Solar models - for nerds only

02/27/2011 - 07:53

this may be a bit esoteric but I have just put up 3 updated Excel models on in the downloads section. These cover panel angles with a graphical study on how fitting oversize - wet -panels with steep angles can give a really usefully extended solar production period. Seeing that PV panel suppliers use 30 degrees slope round here I built the panel angle model to check for maximum production, month by month, and the result was strangely exactly 30 degrees, not 29 or 31, just 30. The data came off the NASA web site so if you don't live in Umbria you can look up your own area and change the model. The tank sizing model is really useful if you are wondering how input power ralates to energy stored and how resposive the tank will be. Along with the pipe sizing model next to it you can also use it to see what sort of power transmission you can get down certain pipe sizes. The PV production model allows you to key in your own chosen panel array and see what sort of income to expect for the tariff you deal into. Have fun and, N.B. I don't sell solar kit.

Topic

Technology

Location

Perugia Province

Umbria

Comment

Interesting, I always understood that to maximise solar gain in the winter you needed a steeper angle, so for our latitude, 40 degrees the optimum winter angle is 57 degrees . So I'm surprised that 30 degrees works so well. I'll have to experiment myself.

yes the reason for 30 degrees being best is that summer sun is so much better than winter sun that to get the best overall production (ie PV panel income) you need the flatter angles. The steep winter angle you mentioned is really good for wet panels if you have lots of them - say up to 10mq - as you can mitigate the summer peaks in favour of fatter shoulder months. Have a look at the model on the web site as it has a lovely graph for you to experiment with. One important thing to always bear in mind with wet panels is that they are cheap and so we are not really bothered with efficiency we just want to build a production curve that suits our needs .. eg fat enough shoulder months for pool heating and maybe not so much in mid summer when there is virtually no demand for hot water.

Capito, I'll have my solar PV at 30 and my wet panels at 57, but I'll need to watch out for the wind I expect! PS you've also made me think more about an air source heat pump, however i'm still keen to be frugal and stick with a 3kw supply.I'll bash on with the insulation first.

PS you've also made me think more about an air source heat pump, however i'm still keen to be frugal and stick with a 3kw supply.I'll bash on with the insulation first. Would suggest you steer clear of the Chinese models at the moment, as these are " bitzas" May be cheap, but when they go wrong!!!!

Hurro Badger, how can you tell if it's made in China ? What brand names should I avoid? PS I remember that, post war, the Japanese named an industrial town Usa so they could print made in USA on the box of any products.

Just stick with well known long time manufacturers, that have their own plants to make them. At least then if spares are needed, you have more chance of getting them quicker.