You can think of temperature, besides quantifying everyday words like hot and cold, as being a rough measure of how quickly the constituent particles of a substance are zipping around. If you had a microscope powerful enough to look at individual water molecules at room temperature versus water molecules at the point just before they break free of each other to become steam, you’d see that on average the room temperature molecules are moving around more sluggishly than the ones at the boiling point.
Chemical reactions, from the dramatic to the mundane, all proceed at a rate that is roughly proportional to the chances the molecules have to meet and interact. That is, chemical reactions proceed at a rate that is proportional to temperature. High temperatures mean the molecules are moving much more and thus have more chances to meet another molecule to partner up with. You can say the converse for cold temperatures. And this happens for all sorts of reactions, including those that take place when a photon of light interacts with the crystal inside a solar panel to free an electron and make electric current.
Colorado’s bitter cold snap prior to Christmas, combined with a series of tweets by Independence Institute energy researcher Jake Fogleman, got me wondering exactly what kind of effect the extreme cold had on my own solar panels. I wasn’t expecting a malfunction because there aren’t any moving parts and the panels are rated to survive cold snaps. I just wanted to know how much a severely cold day would set back my solar production. It turns out that, despite my hopes to the contrary, I wouldn’t ever have the ability to do anything like a valid comparison; there were a lot of confounding factors between the blowing snow, off and on cloud cover, and the howling winds that left some panels scoured clean and some covered in snow. I can’t with any confidence draw a conclusion from that.
Zooming out (in time but not distance) gave me an interesting comparison that I felt was fair, however. Pulling a year-to-date report for my home’s solar array, I could clearly see a steady decline sliding from summer into deepest winter of about half. That is, my solar electrical production now is about half of what it was in July/August. Again, I’m not surprised and nor am I disappointed (conversely, I did puff up with pride to note that the solar panels I installed actually stayed attached to my roof in the horrendous gusts of wind and that none of the flashings have leaked with the insidious slow drip of melting snow as opposed to rain). My system is doing exactly what it was expected to do. It will generate surplus electricity in the summer and will run a deficit in winter, with (I hope) the balance titrated just right to make my net consumption over a year be zero. I could, by adding panels, make more energy in winter to get my production up above my consumption, but I’m on a grid-tie system with a net meter. I can’t ever cash out the giant surplus pile of credits I’d rack up in that situation or store the energy in batteries for later. Whether used in my home or sent back to the grid, once the power I generate is made, it’s gone.
I don’t know much about commercial-sized solar arrays, but my guess is that they are experiencing a drop off in solar production with winter’s shorter days and colder temps too. There’s nothing unique in the physics of the situation to tell me there would be a radical difference. You could reasonably argue that the drop off would be less for a more sophisticated system with tracking arrays. Designers could also, as I have the option of doing, overcome a drop off by the brute force method of adding panels (with the commensurate increase in summer production). But there’s no getting around the fact that lower temps and shorter days lead to a drop off in all solar production, no matter the scale of the operation. There is also no large scale way now to bank this generation for later use. Like my system, when it’s generated, it’s gone.
One of the more compelling tweets by Mr. Fogelman was a time series of the different kinds of energy Xcel generated as the cold snap of December 22nd and 23rd wore on. In it you can see that, after an initial burst of generation by wind as the storm literally blew in, Xcel moved us more and more to coal power to keep the lights on and the heaters working. Bear in mind that I don’t think it’s right to conclude from this graph that wind or solar couldn’t have worked during the cold snap–I at least don’t know enough to feel comfortable making that claim. I mention it because, when put in concert with what I noticed about my own solar production, it points to something that we should be talking about more than we are.
Weather and seasonal patterns will (repeat will) affect renewables’ ability to make electricity. Even assuming you could get enough renewables over time to average out to our state’s consumption, we have no viable, state-sized storage solution to keep that power in times of low generation. What fills the holes we’ll inevitably have in winter if we heedlessly jump in with both feet on renewables? Said another way, if we have no more coal to ramp up in a future graph of our state’s energy mix, what then?
We better have something or we’d better reconsider the rapid pace of change our legislators and Governor Polis are forcing us into.
Cory Gaines lives in Sterling on Colorado’s Eastern Plains.