Solar photovoltaic panels – aka solar cells – are one way to capture the sun’s energy for home use. But they tend to be expensive. This 5-kilowatt system has an estimated cost of $30,000.

One much-less-expensive way to collect and use solar energy is to heat your hot water with the sun. This can be important because roughly 20% of energy consumption can go toward hot water in a typical home. Eliminating some or all of that energy cost has a real impact. Combine that with some way to provide inexpensive heat in the winter, like this…

Build an inexpensive solar collector that works

…and you can make a real dent in home energy consumption without breaking the bank.

The basic idea behind a typical active solar hot water system is nicely summarized in this little video:

You have a collecting panel on the roof, a way to pump water through the panel, a tank to store hot water from the panel (usually the existing water heater), and a way to prevent freezing. In cold climates you might use a slightly more complicated system to prevent freezing – antifreeze solution runs through the panel and a heat exchanger heats water using the hot antifreeze.

In a passive system, a separate storage tank is closer to the panels. Water heated by the sun rises on its own and creates circulation through the tank, like this:

The latest technology is vacuum-insulated tubes (aka evacuated tubes) for the collector:

Examples of evacuated tube technology can be seen here, here and here.

Here is a simple home-brew system that works well:

If you want to DIY, you can make your own panel with copper tubing, you can buy a panel, or you can buy an evacuated tube system. Or you can go even simpler and use a batch heater approach, as shown here:

Basically it is the inner tank from an old water heater painted black and put in an insulated box with a glass cover. If this black tank sits in the sun all day, the water in the tank gets hot and you have plenty of hot water for showering and doing the dishes.

This second video explains how he plumbed his system:

It could be argued that a vertical orientation for the tank would be better because it would take advantage of the natural heat stratification used in a water heater.

See also: How does solar air conditioning work?

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