I'd like to put in a hot-water pre-heater.
ie; a coil of black plastic pipe on the roof. It would go between the cold water source, and the cold-water inlet to the water heater. No controls, no relays, no housings, no...anything.
On warm sunny days ( 99% of the time ) it would pre-heat the water going into the water heater.
My question is; What type of flexible black plastic pipe would hold up to the sun without degrading ?
if you look at how much water you will be heating its a fiancial loser as described. not enough water will be heated.
payback 25 years
With enough pipe, and diy? I was in mexico, everyone had black plastic water tanks on the roof and 5 gallon tank water heaters, if the tank didnt work the water was still hot enough to take a quick shower. Plastic pipe and tanks are dirt cheap, but you still done believe in tankless and you havnt owned one.
There are a number of DIY solar water heater plans on the network that can be built fairly cheap, less than $100 I suggest you look up these plans.
Jimmie
There are a number of DIY solar water heater plans on the network that can be built fairly cheap, less than $100 I suggest you look up these plans.
Jimmie
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first question to answer: does it freeze whereever in the world you are?
Yeah, I looked at it a while ago and the length of pipe needed to equate to a 50 gallon tank is considerable. But having said that, *if* pipe can be found cheap enough somewhere then maybe...
My main concern wouldn't be degradation, but whether anything that made financial sense was also suitable for domestic water and wasn't going to leech something nasty into the supply...
Well, that depends on location, materials cost, typical inlet water temperature etc. (ours sits at an average of about 50F, but I don't know how typical that is)
cheers
Jules
When I was in college in 1975, I build a solar water heater. It used a thermosiphon principle. As I was living in a house trailer at the time, the hot water would rise into the small water heater in the trailer and push the cold water out the bottom of the inside heater into the solar insulated box that was outside, lower than the trailer. Inside the insulated 4 x 8 box, was 500 feet of coiled black plastic hose. it worked real good for most of the summer. Even on a cloudy day I would get very hot water out of it. Alas, though, my design had a flaw, and the coil got a kink in it and one day it sprung a leak. My wife shut off the water, and by the time I got home a couple hours later, all I had left was a giant blob of melted plastic. Needless to say, future ones I dabbled with were made of materials that would not kink.
Roanin
The problem with this is the water in the pipe on the roof will freeze in the winter!
So part of the design should be that you can turn it off in the winter (Inside the house.) and all the pipe runs "downhill" on the roof (a curving back and forth "S" like a road coming down a mountain) so you can open the top of the pipe and open the bottom of the pipe and all the water will drain out the bottom.
And/or also be able to drain the pipes leading down to the water heater.
Then for more efficiency, water heaters will keep the water warm for over a day! So a better system would be to get a LARGE used water heater (recycling center) which still has a good tank, then use a solar powered water pump to circulate water to this tank during the day when it is hot, then not circulate water in the evening.
And place this tank in-line before your existing hot water heater. Then there will be warm water flowing into your existing hot water heater at all times (including the evening).
An even more advanced system would have temperature sensors and would only circulate the water when the roof water was warmer than the water in the pre-heat tank.
In any case, you water heating bills will be MUCH lower! An electric water heater can be 30 % of an electric bill!
-snip-
Or 5%--- or, I suppose, 90%.
I wouldn't get too excited. I went from electric to propane 20yrs ago or so when my electric bills were about $100 a month. The propane only cost me $10-15/month so it didn't bother me too much that I never noticed a change in my electric bill at all. Switching the dryer helped a little. Turned out my refrigerator was the culprit. The defrost element in the doors was constantly on.
Now I've got a Kil-o-watt meter that gets frequent use.
Jim
Roof coils not so hot for a occasional-use system, since you would quickly empty the coil of warm, and the cold coming in would not have a chance to get warm. But lots of people have them on their pool pumps around here- low flow, and going most of the time. People tell me it extends the swim season by a week or two on each end, and keeps pool toasty warm in the sunny months.
-- aem sends...
Try this:
Schedule your computer to "Hibernate" at 10:00 p.m. (or whatever). Leaving it on all night is 10 hours x 100 watts = 1 KWH. If three computers, that's as much as 50¢ a day.
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