Photovoltaic Energy

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Photovoltaic Energy Paolo Abagar, Mario Miguel Celdran, Arjan Delos Santos, Keno Hibaya, Kevin Richard Miraflores, Lovely Jane Vallinas EE 147 Energy Conversion EECE Department Mindanao State University Iligan Institute of Technology Iligan City, Philippines I. INTRODUCT ION The term "photovoltaic" has two parts: ‘φς (phōs)’ a Greek word meaning light, and ‘volt’, a word coined in honour of the inventor of the electric battery, Alessandro Volta ( 1745-1827). It is produced when sunlight is converted into energy with the use of solar cells or semiconductors. -Photovoltaics is the field of technology and research related to the practical application of photovoltaic cells in producing electricity from light, though it is often used specifically to refer to the generation of electricity from sunlight. Photovoltaics (PV) is a method of generating electrical power by converting solar radiation into direct current electricity using semiconductors that exhibit the photovoltaic effect. Photovoltaic power generation employs solar panels composed of a number of solar cells containing a photovoltaic material. Materials presently used for photovoltaics include monocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, and copper indium gallium selenide/sulfide. Due to the increased demand for renewable energy sources, the manufacturing of solar cells and photovoltaic arrays has advanced considerably in recent years . II. HISTORY Photovoltaic energy has been discovered for almost two centuries. Photovoltaic effect was first discovered by a 19 year old French experimental physicist named Edmund Becquerel while he is experimenting with an electrolytic cell made up of two metal electrodes. Until in 1954, Bell Labs researchers Pearson, Chapin, and Fuller reported their discovery of 4.5% efficient silicon solar cells. Then in 1964 the Nimbus spacecraft was launched with a 470-W PV array which was its first practical application. However, it was not until 1940 that the first modern solar cell manufacturing began. This used silicon as the semiconductor material, patented by the American inventor, Rusell Ohl. In 1955, the American utility, Western Electric, began to market solar cell arrays. The first practical applications for these devices were in artificial satellites. They were an efficient way of providing electricity to remote bodies. Vanguard 1 thus became the first satellite to use a photovoltaic module to feed the transmitter, which consumed a mere 5 milliwatts. By the mid-70's, photovoltaic modules began to be used in different terrestrial applications. These included clocks, games and calculators. Over recent decades, photovoltaic technology has continued to advance, leading to the development of photovoltaic systems connected to networks. This has triggered an industry whose main objective is to supply modules for large photovoltaic farms to generate electricity on a quite different scale. In this market, T- Solar has become the byword for excellence. III. PROCESS Photovoltaic (PV) cells are made up of at least 2 semi-conductor layers. One layer containing a positive charge, the other a negative charge.

description

Overview of Photovoltaic Energy and its uses.

Transcript of Photovoltaic Energy

Photovoltaic Energy

Paolo Abagar, Mario Miguel Celdran, Arjan Delos Santos, Keno Hibaya, Kevin Richard Miraflores, Lovely Jane Vallinas

EE 147

Energy Conversion EECE Department

Mindanao State University – Iligan Institute of Technology Iligan City, Philippines

I. INTRODUCTION

The term "photovoltaic" has two parts: ‘φῶς

(phōs)’ a Greek word meaning light, and ‘volt’, a word

coined in honour of the inventor of the electric battery,

Alessandro Volta ( 1745-1827). It is produced when

sunlight is converted into energy with the use of solar

cells or semiconductors.

-Photovoltaics is the field of technology and

research related to the practical application of

photovoltaic cells in producing electricity from light,

though it is often used specifically to refer to the

generation of electricity from sunlight.

Photovoltaics (PV) is a method of generating

electrical power by converting solar

radiation into direct current electricity using

semiconductors that exhibit the photovoltaic effect.

Photovoltaic power generation employs solar

panels composed of a number of solar cells containing a

photovoltaic material. Materials presently used for

photovoltaics include monocrystalline

silicon, polycrystalline silicon, amorphous

silicon, cadmium telluride, and copper indium gallium

selenide/sulfide. Due to the increased demand

for renewable energy sources, the manufacturing of

solar cells and photovoltaic arrays has advanced

considerably in recent years .

II. HISTORY

Photovoltaic energy has been discovered for

almost two centuries. Photovoltaic effect was first

discovered by a 19 year old French experimental

physicist named Edmund Becquerel while he is

experimenting with an electrolytic cell made up of two

metal electrodes. Until in 1954, Bell Labs researchers

Pearson, Chapin, and Fuller reported their discovery of

4.5% efficient silicon solar cells. Then in 1964 the

Nimbus spacecraft was launched with a 470-W PV

array which was its first practical application.

However, it was not until 1940 that the first

modern solar cell manufacturing began. This used

silicon as the semiconductor material, patented by the

American inventor, Rusell Ohl. In 1955, the American

utility, Western Electric, began to market solar cell

arrays.

The first practical applications for these

devices were in artificial satellites. They were an

efficient way of providing electricity to remote bodies.

Vanguard 1 thus became the first satellite to use a

photovoltaic module to feed the transmitter, which

consumed a mere 5 milliwatts. By the mid-70's,

photovoltaic modules began to be used in different

terrestrial applications. These included clocks, games

and calculators.

Over recent decades, photovoltaic technology

has continued to advance, leading to the development

of photovoltaic systems connected to networks. This

has triggered an industry whose main objective is to

supply modules for large photovoltaic farms to generate

electricity on a quite different scale. In this market, T-

Solar has become the byword for excellence.

III. PROCESS

Photovoltaic (PV) cells are made up of at least

2 semi-conductor layers. One layer containing a

positive charge, the other a negative charge.

The photovoltaic process converts sunlight,

which is the most abundant energy source on the planet,

directly into electricity. The sun emits photons (light),

which generate electricity when they strike a

photovoltaic cell. So in the same way a photovoltaic

cell, made from a semi-conducting material, is a device

that converts light into electricity.

Sunlight consists of little particles of solar

energy called photons. As a PV cell is exposed to this

sunlight, many of the photons are reflected, pass right

through, or absorbed by the solar cell.

When sunlight strikes the solar cell, electrons

are knocked loose and move toward the treated front

surface of the solar cell. This creates an electron

imbalance between the front and back of the cell and

causes electricity to flow – the greater the intensity of

light, the greater the flow of electricity.

Solar cells are made of silicon, a special type

of melted sand, consisting of two or more thin layers of

semi-conducting material, usually silicon. The layers

are given opposite charges – one positive, one negative.

When enough photons are absorbed by the

negative layer of the photovoltaic cell, electrons are

freed from the negative semiconductor material. Due to

the manufacturing process of the positive layer, these

freed electrons naturally migrate to the positive layer

creating a voltage differential, similar to a household

battery.

When the 2 layers are connected to an external

load, the electrons flow through the circuit creating

electricity. Each individual solar energy cell produces

only 1-2 watts. To increase power output, cells are

combined in a weather-tight package called a solar

module. These modules (from one to several thousand)

are then wired up in serial and/or parallel with one

another, into what's called a solar array, to create the

desired voltage and amperage output required by the

given project.

Due to the natural abundance of silicon, the

semi-conductor material that PV cells are primarily

made of, and the practically unlimited resource in the

sun, solar power cells are very environmentally

friendly. They burn no fuel and have absolutely no

moving parts which makes them virtually maintenance

free, clean, and silent.

Illustrations:

Photovoltaic effect was first observed by

French physicist A. E. Bacquerel in 1839. Photovoltaic

effect is directly related to the photoelectric

effect.When the sunlight or any other light is incident

upon a material surface, the electrons present in

the valence band absorb energy and, being excited,

jump to the conduction band and become free.

Illustration:

These highly excited, non-thermal electrons

diffuse, and some reach a junction where they 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.

IV. TYPES OF PV CELLS

Monocrystalline Silicon Cells

These are made using cells sliced from a single

cylindrical crystal of silicon, this is the most efficient

photovoltaic technology, typically converting around

15% of the sun's energy into electricity. The

manufacturing process required to produce

monocrystalline silicon is complicated, resulting in

slightly higher costs than other technologies.

Polycrystalline Silicon Cells

Also sometimes known as multicrystalline cells, these

are made from cells cut from an ingot of melted and

recrystallised silicon. The ingots are then saw-cut into

very thin wafers and assembled into complete cells;

they are generally cheaper to produce than

monocrystalline cells, due to the simpler manufacturing

process, but they tend to be slightly less efficient, with

average efficiencies of around 12%.

Thick-film Silicon

This is a variant on multicrystalline technology where the

silicon is deposited in a continuous process onto a base

material giving a fine grained, sparkling appearance. Like

all crystalline PV, it is normally encapsulated in a

transparent insulating polymer with a tempered glass

cover and then bound into a metal framed module.

Other Thin Films

A number of other materials such as cadmium telluride

(CdTe) and copper indium diselenide (CIS) are now being

used for PV modules. The attraction of these technologies

is that they can be manufactured by relatively inexpensive

industrial processes, certainly in comparison to crystalline

silicon technologies, yet they typically offer higher

module efficiencies than amorphous silicon. Most offer a

slightly lower efficiency: CIS is typically 10-13%

efficient and CdTe around 8 or 9%. A potential

disadvantage is the use of highly toxic metals such as

Cadmium with the need for carefully controlled

manufacturing and end of life disposal, although a typical

CdTe module contains only 0.1% Cadmium which is

reported to be a lower quantity of the metal than is found

in a single AA-sized NiCad battery.

V. ADVANTAGES

1. Available nearly everywhere

2. Inexhaustible and abundant

3. Clean energy

Solar power is clean energy with little

environmental impact, and does not release air

pollutants or noise while it is being generated.

Compared to other means of generating power

(hydraulic, nuclear, thermal), it demands little in

terms of installation condition or scale. The

distance between the point where the energy is

generated and consumed is therefore short and

keeps power loss minimal during supply. With few

moving parts in its system it has no mechanical

corrosion and long life. Above all, it benefits from

an infinite source of energy.

4. Production end-wastes and emissions are

manageable

5. Noise Free

6. Less transmission/distribution losses

7. protects against rising energy prices

8. Excess heat can be used for co-generation

9. There is room for improvement

10. Long-lasting

11. Maintenance and operating expenses are low

Solar Energy systems are virtually maintenance

free and will last for decades. Once installed, there

are no recurring costs. They operate silently, have

no moving parts, do not release offensive smells and do not require you to add any fuel.

12. Get paid

13. Solar energy systems are now designed for

particular needs. For instance, you can convert

your outdoor lighting to solar. The solar cells are

directly on the lights and can’t be seen by anyone.

At the same time, you eliminate all costs associated

with running your outdoor lighting.

VI. DISADVANTAGES

1. Expensive

This is due to its installation, any regulatory fees,

semi-conducting material used, and infancy.

2. Lack of consistency and reliability

We know that this system relies on the steady

absorption of sunlight. But there are factors that

limit the availability of sunlight:

Latitude – efficacy falls as the distance

from the equator increases.

Clouds/Weather

Night

3. Takes up a lot of space

4. Solar panels consume land, as power generation per

unit square is low

5. Panel deterioration

6. Environmental pollutants - A few of the more

notorious substances contained in panels and associated equipment include:

Cadmium.

Lead

7. Only areas of the world with lots of sunlight and

very low heat are suitable for solar power generation

8. When there is no solar energy to be collected you'll

have to have adequate battery backup to get you

through the nights and rainy days.

9. It takes a considerable amount of solar panels

depending on your location to produce the same amount of electricity

10. Current devices which utilize solar energy are

expensive.

11. Solar panels require quite a large area for installation to achieve a good level of efficiency.

12. Heat degrades the system faster and also degrades in time

VII. APPLICATIONS

1. Power Stations

As of July 2012, the largest photovoltaic (PV)

power plant in the world is the Agua Caliente Solar

Project in USA (247 MW).

Agua Caliente Solar Project

Some use innovative tracking systems that

follow the sun's daily path across the sky to

generate more electricity than conventional fixed-

mounted systems and there are no fuel costs or

emissions during operation of the power stations.

CEPALCO’S 1mwp Photovoltaic Power Plant

From the start of its commercial operations on

September 26, 2004, the PV plant has exported to

CEPALCO a total of 4,169,100 kWh or an average

of 1,389,700kWh annually

CEPALCO’s 1MWp plant, with installed costs

close to 5.3 Million US Dollars, uses 6,500 solar

panels on 2 hectares of land

2. In Buildings (Building-Integrated Photovoltaics

(BIPV)) and Rural Electrification

Photovoltaic arrays are often associated with

buildings or houses: usually mounted on top of the existing roof structure or on the existing walls.

Building-integrated photovoltaics (BIPV) are

increasingly incorporated into new domestic and

industrial buildings as a principal or ancillary source of electrical power.

A 2011 study using thermal imaging has

shown that solar panels, provided there is an open

gap in which air can circulate between them and

the roof, provide a passive cooling effect on

buildings during the day and also keep accumulated heat in at night.

3. In Transport

PV has traditionally been used for electric

power in space. It is being used increasingly to

provide auxiliary power in boats and cars. A self-

contained solar vehicle would have limited power

and low utility, but a solar-charged vehicle would allow use of solar power for transportation.

SINAG is the Philippines’ first entry to the

World Solar Challenge

4. Standalone devices

PV was used frequently to power calculators

and novelty devices.

Solar powered remote fixed devices have seen

increasing use recently in locations where significant

connection cost makes grid power prohibitively

expensive.

VIII. REFERENCES

[1.] http://www.solarenergy.net/Articles/how-

photovoltaic-cells-work.aspx

[2.] https://en.wikipedia.org/wiki/Photovoltaic_system

[3.] http://pveducation.org/pvcdrom/solar-cell-

operation/photovoltaic-effect

[4.] http://www.triplepundit.com/2012/04/solar-

photovoltaics-pros-cons/

[5.] http://www.triplepundit.com/2012/04/solar-

photovoltaics-pros-cons/

[6.] http://www.solarguide.co.uk/solar-pv

[7.] http://www.solarpowerplanetville.com/photovolta

ic-solar-panels-advantages-and-disadvantages

[8.] http://www.renewableenergyworld.com/rea/blog/

post/2012/12/advantages-and-disadvantages-of-

solar-photovoltaic-quick-pros-and-cons-of-solar-

pv

[9.] http://www.nef.org.uk/greencompany/active-pv-

cells.htm

[10.] http://www.tsolar.com/en/portal.do?IDM=242&N

M=2

[11.] http://www.powersourcesolar.com/5151/