A Too-Smart Solution?

Aug. 1, 2007
The benefits of installing smart metering systems in the plight of utilities are clear, but implementation is complex.
By Dan Hebert, PE, Senior Technical Editor

The plight of utilities trying to install smart metering systems is familiar to those in process plants, who have tried to implement large-scale data integration projects. In both cases, the benefits are clear, but implementation is fiendishly complex.

Electric utilities need smart metering systems to mitigate peak loads, and reduce the amount of required electrical generating, transmission and distribution capacity. For decades, smart metering systems for residential utility customers were envisioned, but rarely implemented.

The original idea was perhaps too ambitious. Each residential customer would have his or her own smart meter that would measure power usage and would include high-speed, two-way communication with the utility’s command-and-control system. Residential customers would be informed of the real-time price of electricity via a digital readout device mounted inside the home. The utility would adjust this price upward or downward to control usage. Informed customers would willingly and actively cut their electricity usage at times of peak demand.

There are at least three problems with this vision. First is the huge expense of installing smart meters and digital readout devices at every residence. Second is the substantial cost of linking each meter back to a central command-and-control system via a high-speed data link. Third are the significant data-management challenges, which are especially acute since there is no common standard for data exchange among meter manufacturers and meter data management software firms. The final nails in the coffin of these meter-management schemes are the need for real-time pricing and the requirement for customers to react to changes in price.

But this is a classic case of simpler being better.
I recently signed up for a relatively “dumb” residential peak load-shaving program, and I have high hopes that the program will save me money and help my electric utility, Southern California Edison (SCE), trim peak demand in a cost effective manner.

According to Scott Hirth, a manager at SCE, the A/C cycling program allows SCE to temporarily turn off residential air conditioner compressors during Southern California power emergencies. Participation is strictly voluntary, and participants receive credits of up to $200 on their summer season electric bills.

SCE’s peak demand occurs during summer weekday afternoons, typically between 2 p.m. and 6 p.m. The company estimates that peak residential air conditioning demand is approximately 3,400 MW or about 16% of total summer weekday afternoon peak. So if SCE could get half of its customers to sign up for the A/C cycling program, it could cut peak demand by about 8%. About 240,000 or 12% of SCE’s residential customers are presently enrolled.

The beauty of this program lies in its simplicity. SCE just installs a small (8 h x 8 w x 3 d in.) radio-controlled contactor outdoors on or near the A/C compressor. The contactor is powered from the same 240-V AC source as the compressor itself. The contactor interrupts the 24-V DC on-off signal from the in-home thermostat to the compressor. The installation only takes about an hour, and the technician doesn’t need to enter the house.

Communications between SCE and the contactor are also simple. Instead of the two-way data link required by “smart” systems, all that is needed is a one-way, low-speed radio signal to the contactor. This VHF radio signal is transmitted to the contactors from SCE’s grid control center via radio towers placed throughout the utility’s service area.

Perhaps most important, required customer action is also simple. They don’t have to do anything because their A/C compressor is shut off automatically. The only drawback from the customer’s perspective is that the A/C compressor fan will keep running during contactor activation as long as indoor temperature remains above the thermostat set point.

The key lessons learned from this program are these: simplicity is a virtue; wireless works when it is applied in an undemanding application; and—the one applicable to many other arenas—technical types often become so enamored of elegant and all-encompassing smart solutions that they forget about much simpler and almost-as-effective “dumb” ones.