Canada is moving toward adoption of a national standard that will encourage the use of storage for renewable energy technologies.
OTTAWA, Ontario, CA, 2001-03-13 //SolarAccess.com// Underground thermal energy storage (UTES) is a process of storing free or cheaply available energy within the subsurface of the earth. The practice is used in several European countries, particularly the Netherlands and Sweden, with at least ten major projects already operating in Canada and the United States. UTES can address “the temporal mismatch between energy supply and demand in large stand alone buildings, district heating and cooling systems, waste heat recovery, solar heating and even heat storage in wind turbine applications,” says David Wartman of Environment Canada. A number of federal departments are using or contemplating the technique, including a Public Works building near Toronto that was commissioned in 1985. That facility uses solar collectors to heat water in the summer, which is injected into a slow moving underground stream and then extracted six months later to provide heating for the building. During winter, water is cooled and injected in the same aquifer, and extracted in summer to provide air conditioning. The process has significant potential for increasing energy efficiency and reducing greenhouse gas emissions from the use of conventional energy sources, but “a nationally recognized standard is required if Canada is to avail itself of the practical knowledge gained this far” in other countries, explains Wartman. Monitoring by federal departments in Canada has indicated that GHG emissions can be reduced by as much as 92 percent compared with other heating and cooling options, and the energy agency in the Netherlands has suspended fees for the use of UTES because of its numerous benefits. Water used in the process is not wasted, but is recycled to avoid depletion of aquifers and other sources of groundwater. There are a number of applications that can use UTES, but the renewable energy industry in Canada agreed that earth energy systems have the most immediate need for a national standard to ensure quality systems. The country’s national standards organization, CSA International, has agreed to include a UTES standard as an integral part of a new installation standard that addresses ground source heat pumps. The environmental concern with UTES is that a poorly designed system can harm underground water supplies, with impacts ranging from clogged wells and changes in water pressure, to bacteriological and chemical effects. The new standard will provide guidelines for the proper design and installation in aquifers, gravel beds, waste heat sinks, abandoned mines or caverns. “Many variations of UTES systems are market ready and attention from engineers, architects and decision makers is growing,” adds Wartman. The process is designed to store thermal energy that is more than 50oC, and it can be measured over months or even hours. Although it is most suited for commercial, institutional and industrial applications, the residential market can also benefit. There are only 40 major projects around the world, but the total number of systems is in the thousands if earth energy heat pumps are included in the tally. Government officials said the solar thermal industry in Canada was not yet ready for UTES applications. The new CSA standard is expected to be finalized this year, and will then be approved as a national guideline.