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11 January 2007

Here's wishing you a belated happy new year.

The winter solstice is behind us now here in the northern hemisphere, but it's still a long time until the sun is high in the sky.

Today, how to make money from my book, plus a look at the effect of shadows on your solar array.

1) Become an affiliate
2) Why shading has a big effect on performance

Teach yourself all about Solar Power

1. Become an affiliate
Have you got a web site about solar power? If so, why not promote my book, the Solar Power Design Manual? All you have to do is put a link on your site - if anyone buys the book through it, you get half of the money. It's that simple.
Sign up for free here:


You can even put the link in an email or blog; you don't have to have a site of your own!

2. Why shading has a big effect on performance

Is it really worth worrying about a bit of shade on your solar array? I mean, a few square centimetres of a whole panel can't make that much difference can it?

Well yes it can actually, and the reason is to be found in the law that states that the current in a series circuit is the same at all points.

Stay with me here: A standard 12 Volt module is not a single cell but (usually) 36 cells connected in series. Therefore, if the current in one cell is reduced then the current in the entire module is reduced by the same amount.

As an example, let's assume you have a module with cells 10 cm square. Now let's say that a shadow 5 cm square falls on the module - a pretty small shadow? Yes, but if it falls on one cell it will mask 25% of the area. That will have the effect of reducing the current in all cells by 25%, and therefore reducing the power output of the module by 25%. Not such an insignificant shadow after all then...

The conclusion to be drawn from this is that it's very important ot avoid shading the modules, even slightly. That becomes all the more important in the winter, when the sun is low in the sky and the insolation is significantly lower.

If I were you, I'd pop outside and check that no tree branches have grown across the array since last year!

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