My Telegraph column today is a bit of a grab-bag about solar power. In it, I say that I’ll explain a couple of items here, that I didn’t have room for in print. So here goes:
I calculated the efficiency of the 51.3-kilowatt solar installation on the roof of PSNH’s headquarters in Manchester because it is connected to FatSpaniel software, which provides remote access to data about solar power production. (Here’s the site - play with it yourself!)
1. From the start of August 2009 (it wasn’t online for all of July) through the end of March 2010, we find a total generation of 26,227 kilowatt-hours. Those 8 months had 243 days or 243*24=5,832 hours. So on average, the solar array was continuously producing 26,227/5,832 = 4.5 kilowatts of power, or a bit under 9 percent of its theoretical maximum output.
Of course, this was the worst half of the year: In all of December it generated a feeble 650 kilowatt-hours. In August it generated 11 times as much power.
If nothing else, this quickie calculation shows why utility folks, who are used to coal/gas/nuclear plants that generate 80 to 90 percent of their rated power every hour of the year, aren’t too impressed by solar and wind power.
2. One of the interesting facets about the participants in the state’s “net metering” program, which allows homes to sell power from alternative-energy systems back to the utilities, is how small wind is faltering.
There are 265 photovoltaic installations with an installed capacity of 787 kilowatts, compared to 35 small-wind operations. Further, wind is fading (so to speak): In the few half year of the program, roughly 20 percent of applications were from home turbines; how it’s down to about 13 percent. I suspect this is a sign that people are realizing small (under 5 kilowatt) wind turbines are very hard to position correctly; they can very easily be duds.
Massachusetts, I was told by an official there, has seen the same thing; the only wind power that’s succeeding there involves units of 100 kw or more, located near the coast. New Hampshire, obviously, doesn’t have much coast (18 miles is the usual figure).