Drain Water Heat Recovery Devices
A version of this article appears in the May/June 2008 issue of Home Energy Magazine.
May 01, 2008
Drain water heat recovery (DWHR) devices are little-known but effective means to save hot water energy and homeowner dollars.
Heat recovery ventilators (HRVs) recover heat energy from air exhausted from homes, saving energy and money for the homeowner. But houses can use up to 20% of their energy heating water, and much of that energy can slip away down clothes washer, sink, and shower drains. Drain water heat recovery (DWHR) devices are little-known but effective means to save hot water energy and homeowner dollars. At the Canadian Centre for Housing Technology, we have been studying the effectiveness of DWHR devices. In our 2005 study, we found that DWHR devices recover energy almost exclusively during simultaneous water draws (showers), and that for modeling purposes, all other water draws could be ignored. Based on this conclusion, we sought to characterize the DWHR devices in order to develop an energy savings calculator. The purpose of our experiment was twofold. Our first purpose was to assess the performance of DWHR devices. Our second purpose was to develop standard tests and modeling methods that would enable manufacturers, utilities, policy makers, and consumers to estimate energy savings caused by these devices. The DWHR technologies we tested are fairly simple in design and can be effective in reducing the amount of energy needed to produce hot water (...
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