ABSTRACT
A photovoltaic (PV) cell converts sunlight directly into electricity. A number of materials are photoelectric: Light is absorbed, and an electron acquires kinetic energy to move it to another energy level within the material. Today, the primary materials for PV cells are semiconductors, although researchers are trying other materials, even organic polymers. A PV cell is used in things from small items such as calculators and watches to large installations for electric utilities. The cost of PV systems has decreased dramatically so grid-connected PV has increased, and there are a number of applications in which they are the least cost, especially for standalone systems some distance from the utility grid, mobile jobs such as construction signs, and even for low power (50-200 W) close to the grid. A PV system has the following advantages and disadvantages:
PV has two other major advantages: PV and wind do not require water for the production of electricity, in contrast to conventional thermal steam plants, even those powered by nuclear reactors, and there is some load matching, for areas that need air conditioning and good solar resource, so peak loads for utilities can be reduced. There is still the problem of load for late afternoon and early evening.
