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.
