Solar

Global Agency Should Study New Application of Earth Energy

A Canadian researcher wants the International Energy Agency to examine the use of earth energy heat pumps to extract waste energy from sanitary sewers.

OTTAWA, Ontario, Canada, 2001-09-27 [SolarAccess.com] Otto Svec wants the IEA to establish a new Annex that will explore the feasibility at a new school to be built in the city of Ottawa. The cost of his proposed annex would be Cdn$100,000. The technology behind ground-coupled heat pumps has been used since 1912, explains the researcher at Canada’s National Research Council. The technology transfers solar heat from the ground into a building, but has been slow to penetrate the market because of relatively low cost of electricity and natural gas, and the high installation cost of installing the pipe needed for the transfer. “But now, with all the environmental changes occurring worldwide, interest in all renewable sources of energy is increasing,” he adds. Governments in the United States, Denmark, Germany and Great Britain require utilities to generate electricity from renewable energy, while subsidies are offered for consumption of green energy in the U.S., Denmark, Japan and the Netherlands. Water that flows through a sanitary or storm sewer in winter contains heat, which escapes when the warm air flows through the manhole cover. Svec wants to direct that warm air through vertical slots in a modified top ring of a manhole, from where it would be directed to a special layer of aggregate which uses geotextile to form a donut-shaped natural radiator based on the ‘frost-heave mitigation’ principle. The city of Ottawa reconstructed six sewer manholes to incorporate the concept, and testing during the past three winters shows that the heat from the sewers can be transferred through a closed-loop heat pump into nearby buildings. “A complete new ground source heat exchange system can be easily and inexpensively put in place during the construction of sanitary sewer,” says Svec, in either new construction or retrofits. “It is very important to design the system properly, with knowledge of how much energy can be withdrawn from sanitary sewer part of entire system without freezing its content.” He says the concept would lower the initial installation cost of earth energy systems by reducing the amount of loop to be buried in the ground to transfer solar energy, as well as capturing and using the energy from sewers which normally is lost. It would also lower the amount of anti-freeze used in closed-loop heat pumps and decrease the rising level of toxic gas in sanitary sewers. “implementing this ‘new’ source of renewable energy could arouse the sluggish use and development” of earth energy heat pumps, he concludes. “In the current worsening state of the global environment, any attempt for its improvement should be ardently supported and developed.” Svec is known in the industry for his development of a spiral pipe that lowers installation costs for ground-coupled heat pumps, the largest cost behind a system.