Weekly DIY: Solar Shower

May 2, 2007

PhotoCredit: Path to Freedom
If you have been exploring solar energy at all, you already know that the payback period for a solar hot water system is much shorter than that for a solar photovoltaic system. The system for solar hot water is much simpler. Rather than converting solar energy into electricity with expensive photovoltaic panels and then rectifying the current through an inverter to create AC power, a solar hot water system uses a series of loops to directly heat the water moving through the collector.

Solar hot water systems are a little more complex in cold weather locations where they need to be filled with anti-freeze fluid for heat collection and then use a heat exchanger to transfer heat to the water, or valves and mechanical systems in the plumbing in order to prevent damage from freezing. But even with these elements, the payback period for a solar hot water system can be just a handful of years, even in a northern state.

But if you want to do some experimentation with a hot water system without going to a whole house system, this project will provide an inexpensive demonstration project that gives you a useful device.

I must preface this with the caveat that, unlike some other projects I've written up, I have not built this one myself. However, I've been gathering information for a few weeks, and I have several resources for you to use to look further into this project. And, in the middle of writing this article, I found another commercial example (in case you want to buy something like this rather than making it yourself, although there is no price listed as yet) on The Sietch Blog. (They have posted earlier examples that are being used for more extensive hot water needs, as well.)

The materials list for this project are as follows:

PhotoCredit: Path to Freedom

  • 75-100 feet of 5/8" inside diameter black garden hose
  • a low flow showerhead (and possibly an adapter to connect it to the hose)
  • a piece of plywood or some other support for the coil
  • and some hardware for mounting the coil; the photo here shows some plumbing strap being used to keep the coil nicely organized and flat.

You will also need to have a place to mount this assembly overhead and in direct sunlight. (5 gallons of water weigh more than 40 pounds, so be sure it is securely supported.)

FrontStepDesign is where I first came across the concept for the solar shower. (Of course, she's in Florida, where an outdoor shower is more useful fixture than it is further north.) Her inspiration came from a similar project at Path to Freedom (a couple of whose photos I've borrowed for this article. The whole set begins here) I recommend that you take a look both at those photos and the FrontStepDesign article for further information about the assembly. Basically, you need to make a flat coil of the hose, and then fasten it to a supporting board or surface. A few small bolts through some plumbing strap, as shown, makes a neat and efficient assembly. Then it is simply a matter of connecting the showerhead to the hose (you may also need a plumbing adapter for that), shutting off the showerhead and filling it with water, and then setting it in the sun and allowing it to heat.

Let me leave you with some comments from Sarah at FrontStepDesign. She's a fellow architect, so I trust her numbers about the project:

"A low-flow showerhead ($15) from the local big box uses 1.4 gallons/minute. A 5/8" interior diameter black garden hose ($30) holds 5.1 gallons of water. That's only 3.5 minutes per change of water in the hose – can it really heat up the water? All sorts of people say they've done this, but clearly not enough geeks. I want 'time to heat a 5/8" hose to 120F' data! Of course, if you switched to the not-yet-available Aqua Helix, at only .5 gpm, you'd get a 10 minute heating period in the hose."

I'll be especially interested in feedback from any of these that you build.