Urban Cogeneration: Old technology in New Applications
Cogeneration is an idea as old as the electric power plant itself. In 1882 Thomas Edison’s Pearl Street generating station provided both electricity and heat to lower Manhattan. The leftover steam from the coal-powered turbines was piped to homes and businesses. Despite the inherent efficiency you get from stacking functions, this type of design was cast aside in favour of large remote centralized electricity generating stations.
And while these massive power plants might generate electricity at a cheap price in isolation you need a massive network of wires and infrastructure to get that electricity to the consumer. Also, two thirds of the potential energy you could have extracted is lost up the smokestack as waste heat.
Now, cogeneration has returned as a viable technology. Pulp and paper, manufacturing, oil sands operations all found that given their demands for heat cogeneration made sense.
In Alberta there are 4,000 megawatts of cogeneration capacity running. The largest cogeneration plants are found in those industrial applications, but the technology has scaled down too.
One small 370-kilowatt cogeneration plant provides heat and power for the east tower of Oxford’s Centennial Place office building in downtown Calgary.
"If you’re under 150 kilowatts you’re going to be over a five year payback, and if you’re over a 150 kilowatt you’re going to be a three to five year payback”
Dan Cloutier, the president of Power Eco-Systems, the company that installed the unit, says the basic mechanics of it are similar to a car’s.
“Most of the energy that goes into your car is lost as waste heat. So what we’re doing is instead of turning a driveshaft, our engine is turning a generator and generating electricity, and then we’re capturing that heat off the engine jacket as well as the exhaust.”
Cloutier says there’s a three to four year simple payback on this system and that’s including installation costs.
The other bonus is that though these run on natural gas, because they’re so much more efficient than giant power plants they emit dramatically less greenhouse gas, making them eligible for LEED points, BOMA Go Green points and a variety of other programs and incentives. This building has a LEED Gold certification. To go even greener they can be run on biomass, biogas or biodiesel.
This technology has matured to the point that anyone with a big enough heating or electricity bill should consider it. And while the systems go down in size to five kilowatts (one house-sized system Cloutier set up cost $24,000) the bigger the system is the better bang you get for your buck.
“If you’re under 150 kilowatts you’re going to be over a five year payback, and if you’re over a 150 kilowatt you’re going to be a three to five year payback,” says Cloutier.
In a carbon-constrained world where every unit of energy we consume should be doing as much work as possible, technologies like this will thrive.