Photo Credit: geocam20000
Unlike PV solar panels, there is no limit to how low-tech you can go when heating water with the power of the sun. Modern systems use vacuum tubes and they are very efficient. A simple collector that uses a black surface encased in insulation and glass with copper piping running through it will work too. Very basic systems are commonly used to raise the temperature of swimming pools. They can also help reduce the cost of heating the running water that you use in your home. Even if you live far away from the equator, you can offset your water heating costs by 25% or more with a solar water heater. Sunnier places can approach a 100% savings.
If you are thinking about a DIY solar water heater there are three many things that you have to consider when comparing plans or making your own. These are COST, DURABILITY, and EFFICIENCY.
There is no point in spending more on your do it yourself project than it would cost to get a factory made, plug and play water heater. Good quality solar water heaters cost in the neighborhood of $5000. One of the cheapest looking plans that I could find on the internet used Coroplast as a collector. The designer was quite confident about the panel’s efficiency but he admitted that it may not be durable enough to install as a residential water heater. So basically his simple solar water heater excels in one of the three considerations but falls short on the other two.
I saw elsewhere that someone had a plan to convert a free supply of old fashioned cast iron radiators into solar collectors. It seems like a simple plan since these things are incredibly durable. In this case, two out of three is bad. While the plan is cheap and the end product would be durable, the efficiency of the system makes it nearly useless.
The most common type of DIY solar water heater is common because it has the best balance of durability, cost and efficiency. These plans typical involve a collector plate made from a conductive metal like copper or aluminum. This plate is coated on one side with black paint. Copper piping is attached to the back of the plate. This collector assembly is then housed in a basic frame with the coil side next to insulation and the plate side covered with glass. A panel like this can be plumbed to the hot water line for you home. Obviously, the secondary system should be between the solar panel and the outlets (faucets). It would be very inefficient to pump water that you had heated with gas or electricity up to your roof on a cold, cloudy day.
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