How does solar power water heaters help the environment?

Answer 1

Environment benefit of solar water heat comes from using sun's heat to heat water instead of using gas burner or electric element. The sun replaces hydrocarbon fuel, and this impacts environment by reducing carbon emissions, pollution, and cost to extract and transport fuels.

Other factors also play a role:

Source of water. All water heaters, solar and otherwise, impact environment when they are filled with water. Water usually arrives from electric well pump or municipal water service. Electric pumps, pipes, purification, and waste-water treatment factor into water heating. So solar heater is not environmentally better in this category, unless users of solar water heat naturally consume less hot water.

Materials: Another factor is cost and durability of man-made materials used to make solar heater. Materials may be more or less than conventional heater, and affect net environmental impact of solar water heater.

Solar heater with least impact would be clay pot filled with rain water and left in the sun. Environmental damage would be energy used to make clay pot, plus cost of transporting pot to location. The rain and sun are assumed positive environmental factors.

Passive solar heat: A passive solar heater using old water heater exposed to sun's heat probably has low impact on the environment. The tank is being recycled. The tank can be placed on a stand above shower, and then water falls by gravity. Typically however, a passive heater requires varying amounts of copper pipe, and optionally a small electric motor and pressure controls to circulate heat into existing water heater. Again the sun's heat has no measured environmental impact, but added materials do.

Collectors: Other solar water heaters use a collector and small motor to circulate heat into water tank. Some systems circulate hot water directly into tank. Some systems circulate fluid instead of water. Heat transfer takes place when fluid circulates through coiled pipe inside specially-made solar water heater. Collector-type solar heaters use copper pipe, insulation, plus electrically-powered pumps and regulators to control flow and temperature of water. The collector frame is made from wood or metal, and can be painted to absorb heat. Collector is covered by glass or transparent plastic that retains heat so pipes inside collector get hot. There is one solar collector that uses recycled plastic water bottles, where piping runs through the center of several plastic bottles, and recycled plastic replaces glass cover. Collectors need to be cleaned regularly to maintain efficiency.

Solar water heaters with simple design and durable material will probably have better impact on environment, especially if design also reduces consumption.