When President Obama and President Xi Jinping of China announced in November that they will commit to targets for carbon cuts, few thought changes would happen quickly. Less than two months later, Xiang Yang Institute (XYI) in Hubei, China and Focused Sun of Las Cruces, New Mexico, USA are partnering in the critical area of solar microgrids. Microgrids are small local electric grids for supplying energy to gated communities, shopping malls, eco-resorts and agricultural projects.
XYI Dean Jihong Chen says, “Focused Sun has squeezed the cost out of solar concentrators, the key part of the microgrid system that focuses sunlight. Together with thermal storage and Chinese turbogenerators, we can produce small power plants for microgrids.” Reflected solar energy heats mineral oil to the 300C temperatures needed by modern turbogenerators. Thermal storage holds the heat for a day or more, generating electricity day or night.
“The solar energy peak is at mid-day, but people need heat and electricity in the evening,” says MIT Prof. David Gordon Wilson, an expert on thermal storage and turbomachinery. Wilson believes thermal storage can power generators until the next day. “For microgrids in the 100 kW to 10 MW range, low cost solar concentrators and thermal storage combined with turbo generators make more sense than photovoltaic collectors and battery storage. Thermal storage is the key missing ingredient,” he says.
Four times more solar energy is captured by the concentrators than by conventional photovoltaic panels of the same size. During the day, solar energy is stored thermally. At night or during cloudy periods, the energy is pumped from storage to the turbogenerator where 20% of the energy is converted to electricity. The remaining 50% of the sun’s energy is available as heat for example for warming homes, hotel rooms and greenhouses.
The system produces both electricity and hot water and can pay for itself in as little as two years. The Focused Sun concentrators are made locally bringing local jobs plus cheap, clean energy. For every dollar spent, four times more solar energy is captured.
Dr. Amir Abtahi, Director of the Solar Laboratory at Florida Atlantic University (Boca Raton, FL) has investigated solar microgrids with thermal storage. He says, “The modular approach that Focused Sun uses lets solar energy be customized to various power plant sizes.”