Vancouver community centre uses the sun to cool off
Nina Winham For bchydro.com
As energy costs rise, one of the oldest forms of air conditioning could find renewed popularity for both residential and commercial use. Unlike conventional cooling systems, it uses little electricity. And as the new Southeast False Creek Community Centre in Vancouver's Olympic Village is proving, it can even be powered by the sun.
It's called absorption chilling. Invented in 1858, it exploits the attraction between a brine solution and fresh water to create a cooling effect. It requires no Freon-based refrigerants, and no compressor to operate.
"From an electricity perspective, the absorption chiller uses an order of magnitude less electricity than a standard compressor system," says Vlad Mikler of Cobalt Engineering, who designed the mechanical system for the community centre at the Olympic Village . "So if a given size conventional chiller has a three kilowatt compressor, an absorption chiller of the same capacity will require only about 300 watts [0.3 kilowatts] for a small circulating pump to move the brine mixture through."
There is a catch, however: absorption chillers require thermal energy (heat) to drive their cooling process.
"That's the missing link," says Mikler, "and that's one reason why absorption chillers are not being used as predominantly as they were in the past. If you don't have a source of heat, you have to provide it, and it doesn't make sense to have a fossil fuel boiler providing heat to drive the chiller." (Absorption chillers have, however, remained popular in situations where there isn't consistent access to electricity – in particular, in refrigerators for recreational vehicles.)
At Vancouver's Olympic Village, the simplest form of thermal energy has been harnessed for the community centre cooling system: the sun. Mikler believes it is the only system of its type in North America.
The mandate handed to the designers was for a LEED platinum building with the highest energy efficiency possible, using on-site renewable energy sources where feasible. The requirement for renewables led to a solar system for space heating and domestic hot water heating. Then the design team decided to find a way to use the system year round.
"We looked at the option of absorption chilling because the building cooling load follows the same distribution pattern as the solar radiation," says Mikler. Simply put: on hot sunny days when you need the cooling the most, you also have the most (solar) energy available to power the system.
Mikler says absorption chillers also make sense in situations where there is "waste heat" – thermal energy produced as a by-product of some other process. Examples include heat generated by solid waste incinerators or industrial processes, or by electrical generation plants that burn fossil fuels.
"They typically don't utilize the waste heat for anything; they just reject it to the atmosphere," says Mikler. "So the electricity is created with less than 30% efficiency. But if an electrical generation plant is combined with a DE [district energy] heating system during the winter and a cooling system with an absorption chiller scavenging the heat to generate cooling capacity and distribute it, that's the way to go."
With the price of electricity generally low at present, Mikler says the capital cost of solar-powered absorption chilling is likely to keep it in second place behind conventional electrical-compressor air conditioning systems. The community centre system's payback period is roughly 15 years, with all of its space heating, domestic hot water and cooling functions factored in.
Absorption chilling is also a bulkier technology than compression, making it less feasible for tight spaces. But with rising energy costs, Mikler expects absorption chilling to start getting new attention, especially in settings where there is waste heat – or steady power from the sun.
"In terms of a new technology breaking through, once you have one, and it's done properly and working properly, it helps move the application forward," he says. Cobalt will fine-tune the system at the Southeast False Creek Community Centre this summer, when the hot summer sun makes it possible to calibrate its operations. Meanwhile, Mikler is already talking to a client in California – where there's no shortage of solar energy – about a similar installation.
"We choose to push the industry into this [energy efficiency] direction," says Mikler. "In areas where there is a continental climate – Edmonton, Calgary, the Prairies, the southwest U.S., California – this system would work really well. If there's a client with an appetite for innovation like this, we'll take them where they want to go."
Nina Winham is a Vancouver-based freelance consultant and frequent contributor to bchydro.com.
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