Thursday, December 22, 2011

Where does Ontario's electricity come from? (Winter edition.)

Lately I've been involved in some arguments about just how effective solar panels are at reducing CO2 emissions. That's a topic for another post and it will be an occasion for extended ranting--stay tuned--but in the meantime, the debate has forced me to go digging for some data on the composition of electricity in Ontario.

Ontario (like many places) has a bunch of different generators in its electricity mix; each of them has its pros and cons, and they get cranked up to meet demand at various times according to a fairly complex set of criteria. What I wanted to know is, what combination of generators is providing power, and in what proportions, at any given moment.

What I found was the time-series data, going back a month, for the output of all the major (over 10MW) generators in Ontario. The data is disaggregated by hour, so you can graph exactly how much of each kind of generation is contributing to the system during any given sixty-minute period.

So I did. Here are the charts for four one-week periods, starting November 19th, 2011 and ending December 16th.

First, the basics. These charts are for seven-day periods, beginning on midnight Saturday. Each day, you see a sort of double hump in electricity production. It's low overnight, ramps up to a bit of a peak around mid-morning, drops off a bit around lunchtime, and then ramps up to a higher peak in the early evening before dropping back down at night. It sort of looks like a graph of someone's heartbeat...

Since you can't really store electricity (well, you can, but not at this scale) that production curve is a pretty close match for the demand curve--how much electricity people in Ontario are using.

The humps are less pronounced on Saturday and Sunday (left-hand sides of the graphs.) That's because people are sleeping in, they aren't all making coffee and toast at the same time, and of course a lot of businesses are closed so they're not drawing so much power.

There's a ton of interesting stuff in there--so much that I'll have to break this up over a series of posts. Check back later.


  1. I saw an interesting item on Daily Planet a few weeks back, about compressing air in large underwater balloons at depth in Lake Ontario. Air pumped into the balloons during excess capacity, and subsequently used at times of demand. I tout it was a promising concept.


  2. That's interesting. Sounds like a good way to store electricity from offshore wind turbines.