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Solar Space Heating


ebrsa
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I have embedded Pex pipe loops in my concrete floors when building the house with the intention of heating the floors with solar heat. All this was based on information from numerous articles on the Internet. Having installed an EV-tube heater for domestic hot water recently, I fear that using solar to heat the floors in winter is wishful thinking. Not enough solar radiation in winter and too much in summer when I won't need it. I live in Yzerfontein on the Cape West Coast, about 80 Km north of Cape Town so sunshine in summer is plentiful but less so in winter. The EV-tube heater for the domestic water works very well with little need for grid electricity.

It would seem to me that perhaps a swimming pool heat pump, powered by excess power from photo-voltaic panels, once the inverter batteries are charged, may just be the answer and should limit electricity consumption from the grid. It will take time to heat the floors but it seems that concrete can absorb about seven times as much heat as water so once heated they should keep the house warm for some time. So I am considering installing a 300 liter insulated tank from Xstream, which I have, as a buffer tank. This will eliminate undue pressure developing in the system and water at about 35C will be pumped from the tank to the floors. The heat pump will heat water in the buffer tank when excess output from the solar panels is available.

Does anyone have experience of something similar or maybe some advice or ideas on the subject. Your input will be much appreciated.

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I am using waste heat from my generator for space heating. Basically when it is overcast and the solar needs some supplementing, wtehe cooling water is circulated through radiators using a solar circulation pump.I'm not sure that heating the water with solar will work too well as when you need the heating the solar will be at its weakest.Another way to heat the water will be to use a closed combustion fireplace with a water heater and then circulate that water. That should make the lace nice and toasty.

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Thanks for your suggestion DeepBass9. I am connected to the grid in our village so only rarely run my generator which is air cooled so your system won't work for me. Looks like a pool heat pump, driven when the sun is producing maximum power with photo-voltaic panels may be a solution if I don't want to use grid power. Once the floor slab is hot, it should be able to radiate heat for a considerable time. Hydronic under floor heating remains the most effective method of space heating in my view. To optimize this method one just have to find the best way to harvest heat from the sun, directly or indirectly with solar heat and power together with a heat pump of sorts. I could extend the time the heat pump runs by driving it from my inverter and not draining the batteries below 80% SOC. This will determine the number of photo-voltaic panels I install. Of course adding a EV tube heater will help but then I end up with excess heat in summer. Still I find it an interesting project requiring plenty of thought and hopefully expertise from other forum members.

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In think you will find you need a lot of pv to heat the water, and when it is really cold, you will have none. Today for instance it is completely misted over and yesterday my panels essentially made no power at all. I do have heating though from the generator, and a wood burning stove would also supply heated water. Probably much cheaper than heat pumps and pv.

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Thanks for your reply. I am still researching the heat pump option. If solar cannot generate sufficient power, I will just switch to the grid. Once the floor slab has heated up, it should stay warm for some time. Of course one has no control over changing the temperature quickly but as long as it reduces most of the winter chill, it will be fine. I am looking into adding a heat exchanger to the fireplace to capture some of the heat that is now wasted.

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