Forschungsgruppe-NET - Hochschule Offenburg

Solar Heat

The total investment costs shown in theses bars are segmented to indicate the costs of the individual components and the planning.
The cost of the usable solar heat is given in price per kWh of usable heat. It is calculated by the ratio of the overall system’s costs (investment cost of planning and setting up of the solar thermal system as well as the investment loan at 6% interest and an estimated lifecycle of 20 years) and the annual solar yield of the system.

The average investment costs for the planning and building of the solar thermal systems were about € 681/m² of collector surface (incl. VAT). The diagram on the right (top) shows the specific costs per m2 of collector surface for each of the seven systems. They are subdivided/ separated into the individual costs of the system component and planning. It reveals quite a large variety concerning both the overall investment and the costs of the components. This is chiefly determined by the conditions of installation, such as the technique of mounting the collectors (flat or tilted roof/ in- or on-roof) or whether the existing components (water tanks) were used. Holzgerlingen was the system with the lowest specific costs, which is mainly due to the fact that it is easier to connect to the local heating network than it is to connect to the potable water system.

Freiburg Wilmersdorfer Straße featured the highest specific costs. Here, the complex piping and the collector elevation were responsible for the higher costs. As the collector field had to be mounted on two rooftops, the system required two ascending pipes in addition to the underground ones.

The bottom diagram shows the average as well as the minimum costs for usable solar heat of the solar thermal systems.

Freiburg-Vauban was the most cost-effective system largely due to a very high capacity utilization. The costs of the system at Holzgerlingen were the highest of all our systems because it feeds into the local heating network rather than heating potable water like the others. This accounts for Holzgerlingen’s low solar yield.

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