Calc solar energy energy by date and location?

[davepl]

I've been tinkering with a 55W panel and today (first somewhat sunny day!) I saw a peak of 2.7A @ 14.5V, or 39W. But I'm up in Seattle, it's March, and it was 1:30PM, so its hard to say if 39W is a lot or not.

I presume that the 55W is the theoretical max at noon on the equator, so I'm wondering if there's a table or online calculator that will tell me for a given day and lattitude and time what the max theoretical available solar energy is, let's say at sea level for simplification.

I've seen the USGS solar maps, but they take into account annual averages, whereas I want date/time/location peaks.

Any thoughts?

[russ]

Hi Dave - Don't know where you will get date/time/location peaks - Some weather station site may have a pyranometer and show that information. There are several - Davis Weather has one, Weather Underground another

The 55 watts is the STC (standard test condition) rating based on 1000 watts/m2 insolation and a number that most places may see for one hour per year - or on a cloudy day when the readings are upset. For example the highest reading I saw today (hourly average) was 819 watts/m2 and yesterday was 851 watts/m2 - The rest of the hourly readings were all lower. Both of those even probably had some 'cloud effect'.

Look at these for more information - might find something useful -

1) PV System General Sizing Instructions Sandia http://photovoltaics.sandia.gov/docs/Wkshts1-5.html

2) http://www.ambientweather.com/gedbtu1300.html

3) http://www.ambientweather.com/gedbtu1300.html

Russ

[Sunking]

(first somewhat sunny day!) But I'm up in Seattle, Any thoughts?

Sun in Seattle. I bet you guys freaked out and had people jumping out of buildings thinking the world came to an end.