Why are Ontario electricity carbon emissions so low? Introducing the CIPK: the most important number in clean electricity

What is the most important number in clean electricity? It is the carbon intensity per kilowatt-hour (CIPK): the total amount of carbon dioxide, or CO2, in metric tons, emitted by the emitting generators feeding the grid, divided by the total amount of electricity generated, in kilowatt-hours. As you can see in Table A1 on the left-hand sidebar, total grid generation in Ontario in the last hour was 15,723 megawatt-hours, and total carbon emissions were 374 metric tons. Therefore, the CIPK is 23.8 grams CO2 per kilowatt-hour. (To do this calculation, first convert total megawatts, or MW, to kilowatts by multiplying by 1,000; and convert total metric tons CO2 to grams by multiplying by 1,000,000. Then divide the total grams of CO2 by the total kilowatts.) As you can see in Table A1, there are two main CO2-emitting fuel types contributing to Ontario’s grid, gas and coal. Gas and coal are mainly why the CIPK is above zero.

Electric light rail, the cleanest urban surface transportation. Can it run on renewable energy like wind and solar? Not a chance. It is only viable with reliable electricity. And the only clean reliable electricity comes from nuclear and hydro plants. In Ontario, only nuclear is expandable.

And as you can also see, the three main zero-emitting fuel types are nuclear, hydro, and wind. Of these, nuclear contributes by far most of the megawatts. Without nuclear, Ontario’s grid CIPK, and its hour-by-hour grid CO2 emissions, would be more than three times what they are right now. Table A3 on the upper right sidebar shows what Ontario’s hourly electricity CO2 would have been with allegedly “clean” natural gas.

Nuclear is therefore the biggest reason why, for example, subway and streetcar travel in Toronto is so clean. Subways and streetcars are electric powered. The cleaner the electricity, the cleaner the subway/streetcar ride. More nuclear means a cleaner subway or streetcar ride.

Now, the question is: would you like to see Ontario’s CIPK drop permanently? If so, from Table A1, it is obvious that more nuclear would achieve that.

I stumbled across a very interesting website page the other day. It is from the Toronto Environmental Alliance, and it gives an excellent rundown of the environmental benefits of electric light rail transit (LRT). At one point, however, the page says that electric rail vehicles produce “no local emissions, since they are powered by electricity, and can be run on renewable energy like wind and solar.” The first part of that quoted sentence is bang on, but the second is clearly not. Any electric transit must be powered by reliable sources of energy. Wind, as I mentioned a few weeks ago, stopped being commercially viable in the mid-1800s. It was because it was simply too unreliable. Little has changed with global wind patterns since the mid-1800s. Wind was not reliable then, and it is stil not reliable.

For LRT in Toronto to be clean and reliable, it must be nuclear powered. That means adding nuclear capacity to our grid, to force Ontario’s CIPK to go down. If we allow our nuclear fleet to languish, or if we shifted nuclear generation to gas (the “cleanest” fossil fuel), then our CIPK would nearly three times what it is now.

How did I arrive at that? I replaced the total CO2 in Table A1 with the figure in Table A3 in the upper-right sidebar, and then re-calculated the CIPK. Table A3 is a counterfactual, which represents the tons of CO2 that would have been dumped into the air in the last hour if Ontario’s nuclear fleet were replaced by gas, as some “environmentalists” have advocated.

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7 years ago

This is a great little educational post perfect for teaching about energy in the schools. I hope some teachers discover your great posts.

Joe Schiewe
4 years ago

Why use natural gas, oil or biofuel at all. I would hope the priority access to the grid would be hydro (maintain proper flow for fish), nuclear (high capacity), solar (to reduce daytime peak), wind (still low CO2), natural gas (cleaner emissions), biofuel (barely better then oil/gas) and then oil/gas.

[…] In Ontario, it is prohibited to generate electricity via burning coal. In 2000, Ontario’s electricity generation mix was the following: nuclear 37%, coal/oil 29%, hydro 26%, natural gas 7% and renewables 1%. In 2015, the generation mix was Nuclear 60%, hydro 24%, gas/oil 10%, wind 6%, with biofuel and solar making up the rest. However, this has presented series financial issues, namely nuclear refurbishment and current grid operations. The Ontario electricity grid currently emits well under 100 grams of carbon dioxide per kilowatt hour (CO2g-e/kwh). This is also sometimes referred to as carbon intensity per kilowatt hour (CIPK). […]

Naomi Bloch
4 years ago

Interesting article. I am confused by the statement, “As you can see in Table A1, there are two main CO2-emitting fuel types contributing to Ontario’s grid, gas and coal. Gas and coal are mainly why the CIPK is above zero.”

Per your table, coal is no longer a contributor in Ontario, is that right? I hope you’ll see this note and edit the article to clarify this point. It’s pretty confusing to readers, particularly those not familiar with Ontario. Best.

4 years ago
Reply to  Naomi Bloch

thanks for your note. Coal was indeed phased out — in May 2014. The article was published a year earlier, on a day on which coal plants generated nearly 10 million kilowatt-hours.