Microgrids have become a hot topic in industry news describing installations popping up across the country, particularly at universities and on military bases.  The Solar Electric Power Association, whose mission is to support utility integration of solar, held a webinar on July 31 profiling two microgrids in San Diego Gas & Electric’s service territory.  One is the microgrid at Borrego Springs built by the utility. The other has been built by the University of San Diego on its campus.


Beginning in 2000, Byron Washom, director of strategic energy initiatives at UC San Diego, and his colleagues built a 40-MW microgrid system that now provides power for 90% of the campus. Peak demand is 42 MW on the 1,200 acre campus that hosts a daily population of 45,000 studies, faculty and researchers.

Washom described the various components of the microgrid: Two Solar combined-cycle gas-fired turbines produce 25 MW and 3 MW of Dresser Rand steam turbines produce 120,000 lbs./hour of steam for heat recovery. The waste heat flows into the district heating system to provide 95% of the campus’s heating and cooling. There are three steam-driven chillers and eight electric-driven chillers.

Two megawatts of photovoltaic solar systems include a Soitec concentrating PV solar system which is 27% efficient, Washom said, and a Kyosera system rated at 14% efficiency. Moreover, the campus has invested $4 million in solar forecasting.  A fish eye camera scans the sky and takes pictures every 30 seconds, allowing staff to forecast solar power availability.  He said the ground-based system is more accurate, since a satellite-based system is less accurate due to the slow delivery of data.

Lyn Corum

A 3.8-million gallon thermal storage system, installed in 2000, creates ice at night and cools the campus during the daylight hours.

A 2.8-MW fuel cell system, manufactured by FuelCell Energy, began operating in January 2012.  It burns biogas generated at the Pt. Loma waste water treatment plant 17 miles away. “We purify the methane to inject it into SDG&E’s gas lines” he said, and UCSD receives renewable credits.

Washom said the fuel cell plant is working well and supplies 10% of the campus electrical base load. The campus is installing an absorption chiller to use the fuel cell’s waste heat.

A 2.5-MW energy storage system is scheduled to be installed by December 2014. Washom emphasized this is not a demonstration. “It is an early commercial system and we want to illustrate the flexibility of different solar electricity strategies,” he said.  A 1.3 MW/2.6 MWH PV integrated storage system was installed in 2012.

Washom said Power Analytics monitors and manages the high volume of data generated by the microgrid control systems – 90,000 data points/second, he said. The microgrid is tied into SDG&E’s grid and the California Independent System Operator has the ability to observe its operational system. “We think this will increase incorporation and development of microgrids in the wider transmission system, he said.

Washom said they are also looking at PMUs, or phasor measurement units, which use GPS systems to monitor the phases of all the voltages and currents throughout a grid in real time. “If we had PMUs at the time of the September 2011 regional blackout in Southern California we would have detected the problem ten minutes ahead of time” and islanded our system.  “We didn’t and the microgrid collapsed with the grid.  We had to black-start the system,” he said. The physical plant has 75 diesel generators for just such an emergency.


San Diego Gas & Electric created a microgrid in the desert community of Borrego Springs with $10.8 million in funding from the US Department of Energy and the California Energy Commission. The community, with 2,500 customers of whom 300 are commercial, is located in the middle of a state park in the southeastern corner of the state. Borrego Spring is surrounded by mountains and is beset with flash floods during monsoon season. Since it is at the end of a 69-kV transmission line the flooding often cuts off electricity service for hours at a time.

Tom Bialek, SDG&E’s chief engineer, said during the SEPA webcast, the community is progressive-minded and there is a high concentration of roof-top solar. Advanced metering is fully deployed in the town. Therefore, residents and businesses can reconfigure their energy management systems to island their homes or business space during emergencies.

SDG&E installed two .1.8-MW diesel generators with selective catalytic reduction units and one 500-kW/1,500 kWh battery. A community energy storage system consists of three 25 kW/50 kWh lithium ion batteries.

In a September 2013 flood the microgrid supplied power to 1,056 customers for up to 20 hours, in essence islanding the community from SDG&E’s grid.

Bialek said it took 25 hours to restore power because of the devastation to distribution line poles. Customers with solar panels on their roofs did not see the outage. In an earlier wind storm in April 2013, the microgrid was able to provide power to 1,225 customers for six hours.

SDG&E is continuing to upgrade the technologies, and is planning to charge the energy storage batteries with solar power.

Bialek said all power electronics are housed below ground. The batteries are warrantied for 40 degrees centigrade but temperatures in the area can reach as high as 50 degrees, so air-conditioning is needed in the buildings housing the electronics.


Recall that in March of this year, the California Public Utilities Commission authorized SDG&E and Southern California Edison to procure additional local power resources to make up for the June 2013 retirement of the San Onofre Nuclear Generating Station? (If not, see my column in the May/June issue.)

SDG&E is to procure between 500 and 800 MW in San Diego’s “local reliability area.” It is quietly moving forward with contracts to fulfill this requirements and submitted an application to the CPUC on July 21 requesting approval for a power purchase tolling agreement with NRG Energy to purchase the 600 MW of capacity from the Carlsbad Energy Center in Carlsbad, California. The CPUC will decide on SDG&E’s application perhaps as late as the end of the year.

NRG has been developing the Carlsbad Energy Center since 2007 when it applied for certification at the California Energy Commission. It didn’t receive a permit to construct until 2012, due largely to city and community resistance, but without a power purchase agreement the development was stalled.  SDG&E expressed no interest in a contract with the plant until SONGS shut down. 

In May, 2014, NRG asked the CEC to amend its certification and allow it to install fast start, simple cycle peaking generation instead of the combined cycle units it originally intended to install.  The CEC has not published a schedule for its review but it may take as long as a year. NRG is likely hoping the review will be much shorter.

The new facility will consist of six generating units utilizing GE LMS100 turbine technology. The plant’s flexibility will give it the capability to start and stop multiple times per day. This will allow SDG&E to accommodate the variable and intermittent solar and wind projects being added to its system, and hence the utility’s new interest in signing a contract with NRG.

Bringing the Carlsbad plant online by November 2017, as currently scheduled, will allow the old Encina power plant next door to be razed and its once-through cooling system  to be removed by the December 31, 2017 deadline as ordered by the State Water Resources Control Board.

The new Carlsbad power plant has finally won the support of the City of Carlsbad which put up a vociferous (and losing) fight over the original development. The agreement with the city includes turning over land currently occupied by the Encina plant to the city for recreational development.  The new plant will also have a lower profile.

In a second request filed in May 2014, SDG&E sought approval at the CPUC for an amendment of a contract with a qualifying facility, Oceanside Refrigeration, Inc., owned by Goal Line, L.P. The 49.9-MW cogeneration facility in Escondido has been selling firm power to SDG&E since February 1995. The original standard offer contract, as well as the amendment, will expire in February 2025.

The amendment will convert Oceanside Refrigeration to a prescheduled facility, allowing SDG&E to schedule the plant rather than being required to accept firm power, even at times it isn’t needed, according to SDG&E.

The facility is federally certified as a qualifying cogeneration facility but will operate as an exempt wholesale generator once this amendment is approved by the CPUC. SDG&E will be the scheduling coordinator and will supply the fuel required to run the cogeneration plant.

SCE also got into the act. It announced on August 1 it signed contracts with solar and geothermal energy producers representing more than 1,500 megawatts of clean, renewable power. Signed contracts include the purchase of more than 1,300 megawatts of new solar power and the re-contracting of 225 MW with Calpine subsidiary, Geysers Power Company. The contracts need to be approved by the CPUC and resulted from a solicitation for renewable power last year.

The largest number of solar contracts were signed with 8Minute Energy (three totaling 457 MW) and Silver Ridge Power (two totaling 406 MW). Following up are Recurrent Energy with one contract totaling 206 MW, Panoche Valley Solar for 247 MW and Copper Mountain Solar, 94 MW.