Building a Solar Hot Water Heater Out of Scrap

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Building a Solar Hot Water Heater Out of Scrap

Whether you want to use a renewable energy source to save the planet, or just to save some money this summer, a solar hot water heater is one of the easiest do it yourself projects, and it can be made with largely used materials.
The simplest solar hot water heater to make is one for use in the summer months only, not because they can’t still heat water in the winter, but because you won’t have to deal with the pipes freezing on very cold winter nights.

A solar hot water heater that is only used during the summer months will still save you money 5 to 7 months out of the year. That can save you $100 to $150 per year on your bills.

A solar hot water heater has two basic parts the collector, and the storage tank. If have a conventional hot water heater with a tank, you’ve got the biggest part of the system already as the conventional hot water heater’s tank can be used to hold the hot water from the collector.

If you have a tankless hot water heater than you’ll need to buy a preheater tank, which unfortunately tend to cost almost as much as a regular hot water heater.

Ideally, if you have a working conventional hot water heater and you plan on switching to a tankless model you can simply turn off your old one and use it as a preheater tank.

To make the solar collector you’ll need a pane of glass, or sheet of plastic. The easiest solution is to find an old storm window with its case at a salvage yard, or if you know of anyone who is getting new windows.

Measure your storm window and build a box to hold it. I’ve used both 2″ x 6″s and 1″ x 6″s to make the frame for the box, both work fine. I’ve had some DYIers insist on 2″x4″‘s but I’d personally go with whatever you have laying around.

After you have a frame build a plywood back to match its dimensions. The back can be made of any type of plywood, for my 2′ by 4′ foot solar panel I used particleboard, it worked fine but it was heavy.

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Glue foam insulation to the inside and paint it all flat black.

Drill two holes in the back for the pipes one at the bottom and one at the top.

Build a lattice of pipes, there are long discussions over which pattern is better, a zig-zag pattern where the water flows through every inch of the pipes or a grid pattern with the center pipes attached to the top and bottom ones with T-joints. I don’t think it really matters as long as the input and outflow are on opposite ends of the box.

Paint the pipes flat black to absorb the heat from the sun.

Copper or Iron pipes are best as they will transmit the heat faster, but as the pipes will be collecting heat as long as the sun is shining the ease of use with PVC pipes makes up for the slower heat transference.

Make sure that you have the connections to the pipes sticking out the back of your box and screw the storm window on the front.

Find a suitable place next to your house’s south side that has easy access to the houses water and set up your solar collector at a 15 to 60 degree angle facing south. The optimum is to take your latitude put your panel within 15 degrees of that. For instance my latitude is 34 degrees so my panel can be placed at between a 19 to a 49 degree angle.

Connect the input pipe (the bottom one) to your houses cold water and the outflow (the top one) to the input pipe to your hot water tank. Make sure to insulate these pipes.

If live in a place where winter temperatures get below 20 degrees for any length of time (the system will stay warm enough to survive a light frost) you will need to put shut-off valves and a drain on your connections so you can shut it down over the winter.

As long as the solar collector is lower than the tank it will sit there all day and warm up the water in the tank as warm water rises.

As far as the power these homemade solar collectors under ideal conditions an 8 square foot 2′ x 4′ collector can generate 2,560 BTUs per hour. That is about 7.5% of a typical hot water heater, however it runs all day so it can easily do most of heating for a typical families hot water needs with the heating element only being used to heat the water from 90-100 degrees to 120 degrees instead of from 50-60 degrees to 120.