Solar Hot Air – Project #3

Technically this is my second solar hot air furnace but my 3rd renewable energy project – at least that Ive blogged about. So to the pictures, first you see the box, covered with aluminum foil, painted flat black with the BBQ high temp spray paint.. Then like last time I cut the holes out of the bottom of the cans with a can opener, left the tops intact, the smaller holes create the resistance to slow the air down and allow it to warm up a bit before getting sucked all the way through.

Finally I got the fan on, I used the one from my original small solar heater, its not defunct… Destined for the trash. It worked flawlessly for its whole life. The biggest issue was trying to keep it in the window :/ It would always fall out, I’ve have to tap it and wedge it in. Thats the downfall. Its also a bit noisy with that little fan spinning at such high RPM. I need to find a low voltage 12cm one like computers have, though often they draw too much power and I only want to put one 3watt solar panel on the unit. I think, when the sun is shining, that this unit will heat a room and keep it at a decent temp. Hey, its better than no rooms heated for free 😉 I like to think that it helps generally with the temp of the upstairs which during winter is always cooler. For various reasons, one large reason is that its not insulated well. Insulation would go a much farther distance keeping the house warm but there aren’t as many options for that, especially none as cheap as building a pop can furnace!

I could buy a ‘commercially’ made unit (still using pop cans) for around 2000 bucks I believe, it attaches to the side of your house, its a 4×8 panel. I’d love to do that, but with my own if Lindsey was ok with it. She isn’t keen on putting such a large black object on the side of the house…

One other thing you’ll notice about my solar units, they aren’t sealed at all. Less efficient for sure but then,… any heat that comes off that whether it gets around the cans or through it end up in the room so I’m not real concerned about sealing it and getting the box really cooking. Really not sure how much of a difference that would make since like I say, the unit is inside all the time anyways. Definitely needed for an outdoor unit though!

Going forward, I don’t really think I”ll make one any bigger, they take up window space which Lindsey doesn’t like either 😉 I suppose its nice to have some natural sunlight streaming in even though its not the most efficient way to collect heat. Considering how much of a dent, or the lack there of that it makes in our heating bills, its not a large concern. One unit is a good test and this is of a decent size that return is a lot better and its sized just to fit in the width of the window.

I might do a follow up on this one if I can get some metrics on performance, Though it may just end up being similar to the smaller one where I can feel lots of heat, but just don’t really know how much of a difference its making in the room. We’ll see…

And next, my next project is going to be a wind generator. I have some ideas for getting some old bicycle wheel generators and an old bike and making a turbine out of said old bike. Saw some interesting designs just using upside down bicycles since the axles, bearings etc are all there, and they are relatively light etc. My problem though is I need to find a use for the electricity. The solar hot air is great because I know its contributing to the heating gof the house. With wind,… there is less then I can do with it. Unless maybe I bring in the power and plug it direct to the hallway light which is on all the time anyways. My thing is that if I can’t make use of it, if it can’t contribute something in terms of savings then is it really worth my time. But thats funny saying that cause I do a lot of things that don’t otherwise contribute to life like that, they are just hobbies 😛 Anyways, for wind, I really want to do something but I need to find someway to use the power. Hm,.. a security light outside, now thats a good idea since we burn electricity outside for that which consumes about 800 watt hours a day of electricity.

For fun, here is the math. 14 watts x 3 bulbs, x 6 hours of ON time a day for each bulb. Now our daily kW usage is 10 to 12. So thats 12,000 / 756 Watt hours = approximately 15%. 15% of our daily electricity bill is our outside lights. Very interesting now that I did that math… That saves us about 1800 watt hours, or 1.8 kWh at $0.155 per kWh. So daily that adds up to about $0.28 cents a day, which over the month, $0.28 x 30 days in a month = $8 or abouts. It sounds high that we could be saving almost $10 a month just by having those shut off or using wind energy. This is a subject for a whole other blog post if I figure out that this is actually true…

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