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Simple Drain Heat Recovery System Can Save Up to 50% Heating Energy


This morning I found an ingenious idea by RenewABILITY Energy, called Power-Pipe Drain Water Heat Recovery (DWHR). The name should say it all – it’s a system designed to recover the heat of the water going down the drain and to reduce heating costs by as much as 40 percent.

The idea is brilliant yet simple (and I don’t think they really invented it in the first place): take a large copper tube that you pass the waste water through, and then surround it with three other thinner copper tubes, that you pass fresh water through.

This simple heat exchanger will pre-heat your incoming cold water up to 24 degrees Celsius (75 °F) and will reduce the effort of the electric (or gas) heater to bring the cold water to that temperature.

Water going down the drain doesn’t run through the middle of the pipe, just like electrons never run through the middle of the wire. It instead flows on the walls of the pipe, exchanging heat energy with them. This is the basic principle on which the DWHR works.

Now, you think you could build such a device at home, cheaper… and you may be right. But you need to use copper, which is expensive, you have to have an exact design of what you’re doing, and you have to find someone to put things together, since in most of the cases you won’t be able to do the job. Or you can buy it directly from RenewABILITY for prices starting at $500.

The company says you’ll be able to recover your investment in as little as two to seven years, and its results have been tested by the Canadian government.

Whether you want to buy or build such a device yourself, you have to think about this possibility that will save up to a ton of carbon dioxide per year and make you less dependent on energy.

(This article is not paid advertisement, although it looks like one. I just found these guys’ idea brilliant)

[via treehugger]

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  1. Instead of letting the used water to go away after it passes the heat exchanger why not combine this idea with a thermos/vacuum isolated recipient? The heat exchange would be more efficient and the pre-heated water will last much longer, even > 24 h!


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