Monday, December 21, 2009

Solstice sun

21 Dec 2009: Well Dec 20/21 are both Sunny Days! A great time to calibrate the roof performance. Dec 20 had a short period of cloud which modified the PV harvest to 3.99 when it should have gone over 4.0.

Sunrise in Nottingham is 0816 on Dec 20/21, but the annoying thing about living in the shadow of Sharp Hill is the late sunrise in Winter. I watched the sun rise, but Peveril-sunrise didnt happen until 0918, 62 mins after the real sunrise. We get daylight in the mornings, but can only sense sunlight in the sky, but not see it on us!

GAISMA seems to be a really good site, with predictions for sun angles and declination, both in tables and in good diagrams. Plus info on insolation, wind and temperature. (the word means 'light' in Latvian)

By 0925, when the sun has fully cleared the hill, the roof is generating 310W, and by 1018, an hour after Peveril-Sunrise, its getting 1240W. We pass our peak at about 1030, so at 1118 the power was 1120W..... at 1200 was 800W.... and from now it's downhill for the rest of the day :(

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