DIY: Solar Powered Water Heater

[hayenmill]

I did this recently, was wondering what you guys think about it.

Here's the blog post (http://ecowanderer.wordpress.com/2009/12/18/diy-solar-powered-water-heater/)

And the instructables (http://www.instructables.com/id/DIY-Solar-Powered-Water-Heater-3-Steps/)

And the youtube video (http://www.youtube.com/watch?v=o3AhS615-Hk)

Basically, it works as follows:

Water, inside a water reservoir, will flow through a pvc pipe which is being heated through a simple parabola which reflects sunlight .

Here's a pic of it finished (http://ecowanderer.files.wordpress.com/2009/12/dsc05537.jpg)

Any thoughts?

P.S: I know I shouldve used copper instead of PVC, but I had serious budget limitations, besides an irrational belief that metal such as copper, brass or aluminium could intoxicate the water for a shower... (yeah, i know...)

[wardenclyffe]

Any thoughts?


My thought is, "Does it work?"

Ward

[hayenmill]

My thought is, "Does it work?"

Ward

Why would you think it wouldn't work?

Anyway, I'll post a video of it working soon (with a thermometer), as soon as I tweak the right angle of the parabola.

[shadron]

Oh, it will warm up the water - a little. PVC is much more an insulator that copper is, so a lot of the heat you generate on the black surface by irradiating the pipe will heat the air around the pipe rather than the water within. If it were copper, you'd have much better heat transfer into the water, but even then, a trickle is all you'll be able to pull through it and get significant heating. Water has a rather high heat capacity, which means it takes a lot of energy to raise it's temperature.

If you want to use this, you probably want to recirculate the water through the pipe repeatedly, which will slowly heat up all the water in the tank. In a couple of hours you may have enough for a brief shower. BTW, as long as you're doing this, you might as well paint the tank black, too, an dthe top of the pipe as well as the bottom, and leave it where the sun can hit it. In this sort of case, every bit helps.

EDT: one more thing. If your reflector is hitting all sides of the pipe, the best transfer will require the pipe to be at least half full of water so water is immediately adjacent to the entire radiated surface of the pipe.

More EDT": the reflector needn't be parabolic (which is difficult to do; circular will be much easier). A parabolic mirror focuses on a single point, but you don't care as long as it impinges on some part of your black painted pipe. semi-circular would do fine for the size of reflector pictured.

[wardenclyffe]

Why would you think it wouldn't work?

It might very well work. It's just in your first post you explain how you built it, but you never say "I've disconnected my regular water heater, and it's amazing how hot the water in the shower is!"

I believe you can build it. I'm waiting to hear whether it does what you hope it will do. I hope it does. As a life-long cheapskate, I would love a solution like that.

Ward

[rjh01]

You should be able to buy a solar water heater. Are there any installed in your neighborhood?

Edit. I doubt it would heat up your water that much as it is not that big.

By the way what is your latitude?

[shadron]

There are any number of magazine articles that will instruct you on how to hook up a tank to a solar panel and use gravity feed to cycle the water through the panel to warm up and then gravity feed it to where you want to go. They'll even tell you how to build your own solar panel. You have the right ideas here, but you need to expand the amount of heat input and get that insulating plastic from between the sun and the water, and to get a tankful instead of a trickle you have to recycle it through the tank repeatedly - you want to use the whole day's worth of sunlight, not just that on the pipe while you're actually drawing water. Try out looking into BackHome mag, Backwood Home, Mother Earth News, Countryside and Small Stock Journal. Go to their websites and search them.

[Magyar]

I believe that it's Spain, I heard it on NPR a week or so ago, has mandated that ALL houses use solar powered water heaters.

quick google
http://www.timesonline.co.uk/tol/news/world/article389061.ece

[GreyICE]

I believe that it's Spain, I heard it on NPR a week or so ago, has mandated that ALL houses use solar powered water heaters.

quick google
http://www.timesonline.co.uk/tol/news/world/article389061.ece
For Spain, seems entirely sensible.

[Nosi]

The more gadgets we can get off the grid the better.

[I Ratant]

I had a plastic bag I used camping, transparent on one side, black on the other.
Filled with water, it got more than hot enough for a good rinsing in just a couple hours in the summer sun.

[nescafe]

I did this recently, was wondering what you guys think about it.

Here's the blog post (http://ecowanderer.wordpress.com/2009/12/18/diy-solar-powered-water-heater/)

And the instructables (http://www.instructables.com/id/DIY-Solar-Powered-Water-Heater-3-Steps/)

And the youtube video (http://www.youtube.com/watch?v=o3AhS615-Hk)


Cool.


Basically, it works as follows:

Water, inside a water reservoir, will flow through a pvc pipe which is being heated through a simple parabola which reflects sunlight .

Here's a pic of it finished (http://ecowanderer.files.wordpress.com/2009/12/dsc05537.jpg)

Any thoughts?

P.S: I know I shouldve used copper instead of PVC, but I had serious budget limitations, besides an irrational belief that metal such as copper, brass or aluminium could intoxicate the water for a shower... (yeah, i know...)
Don't use PVC for hot water -- too hot, and the pvc starts to soften and break down. Copper, while expensive, is used universally for indoor plumbing around here -- it does not care what temp the water is at, and is much less likely to fail than PVC over the usable lifespan of most plumbing

[Hamradioguy]

Looks more like a semi-circle than a parabola....but that's OK. These type things are very common in Grenada. But they use copper for reasons mentioned in other posts. I remember one in a place I rented a few years ago with a trough about 5-6 ft long. The water was so hot you had to mix it with cold water to shower or wash. Mind you, Grenada is close to the equator, and the sun is very high in the sky for a good part of the day. If you are much further north you'll not get a lot of really hot water.

[CORed]

Yes, copper would be much better, for one thing PVC weakens considerably at temperatures above, IIRC, 120 degrees Fahrenheit, so you're likely to get leaks. For another, it's a pretty poor conducor of heat. If you're going to use plastic pipe, at least use CPVC (it's fairly commonly used for hot water).

[skeptsci]

I believe that it's Spain, I heard it on NPR a week or so ago, has mandated that ALL houses use solar powered water heaters.

quick google
http://www.timesonline.co.uk/tol/news/world/article389061.ece
For sure in Israel. Has been madated since the sixties (!!) for every living quarter in the country. It costs around $400 for a capacity of 150 liters (enough for a 4 member family) and is very efficient.

[Bikewer]

Years ago, during a period of financial insolvency, we had our gas shut off. In the Summer, we would simply fill gallon plastic jugs full of water and set them out in the sun for a few hours.
Worked fine.... Not too practical in Winter, though.

[JoeTheJuggler]

I did this recently, was wondering what you guys think about it.

Here's the blog post (http://ecowanderer.wordpress.com/2009/12/18/diy-solar-powered-water-heater/)

And the instructables (http://www.instructables.com/id/DIY-Solar-Powered-Water-Heater-3-Steps/)

And the youtube video (http://www.youtube.com/watch?v=o3AhS615-Hk)

Basically, it works as follows:

Water, inside a water reservoir, will flow through a pvc pipe which is being heated through a simple parabola which reflects sunlight .

Here's a pic of it finished (http://ecowanderer.files.wordpress.com/2009/12/dsc05537.jpg)

Any thoughts?

P.S: I know I shouldve used copper instead of PVC, but I had serious budget limitations, besides an irrational belief that metal such as copper, brass or aluminium could intoxicate the water for a shower... (yeah, i know...)

I'm working on a passive solar water heater. Hopefully I'll be ready to do the outside stuff in the early spring, but I'm trying to get the indoor part of the plumbing done over the winter.

Mine is a bit more conventional. It's basically a 30 gallon tank scavenged out of an old electric water heater. I'll paint it black and mount it on my south facing roof propped up inside an insulated box lined with foil that will be glass covered facing the south. (The glass part will be about 45% to the east and west, making about a 90% that can catch the rays.) The cold water in pipe goes in at the bottom, and the water out goes out at the top, so you take advantage of the temperature gradient in the tank.

I have no idea how well it will work for how much of the year, so I'm making a mess of pipes and valves in my basement so that I can set it to work as my only hot water heater, set it to work as a pre-heater for my conventional gas-fired heater, or shut it off and drain it.

I'm mostly doing it on the cheap. The valves are the most expensive part since I already had about enough copper pipe, and the rest of the materials are scavenged.

[Nosi]

I live an apartment complex so I have far fewer options.:boxedin:

[novaphile]

Good effort, but you'll probably surprise yourself with how critical you'll be of this first go once you've tried a few more experiments.

I've build a solar water heater out of junk yard scraps (on a friends of the earth camp when I was a teenager) and offer the following suggestions.

1. A copper pipe inside an insulated box with a glass lid works really well.

2. Painting the internal metal components (that the sun can shine on) black helps a lot.

If you want to make something really efficient, create a sealed system that circulates a heat transfer fluid (like vehicle coolant) between your collector and through a coil inside your insulated water tank.

There are systems that are commercially available in Australia, which are just a water tank with little alcohol filled vanes on the outside. All you have to do is stand the tank, on the ground, in the sun.

Using a sealed system also reduces any risk of pipes freezing and bursting inside of your collector (I don't know if that's a problem where you live).

I really wouldn't use PVC pipe, I'm a bit wussy when it comes to heating things up in plastic, if there's any chance that I might be ingesting extra chemicals as a result. Solar water collectors can get really hot.

[GreyICE]

Good effort, but you'll probably surprise yourself with how critical you'll be of this first go once you've tried a few more experiments.

I've build a solar water heater out of junk yard scraps (on a friends of the earth camp when I was a teenager) and offer the following suggestions.

1. A copper pipe inside an insulated box with a glass lid works really well.

2. Painting the internal metal components (that the sun can shine on) black helps a lot.

If you want to make something really efficient, create a sealed system that circulates a heat transfer fluid (like vehicle coolant) between your collector and through a coil inside your insulated water tank. Ugh. Please don't do this. The chances of microleaks are non-zero, and you really don't want to be doing this stuff. Leave heat transfer fluid to professionals.

The rest is a good idea, but you can neither build a good heat transfer mechanism, nor ensure it is free of microleaks.

There are systems that are commercially available in Australia, which are just a water tank with little alcohol filled vanes on the outside. All you have to do is stand the tank, on the ground, in the sun. Which is definitely a good idea. Especially in areas where the pipes can't freeze.



Using a sealed system also reduces any risk of pipes freezing and bursting inside of your collector (I don't know if that's a problem where you live).

I really wouldn't use PVC pipe, I'm a bit wussy when it comes to heating things up in plastic, if there's any chance that I might be ingesting extra chemicals as a result. Solar water collectors can get really hot.[/QUOTE]

[novaphile]

ugh. Please don't do this. The chances of microleaks are non-zero, and you really don't want to be doing this stuff. Leave heat transfer fluid to professionals.

The method I used when I last tried this approach was a single contiguous coil of copper pipe with all connections external to the water tank.

I haven't come across the "micro leak" problem but will happily rely on your superior knowledge in this subject.


Which is definitely a good idea. Especially in areas where the pipes can't freeze.


I'm having trouble following this part, I'm guessing that you meant where the pipes can freeze.

I saw that particular style of system in Canberra, where all water pipes are buried quite deep in the ground to reduce the risk of pipes freezing and bursting.

I believe that some kind of alcohol was the heat transfer fluid used in the collectors.

[TjW]

I'm working on a passive solar water heater. Hopefully I'll be ready to do the outside stuff in the early spring, but I'm trying to get the indoor part of the plumbing done over the winter.

Mine is a bit more conventional. It's basically a 30 gallon tank scavenged out of an old electric water heater. I'll paint it black and mount it on my south facing roof propped up inside an insulated box lined with foil that will be glass covered facing the south. (The glass part will be about 45% to the east and west, making about a 90% that can catch the rays.) The cold water in pipe goes in at the bottom, and the water out goes out at the top, so you take advantage of the temperature gradient in the tank.

I have no idea how well it will work for how much of the year, so I'm making a mess of pipes and valves in my basement so that I can set it to work as my only hot water heater, set it to work as a pre-heater for my conventional gas-fired heater, or shut it off and drain it.

I'm mostly doing it on the cheap. The valves are the most expensive part since I already had about enough copper pipe, and the rest of the materials are scavenged.

I have a pre-heater system using two 4x10 foot panels rather than a rooftop tank. A very small pump and motor circulates water between an insulated 80-gallon tank in the garage and the panels on the roof when the panel water is warmer than the tank water, or the panel water is very close to freezing. I'm in southern California, so this technique of keeping it from freezing doesn't waste very much gathered heat.
The cold water feeds the tank, the tank feeds the 40-gallon gas water heater. You know you've been in the shower too long when the shower starts getting hotter. The "preheater" is usually 140 F or warmer, and the gas heater is set for 125 F.

We used to have a solar shower out at Andy Jackson's hang glider LZ. This was a 55 gallon drum painted black, with a valve and sprinkler head on the bottom. It was set up on a platform next to the shower stall. We'd fill it with water in the morning, and it would be nice and warm by the evening.