Island of opportunity: Microgrid technology comes to the Bay Area

Microgrid technology is an attractive way for military bases, schools, jails, and other electricity customers to pursue energy efficiency and clean energy in tandem. One of the most unique functions of microgridsis their ability to island, or operate autonomously and separated from the larger macrogrid. Indeed, the official U.S. Department of Energy definition of microgrids emphasizes the importance of islanding functionality, saying: “[a microgrid is] a group of interconnected loads and distributed energy resources within clearly defined electrical boundaries that acts as a single controllable entity with respect to the grid [and can] connect and disconnect from the grid to enable it to operate in both grid-connected or island-mode.”

One microgrid islanding success story is that of the Sendai microgrid in Japan. When the devastating Tohoku earthquake hit the Sendai region in March 2011, its microgrid continued to provide reliable power to a number of loads, including a hospital, for two days while the larger macrogrid halted power supply. The chief engineer for the Sendai project, Keiichi Hirose of NTT Facilities, visited LBL on March 23 to give a talk on the microgrid development to date and operation during the earthquake period. According to Hirose, the Sendai microgrid project features a fuel cell, solar PV, batteries, and two natural gas-fired microturbines for a total peak output of 1 megawatt, all of which worked in unison in the aftermath of the disaster.

On March 22 this year, a local microgrid project officially launched at the Santa Rita Jail in Dublin, just 30 miles east of Berkeley. Power reliability is a primary concern for the jail, which houses about 4,000 inmates. Over the past ten years, the project has slowly been coming to fruition as various power supply technologies and energy efficiency measures have been installed and implemented. The jail has over 1 megawatt of installed solar PV capacity, featuring both rooftop installations and ground-mounted tracking installations, as seen in the photo below.

The jail also has a fuel cell and two back-up diesel generators, and its most recent addition was a 2 megawatt battery. The combination of these technologies allows the jail to significantly reduce its daily purchases from the macrogrid (saving the jail about $100,000 a year) and to operate as an island in the event of a power supply disruption. A switch detects when no voltage is coming from the macrogrid and immediately disconnects the jail from the grid. Simultanously, microgrid controls allow the jail’s suite of backup supply and storage technologies to provide uninterrupted full power to the jail. The jail consulted with Lawrence Berkeley Lab (LBL) a number of times throughout the development of the microgrid, using the lab’s DER-CAM (Distributed Energy Resources-Customer Adoption Model) software to analyze electricity and heat requirements and develop a plan for the jail to meet its needs at minimum cost.

Both the Sendai and Santa Rita microgrid projects benefited from public funding. The Sendai project received funds from Japan’s New Energy and Industrial Technology Development Organization, and the Santa Rita project received funds from the Department of Energy and California Energy Commission. Indeed, microgrid investment costs are still relatively high for many commercial building customers. However, customers with high reliability demands, such as military bases and tactical operations centers, are actively pursuing microgrid solutions (such as the SPIDERS project). As successful experiences accumulate and costs come down, opportunities for other customer applications will arise. Maybe, one day, we’ll all be on the island.