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.

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