Solar energy and PV Cells

Supervisor: Dr. Shah AlamMentor: Dr.M.J.Siddiqui

Presented By: Surbhi Agarwal

ContentsBasic Concept of Solar energy

Physics of Photovoltaic cellsPV modules

Emerging Technologies

Environmental Aspects

Indian Scenario

Application of solar panel

Disadvantages of solar cells

What is solar energy?radiant energy emitted by the sun.

The Sun daily provides about 10,000 times more energy to the Earth than we consume.The earth receives 174 petawatts [1015 watts] of solar radiations from the sun.

The total energy absorbed by earth’s atmosphere, oceans, land mass is 3,850,000 exajoules [1018 joules] per year.

The energy reaching earth’s atmosphere consists of about 8% UV radiation, 46% visible light, 46% infrared radiations.

Why Solar Energy ?Solar energy is the most readily available source of energy.

It is free.

It is also the most important of the non-conventional sources of energy because it is non-polluting.

It is a renewable source of energy.

(Renewable Energy) (Nonrenewable Energy)

What is a Photovoltaic Cell?

also called solar cell, is an electrical device that converts the energy of light directly into electricity by the photovoltaic effect.

Solar Cell (PV)

Light Electricity

Photovoltaic effectSunlight is composed of photons, or particles of solar energy that contain various amounts of energy corresponding to the different wavelengths of the solar spectrum.

The electrons present in the valence band absorb energy and, being excited, jump to the conduction band and become free.These highly excited electrons are accelerated into a different material by a built-in potential.

This generates an electromotive force, and thus some of the light energy is converted into electric energy.

History of Solar Cells

Discovery of Photovoltaic effect by French physicist , Alexandre-Edmond Becquerel.

1839 :

1883 : A description of the first solar cells made from selenium wafer were made by Charles Fritts and operated at 1% effeciency . Charles Fritts constructed what was probably the first true solar cell. He coated a semiconductor material (selenium) with an extremely thin layer of gold.

1894 :

A cadmium sulphide p-n junction was produced with an efficiency of 6% Audobert and Stora discover the photovoltaic effect in cadmium sulfide (CdS).

The The Fraunhofer Institute for Solar Energy achieve a 44.7% efficiency in solar cell technology.

1932 :

1954 :The University of South Wales breaks the 20% efficiency barrier for silicon solar cells under one sun conditions.

1985 :

2013 :

Basic structure of a SOLAR CELL

When sun light falls on silicon metal cell, the photon energy allows the electrons from the P-layer to move to the N-layer, creating an electric potential difference on the semiconductor borders.

If these borders are connected to a load by conductive wires, there will be a flow of electric current, getting back the electrons to the P-layer and starting the process again.

A photovoltaic cell generally has low current and voltage levels, of about 3 A and 0.7 V, respectively.

Operation of a solar cells

For this , many cells are connected in series and/or parallel to obtain the expected current and voltage levels and this set of cells is mounted on an appropriate structure to create a photovoltaic module.

Assemblies of cells are used to make solar modules , also known as solar panels and these panels are combined to form arrays.

PV modules

Applications of Solar panel

“Nellis solar power plant” contains 70,000 solar panels that generate 25 gigawatt-

hours

“solar one”, California 1,800

sun-tracking mirrors reflect

heat to a central collector

a solar farm in the Philippines…

Major Solar Plants

Types of PV cells

Silicon Crystalline Cells

Thin Film Cells made by using crystalline silicon solar cells,developed from the microelectronics technology industry.

made by depositing one or more thin layers (thin film) of photovoltaic material on a substrate.

Mono Crystalline PV Cells

Multi Crystalline PV Cells

Amorphous Silicon PV Cells

Poly Crystalline PV Cells(Non-Silicon based)

Silicon Crystalline TechnologyCurrently makes up 86% of PV market Very stable with module efficiencies 10-16%

Mono crystalline PV CellsMade using saw-cut from single cylindrical crystal of Si

Operating efficiency up to 15%

Multi Crystalline PV CellsCaste from ingot of melted and recrystallised silicon

Cell efficiency ~12%Accounts for 90% of crystalline Si market

Thin Film Technology Silicon deposited in a continuous on a base material such as glass, metal or polymers.

Thin-film crystalline solar cell consists of layers about 10μm thick compared with 200-300μm layers for crystalline silicon cells.

PROS• Low cost substrate and fabrication process.

CONS• Not very stable .

Amorphous Silicon PV Cells The most advanced of thin film technologies . Operating efficiency ~6% . Makes up about 13% of PV market .

PROS• Mature manufacturing technologies available .

CONS• Initial 20-40% loss in efficiency .

Poly Crystalline PV Cells( Non – Silicon Based Technology )

PROS 16% laboratory efficiency 6-9% module efficiency

CONS Immature manufacturing process

Unlike most other II/IV material CdTe exhibits direct band gap of 1.4eV and high absorption coefficient

Emerging Technologies

Electrochemical solar cells have their active component in liquid phase.

Dye sensitizers are used to absorb light and create electron-hole pairs in nanocrystalline titanium dioxide semiconductor layer.

Cell efficiency ~ 7%

‘ Discovering new realms of Photovoltaic Technologies ‘

Electrochemical solar cells

Ultra Thin Wafer Solar Cells

Thickness ~ 45μm

Cell Efficiency as high as 20.3%

Anti- Reflection CoatingLow cost deposition techniques use a metalorganic titanium or tantanum mixed with suitable organic additives

Emerging Technologies ‘ Discovering new realms of Photovoltaic Technologies ‘

Environmental Aspects

Exhaustion of raw materials CO2 emission during fabrication process Disposal problems of hazardous semiconductor material

In spite of all these environmental concerns, Solar Photovoltaic is one of the cleanest form

of energy

In terms of overall installed PV capacity, India comes fourth after Japan, Germany and U.S. (With Installed capacity of 110 MW). India today is the second largest manufacturer in the world of PV panels. The Delhi Government has decided to make use of solar power compulsory for lighting up hoardings and for street lighting . Solar power generation is merely concentrated in three states. Gujarat Rajasthan Maharashtra

Where India now and its total installed capacity?

Solar panels are expensive. Solar power is inefficient in cloudy areas. A solar energy installation requires a large area for the system to be efficient in

providing a source of electricity. Solar power maintenance is a problem especially to those who doesn’t know the

proper techniques. Disposal is difficult for the batteries and solar panels when they have broken down

because they contain toxic chemicals like lead, sulfuric acid & cadmium telluride.

Disadvantages of solar cells

Solarbuzz European and US All Solar Module Retail Price Index

Conclusions• Solar energy is the energy emitted by the sun.• It is the most abundant and renewable form of energy.• Photovoltaic cells convert light energy into electrical energy.• Assembly of PV cells make solar panels.• Solar panels finds its applications in many fields such as domestic

lighting, solar vehicles etc.• Cost and area are big disadvantage of solar cells.

[1] V. Smil, “Energy at the crossroads”, OECD Global Science Forum, 2006. [2] V. Smil, “General Energetics Energy in the Biosphere and Civilization” , xiii + 369 pp (1991).[3] "Climate and Earth’s Energy Budget". NASA Earth Observatory, (2009).

[4] Donald A. Neaman, “Semiconductor Physics and devices”, fourth edition, Tata McGraw Hill Pvt. Ltd., pg:- 177-197.

[5] B.H.Khan, “Non –conventional energy resources”, second edition , Tata McGraw Hill Pvt. Ltd., pg:-88-192

[6] Mohit Kr. Srivastava, Sharad Kr. Gupta, Ashish Gupta, “Environmental Aspects of Solar Cell Modules”.

References:

ThankYou!!!