How to have a
OUR OUTDOOR BATHHOUSE is just a formal version of a camp shower. A shallow tray of water sits up above you, lined in black (butynol), insulated and glass-covered.
It’s a pretty simple system: the sun pours into the water through the glass; when it’s hot enough you can shower below, conscience-free.
In practice, it has one big down-side: as soon as the sun goes down or the clouds come over, the water loses heat, and after three or four sunless hours, it’s lost too much heat for comfortable showering.
An insulated lid would improve the situation and put a lid on it, as it were. That would cope with the need for an ‘end of a long sunny day’ shower scenario, but what if you had a partly-cloudy day? Unless you’re up there opening and closing the insulated lid, the water is going to get progressively chillier.
In the spirit of decomplexification, I opted to avoid automatic opening/ closing mechanisms when designing our lid. That left the cloudy-day possibility of getting extra sunlight into the water during the sunny phases, a bit like pumping faster to beat the slow leak of a bike-tube.
The sun doesn’t transmit heat to us, just light. It’s the infra-red light we’re after, and the heat is the result of it speeding up electrons in whatever it hits, eg your skin if you’re sunbathing, or water in this case.
Catching sunlight is a matter of area and of concentration. I remember well the acrid smell of scorched school-shoe rubber under a focussed magnifyingglass, and the subsequent canings and detentions.
More catchment area is easy to organise – all you need is a mirror reflecting into the water. Even better, if the mirror is the underside of an insulated lid, you’ve just killed two birds with one stone as you get twice the sunlight into the water and have a lid to trap it there.
This idea took me off to the treasure-trove pile under the trees on our block, and I came back with an old shower-door, some Dexion angled steel used for shelving frames (it looks like over-sized Meccano) and assorted pieces of the possibly-useful kind.
Rather than a glass mirror – heavy and vulnerable – I opted for second-hand stainless-steel, marginally less efficient but much more likely to last.
The lid needed to hinge from the down-sun side of the water tray, so it needed a pulley up in space somewhere above. It also needed to tilt past the vertical to be useful in mid-summer, although the best outcome would be an adjustment for tracking the seasonal sun angle.
The Dexion steel made all of this easy. I used it to build a structure like a blackboard easel so we can adjust the length of the back upright to control the tilt. So far, so easy.
Power to the people
Some US $2.2 trillion of this will go on rooftop and other local PV systems, handing consumers and businesses the ability to generate their own electricity, to store it using batteries and – in parts of the developing world – to access power for the first time.