The Best Solar Heating Ideas

Savings

• The California Energy Commission estimates that a typical household using SHW can cut 60 to 70 percent off water heating costs.

Five types

• Over the past 30 years, dozens of solar heating methods have been tried but they can all be classified under one of five types: Batch, Thermosyphon, Pressurized glycol, Open-loop direct, and Closed-loop drainback. Some are active, meaning they have moving parts, and others are passive.

Household size

• The number of people in a household and the climate are major considerations when deciding on a system. A couple living in a temperate area should consider a batch heater, while for a bigger household in a colder climate the thermosyphon or drainback have more to offer.

  Another factor to consider is the various state and federal incentive programs, some of which only apply to certain systems in certain areas. Some systems must be professionally installed while others can be installed by a competent do-it-yourselfer.

Batch Heaters

• Solar batch heaters are simple and have been around in the United States for a century. A tank of water is enclosed in an insulated box covered with glass and facing south. Cold water is piped to the bottom of the tank; hot water is taken off the top by water pressure.

Thermosyphon

• This is the most popular solar water heater worldwide and it works on the principle of heat rising. The tank must be directly above the collector. An advantage of this system is that solar heat is stored in a well-insulated tank, so there is no overnight loss.

Pressurized Glycol

• These systems are for cold climates. A mixture of water and antifreeze circulates from the collectors through a coil of pipe in the solar tank, then back through the collectors. The water warms by heat transfer. These systems require an expansion tank.

Open-Loop Direct

• Used in warm climates, open-loop is the simplest active system. A water tank is connected to a solar collector, with a sensor to control the maximum water temperature. Water enters the bottom of the collector and rises into the tank as it warms.

Closed-Loop Drainback

• The heat-transfer fluid is distilled water. When the system is not pumping, the distilled water is stored in a 10-gallon reservoir. When pumping, it circulates through the collector and heat exchanger, passing heat to the water in the solar tank. The collector must always be higher than the storage tank.