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Tuesday, June 29, 2021

120 Hours of AC - Excessive Energy Usage


The heatwave hitting the Pacific North West seems to have finally broken. This event set new record highs for many locations in the region. British Columbia set a new record for the entire country of Canada.

Some have called this event a "once-in-a-millennium" occurrence. This would likely true if we had a stable environment, but we've added a lot of energy into the climate system and, in a perturbed system, you see many unexpected results. We've entered into an era of "global weirding." 

Roads Buckling in Heatwave - via @wsdot_north

Several roads in the region buckled and cracked due to thermal expansion. The trolley cars of Portland had to shut down due to damage to the high power cables. Similarly, the light rail passenger train, MAX, shut down due to cable expansion and sagging. Much of Oregon has had drought conditions for the last three years. Then, compounding the problem, it was hit with temperatures higher than any that have ever been recorded in the area.  

For our little home, we had a few little challenges, but overall we were rather lucky. Some of our neighbors lost power for a few hours. This is not surprising given the load that all the additional air conditioner use caused. However, these outages were in small areas and short-lived. The Western Interconnect grid held up to this stress test far better than the Texas grid has held up to their recent hot weather. Kudos to everyone in the region that helps keep the lights on (and the AC running when we needed it most). 

Speaking of AC, our AC unit is sized for a typical Oregon summer. It is, however,  significantly undersized for extreme heat like this. Even with our AC running all-out, the temperature in our home slowly continued to increase throughout the day. As I write this the AC has been running for 120 hours, non-stop. And it looks like it will be running for at least another 10 hours. The higher highs this heatwave brought were bad, but the higher overnight lows were worse; they meant no relief overnight either. On a typical hot summer day, the AC will run about 16 hours, not for days straight.

Portland weather graph via timeanddate.com

We (and much of the region) are going to have a big power bill this month. Compounding the energy problem is that despite all the sunshine, our solar energy production was reduced. Solar panels have a preferred operating temperature; when they get too hot, their efficiency is reduced. For example on June 28th (one of the hotter days), we generated 49.4kWh. On a more typical summer day, we typically generate ~80kWh. This is a notable reduction in output at a time when we most needed it. Just another reason that you should oversize your solar PV system whenever you can (even if it results in some solar clipping on good days).

Have a great summer and stay cool!

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