The Uses and Advantages of Solar Water Heaters

Before hot water leaves the faucet, a solar water heater performs three basic tasks: 1. Energy collection: Sunlight, short-wave energy, is collected and converted into long-wave energy, which is then converted into heat.

Solar collectors are installed on or near the south-facing side of a house. When sunlight passes through the house's plastic or glass, it hits a metal or rubber absorbent material called "glazing." This material converts sunlight into long-wave heat, and the glazing prevents heat from escaping, much like a greenhouse. It's like leaving a car parked in the sun with its windows closed. Without a heat transfer fluid flowing through it, the temperature inside a roof-glazed solar collector can easily reach 300°F (300°F).

The most common type of solar collector used in solar water heaters is a glazed flat-plate collector. A glass plate collector consists of a shallow rectangular box with a transparent plastic or glass "window" covering a flat black plate or optional "chrome" coating. The black plate is attached to a series of parallel tubes or a single serpentine tube through which water, or another heat transfer fluid, passes. 2. Energy Transfer: In "closed loop" or "open loop" systems, a fluid such as water or propylene glycol circulates through a storage tank, transferring the collected energy in the form of heat.

The heat energy is transferred from the entire house to the water storage tank. In some water heaters, hot fluid is pumped from the collector to the storage tank. The pump is powered by electricity, either from an electrical outlet or from a small solar panel next to the house.

3. Energy Storage

The solar-heated water is stored in an insulated tank until it is needed. Hot water is drawn from the tank when tap water is used, and cold water enters the bottom of the tank.

Solar water heaters tend to have slightly larger hot water storage capacities than conventional water heaters. This is because solar power alone must be able to collect enough hot water to meet daily needs, both morning and evening.