1

Abstract

There are many ways to harness the solar energy which is the

most clean and sustainable energy. It can be used to generate

electricity and heat at high temperature as per the requirement.

Now a days there are many devices like photovoltaics thermal

hybrid, concentrated solar technologies, solar furnace and solar

fuels. In order to meet the human requirement it is necessary to

take an account the cost and efficiency associated with the

current technology.as per the current demand of the energy

consumption, only solar energy has the potential to fulfill the

requirement as a renewable resource. From an economic and

ecological perspective the devices available can be used

accordingly. From the photovoltaic the levelised cost of

electricity generation is very close to the cost of thermal

electricity thus in future it will prove to be major technological

area. Efficiency of photovoltaic is increased by making it a

hybrid type power plant. Solar furnace can be used to obtain

heat directly in various application where direct heat sources

are required. Concentrated solar power plants and solar fuels

are currently in developing phase with only minor contribution

to the current energy supply. Solar fuels development can led

to total dependence on solar energy possible.

Introduction

With the rapid Industrialization and Globalization the global

energy demand has been steadily increasing since the last 40

years. In year 2008, the total global energy consumption

reached 4741018 J (474 exa-joules), out of which 8090% is

coming from combustion of fossil fuels only [1]. The steady

gradual increase in the consumption of fossil fuel has led to a

drastic climate change, with 14 of the 15 most warm years on

record occurring since 2000.[2]

The International Energy Agency have estimated that the

developing countries need to double the installed power

generation capacity in order to fulfil the growing energy

demand by year 2030 and the world energy consumption is to

be increased by 44% up to 2030.[1]

By using only 0.1% of the available land on earth earths with

solar power collectors with the collection efciency of 20%, we

could generate more electrical power than the electrical power

demand of all inhabitants of our mother Earth[9]. In recent

past due to the rapid increase in the Environmental Pollution

level and global warming issue there is huge growth observed

in the photovoltaic solar based technology market. Nowadays

due to new development of industrial hub the levelized cost of

the solar energy has fallen down and is about to meet the cost

of commercial electricity, with the current growth rate of

technology the solar electricity cost will soon be available with

a competitive price for the daily household use.[3].

Nomenclature

PV = Photovoltaic

P = Maximum Power Generated by PV cell

Vos = Open Circuit Voltage

Isc = Short Circuit Current

FF = Fill Factor (P/(Vos x Isc))

T = Ambiance Temperature

Tc = Collector temperature

CSP = Concentrated Solar Power

COST AND EFFICIENCY ANALYSIS OF DIFFERENT SOLAR BASED DEVICES: A REVIEW

Adarsh Kumar, Gaurav Gupta School of Mechanical Materials & Energy Engineering

Indian Institute of Technology Ropar Rupnagar 140001, Punjab, INDIA

*Corresponding author: Gaurav GuptaTel: 7814326401; E-mail: gauravgupta@iitrpr.ac.in

2

Photovoltaics

Photovoltaics fundamentally are solid semiconductor devices

which covert the solar Irradiation directly to electrical energy,

they are made up of either mono crystalline, poly crystalline,

ribbon crystalline or amorphous (micro crystalline) silicon,

gallium, copper-indium-selenide and cadmium telluride

materials.

Phovoltaic panels are made up of a laminate structure of series

wired multiple solar cell as individual cells have very less

voltage output of 0.5V. [3]

The operation principles of solar cells is the higher energy

Photons i.e. with greater energy as compared with the band-

gap energy of the semiconductor are absorbed and excite the

valance electrons towards the conduction band thus, leaving

behind holes in the valence band. The electron and hole pairs

generate an electric field in the depletion layer of the pn

junction the electric eld present in the depletion region

separates them and drives them through an external load. When

the impedance of the circuit matches the load of device

maximum power gets delivered.

The solar conversion efficiency for a solar cell is given by.

[5][3]

= Vos x Isc x FF/P

The power and other properties for the solar panels are

generally rated for STP conditions i.e. 250C at 1atm pressure

with 1.5 AM Solar Mass and Irradiation of 1000W/sq.m From

the date of invention of Solar cells, besides that the solar energy

is being available for free and these Photovoltaics have not been

considered in past for large scale electricity generation because

of its high cost. Solar panels have of manufacturing, high cost

of equipment and installation high levelized cost of electricity.

Thus, restricting its use but from the recent few years as the

people all around the globe are becoming more concern about

the renewable energy consumption because of the

environmental degradation, the use of solar based technology is

increasing abruptly, and the photovoltaics are leading the chart

as it directly converts solar energy into electrical energy. [4][5]

The Globally installed Photo Voltaic capacity has risen from

1.8 GW in 2000 towards 177 GW in 2014, on an average it is

the fasted growing energy sector with a growth rate of 48%. The

rapid interest in the renewable solar based technology and

environmental impact along with rapid development in solar

PV technology has cause a significant rapid cost reduction.

Nowadays is a wide range of PV available in the market today,

they uses different technology and different types of material

they are classified into three generation category on the basis of

used material and commercial production technology.[4][5]

First generation Photovoltaics, they are made up of wafer

based crystalline silicone of two types, single crystal or poly

crystal. These types of PV have the largest share in the global

market of nearly 87% up till 2010, although the silicone is one

of the most abundant element on earth but the cost of these

photovoltaics are very high. They have efficiency of about 14-

19%, the wafers of silicon are generally 200-300m.[3][4][9]

Second generation Photovoltaics, they are made up by thin

film Photovoltaic technology, it consist of amorphous Silicon,

Microcrystalline Silicone, Copper-Indium-Gallium-Diselenide

, (Cu-In-GA-Se), Copper Indium-Selenide (Cu-In-Se),

Cadmium-Telluride (Cd-Te). They are the result of 20-30 years

wide extensive research, they need less material for

manufacturing and they have in principal low levelized cost of

electricity production. They are made up of successive thin

layer of just order of 1-4 m.[3][9]

Amorphous Silicone PV cells and microcrystalline silicone

have efficiency of the order of 4-8%, and the efficiency even

drops down by years, thsus the lower cost in production is being

compensated by the lower efficiency and they generate

electricity at a higher levelized cost.[3][4]

Copper-Indium-Gallium-Diselenide and Copper Indium-

Selenide have the highest efficiency among all thin film solar

cells of order of nearly 18%. Cadmium-Telluride solar cells

have efficiency of 16% and they are the most economical thin

film technology. The only drawback is they are toxic.[3][4][9]

Third generation Photovoltaics, they are under developing

phase and not have been commercialized yet, like Organic

Photovoltaics, Dye based Photovoltaics and Concentrating

Photovoltaics, they are very inexpensive but are very

inefficient.[4][9]

Organic photovoltaics cells are made up of organic or

polymeric material they having efficiency of only 4-6% they

are also unstable over time. Dye-sensitized solar cells are made

up of photo-electrochemical they too have 4-5% efficiency.

Concentrating PV uses optical devices to concentrate the direct

solar insolation in a small, efficient multi-junction based solar

cells made up of semiconductors like Germanium, Gallium

Arsenic, Indium Gallium Arsenic and Indium Gallium

Phosphorus. They have very high efficiency of order of 40-

50%, they have a drawback that the concentrated solar

irradiance use to increase the temperature of the solar cell and

they tends to reduce the efficiency of the solar cell.[9]

To rectify that effect they need a cooling system, and Solar

Thermal Hybrid energy system is an outcome to use the thermal

energy by the raised temperature of the solar cells. Cost is the

prime factor in the production of Photovoltaics, from the time

of Photovoltaic development the module use to consist of 60-

70% of the cost of total PV system but since 2008 there is a

random decline in the module cost and now it is available for

cheap. [3][4]

As of now the learning decline rate of the price of Photovoltaic

3

modules is around 20% which means that for the each time

photovoltaic cumulative installed capacity has doubled the

module cost have declined by 20%, one of the possible reason

for that is the entrance of Chinese companies in the PV

manufacturing market, despite the rapid growth and easy

availability the solar energy have only 1% share in the global

installed capacity.[4][5][6]

The rapid development in past time, has brought down the cost

of the high power solar modules INR. 810,000/kW in 1982 to

INR. 200,000/kW in 2006 the installation cost of a PV system

has also declined to INR 240,000/kW in 2008 as compared to

INR 640,000/kW in 1992. It is keeps on decreasing further now

with a decline rate of 45% since last 5yrs with each 22%

reduction with doubling of cumulative volume

production[4][5][6]

The levelized cost of electricity from different types of PV cells

have fallen down due to increase in its efficiency, life time of

solar panels and the decrease in the capital investment for the

Module installation, the levelized cost of Electricity is nearly

INR 6.64 7.85 for life time of 25yrs with 10% decline in

performance in first 10yrs than 25% decline in next 15 yrs. The

point to notice is that the levelized cost of currently available

amorphous PV cells are more than crystalline PV cell this is due

to the rapid reduction in the efficiency of amorphous PV cells,

for the current development scenario the levelized cost of the

PV cells will beat the cost of thermal based electricity at that

time it will be further good for utility.[5][6]

Ecological footprint of the Solar Power is comparable with the

other PV Technologies. The land required to use construct a

Hydro Power Plant is quite huge as compared with the solar

power plant, Thus it have a low Ecological footprint.[7][8]

Solar Thermal Hybrid

Another and the most prominent type of Solar Technology is

Solar Thermal Hybrid Power panels, as the temperature

increases the efficiency of the solar panel decreases, the solar

thermal hybrid power collector utilized that thermal energy to

produce electricity, the cooling system of the panel with

flowing some fluid uses many technologies have to produce

sufficient energy for the Rankine Cycle Power Plant, as nano-

fluid.[6]

Although the cost of the Solar panel rises due to the installation

of Cooling mechanisms but the overall efficiency of the system

tends to increase by rapidly up to 65-80%. Reducing the

levelized cost of the electricity produced with not much effect

in the Ecological Footprint. There are also projects on wind-

solar hybrid and wind-solar-thermal hybrid technology.

[6][7][9]

Solar Furnace

Solar furnace one of the best option to utilize the solar energy

if we have to use the solar energy in the form of heat. It

concentrated solar irradiation by heliostats and parabolic

mirrors on the focal point to produce high very high

temperatures up to an order of 30000C with concentration factor

of 5000. Solar furnace is an old technology of back 18th century,

a French person Antoine Lavoisier made a solar furnace which

can reach temperature of 17500C which was used to melt copper

and iron like metals. [10]

This huge amount of heat can be used for chemical purposes, to

melt down metals for industrial purposes, to

generate electricity, and to produce hydrogen fuel for fuel

cells.[11]

The conversion efficiency () is function of Carnot efficiency

and receiver efficiency [11]

= reciver x carnot

= (1 (T4)

IC) X (1 (

Tc

T))

Image Source[2]

Small Solar furnace can be used for heating the home, could

be used as water heater and be used as an cooking equipment,

for the concentration ratio to be nearly 1000-1500, the

Levelized cost is INR 6.4/KWh which is less than the

commercial cost of electricity in India.

With the recent development of the Optical Cavity Furnace the

thermal efficiency of the solar furnace will show a gradual

increase in next few years as it will decrease the .[12]Solar

furnace can be used to for the production of Hydrogen based

fuel for Fuel cells[13].

Ecological footprint the solar furnace is quite low as compared

with the traditional Thermal and Hydro Power Plant, it

doesnt emits C02 and other Green House Gases.[14]

4

Energy payback time of the solar furnaces are used to be

nearly 4-6 years for large furnaces for small furnaces it is used

to be 8-10years and the life time are 30 years.[9]

In India small scale Solar furnace are used for Solar

Cremation, which will reduce the deforestation and is more

ecofriendly as compared with the Electrical Cremation, on an

whole, it save 200-300kg of wood for each cremation . [15]

Concentrated Solar Power Plant

The concentrated solar power plant provides a greater

opportunity for harnessing the solar power. They work in High

temperature range since no semiconductor device is used

harness solar energy. Solar radiation is concentrated at a single

point by the use of multiple mirrors or curved mirrors [17]. The

high temperature heat generated is harnessed by using a carrier

fluid which has heat capacity and stability. Occasionally the

carrier fluid is water itself and thus steam is generated directly

in the solar concentrator. The steam is used to run the turbine.

However due to high working temperature, a separate fluid is

used to generate the steam for rankine cycle. The CSP plant on

a broadly consists of following hardware: 1. Glass for

concentrating solar radiation, 2. Solar collector with workingfluid, 3. Heat exchanger for generating steam, 4. Turbine for

electricity generation, and cooling system. All these component

require initial manufacturing cost and thus the

installation/setting up of a CSP plant does not necessarily an

environmental friendly process.[17] Various resources are used

to manufacture the component leading to high ecological

footprint and thus the working life time of the power plant

should be sufficient to counter the initial environmental impact.

Mostly impact is on Land resources, water resources and global

warming emissions.[18]

By changing the type of concentrator, different types of CSP

Plant configuration are possible which are 1. Trough collector,

2. Power tower system and 3. Dish systems [19]. These plant

configurations can effectively reach different operating

temperature and thus different output energy is obtained. The

largest CSP Plant is of tower system type, located in California

having a capacity of 392MW in an area of 4000 acres [20]. The

total cost of project is $2.18 billion [20]. The power plant is

expected to reduce the annual carbon dioxide emissions

however if the power plant will not operate for long time

successful recovery of the resource investment will not be

possible [20]. The efficiency of the CSP is summarized below.

Type Parabolic

trough

Linear

Fresnel

Solar

tower

Dish

Efficiency 20% 18% 35% 30%

High efficiency is obtained for point concentration type CSP in

which all the solar radiation is concentrated at a single point.

However high efficiency requires higher resources for the

construction thus parabolic trough are widely used for power

generation.[21] The overall efficiency of a CSP is the total

conversion efficiency of solar collector and thermal power

station. Currently in India, most of the operational CSP plant

are of parabolic trough type since cost of production and

maintenance is considerably lower than tower type plant [22].

Essentially CSP plant are set up in remote areas where high

amount of solar irradiance is received. According to NREL data

for annual average direct solar irradiance for India, some

regions of Karnataka near the Krishna basins and parts of

Rajasthan and Gujarat near Bans River are suitable for the

construction of the concentrated solar power plant.

Mirrors required may be silver plated for higher reflectance but

are costlier but aluminum plated mirrors are widely used

because of corrosion resistance property of aluminum. Carrier

fluid is generally of mineral salt. Other than this typical rankine

cycle based power plant construction is needed. For minimizing

the ecological and environmental impact, construction of bigger

power plant is generally suggested [23]. Generally for any CSP

plant, 20-24% of cost is invested in constructing the storage

facility for the power station. Mirrors take only 12% and heat

channeling device take 15% of the total cost.[24] Rest of the

amount is invested in maintenance and construction of power

generating part of the plant[25]. Mega solar power plant located

in anantapur city of Andhra Pradesh is a parabolic trough type

CSP plant with a total investment of INR 8480 million.

Solar Fuels

The earth receives a huge amount solar energy which can

completely satisfy the energy requirement. However the

dependence on traditional fuels is not yet diminished.

Continuous consumption of fossil fuels led to an increased

concentration of carbon dioxide in atmosphere which is

responsible for many changes in climate. One of the drawback

of the solar energy is that it is not available throughout the 24

hrs. So there is a need to store the solar energy for night usage.

However current technology is only advanced to store the solar

energy in modern batteries which is not economical and

environment friendly since battery production require resources

and many batteries will be required. One of the idea is to utilize

the process of photosynthesis. Photosynthesis utilizes the solar

energy and carbon dioxide to produce glucose [26]. However

glucose cannot be used as fuel. Thus artificial photosynthesis is

required using a proper catalyst which can convert atmospheric

carbon dioxide into appropriate chemical compound which can

be economically process to produce fuels. The fuels thus

5

obtained are called solar fuels [26[. These fuel have zero carbon

content and thus stores solar energy in the form of chemical

energy effectively [27]. The catalyst required should be occur

naturally or require little investment as such the higher cost will

led to non-sustainability. There is direct conversion of the solar

energy to make solar fuels which can be used for power

generation however indirect conversion of solar energy to

intermediate compound is much easier. These intermediate

compound can be used to make solar fuels although the

efficiency of conversion is reduced [27].

Production of hydrogen and methane is essentially a research

subject [27]. Hydrogen can be produced by the electrolysis of

water and methane can be produced from the reduction of

carbon dioxide. Both of these requires energy which can be

given by solar energy however appropriate catalysts are

required. Solar energy can also be used indirectly to produce

solar fuels. The photovoltaic cell can produce electricity to

electrolyze water and reduce carbon dioxide appropriately

however since there is a limit on conversion efficiency on solar

panel the overall efficiency of the process is reduce. The

economics of second process is quite acceptable. The electrodes

material is available however prone to corrosion thus require

periodic replacement. Solar energy in the form of heat can be

used generate solar fuel with much more efficiency. The

thermochemical reaction can take place in the collector part of

any concentrated solar power plants. Hydrogen can be produced

by boiling water at high temperature.

Conclusion

With rapid development in photovoltaic technology the

levelised cost of different solar devices has fallen down with

improvement in their efficiency. For those places where the

infrastructure for grid supply is not available small scale solar

power plant could be built in developing countries like India.

The levelised cost of solar furnace is minimum but has

limitations for thermal purpose only. The cost of concentrated

solar power plant depends on the scale of the CSP to be set up.

Least investment is required for the hardware corresponding to

the solar devices and maintenance cost is higher. The solar fuels

can be sustainable replacement for the traditional batteries and

has huge potential to fulfill the energy requirement. Although

the cost of solar thermal hybrid is more but currently it is the

most efficient technology. If somehow the levelised cost solar

thermal hybrid energy decreases, it will be a major boost in

power sector.

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