Solar coverage

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As solar fraction (also solar coverage or solar coverage ) is typically used in the proportion of a building or property amount of energy referred to, which is provided by a technical converting solar radiation. The conversion into usable energy can be done by a solar thermal system into thermal energy (heat) or a photovoltaic system into electrical energy (electricity). The thermal energy can then z. B. can be used to heat a building. Passive solar yields , which also represent part of the energy that can be used in a building, are not taken into account in this analysis. The solar share of coverage is a component for a typically annual balancing of the amount of energy converted in a building. Basically, the following applies: higher values ​​represent a higher proportion of solar-based energy in the supply of a building with heat and electricity and thus a reduced use of other energy sources that typically use fossil fuels .

General

The solar coverage is used for the needs-based planning of solar systems and is a measure of the energetic (in) dependence on other energy sources than the sun.

Differentiation of solar coverage for buildings

  • Water heating,
  • Heating for space heating,
  • Total heating requirement,
  • Power generation,
  • Total energy requirement.

This value depends on the one hand on the size of the storage ( hot water storage tank or accumulators ), the size of the harvested areas ( solar collector area or area of ​​the photovoltaic modules ) and on the other hand on the energy demand. In addition to the total yield, there is another important parameter for assessing a solar system. Energy losses in the system, such as storage losses, are taken into account.

economics

The solar coverage is still the sole measure of the economic efficiency or quality of a system, because other boundary conditions have to be considered at the same time. The value depends, among other factors, on the size of the system, the location and orientation of the collectors, the size of the storage tank and the energy demand. A solar coverage of 100% would mean that the entire energy requirement of the system can be covered by solar energy. In the case of a solar thermal system in Europe, this would mean that the entire heat demand can still be met on a cold winter's day. On summer days, however, the same system would produce a very large surplus that could not be used because the system would frequently stagnate . The system would have to be greatly oversized in summer and could not necessarily be operated economically. A high degree of coverage is therefore not always an advantage. If a very high degree of coverage is to be achieved nonetheless, solutions in a local heating network and seasonal storage are available .

With regard to the planning of a solar thermal system, it is important to find a balanced compromise between yield, i.e. the amount of heat provided by the solar energy and the degree of solar coverage. A good compromise between yield and solar coverage is usually also a good compromise between investment costs for the solar system and saved conventional energy.

Storage

Since the sun does not always shine, storage tanks are used to store heat or electricity, which increases these values. By designing storage sizes, both thermal and electrical, the solar coverage of a system can be significantly influenced. Storage systems make it possible to supply load peaks as well as to store solar irradiation peaks in order to bring the energy supply closer to a base load level. This reduces the dependency on the supply system. Photovoltaic systems in Germany are largely determined by the conditions of the Renewable Energy Sources Act . The market and technology development of battery storage systems is to be stimulated through a market incentive program of the Federal Ministry for Economic Affairs and Energy. The investment in battery storage systems is supported by repayment grants from KfW .

Typical values

On the hot water side, it is common in Germany to design single-family houses with 50 to 60 percent solar coverage, and in multi-storey apartments with 30 to 40 percent. These values ​​come from trying to find a balance between investment costs and usable income (hot water). It is not always possible to specify standard values for solar thermal heating support , as the degree of coverage at this point is largely determined by the building. In the standard installation of single-family houses, this is around 15 to 25 percent of the total heating requirement, but can be much higher in so-called solar houses . In a plus-energy house , the value can be over 100 percent, depending on the energy sources used.

literature

  • Expert Practice Lexicon: Solar Energy and Solar Techniques. 2nd Edition. expert Verlag, 2006, ISBN 3-8169-2538-3 .
    • Annual coverage rate of a solar hot water system. P. 148.
    • solar coverage rate. P. 273.

Web links

Individual evidence

  1. ^ Heinz P. Janssen: Energy advice for residential buildings. Hamburg 2010, ISBN 978-3-481-02635-6 , p. 204.