November 3, 2008

Geothermal energy gains ground

Construction Corner

Korky Koroluk

The various names attached to heat pump systems are confusing to ordinary people, but whether you call them earth energy systems or ground-source heat pump systems or geothermal systems, they have become a hot green technology that is slowly enlarging the niche it has occupied for many years.

The market for various versions of these systems in North America has been growing at a steady 30 per cent per year, since the need to reduce greenhouse gas emissions became a popular issue just a few years ago.

But even at that, their total market share is only about one per cent.

The up-front costs have always been the killer. A spokesman for the Geothermal Heat Pump Consortium in the United States said that for residential applications, a geothermal heat-pump unit costs about the same as a conventional furnace.

But, the additional cost of either burying the associated piping in the ground or sinking a couple of deep boreholes, discourages would-be buyers.

Now, though, with more and more applications proving their reliability and providing solid figures about pay-back times, the technology’s popularity is increasing.

For example, a hospital under construction in the Chicago suburb of Elgin, Ill., will use a geothermal lake for its heating and cooling.

The hospital, owned by a private health-care service provider, will be a 255-bed facility costing US$310 million.

There was to be a five-acre stormwater detention pond on the grounds.

The owner bought more land so there would be room for a 15-acre pond that was five metres deep. That’s where the piping is being installed.

The cost of the system will be $4.5 million and the additional land added $1.6 million.

Against that, an engineering analysis done for the owner estimates annual savings from the system of about $1 million a year. The total payback time, then, is expected to be just more than six years. After that, the annual savings will go into the company’s piggy bank.

This is not a first. The same mechanical consultant had already done a “lake-loop” system for a hospital in Iowa.

There is another large lake-loop system in England.

It turns out that geothermal systems can be pretty attractive for any buildings that continually shed heat.

Hospitals, with all their electrical equipment and high-lighting systems in operating rooms, are prime candidates. So too, is any commercial building occupied by a lot of people.

With that in mind, ground-source geothermal units were installed in a low-energy commercial building in Montreal.

They comprise 4,180 square metres, accommodating offices and some retail space.

The energy savings have been impressive. A published technical report on the project claims that the annual electrical energy consumption was reduced by 71.4 per cent compared to a nearby reference building.

This is a cold-climate building, so there ought to be some direct lessons to be learned by owners and engineers contemplating geothermal applications in other projects elsewhere in Canada.

The report was published in the latest newsletter from the IEA Heat Pump Centre.

The Centre is an offshoot of the International Energy Agency.

It’s quarterly newsletters can be downloaded at www.heatpumpcentre.org.

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