2.1 RENEWABLE ENERGY SOURCE

2.1.1 Pv Cell

The solar cell is the basic unit of a PV system. An individual solar cell produces direct current

and power typically between 1 and 2 W, hardly enough to power most applications. Solar Cell or

Photovoltaic (PV) cell is a device that is made up of semiconductor materials such as silicon,

gallium arsenide and cadmium telluride, etc. that converts sunlight directly into electricity. The

voltage of a solar cell does not depend strongly on the solar irradiance but depends primarily on

the cell temperature. PV modules can be designed to operate at different voltages by connecting

solar cells in series. When solar cells absorb sunlight, free electrons and holes are created at

positive/negative junctions. If the positive and negative junctions of solar cell are connected to

DC electrical equipment, current is delivered to operate the electrical equipment.

2.1.2 Wind Energy Source

Wind power is the conversion of wind energy into a useful form of energy, such as using wind

turbines to make electrical power Small-scale. Wind power is the name given to wind generation

systems with the capacity to produce up to 50 kW of electrical power. Isolated communities that

may otherwise rely on diesel generators may use wind turbines as an alternative. Individuals may

purchase these systems to reduce or eliminate their dependence on grid electricity for economic

reasons, or to reduce their carbon footprint. Wind turbines have been used for household

electricity generation in conjunction with battery storage over many decades in remote areas.

Most small wind turbines manufactured today are horizontal-axis, upwind machines that have

two or three blades. These blades are usually made of a composite material, such as fiberglass.

The turbine's frame is the structure onto which the rotor, generator, and tail are attached. The

amount of energy a turbine will produce is determined primarily by the diameter of its rotor. The

diameter of the rotor defines its "swept area," or the quantity of wind intercepted by the turbine.

The tail keeps the turbine facing into the wind.

Grid-connected domestic wind turbines may use grid energy storage, thus replacing purchased

electricity with locally produced power when available. The surplus power produced by

domestic micro generators can, in some jurisdictions, be fed into the network and sold to the

utility company, producing a retail credit for the micro generators' owners to offset their energy

costs. Off-grid system users can either adapt to intermittent power or use batteries

photovoltaic or diesel systems to supplement the wind turbine. Equipment such as parking

meters, traffic warning signs, street lighting, or wireless Internet gateways may be powered by a

small wind turbine, possibly combined with a photovoltaic system that charges a small battery

replacing the need for a connection to the power grid.

2.1.3 Fuel Energy Source

A fuel cell is a device that converts the energy for fuel into electricity through a chemical

reaction with oxygen or another oxidizing agent. Hydrogen produced from the

steam methane reforming of natural gas is the most common fuel, but for greater efficiency

hydrocarbons can be used directly such as natural gas and alcohols like methanol. Fuel cells are

different from batteries in that they require a continuous source of fuel and oxygen/air to sustain

the chemical reaction whereas in a battery the chemicals present in the battery react with each

other to generate an electromotive force (emf). Fuel cells can produce electricity continuously for

as long as these inputs are supplied

The first fuel cells were invented in 1838. The first commercial use of fuel cells came more

than a century later in NASA space programs to generate power for probes, satellites and space

capsules. Since then, fuel cells have been used in many other applications. Fuel cells are used for

primary and backup power for commercial, industrial and residential buildings and in remote or

inaccessible areas. They are also used to power fuel-cell vehicles, including forklifts

automobiles, buses, boats, motorcycles and submarines.

There are many types of fuel cells, but they all consist an cathode an electrolyte that allows

charges to move between the two sides of the fuel cell. Electrons are drawn from the anode to the

cathode through an external circuit, producing direct current electricity. As the main difference

among fuel cell types is the electrolyte, fuel cells are classified by of electrolyte they use

followed by the difference in startup time ranging from 1 sec for PEMFC to 10 min for RSOFC.

Fuel cells come in a variety of sizes. Individual fuel cells produce relatively small electrical

potentials, about 0.7 volts, so cells are "stacked", or placed in series, to increase the voltage and

meet an application's requirements. In addition to electricity, fuel cells produce water, heat and,

depending on the fuel source, very small amounts of nitrogen dioxide and other emissions. The

energy efficiency of a fuel cell is generally between 4060%, or up to 85% efficient in

cogeneration if waste heat is captured for use.