GVRD – Geoexchange System

The need

The Greater Vancouver Regional District (GVRD) is a partnership of 21 municipalities and one electoral area that make up the metropolitan area of Greater Vancouver. The GVRD serves more than two million residents, providing a variety of essential utility services, including the provision of safe, high-quality drinking water. This includes the construction of a new water filtration plant (Canada's largest), which includes ultraviolet disinfection, to treat water from both the Seymour and Capilano reservoirs.

Such facilities are energy-intensive and expensive to operate and maintain. Since natural gas will not be brought to the site, the five- to six-megawatt plant will be an all-electric facility. It was originally designed with electric resistance space heating, cooling and hot water heating. However, at a BC Hydro Design Assistance workshop, it was determined that a geoexchange system was the most energy-efficient and cost-effective option for providing space heating, cooling and hot water heating at the plant. As well, because geothermal energy is a clean, renewable energy source, it reinforces the objectives of the GVRD's sustainable region initiative.

The technology

Almost everywhere in the world, the upper 10 feet of the earth's surface below the freezing line maintains a nearly constant temperature between approximately 10° C and 16° C (50° F and 60° F), remaining warmer than the air above it in the winter and cooler in the summer. A geoexchange, (sometimes called a geothermal, heat pump or GHP) system transfers heat stored in the earth or in ground water into a building during the winter, and transfers it out of the building and back into the ground, or water during the summer. In other words, the ground, or water body acts as a heat source in winter and a heat sink in summer.

A geoexchange system consists of pipes buried in the ground, a heat exchanger and ductwork into the building. The series of pipes, commonly called a "loop," is buried in the ground, either vertically or horizontally, near or beneath the building. The loop circulates a fluid (water, or a mixture of water and antifreeze) that absorbs heat from, or relinquishes heat to, the surrounding soil, depending on whether the ambient air is colder or warmer than the soil.

The project

The Seymour-Capilano filtration plant will use an all-encompassing geoexchange system for space conditioning and hot water heating. The system will incorporate an innovative approach to the installation of a horizontal ground loop. Normally placed in parallel runs in the ground, the ground loop for this facility will be incorporated in approximately 45 loops, totalling 42 km, under the concrete floor of the clear well.

The Seymour-Capilano geoexchange installation will be the first of its kind in a drinking water treatment plant in B.C. The construction concrete work will start in the summer of 2004 and the project is scheduled for commissioning in early 2007.

The benefits

Electricity savings

Although the installation costs for geothermal systems may be higher than those for conventional systems, the cost is rapidly offset by substantially lower utility and maintenance bills. Typically, geoexchange systems reduce heating and cooling costs by 25 to 40%. As well, heat removed during the summer can be used as no-cost energy to heat water. At the Seymour-Capilano filtration plant, the geoexchange system is estimated to save .528 gigawatt hours of electricity per year.

Enhanced comfort

Customer comfort is typically very high with geoexchange systems, since heating and cooling can be done simultaneously and the systems offer zone control of heating levels.

Environmental and social benefits

An advantage of geoexchange systems is that they work by concentrating naturally existing heat, rather than by producing heat through the combustion of fossil fuels. By displacing electricity, the Seymour-Capilano filtration plant system will reduce associated greenhouse gas emissions by 325 tonnes per year. This means less air pollution for the entire region. Customers appreciate facilities that employ ecologically sound technologies.

More efficient use of space

Because most of the system is buried underground, it decreases space requirements inside the facility for heating, ventilation and cooling equipment.