LitEratUre RevieW

Research

            Photovoltaics are best known as a method for generating electric power by using solar cells to convert energy from the sun into electricity because of the increasing efficiency and ease of use. PV modules come in a huge variety of types and sizes and are used as the power solution for many different applications including residential and commercial grid-tie solar power systems as well as off-grid and industrial systems.

            Made most commonly using the  Silicon Crystal , solar cells essentially create electricity by converting photons of light into electrons. The "photovoltaic effect" occurs when photons of light from the sun strikes these cells, a portion of the energy is absorbed into the silicon, displacing electrons which then begin to flow. In order to harness this flow, the electrons are drawn into a magnetic field generated by positively- and negatively-charged metal contacts on the top and bottom of the cell. producing direct current, or DC, electricity. Using a DC to AC inverter, the DC current is converted to alternating current, or AC, which can then be used to power electrical appliances.

            Solar cells (SC) produce direct current electricity from sunlight, which can be used to power equipment or to recharge a battery.  Nowadays, the majority of photovoltaic modules are used for grid connected power generation. In this case an inverter is required to convert the DC to AC.

            A photovoltaic system consists of multiple components, including cells, mechanical and electrical connection and mountings and means of regulating and modifying the electrical output. Due to the low voltage of an individual solar cell typically 0.5V, several cell are combined into photovoltaic modules, which are in turn connected together into an array.

            Photovoltaic power systems are generally classified according to their functional and operational requirements, their components configurations and how the equipment is connected to other power sources and electrical loads. The three principal classifications are grid connected or utility interactive systems, photovoltaic hybrid system and PV stand alone systems. Photovoltaic system can be design to provide DC and AC power service, can operate interconnected with or independent of the utility grid and can be connected with other energy source and energy storage system. 

Advantages Photovoltaic

• No pollution and totally silent in process energy compare wind and water based from turbine and very noisy
•  Low cost maintenance and have a long lifetime
•  Not required large space to build. The solar panel can put on the roof top
•   Appropriate to use in Malaysia

The figure above show the solar panel which cell connected in series and parallel

           

 Thermoelectric is a device that converts heat into electricity and it is a two-way process. It can refer either to the way a temperature difference between one side of a material and the other can produce electricity, or to the reverse: the way applying an electric current through a material can create a temperature difference between its two sides, which can be used to heat or cool things without combustion or moving parts.

The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice-versa. A thermoelectric device creates a voltage when there is a different temperature on each side. Conversely, when a voltage is applied to it, it creates a temperature difference. At the atomic scale, an applied temperature gradient causes charge carriers in the material to diffuse from the hot side to the cold side.

            Thermoelectric modules are solid-state heat pumps that operate on the Peltier effect. A thermoelectric module consists of an array of p-type and n-type semiconductor elements heavily doped with electrical carriers. The array of elements is soldered so that it is electrically connected in series and thermally connected in parallel. This array is then affixed to two ceramic substrates, one on each side of the elements. Electrons can travel freely in the copper conductors but not so freely in the semiconductor. As the electrons leave the copper and enter the hot side of the p-type, they must fill a "hole" in order to move through the p-type. When the electrons fill a hole, they drop down to a lower energy level and release heat in the process. Essentially the holes in the p-type are moving from the cold side to the hot side. Then, as the electrons move from the p-type into the copper conductor on the cold side, the electrons are bumped back to a higher energy level and absorb heat in the process. Next, the electrons move freely through the copper until they reach the cold side of the n-type semiconductor. When the electrons move into the n-type, they must bump up an level in order to move through the semiconductor. Heat is absorb when this occurs. Finally, when the electrons leave the hot side of the n-type, then can move freely in the copper. They drop down to a lower energy level and release heat in the process.