Think about how reliable electricity is, especially if you compare it to getting hot water from a tap. That reliability comes at a price. Let’s look at electricity use throughout the day in a typical residence. We aren’t nocturnal so it makes sense that we use most of our energy between 6 AM and 11 PM. We work an eight-to-five schedule, so there is a spike in the morning around 7 AM as we get ready for work and another in the evening about 7 PM as we get home, turn the lights on, cook dinner and use electronics.
Then there is use that depends on the season. While there are large swaths of Canada that don’t require air conditioning during the summer, here in the Okanagan we like summer weather to stay outside. Refrigerated air uses a whopping amount of electricity and follows the rise and fall of the outdoor temperature. Electric demand in the winter is almost as much as summer, with most of that electricity going for lighting and heating.
Refrigerated air uses a whopping amount of electricity
Spring and fall are the ideal seasons: little heating or cooling is necessary and electricity clearly shows the 7 AM and 7 PM bumps.
Unless you live in a Net Zero or Passivhaus your electricity demand never falls to zero. Even in the dead of night your AC or furnace is running, the hot water tank is on. This load is called the baseline and is shown in the figures as a dotted line.
Your electric provider has three resources to draw from: 1. Power plants that provide the baseline load — they run steady twenty four hours a day and seven days a week. 2. Dipatchable power (sometimes called peaker plants) and 3. Buying power from a nearby grid that has a surplus. Utilities focus on making baseline power as cheap as possible, using hydro, nuclear and sometimes coal for baseline loads. Dispatchable power is expensive: the utility is building and maintaining plants (natural gas or hydro) that are only needed sometimes.
Since 7AM and 7PM electricity is more expensive than midnight, shouldn’t we be paying more at times of high demand? Traditionally residential customers pay the same price for a kilowatt hour of electricity no matter what time of day they use the power. Commercial and industrial electricity users have “time-of-use” charges where the electricity they use at peak periods costs more than electricity used in the dead of night.
There are two ways of making the electricity system more efficient: using less energy and/or using more solar. That solar can be privately built solar on rooftops (distributed solar) or utility scale solar. A great example of the impact of energy efficiency is the type of summer air conditioning you install in your house.
There are three kinds of devices that can make air cooler in your house: refrigerated air, heat pumps and evaporative cooling. By switching from refrigerated air, which uses a lot of electricity, to heat pumps or evaporative cooling we can bring the overall summertime load down by a lot.
Solar power is actually a pretty good match to electricity demand
Solar power is actually a pretty good match to electricity demand. During the summer we have more hours of daylight and the rays of the sun are more direct, matching the curve for air conditioning demand.
California has an interesting solar problem (someday I hope to have this problem in the Okanagan). It’s called the “Duck Curve”. As you can see from the graph, solar has shaved the peek at noon, but the pre- and post-work bumps are too early and too late for solar to contribute. This leaves a weird shape that looks like a duck. This decreases the need for mid-day peaker plants but the steep rise can be a strain on the distribution system. There are a few ways to deal with it. Solar arrays can be pointed slightly west to catch more late day sun. Storage, such as the Summerland Solar+Storage project can provide electricity after the sun has set.
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Kristy Dyer has a background in art and physics and consulted for Silicon Valley clean energy firms before moving (happily!) to sunny Penticton. Comments to Kristy.Dyer+BP@gmail.com
Kristy’s articles are archived at teaspoonenergy.blogspot.com