Photovoltaic System Research Paper

CHAPTER 3

PHOTOVOLTAIC SYSTEM

AND

WIND ENERGY SYSTEM

3.1 Photovoltaic system

The photovoltaic system was invented by Edmund Becquerel in 1839. He introduced the fact that some certain materials have small amounts of electric current when they are exposed to sunlight. In 1905, Albert Einstein explained the nature of the light and the photoelectric effect which becomes the main principle for the photovoltaic technology. In 1954, Bell Laboratories first built photovoltaic module In photovoltaic system, one or more number of solar panels is connected to convert the light energy into electrical energy. It has many having more components which are photovoltaic modules, electrical connections and mechanical connections. 3.2.1 Photovoltaic arrangements:

The output power of PV array can directly feed to a load like DC motor for agricultural applications.

3.2.2 Working of PV Cell

The main principle of PV cell operation is photoelectric effect. Photoelectric effect is a effect caused by the absorption of sunlight of a certain wavelength by the metallic matter, due to that electron gets ejected from the conduction band. So, in a PV cell, when sunlight knocks its surface, some portion of the solar energy is absorbed in the semiconductor material. Fig 3.3 Working of PV cell

When absorbed energy is greater than the energy of band gap of the semiconductor the electron jumps from valence band to the conduction band. Due to this electron- hole pairs are created in the illuminated region of the semiconductor. In the conduction band, the electrons are created and now they are free to move. These free electrons are forced to move in a particular direction by the action of electric field present in the PV cells. These flowing electrons comprise current and can be drawn for external use by connecting a metal plate on top and bottom of PV cell. This current and the voltage produces required

Battery

In present society the main role of battery is important as energy carrier, due to present devices are used for every day. The demand of batteries is increased rapidly due to the large interest in wireless devices. Many large companies produce several million batteries per month due to requirement. The energy capacity has improved and it is major development issue, for this consumer products are probably safe and considered equally important today. To reduce fuel consumption and gas emissions, battery technological development has to be improved for the newly hybrid based electric vehicles. To develop the battery the major task is both for academic research and industry.

3.3.1 Modeling of battery The battery is modeled as a nonlinear voltage source and its output voltage depends on current and state of charge (SOC) of battery, which is a nonlinear function of the current and time. Terminal voltage and state of charge parameters represent the state of battery. It can be written as: ..... (3.2) .....