Solar Technology / Photovoltaic

Fossil energy resources are limited. The huge potential of using the unlimited energy generated by the solar radiation is world-wide available though.

Current and future developments in the field of solar technology are able to generate large parts of the required energy in a sustainable and environmentally friendly way. To forward that, the expansion of alternative energy sources, like solar power, is also politically being supported.

The costs for a lot of goods and services are already increasing now because of the shortage on fossil commodities. That is revealing great chances for solar energy systems. Another reason is the high potential of these systems, which feature tremendous improvements in its developmental stage.

The term solar technology contains two possibilities of active usage of solar energy.

Solar heat:

In the field of solar heat the solar radiation is being used to warm up liquids in a cycle. This is being realized by the use of varying kinds of collectors, like for instance flat plate or evacuated tube solar collector. The storage heating tanks, fed by this energy, are then being able to be connected to the service water system or/and the solar backup heating.


Photovoltaic is equally representing a section of solar technology, its name, by the way, is based on the ancient Greek word “phos” = light. The second part of the name is referring to Alessandro Volta and his unit for potential, volt.

Photovoltaic is using the direct and diffuse radiation of the sun to generate electricity with assistance of photovoltaic cells. In doing so, the sunlight is being transformed into electricity by silicon-based solar cells.

The origins of photovoltaic are going far back in history. Physicist Becquerel described the photoelectric effect in his works already in the year 1839. Nevertheless, the first photovoltaic systems, matured enough for usage, were firstly being developed in the late 20th century. In the end of the 1950s, the breakthrough succeeded through the key developments in the field of satellite technology and aerospace.

If the justification of the modules is made in a proper way, photovoltaic systems are reaching high lifetimes associated with a low need of maintenance and a high cost-effectiveness.

Technology of photovoltaic

On the international market are currently more than 100 manufacturers present, who offer way above than 1,000 different solutions in the area of photovoltaic. Besides the monocrystalline and polycrystalline silicon cells, the thin-film cells are belonging to the mostly used technologies.

The monocrystalline silicon cells are silvery shiny slices with a thickness of 0.2 to 0.3 mm. Basis of the production are single crystals of high-purity silicon.
The monocrystalline cells are requiring higher production costs in comparison with the other cell-technologies because of the special way of being manufactured.
With a current efficiency of up to 20%, an area of about 7-9 m² are necessary to produce 1 kWp.

The polycrystalline silicon cells are inter alia produced by the ingot casting process. In this process the intensely heated silicon is being cooled down in a casting mold, whereby irregular crystals are emerging. Polycrystalline silicon cells are achieving an efficiency of 16% and are less expensive to produce as the monocrystalline cells regarding to the costs and energy.

The thin-film cells, amongst others containing of copper-indium-diselenide (CIS) or cadmium telluride (CdTe), are achieving an efficiency of 9 to 12 %. They are characterized by a slight loss of power if they are exposed to high temperatures and a higher tolerance against shading in comparison to the silicon cells. A further increase of the potential of efficiency of the copper-indium-diselenide cells can be expected.

Choosing the right modules is, besides the technology, also depending on other factors. These include the build quality, seal of approval or certification of the products and manufacturers. These factors are mostly an indication for the performance ability of the offered products. So is, for example, the tolerance of efficiency over ±5%, you should refrain from the purchase to prevent profit cuts.
You should also pay attention on the temperature coefficient as well as on the storm and hail resistance according to EN 61730.

Key standards in the field of photovoltaic modules are amongst others:

DIN EN 61215: Crystalline silicon terrestrial photovoltaic (PV) modules
Design qualification and type approval

DIN EN 61646: Thin-film terrestrial photovoltaic (PV) modules
Design qualification and type approval

DIN EN 61730: Photovoltaic (PV) module safety qualification – part 1: Requirements for construction and part 2: Requirements for testing

DIN EN 50380: Datasheet and nameplate information of photovoltaic modules

A reputable quality label of the branch is:

RAL-GZ 966: Classification and test specification

Funding and Permissions

Europe-wide, there are several political initiatives, comparable with the Renewable Energy Law (EEG) in Germany, to support the investments in solar energy. Based on the young stage of development of the branch of photovoltaic, the guaranteed feed compensations are around 30 Eurocent per kilowatt hour. This amount will be generally warranted over a period of 15 to 20 years.

Furthermore, there are several investment programs of single branches for roof conversions, for instance for an asbestos reduction of production halls, to gain more attraction. These programs refer to local, national and even international funds.

Use your opportunities to be state-aided and promote the expansion of the branch of renewable energies in Europe.

The construction of a photovoltaic installation on a flat roof, respectively façade does not require a building permit in Germany. However, exceptions can occur through several circumstances.

In excerpts containing:

  • Impacts on the monument protection
  • Design regulations
  • Statements of the land-use plan
  • Distance space or
  • Local differing regulations etc.

In any case, being able to realize a free-standing photovoltaic system is requiring a building permit.
Besides the clarification of the building permit, it is necessary to agree on a feed-in regulation with the local power supply company. But before entering into this engagement it will be necessary to validate the closest grid connection points.

Cost-effectiveness and financing

The cost-effectiveness of a photovoltaic park is characterized by several factors. That is enabling the possibility for the investor to perform little modifications during the planning to gain a change in the yield.

In addition to the pure project size, which can ensure discounts, it is determining to choose the right module technology. In this context the question of the origin of the distributor is occurring. Foreign suppliers are frequently being able to offer installations at a reduced rate. Nevertheless, some banks have a hard time financing exotic modules.
A second important aspect in planning a photovoltaic installation is choice of the inverter. One of his main tasks is the accomplishment of the sinusoidal electricity feed-in as well as the function control of the installation. Beyond that the inverter is ensuring the steadily adjustment of the photovoltaic installation at the optimal operating point (MPP = Maximum Power Point).
That’s why an wrong dimensioned inverter can be responsible for massive profit cuts.

Besides the costs for the modules it is necessary to pay attention to several other points to calculate the investment costs:

  • Inverter
  • Costs of the site
  • Foundations
  • Subconstruction
  • Transformer
  • Perimeter fence or enclosure
  • Installation and other costs

To calculate the cost-effectiveness a consideration of the accruing operating costs is required. Relevant, beside the economic matters of expense, are the maintenance, repair and insurance. The conventional expected operating costs are approximately 2 % per year of the investment costs.

The whole expenses are being confronted with the expected income of the photovoltaic park. That is why a simulation, respectively a calculation of expected yield is especially important for determination of the cost-effectiveness of the park. First basic approaches are made by weather maps. But for a detailed planning a precisely made simulation und consideration of weather data, the surrounding and the slope of the modules is required. Considerations of shading of the installations should be made too.

If you have the intention to apply for a credit, you should, at least, be able to give in a complete offer with the specifications of the used components and the wiring plan. The calculation of the cost-effectiveness on the basis of the predicted average annual yield under consideration of the expected operating costs is the second cornerstone for a succeeding credit application. Some banks demand the acquisition of a maintenance agreement if you are going to build a bigger photovoltaic installation to warranty minor downtimes and thereby the availability of the installation.