Keeping drinks cool with the Peltier effect!

This past week—in the height of southern hemisphere summer—I put on my jacket to go take a walk outside, while shivering in the frigid summer air.

It's been an odd summer here in Melbourne this year. Apparently it's a La Niña year in the Pacific ocean, which means a colder, wetter, summer. And it definitely has been; I think two weeks ago—in the middle of February, typically the hottest month of the year—was the first time this summer it was warm enough to go an entire week without wearing socks. Then a cold front came through and I've been shivering while dressed in warm clothes this entire past week. Imagine it being cold enough in central California in August to need to put on a jacket to go out for a walk, and you'll get an idea of what it's like here.

I mention this because, back in November, when we had our first signs of winter relinquishing its fell grasp and an occasional day where it was actually warm, I started thinking about working from home over the summer. At that point I didn't know it was going to be a cooler summer; in past summers since I've been here I've seen days where it hit over 43 °C/110 °F. (This summer I think the highest I've seen is 32 °C/90 °F, though that's still plenty hot enough when it barely cools down more than a few degrees overnight.) Thinking that the expected upcoming heat would be more tolerable if I just had something cool to drink during it, I started thinking about ways to keep a drink cool. The obvious first choice was ice cubes, but ice always waters down your drink over time, and I prefer to sip on something cold over time rather than guzzle it to avoid it getting watery. I started wondering if there were anything more modern than simple ice cubes, and did a little digging.

I first discovered whiskey stones, which are basically re-usable ice cubes made of stone or metal: you put them in the freezer to cool down, then put them in your drink. Not bad, but then I had a thought: wouldn't it be neat to use a thermoelectric Peltier cooler to directly cool down a drink on your desk? If you haven't heard the term before, a Peltier cooler is a device where, by putting two different metals together and running an electric current through where they join, one side cools down by giving up its internal heat to the other side. (It's not a new discovery, having been discovered by Jean Peltier back in 1834, but Peltier coolers are still not something most people will ever likely have come in contact with.)

I wasn't sure such a device for home use existed (and had no idea what to call it even if it did), so it took some stumbling around with Google and Amazon to find one, but find one I did! In fact, I found several different takes on the idea by several brands, though all following more-or-less the same pattern.

Now, while it looks like these devices have been on sale for at least a few years or so, they're still new enough (and niche enough) that I don't think they really have a settled name yet. The one I bought had the word-salad title “HSTYAIG Portable Mini Refrigerator Electric Summer Drink Cooler Kettle Drink Instant Quick Cooling Cup Home Office Cold Drink Machine Small Appliance Kettle (Traditional),” but let's just call it a “cooling cup” for short.

But what is it, exactly? Well, it's an electric device comprised of a plastic base holding the electronics with an aluminum plate in a depression on top in which sits an aluminum cup, and it looks like this:

Device on the right, cup on the left. You can see the cooling plate in the depression.

It's got a single capacitive on/off button on the front, and that's it as far as interactivity goes. The aluminum plate is the cold side of a Peltier cooler, and when you turn it on, the plate cools down (and draws heat from the cup) and a fan blows out heat from the hot side of the Peltier cooler (inside the device).

And does it ever cool down fast! Literally a few seconds after turning it on the aluminum plate is cool to the touch. After a minute or so it becomes painfully cold, and when I let it run for 20 minutes as a test the first time I tried it I saw tiny ice crystals forming on the plate, despite it being 20 °C/68 °F in my room at the time. I'm used to refrigeration, but heat-pump refrigeration takes a while to cool things down. In comparison, a Peltier cooler feels downright magical with how fast it works. Now, despite the impressive cooling performance of the plate by itself, in practice it'll struggle to cool a room-temperature drink down. Water has a surprisingly high thermal inertia, so if any water-based drink isn't already cold it'll take a long time to get cold. If it is cold, though this thing does a phenomenal job of keeping it cold. (In fact, the last few sips can be even colder than when it came out of the fridge!)

Although I got my cooling cup at the end of the November, I've been holding off on reviewing it here while waiting for it to really warm up for the summer (when it would make sense to talk about something meant for cooling drinks). As that appears not to be happening this summer, however, I might as well post about it now. I've had several months to try it out, and it works like a charm. Pour something cold into the cup, press the button, and it'll keep it nice and frosty for as long as you like. It feels like a very modern solution to the problem of keeping a drink cool, even if the technology to do it is approaching 200 years old at this point. Admittedly it's hardly the biggest problem out there, but as a solution to it I can heartily recommend a “cooling cup.” (Although, if these ever catch on, let's come up with a better collective name for them.) A hui hou!