the utility of deviations from expected loads and adjust bids to reflect load changes;

• Initiate dispatch, then maintain and end the curtailment, and

• Collect settlement data.

Though SCE proved it can take part in the ancillary-services market, “the challenge is whether it makes economic sense to install the equipment to do that on a large scale,” Oliva said. Once smart meters are in place throughout the utility's service area, it will be able to measure load cuts, letting it take part in the less equipment-intensive proxy demand resource program that CAISO is planning. To date, 175,000 smart meters have been installed in CSE's 50,000-square-mile service area.

“The pilot gave us and CAISO some comfort that this resource is real and accountable,” Oliva said. “So while it may not be appropriate for the ancillary-services market, we do know that the resource is viable for a market requiring less granular information.”

This story has been reproduced from the January 14, 2010 issue of Smart Grid Today with the permission  of the publisher, MMI Inc. To view the full story on Smart Grid Today’s website, please visit http://www.smartgridtoday.com/public/1138.cfm?sd=31.