Recently I had the chance to tour the Island of Alcatraz, once the site of one of America’s most famous prisons. The prison was closed in 1963 due to the high cost of maintenance in such a remote location, but it remains a top tourist destination.
My justification for this junket was an invitation from Princeton Power Systems, a smart inverter company based in Princeton, New Jersey, whose technology forms the backbone of a microgrid installed on Alcatraz with the help of federal government stimulus and which began operation earlier this year.
An inverter converts direct current (DC) from generation sources to alternating current (AC), at the voltage and frequency required by utility distribution companies (i.e., 60 hertz). Recent advances in inverters for solar photovoltaics (PV) and small wind turbines are setting the stage for a viable microgrid market to evolve. New inverters allow for safe islanding – i.e., the creation of small distribution systems cut off from the larger power grid. When connected to the larger grid, inverters enable distributed renewable resources, such as solar PV, to continue to operate when the larger grid goes down, thus avoiding the feeder fault concerns associated with synchronous generators, which may take 2, 5, or even 10 seconds to respond to a grid outage. (Pike Research’s new report, Inverters for Renewable Energy Applications, forecasts that the total inverter market will surpass $4 billion in global revenues by 2018.)
In the case of Alcatraz, access to Pacific Gas & Electric’s electric grid was severed several years ago when a ship’s anchor accidentally cut the transmission line from mainland San Francisco. As a result, diesel generators were installed to provide on-site power. However, as the price of diesel began to climb, and the cost of solar PV fell, developing a state-of-the-art microgrid appeared attractive.
On the day I visited, unfortunately, none of the nearly 1,000 highly efficient SunPower solar panels were working because a switch had failed. So the entire island was still running on diesel generation, with back-up being provided by banks of lead acid batteries. Of course, that’s the beauty of a microgrid: a diversity of resources can run together or serve as back-up to each other.
I learned a lot about the nitty-gritty issues of trying to build a microgrid on a windswept island. For one, construction of the microgrid was delayed several times due to regulations protecting bird breeding activities, which limited the use of light and sound during a three-week period. Along with these environmental factors come the quirks associated with preserving historical artifacts, which include rusting (and useless) water and fuel pipes as well as a hole in the roof.
The most persistent issue facing the microgrid, though, revolves around the birds. Though naturalists initially worried that the solar PV panels that cover the roof would scare away birds, gulls have actually found them quite appealing. In fact, they sometimes nest under the panels. Unfortunately, they tend to leave behind their waste, which degrades performance and requires an ongoing, and messy, maintenance task. Kept clean, the solar PV panels can meet the entire island’s power supply, even during San Francisco’s famous fog, which reduces potential output by more than half.
Beyond the Alcatraz project, Princeton Power Systems has three other microgrids up and running in San Diego, Texas and Missouri. The company offers 10 kilowatt and 100 kilowatt versions of its “DR Inverter,” which accepts four connections to and from power loads (two AC and two DC). The inverter is designed to sell stored solar energy into the burgeoning U.S. market for demand response revenue streams being authorized by grid operators in response to the Federal Energy Regulatory Commission’s Order 745. Funded in part by the Department of Energy, PPS’s technology aims to make solar PV more competitive by capturing new revenue streams. The firm was in San Francisco at the Intersolar North America conference to showcase this new commercial product.
Article by Peter Asmus, appearing courtesy the Matter Network.