a presentation on solar photovoltaic cell

A

Presentation

on

SOLAR PHOTOVOLTAIC CELl

www.engineersportal.in

Solid state device that converts incident solar energy directly into electrical energy

Efficiencies from a few percent up to 20-30%

No moving parts No noise Lifetimes of 30-40 years or more


The PHOTOVOLTAIC EFFECT refers to photons of light exciting electrons into a higher state of energy, allowing them to act as charge carriers for an electric current

The term “Photovoltaics” comes from the Greek, meaning light, volts, and electrical


1839 - French physicist A. E. Becquerel first recognized the photovoltaic effect

Photo+voltaic = convert light to electricity

1954 - Bell Laboratories, experimenting with semiconductors, accidentally found that silicon doped with certain impurities was very sensitive to light.

Resulted in the production of the first practical solar cells with a sunlight energy conversion efficiency of around 6%.

http://en.wikipedia.org/wiki/Solar_cell www.engineersportal.in

The junction of dissimilar materials (n and p type silicon) creates a voltage

Energy from sunlight knocks out electrons, creating a electron and a hole in the junction

Connecting both sides to an external circuit causes current to flow

In essence, sunlight on a solar cell creates a small battery with voltages typically 0.5 v. DC


A semiconductor is a material which has electrical conductivity between that of a conductor such as copper and an insulator such as glass.

Silicon(Si) ,Germenium(Ge)


Intrinsic Semiconductor

Extrinsic Semiconducter

P - Type N- Type


Intrinsic Semiconductor Also called an undoped semiconductor

or i-type semiconductor, is a pure semiconductor without any significant dopant species present.

Number of excited Electrons Holes are equal


In semiconductor production, doping intentionally introduces impurities into an extremely pure semiconductor for the purpose of modulating its electrical properties

Based on impurties 2 types of semiconductor are produced

n- Type

p- type


The pure silicon is doped with a group 5 element such as phosphorus, antimony or arsenic.


The pure silicon is doped with a group 3 element such as boron, aluminium or indium.


On the basis of Active Material

Monocrystalline Solar cellPolycrystalline Solar cellAmorphous Silicon Solar cellGallium Arsenide CellCopper Indium Diselenide (CIS) cellCadmium Telluride Cell(CdTe)Organic Photovoltaic Cell


Silica (SiO2) is the compound used to make the cells. It is first refined and purified, then melted down and re-solidified so that it can be arranged in perfect wafers for electric conduction. These wafers are very thin.

Many of these types of cells are joined together to make arrays, the size of each array is dependant upon the amount of sunlight in a given area.


Mono crystalline Solar Cell

EfficiencyCurrently, SunPower (USA) manufacturers the most efficient monocrystalline solar panels - with an efficiency of 22.5 percent


MGS: Raw material is Quartzite (SiO2, sand), then refined to Metallurgical Grade Silicon (MGS)

with coal / coke and SiO2 @ ~ 2000°C 2 C (solid) + 2 SiO2(solid) Si (liquid) + 2 CO Significant power needed: ~ 13 kWh/kg End result: 98% Silicon

Electronic Grade Silicon (EGS) MGS + HCl (gas) SiH4 (silane) SiCl4 (silicon

tetracloride) SiHCl3(trichlorosilane)


High-purity, semiconductor grade silicon is melted in a crucible

Dopant impurity atoms such as boron or phosphorus can be added to the molten silicon in precise amounts to dope the silicon, thus changing it into p-type or n-type silicon, with different electronic properties

A precisely oriented rod-mounted seed crystal is dipped into the molten silicon. The seed crystal's rod is slowly pulled upwards and rotated simultaneously


By precisely controlling the temperature gradients, rate of pulling and speed of rotation, it is possible to extract a large, single-crystal, cylindrical ingot from the melt

Occurrence of unwanted instabilities in the melt can be avoided by investigating and visualizing the temperature and velocity fields during the crystal growth process


Durable/Longevity: Several of the early modules installed in the 1970's are still producing electricity today

Drop in Efficiency is just 0.5% per year More efficient than poly crystalline and

thin film solar cell Lower Installation Costs Embodied Energy: less embodied energy

reqired for per watt of energy More Electricity for per square area


Initial CostFragile: it can be damaged by strong wind


Polycrystalline (sometimes also called multicrystalline) solar panels are the most common because they are often the least expensive

Polycrystalline silicon is composed of many smaller silicon crystal fused together

A polycrystalline silicon rod made by the Siemens process


The molten silicon is poured into a cast instead of being made into a single crystal

In the cast process, silicon pieces are melted in a ceramic crucible and then formed in a graphite mold to form an ingot.

Although molding and using multiple silicon cells requires less silicon and reduces the manufacturing costs, it also reduces the efficiency of the solar panels.


1. P-n junction cells For a p - n junction cell, a polycrystalline

silicon film is deposited by chemical vapor deposition on substances like glass, silicon and metal


2 Metal insulator Semiconductor (MIS) Cells

These are made by inserting a thin insulating layer of SiO2 between metal and semiconductor


A window semiconductor is used over an active semiconductor

It has high transmittance for solar rdiation and high electricalconductivity

Acts as a antireflection coating


The typical monocrystalline solar cell is a dark black colour, and the corners of cells are usually missing as a result of the production process and the physical nature of monocrystalline silicon and Polycrystalline is of light or dark blue colour


Monocrystalline cell is more efficient than polycrystalline polycrystalline panels have an efficiency that is about 70% to 80% of a comparable monocrystalline solar panel.

Polycrystalline cell are less expensive than \monocrystalline


The term "Thin film solar panels" refers to the fact that these types of solar panels use a much thinner level of photovoltaic material then mono-crystalline or multi-crystalline solar panels

Thin film solar cells consist of layers of active materials about 10 nm thick compared with 200- to 300-nm layers for crystalline-silicon cells.

A-Si has been used as a photovoltaic solar cell material for devices which require very little power, such as pocket calculators


The thin film solar panel is a new type of solar technology made by coating a metal or glass surface with light absorbing amorphous silicon alloy layers


A transparent conducting oxide layer (such as tin oxide) forms the front electrical contact of the cell, and a metal layer forms the rear contact.

The primary objective of manufacturers of these solar panels is to reduce the overall price per watt to make solar competitive

While these thin module prices are much lower in price, they also have a lower module efficiency (roughly 1/2 of monocrystalline solar panels,


The most advanced of thin film technologies

Operating efficiency ~6%

Makes up about 13% of PV market


Versatility: Thin film can be applied to almost all types of surfaces - such as metal, plastic and even paper

Flexibility: While crystal silicon solar panels are rigid and therefore fragile, "thin film" materials can be deposited on flexible substrate materials

Good Performance in Indirect Light One benefit of thin film solar panels that other

types can’t offer is that they don’t suffer a decrease in output when temperatures go up


Efficiency: This is the reason why thin film solar panels haven’t replaced older types yet

Longevity: These cell are not considered as durable as crystalline cell

Scarcity of Raw Tellurium Toxicity Concerns: Both Cadmium

Telluride (larger amounts) and CIGS (smaller amounts) use Cadmium, which is classified as one of the 6th most toxic substance


1. Semiconductor: monocrystalline, Polycrystalline,Thin film Solar cell

2. Electrical Contacts: Electrical contacts are essential to PV cells because they bridge the connection between the semiconductor material and the external electrical load, such as a light bulb.

Coating on both the side is done. Front side is more complicated.


To make top-surface grids, metallic vapors are deposited on a cell through a mask or painted on via a screen-printing method.

Metals such as palladium/silver, nickel, or copper are used


3. Anti-reflection coatings: The top surface with a thin layer of silicon monoxide (SiO). A single layer reduces surface reflection to about 10%, and a second layer can lower the reflection to less than 4%.

titanium dioxide silicon oxide,

4. Glass Cover: These are used to protect from atmoshpere

5. Encapsulating the cell: in the last finished solar cells are then encapsulated


sealed into silicon rubber or ethylene vinyl acetate.

The encapsulated solar cells are then placed into an aluminum frame that has a mylar or tedlar back sheet and a glass or plastic cover

6.Connectors: Finally, the module is fitted with connectors and cables, so it can be wired.


Typical output of a module (~30 cells) is ≈ 15 V, with 1.5 A current


A solar cell is the basic building block of a PV system.

A typical cell produces .5 to 1V of electricity.

Solar cells are combined together to become modules or if large enough, known as an array.

A structure to point the modules towards the sun is necessary, as well as electricity converters, which convert DC power to AC.

All of these components allow the system to power a water pump, appliances, commercial sites, or even a whole community.


While a major component and cost of a PV system is the array, several other components are typically needed. These include:

The inverter – DC to AC electricity DC and AC safety switches Batteries (optional depending on design) Monitor – (optional but a good idea) Ordinary electrical meters work as net

meters


Battery ChargingDomestic lightingStreet LightingWater PumpingPower Generation Schemes


The PV module charge the battery through an electronic controller

It automatically charge the battery during sunshine and simultaneously supply the power to appliances

During non sun shine it also supply power automatically

Charge controller indicates the charging In case voltage is below a preset level loads

automatically gets cut off


In case of overcharge, PV cell get disconnected from battery

Short circuit is also provided using fuses Reverse polarity and indication is also

provided


A charge controller, charge regulator or battery regulator limits the rate at which current is added to or drawn from electric batteries

It prevents overcharging and may prevent against overvoltage which can reduce battery performance or lifespan, and may pose a safety risk Tracking technology to manufacture our controllers


Manufactured by Max Power Point Tracking technology


Street Light Emergency Backup Rural Power Solar Pump Road Flasher Solar Lantern Solar Power Pack House Office Manufacturing Plant


The Power Solar Home Lighting Systems is a prepackaged control unit designed for rural home electrification.

just adds batteries and modules for a complete solar home system that replaces dry cell batteries, kerosene and candles with safe, dependable solar energy

These systems supply electricity for lighting, entertainment and information to homes that are not connected to utility power grids


Solar street lights are powered by photovoltaic cells mounted on the lighting structure

The photovoltaic panels charge a rechargeable battery, which powers a fluorescent or LED lamp during the night.

May be automatic or manually


Standalone solar street lights:Standalone solar street lights have

photovoltaic panels mounted on the structure. Each street light has its own photovoltaic panels and is independent of the other lamps

Centrally operated solar street lightsThe photovoltaic panels for a group of street

lights are mounted separately and All the street lights in a particular group are connected to this central power source.


Our stand alone solar powered lighting offers the following benefits:

eliminates expensive mains cable installation costs eliminates any associated electricity bills increases public safety and aids in providing a safe

working environment in areas where mains power is difficult to access

fully automatic operation high quality construction and components designed for easy servicing and maintenance where

required


Solar pumping systems work anywhere the sun shines.


Solar panels mounted on the top of the pole convert sunlight into electricity which is used to charge a battery.

A solar controller/regulator ensures that the battery is charged in the most effective manner and not overcharged. The controller senses when the sun goes down and turns on the light.

The controller can be programmed to run the light all night, or for the required time duration. The controller also protects the battery from over discharge.


During the hot months, when water requirements are highest, a solar pump will provide a reliable water source for a farm

small pump only running when the sun shines, plus water storage, can often provide all that is requiremed for water supply

1. Water for drinking & cooking 2. Water for livestock 3. Water for crop irrigation


Stand alone PV Power generation Water pumping Domestic Lighting Street Lighting

Grid interactive Power generation Large Scale power production Grid is used to Distribute Power


These are electrical power systems which are independent of the utility grid


The availability of grid-interactive PV systems means that energy consumers can tie to the grid when it benefits them and disengage when it does not


On grid means a house remains connected

to the state electricity grid. PV module are

connected to utility grid system

During day time PV supply power to grid

system

During night time or in emergency grid

supply power back to the load

Thus need for a battery is removed


The power source of the sun is absolutely free

The production of solar energy produces no pollution. The first and foremost advantage of solar energy is that it does not emit any GHGs

Most systems do not require any maintenance during their lifespan, which means you never have to put money into them

Most systems have a life span of 30 to 40 years

Most systems carry a full warranty for 20 to 30 years or more


Solar energy offers decentralization in most (sunny) locations, meaning self-reliant societies

The ability to produce electricity off the grid is a major advantage of solar energy for people who live in isolated and rural areas

A particularly relevant and advantageous feature of solar energy production is that it creates jobs.

Solar jobs come in many forms, from manufacturing, installing, monitoring and maintaining solar panels, to research and design, development, cultural integration, and policy jobs


One of the biggest advantages of solar energy is the ability to avoid the politics and price volatility that is increasingly characterizing fossil fuel markets

Because solar doesn’t rely on constantly mining raw materials, it doesn’t result in the destruction of forests and eco-systems that occurs with most fossil fuel operations


The primary disadvantage to solar energy is the initial cost. Solar energy technologies still remain a costly alternative to the use of readily available fossil fuel technologies

A very common criticism is that solar energy production is relatively inefficient.

solar energy installation requires a large area for the system to be efficient in providing a source of electricity. This may be a disadvantage in areas where space is short, or expensive (such as inner cities)


Solar energy is only useful when the sun is shining. During the night, your expensive solar equipment will be useless, however the use of solar battery chargers can help to reduce the effects of this disadvantage

The location of solar panels can affect performance, due to possible obstructions from the surrounding buildings or landscape

Pollution can be a disadvantage to solar panels, as pollution can degrade the efficiency of photovoltaic cells

Solar electricity storage technology has not reached its potential yet


Energy Payback Time: Energy Payback Time: EPBTEPBT is the time necessary for a is the time necessary for a

photovoltaic panel to generate the energy photovoltaic panel to generate the energy equivalent to that used to produce it. equivalent to that used to produce it.

A ratio of total energy used to A ratio of total energy used to manufacture a PV module to average daily manufacture a PV module to average daily energy of a PV systemenergy of a PV system..

At present the Energy payback time for PV At present the Energy payback time for PV systems is in the rangesystems is in the range

8 to 11 years8 to 11 years, compared with typical , compared with typical system lifetimes of around 30 years. About system lifetimes of around 30 years. About 60% of the embodied energy is due to the 60% of the embodied energy is due to the silicon wafers.silicon wafers.


There has been almost six fold decline in price per peak watt of PV module from 1980 to year 2000

Solar PV Costs 1980-2000


If your load is 10 kw-hr per day, and you want to battery to provide 2.5 days of storage, then it needs to store 25 kw-hr of extractable electrical energy. Since deep cycle batteries can be discharged up to 80% of capacity without harm

you need a baettry with a storage of 25/0.8 = 31.25 kw-hr. A typical battery at 12 volts and 200 amp-hour capacity stores 2.4 kw-hr of electrical energy


The relationship between energy in kw-hr and battery capacity is

E(kw-hr) =capacity(amp-hr) x voltage/1000 E = 200 amp-hr x 12 volts/1000= 2.4 kw-hr So for 31.25 kw-hr of storage we need 31.25 kw-hr/2.4 kw-hr/battery = 13

batteries


A PV system can be sized to provide part or all of your electrical consumption. If you wanted to produce 3600 kw-hr a year at a site that had an average of 4.1 peak sun hours per day,

PV Size in KWp = 3600 kw-hr 4.1 kw-hr/day x 365 days/yr x 0.9 x0.98

= 2.7 KWpNote: the 0.9 is the inverter efficiency and

the 0.98 represents the loss in the wiring.


The actual area that you need depends on the efficiency of the solar cells that you use. Typical polycrystalline silicon with around 12% efficiency will require about 100 ft2 of area to provide a peak kilowatt. Less efficient amorphous silicon may need 200 ft2 to provide the same output. Modules are sold in terms of peak wattage and their areas are given so you can easily determine the total roof area that is needed for a given size array.


Assume it is a 100 Wp module and its area is 0.8 m2. Remember that the peak power rating is based on an intensity of 1000 watts/m2. So the maximum output with 100% efficiency is P = I x A = 1000 w/m2 x 0.8 m2 = 800 watts

The actual efficiency = Pactual peak/Pmaximum peak

= 100 watts/800 watts = 0.125 or 12.5%


Solar Electric Energy demand has grown consistently by 20-25% per annum over the past 20 years (from 26 MW back in 1980 to 127MW in 1997)

At present solar photovoltaic is not the prime contributor to the electrical capacities but the pace at which advancement of PV technology and with the rising demand of cleaner source of energy it is expected by 2030 solar PV will have a leading role in electricity generation

Research is underway for new fabrication techniques, like those used for microchips. Alternative materials like cadmium sulfide and gallium arsenide ,thin-film cells are in development


THANK YOU


a presentation on solar photovoltaic cell

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