The Solar Solstice

Living in Minnesota, the winter months can be trying on many levels. Cold temperatures, slippery roads, ice dams, the list goes on. And to add insult to injury, it seems as if we only get about four hours of sunlight each day.

With the winter solstice upon us – and with it the shortest day of the year – my thoughts turned to the power of the sun. Specifically, during this cold, dark time, it would seem that solar energy generation would be non-existent. For those looking for a little heat, the logical answer would be to head south – the same way flocks of northern “snow birds” migrate to warmer climes each year.

But before I pick up and leave, I thought I’d try to find just how much solar energy can be expected in northern climates during the colder months?

While it’s no surprise that the cold winter months offer the least amount of solar radiation (kWh/m2/day) in northern climates, what may be surprising is the amount of solar energy actually produced during that time. Using Minneapolis as my sample location, solar efficiency during January (3.85) and February (4.72) only decreases about 20% – as compared to the average high of 5.91 kWh/m2/day in June.

For a little perspective, Tampa, Fla. achieves a between 4.5 and 5.2 kWh/m2/day in January and February.

Not bad for the nation’s ice box.

If you’re thinking about solar for your home or business, or if you’re just interested in a tutorial on solar energy data– I’d recommend a visit the National Renewable Energy Laboratory’s PVWatts grid calculator page. You’ll have access to more information than you’ll ever need regarding solar energy. It’s a great resource to help determine what kind of cost- and energy-savings you can realize with PV solar panels. The tool allows users to create estimated performance data for any location in the United States by selecting a site on a 40-km gridded map.

Hopefully you’ll see that for all of us braving the cold – and the dark – this winter solstice, solar energy is a viable option any time of year. And while we may not hold a candle to the sunbelt in winter, it’s nice to know not all is lost.

Article by Tim Laughlin, appearing courtesy Xcel Energy Blog.

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