Monday, June 20, 2011

DIY Solar Hot Water Heater we Built & Use for Under $200 with a Green Roof twist

Sits right next to the small Cubanelle pepper Green Roof on a southerly exposure sloped roof and the DIY solar hot water panel works very well.  Photos below but first a photo of the Green Roof Cherry Tomatoes growing adjacent to the Rooftop Solar hot Water Heater :)
Rooftop Permaculture - Cherry Tomatoes
I will be clear up front I have alot to do before It is truly complete.  I know there are many unorthodox approaches here and I am sure a mechanical designer could list many reasons why this is an inefficient design and why a much more expensive system would be capture and retain with higher efficiencies.  Importantly, I didn't want to use CPVC or Copper in the collection coils because of photodegradation.

But the point here is simple.  I have disconnected the circuit breaker to the electric hot water heater and we still have plenty of hot water for a family of four, including two shower loving teenagers.

So I understand that the system is inefficient.

But I am not paying for hot water now.  And I am not using coal or petroleum generated electrical power.  What I am doing is using the sun's energy, reducing my electrical bill and affording us here on the Jax Urban Farm another step towards true independence.  Once we get our electric bill I'll do a follow up post.

DIY Solar Hot Water Directions.

1. Find your most sun exposed roof surface.
2. I used a old tin planter boxes for the frames however 3" edging could be used to create the side walls.  You really dont need a bottom to the box.
3. Once you decide the length and width you want - I used 1 meter x 2 meters, cut a piece of used plastic, preferably a EDPM or PVC material - something like a Coy Pond Liner (you can find these on Craigslist for almost nothing).
4. Make sure the roof is clean and spot adhere the waterproofing liner to the asphalt shingles using a tube of roofing adhesive from your home improvement store.
5. Attach the box or frame (I'd recommend a 1 M x 2 M rectangular frame made from 3" edging without a bottom) to the roof above the liner.  Use 1 1/4 or 1 1/2" metal roofing screws with sealant washers.
6. Uncoil a roll of 1" PPE 150PSI Black Irrigation Tubing (see photo below) and place inside frame/box)
7. Drill entry/exit holes in frame or box for tubing.
8. Run 3/4 CPVC pipe from existing hot water heater inlet to tubing in solar box and attach with standard adapter and band.
9. Add drain valve to system for draining during very cold weather.
10. Cover all pipe with standard pipe insulation.
11. Let glue dry.
12. Enjoy free hot water.

I am going to add a piece of clear fiberglass or plexiglass over the box as a top at some point but haven't yet.

The system heats the water going into my hot water heater.  Once in the hot water heater the water stays warm because the tank is insulated.

We've noticed of course the water is hotter during the afternoon than it is in the morning yet there is still plenty of hot water to go around.

What I do plan to do is add another coil of 1" insulation tubing to increase capacity, add a clear cover.

We are considering adding a green roof soil media around the coils and plant some small plants as an experiment.  We have found on our many green roofs that our speciality soil media serves as a heat sink, allowing for the storage of heat.  Will update the post as we implement the green roof component.

There have been no leaks.  The systems has experienced 150-170F , 65C to 75C during the day dropping to 70F,  20C at night so there has been plenty of thermal expansion going on.

Yes, many different ways to cost-effectively (the key here is inexpensive) improve this system and I'd love to hear your comments.  We have worked for years in designing living wall and green roof systems for low cost applications in slums and intense Urban Core permaculture situations and what I cannot incorporate are expensive, custom components.

Disclaimers important, I will say your should check with all the appropriate regulatory authorities for code, permit and blah, blah, blah requirements.  Insurance companies also have their own blah, blah, blah requirements.

However, if you want free hot water you can have free hot water and for less than US $200 and a weekend of your time.

Please leave your thoughts on fine tuning and I'll consider incorporating them!


1. Tube of adhesive $4
2. Pond Liner or plastic $5
3. Roofing Screws $7
4.  6 M ( 20') 3" vinyl or aluminum edging (for sidewall frame) $15
5.  50' roll black 1" 150 PSI irrigation tubing $60
6.  3/4 CPVC to 1" tubing adapters (2) $4
7. Misc 90's ells and couplings 3/4" CPVC & CPVC Glue $15
8. 3/4" CPVC pipe $24
9. 3/4" drain valve $4
10. Standard pipe insulation $10

Total Approximate Cost $ 138
Installed $200 Solar Hot Water Heater

Tubing to CPVC Connection

1" 150 PSI Irrigation Tubing serves as Coils

CPVC supply lines to Hot Water Heater

1 comment:

Unknown said...

I have been talking about this subject a lot lately with my mother so hopefully this will get him to see my point of view.
hot water heater price