Solar Cell
A solar cell or photovoltaic cell is an electronic device that converts solar energy into electricity by the photovoltaic effect. Assemblies of cells are used to make solar modules, or photovoltaic arrays. Solar cells are used for powering small devices such as electronic calculators. Photovoltaic arrays generate renewable electricity, particularly useful in situations where electrical power from the grid is unavailable such as in earth-orbiting satellites and space probes, remote radiotelephones and water pumping applications.
The photovoltaic effect was first discovered in 1839 by French physicist A. E. Becquerel. However, it was not until 1883 that the first solar cell was invented, by Charles Fritts, who coated the semiconductor selenium with an extremely thin layer of gold to form a junction. The device was only around 1% efficient The modern age of solar power technology arrived in 1954 when scientists of Bell Laboratories accidentally found that silicon doped with certain impurities was very sensitive to light.
The p-n junction
The most commonly known solar cell is configured as a large-area p-n junction made from silicon. The junction is made by diffusing an n-type dopant into one side of a p-type wafer (or vice versa). When photons are absorbed by doped semiconductor, their energy is given to electrons in the crystal lattice. The energy given by the photons "excites" electrons into the conduction band, and they move freely within the semiconductor forming an electric current. The electric field established across the p-n junction creates a diode that promotes this current to flow in only one direction across the junction.
To understand the electronic behaviour of a solar cell, it is useful to create a model which is electrically equivalent, and is based on discrete electrical components whose behaviour is well known. An ideal solar cell may be modelled by a current source in parallel with a diode. In practice no solar cell is ideal, so a shunt resistance and a series resistance are added to the model.
The equivalent circuit of a solar cell and the schematic representation of a solar cell for use in circuit diagrams
From the equivalent circuit it is evident that the current produced by the solar cell is equal:
where
I - output current
IL- photogenerated current
ID - diode current
ISH - shunt current
Solar cells are often electrically connected and encapsulated as a module. PV modules often have a sheet of glass on the front (sun up) side, allowing light to pass while protecting the semiconductor wafers from the elements (rain, hail. etc. ) Solar cells are also usually connected in series in modules, creating an additive voltage. Connecting cells in parallel will yield a higher current. Modules are then interconnected, in series or parallel, to create an array with the desired peak DC voltage and current.
To make practical use of the solar-generated energy, the electricity is most often fed into the electricity grid using inverters (grid-connected PV systems).
Answer the questions:
1. What is a solar cell?
2. What is a difference between a solar cell and a photovoltaic cell?
3. What is the name for assemblies of solar cells?
4. Who discovered the photovoltaic effect?
5. Where and when was the modern solar technology developed?
6. In which way is the electric current produced in a solar cell?
7. What is usually used to protect photovoltaic modules from weather conditions?
8. What device do you need to connect a photovoltaic module to the mains?
Translate into Polish
1. Solar cells are classified into three generations depending on technologiesused to manufacture them.
2. First generation cells consist of large-area, high quality and single junctiondevices.
3. First generation technologies involve high energy and labour inputs whichprevent any progress in reducing production costs.
4. Second generation solar cells have lower production costs, but much reducedefficiency compared to first generation.
5. Third generation technologies aim to enhance poor electrical performance ofsecond generation while maintaining very low production costs.
Translate into English:
1. Aby zmienić energię słoneczną w energię elektryczną, potrzebne jest fotoogniwo.
2. Moc wyjściowa paneli słonecznych jest mierzona w watach lub kilowatach.
3. Zapotrzebowanie energetyczne jakiegoś urządzenia jest mierzone w watogodzinach, kilowatogodzinach lub w kilowatogodzinach na dzień.
4. Inwertory są stosowane do podłączenia paneli słonecznych do sieci elektrycznej.
5. Można powiedzieć, że fotony absorbowane w półprzewodniku tworzą mobilne pary elektron-dziura.
6. Foton musi mieć wystarczająco dużą energię, aby mógł przenieść elektron z pasma walencyjnego do pasma przewodnictwa.
elektrapsk