Posted by Tim Jackson on June 27, 2009, 2:03 pm
Jim Wilkins wrote:
I've got working prototypes of low-cost electronic heat-flow and draught
sensors built up here, but the project is on a back-burner because I've
got too much less-speculative work going on at the moment.
Posted by harry on June 29, 2009, 7:25 pm
I have a solar water heater too. I made it myself but before I'd
finished I was wishing I'd just bought one. I made a glass fronted
box (8' x 4') and made an array of copper tubes soldered onto copper
fins. All made from scrap metal. But jeeze, I was at it for weeks.
The big problem was the glazing. I used polycarbonate multilayer roof
glazing. Numerous problems with leaks and expansion buckling. I think
the copper bit performs as well as any commercial design, the glazing
maybe not. All very heavy to get on the roof too. However on a
sunny day I can get the water up to almost 200deg fah. It's not so
good when cloudy. It's probably a bit oversized. It was supposed to
be a self draining job but there was some water left in and it froze
and burst a couple of the tubes last Winter. So I suppose I'll have to
put in antifreeze. It drains into a stainless steel bucket I happened
to have which is open to atmosphere. Well it has a lid. But as it's
in the roof space (hot up there) & the water is very hot the water
evaporates, I have to go up once a month to fill it.
Posted by Jim Wilkins on June 29, 2009, 11:24 pm
Mine is just an old water heater tank painted black. The top half
heats during the day and the heat equalizes through the bottom at
night. It is at ground level so easy to work on. It isn't connected to
the plumbing, which simplifies everything considerably but means I
have to carry the water to the washing machine in a bucket.
Which polycarbonate? The glass on mine has started to crack. I plan to
cover the greenhouse box with a single sheet, like a shed roof, hinged
at the top edge but otherwise free to expand, and kept down when the
wind blows with a crosswise batten and the bungee cords for the
insulated cover panels.
Posted by harry on June 30, 2009, 7:23 pm
Glazing is a big problem. The heat you get in the collector is so
great there'a always gonna be expansion problems. Initially I just
screwed the polycarbonate down with some "penny washers" under the
crew heads. But it all buckled up in hot weather. I tried various
things but eventually when for the sophisticated solution - more
screws & washers.
The polycarbonate is a standard thing over here. It's available in
various thicknesses with multilayers spaced apart. You can get
anything from two layers (3/8" thick to six layers just over an inch
thick) I assume you are on inches over there. The stuff is virtually
indestructable, you can bend it double & it won't break. They make
vandal-proof light fittings from it.
It's pretty expensive, I had some off-cuts from my conservatory roof.
It's quite important to make it as near to airtight as you can to keep
the heat in.
Posted by News on June 24, 2009, 3:16 pm
Harry, is there a web site this house is on?