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Sun Volt Solar

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We are at a cross roads in human history, we can choose to continue on as we have been, or we can make a change to improve our future and quite possibly the future for several generations to come. We are here to promote energy independence, a better environment, a secure future and a higher return on investment for your hard earned dollar. It is what I believe in, it is why I am in the solar business.

Gravity Film Heat Exchangers or GFX

29 Dec 07 | Conservation, Environment, Solar Hot Water

Update: Sun Volt Solar is now an authorized dealer of ECO-GFX gravity film heat exhangers!  For more information, check out our GFX web page.

I am always looking for ways to improve efficiency, especially in energy use. I came across something called a Gravity Film Heat Exchanger or GFX system. These units recover heat from waste water and return it to the hot water tank. Since 80-90 percent of household hot water heat goes down the drain, literally, what a great way to recover some of that energy and reuse it.

Here is how they work: Hot water from a shower or sink runs down the drain and out into the sewer. If there is a vertical run of pipe, the water, because of adhesion, runs down the wall of the pipe (and not the center). If the pipe is metal, heat is transfered from the water to the metal pipe wall until the pipe is the same temperature as the water. All of this happens in any sewer line. If the vertical section of pipe has a heat exchanger attached to the outside of it, the heat from the metal pipe is conducted away to be reused. Most often cold water feed into the hot water tank is run through the heat exchanger. The system efficiency depends on the difference in temperature between the waste water and the incoming cold water. The greater the difference, the higher the efficiency.

This system only works where there is simultaneous hot water use and immediate drainage, say a show or sink. Something like a bath or laundry would not work well because the hot water is drawn off, used, then drained away.

It appears that the system is around 45-50 percent efficient. Therefore, if you use 70 percent of your hot water in showers or sink use, you would recover 30-35 percent of your total hot water energy. Not too bad.

These systems would work very well with solar hot water systems. I am contemplating installing one at my house to see if they work as advertised. The only requirement is that they be installed vertically. In fact, in order to work properly, great care should be taken to make sure the unit is perfectly vertical. For more information, see the NREL website on waste water heat recovery or this .pdf file called Heat Recovery from waste water using Gravity Film Heat Exchangers.

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29 Dec 07 | Conservation, Environment, Solar Hot Water | Comments (0)