UC San Diego Researchers Create Tool to Put the Lid on Solar Power Fluctuations

[OKIsItJustMe]

http://ucsdnews.ucsd.edu/newsrel/science/2011_06pv_variability.asp

UC San Diego Researchers Create Tool to Put the Lid on Solar Power Fluctuations

June 21, 2011

By Ioana Patringenaru

How does the power output from solar panels fluctuate when the clouds roll in? And can researchers predict these fluctuations? UC San Diego Professor Jan Kleissl and Matthew Lave, a Ph.D. student in the Department of Mechanical and Aerospace Engineering at the Jacobs School, have found the answer to these questions. They also have developed a software program that allows power grid managers to easily predict fluctuations in the solar grid caused by changes in the cloud cover. The program uses a solar variability law Lave discovered.

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The variability in the output of photovoltaic power systems has long been a source of great concern for utility operators worldwide. But Kleissl and Lave found that variability for large photovoltaic systems is much smaller than previously thought. It also can be modeled accurately, and easily, based on measurements from just a single weather station. Kleissl presented the paper, titled ‘Modeling Solar Variability Effects on Power Plants,’ this week at the National Renewable Energy Laboratory in Golden, Colo.

His findings are based on analysis of one year’s worth of data from the UC San Diego solar grid—the most monitored grid in the nation, with 16 weather stations and 5,900 solar panels totaling 1.2 megawatts in output. Lave looked at variations in the amount of solar radiation the weather stations were receiving for intervals as short as a second. The amount of radiation correlates with the amount of power the panels produce.

Output from the UC San Diego photovoltaic variability tool during a period of high variability in solar radiation (black line). A 1.2 megawatt central station photovoltaic plant (green) reduces variability, but the variability is even smaller for a 1.2 megawatt distributed photovoltaic system (red). The output is shown in relative units to facilitate comparison.

Based on these observations, he found that when the distance between weather stations is divided by the time frame for the change in power output, a solar variability law ensues. This operation was inspired by a presentation by Clean Power Research, a Napa-based company, at the Department of Energy – California Public Utility Commission High Penetration Solar forum hosted by UC San Diego in March 2011. “For any pair of stations at any time horizon, this variability law is applicable” says Lave. In other words, the law can be applied to any configuration of photovoltaic systems on an electric grid to quantify the system’s variability for any given time frame.

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The model development was sponsored by DOE’s High PV Penetration Program grant 10DE-EE002055. Further information is available at https://solarhighpen.energy.gov/project/university_of_california_san_diego and http://solar.ucsd.edu

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[Gregorian]

1. It's a simple observation, but the real world practice is going to take some real effort.

This is going to be the new grid. Lots of little grids. I don't see this as being a very big deal. But the transition from what we have to what we need is a very difficult one. I wonder how it'll be done. Maybe we'll parallel up lines on existing poles?

[OKIsItJustMe]

2. There’s no particular need to "parallel up lines"

The current “dumb” grid already deals with multiple sources and multiple consumers.