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Solar Thermal Photovoltaics
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Doesn't the circulating pump use a lot of power? Not really. We recommend a closed loop system, in which the pump does not have to provide a head, but only overcome frictional losses. A typical pump in this situation uses about 40W, but remember it is not running all day. Looking at the figures for Justin Walters' installation here, the average heat input from his collector field is around 2kW when the pump is running, so that the pump is consuming 2% of the energy provided. Also, most of the 40W is not lost, but transferred to the solar fluid in the form of heat, so it could be considered as a very small immersion heater. If you are still concerned about this, consider a modulating type pump drive which reduces the speed and hence power consumption of the pump in proportion to the temperature difference between tank and collector. |
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