To generate heat and electricity from solar radiation, special equipment known as solar panels is used . Sometimes they are also called sunlife. According to the principle of work, they are divided into:
- photocells
- thermal collectors
In the first type, photocells, light and infrared rays are immediately converted into electricity. This is possible due to the semiconductor properties of pure silicon and some chemical compounds. When light hits a solar panel cell, a potential difference occurs, due to the pn junction, it creates a current. Small, with one no more than 0.6 V, regardless of its size. Individual cells connected in series make it possible to increase the output voltage. Therefore, they are called solar panels – that is, a number of identical elements.
Solar collectors have a liquid heat carrier that absorbs infrared radiation, heats up, expands and circulates in a closed system. They can serve:
- water
- mineral oils
- salt solutions
The coolant either heats water for heating and domestic or industrial needs, or turns the blades of turbines that generate electricity.
Varieties of solar panels
The industry produces three main types of solar panels:
- monocrystalline
- polycrystalline
- thin-film
In the first two, pure silicon is used with alloying materials deposited on the outer and conductive base on the back sides. Thin-film solar cells can be made of amorphous silicon or other semiconductor materials, as well as with additional sputtering and stream-sensitive elements. All types require a transparent outer layer of glass or polymers to protect against moisture and mechanical damage.
Solar panels are used in everyday life, for the industrial production of electricity and as batteries for spacecraft. Therefore, they have different requirements:
- Efficiency (COP)
- life time
- the weight
- price
The type of solar panels suitable for establishing is in each case chosen according to the ratio of these indicators. Also take into account:
- Temperature coefficient – dependence of power loss on fluctuations in ambient temperatures;
- Guarantee of generation – over time, the power decreases, but there is a period when these changes do not exceed 10-15%;
- Size – how much area of solar panels you need to have to produce 1 kW of electricity.
Monocrystalline – the most expensive, with the highest weight, but at the same time they have high efficiency (up to 25%), the smallest area for the production of 1 kW (up to 8 m²), the longest service life (20 – 25 years) with low power losses due to temperature and time.
Thin-film cheap and light, with a slightly larger working area single crystals, but the warranty period in them does not exceed 3 years and they are very dependent on weather conditions.
Polycrystalline solar panels require areas several times larger than monocrystals and films to produce 1 kW, but in other respects they are not much inferior to monocrystalline solar panels, and ten times better than film ones.
Photocells for thin-film solar cells are produced using:
- amorphous silicon
- indium copper diselenide
- cadmium telluride
To create pn junctions, semiconductor materials doped with phosphorus, gallium or sulfur. As an anode, molybdenum sputtering, oxides of zinc, tin or gallium are used. Metal plates serve as a cathode (current collector) This all work done in Solar energy in Pakistan.
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