CHAPTER 3-Solar Edit

8/3/2019 CHAPTER 3-Solar Edit

1/19

CHAPTER 3

3.1 Solar Cell

A solar cell is a device that takes the energy of sunlight and converts it into

electricity. Solar cell also known as photovoltaic cell.

The most common types of solar cells are based on the photovoltaic effect, which

occurs when light falling on a two-layer semiconductor material produces a potential

difference, or voltage, between the two layers. The voltage produced in the cell is capable

of driving a current through an external electrical circuit that can be utilized to power

electrical devices.

Solar cells are made of semiconductor materials. Semiconductors are materials

which become electrically conductive when supplied with light or heat, while acting as

insulators at low temperatures. Over 95 % of all solar cells produced worldwide are made

of semiconductor material silicon (Si). Silicon has the advantage that it is available in

sufficient quantities as the second most common element in the earth's crust and the

material can be processed in an environmentally-friendly manner.The efficiency of solar

cells is between 10% till 12%. Solar cell must have a low reflectivity and high photon

absorption coefficient. The typical solar cell should be rated at about 0.45V, 0.8A


2/19

3.2 Operating principle of solar cell

Figure 1: Electron and Current flow in solar cell

In a typical photovoltaic cell, two layers of doped silicon semiconductor are

tightly bonded together (illustrated in Figure 1). One layer is modified to have excess free

electrons (termed an n-layer), while the other layer is treated to have an excess of electron

holes or vacancies (a p-layer).

When two dissimilar semiconductor layers are joined at a common boundary, the

free electrons in the n-layer will cross into the p-layer in an attempt to fill the electron

holes. The combining of electrons and holes at the p-n junction creates a barrier that

makes it increasingly difficult for additional electrons to cross. The electrical imbalance


3/19

reaches an equilibrium condition, a fixed electric field results across the boundary

separating the two sides.

When light of an appropriate wavelength (and energy) strikes the layered cell and

is absorbed, electrons are freed to travel randomly. Electrons close to the boundary (the

p-n junction) can be swept across the junction by the fixed field. The electrons can easily

cross the boundary, but cannot return in the other direction (against the field gradient), a

charge imbalance results between the two semiconductor regions.

Electrons being swept into the n-layer by the localized effects of the fixed field

have a natural tendency to leave the layer in order to correct the charge imbalance.

Towards this end, the electrons will follow another path if one is available.

By providing an external circuit by which the electrons can return to the other

layer, a current flow is produced that will continue as long as light strikes the solar cell.

In the construction of a photovoltaic cell, metal contact layers are applied to the outer

faces of the two semiconductor layers, and provide a path to the external circuit that

connects the two layers. The final result is production of electrical power derived directly

from the energy of light.

3.3 Polycrystalline solar cell

Polycrystalline silicon photovoltaics are a type of solar cell. Silicon solar cells are

manufactured with a microstructure tailored to the application depending on economic

and performance requirements.

Polycrystalline silicon is composed of many smaller silicon grains of varied

crystallographic orientation. This material can be synthesized easily by allowing liquid

silicon to cool using a seed crystal of the desired crystal structure. Additionally, other

methods for crystallizing amorphous silicon to form polysilicon exist such as high

temperature chemical vapor deposition (CVD).

3.4 Thin Film

The sun blasts Earth with enough energy in one hour 4.3 x 1020 joules to provide all

of humanity's energy needs for a year (4.1 x 1020 joules), according to physicist Steven


4/19

Chu, director of Lawrence Berkeley National Laboratory. The question is how to most

effectively harness it.

Thin-film solar cells may be the answer: One recently converted 19.9 percent of the

sunlight that hit it into electricity, surpassing the amount converted into power by mass-

produced traditional silicon photovoltaic and offering the potential to unleash thisrenewable energy source.

Prices for high-grade silicon (that can generate electricity from sunlight) shot up in

2004 in response to growing demand, reaching as high as $500 per kilogram (2.2 pounds)

this year. Enter thin-film solar cellsdevices that use a fine layer of semiconducting

material, such as silicon, copper indium gallium selenide or cadmium telluride, to harvest

electricity from sunlight at a fraction of the cost.


5/19

In figure 2 below shows the table of various types of solar photovoltaic cells and

their modules that usually used in detail like their efficiency, performance, environmental

impact etc. Other than that they also have photoelectrochemical cell and dye sensitized

solar cell.


6/19

Figure 2: Photovoltaic cells and their modules

3.5 Photovoltaic (PV) cell efficiency versus cost

This matrix provides an indication of the relationship between cost and

efficiency of photovoltaic material. The most efficient, but also most costly remains the

multi-junction material. Therefore, this material is only used in cases where area

limitation is the most important factor, for instance in space technology. Otherwise, this

material is only used in conjunction with concentrating devices as outlined above.

Note that this picture only shows the relationship between photovoltaic

efficiency and cost of photovoltaic material rather than cost of the total system. Low

efficiency may impact on costs for mounting, wiring and land ownership, as more area

needs to be covered for the same rated power. Hence, costs could go up further even

when module costs per kWh are the same.

Figure 3: PV cell efficiency VS cost

3.6 Solar energy

Solar energy is an alternative source of energy power production. The sun

delivers a constant stream of radiant energy. The amount of solar energy coming towards


7/19

the earth through sunlight in one day is same with the energy produced by burning many

millions of tons of coal. Solar energy reaching the earth in tropical zones is about 1

kW/m per day. The main problem is to develop methods for controlling and utilizing the

energy of the sun. There are two methods for collecting and concentrating solar energy.

Both these methods involve a mirror like reflective surface.

i. Uses parabolic mirrors to capture the energy of the sun. Mirrors

concentrate the energy from the sun by focusing the light onto an opaque

receiving surface. Suppose the heat is focused onto the tubes where water

is circulated. Then the water can be turned into steam. This steam can

drive a turbine. The mirrors must be rotated to such a position that ensures

the best light reflection.

ii. Uses a flat plate solar collector. Layers of glass are laid over a blackenedmetal plate, with an air space between each layer. These layers of glass act

as a heat trap. They allow the rays of the sun in, but keep most of the heat

from escaping. The heated air could be utilized to warm a home. The

heated air would be stored in an insulated tank and then pumped into the

house through pipes and radiators.

3.7 Solar power plant

There is several type of solar power plant application used around the world. Thetechnologies below are frequently applied to solar power plant.

3.7.1 Solar thermal power plant


8/19

Solar thermal power plants also work in a few different ways. The most common

type uses a parabolic trough design. In these plants, commonly known as concentrated

solar power (CSP) plants, several rows of trough-shaped, parabolic mirrors are

strategically designed to capture and concentrate the sun's rays onto a focal point; much

like a child might use a magnifying glass to burn ants. That point is a black pipe running

the length of the row of mirrors. Inside this pipe is a transfer fluid, which heats up to very

hot temperatures, often upwards of 300 degrees Fahrenheit. The heated fluid is piped to a

power generator, where its heat is used to boil water, creating steam and electricity.

Figure 4: Concentrated solar power plant


9/19

Figure 5: Parabolic trough

A concentrated solar power plant in principal works no differently than

conventional steam power plant. However, there is one important difference. When

concentrated solar power plant operates it does not harm to the environment by burning

coal, oil, natural gas or by splitting uranium to produce steam. It is produced solely by the

energy that comes from the sun.

In order to achieve the high temperatures required, solar radiation must be

concentrated to a point or a line. Parabolic trough collectors represent the most advanced

technology for use in doing this. These troughs are more than 1,300 feet (400 meters) inlength and are made up of parabolically shaped mirror segments. The troughs track the

sun over the course of the day and focus the resulting radiation along the caustic line of

the mirrors onto specially coated, evacuated absorber tube receivers.

Another version of a solar thermal power plant is a "power tower." Power towers

take CSP technology in a new direction. Mirrors are situated to focus solar radiation onto

a single focal point: a tall tower which houses a receiver that boils water to create steam.

Mirrors are usually connected to a tracking system that allows them to follow the sun

across the sky. Power towers have some key advantages, such as smaller footprints and

relatively fast construction time.


10/19

Figure 6: operation of solar thermal power plant

Referred to figure 4, the solar irradiation is reflected by the heliostats (sun

tracking mirrors) to a single spot at the top of the Solar Tower. The concentrated solar

irradiation hits the volumetric receiver and heats it up to a temperature of 680C.

Ambient air is sucked through the porous absorber material by two blowers. The

hot air enters the steam generator to produce superheated steam with a pressure of 26 bar

pressure and 480C. This steam is fed to a steam turbine.

The air leaves the steam generator at a temperature of 120 C and is transported

back to receiver to cool its support structure and recover the remaining energy. In times

of high solar power the energy can be stored in a thermal storage system.

Figure 7: Solar Thermal Power Plant Tower Jlich, Germany

For the Jlich demonstration plant all system components are located inside the

tower. This is not necessarily the case for a large power plant.
http://www.vicerp.de/files/files/IMG_3167_web_th.jpg


11/19

Depending on the solar irradiation the thermal storage the plant can charged or

discharged (also together with solar operation) by adjusting the power of the two blowers.

Thus, a parallel process like storage load and steam production is possible. The Solar

Tower Power Plant Jlich features the follow parameters:

i. Electric power approx. 1.5 MW

ii. Area of single mirror: approx. 8 m

iii. Number of sun-tracking mirrors: 2150

iv. Area mirrors power plant approx. 18000 m

v. Storage capacity approx. 1 to 1.5 hours

3.7.2 Solar photovoltaic (PV) power plant

PV plants utilize solar power panels to convert solar radiation directly into

electricity. Photovoltaic plants are very straightforward. Several solar power panels are

installed to form an array. Typically, a handful of panels will be "strung" together in

series on a single mounting system. Each set of panels collects solar energy, converts it

directly into electricity, and sends that electricity through wiring to the electric grid. PV

power plants are relatively rare because solar thermal power is currently much more

efficient at producing electricity on a large scale.


12/19

Figure 8: Grid-connected, large-scale installation

Junction Box

In large-scale installations, multiple modules are connected through a junction

box, which is just that, but also provides surge protection.

DC Switch

In order to be able to undertake repair or general maintenance work, the solar

generator must be separated from the inverter. This is achieved by a DC switch close

to the inverter. As the modules continue to generate electricity as long as there is

sufficient light, the DC switch must cope with the short-circuit current as well as theopen-circuit voltage. Just unplugging a string of modules may cause a corona with a

risk of fire. Some manufacturers of inverters offer integrated DC switches.

.


13/19

Inverter

Inverters used here will most likely produce a 3-phase AC, which is more

common in industrial contexts.

Transformer

An optional transformer may step up the voltage to very high voltage required

by the grid.

AC Switch

An AC switch is required by grid operators to ensure safety. It automatically

switches off the grid connection if error currents, changes in frequency or voltage are

detected.

Maximum Power Point Tracker (MPP)

As described, the mpp- tracker ensures that the module operates at its maximum

power point at all times. Most inverters also include the maxium power point tracker

(mpp).

Where crystalline modules are used, partial shading of the entire roof (for instance

caused by a tree or the chimney), the module will only generate as much current as its

weakest string. In this instance, each string should have its own mpp- tracker,

resulting in efficiency gains of up to 8% according to Stecca.

Figure 9: The 71.8 MW Lieberose Photovoltaic Park in Germany.


14/19

Figure 10: Nellis Solar Power Plant, 14 MW power plants installed 2007 in Nevada, USA

Solar Farm

Solar farms are farms that utilize the sun for the energy needed to run efficiently and with less

cost to the owner. The suns energy is used by using mirrors and solar panels placed throughout

the property to direct light to other areas of the farm where they can then be used for electricity.

Solar farms are becoming much more popular throughout the United States. Florida and

California are currently leading the country with the number of solar farms and there are plans in

place for more to be built soon.

By farmers using solar farms as opposed to traditional farms, it can reduce their costs which can

in turn reduce the cost that consumers pay to purchase the food. There may be a larger initial

coat for the farmer to install the solar panels on their property, but many farmers will agree that itis worth the initial investment. Solar farms are also better for the environment as there are

utilizing natural resources.


15/19

Solar Panel Cost

In this article we are going to discuss solar panel cost , which is really two different questions.

When people ask the question, How much willsolar panels cost, they could really be asking

either, How much does a solar panel cost, or How much will it cost for enough solar panels to

power my house?

The first question is more directly related to solar panel cost, so well cover that first. The answer

is a little tricky because it depends on whether you are planning to buy pre-made solar panels or

make them yourself. For premade solar panels, a single panel can cost about $900, or $12 per

watt. A medium sized system to provide power to a small or very energy efficient house might

cost $25,000 and a solar system to power a large house could cost $50,000+.

Most people dont know this, but it is actually fairly easy to build your own solar panels. With a

few common tools, the right knowledge and some effort on your part, you can build a solar panel

for as little as $200.

There are many federal, state and local tax credits, rebates and incentives available that can

reduce solar panel cost. These incentives could save you up to half the cost of a solar power

system. You can check the website for your state government to see what is available in your

state.

The second possible meaning of a question about solar panel cost is, How much will it cost for

enough solar panels to power my house? It is difficult to give an answer for a specific house

because there are a lot of factors including how much electricity your houses uses, where in the

country you live (and how much sun you get), which direction your house faces, etc. So, in order

to answer the question, well make some assumptions and give answers for a typical house.

In order to figure out the solar panel cost for your home, the first thing you need to know is how

much electricity your house uses. The best way to figure this out is to look at a monthly

electricity bill to see how many kilowatt hours or KWH you use per month. Multiply the KWH

by 1000 to get your monthly Watt/Hours of electricity. If you divide that number by 30, that is

your average daily electricity usage. Then youll need to divide that number by the average

number hours of sun per day you get in your location. To be safe, use the number of hours per

sun on the day of the year with the shortest amount of daylight. Now you know how much

electricity you need to generate per hour of daylight to power your home.


16/19

Why solar is less used

The initial cost is the main disadvantage of installing a solar energy system, largelybecause of the high cost of the semi-conducting materials used in building one.

The cost of solar energy is also high compared to non-renewable utility-supplied

electricity. As energy shortages are becoming more common, solar energy is becomingmore price-competitive.

Solar panels require quite a large area for installation to achieve a good level ofefficiency.

The efficiency of the system also relies on the location of the sun, although this problemcan be overcome with the installation of certain components.

The production of solar energy is influenced by the presence of clouds or pollution in theair.

Similarly, no solar energy will be produced during nighttime although a battery backupsystem and/or net metering will solve this problem.

As far as solar powered cars go - their slower speed might not appeal to everyone caught

up in today's rat race. The maintenance can be an issue. When yoursolar energy goes out, you cant just call

the power company. If you dont have an experienced photovoltaic energy technician inyour area or if you are not willing to be a bit of a handyman, maintenance is definitely anissue! But if you think you can handle minor repairs now and then, youll be fine. Solarpower is very dependable and usually requires little work.

The proper disposal of the panels and the batteries when they are at the end of theiruseful life is important. Both the storage batteries and the panels contain materials thatare very toxic. Lead, sulfuric acid, and cadmium telluride are all used in the manufactureof either the batteries or the panels. The batteries are 98% recyclable and technologypromises advances in the development of more eco-friendly photovoltaic cell production .

Disadvantages of solar panels are there, but most of them are decreasing with the advances intechnology. Assess your solar situation wisely. Determine how many watts your household useson average and at peak usage. Look up your sun exposure in an almanac. Incorporate thisinformation into a list of advantages and disadvantages of solar panels as they apply to yoursituation. Then you can figure out how photovoltaic power can work for you.
http://www.solarenergy-solarpower.com/what-is-solarenergy.htmlhttp://www.solarenergy-solarpower.com/what-is-solarenergy.html


17/19

SOLAR PANEL MAINTENANCE

Solar electric systems use something called photovoltaic cells to capture the energy of the sun.

These cells are the means by which the suns energy is converted to electricity to either be

directed straight into the household for power or stored in batteries to be used later.

Fortunately, residential solar panels do not require much maintenance, but there are somethings you can do to increase the longevity of your solar electric system. One aspect that

makes solar panels fairly maintenance-free is that there are no moving parts to rust, break

down or wear out. This certainly cannot be said of a generator which has belts, hoses and other

confusing parts you have to replace. There is also no need of refueling it as it collects all its fuel

automatically from the suns rays.

What you do need to do is ensure that yoursolar panels are wiped and clean. A dirty panel willbe far less affective in collecting energy from the sun if much of the rays are being blocked bydirt and grime. Fortunately, for most climates there is a good bit of rain every year which acts to

clean yoursolar panels. The next time you are negative about the cloudy, rainy day because youare not gathering solar energy, think of it as day off for the panels to receive some maintenance.Snow, however, is a form of precipitation that will affectively block the rays from reaching thepanels. Snow removal in the winter is important because there are still plenty of sunny days evenduring this time of year.

If you have made the wise decision to switch to Solar Panels as your primary form of energyproduction, rest assured that the only maintenance you must perform is a regular check thatnothing is blocking the panels from soaking up the sun. If you are debating about making theenvironmentally and fiscally sensible switch, understand that photovoltaic panels are extremelyreliable and cost effective. If you are waiting for the scientific breakthrough that makes themmore feasible, you are waiting in vain because it has already happened.

Maintaining Your Solar Panel

Whether a solar panel system is designed to generate heat for our homes or produce electricity, aproperly functioning solar panel is an obvious requirement. Luckily, a well-designed andinstalled solar panel system is durable and simple in concept. In fact, the only part of a solarheating system that has any moving parts requiring maintenance is the pump. Plus, while earlierversions of solar panels were relatively fragile, solar panels are now constructed from strongunbreakable materials, so a solar panel itself requires minimal maintenance to continue doing itsjob. Essentially the only breakable part of a solar panel is the glass covering. Maintaining a solarpanel is very straightforward; here's all that's necessary.

Instruction
http://www.allsolarproducts.net/http://www.allsolarproducts.net/


18/19

1) Inspect the solar panels on a periodic basis (frequency depends on location or the

manufacturer's specifications) to remove any debris and dirt and ensure all connections

are tight.

2) Panels installed in dusty areas may require more frequent inspection.

3) Clean the surface of a solar panel with warm water and dishwashing soap to remove any

accumulation of dirt and grime.

4) Remove any bird droppings as well since they can severely reduce the panel's energy-

producing capacity.

5) Cleaning a solar panel is not cosmetic. A panel needs to be clean for it to operate at its

rated capacity.

Checking Solar Panel Operation

The only other part of solar panel maintenance is monitoring their energy output and ensuring

there are no malfunctions. Check and log the power output on your solar inverters display on a

daily or monthly basis. With this data, you can then check to see if your solar panels are

functioning at full efficiency. Solar panels produce different amounts of power during the year,

so keeping a baseline measurement helps.


19/19

Solar farm maintenance

A farming opportunity with low maintenance and overheads

A solar farm has none of the labor intensive nature and ongoing overheads of traditionalfarming. No water is needed, no herbicides or pesticides, no vet bills, early morning starts or latenight paddock checks. You'll also be able to provide your own farm with clean, renewablepower. There's next to no maintenance involved - the sun does all the hard work for you; makingyou money while leaving you frees to do other things. Solar farming can easily integrate withyour farm's current activities - all you'll need is under an acre of land or 500 square meters ofNorth facing roof area.

A solar farm is a great return on investment, particularly considering the low maintenanceinvolved and the reassurance of guaranteed income. Additionally, components in a gridconnected solar farm have no moving parts and the solar panels have an output guarantee of 25

years. By installing solar farm equipment, you'll also considerably boost the value of yourproperty.

CHAPTER 3-Solar Edit

Documents