solar power by k r.thanki

Solar Power

Sub.: ENVIRONMENT CONSERVATION and HAZARD MANAGEMENT (3300003)

UNIT -IV

Prepared By:

K.R.THANKI (BE Civil)

LECTURER CIVIL ENGINEERING DEPARTMENTGOVERNMENT POLY TECHNIC ,

JUNAGADH,GUJARAT-INDIA.

The Sun: The Sun is a G2 type star, one of the hundred billion stars of this type in our galaxy (one of the hundred billion galaxies in the known universe).

Diameter: 1,390,000 km (the Earth: 12,742 km or 100 times smaller)

Mass: 1.1989 x 1030 kg (333,000 times the mass of the Earth)

The Sun:

The Sun: The Sun contains 99.8% of the total mass of the Solar System (Jupiter contains nearly all the rest).

• Sun‘s energy output is produced in the core of the sun by nuclear reactions (fusion of four hydrogen (H) atoms into one helium (He) atom).

• Sun is about 4.5 billion years old. Since its birth it has used up about half of the hydrogen in its core.

The Sun: • Sufficient fuel remains for the Sun to continue radiating "peacefully“ for another 5 billion years (although its luminosity will approximately double over that period), but eventually it will run out of hydrogen fuel.

Chemical composition:Hydrogen 92.1%Helium 7.8%Other elements: 0.1%

The Sun: The Sun's energy output is 3.84 * 1017 Gigawatts:(a typical nuclear power plant produces 1 Gigawatt)•The outer 500 km of the sun (“photosphere“) emits most of radiation received on Earth.•Temperature: 5800 K (at the surface) 15,600,000 K (at the core).

The Sun:

Solar radiation

Intensity of solar irradiance decreases with distance according toInverse square law.

• -is any physical law stating that a specified physical quantity or intensity is inversely proportional to the square of the distance from the source of that physical quantity.

• In equation form: Where I is the intensity of the radiation and d is the distance.

Inverse Square Law

Solar radiation

Inverse square law is applied to:

Gravitational strength with distance.

Electrostatic force with distance.

Light intensity from a point object.

Sound intensity from a point source.

Nuclear radiation from a point source.

Radiation emitted by the Sun and the Earth

Electromagnetic Spectrum

ULTRA-

VIOLET

RADIATION

FG Figure 7-2

ULTRA-

VIOLET

RADIATION

INFRARED RADIATION

Sun Earth relationships

Earth‘s orbit around the Sun:

Earth's orbit is an ellipse and the sun is located in one of its focal points.

=> Sun Earth-distance are varies during the course of the year

Sun Earth relationships

Solar radiation

☼ Approximately 30% energy is reflected back to space.

☼ Earth's land surface, oceans and atmosphere absorb solar radiation, and this raises their temperature.

☼ The total solar energy absorbed by Earth's atmosphere, oceans and land masses in one hour is more than the world used in one year.

Solar radiation

☼ The solar rays have various wave lengths ranging from o µm to 4 µm.

☼ But 90% solar radiations which are in the visible spectrum have wave lengths between 0.38 µm to 4 µm.

☼ A Spectrum is a range of wavelength for particular group of radiations.

Solar radiation

Solar radiationThe effects of atmosphere on solar radiations:

Absorption:

The short wave ultra violate rays are absorbed by the ozone gas and long waves infrared rays are absorbed by carbon dioxide and water vapor present in the atmosphere.

Absorption process reduces intensity of radiation.

Solar radiation

Absorption

Reflection:

The atmosphere contains suspended particles; When radiation fall on these particles ,they are reflected back into atmosphere due to shining .

Reflection process reduces intensity of radiation.

Solar radiation

Scattering:

Solar radiation strikes on the suspended particles in the atmosphere, they get diffused.Scattered radiations reach the earth surface as diffused radiation. This effect also reduces the intensity of radiations reaching on the surface of Earth.

Solar radiation

Scattering

Refraction:

When solar radiation travel through the thickness of earth’s atmosphere, their directions and the angle of incidence get changed.

Solar radiation

Refraction

Types of Solar Radiation:Atmospheric Effects: Solar radiation is absorbed, scattered and reflected by components of the atmosphere.

• The amount of radiation reaching the earth is less than what entered the top of the atmosphere.

Types of Solar Radiation:

Beam Radiation

Diffuse Radiation

Total Radiation

Types of Solar Radiation:The solar radiations which are received on earth surface directly without having change its direction are called Beam or Direct radiation.

It is also known as “Sun shine.”

These radiations are very intense and have harmful effect if they fall straight into our eyes.

Beam Radiation

Types of Solar Radiation:When solar rays pass through clouds, they get diffused because the cloud contains suspended particles, water vapor and gases.

The radiations are scattered, reflected and refracted due to which its energy is very much reduced.

Diffuse Radiation

Types of Solar Radiation:They are also called as global radiations.

Total solar energy falling on unit area on any part of the earth is called total radiation.

It is measured in watts per sq. meter.

It is the sum of beam radiation and diffused radiations.

Total Radiation

Types of Solar Radiation:

Principles of measurement of Solar Radiation:

Principle of Thermo Couple

Photovoltaic Principle

Principle of solar concentration

When metallic strips of dissimilar metals are joined to gather at one end, they form thermo couple and other end of the thermo couple produces E.M.F. in millivolt when the junction is heated.

E.M.F. produces at end is in proportional to the temperatures.

Thermo couple can be used to measure intensity of radiation by heating them with solar radiations and finding the voltage produced by heating.

Photo Voltaic or Silicon cell can be used to measure the intensity of solar radiations.

When solar rays fall on silicon cell, electricity is produced.

Hence radiation measuring instruments can be calibrated directly with watts per sq. meters to known the value of solar constant.

Photovoltaic Principle

Photovoltaic PrinciplePrinciple of solar concentration

Solar ray can be concentrated by convex lens. The concentrated solar rays when fall on piece of paper, it starts burning.

How much time it take to burn the paper can be measured by time recorder.

Time to burn the piece of paper is inversely proportional to heat energy.

Solar radiation measurement Instruments:

Pyranometer

Pyrheliometer

Sun-shine Recorder

It measures total and diffused radiation.

It can measure diffused radiation when shading ring is used to prevent beam radiation when shading ring is used to prevent beam radiation falling on it; is called as Eppley Pyranometer.

Pyrheliometer is used to measure direct beam radiation.

It is working on simillar principle as pyranometer.

The sun-shine Recorder is used to measure the duration of the day when there was bright sun shine giving beam radiation.

It is measured continuously through out the day on the card paper kept in groves provided on the instrument.

Solar Photo Voltaic System

Photovoltaic (PV) systems convert sunlight directly into DC power, and are potentially one of the most useful renewable energy technologies.

Solar Photo Voltaic System

Semiconductors:

The semiconductors are the type of materials which are neither good conductors nor bad conductors of electricity.

The process of adding controlled impurities to a semiconductor is known as doping they can be doped with impurities like Boron, Arsenide copper and Cadmium etc..

P-N Junction:

A P-N junction is a junction formed by joining P-type and N-type semiconductors together in very close contact.

P- type materials are doped with trivalent impurities while N type materials are doped with penta valent impurities so that they can be donors and acceptors for free electrons.

P-N Junction:

What is a solar cell ?• A solar cell (also called photovoltaic

cell) is a electrical device that converts the energy of light directly into electricity by the photovoltaic effect.

Solar Cell(Photovoltaics)

Solar Cell (PV)

Light Electricity

Nonrenewable Enargy

재생에너지원 (Renewable Energy)

일회용에너지원 (Nonrenewable Energy)

Renewable

What is a Solar Cell?

• A structure that converts solar energy directly to DC electric energy.– It supplies a voltage and a current to a resistive load

(light, battery, motor).– Power = Current x Voltage=Current2 x R= Voltage2/R

• It is like a battery because it supplies DC power.• It is not like a battery because the voltage supplied by the

cell changes with changes in the resistance of the load.

Solar cell

Basic Physics of Solar Cells

• Silicon (Si) is from group 4 of the period table. When many Si atoms are in close proximity, the energy states form bands of forbidden energy states.

• One of these bands is called the band gap(Eg) and the absorption of light in Si is a strong function of Eg.

• The Sun daily provides about 10 000 times more energy to the Earth than we consume

• Photovoltaic technology directly converts solar energy into electricity

• No moving parts – no noise – no emissions – long lifetime

• Large industrial potential - cost reductions needed• Feedstock for PV industry is silicon - the second

most abundant element in the crust of the Earth

The Sun as Energy Source

Polysilicon Wafer Solar Cell Solar Module

Chemical Process

(purification)

CastingCutting

Surface Treatment

Assembly

Systems

InstallationOperation

The PV Value Chain (multi-crystalline)

How does solar energy work?

Solar Electric or Photovoltaic Systems convert some of the energy in sunlight directly into electricity. Photovoltaic (PV) cells are made primarily of silicon, the second most abundant element in the earth's crust, and the same semiconductor material used for computers. When the silicon is combined with one or more other materials, it exhibits unique electrical properties in the presence of sunlight. Electrons are excited by the light and move through the silicon. This is known as the photovoltaic effect and results in direct current (DC) electricity. PV modules have no moving parts, are virtually maintenance-free, and have a working life of 20 - 30 years.

Silicon Solar cell

Groups of solar cells can be packaged into modules, panels and arrays to provide useful

output voltages and currents to provide a specific power output

- An individual PV cell typically produces between 1 and 2 watts

Solar Cell, Module, Array

Basic structure of a SOLAR CELL

A = Glass cover B = Anti reflective coating C = Contact grid

D = N-type Silicon E = P-type silicon F = Back contact

n-type semiconductor

p-type semiconductor

+ + + + + + + + + + + + + + + - - - - - - - - - - - - - - - - - -

Operation of a solar cells

Depletion Zone

When light hits the cell

• When light, in the form of photons, hits our solar cell, its energy frees electron-hole pairs.

• Each photon with enough energy will normally free exactly one electron, and result in a free hole as well. If this happens close enough to the electric field, the field will send the electron to the N side and the hole to the P side. This causes further disruption of electrical neutrality, and if we provide an external current path, electrons will flow through the path to their original side (the P side) to unite with holes. The electron flow provides the current, and the cell's electric field causes a voltage.

Solar cell - converts light energy to electricity

Light energy

Electrical energy (carried through wires)

Solar Cells are Converters of Energy…

Solar cells can only absorb specific wavelengths of

light.

A certain wavelength of lights gets absorbed

depends on its energy Light with energy greater

than the band gap energy of Si is absorbed

Types of Solar Cells :

Silicon Solar Cell

Cadmium sulfide- Copper Sulfied cell

Gallium Arsenide Cell

Sohottky Junction

Metal Insulator Semiconductor

Types of Solar Cells :Solar cells are electrically connected “in series” to achieve higher voltages

Source: Photon Special 2004

Types of Solar Cells :

Typical Structure:

• Glass• Transparent lamination foil

(Ethylen Vinyl Acetat: EVA)• Solar cells, electrically connected• back side protection

(Teflon foil or glass)

Packaging of solar cells into a solar “module” protects against destructive environment

Source: Photon Special 2004

Types of Solar Cells :Module (Solar Panel):

Siemens SM55 monocrystalline Silicon

Source: Siemens Solar GmbH, Germany

SOLAR COLLECTORS

• Expose a dark surface

to solar radiation so

that the radiation is

absorbed. This heat is

then transferred to

thermal/heat storage

tank and utilized.

TYPES :-1. FLAT PLATE

COLLECTORS :- • Low temperature

application, <1000c.

2. FOCUSING PLATE COLLECTOR :-

• For high temperature, 1000c - 3000c.

FLATE PLATE COLLECTOR

• Consist of casing, absorber plate, transparent glass covers, insulating material and fluid passage tubes.

FOCUSING PLATE COLLECTOR

• Coming RADIATION on concentrator is diverted to absorber tube, which is covered with glass tube to avoid reradiation loss.

Solar modules are designed to withstand the toughest environmental conditions and manufactured in compliance with the most stringent quality standards. The Solar modules are covered by a 10 year limited warranty on power output. .

The solar module contains 36 mono or poly crystalline silicon solar cells connected in series. All cells are electrically matched to assure the maximum power output possible. One solar module can charge a 12 volt battery using a charge controller. System voltages of 24 volt and higher can be obtained by connecting modules in series. Higher currents can be obtained by connecting modules in parallel.

• decrease the area of solar cell material being used in a system

Concentrator collectors

• Flat-plate collectors typically use large numbers or areas of cells that are mounted on a rigid, flat surface.

substrate ; metal, glass, plastic

• They are simpler to design and fabricate.

• They do not require special optics, specially designed cells, or mounting structures that must track the sun precisely. plus, flat-plate collectors can use all the sunlight

Flat-Plate Systems

Definitions Solar cellThe solar cell is the basic unit which makes electricity from

sunlight

Solar panel (or: solar module)The solar panel contains a number of cells and protects them

Solar arrayThe solar array is the installaton of one (or many) solar

modules

Solar system (or: solar generator)The solar system includes inverters or batteries (if needed) etc.

Cost breakdown for a solar system based on Si-wafer PV cells, status 2006

Solar cell production 1999 to 2010

Shares per region for 2010 (2009)

Solar cell: absorber crystalline silicon

200 μm

CIS Thin Film PV cell

SEM picture of cross section of PV cellPicture: ZSW

TCO/ZnO

Absorber/CIGS

Back contact/Mo

Substrate/glass

Buffer/CdS

Flexible and light weight Thin Film Modules

For the power market: Low cost PV-modules through “roll to roll” productionPicture: Solar Integrated, www.solarintegrated.com

Portable power source (mobile communications), integration into flexible structures (tent roofs, air ships)

IPC Solar, www.IPC-Solar.com

Lidl, Vars, southern France, 1 MW,Unisolar Modules, a-Si, flexible membranes, on roof

Why Concentration Technologies?The basic idea:

Use cheap optics for collection of the sunlight and reduce the expensive semiconductor material

Reduce cost of PV-generated kWh

solar radiation

lens F0

solar cell Fc

heat transport 04/0

Cost break down for a solar system based on Si-wafer PV cells, status 2006

Uses for Solar Energy

Solar Home Systems

Water Pumping

Telecom

Main Application Areas – Off-grid

Residential HomeSystems (2-8 kW) PV Power Plants

( > 100 kW)

Commercial BuildingSystems (50 kW)

Main Application AreasGrid Connected

• Solar energy will become the most important and cost-efficient energy source in the future.

• The present lack of silicon feedstock is promoting a rapid development of next generation technology.

• Immediate actions are taken to cut thinner wafers and increase cell efficiencies for crystalline silicon.

• New thin film technologies are being developed.• Stronger influence from semiconductor industry will

accelerate the development of better technologies• Nanosilicon and other third generation technologies may

offer a long-term solution for the future solar energy technology.

Conclusions

THANK YOU………FOR ANY OTHER INFORMATION PLEASE CONTECT ME TO

Email : thankikrunal@yahoo.co.in

solar power by k r.thanki

solar radiations

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