solar hot water

Dear Ursula,

Evaporation for 25th to 31st October 7,7,8,8,8,7,8

Very few of us recorded any rain in October and this is true of only 25% of my records – going back to 1950. However, my records also indicate that, in years with no October rain, the total is actually higher than the average of wet October years – so the verdict is still wide open.

I hope those of you who attended the Greenleaf presentation on Saturday at the Sports Club were inspired to think more and more in terms of solar power. David Falkenberg told me of a company, Freedom Won, who are converting vehicles to electric battery power. Their website is quite fun, even if their prices are beyond me. (However I am asking them to quote for a suitable battery).

David, Steve Hodge and I also discussed the challenge of fitting a solar hot water system to a thatched house. One doesn’t want to fit it to the roof (as one would normally do) because the thatch would quickly rot, and it is quite awkward to plumb a solar water heater if it is situated some distance from the house, where it will get proper exposure to the sun. I had hoped that Steve and David would work this one out, but my mind wouldn’t leave it alone and I think I have a solution that is worth trying. Put a single 300W panel wherever it suits you (i.e. in full sunlight). Fit two geysers in series. The second one, just before your bath/shower, is connected to ZESCO. The first one receives the cold water and is heated by an element, powered by the solar panel. A single panel in 6 hours of sunshine could easily heat 200 liters of water a day from 20C to 90C. Because the water is already hot when it moves into the second geyser, the ZESCO element has to do nothing more than maintain the temperature. This would cost a fraction of the cost of an evacuated tube glycol solar heater and has no moving parts The only tricky part is finding a suitable element……watch this space.

I also hope to meet with ZESCO when I go to Lusaka on Wednesday/Thursday this week. I hope to get all my load shedding (and therefore the load shedding of the Sibanyati line, all the way down to Kala) moved to daylight hours. Not only would this allow me to get maximum benefit from my solar panels (with minimal use of batteries) but would also mean I run my generator during daylight hours (when it is easier to monitor). I will be negotiating for a price of my surplus solar power at least 60% of what I pay ZESCO for their Kariba power. I am prepared to give them this 40% margin as they provide the service of storing my surplus energy for when I need it – much cheaper than batteries! However, I have yet to receive confirmation of an appointment, so I suspect that ZESCO will be a more difficult solution to crack than finding the correct technology.




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