Laser technology improves solar collectors

Whereas photovoltaic cells transform the sun's energy directly into electricity, solar collectors use a liquid which is heated by solar radiation. The thermal energy captured by this process can be used for heating water in homes or in larger units for driving power generators. At the heart of larger units are glass tubes filled with a liquid, which is heated by solar radiation. These glass tubes must be joined together, and according to the Laser Zentrum Hannover (LZH), laser technology is best suitable for this process. A new project between the LZH and several industrial partners aims at proving that laser joining of glass tubes has many advantages over the conventional flame method, and that it is more cost-efficient for the glass industry.

The disadvantages of the conventional flame technique can partly be compensated for by trained staff, but they can also lead to product failure. During the joining process, impurities may occur in the joining zone, which cause considerable variations in the glass quality. Also, the heat input is difficult to regulate when using the flame technique. This is not the case with laser technology.

The advantages of laser joining of glass tubes are mainly temperature control, temperature distribution and automation. Additionally, in contrast to the flame joining, the laser joining technique prevents condensation and deposition in the glass tube, thus offering better quality. In combination with chemical resistant and robust borosilicate glass, breakage is significantly reduced, which in turn leads to a considerably lower reject rate.

The 'Lafuelsol' project is funded by the German Federal Ministry of Education and Research (BMBF). The Karlsruhe Institute of Technology administrates the project via its Production and Manufacturing Technologies division.

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