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efficiency of solar panels

We intend to install solar panels to power borehole water pump, and have been advised to enable switch to alternatives when panels produce less power eg rainy season and harmattan. What %age of optimum output is expected without direct sunlight? We are advised to enable use of mains electricity (often absent for weeks) and diesel generator as the alternatives.

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have a look also at other posts on this platform - the efficiency is affected by the position etc. Solar panels will change in rain / under a full moon. You probably also want to consider the quality of the panels (manufacturer) and maintenance (cleaning etc).

Liz Palmer gravatar imageLiz Palmer ( 2020-01-28 15:05:09 +0000 )edit

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Hello Helen,

check by the World Bank, it shows photovoltaic power potential data on different regional and national levels.

Maybe these resources from energypedia could also be of help:

Best, lisa

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Can you get any data from local weather stations ? The PV output will vary approx the same as the solar irradiance - ie if that drops by 50% the output will drop by 50%. If the interuptions are likely to be short, you could provide a larger water tank (say 3 days supply or something) to compensate. But if the harmattan goes on for weeks (?) then you probably will need an alternative supply. There is quite a bit of data here which covers Africa and should show the reduction in the wet season, but I doubt if it includes things like the Harmattan.

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Hello Helen,

This is not really my area of expertise but have you considered a wind generator as your back-up power source? I believe that the winds are fairly consistent during the Harmattan but the wind-borne dust and sand particles could be a problem by causing erosion of equipment. You could also consider battery back-up but if you have reduced sunlight for prolonged periods recharging the batteries would be as much a problem as powering your pump.



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hello. In the wind pump area there are those really strong wind pumps made of steel plates. here you have a link just to show what I'm talking about there is also the panemona savonius which can be built easy amb they are stunning strong. Both can be built low tech

adolf gravatar imageadolf ( 2020-01-28 17:25:53 +0000 )edit

Hi Helen The European solar website noted above ( is a fantastic tool for a quick solar PV design. I used it loads of times in the past when I was an energy consultant ( now retired) If you pretend that your system is an off grid solar you can see how storage affects it. You can get hourly data for your site in Nigeria from the map. It will optimise solar panel angle and orientation for max efficiency Although I don't know about irrigation systems, in general I assume that water storage tanks are a lot cheaper than batteries, so you just need a big enough tank to cover your needs for the longest period where there is insufficient sun. Practical Action have designed loads of solar irrigation systems for Zimbabwe and have loads of practical detail somewhere on their website Good luck!

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2020-01-25 21:32:53 +0000
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