Monday, August 15, 2011

Build Your Own Solar Hot Water System

Last week, my job was to go to Baucau and provide solar power and solar hot water for a friend working in the Seeds of Life Program (agriculture). It was a great opportunity to put in a gravity fed solar hot water system which we are building here in East Timor from locally available materials. Just in case you wanted to build your own or were intrigued as to how I did it here’s my little explanation. Its a rip-snorter of a system really.
DSCN0306You’ll need a 44 gallon drum (204L general fuel drum), about 8 lengths of 1/2” plastic pipe, 4 lengths of 3/4” plastic pipe, a bunch of T-fittings and other plumbing bits, some 3”x2” timber, insulation, flat sheet metal, glue, screws and nails etc. Basically stuff we can buy here from the local hardware shop.

We made a rectangle frame of timber and nailed some flat tin on the bottom to keep the mice out – this holds the old drum.
To insulate the drum, we covered it with a mattress which the Timorese make out of kapok – its like cotton wool only from a tree. (In the old days they used to stuff life-jackets with it.) You could use old rags or an old foam mattress I suppose. The Timorese man I was working with was very confused about why I’d want to lay a perfectly good drum on its side, on the roof and cover it with a mattress!!! These white skin folk are truly crazy. By the end though, he was convinced that this was a new business opportunity for him as he could see that he could build solar hot water systems using things he could buy and skills he had. The only thing he lacked was the technical design which he learnt on this day. DSCN0312
This then gets covered over with a sheet of flat ‘tin’ (actually a sheet of zinculume roofing iron). You can see my metal working skills are at a rather fundamental level minus the ‘funda’.         
The fun bit is making the solar collector. We are in the tropics so we just scrapped the whole glass box thing. I really think its superfluous for anyone below the 30th degree of latitude. I just cut all these plastic pipes up at around 2m long and glue them together with T-pieces. Its so simple you should have thought of it yourself. (Note, for those who are actually going to try this, that the sequence in which you glue it together is a bit tricky, put some thought into it)
Plumbing it into the drum takes a bit of thought. Solar hot water works labelledon the principal of thermosyphoning – hot stuff rises (like me really) and cold stuff sinks. So at the bottom of the drum a pipe comes out to go down to the bottom of all the vertical tubes. (Note that I screwed this straight into the small hole in the drum, its a 3/4” fitting). The sun heats up the water in the tubes, it rises up and finds its way back into the top of the drum. I made my own little hole for a 3/4” fitting by using a small drill bit and drilling little holes around in a circle. (For the techno buffs, the messy hole I create receives a 3/4” steel nipple fitting which sort of threads its own hole in and then I plug it up with silicon.) The big hole in the drum is left for inspection and also to allow air trapped above the hot water intake to escape.
The single most important thing to get right is to allow for the expansion and contraction of hot water. If you stuff this up the whole thing could blow up. I just put in a rising pipe which goes up higher than the water in the holding tank (the holding tank is on a small hill behind the house, water comes into the solar hot water system by gravity.
The second most important thing is to make sure that the hot water goes uphill all the way from the vertical pipes into the drum and the cold water in the drum goes downhill all the way to the bottom of the vertical pipes.
And hey presto! Hot water.
The whole thing cost us about $25 in bits. Takes a day or so to build and mount.
PS If you live in one of those rich, fancy countries stuffed with heaps of rules I suspect this would be somewhat on the illegal side, so just forget I ever told you.
PPS If you want to pull this off under a pressurised system (like a pump) there is a simple way. If you cant figure it out, ask your grandfather. If he cant figure it out, email me.


Anonymous said...

You're a star!!! and thanks for the tips. AG is busting to try this. I'm sure he's thinking "If Sam can do it, I can do it!" OK truth is I'm finding this little project pretty cool conceptually and think it would be a great homeschool project... (and um, I don't have a grandfather to ask...)
Missy :-)

Karen @ Pieces of Contentment said...

Brilliant idea for those with some building/hardware skills. I'm very grateful for our "conventional" solar hot water and grid-feed solar panels.

Alex Lanis said...

You say plastic piping. Will PVC work or can it not stand up to the heat?

Samuel said...

Hi Alex, yes, I have been using PVC plastic pipe 1/2" for the heating section and then 3/4" to take it up to the tank. It is best to clean the PVC with a pipe cleaning fluid like acetone or we use thinners - the same stuff we use to thin down varnish. Just wipe the joining area with a rag dipped in this thinners and then apply the PVC glue to the pipe and the join and quickly push together. I made a mistake on the first model when I glued all the T-joins together in a row and then tried to glue in the long pieces in between. This is almost impossible to do well so glue the two T-pieces to each long in between piece and then glue all these together to build your rack. Happy gluing, dont get too high.

Alex said...

Great! Thanks. No hot showers in Haiti and it's killing me! Ready to get started!

Anonymous said...

Hi, I was wondering about the purchase of the 44 gallon drum. Did you import it or buy it somewhere in East Timor? I am studying Engineering and doing a renewable energy group report for a town (Codo) in Timor Leste and we need to purchase a 44 gallon drum, preferably in the country to keep cost of the solution down. Thank you.

Unknown said...

I need to have my hot water looked at. It hasn't been getting as warm as I'd like. I think that I might need to get a new one. Thanks for posting this.
Gary Puntman |