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Cities tap earth, sea and sewage for district energy

By District Energy posted 05-31-2022 17:02


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Earlier this spring, contractors in San Jose, California, broke ground on a 1.3-million-square-foot tech hub complex with more than the usual complement of green features, beginning with its name: Park Habitat. Targeted at office and retail tenants, the development team, led by Vancouver’s Westbank, says the downtown high-rise project will be fitted out with a landscaped green roof, indoor and outdoor “pockets of nature” and naturally ventilating exterior walls and windows to prevent excessive solar gain. 

Out of sight, meanwhile, the towering net-zero complex incorporates an entirely electric community energy system (a.k.a. district energy) designed by another Vancouver outfit – Creative Energy, the descendant of the city’s district heating utility, which was founded in 1968 with a mandate to pump steam through a network of pipes connecting buildings around the downtown core. 

As an approach to distributing energy in cities, district heating isn’t new; the earliest systems date to the late 19th century, in cities like Hamburg and New York. The benefits and economies of scale were obvious: individual buildings could buy their heat from the district heating agency instead of maintaining boilers in the basement. The problem was that district heating utilities – some municipal, others limited to campuses – tended to rely on dirty or carbon-intensive energy: municipal waste incinerators and fossil-fuel-fired boilers. 

In the 2000s, however, Toronto and other waterfront cities like Amsterdam and Singapore built district cooling systems based on the same principle: pipes linking clusters of buildings and using lake or ocean water as the coolant. As with district heating, property owners didn’t have to maintain expensive HVAC equipment, while local utilities benefited because these systems reduced loads during hot summer days when demand for air conditioning was high.

These days, district energy companies like Enwave, which built Toronto’s deep lake water cooling system, are drawing on a far broader range of low- and no-carbon technologies to make and distribute clean heating and cooling, including geo-exchange, electric boilers and heat pumps for recovering waste heat, including heat from municipal sewer mains. 

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