Solar thermal collectors

Solar thermal collectors convert solar energy into heat, which can be used for space or water heating. To bridge the time difference between energy production and energy demand, solar heat must be temporarily stored. This can be done for the short term, from day to night, or for the long term, from summer to winter.

The larger the fraction of the heating demand that must be covered by solar energy, the larger the storage becomes. Especially for seasonal storage of solar heat, very large storage volumes are required. Using advanced thermal storage technologies, this volume can be reduced significantly in the future. Hence, more energy can be stored in the available volume, increasing the solar fraction. Alternatively, advanced storage reduces the effective space required for the solar heating system, enabling the use of solar heating where less space is available, for instance in building renovation.

The solar thermal market

With a spectacular growth of 47%, the European solar thermal market exceeded everybody's expectations in 2006, reaching 2.1 GWth, over 3 million m2 of collector area, of newly installed capacity. Consequently, the total capacity in operation reached 13.5 GWth. Several factors contributed to this good result, like public support in several countries, a rapid increase of oil and gas prices, the cut-off of the Russian gas supply in January, and the more and more visible signs of climate change.

Within Europe, Germany is by far the leading market, although the German market has seen some stagnation in 2007. More recently, Spain, Italy, and France have seen a very sharp increase in their solar thermal markets.

Worldwide, Asia is the largest market with 18 million m2, strongly dominated by the Chinese market. The European market is a distant second with 3.9 million m2, followed by the Americas and India with 0.7 and 0.5 million m2, respectively.

Where the European market is dominated by flat plate collector systems, the Chinese and Asian markets consists mainly of vacuum tube collectors.

Since every solar thermal system comes with some form of storage, solar is a very important part of the storage market. The value of the European storage market for solar thermal systems is estimated at around 450 million euros.

More information

This information is also available in an information leaflet on thermal energy storage for solar heating. More details can be found in one of the PREHEAT reports, Heat storage technologies: markets, actors, potentials.