Utilization of sunlight is easy with a photovoltaic cell. Photovoltaic cell directly converts solar energy into electric energy. The photovoltaic effect can be observed by the performance of material in sunlight. That’s why Photovoltaic cells are made of semiconductors that generate electric energy when they absorb photons (sunlight). The generated energy can be collected on batteries. Many developed and developing countries have installed solar power plant for electric conversion. Although solar power requires a lot of space. But efforts are being made to reduce space requirement and improve output through various technical innovations. The conversion of light into electric energy can be easily described by the principle of photovoltaic cells.
Photovoltaic(PV) cell principles:
The solar energy from the sun enters through earth’s atmosphere, and harmful rays (smaller wavelength waves) are absorbed by the ozone layer. When photons strike photovoltaic cell material creates high energy free electron. The p-n junction phenomenon is described below:
In modern photovoltaic cells, silicon is used as a semiconductor. each one of the four valence electrons in semiconductor material tied in a chemical bond, and no free electron available. This electron relatively bounded with the atom(even in room temperature). If we divide the material into two opposite sides than:
If side one is doped with 5 valance electron material like arsenic and phosphorus, there will be an excess electron generate on this side. The dopants which donate their free electron to the semiconductor crystal are known as donor. This side becomes an n-type semiconductor. This electron is free to move in the lattice structure of the material. These generated electrons cannot produce electricity in the silicon crystal alone.
The second side of semiconductor material is doped with 3 valance electron material such as boron. These create the deficiency and it’s known as the hole. This side of the piece is known is the p-type semiconductor.
The combination of p-n type semiconductor is known as the p-n junction. In this piece, the electron moves n side to p side. And holes flows p to n direction. These processes generate an electric field and responsible for electric conversion.
Here are 15 important facts about PV cells:
- Photovoltaic cells are made of semiconductor material and these material generate electric when they absorb electromagnetic radiation(light).
- A single photovoltaic cell produces very less amount of energy that’s why the combination of such cells are designed to improve power output. This combination of PV cells is known as a solar module.
- Since in early stage (development), the efficiency of a solar PV cell was limited with 10 %.
- Supposedly the efficiency of the PV cell is 25%. But in operating condition at the installed site, actual gain efficiency is between 10-18%.
- Theoretically, it’s considered that increasing temperature also increases efficiency. but actually, it decreases with increasing temperature (after critical stage).
- The high temperature is not the requirement of a photovoltaic cell. It requires electromagnetic radiation for energy conversion.
- Space crafts, radio ship navigation and weather monitoring is best-known examples of PV system.
- Most PV cells are expensive available in market reason is simple. This silicon is expensive material. Refining and purifying increases the total cost.
- A rooftop is an adaptable place for any small plant or industries for installing PV system.
- The combination of PV cells is designed to protect the system from corrosion and other problems.
- PV cell only operates in sunlight; hence it requires an energy efficient electric storage system.
- In a normal sunny day, 0.5-2kwh electricity can produce on 1-meter square area.
- Infrared radiation with larger wavelength has no PV effect in semiconductor materials.
- For space and interplanetary missions, the application of PV system is most important.
- The photovoltaic cell produces electric in form of DC(direct current ).
If tracking system is not used it decrease the efficiency of the PV system. and also many atmospheric factors affect power output. Comment your thoughts about PV cells and PV system.