Solar Thrives in New England

Is it sunny enough in New England to reliably and economically sustain solar power?  While we do have hot and sunny summers with what seems like long days, summer is over before we know it and our winters have much shorter days, a lot of snow, ice and sleet, and a lot of clouds.  How does our climate compare with the south and the southwest for sunny days and its compatibility with solar power?

The technical term for measuring solar capacity is solar irradiance, which is a measure of how much solar power you get at a particular location.  Solar insolation is the amount of solar energy or solar irradiance hitting the earth’s surface as measured in kilowatt-hours per meter-square per day, or per month, or other periods of time.  The success of any solar power installation, large or small, depends on the degree of solar insolation at a particular location.  The solar array area and system efficiency are constant values, which means that the only variable factor is solar insolation. Two identical PV systems will have a different output if installed on locations with different solar insolation rates.

You may be surprised to learn that much of New England has a similar amount of “insolation” as Texas.  The US Department of Energy’s National Renewable Energy Lab, or NREL, in conjunction with the National Aeronautics and Space Administration, the Northeast Climate Center, and a number of universities and companies have collaborated to create a database of solar radiation and worldwide insolation data that is of use to solar developers and others.  As a recent article by the Union of Concerned Scientists pointed out, despite being a northern state, Maine has much better solar resources than we might expect.  According to data from NREL, a solar photovoltaic, or PV, system installed in Portland, Maine will generate slightly more electricity than a system installed in Houston and only five percent less than a system installed in Miami.

Insolation levels change throughout the year, lowest in winter and the highest in summer. Close to the equator, the difference throughout the year is minimal whereas at higher latitudes winter can be a fraction of summer levels.  It is also true, however, that solar modules actually operate better in colder weather and are relatively unaffected by snow. The panels are installed at an angle, which is necessary to catch the sun’s radiation and also helps prevent snow collection on the array. If snow does collect, it typically melts quickly.

According to the Independent System Operator for New England, winter does impose the most variation in solar output because of snow, clouds, and shortened daylight hours, but it certainly helps reduce demand on our electrical grid during sunny days in warmer months, the time when our electricity usage peaks because of the air conditioning demand.  As battery storage systems improve and become more economic that will help to manage the variation in solar power produced between winter and summer months.

About the Author: Douglas L. Patch

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