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Newsletter Archive

15 November 2006

Today, no need to design your own solar power system. Why? I've done it for you!

1) Complete Solar Power Systems
2) Insolation - how sunny is it here?
3) Phantom Loads - Update

Teach yourself all about Solar Power

1. Complete Solar Power Systems

Are you confused about how to design a solar power system to suit your needs? I've produced instructions for three systems to cover most eventualities. Download them here:


Do exactly what they say or modify them to suit your needs - it's up to you.

2. Insolation - how sunny is it here?

The sun shines all day here, so there must be loads of power available, mustn't there? What about days when it's overcast, will solar power work?

The answers to these questions require an understanding of the concept of insolation. Insolation is the measure of the amount of solar energy falling on the Earth's surface - for solar power applications it is usual to use the daily average insolation by month, falling on a tilted surface of 1 square metre.

The insolation is measured in kilo-Watt hours, so the daily average is measured in kilo-Watt hours per metre squared per day (kWh/m2/day). Conveniently for us, when the sun is high in the sky on a cloudless day, the solar radiation at ground level is almost exactly 1 kW/m2, that is, every square metre has a kilowatt of visible radiation incident upon it. This is the power level that the output of a solar photovoltaic cell or panel is rated at.

All this means that, for practical purposes, the insolation can be taken as equivalent to the number of hours of full sunshine per day. So if you say that the insolation for a particular place is 4 kWh/m2/day, then you can assume that that is the same as 4 hours of sunshine, so a panel rated at 50 Watts will deliver 50 x 4 = 200 Watt-hours of energy per day before losses in the charging system. That means that you don't have to worry about whether it's sunny or not; as long as the battery is big enough to overcome the peaks and troughs you know how much power you can use.

Practically, insolation may vary between 1 kWh/m2/day in northern Europe in winter, to 7 kWh/m2/day in Sub-Saharan Africa or the Australian Outback.

Find out more about insolation here:


3. Phantom Loads - Update

The last issue had an article in it about phantom loads. One of my readers very helpfully sent me a link to a company which makes a product which helps to deal with the problem. It's a device which you plug all your computer peripherals into which switches off the mains to them when you power the computer down. It would work equally well for hi-fi equipment, and no doubt there are many other applications which I haven't thought of yet.

The URL is:

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