Do you have a battery-free pocket calculator? Then you probably own a solar cell – a piece of equipment which converts sunlight into electricity. Solar cells have been around for a while, but they are still relatively expensive even though the raw material, sunlight, is free and unlimited in many places around the world. The sun provides our planet with 500 million TWh of energy per year. This is 5,000 times more than is used by humans at present.
The solar cell industry is really keen on pushing down the cost of equipment, and although solar cells are expensive, there is a great deal of interest in them. Many countries provide financial support for individuals who install solar panels. The hope is that technical development will speed up if there is a demand for the products. And people buy more when prices are lower.
Swedish solar cell research won early recognition throughout the world. The first system using solar cells to produce heat with the aid of reflectors, known as the Photo Voltaic-Thermal system, was built in 1982 at the Studsvik laboratories. The technology was developed further in the 1990s by Vattenfall in partnership with several universities. Lund University opened its new Solar Lab in 2006, with the aim of evaluating various types of equipment and reflectors.
Water-cooled solar cells produce electricity and hot water
A company which has commercialised the technology of producing electricity and hot water simultaneously is Arontis Solar Concentrator, which developed a ”smart” solar collector supplied in flat-pack format. It can be fitted to a roof by a single person, an idea taken from IKEA.
The principle behind the company’s Solar8 system is based on the use of reflectors to focus sunlight onto highly-efficient solar cells. The reflectors concentrate the sunlight projected onto the solar cells eight times, which makes them so hot that they have to be cooled down. The cooling system uses water, which is then used to heat water in the building. The performance of the system is high, both in the production of electricity and hot water.
A Solar8 is five metres long and has an effective surface of 4m2. A number of such reflectors can be linked together, which makes the system suitable for facilities where large quantities of hot water are required, such as hotels, swimming pools or sports facilities.
The greatest potential for Arontis solar cells is in countries with a great deal of sunshine all year round. There is considerable interest in the system in Sweden, as a supplement to other energy supplies. The World Heritage Museum in Skule has two Solar8s which generate electricity and provide hot water at 55°C. The system functions best in summer, when it provides the museum with all the hot water it can use. It also generates surplus electricity which is delivered to the national grid. In winter, the museum is heated by a pellet-fired boiler and the Solar8s are used to supplement this system. Lund University has ordered Solar8s, even though the price of the reflectors is high in comparison with conventional solar cells. The great efficiency of the installation still makes it a profitable investment. Right now, Arontis is in process of fitting demo-systems at two installation firms in Germany and Greece.
Tennis players at Båstad take energy from the sun
As of the 2007 competition season, the tennis stadium in Båstad and the Hotel Skansen received up to 10 percent of their electricity supply from the sun. The Japanese solar cell manufacturer, Sharp, supplied a system consisting of 216 monocrystalline panels, each with an output of 180 W. The tennis stadium expects the systems, which cover an area of 281 m2, to produce 40 MWh of electricity per year. The hotel is using the investment as part of its marketing, and has fitted a display in the entrance which shows guests how much electricity is being supplied. The total amount invested was approximately SEK 10 million.
This article was first published in Advantage Environment printed in February 2008