Until recently, recovering heat in wastewater discharged from fixtures and appliances in dwellings, commercial buildings and industrial plants was a largely neglected source of energy.

However, with the rising cost of energy and the need to reduce greenhouse gases, greater attention is being given to this readily available and clean energy source.

Several heat-recovery systems are now available, particularly from companies in Canada, and new systems are also being developed in Europe.

Andre Cayer is president of Watercycles Energy Recovery, which is based in the Canadian province of Saskatchewan. The company manufactures the Watercycles heat-recovery system and exports to the United States and Europe.

Cayer says the system is designed to recover energy from water being flushed down the drain in residential and commercial applications. It uses no energy itself, and there are no moving parts.

“The Watercycle, which has a copper coil system and forms part of the wastewater pipe, extracts heat from the wastewater. This heat is then conveyed to the incoming fresh water before it reaches the water tank, thus pre-heating the supply. The system will extend the life of a hot water tank and reduce the stress on a tank-less water heater.

“In residential situations, the Watercycle requires no maintenance and has no effect on lifestyle while saving money and reducing greenhouse emissions. The system will recover its cost in two to seven years, and this is based on shower use only.

“For commercial applications, the main opportunities are in areas such as multiple shower installations in fitness centres and swimming pools, and dishwashers in commercial kitchens. The cost is greater due to the fittings and installation time involved, but savings are also greater because of the higher volume of hot water consumed in a commercial setting.

“In the case of dishwashers, the water temperature is also a factor, due to the delta T (change in temperature). The greater the difference between incoming fresh water and heated wastewater, the faster the heat travels, and therefore there is greater effectiveness.

“There is a C$100 (US$98) government grant across Canada for home-owners who retrofit, and in Saskatchewan the grant is C$200 (US$197), which is 30% of the purchase cost. There are also grants in Saskatchewan and Ontario for installations in new homes. In addition, several natural gas companies are offering grants to builders and home-owners in various provinces.

“Despite the grants, our largest market is the eastern US, where energy costs are three times those of Canada, so people can’t afford to throw energy away. Our main goal is to have Watercycle installed with tankless and solar water heating systems.

“Tankless systems are designed for groundwater temperatures of about 20ºC (68ºF). In locations where the water is 10ºC (50ºF) or less they have difficulty meeting the demand and a larger unit is required, which will of course consume more energy.

“The Watercycle will put water into the tankless system over 20ºC no matter how cold the incoming water is (for our standard 58 long unit). This wastewater heat-recovery system will also increase the amount of days the solar system can provide 100% of the hot water needs. It will provide more energy per dollar spent than increasing the size of the solar collection system.”

Renewability Energy, based in Ontario, manufactures the Power-Pipe drainwater heat-recovery system, which the company says is installed in many commercial, industrial, multi-unit apartment and residential applications in Canada, the US and Europe.

According to Renewability Energy vice-president marketing Walter Urban, the US Department of Energy and Natural Resources has identified water heating as the second largest energy use in American and Canadian homes, accounting for 20-30% of home energy costs.