The solar air collector of Kollektorfabrik

Kollektorfabrik has laid the foundations to produce a solar air collector which meets the technical requirements of efficient solar energy usage. This collector complies also with the needs of installers and craftsmen, customers and investors.

The field test in private households with heat exchangers for domestic hot water production and direct use of air for heating was started in September 2008. Larger collector fields for solar heat for industrial processes are currently under negotiations.

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Fig 2. A demonstration field of an early prototype stage with five modules.

Characteristics of the air collector of Kollektorfabrik

• In comparison with unglazed or flat-plate collectors a higher temperature level can be supplied for processes by means of vacuum tubes.

• For space heating applications in private households a further system with heat exchanger and fan is available.

• Optimized area ratio between absorber and header surface.

• Different geometries and sizes are possible.

• Different designs are possible, for e. g. header with different colors and different sizes.

• Safe and fast installation without the need for long instructions.

• Lightweight construction (ca. 20 kg/m2) for loadsensitive sub-structures.

• The solar thermal air collector of the Kollektorfabrik has a total area of ca. 9.2 m2. A typical household would use about two or three air collector modules for domestic hot water production and space heating.

• A heating system perfectly fitted around roof windows and a smooth adaptation of the dormers of a roof can be realized by means of vacuum tube of different lengths.

Sustainability

• The usage of decentralized renewable energy represents a major contribution to secure environment, supply independency and to deal with depleting resources. The use of solar thermal heat is a cooperatively easy and effective way to do so. With the introduced collector, high solar fractions are easy to realize thus achieving an important impact on the energy supply chain.

• From an economic point of view, a reasonable investment is strictly connected to its life time, its total costs and total benefits of ownership. By integrating the solar air collector into a suitable application not only the energy supply is secured in an ecologically way. The economic investment also achieves sustained success.

Reliability

• High solar fraction of typical solar thermal systems comes often along with a partial energy overrun in summer. Ideal, easy to run applications need the most heat when the radiation is at the maximum (e. g. solar cooling). If this is not the case, additional components are — depending on the size of the collector field — absolutely necessary to deal with stagnation problematics in summer. These would be e. g. space consuming big storages, advanced intelligent controller with nightcooling (heat rejection), redundant pumps, electricity backup unit, rating rules for expansion vessels, special connecting schemes and advanced solar fluids.

Whereas the collector developed by Kollektorfabrik is intrinsically safe. If the system, a sensor or a actuator fails, even if the system was not installed properly, the collector does not deteriorate during stagnation condition neither does it damage any other part of the system.

• Therefor, no particular measures are necessary to guarantee safety during weekend, lunchtime, process interception or vacations of companies, schools, public buildings etc. The solar air system can resume after a break and even start from full stagnation and inner absorber temperatures up to 250°C without the risk of thermal shocks.

• The collector of Kollektorfabrik meets the requirements based on the test conditions of the European Norm for collector testing (EN 12975-2).

Cost effectiveness

• Kollektorfabrik has developed a long-lasting intrinsically safe collector with the focus on maximum energy output at high temperatures (30°C — 130°C) in the cold and hot seasons.

• Some details were implemented that enable an easy and fast mounting of the collector, thus reducing costs connected to installation.

• Special attention was given to make the collector lightweight so it can be moved without a crane. A Team of two persons can easily transport the collector to a roof e. g. through a roof light and install it. This lowers the costs of installation.

• Kollektorfabrik initiated the development of a fan with extremely low power consumption which could even be driven as standalone system in combination with pv-cells.

• With the scientific assistance of the Fraunhofer Institute for Solar Energy Systems the aerodynamics were optimized through CFD-Simulations and proofed on the test facilities of the Fraunhofer ISE. This way, a maximum benefit can be achieved at a minimum auxiliary power.

• There are several possibilities to store the heat from hot air. It could be transferred into water and stored in a water tank or it could be stored directly and cost effective in the thermal mass of walls and floors or lossless in sorption materials.

Different possibilities to influence the technical and optical appearance like color shadings, different length of the tubes, different sizes and different angles of the tubes make the solar air collector field of Kollektorfabrik unique. It becomes a part of the house, the building or the application the collector is made for. This grades up the application itself, modernizes the building and makes the object of the heat supply more valuable.

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