“Sunny Day For Solar” titled the U.S. American Solar Energy Industries Association (SEIA) on the 24th of September. A day beforehand, the Senate had approved its version of the Energy Improvement and Extension Act of 2008 which would extend the 30 % tax credits for solar thermal...
A hybrid air PV collector: The hot air behind the photovoltaic modules is sucked into a ventilation system. Photo: Conserval Engineering
The Finnish company Cupori Group Oy, which in the spring took over the copper business of Outokumpu Copper Tube, now supplies a copper tube with a particularly clean surface. At the Intersolar 2008 in Munich in June the company presented its new “Tub-e” copper tubes, although still under the old...
At the beginning of August the Swiss company Clariant brought a new heat transfer medium for solar thermal systems out onto the market under the name Antifrogen Sol HT. The antifreeze has been designed to survive stagnation temperatures of over 270 °C unscathed.
Solar thermal factory in Italy: Flat-plate collectors for the MTS Group’s business are produced at this new site in central Italy. Photo: MTS Group
Robert Bosch GmbH has taken over the Thuringian solar cell manufacturer Ersol Solar Energy AG, Germany. In August the world’s largest automotive supplier and electronics company bought up 44.76 % of the shares from the previous majority shareholder Ventizz Capital Partners Advisory AG. Since...
Feeding directly into the district heating system of the Austrian city of Graz: The collector fields are mounted on four different hall roofs belonging to the AEVG, a municipal waste disposal company. Photo: S.O.L.I.D. / Oberländer
So far solar thermal technology is mostly used for domestic hot water, pool heating and room heating. It´s often forgotten that there is a huge demand for heat below 250 °C in industry, which can easily be reached with solar thermal collectors.
An international team of researchers...
Flat plat collectors are made of metal, glass, insulating and joining materials. Typically copper, steel or aluminium is used for the absorber configuration. The sides and bottom of the collector are usually metal and insulated with mineral wool to minimize heat loss. The glass top is made of special glass to resist facture and maximise transmission of energy. In the future, a variety of materials and combinations of materials including plastics may be used to improve cost benefits ratios, higher temperature ranges and systems performance.
Vacuum tubes collectors are made of a borosilicate glass. Mostly the absorber layer is coated on the inner tube and no metal is required. But there are also tubes with an inner metal fin absorber.
For swimming pool heating, plastic or rubber are used to make low-temperature absorber plates.
The solar collector is usually mounted on the roof and is connected to a circuit containing water with propylene glycol anti-freeze added. The tank is also made of metal, partly stainless steel, partly enamelled steel or copper.
There is a wide variety of applications for solar thermal technology. The most common application is the heating of pool water, the heating of domestic hot water and space heating. Not very wide spread yet are solar cooling systems, because of the complexity of the technology and the high initial investment costs. Also, process heat applications such as in breweries or car washes, as well as in the food and textile industries, are still in their infancy. You can search for all these different kinds of applications in the filter section market sectors on the right hand side of the page.
What is the difference between vacuum tube collectors and flat plate collectors? With flat plate glazed collectors the absorbers are fitted in a box closed by a pane of glass (90 % market share in 2009 in Europe). Vacuum tube collectors – which are the dominating technology in China (96 % market share in 2008) – have the absorber coating on the outside of the inner tube in placed within an evacuated glass tube. Generally speaking, the advantage of vacuum tubes is a higher efficiency (less space required for the collector on the roof) and higher temperatures (necessary for process heat and some solar cooling technologies).
The disadvantage: The vacuum tubes produced in Europe are more expensive than the flat plate collectors but in some incentive schemes like in Germany they receive the same grants as the flat plate collectors. In China, some locally produced vacuum tube collectors have a poor quality performance, flat plate collectors are seen as high-quality products.
By far the largest solar thermal market in the world according to newly installed solar thermal capacity per year is China. In 2008, around 21 GWth (30 million m2) were sold in China, which was around 80 % of the world global solar thermal market.
In Europe, Germany – the second biggest market in the world – is dominating. With its newly installed capacity of 1.13 GWth (1,615,000 m2) in 2009, the country reached a market share of 38 % within Europe.
Position three is held by Turkey, a dynamic solar thermal market which is estimated at 785 MWth ( 1,120,000 m2).
Besides these front-runners, India, Brazil, Israel, Austria, Greece, USA, Japan, France, Italy, Spain and Australia are countries which reached a market volume of greater than 70 MWth (100,000 m2) in 2007.
Solarenergie 2007, Study by the Swiss bank Sarasin, November 2008 (Only available in German)
Solar thermal Markets in Europe. Trends and Market Statistics 2009, Study by European Solar Thermal Industry Federation (ESTIF), June 2009 (see the following link)
There are a number of mature markets like Israel, Austria, Barbados, China or Cyprus where solar thermal is used by a wide majority of people for heating the domestic hot water and sometimes for room heating.
One factor that shows the market penetration of this technology in a certain country is the total capacity installed per capita. In Cyprus there were 0.65 kWth in operation per capita at the end of 2007 followed by Israel (0.5 kWth/head), Austria (0.23 kWth/head) and Barbados (0.2 kWth/head). You find niche markets when looking at market penetrations such as in the United States with only 0.006 kWth per capita or in sunny South Africa with so far not more than 0.0036 kWth per capita. Also, there is still quite a large untouched potential worldwide in using solar thermal technology for cooling and for supplying process heat.
Further information: Solar Heat Worldwide, a study from the IEA Solar Heating & Cooling Programme, May 2009 (http://www.aee-intec.at/0uploads/dateien648.pdf)
0.7 kWth nominal solar thermal power equals 1 m2 of collector area.