Solar water heating is a practical technology that has undergone several generations of development. These systems often have a lifespan of more than 30 years, depending on the quality of components.
If you live in an area that does not freeze often, a simple solar water-heating system, backed up by your old storage water heater, may be your best water-heating choice. If you live in a cloudy or northern climate, solar water heating, can still be a benefit, but will cost more initially for a larger collector area, a design that includes freeze protection, and higher quality components.
To employ solar water heating successfully you need a good unshaded southern exposure on your house to mount the solar collectors. You can learn more about siting all types of solar systems on our solar energy site.
Solar water heating systems are not inexpensive, and so are most economically viable if you live beyond the reach of natural gas lines. That's because households with gas water heat typically spend $200 to $300 per year on water heating, while households with electric water heat spend $400 to $600 per year. If electric heating is your only option, your potential savings from solar water heating will be much higher.
Remember that solar heating is the suds on top of the beer for the most efficient homes. Dedicate your first dollars to the other projects on this site that save more money per dollar invested. This is especially true of water conservation measures like making sure you have low-flow shower heads, water-efficient appliances, and insulated water pipes before you consider installing a solar water heating system.
Solar water heaters have two main storage components: a heat collector and a storage tank. Then they have plumbing and a water pump connecting the two in a circuit with hot water on one side and cold on the other. Sometimes the heat collector and storage tank are one in the same. In other types, they are adjacent. And still, other types may have the heat collector on the roof and the storage tank inside the building.
Batch heaters, also known as breadbox heaters, are a simple and relatively trouble free system for climates where freezing weather is rare. Water is heated passively, with no circulating pumps.
Batch heaters are built around a black steel tank that acts both as the collector and storage vessel. The tank is encased in an insulated box covered with glazing.
Batch heaters may survive occasional freezing temperatures, but they are most practical in frost-free climates. Batch water heaters are the least expensive solar water heating option because they don't require separate solar panels.
The batch water heater is usually charged with house water pressure. Domestic water is heated in the batch water tank and then usually feeds into a conventional water heater where heat is added when needed. In the summer, the conventional water heater is called upon infrequently because the batch heater provides water hot enough for direct use at the fixtures. In the winter, when water from the batch water heater is cooler, the conventional water heater compensates for the difference in demand and supply temperatures. Batch solar water heaters typically cost between $2000 and $3000 for materials. Installation might run another $500 to $1000, depending on installation details. Many of these simple systems have also been constructed by do-it-yourself folks.
Thermosiphoning solar water heaters use collectors that are separate from the tank. Like batch water heaters, they work best in frost-free climates, although they can be drained for the winter months in cold climates.
Thermociphoning systems are designed so the grey-water buoyancy of hot water will naturally move it from the collector to a storage tank mounted on top of the collector. The collector looks like an active system. The hot water is sometimes piped directly to fixtures in the home, but thermociphoning systems are often designed so hot water flows into a conventional tank to provide added heat as needed. Themociphoning water heaters typically cost between $1500 and $3500 installed.
Active systems circulate water, glycol, or other fluids through the collectors by means of a pump. These are the most expensive solar water heating systems, and can come closest to providing year round domestic hot water.
An electronic controller monitors temperatures throughout the system, and runs the pumps when sufficient heat is available in the collectors. The pumps and controller can be powered by standard house current, or by integrated photovoltaic (solar electric) panels.
Where temperatures drop below freezing, solar water heating systems need freeze protection. Some systems circulate a water-antifreeze mix through the collectors for protection from freezing. If water is used for a circulating medium, the system is sometimes set up to drain automatically when freezing weather arrives.
The storage tank usually utilizes a heat exchanger that allows the circulating medium, water or antifreeze, to to remain captive in the collection loop. Heat is transferred to the domestic hot water through the heat exchanger. Backup heat, for cloudy weather, is usually provided by a conventional gas or electric system that is installed in either the same tank or in an auxiliary tank. The materials for active solar water heating systems typically cost between $4000 and $10,000. Installation might run $1000 to $3000.
Creating a do it yourself (DIY) solar water heater is relatively simple. You just need to make sure the box is sealed and well insulated. There many individuals who have posted their diy solar water heating projects on the Internet. If you are a good hands on person, this may be a tempting project to pursue.
Tags: solar water heater, hot water heaters.