The Energy Center of Wisconsin was awarded a 2011 Conservation and Applied Research Grant from the Department of Commerce, Division of Energy Resources for field testing drainwater heat recovery (DHR) systems in Commercial Buildings.
DHR systems include replacing a portion of vertical drain pipe with a heat exchanger module. The heat exchanger module can consist of a copper vertical pipe (drain line) to match the diameter of drain pipe being replace, surrounded by a coiling smaller diameter copper pipe (supply line). The system works when warm water (say, from a shower, washing machine, or dish wash station) flows vertically down through the drain line and cool water flows upward through the supply line and onto a water heater for additional heating.
CERTs recently sat in on a webinar from the Energy Center about the nearly completed study. The main take-aways are as follows:
- DHR systems are an elegant technology in search of good applications.
- Easier to implement during new construction, but can be retrofitted in the right situations.
- Out of the four pilot locations, DHR systems installed in the restaurant performed best by recovering 26% of total hot water energy originally delivered.
- DHR systems can recover 9.2 to 42.6 million BTUs of heat annually, saving about $100 to $400 on heating bills each year.
- Retrofitted systems cost $1,500 to $3,800 and new construction systems cost $1,250 to $2,800.
The content delivered by the Energy Center about DHR systems was definitely interesting and CERTs will be keeping an eye out for appropriate applications for this technology.
However, something that struck CERTs while attending the webinar is that the DHR system retrofitted in the restaurant setting results in the same amount of annual energy savings, around $400 each year, as upgrading to an efficient pre-rinse spray valve. Until August 31st, restaurants and others with commercial kitchens can obtain deeply-discounted pre-rinse spray valves through our Make A Splash program. A $28 dollar investment with 1-2 month pay back sure is quick and easy!
Are drainwater heat recovery systems worth the investment? It depends…
Heating hot water can account to a large proportion of overall energy consumption, particularly in commercial buildings with specific water-intense activities such as laundries, health clubs, restaurants and larger multifamily buildings. The Energy Center set out to determine if drainwater heat recovery systems, which recoup some of the heat ordinarily lost when warm water goes down the drain, could save a significant amount of energy in certain commercial applications. The two-part webinar on July 11 explored what was learned about practical installation and the energy-savings potential of commercial DHR systems.
Download the original PDF slide show from Energy Center of Wisconsin here.
You may also view an on-demand recording of the presentation here.
Did you know? Minnesota Energy Resources has a utility rebate for $175 per DHR system. Visit Minnesota Energy Resources website for more information.
