I’ve had plenty of people asking me lately what’s going on with Project HMX, and unfortunately, progress on it has stalled for a number of reasons. Chief among them are the other projects that have taken time away or quite literally blocked me from getting to the HMX. Over the weekend, I got one of those projects out of the way.
Ever since I built my first soda can solar heater three years ago, I’ve received plenty of input on how to improve the design for better heat output. For that reason, I never hooked up the first one – in fact, I gave it away to a friend – and set about building a bigger, better version, suffering through three cold winters in the garage. I started out by looking for a sliding glass door, which I found locally for free, then took all my measurements from that. Minus space for the insulation, the sliding glass door allowed for 180 cans (versus 50 for the first version), which took a while to accumulate, given that I’ve sworn off soda the last few years.
Aside from the addition of the insulation, the build went pretty much the same as the last one: Build box, seal it up, drill holes in cans, stack them, paint them, drill inlet and outlet, use shop-vac parts to funnel air in and out. Because this box turned out much heavier than the last, PVC pipe wouldn’t do for a stand, so I popped some Tractor Supply wheels on it and built a hinged stand from 2×4s.
Recall that the first version pushed out a paltry 15 degree temperature differential. Weak. I took multiple readings from this second version over the weekend and recorded temperature differentials up to 120 degrees in full sun and up to about 80 degrees in a mixture of sun and clouds. I plan to continue taking readings from the heater over the next few weeks and in varying conditions to get a more complete idea of its performance, but it appears I’ve achieved success with this second version – sure, it’s not hot enough to boil water (though it got mighty close), but it should provide plenty of heat for my garage this winter, allowing me to continue working on cars in the chilly winter months.
Thanks to everybody who offered input over the last three years, and please continue sharing your own soda can solar heat projects!
