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What does the term photovoltaics mean?
Simply said, it applies to the conversion of solar energy to electricity (Greek phos=light, volt=voltage unit). In view of the fact that the amount of solar energy that falls to the Earth's surface is many times higher than the global consumption of electric energy, this technology provides a reliable solution for both energy and environmental problems. It is the only technology that does not produce any harmful substances or excessive noise and moreover its maintenance is not difficult.
What is the principle of photovoltaics?
A semi-conductor component, a so-called photovoltaic (solar) cell, is used to convert solar energy to electricity. This cell which is manufactured using crystalline silicon is used to absorb as much solar radiation as possible and at the same time to use the obtained energy most efficiently.
There are three basic types of photovoltaic cells:
- amorphous (efficiency 4 – 8%)
- polycrystalline (efficiency approx. 16%, the most suitable and efficient)
- monocrystalline (efficiency 13%, short-time efficiency in perpendicular light even 17 %)
Photovoltaic cells form the basic structure of a solar panel. The cells are connected using soldered circuits and they are capable of resisting even very unfavourable climatic conditions, due to the solid board that protects them from below and hardened glass that is used to protect them from above.
Photovoltaic panels provide very low direct voltage (12 V – 24 V), which is then converted to low alternating voltage (230 V) using a voltage changer (inverter).
Where can photovoltaic systems be installed?
A photovoltaic system functions best if it is designed in compliance with local conditions (dimensioning, solar cell location and method of use). The dimensioning requires knowledge of the purpose, considered power consumption (generation), type and operating hours of connected appliances, whether the system is connected to a network, or not, type of connection to the auxiliary energy source and other input data:
- number of hours of sunshine and intensity of solar radiation, which changes depending on atmospheric pollution (town, village, mountains)
- orientation – optimal to the south (possibly for automatically swivelling panels to the sun)
- panel inclination– for year-long operation, 38° towards the plane is optimum
- amount of shadowing obstacles – day-long sun exposure is necessary
Natural conditions:
The territory of the Czech Republic is exposed to 900 – 1,200 kWh/m2 a year. The decisive factors include cloud amount and atmospheric pollution. The amount of solar energy differs commonly by 10% in individual years. A photovoltaic system with an installed capacity of 1kWp is capable of providing 800 - 1,000 kWh of electric power a year in the conditions of the Czech Republic. In cases of improper orientation or shadowing, this figure can be significantly lower. The area of a system with a capacity of 1kWp depends on the efficiency of used components, it ranges between 6 and 9 m2.
