This idea is particularly suited for a home when the nightly temperature is too cold and the daily temperature is too high. In a simple embodiment, the system would consist of two radiators, a quantity of water sufficient to fill one of them, and a pump between them. The two radiators would respectively be located indoors and outdoors, and each would have atmospheric venting. At night, the indoor radiator would be empty, and the outdoor radiator would be full of water. At sunrise, the pump would pump the water to the indoor radiator, where the cool water would be used to cool the home. At sunset, the water would be pumped to the outdoor radiator once again, where the water is allowed to cool at night for use the next day.

In a second embodiment, four radiators would be used, alternating the water between them to keep the house both cool during the day and warm at night.
-- kevinthenerd, May 08 2017

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