Abstract: Concentrated Solar Power (CSP) technology is one of the most promising candidate for mitigating the future energy crisis. The extracted power from CSP technology is very clean, reliable and environmental friendly. An overview of CSP technologies like Parabolic Trough, Solar Tower, Parabolic Dish, Linear Fresnel technology have been described in this paper. Comparison among these technologies has been illustrated in this work. For extenuating the present power crisis in Bangladesh CSP technology has great opportunities, since the average Direct Normal Irradiance (DNI) in Bangladesh is 4-6.5 KWh/m 2 which is suitable for all types of CSP technology. Suitable locations for different CSP plants in Bangladesh are also proposed on the basis of efficiency, required area and amount of DNI received. DOI: 10.1109/ECACE.2017.7913020

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An Overview of Concentrated Solar Power
(CSP)Technologies and its Opportunities in
Bangladesh
Rabiul Islam, A.B.M. Noushad Bhuiyan, Md.Wali Ullah
Department of Electrical and Electronic Engineering
Chittagong University of Engineering and Technology
Chittagong, Bangladesh
rabiul.islam@cuet.ac.bd, noushad.cuet1202065@gmail.com, waliullah.cuet.1995@gmail.com
Abstract— Concentrated Solar Power (CSP) technology is
one of the most promising candidate for mitigating the
future energy crisis. The extracted power from CSP
technology is very clean, reliable and environmental
friendly. An overview of CSP technologies like Parabolic
Trough, Solar Tower, Parabolic Dish, Linear Fresnel technology
have been described in this paper. Comparison among these
technologies has been illustrated in this work. For extenuating
the present power crisis in Bangladesh CSP technology has great
opportunities, since the average Direct Normal Irradiance (DNI)
in Bangladesh is 4-6.5 KWh/m² which is suitable for all types of
CSP technology. Suitable locations for different CSP plants in
Bangladesh are also proposed on the basis of efficiency, required
area and amount of DNI received.
Keywords—Energy;CSP;DNI;Solar Tower;Parabolic Trough;
I. INTRODUCTION
Energy crisis is the most familiar and disquieting matter of
now-a-days. Suitable and reliable energy sources are the best
solution of this crisis. There are two type of energy sources:
conventional energy and renewable energy. The familiar
conventional energy sources are coal, natural gas, oil, crude
oil etc. Use of conventional energy sources has multi-faceted
environmental and health hazards. Burning of fossil fuel like
coal and oil produces photochemical pollution from nitrous
oxides and acid rain from Sulphur dioxide. It also produces
greenhouse gases that causes the phenomenon of global
warming. There sources are also diminishing at an alarming
rate.
In this circumstances, we have to looking forward to ‘green
energy’ for electricity generation. Green energy means
environment friendly and non-polluting energy (such as solar,
biomass, wind, tidal etc.). Among these, wind energy is suited
for large scale power generation as it is requiring coastal or
hilly areas and much wind speed. Biomass and tidal are also
suitable for small scale individual purpose. Limited
availability of organic wastes and vegetation restricts the
widespread use of biomass energy. Only solar energy has full
potential to recover the existing power crisis without polluting
our environment. Two types of solar energies are solar
photovoltaic(PV) and solar thermal also known as a
concentrated solar power(CSP).
While solar PV system could take up to 10m² of roof space on
the other hand just 3m²-4m² for CSP. CSP can turn around
90% of solar radiation into heat, whereas solar PV has
efficiency of between 15%-20%. Now a days CSP becomes
very popular all over the world. USA and SPAIN gives special
interest to it. The state of California is likely to produce 33%
within their total energy implementing solar technology by
just 2020 which 88% will CSP and rest individuals will be
solar PV. [1]. In this paper an overview of CSP technologies
are outlined and its opportunities is described.
II. TECHNOLOGY OUTLINE
In CSP technology, sun’s direct normal irradiation(DNI)
concentrated on HTF (Heat Transferred Fluid). which is then
passing through a series of heat exchangers to produce super-
heated steam. This steam is converted to electrical energy in a
conventional steam turbine. A portion of heat is also stored in
some liquid or solid media (such as molten salts), concentrate
[2] for use at night or during the times when there is no
sunlight thus continuing turbine operation. [4].
General working flow diagram of CSP is given in Fig. 1:
Fig. 1. General Flow Diagram of CSP Plant [4].
Fig. 1: General Flow Diagram of CSP Plant [1].
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III. DESCRIPTION OF TECHNOLOGY
There are different CSP technologies but their basic
principle in generating electricity is same. The structure and
the focus of these systems are different, so they resulting in
different temperature ranges that are generated. The CSP
systems are divided into Line focusing systems and point
focusing systems.
In Fig. 2 flow diagram shows different CSP systems [2]:
Fig. 2: Classification of CSP systems.
A. Line focusing systems
Line focusing systems concentrate the solar radiation
onto a linear absorber tube or series of tubes, then reflectors are
tracked about a single axis so as to keep sun’s image focused
onto the liner absorber tube. It’s also known as single axis
tracking technologies. Heat Transfer Fluid(HTF) is inside the
tube which could be water, steam or synthetic oil. HTF
transfers its absorbed heat to a steam turbine power cycle.
Range of the operating temperatures from about 350°C to
about 550°C [2]. The Parabolic Trough system and the Linear
Fresnel Reflectors system are the example of Line focusing
Technology.
a) Parabolic Trough System
Most matured concentrated solar design for utility scale
solar power plant is the parabolic trough technology. It
consists of several parallel curved mirrors that focus the sun’s
ray onto a receiver tube containing a heat transfer fluid.
Six major part of a parabolic trough concentrator system,
which are as follow (i) Reflecting surface, (ii)Absorber, (iii)
Support structure, (iv) Tracking system, (v) Conventional
electricity generation unit and (vi) Thermal storage (optional).
Fig. 3 shows different parts of parabolic trough collector.
It tracks the sun over the course of the day along the central
axis as the sun travels east to west. The reflectors have a
property of collecting parallel rays along a single line focus
which are parabolic trough shaped.
They reflect the solar radiation and concentrate it onto a
receiver tube that is located at the focal line of the parabola.
The concentrated solar radiation increase heats of HTF and
then transforms into thermal energy. During all over the day
the parabolic trough collectors (PTC) track the position of the
sun. To collect DNI efficiently a driver motor is used.
Two different methods used to track sun:
i. First method: It involves photocell sensors on the
PTC that can track the position of the sun.
ii. Second method: It involves astronomical algorithms.
By using very accurate mathematical algorithms
calculate the sun elevation and azimuth every second
of the day and the angular position of the rotation
axis using electronic devices also measured [5].
The reflector designed with a 0. 85mm silver precious
coated mirror for the back layer and a 4mm glass of
substantial transmittance that situated in the top of it. They get
high reflectivity about 93. 5%. Diameter of a stainless-steel
tube is 70mm with high temperature absorption coating which
encircled by the vacuum glass tube of 115mm diameter with
antireflective coating comprise the receiver tube. [6].
Tube contains HTF (synthetic oil) which heated up to
400°C by the DNI of solar [1]. working diagram of a PTC
power plant shown in Fig. 4. During sunny day HTF in tube
heated up by DNI and pass to steam power plant then they
preheat water, generates steam in steam generator. Also,
superheats the steam, then discharge heat and circulated back
to SCF to complete cycle again.
Continuing operation during nighttime or cloudy days the
system equipped with most popular storage system called
ʻTwo -tank molten salt storage system’. That consists of a hot
tank, a cold tank and a heat exchanger. During day time a
portion of heated HTF transferred to heat exchanger and
pumped cold molten salt. In the heat exchanger, Cold molten
salt receives thermal energy from HTF and stored in the hot
tank. At nighttime or cloudy days, the hot molten salt back its
thermal energy to the cold HTF used to generate steam. By
using thermal storage system an annual capacity factor of 70%
[6]. Solar thermal power plant can be hybrid with fossil fuel
fired back up system for supplying peak loads in sunny days
or continue operation in cloudy days.
b) Liner Fresnel Reflector System
It’s another line focusing technology. It’s also single axis
tracking mirror aligned along a north-south axis, able to track
sun from east to west [3]. Different from PTC is it uses
Fresnel reflector which are flat in shape and pipe is distant
from the reflection unit. The pipe is connected to the steam
turbine to produce electricity conventionally by producing
mechanical torque.
Fig. 3. Parabolic Trough Solar Collector.
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Fig. 4. Parabolic Trough Power plant with fossil fuel back up and thermal storage system.
Thermal storage of molten salt to make system applicable
during cloudy day and night is also used by the system. The
system is easier to install, easy production, cost effective,
cheaper than other CSP system [5]. Fig. 5 shows liner fresnel
reflector.
B. Point focusing systems
All the concentrators would concentrate the sun radiation at
a central point (focal point) in this method. Solar Tower and
Parabolic Dish are the examples of point focusing systems.
Fig. 5. Liner Fresnel Reflector [1].
a) Solar Tower System
Power tower technology system utilize the sun-tracking
mirrors called heliostats to concentrate the solar radiation onto
a receiver at the uppermost portion of a tower. A heat transfer
fluid heated in the receiver up to 1300°C and convert this heat
into thermal energy which is used to generate superheated
steam for the turbine [6]. Fig. 6 shows solar tower with central
receiver. Working cycle of solar tower power plant shows in
Fig. 7, which is similar as parabolic trough system.
In early power tower, steam is used as the heat transfer
fluid but now a day’s molten salt is used as its higher heat
transfer and energy capabilities. From an optical perspective,
power tower remains high winter performances as the
elevation of the sun in the sky is tracked by heliostat mirrors
from east to west.
Fig. 6. Solar Tower System [4] .
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Fig. 7: Solar Tower Power Plant with fossil fuel back up and thermal storage system.
It is also more efficient as its storage system eliminate the
heat transfer oil, lowering the molten salt requirement and
better compatibility with air cooling. The world largest
operational CSP plant Ivanpah solar plant in California which
capacity Is 392 MW is employed solar power technology.
b) Parabolic Dish System
Among all CSP designs Parabolic dish have high electricity
conversion efficiencies which is up to 30% [9]. This system
uses parabolic dish shaped solar concentrator that focus the
sunlight onto a onto a single central receiver in front of the
mirror. These concentrator tracks solar radiation with a two-
axis tracking system. The collected heat is directly used by a
Stirling engine that is attached to the receiver. Fig. 8 shows a
parabolic dish.
Single Brayton cycle can also be used for power
consumption where air, helium or other gas is compressed,
heated and expanded into a turbine. Then the mechanical
energy is converted to electrical energy with the help of an
alternator. A parabolic dish of 25-KW capacity has a required
diameter of about 10 meters [9].
Fig. 8. Parabolic Dish [1].
IV. PRESENT SCENARIO OF CSP IN WORLD
After introducing in 1990, CSP is getting popular more and
more. In last seven years, Global CSP capacity has more than
5 times increasing to almost 5GW in October 2016 from less
than 1GW in 2010 [12]. Now a day’s size of CSP is increasing
due to reduce cost through economics scale. Because of
regulatory restrictions plants in Spain have been limited to
50MW but new projects in USA in elsewhere are in the 150-
500MW range and even larger. [2]
Approximately 4,810.55MW CSP power plant all over the
world is now under operation, over 1466.9MW is under
construction 5706.08MW in USA, SPAIN, SOUTH AFRICA,
AUSTRALIA, INDIA, CHAINA and many other countries
[10]. TABLE Ⅰ shows the progress of CSP technology in the
world.
V. POWER SCENARIO OF BANGLADESH
Bangladesh is a densely populated and small country but
with a few sections of are taking the blessing of power.
According to the United States Energy Association (USA) the
energy supply deficiency in Bangladesh is 19%. Bangladesh
Power Development Board (BPDB) has taken a massive
capacity expansion plan to add about 11600 MW generation
capacity in next 5 years to achieve 24000 MW within 2021
while present installation capacity is 13,000MW
(November’2016) [8].
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From existing power demand govt. has two resources:
convention energy and renewable energy. Among the
convention energy coal, natural gas, oil, crude oil etc. Use of
conventional energy has multi-faceted environmental and
health hazards. Burning fossil fuel like coal and oil produces
photochemical pollution from nitrous oxides, and acid rain
from Sulphur dioxide. It also produces greenhouse gases that
causing the phenomenon of global warming. Moreover,
present coal reserved is only 2,041 million tons and remaining
reserve capacity of gas is 13 Tcf which will be depleted within
10 to 12 years [11].
At this situation, we have look up to renewable energy.
Within 2030, 6% of total power of the country will be
produced from renewable energy [8]. Of all renewable energy
sources, solar is most suitable and effective source. Up to
2021, It is targeted that Bangladesh will find 3167.8MW from
renewable energy. Almost 54.93% of the will found from solar
[13]. Power generation from solar energy is monopolized by
PV in Bangladesh. The current installed capacity (November
2016) of solar PV is 200.23MWe which is only 1.54% of the
total power generation [ 8].
VI. OPPORTUNITIES IN BANGLADESH
There is requirement of abundance DNI for smooth
operation of CSP plant. The intensity in the radiation that
originates directly through the sun prior to scattering is
described as Direct Normal Irradiation (DNI). Bangladesh is
located at an ideal condition which is between 20.30°-26.38°
north latitude and 88.04°-92.44° east. Sunlight gets almost
perpendicularly at the place of near the equatorial plane.
Fortunately, Bangladesh is very much close (23.50° North) to
the equatorial line. Here from figure we find that solar
radiation is varies between 4 to 6.5 KWh/m² in all over the
country. For CSP technology there is needed annual average
Direct Normal irradiations(DNI) 2000KWh/m². In
Bangladesh, there is abundant of solar radiation annually
which is nearly 1900 KWh/m² [1]. Average DNI of
Bangladesh is shown in Fig. 9.
Labour cost is cheaper in Bangladesh than any other
developed countries, so 15% cost reduction might be possible.
Raw materials of most of CSP power plants are glass and steel
sheet.
a.
ref [1] b.
ref [7] c.
ref [10]
Bangladesh has become self-sufficient in glass production.
Now glasses are being exported in many countries [17]. More
than 400 steel re-rolling company is under operation in
Bangladesh. This will lessen investment cost and also create
more jobs for unemployed people [18].
VII. SUITABLE PLACEMENT OF CSP TECHNOLOGIES
CSP is a most promising technology in the sector of power
generation. Thermal storage system makes it more preferable
because it continued operation at night time and cloudy days.
The system gives output as three-phase AC electricity.
But installation costs are higher in comparison with
conventional fossil fuel technologies. It has been claimed that
cost will reduce in future come from economies of scale of the
plant size, manufacturing industry, learning effects, advances
in R&D, a more competitive supply chain and improvements
in the performance of the solar field, solar to electricity
conversion efficiency and thermal energy storage systems.
Among four types CSP technology Parabolic trough is highly
developed and it deserves the most commercial experiences. It
is suitable for large scale power generation though it’s require
large area. In Bangladesh, it is suitable for west Bangle, hilly
region, river bank. Power tower technologies require high
temperature producing facilities and less land compare to
parabolic trough. It is suitable in desert area of the country.
Fig. 9: Average DNI in BANGLADESH [21].
Technology
World capacity
2009(MWe) a
World capacity
2012 (MWe) b
World capacity
2016 (MWe) c
Opera-
tional
[MW]
Under
construc-
tion [MW]
Plann-
ing
phase[MW]
Opera-
tional
[MW]
Under
Construc-
tion [MW]
Planning
phase
[MW]
Operat-
ional
[MW]
Under
Construction
[MW]
Planning
Phase
[MW]
Parabolic
Trough
570 1690 5775 778 1400 8144 4109 715 530
Solar Tower 8.4 22 1514 44 17 1664 627.9 461.4 2330
Parabolic Dish .5 1600.08 2 1 2247 2 2.5 72.08
Linear Fresnel 34 487 9 30 134 37.65 117 10
TABLE Ⅰ. Progress of CSP Plant in World.
JAN FEB MAR APR MAY JUN JULY AUG SEP OCT NOV DEC
1
2
3
4
5
6
7
8
Average
DNI
(
KWh/m
2
/Day
)
Month
Dhaka
Chittagong
Rajshahi
Sylhet
Rangpur
Khulna
Pabna
Cox's Bazar
Fig. 9. Average DNI in Bangladesh [21].
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aref [7] b. ref [19] c.ref [20]
Parabolic Dish system is the most efficient CSP system
though it is undergoing development to make the system more
cost effective. Parabolic dish system could use to enable an
interconnected power generation system at the multistoried
building’s roof top of the mega cities. Linear Fresnel system is
cost effective than parabolic trough and solar tower though it’s
requires large land areas for setting up. It is suitable for rural
area and also in cultivable land.
VIII.CONCLUSION
Bangladesh is a non-oil producing country, coal reserves
will last for only the next few decades, recoverable gas will be
depleted soon. So, in future solar energy will be the major
energy source in Bangladesh. Present power crisis can be
alleviated greatly without depending on conventional fossil
fuel, oil, gas and without threatening the environment by
installing and utilizing CSP technology. A pilot project should
be taken as early as possible to verify the feasibility of non-
polluting and CO2 emission free CSP technology. In
Bangladesh, parabolic trough is suitable for large scale power
generation. Solar tower power plant should be in second
option by considering land utilization. On the other hand
Parabolic dish is suitable for small scale power generation
units.
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Technology Short description Annual solar to
electricity efficiencya
Storage Tempe-rapture
(°C) b
Cost
($/W) c
Parabolic trough Long, curved mirror
Parabolic sheet of reflective material
12-15% Molten salt 300-550 4.0-2.7
Linear Fresnel Flat mirror instead of curved mirror in
parabolic trough
8-10% Storage has not been
perfected
250-500 2.2
Parabolic dish Parabolic mirror is used to focus heat
directly on a Stirling engine
20-30% Does not accommodate
thermal storage
400-1500 12.6-
1.3
Solar tower It contains large heliostat field with
tall tower in its center
20%-30% Molten salt 300-1000 4.4-2.5
TABLE Ⅱ. TECHNOLOGICAL COMPARISON.
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