INNOVATION March-April 2014

These diagrams depict how geoexchange functions in both a heating (left) and cooling (right) capacity.(Photo credit: GeoExchange BC.)

it flows through a heat exchanger. This device extracts the heat from the fluid and the heat is distributed through the building. The fluid continues its travels through the pipes, but since its temperature is now lower than the surrounding earth it will again absorb heat. These systems can also be used in the summer to provide cooling or air conditioning. As the fluid goes through the heat exchanger, it absorbs heat drawn from the building and is pumped back through the network of pipes. In this case, the fluid is now warmer than the surrounding earth, which acts as a heat sink that draws heat out of the fluid and reduces its temperature. Geoexchange is a highly efficient method of heating or cool- ing a building. The only energy input required is the electricity that powers the pump and the heat exchanger. Jeff Quibell, P.Eng., President of Vernon-based JDQ Engineering and current President of GeoExchange BC, points out that a well-designed systemwill deliver a co-efficient of performance of at least 3.5, meaning that every kilowatt hour of electricity used to operate the pump and heat exchanger will deliver 3.5 BritishThermal Units (BTUs) of heat or cooling. But for all its advantages, geoexchange systems must be well- designed. The plans must be site-specific and should be developed collaboratively by the owner or developer, an engineering consulting firm and the contractor who does the actual installation. “You can almost always develop geoexchange for any building and any set- ting, but whether it’s the appropriate option is another matter,” says Quibell. “We recommend that early on a geoexchange suitability assessment be done.” In fact, GeoExchange BC has developed a user’s guide and a comprehensive, four-part set of documents to ensure that techni- cal requirements are met and that best practices are followed. For example, the user’s guide includes a roadmap for the successful implementation of a geoexchange system, along with checklists to help assess the suitability of the site, procure the service providers, and to ensure that it is properly designed and commissioned. “There isn’t anything like it in North America that we’ve seen,” says Arellano. “Several expert parties have contributed to it or reviewed it. We’ve shared drafts with people in the US and they’ve been very impressed.” That level of care and caution is necessary, he says, because BC has a broader, more diverse mix of geology, climate and infrastructure

the Okanagan and some other parts of the Province have encour- aged building owners to go with geoexchange. As well, companies that design systems have promoted the advantages of the technology. “There is a higher adoption rate here than anywhere else in Canada,” says Stuart Yanow, P.Eng., Vice President and Senior Engineer with Kelowna-based GeoTility Geothermal Systems, the country’s largest geoexchange company. “It’s definitely a technology that’s gaining momentum. We’re confident that it’s going to keep growing.” There are several advantages that make the technology attractive. Geoexchange systems are durable, inexpensive to operate, virtually emissions-free and immune to the fluctuations in oil and gas prices that can drive up the costs of conventional heating and cooling systems. The upfront capital costs—or the price of admission—are considerably higher than opting for conventional systems and that can be a deterrent, but that is offset by lower operating costs. Geoexchange systems require a sub-surface, closed loop network of pipes to extract energy from the earth and the pipes can be installed either horizontally or vertically. In the case of schools or rural homes, which usually sit on large parcels of land relative to the footprint of the building, the pipes can be laid horizontally in trenches five to 10 feet deep, depending on how cold the winters are and how deeply the frost penetrates. Homes, office towers or high-rise condominiums located in urban areas almost always require a vertical network of pipes, sometimes several hundred of them depending on the size of the building. They are sometimes drilled to a depth of 150 metres, or about 500 feet, and they are usually installed beneath the foundation and within the footprint of the structure. The pipes are made of high-density polyethylene plastic measuring four to six inches in diametre and fluid is pumped from the building through the pipes. In horizontal systems, the pipe is laid out in the form of a long, narrow U-shape so that the fluid can flow out and then back to the building. In vertical systems, pairs of pipes are linked by a U-joint at the bottom, which allows the fluid to flow down and then back up and into collection pipes that return it to the building. The fluid is usually about 80% water, topped up with anti-freeze and other liquids that prevent corrosion. It circulates continuously through the closed-loop network of pipes, absorbing solar energy from the earth in the form of heat and returning to the building where

M a r ch/A p r i l 2 014 19

i n n o v a t i o n