Photothermal systems, also known as Solar Thermal Systems, heat water using energy converted from sunlight.

TECHNOLOGY
Solar collectors are the heart of most photothermal systems. The collector absorbs the sun's light energy and converts it into heat energy. Solar collectors heat a fluid, either air or liquid. This fluid then is used to heat water - directly or indirectly - for residential use.1

TYPES

• Active solar heating and cooling is a concept exemplified by a residential active solar thermal hot water system. Residential active solar thermal hot water systems are practical for using on homes. These systems are characterized by south-facing, flat panels on the roof of a home, usually covering 40 square feet. The term "active" implies a pump that circulates water when the panel is warm enough.

• Passive solar heating and cooling is a category of systems larger than that categorized by active solar heating and cooling. These are known as passive solar thermal space heating systems. The term "passive" implies that there is no use of mechanical or electrical energy to move fluids. "Passive" systems are better integrated into the structure of buildings and are larger than "active" systems. These systems often involve glazed vertical walls and thermal storage systems integrated into the walls or floors, rather than a separate tank.

ENVIRONMENTAL IMPACT
In California, buildings account for 24% of the state's total greenhouse gas emissions.2 A large portion of those emissions are products of energy consumption in homes and commercial facilities. Heating and cooling systems incorporating solar technology greatly reduce the building greenhouse gas emissions. Water heating alone accounts for approximately 25% of the total energy used in a typical single-family home. An electric water heater is the single biggest energy user of all appliances in the home. When a solar water heater replaces an electric water heater, the electricity displaced over 20 years represents more than 50 tons of avoided carbon dioxide emissions alone.3

BENEFITS

• Home solar heating can lead to savings of 85% on utility bills over the costs of electric water heating.

• Businesses can save 40% to 80% on electric or fuel bills by replacing their conventional water heater with a solar water heating system.4

DISADVANTAGES
Solar thermal systems require installation of equipment, asking for a costly investment from consumers. However, there are utility incentive programs available as well as federal tax credits.

VALLEY ACCESS POTENTIAL
The Valley can enjoy up to 300 days of sunlight in a year which translates to a significant resource for solar power generation. For the purposes of heating water using solar thermal collectors, sunlight is essential regardless of the air temperature on any given day.

PHOTOTHERMAL IN THE GREAT CENTRAL VALLEY
FAFCO, one of the leading manufacturers of solar thermal products is based in Chico.

For more information on photothermal systems visit the US. Dept. of Energy at
www1.eere.energy.gov/solar/solar_heating.html

1 Eejits Guides: www.eejitsguides.com/environment/solar-water.html (last accessed April 23, 2009)
2 California Climate Action Network: www.cacities.org/resource_files/26927.Green_Building.pdf (last accessed April 22, 2009)
3 Solar Energy International: www.solarenergy.org/resources/energyfacts.html (last accessed April 23, 2009)
4 Themomax Industries: http://solarthermal.com/facts_about_solar_energy.asp (last accessed April 23, 2009)