Night Radiation Cooling of Water Flowing Over Roof

David lives in Castlemaine, Victoria, Australia with hot and dry summers. He is working on a simple and inexpensive and very energy efficient space cooling system that uses water cooled via radiation to the night sky.


roof spray water cooling

The system works by spraying water from a water tank over the roof at night where it cools by radiation and evaporation. The water is then collected via a gutter system and returned the tank. The next day, the cooled water is used for cooling the home's living space.

The system shown here is trial system aimed at determining how effective the radiation cooling is. David is interested in comments to improve the system and methods for delivering the "coolth" to the house living space.

Thanks very much to David for providing this material!

See David's the 10 page pdf below for the full details.


The roof spray setup. The spray pipe trickles water down the roof where it is cooled by radiation to the sky and evaporation, and then collected by the gutter and routed back to the tank.

radiation cooling system

Left picture shows the spray tube on the roof and the collection gutter. Right is closup of spray tube. Click to enlarge.



coolth storage tank

In this trial system, this 275 gallon IBC tote stores the cooled water. In the final system, the cooled water tank would be located right in the living space and would directly cool the living space by radiation and air convection around the tank, or (if needed) with the help of an active "coolth" distribution system (see the pdf).


Full details on David's Night Radiation Cooling of Water Flowing Over Roof Design... (10 page pdf)


For a little more on a similar cooling system...


David is looking for ideas on how best to apply this cooling method. He is interested in comments both on the roof radiation cooling scheme, and also on the best way to distribute cooling to the house living space once the "coolth" storage tank is located inside the living space -- is just radiation and air convection around the cooled water tank going to be enough, or is some more active form of "coolth" distribution needed, and what from might that take?

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