sun/light forcast

katie · Post by **katie** » 03 Sep 2010, 18:36

I've been watching the weather forcast for my part of the UK to try and work out when is the best time for sunlight to produce the energy to do the laundry, use the dishwasher, oven etc. with my new PV solar system. Is there a site, which can let me know when it's going to be bright/sunny/cloudy or do I just go with the weather forcast. Thanks for any help.

Katie

katie · Post by **katie** » 04 Sep 2010, 07:47

Oh well - I guess I'll just stick with the weather forcast then. Thanks for looking anyway.

Katie

Aurora · Post by **Aurora** » 04 Sep 2010, 09:05

Try: http://www.metoffice.gov.uk/index.html

biffvernon · Post by **biffvernon** » 04 Sep 2010, 10:13

I suggest looking out of the window. Real-time, real-data.

katie · Post by **katie** » 04 Sep 2010, 13:13

biffvernon wrote:I suggest looking out of the window. Real-time, real-data.

If only I had the time to look out of the window all day

Thanks for the link Aurora. It's appreciated.

Katie

RenewableCandy · Post by **RenewableCandy** » 04 Sep 2010, 15:45

There are some researchers at RAL who are looking at fractal patterns of rainfall and clouds, but I don't think they've actually got a predictor up-and-running for everyday-type use yet.

In the meantime I just look at the weather forecast, or else out of our window to the SW (where most of the weather comes from) but then I'm at home a lot. Failing that, just set everything to run at mid-day (assuming your panels face due South).

biffvernon · Post by **biffvernon** » 04 Sep 2010, 17:59

For near time weather forecasts a combination these two are good:

http://www.metoffice.gov.uk/weather/uk/radar/index.html
http://www.metoffice.gov.uk/satpics/latest_uk_ir.html

Post by **adam2** » 06 Sep 2010, 08:43

With a grid tied system, under the usuall tarrif and metering arrangements, it does not matter at what times you use the energy.

All surplus energy is exported to the grid, and all surplus demand is imported from the grid.
A premium price is paid for all the PV generation, regardless as to if it is used or exported.

With a stand alone battery charging system, as much load as possible should be shifted to the sunny times of day in order to reduce battery losses and battery wear.

biffvernon · Post by **biffvernon** » 06 Sep 2010, 09:54

Not quite so simple. You get 41.3 p for every unit you generate, whether you use it or export it. You get an extra 3p for exports. You save ~13p off your bill for using your own instead of buying. So by using power when the sun is shining rather than in the evening you effectively gain ~10p per unit. It is worth while using your appliances when the sun shines. There's less of a gain if the appliances would otherwise be used at night on cheap rate.

RenewableCandy · Post by **RenewableCandy** » 06 Sep 2010, 17:25

Yup that's how I understood it.

Except that there's no way yet of measuring how much of what you generate is actually used. So effectively, you're getting 42.8p for everything produced, and are assumed to be using 1/2 of it. Then if you use leccy while the sun shines (but no more than the power you're making) it's effectively free.

farookraghva · Post by **farookraghva** » 05 Oct 2010, 11:35

The amount of sunlight reaching the Earths surface is not always constant. Sunlight may vary depending on location, weather conditions, a certain day, time to time ad day of the year.

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biffvernon · Post by **biffvernon** » 05 Oct 2010, 11:58

farookraghva wrote:The amount of sunlight reaching the Earths surface is not always constant.

Damn.

katie · Post by **katie** » 07 Oct 2010, 13:50

Thanks for the rest of the replies - I have found this site to be quite reliable & it gives a rough idea of the times when it is going to be cloudy http://www.metcheck.com/V40/UK/HOME/ Just add your postcode.

After an appalling week of dismal grey cloud, we are now producing again

When I'm producing the most power, I put the breadmaker on and do any ironing, washing etc. It makes sense to use the free electricity. I'm expecting my monthly direct debit to go down next month.

Katie

emordnilap · Post by **emordnilap** » 07 Oct 2010, 14:17

katie wrote:When I'm producing the most power, I put the breadmaker on and do any ironing, washing etc.

Sounds like a hell of a breadmaker.

katie · Post by **katie** » 07 Oct 2010, 14:59

Katie