In Hot Water: Solar Thermal Takes Off

• From March 2010 World Rivers Review

Solar thermal collectors – used for heating water and buildings (and even for cooling, through solar chillers) – are now the world's top renewable energy source, producing more energy than wind power, and more than geothermal, solar photovoltaic (PV) and ocean energy combined, a new report states.

In 2009, there were 147,000 megawatts (MW) of wind power, and 174,000 MW of solar thermal collectors. By comparison, there were only about 1,000 MW of concentrating solar plants (another type of solar thermal) and about 17,000 MW of solar PV capacity around the globe. Many concentrating solar plants are in the works around the globe.

Solar thermal collectors use much simpler technology and convert far more of the sun's energy into useful heat than PV. They also are priced much lower than PV panels, and have a quick short-term payback period compared to other renewables.

The global market for solar thermal is booming. An estimated 60 million households worldwide heat water with the help of the sun. In 2008, the use of solar thermal jumped by around 40%, in part due to rising oil prices. It's expected to grow by around 15-20% annually in coming years.

Depending on the region, solar thermal plants can offset up to 60-70% of the energy required for warm water and heating.

According to the Swiss bank Sarasin, two-thirds of the world's solar thermal units are installed are in China, where the government has encouraged their manufacture and installation.

Mexico is trying to bring the technology to some of its poorer communities, using cheap loans to finance the installation of solar thermal, and sharing information and technical assistance. One case study is the working-class settlement Heroes de Tecamac in Mexico City, where 1,000 households have installed solar thermal systems.

Solar thermal energy has now found mention in the EU's renewable energy directive for the first time. EU member states have to present their plans for the national implementation of the directive by June.

New solar thermal markets are likely to develop in Indonesia, Mexico, South Africa and Brazil. Promising signs are also visible in southern Europe, the US, Australia, and India. California recently approved $350 million in rebates for homes and businesses that switch to solar water heating.

Two US senators recently introduced legislation calling for the installation of 10 million solar PV systems and 200,000 solar water-heating systems by providing financial assistance to businesses, homeowners and government bodies.

Even the grey UK is betting on solar water heating. New feed-in tariffs in Britain will encourage homeowners to install systems, and help bring the nation closer to meeting its carbon-reduction targets.