pump and controller
Solar Water heating
liz Merry and
In most parts of North America, the best bang for your solar energy buck is with domestic solar water heating (DSWH). It’s a no-brainer in the desert Southwest and in semitropical Florida and Hawaii.
A complete DSWH system can be installed for $4,000 to $7,000, depending on its size, complexity and the climate.
These systems are now eligible for the 30 percent federal tax credit. At today’s energy prices, over the life of the system, the
cost to operate is about 20 percent lower than a conventional gas water heater and 40 percent lower than an electric one. As
gas and electricity prices rise, DSWH will look like a better and better deal. The benefits are much greater since solar energy
This article is adapted and
avoids 2,400 pounds of CO2 per year and provides a secure domestic source of hot water.
Solar hot water systems come in two flavors: passive and active. In warm climates, a simple passive system can provide
updated from the Solar
plenty of hot water.
Energy Resource Guide 2008,
published by the NorCal
Passive Solar water-heating Systems
Solar Energy Association
Passive systems are installed in areas where freeze protection is not an issue. The most common types are integral col-
( norcalsolar.org), a chapter
lector storage (ICS) and thermosiphon systems.
of the American Solar
In an ICS (or breadbox) system, cold city water flows into a rooftop collector. The collector holds 30 to 50 gallons
of water in a serpentine pipe with a heat-capturing coating. Hot water from the collector flows directly to a conventional
water heater; in effect the sun does most of the work usually performed by the water heater’s burner. As hot water is with-
drawn from the water heater, cold water is drawn into the collector, driven by pressure in the city water pipes.
energy Star: the energy
Star program rates solar
water-heating systems. Comparative performance data
for products from two dozen
companies are listed at 1.usa.
Swimming pools and hot tubs: one of the most common uses for
solar water heating is to heat pool water. Pool solar collectors are lighter
in weight — usually made of uv-resistant polymers — and less expensive than dSwh systems. the size should be 50 to 100 percent of the
surface area of the pool. the more solar collector area, the warmer the
pool will be in cool weather. the pool serves as the storage tank, and the
filtration pump circulates the pool water through the collectors. a solar
collector can provide all the heating necessary for a swimming pool, but
hot tubs and spas need a backup or booster heater.