The sun, already 4.5 billion years old, is an almost unlimited source of energy that makes life on earth possible. Although only a fraction of their energy reaches the earth, this proportion is around 10,000 times higher than the energy needs of the entire human race. However, awareness of the enormous potential of this energy source is by no means recent, as we know from the ancient Egyptians. What is new, however, is the progress and further development of solar cell technology, which has meanwhile made the targeted generation of electricity and heat an integral part of our houses.
In the following, our expert gives you an overview of the use of solar energy: whether photovoltaics, electricity storage or solar thermal energy – here you will find answers from solar cell technology expert Uwe Biermann!
the essentials in brief
- A solar module, consisting of several solar cells, converts sunlight into electrical energy.
- There are different cell types, the biggest difference being efficiency and production costs.
- Most consumers want a high degree of self-sufficiency, i.e. to cover as much of their own electricity consumption as possible with the electricity they produce themselves.
Work on improving and further developing photovoltaic technology is tirelessly pursued. The currently highest efficiency achieved by a solar cell is an impressive 46%, as the Fraunhofer Institute for Solar Energy Systems announced at the end of 2014. Even if the technical part is a closed book for many people, you should take the time to read a little more closely. Because only those who have background knowledge of technology and quality can distinguish good advice from poor advice and make the right decisions for their own system.
How does a photovoltaic system work?
The functional principle behind a photovoltaic system is actually quite simple: Sunlight is converted into electrical energy using solar cells. Several such cells form a solar module. The stronger the solar radiation, the more solar power can be produced. The direct current produced is converted into alternating current by means of an AC converter and can thus be fed into the power grid and consumed by you. The first decision is the type of solar cell technology.
Mono, poly or thin film – which solar cell technology should it be?
If you are interested in purchasing a photovoltaic system, you will have to decide what type of solar cells you want to invest in. A distinction is made here between thin-film cells, monocrystalline and polycrystalline solar cells. Thin-film cells differ fundamentally in structure from crystalline cells. They get by with comparatively little raw material, as a carrier material is coated with the semiconductors (eg silicon) that are crucial for photovoltaics. However, most solar systems on single-family homes work with crystalline cells made of silicon. Whether mono or poly is the right choice for you depends largely on the available roof area, since the cells differ primarily in terms of their efficiency and, accordingly, their purchase price.
Monocrystalline cells are more efficient than polycrystalline variants and thin-film cells, but they are also more expensive to buy. If, for example, a rather small area is available, monocrystalline cells are recommended in favor of the highest possible efficiency. But beware! The fundamentally better efficiency says nothing about the quality of the solar cells. Here, too, it becomes clear what a major role professional advice plays.
Two important parameters: self-consumption and degree of self-sufficiency
The self-consumption percentage indicates what percentage of the self-generated electricity is also used in the household. The degree of self-sufficiency, in turn, shows what proportion of the electricity consumed consists of self-produced electricity.
Although sounding similar, these values are not identical. A short example: If a household is completely supplied by its own energy production, the degree of self-sufficiency is 100%. If it also produces so much electricity that a proportion is also fed into the public grid, the self-consumption share would possibly be around 70% with complete self-sufficiency. What percentage of the energy requirement a photovoltaic system can actually absorb depends on your personal consumption as well as on the size and quality of the solar system. A pure photovoltaic system (without additional storage technology) can on average cover about 20-30% of the needs of a household. Although an electricity storage device is not absolutely necessary, it can significantly increase the proportion of self-consumption and the degree of self-sufficiency. Looking to the future, the demand for electricity storage will increase enormously. Be one step ahead and get an initial overview of electricity storage in photovoltaic systems.
With this knowledge and a few thoughts on your personal preferences, you can start any consultation on the subject of photovoltaic systems well informed.