SMALL SUN CAN BE BIG

DOE: Big Utilities Can Get Reliable Power from Small Solar PV Arrays
Sara Stroud, September 28, 2010 (SolveClimate via Reuters)

"Massive utility-scale solar projects under development in the deserts of California and the Southwest have been in the spotlight in recent months as they win slow approval from state and federal regulators. But a study released in September by the U.S. Department of Energy’s Lawrence Berkeley National Laboratory found that smaller solar photovoltaic (PV) installations may collectively offer similar promise for increasing the amount of renewable power on the grid.

"Traditionally, the reliability of small PV systems’ power output has been a concern for utilities, project developers and grid operators, since all it takes is a few clouds to disrupt the power flow of a small array. But [ Implications of Wide-Area Geographic Diversity for Short-Term Variability of Solar Power by Andrew Mills and Ryan Wiser] suggests that when PV plant arrays are spread out over a geographic area, the variability in power output is largely eliminated…This means that for utilities, the distributed generation of small PV arrays could mean increased efficiency, reduced costs and a quicker path to a cleaner energy portfolio."

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"…The power output of a PV plant can fluctuate more than 70 percent in less than 10 minutes on a partly cloudy day, according to the report. That makes it difficult for grid operators to maintain a balance between power generation and demands…Following the model set by wind energy…the LBL study looked at synchronized solar data from 23 sites in Oklahoma and Kansas located between 20 kilometers and 440 km apart. It found that variability of solar output [for sites 20 km apart] was six times less than that of a single site…[and at] sites that were 50 km apart, the variability of solar was virtually identical to that of wind over time scales of five minutes to 15 minutes…"

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"The report’s findings could also have implications for the cost of managing the integration of more solar power into utility grids by lessening the need for energy storage…Geographic diversity reduces [variability and] costs of generation…For utilities, especially those that are required to meet state renewable portfolio standards, figuring out how to integrate renewable power into the grid…and understanding how siting projects will affect output is critical…

"In California, where utilities are required to get 33 percent of their power from renewables by 2020, a lot of PV growth has come from utility programs…While many of those are large-scale centralized projects, two of the state’s biggest utilities have launched widespread distributed generation initiatives that are expected to produce more than 1,000 megawatts (MW) through rooftop and ground-mounted PV arrays…[I]n early 2010 the New York Power Authority launched an initiative to deploy 100 MW worth of rooftop and ground-mounted solar installations across the state…"