The schoolyards of an all-day school in a small town in southern Germany were hardly used on hot days last summer. This was because they offered no protection from direct sunlight. A normal roofing would have resulted in a dark, unattractive cave that would also have had to be lit during the day. No funds were available for such a reconstruction of the playground.
Solar power finances investment
The municipality contacted GridParity AG from Karlsfeld near Munich to investigate the possibility of partially financing the investment through income from electricity.
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The concept developed by GridParity's engineers is based on semi-transparent double-glass modules. They let in a lot of light, and the play of light and shadow under the solar roof also creates an attractive space.
The roof structures should consist of laminated timber beams treated with multiple layers of wood preservative, which are placed on galvanised steel tubes. The electrical connections are safely routed in these tubes to the cable ducts in the ground.
Subsequent extensions possible
The construction is modular and, depending on the available funds, can initially consist of a few components that can be expanded later.
In the first phase, the offer provided for four gable roofs with a connected output of 36 kilowatts and an annual electricity production of around 38,000 kilowatt hours. The investment costs were quoted at 60,000 euros net. The construction team of the municipality was prepared to carry out the installation under expert guidance.
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The remuneration offered by the municipal utilities allowed for a payback period of about eight years. This did not include subsidies from various housing development programmes.
Upgrading a featureless school playground
The direct economic benefit is only a secondary aspect. The example impressively shows the benefits of solar roofing as a source of shade and shelter from rain, snow or hail.
Furthermore, the reduction of overheating of large paved areas in cities also plays an increasing role. In addition, there is the visual enhancement of the previously featureless schoolyard, which in the future can be used outside regular school hours, for example, for games such as table tennis. (mfo)
This article is an abbreviated version of a specialist article that will appear in the April issue of our German sister publication photovoltaik. The author is Erich Merkle, Managing Director of the module supplier GridParity AG from Karlsfeld near Munich.
Video: Erich Merkle of GridParity:
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