Solar Hot Water & Electricity
Earthwalker has been living in his Class C RV for thirteen years now. Because he lives in sunny Nevada, he wanted to take advantage of the abundant sunshine and live as green as possible. This is the story of how he created his own solar hot water system. It may look complicated but both systems are easily doable by anyone with basic handyman skills. Lets get started!
In the picture above is an overview of the system. He used PVC spray-painted black to hold the water. He choose PVC because it is light, cheap, and very easy to work with. He bought 20 foot sections and cut them down to 7 foot sections because his RV is 7 1/2 foot wide. You would cut yours to fit your vehicle. He estimates that the 8 sections he used hold about 4 gallons of water. While that is not an abundance, it is enough for one person with frugal use. If you used 2 inch PVC, you would have 8 gallons which should be plenty for a couple, or extra for one person.
He used basic off-the shelf PVC parts available at Home Depot or any other hardware store. A hand saw will easily cut the PVC. Then you just apply cement and press the parts together. It really is very simple. Print out these pictures and take them to Home Depot, and a clerk can help you get everything you need.
In these pictures you can see the cargo rack that came with his RV. To avoid drilling more holes in his roof, the tubes are attached to the rack and not to the roof. At 8 lbs to a gallon, his 4 gallon water system weighs 32 lbs. While that’s light, it is enough to hold the system in place without need for elaborate hold-downs.
Because he used a regular RV 12 volt water pump, this is a pressurized system, meaning as water is used, the pump automatically replaces it. At the end I will tell you how to make a system without water tanks or RV water pump.
In these pictures you can see the three tubes feeding into and out if the system. The yellow hose on the left is cold water coming in from the pump. The white hose in the middle is hot water going out to the RV to be used. So the water comes in from the left and is pumped back and forth through the tubes to the outlet hose on the right. Because the tubes are painted black, they get very hot in the Nevada sun, heating the water in them.
The reddish hose was a first attempt at a drain that didn’t work. The drain is important in winter if you run into freezing weather.
In the picture below you can see the drain that did work. He cut a splice into the top tube (it is still white because he put it on later). In the picture below it you can see the drain tube running down the back of the RV ladder so it is easily opened and closed to drain the system.
The system works extremely well. Under the summer sun the water gets very hot by afternoon. If you take a shower or wash dishes, draining the system, it will be hot again about an hour later. However, in the winter it does not work as well. The water does not heat up much above the outside temperature, which in December through February is in the 50s and 60s. That doesn’t get the water hot enough to use, so he just drains the system in those months.
As I am writing this he is designing a new system to solve this problem. He will take the old system down and install a whole new one, but this time it will be enclosed in a box to capture and hold the weak winter sun. The bottom of the box will be 3/8th inch plywood cut large enough to hold the tubes. The side walls will be either 1x3s or 1x4s, depending on whether he uses 1 inch or 2 inch pipe. On top will be a sheet of acrylic or Lexan to let the light and heat in and to retain it. The tubes will be painted black as before. He will paint the bottom and sides with Elastometric, a thick white paint used on trailer roofs to seal and keep heat out (in this case it will seal the joints and keep heat in). One option is to cover the bottom and sides with aluminum foil to reflect the light and heat onto the black tubes. Another, and probably best, option is to line the inside of the box with a product called Reflectix. It has two very heavy layers of aluminum foil on the outside and has a type of bubble- wrap in-between for insulation. This would reflect the light/heat onto the tubes and also retain the heat in the box. What is unknown is if the Reflectix can hold up in the high temperatures the box will generate in the summer. When the new system is in place, I will update this article.
A Gravity Fed System:
Earthwalker lives in an RV so it was easy to adopt it to a solar hot water system. He already had fresh water tanks and a 12 volt pump. But most of us in vans or campers don’t have those, so how can we copy his idea? Actually, it isn’t hard at all. Where he is using a pump to force water through the tubes, we will use gravity. His tubes are lined up in a level row, but we will line ours up at an angle so that when we pour water in from the top water inlet, gravity will pull it down to the outlet at the bottom.
Buy two 1x4s (or 1x6s) and lay them flat on the ground. Next, draw a line from the top right corner to the bottom left corner. Assemble the end U joint using the pictures above as an example. Then lay them along the diagonal line and trace the holes in the 1×4 centered on it spaced the right distance apart. The longer the 1X4 is, the more tubes you can get in it. I would run the tubes across the back of the van, so they will be about 5 1/2 feet wide. I would start with a 1X4 about 4 foot long to see how many tubes it will hold. You may find you need a 1×6 instead. Getting the design figured out will take some trial and error. You can practice on cardboard first so you don’t waste wood. When you are sure of the lengths, get a hole saw and cut out the circles on the wood, and that is the framework to hold the tubes in their right spots. Using the first 1×4 as a template, drill the holes in the second 1×4.
Then cut the PVC tubes to the right length (roughly 5 feet) and run them through the holes on the two 1x4s. Then cut and glue to 90 degree joints to connect all the tubes. At the top put in a connector to allow you to add water, and at the bottom splice in a connector to allow you to screw a garden hose on. The system won’t drain in a vacuum, so you will need to keep the fill open when in use.
You can use simple “L” brackets to attach the two 1x4s to the roof. Or you can build an elaborate box to hold the system.