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Week Nineteen - Summer Cooling

Average Canberra house summer power = 396 kilograms CO2e per person per year

· Weekly experiments

My preschooler

- The air conditioner broke at daycare so I hibernated. Ponies like me always hibernate during summer.

Me

- Smart ponies. Best climate change adaptation ever.

It's getting hot in here

Just when we need our power most, it will fail - even if it's coal-fired. My child's daycare had to cope during a record-breaking heatwave without cooling when their overburdened air conditioner broke and Canberra's rental air conditioners ran out. The kids survived four consecutive days over 40 degrees, apparently through hibernation.

Climate change isn't coming. It's here. Canberra is predicted to be one degree warmer by 2030 and over two degrees by 2060. So do we switch on the coal-fired air conditioner and savour the irony, or is there a better way?

More heat = more heat

Hot summers land us in an artificial feedback loop. As the temperatures rise, we use more power to cool our workplaces and homes, to keep our gardens, crops and stock alive and to repair the damaged infrastructure like melting bitumen. We also get more (un)natural disasters, like droughts and bushfires, which require more power to fight, flee from or fix up afterwards. That power churns out carbon dioxide and equivalent emissions (CO2e), which accelerates climate change and causes hotter summers and more droughts and bushfires.

The good news is that, unlike natural climate change feedback loops, we can already minimize this one.

How much CO2e?

My meter showed we used 109 kilowatt hours of electricity this week, which generated around 100 kilograms of CO2e. Over twelve weeks of summer, that would generate 1.2 tonnes of CO2e or around 400 kilograms per person.

This is a close match for the average 3-person household in my suburb. We're not doing too badly as I work mostly from home, so I power the house seven days per week. In many Canberra families, everyone's out during the day, so daytime power usage drops. But I'm sure my house can improve.

Not all of the electricity used during summer goes into cooling the house. Some of it is used for lighting, watching television, running the computer and other activities. For the sake of simplicity, I'm looking at my overall electricity readings and how much they drop, but I won't get to zero even if I switch off the cooler altogether.

Summer cooling experiments

I'll spend the next two weeks looking at better ways to cool a house.

1) Higher temperature / smarter settings. When I looked at winter heating, I turned off our heater for a few days. I pitched the summer equivalent, but my partner nixed it. He felt it would be 'psychologically dangerous' to turn off our cooler. After this week's heatwave, I agree with him. Instead, I'll turn our cooler off for a couple of days when my family are out and I'll start programming it properly the rest of the time because, like many people, we've never bothered to learn. We simply dial it up or down as we go, which is not efficient.

2) Different methods. Depending on your living situation, you might use any combination of air conditioning, evaporative cooling, electric fans and passive cooling. I'll run the numbers to see how these compare in different situations and make a few changes around my house to see what works.

A note on power sources

The above figures are based on emission factors for the ACT / New South Wales grid from the 2018 National Greenhouse Accounts Factors. Actual CO2e from electricity depends on the source you're using, which might be your own power or might come from the grid. For those reliant on the grid, emissions differ state by state. For instance, the Tasmanian grid uses 93% renewables (mostly hydro) and generates 0.22 kilograms of CO2e per kilowatt hour of power. The Victorian grid relies on coal and has less than 25% renewables, so Victorian power generates five times more emissions than Tasmania (1.16 kilograms CO2e per kilowatt hour).

My house has rooftop solar panels, but I'm using grid power figures. Our solar electricity gets fed back into the grid so anything we save displaces someone else's grid power. In any case, we're still using power from the grid as our solar system doesn't cover all our needs. I'll look at the impact of rooftop solar later on when I spend six weeks on electricity.

Spreadsheet calculations, notes and data sources in the 'Notes' section, Week Nineteen.

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