Drew, Aside from getting the weather data for weather-adjusted performance calcs, you might also note to your client that the excessive snowfall has skewed performance even further. One of our projects just outside of NYC had a pyranometer that would be clear of snow the day after a storm and therefore showing say 400 or 500 watts/sq meter irradiance at the site. Meanwhile there was a foot of snow on the array! I suppose we should move the pyranometer down to the module height so that it doesn't clear of snow any sooner than the modules.
It might also be comforting to point out that a 10 degree pitched system in Newark NJ could be down 100% in January and that's still only 5% for the year. If it starts snowing in July, then we have more problems than lost PV production. David Buckner Solar Energy Systems www.solaresystems.com<http://www.solaresystems.com> ________________________________ From: [email protected] [[email protected]] On Behalf Of Andrew Truitt [[email protected]] Sent: Wednesday, March 03, 2010 10:35 AM To: RE-wrenches Subject: [RE-wrenches] Irradiance data Is anyone aware of a resource for finding local historical irradiance data? We've had a cloudy winter around the DC Metro area and I would like to quantify how far down we are from the average for new customers concerned with production. Thanks in advance, Drew -- "Don't get me wrong: I love nuclear energy! It's just that I prefer fusion to fission. And it just so happens that there's an enormous fusion reactor safely banked a few million miles from us. It delivers more than we could ever use in just about 8 minutes. And it's wireless!" ~William McDonough
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