Towards a better tinyhouse

Inventing to freedom?

Rainwater (snow) collection during winter

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There is an obvious problem with rainwater collection systems: During winter, the precipitation has to be gotten off the roof somehow, and melted. If you have a high pitched roof, getting it off is no problem, but a lot of tinyhouses have a relatively low pitch.

To solve this problem. I was just thinking you could have things set up so that the roof could be rinsed with hot water, and the water+snow slush slides off the roof, to remove the snow in an automated way. You need to melt the snow anyway, so it doesn’t take that much energy, all things considered. One potential problem is that diverting the first bit of water that comes off the roof, which is usually done with rainwater collection systems, might not be easy. But you could just filter the water well instead.

Another way I was thinking would be to put a sheet of teflon on the roof, though that would not be cheap, and I don’t know how well it would work.

Suppose you go with the rinsing, how much energy do you need? (which could come from a solar collector) Well, the snow on the roof is just being mixed with the water first, and it will be at the ambient temperature, so you need to provide the energy to raise the temp to 0 degrees, so the water component of the slush mix stays liquid. If it is -10 out, that’s 40kj per kg, so that’s quite a bit, 11 Whrs, but that is totally supplyable with modest a solar thermal collector. Suppose the slush is 20% liquid water and 80% solid when it comes off the roof, the water going onto the roof, which must contain the necessary energy, must be about 40 degrees, theoretical minimum. Some energy gets lost to the roof, a bit to evaporation, and some to the ambient air by convection, but I think you could manage that without too much difficulty. As long as water does not freeze to the roof, I think it will work. And I don’t see that being a problem.

But the roof needs to be thoroughly waterproof, though, you would want the plastic membrane thing sometimes used under the metal/shingle roof. Maybe a hot water loop under the roof would be a better operation. Just in case it isn’t clear, the snow-collection happens in batches, after the snow has accumulated a bit.

Then you need to catch the snow as it comes off, maybe just with a long, big trough where the eaves trough usually is. Waste heat from the house, and whatever solar power is needed, would be directed to this trough, the snow melts and the water and collected and stored elsewhere. You might have the sides insulated, and an insulated lid on the trough, which would automatically close, or open, when collecting snow, at the right time, because the water inside needs to be heated to above 0, and the ambient temp is lower than that, so….


Written by gregor

October 11, 2010 at 00:06

Posted in Uncategorized

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