Combined heat and power: friendly to the environment, or just the gas industry?

Two weeks ago, on The Agenda with Steve Paikin, I participated in a debate on the pros and cons of nuclear power expansion in Ontario. One of the other debaters, Dave Martin of Greenpeace, suggested that industrial power users could reduce their environmental footprint by using combined heat and power. Also called cogeneration, combined heat and power (CHP) involves using heat from one source to provide both electricity and space heating to the same facility.

The concept of combined heat and power appeals to some people because it implies efficiency. We use the same heat to do two jobs: wouldn’t this produce less emissions than separate processes? It sounds like a no-brainer.

Well, it’s a brainer. CHP almost invariably means using natural gas. Emission intensity from generating power solely with natural gas is more than double that of the power coming from Ontario’s grid (550 grams per kWh for gas, versus 222 from the grid; see Environment Canada’s GHG Inventory).

This means that for CHP to work in Ontario, a facility would have to reduce space heating requirements drastically in order to reduce the total emissions that result from separate processes. These requirements would have to be reduced even more drastically if and when Ontario adds power from new nuclear or hydro plants to its system.

So CHP looks good at first glance, but falls down in jurisdictions where the emission intensity of electricity is already low. You still need way more fuel in CHP than you would if you generated power or heat separately. This means that gas-based CHP is only favourable, emission-wise, when you compare it with power or heat generated separately entirely with fossil fuel.

Which means in turn that CHP might work in jurisdictions like Alberta or Ohio, where electricity is generated primarily using coal. But as I have stressed on this blog, this doesn’t apply to Ontario. More than three-quarters of our electricity comes from emission-free sources. And CHP would be an obvious non-starter in Quebec, British Columbia, Manitoba, or Newfoundland-Labrador—none of these provinces has power emission intensity over 31 grams per kWh.

Nice try, gas industry.

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Rod Adams
16 years ago

I like cogeneration, but I like it better when the heat source is a reactor, not a gas burner.

The gas industry has done some excellent work in making people more aware of the technical advantages of the Brayton (gas turbine) cycle and of the reuse of the heat for either combined cycles (Brayton topping cycle with Rankine (steam) bottoming cycle) or cogeneration. They have also done excellent promotional work to make people more aware about climate change and the need to reduce carbon – they often talk about their advantage over coal.

The challenge for the gas industry from an honest debate perspective is that a high temperature atomic reactor is fully capable of replacing the gas combustors in that cycle – making it possible to have a ZERO emission Brayton cycle and one that does not consume any natural gas at all.

The gas industry marketers know they cannot prosper if that information becomes widely known.