How Solar Hot Water Works

1. Solar Collectors

Solar hot water systems often have a collector that is fastened to the roof or wall of a structure facing the sun. The collector uses solar energy to heat a working fluid within cylinders. Collectors are a form of insulated box, with a glass top covering a flat solar absorber that is connected to copper pipes and metal tubes that are surrounded by an evacuated glass cylinder. Evacuated tube collector systems are highly efficient because they employ the principal of a vacuum being a perfect insulator.

2.Transfer Hot Fluid “Active” or “Passively”

The solar heated fluid can be either transported by an “active system”, which is pumped or a “passive system,” which is driven by natural convection to a hot water tank.

3. Use Solar Heated Water Throughout the Home

Hot water is readily available in the hot water tank and piped throughout the house for use in showers, sinks and appliances.

In active systems, a separate fluid containing anti-feeze and a corrosion inhibitor is used within a coil of copper tubes inside the heat tank to transfer heat. Another application that is low-maintenance, and doesn’t use anti-feeze, is the “drain-back system”, where the piping is sloped so the water just drains back to the tank.

Solar water heating systems provide a sufficient source of hot water year round in most climates. During the winter months, or on cloudy days a back-up power source, such as a gas or electric booster is used. This is how solar hot water systems work to keep the minimum temperature from falling below 55 °C.