 The Technology
Gravity Film heat eXchanger (GFX) technology was developed on a US Department of Energy (DOE) grant to capture heat carried by hot water down millions of drains. According to an A.D. Little report funded by DOE, GFX could reduce residential electric water heating bills an average of 34% with a payback of 1.6-4.6 years @ 8.5-cents/kWh. Much higher savings are possible in commercial applications where larger models can be installed.
The Situation
According to DOE’s Energy Information Administration (EIA), electric water heaters provided 45% of US residential water heating needs in 1995. The EIA also estimated that in 1995 residential water heaters in the US consumed 740 billion kWh of energy and commercial water heaters consumed another 320 billion kWh. (1 kWh = 3,413 Btu)
The Problems
Approximately 80-90% of all hot water energy goes down the drain, carrying with it up to 955 billion kWh of energy in the US alone. Efforts to recycle this waste energy have been opposed by many, including the US EPA, which has failed to award an Energy Star label for any water heating or Drain Heat Recovery (DHR) system like GFX to save energy and reduce pollution.
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It’s cost-effective for GFX to transfer over 60% of the heat from drainwater to incoming cold water. Its operation is based upon a natural phenomenon whereby surface tension and gravity create failing water films that spread and cling to the inner walls of vertical drainpipes. The tension is strong enough to cut film speeds to about 1.3-3.9 feet per second and hold their thickness to 12-27 mils at 0.44-3.1 gpm, respectively. This enables very high rates of heat transfer whenever hot water enters a GFX and cold water is rerouted to simultaneously flow up its coil
Visit the GFXtechnology.com Web site.
