SOLAR HOT WATER SYSTEMS
In the world of Solar Water Heaters, there are different types of systems for different needs and applications. For an informative introduction into this type of renewable energy, see the article titled Solar Water Heaters. If you’re just looking into the idea of heating your water through solar energy, you should know that a properly installed, efficient system can reduce the need for conventional water heating in your home or business by 65-70%. If you add that to simplicity of building these systems with the aid of a quality instructional manual you have another large piece of the puzzle to off grid living.
This article will describe the different solar hot water systems that have been proven as industry standard and are the most commonly found these days.
ACTIVE VS PASSIVE
All systems are a combination of solar collectors and storage tanks. There are basically two types of solar hot water systems; active and passive. Simply put, active systems have circulating pumps to move the heated water to and from the storage tanks and passive systems do not. Both systems require a storage tank that has adequate insulation. As explained in the Solar Water Heaters article, the efficiency of a system is drastically improved with proper insulation.
DIRECT VS INDIRECT
The active category of systems branches off into two different types, direct and indirect circulation. Direct circulation systems pump the water from the solar collectors directly into and throughout a home and work well in warmer climates. Indirect circulation systems pumps an anti freeze type solution through collectors to be heated, then this solution is pumped to a radiator type unit called a heat exchanger. The heat exchanger unit actually does the final heating of the water that is circulated into a home. As you can imagine, the anti-freeze component of these units make them more popular in colder climates where freezing temperatures are common.
INTEGRAL AND THERMOSYPHON
Passive solar hot water systems also have two different types; integral collection and thermosyphon. These systems are not as efficient as the active systems, but are usually less expensive. Integral collector systems are also found in areas where temperatures stay above freezing. The basic design of these systems consists of a couple storage tanks that are mounted in an insulated box. One side of this box is positioned to have direct sunlight and is not insulated and is where the heat transfer occurs. These systems will typically lose a lot of their energy at night, so work better if the majority of the hot water needs are mid-late day.
Thermosyphon systems are becoming a popular choice in new homes because of their reliability and efficiency. These types of systems work through simple convection; that is the rising of warm water. When these systems are installed, the storage tank is positioned above the collector; usually on a rooftop. As the water is heated in the collector, it rises up into the storage tank. From the storage tank, the heated water can be directly utilized or brought into a conventional water heater. This type of unit would be considered a “direct” system and used in climates where temperatures stay above freezing. There are also indirect thermosyphon systems for climates where freezing is common which contain an antifreeze solution that is also circulated by convection.
Regardless of the system type, a conventional water heater back up is always a good idea to have. Similar to the way homemade wind turbines can back up a home solar power system on cloudy days, a conventional water heater can do the same for a solar hot water system.
Hopefully this article has given you a basic understanding of the different solar hot water systems and has added another valuable puzzle piece to your off grid living education.