Real World Applications for Microgrids

Borrego Springs makes an ideal candidate for microgrid development.
Published: Fri 12 Dec 2014

California’s clean energy goals and initiatives are major drivers for the development of microgrids, says Neal Bartek, Distributed Energy Resources Manager, San Diego Gas & Electric (SDG&E) who presented Real World Applications for Microgrids, at European Utility Week.

Driving forces behind microgrid development

He lists California’s most ambitious clean energy goals as follows:

  • Reduce GHG emissions to 1990 levels by 2020

  • Reach 33% Renewable Portfolio Standard by 2020 but this target will probably be reached by next year already (Since 2011, SDG&E has signed 36 renewable contracts totaling nearly 2,000MW.

  • Energy storage procurement targets – 1325MW capacity by 2020.

Some of California’s energy initiatives include:

  • California solar initiative

  • Net energy metering

  • Feed-in-Tariffs (SB32)

  • Low Carbon Fuel standard

  • Smart grid (SB17)

  • Distributed generation and demand response goals (AB2514 Skinner)

He explains that the goals and initiatives are major driving forces behind the development of microgrids in California.

Borrego Microgrid 2.0

The Borrego microgrid is one of SDG&E’s largest projects which was carried out jointly with the US Department of Energy (DOE) and the California Energy Commission (CEC). The project’s aim was to find out how the utility can integrate and leverage various distributed generation and storage configurations and help reduce the peak load of feeders and enhance system reliability. Another aim of the project is to enable customers to become more active participants in managing their energy consumption.

The budget for this project was US$8million from the DOE, US$2.8 million from CEC plus matching funds from SDG&E and partners. Borrego Springs in California was chosen as the project’s location since it enjoys extremely high temperatures. The area enjoys a high concentration of solar generation - there is already 1MW of customer-owned photovoltaic and in the last year, 26MW has been added to the transmission level and a further 5MW to distribution as a wholesale generation plant. Altogether there is about 32MW of PV. There is great concern over the high solar generation and what it will do to the grid. It is for this reason that the area was chosen since there is a potential for reliability enhancements and an opportunity to balance supply and demand to be more self-sufficient. Also, the area is fed by one transmission line which makes grid reliability questionable during major storms.

Two 1.8MW Caterpillar Diesel Generators were installed for the microgrid. These are owned and operated by SDG&E. Each generator is rated for 1.8MW at 480V. Emissions equipment was retrofitted onto generators.

One 500kW lithium-ion battery, manufactured by Saft, was also procured and assists with peak shaving, load following, renewable smoothing, and support islanding of operations in the area. Another three 25kW storage units, supplied by S&C and Kokam, have been connected to the circuit. These assist with peak shaving, renewable smoothing and voltage support. The units operate independently and as a fleet.

SDG&E also installed devices in the home so that consumers can manage their consumption more effectively. A demand response system was also installed to aggregate the load. The system provides a rolling 48 hour demand response capacity forecast capability.

Microgrid controllers provide a consolidated view and enables a more efficient control of microgrid resources.

Demonstrations that were carried out include:

  • Var control

  • 4-Quadrant Operation

  • Peak shave

  • Virtual island

“This was the first large scale utility microgrid in the US. We islanded real customer loads and provided advanced technologies for future applications. We have created an established microgrid model that can be used by other utilities.”

Real-world- Non demonstrations

Real world examples highlighted the real benefit of the microgrid:

  • In 2012, during a planned outage, the microgrid powered 2,128 customers for five and a half hours. This would normally have been an eight hour outage.
  • Planned islanding in 2013, SDG&E conducted seven islanding events over three days.

  • A huge desert windstorm in 2013 destroyed three transmission poles. But, the microgrid provides power to 1,225 customers for six hours while repairs were made to the transmission line.

  • A flashflood in 2013 saw three CES units island six customers for five and a half hours. These customers weren’t aware of the outage as the units connected back to the grid smoothly.

  • A massive storm in September 2013 took out nine transmission poles and 11 distribution poles. Restoration took almost three days and over 200 employees were involved. The microgrid was switched on and supplied power for 20 hours to 1056 customers during the outage.

“If you are building a microgrid for an entire load, a lot of money will have to be spent but if you can define your critical load to something which is only 10-15% of that load, then that is what you can build your business case on.”

Lessons learnt

Bartek points to a number of critical lessons:

  • Plan and test
  • Don’t underestimate the complexities of integration

  • Nascent technology will delay implementation

  • Partner vendors are essential when dealing with nascent technology

  • Early involvement and education of all impacted organizations is important

  • No substitute for field demonstrations

  • Siting equipment and permitting are challenging

  • DER, if done correctly, can have a positive effect on the grid

  • Can no longer have IT and engineering silos. Blended skills and working closely together is what is needed now

“The aim now is to further enhance the Borrego Springs microgrid so that it is more flexible and automated in responding to a variety of potential outage situations, and leverage various new technologies and distributed energy resources for increased microgrid capabilities.”