Monday, January 4, 2016


The theme of this blog post is evacuation.

As I mentioned in the last post, it's summer and it's hot. Some nights, we get a cool change, but the breeze is very light. In winter, I built a rooftop solar collector and pumped solar heated air into three rooms using ducting. This system worked quite well, but it would have been better if the indoor vents were not in the ceiling but were instead in the floor. There is an advantage to having them in the ceiling though, and that's when we want to pump hot air out of the house. To do this, all I've done is change the configuration of the thermostat: previously, it switched on when the temperature was above 24 C, now it switches off when it is below 26 C (this is measured at the solar collector, which is at about 80-degrees from horizontal so still gets some sun) so it basically won't switch on during the day.

I've also reversed the fan (I bought an AC fan which only works in one direction -- others may want to consider a DC fan which is reversible with a switch), and opened the (in-duct) backflow preventer with a bulldog clip (the backflow preventer stops warm air from flowing out of the house during winter). This works really well for sucking hot air out of the house in summer -- probably better than the system works as a winter heater. It really lets us capitalise on cooler nights which, with a double brick house, means keeping things cooler during heat waves very cheaply. The fan uses about 50 W, so to run it overnight (when our solar PV isn't producing) uses .05 * 8 = 0.4 kWh. To improve it, I will add better control so I can easily turn it on and off from within the house.

On to a different type of evacuation, I've ordered a urine diverter so that I can build a composting toilet (that was my Christmas present for myself). I went for the we-pee, which costs AU$66 delivered (I don't have it yet). That seems a fair bit of money for a little bit of plastic, but I thought it was worth doing this properly. My plan is to build a bucket-based composting loo using 20 L plastic buckets, and just add in hay/mulch/etc as we go. It's all a bit experimental, but I'll write about it as it goes and let you know.

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