The German solar thermal industry
The use of solar energy to generate heat has been practised for many years now. Solar thermal energy can be used to heat water and for general heating and cooling.
The technology at a glance
In Germany, solar thermal energy has been generally used as a means of heating domestic water supplies and as means of heating in detached and semi-detached housing. Great efforts are currently being made to introduce solar thermal energy in apartment blocks, hospitals, residential complexes, hotels and in the commercial sector. In domestic applications, there are generally just two types of system; those which are used solely to heat drinking water and those which also provide domestic heating (dual systems).
Around half of all newly installed solar thermal systems serve exclusively to heat drinking water supplies. They are typically designed so that in summer they are completely responsible for water heating. In winter however, water heating is generally supplied using a heating oil, gas or wood fired boiler, which is supported by the solar thermal system on sunny days. This means that each year around 60 % of heating requirements can be met by the solar thermal system.
Dual systems, which also provide general heating, enjoy a market share of around 50 %. Their solar collectors have larger surface areas and provide an extra means of heating buildings during the autumn and spring months. Typically, the percentage of solar energy of the total energy needs of a building is 20 to 30 %, depending on how well insulated the house is and size of heating requirements. Special solar houses also exist, which get 50 to 100 % of their total heating energy from solar energy.
Solar Collectors
There are three types of solar collector.
The simplest form of collector is the unglazed plastic absorber. In this case, water is pumped through hoses or black plastic mats, and is used to heat open-air swimming pools. Temperatures of 30 °C to 50 °C are typically achieved with this method.
Almost 90 % of all collectors used in Germany are flat plate collectors. The solar absorber, which converts solar radiation into heat, is contained in an insulated and glazed box to prevent heat loss. Flat collectors generally work at ranges between 60 °C and 90 °C.
Evacuated tube collectors are capable of operating with greater efficiency, because heat loss is reduced by strong negative pressure in the glass tubes. A collector comprises a number of vacuum tubes.
Air collectors are a special type of flat collector construction. Air is used as a heat transfer medium and used to heat halls and buildings. Water can also be heated by installing air-water heat exchangers. The heated air can also be used directly to dry agricultural produce.
Market developments in Germany and the world
In 2006, solar thermal systems for water and building heating with an overall capacity of 105 GW were installed worldwide. Studies have concluded that annual growth in this sector will be as high as 15 %.
To date, about 5 % of German households use solar thermal energy, and over one million solar thermal systems are already installed on German roofs. By the end of 2008, the total surface area of solar collectors installed in Germany was 10 million square metres. Their combined power output amounted to some 7300 megawatts. Sales figures for this sector totalled 1.2 billion Euro and around 20,000 jobs have also been made available. Over the course of the next few years the German Solar Industry Association (BSW) expects strong annual growth of 25 %.
Beneficial conditions for stronger growth in the solar thermal sector
Because of climate protection measures, oil and gas prices are spiralling. This has lead to increasing numbers of solar thermal systems for water and housing heating being installed. The European Union has set itself the target that by 2020, at least 20 % of energy requirement should be met by renewable energy sources. The German government is determined to double the number of renewable energy systems for heat generation by 2020, bringing the figure up to 14 %. In order to encourage the use of solar energy systems, citizens receive grants and subsidies if they decide to install solar thermal systems. On top of this, starting in 2009 a certain percentage of the heat requirements of new buildings must be met by renewable energy sources, e.g. wood-fired boilers, geothermal heat pumps or solar thermal systems.
Outlook
The importance of solar thermal energy has been underestimated for a long time now. Thanks to sharply increasing energy prices, this is no longer the case. In the future, solar thermal systems will be installed in hotels, apartment buildings and other new applications. Of particular promise are those systems which provide support for cooling using solar energy. More than 200 pilot systems have already been installed across Europe. Companies and research institutions are working to improve this technology, making it more compact, cheaper and more suitable for low power applications. For example, a German system has been supplying the Haribo Museum in Uzès, France with solar heating and cooling since 2006. Solar assisted cooling is of particular importance in countries with a high cooling requirement. This futuristic technology promises to provide long-term reductions in energy consumption and lighten the load on the environment.
German solar thermal companies possess many years of experience in the production, design and construction of solar heating systems and their components. Some of these companies can be found on the following pages.
