studies on effect of solar collector types for low...
TRANSCRIPT
Abstract— One of the keys to make solar thermal system provide
more efficient was the suitability of solar collector. Nowadays, solar
thermal collectors have different methods to collect the thermal
energy from sun radiation; however the choice depends on various
issues but mainly location. In this paper we propose to determine the
appropriated type of solar collector for low temperature hybrid solar-
biomass thermal system (HSBTS). The efficiency, the value of
investment, the patterns of use, net solar aperture and stagnation
temperature are the actually the main criteria to considered. A review
of solar collector types is presented. The most suitable collector type
for Thailand’s low temperature hybrid solar-biomass thermal system
(HSBTS) in Thailand is Fresnel due to highest value of investment
and low of land used.
Keywords—Solar thermal collector, Hybrid solar thermal
system, solar collector type.
I. INTRODUCTION
OWADAYS, Thailand is increasing attention to the
renewable energy source due to the energy problem. The
department of alternative energy development and efficiency
in Thailand is progressing the use of renewable energy source
from 20% to 25% of final energy consumption in 2021 [1].
Especially in solar energy source, which producing average 5
kWh/m2 per day, the target was increased from 2,000 MW to
3,000 MW, but at present solar source used is only 554 MW.
[1]
The use of solar thermal systems is very interesting among
the solar energy source applications. But the problem of solar
energy source was the system stability because of day light
period limitations. However, to improve the system stability is
to grant ability that make its can operate during nighttime. The
previous research result shown that this hybrid system can
provide power all day operate [2][3][4]. The Hybrid Solar-
Biomass Thermal System (HSBTS) is the most attractive
Nattakorn Phetwiwat is with the Rattanakosin College for Sustainable
Energy and Environment (RCSEE), Rajamangala University of Technology
Rattanakosin, 96 moo 3 Puthamonthon Sai 5, Salaya, Puthamonthon,
NakhonPathom, 73170 Thailand (corresponding author’s phone: +661 017
8412; e-mail:[email protected]).
Narong Vatcharasathien, is with Research and Develop department,
Electricity Generating Authority of Thailand, 53 Moo 2, Charan Sanitwong
Road, Bangkruai, Nonthaburi 11130 Thailand (e-mail: [email protected]).
Joseph Khedari is with the Faculty of architecture, Kasetsart University,
Bangkok Thailand (e-mail: [email protected]).
pattern among another hybrid solar thermal system, because
the biomass are inexpensive sources and highly available in
Thailand.
However research result in Kenya [5], shown that we can
increase the stability and efficiency for daytime by using the
combination in different types of solar collector. So HSBTS in
Thailand has not many extensive researches about suitable
type of collectors that can improve outcome energy. This
paper is to selecting of solar collector types which appropriate
for low temperature HSBTS for Thailand.
II. HYBRID SOLAR-BIOMASS SYSTEM
The hybrid solar-biomass system that use for this
experiment has been designed as Fig. 1. This system is
designed by using simple Rankine cycle for a small scale
hybrid solar-biomass system, with the capacity of 10 kW,
maximum temperature 150-200 °C with different working
fluid and use parabolic troughs solar collector type according
to G.Pikra’s previous research work [6].
Fig. 1. Diagram of Solar Thermal power system (1.Solar
Collector; 2.Fuel burner; 3.Thermal Storage; 4.Return Oil Pump;
5.Hot Oil Pump; 6.Evaporator; 7.Turbine;8.Generator; 9.Condenser;
10.Feeder Pump)[6]
III. SOLAR COLLECTOR TYPES
Types of solar collector for concentrated solar power (CSP)
have different suitable working condition e.g. temperature
ranks, land usage, cleaning water consumption, that can
classifieds into 4 types.
A. Figures and Tables
Parabolic troughs type is a single-axis tracking solar
collector that use reflect of parabolic curved glass mirrors for
focusing the solar energy to receiver at focal axis (Fig 2). The
Studies on Effect of Solar Collector types for
Low Temperature Hybrid Solar-biomass
Thermal Power Plant
Nattakorn Phetwiwat, Narong Vatcharasathien, and Joseph Khedari
N
International conference on Innovative Engineering Technologies (ICIET’2014) Dec. 28-29, 2014 Bangkok (Thailand)
http://dx.doi.org/10.15242/IIE.E1214063 119
shape of a parabola would make solar rays will be reflected
toward the focus. Most losses in such collectors are due to
imperfections in the parabolic shape and imperfect reflection.
It can control temperature output by control receiver’s fluid
flow rate, lower flow rate more temperature output. This type
of collector has thermal limit about 380-450 °C [5] [8], with
different working fluid. This collector type is cheap to
construct, simple to operate and easy to maintenance.
However, this type of collector has low power output [5] [8].
It is good for desert areas or place where is clear sky and no
sunlight shortage.
Fig. 2 Diagram of parabolic trough
B. Solar Tower
Solar tower type is based on the use of very large
concentrating collector. The optical system consists of a field
of a large number of 2-axis sun-tracking mirrors, each
reflecting beam radiation onto a central receiver. The
difference of this collector type concept was the way to
receiver energy. All of the solar energy to be collected in the
entire field, is transmitted optically to a small central
collection region rather than being piped around a field as hot
fluid (Fig 3). This type of collector has highly efficient and
high thermal output (around 540 to 840°C) [7] [8]. However,
they really need a large space to place all reflectors, can’t
work efficiently without tracking system and can’t be used on
cloudy days.
Fig. 3 Diagram of solar tower
C. Linear Fresnel
Linear Fresnel is a collector that use flat mirrors which
concentrate solar beam in a fixed linear receiver placed at
focal point above these mirrors (Fig 4.), it’s quite similar to
the parabolic trough types. This type of collector has thermal
output about 200 to 400°C [10] [14]. Linear Fresnel type is a
really lower price than parabolic because it uses flat mirror
design to concentrate sun that simpler production and
installation, simple to operate and easy to maintenance.
However, it suitable for small plant size (2-200MW) and has
low thermal output when compare to another types.
Fig. 4 Diagram of linear Fresnel
D. Big Dish Technology
Big Dish Technology or Parabolic dish is a parabolic-
shaped reflector mirror that concentrates the solar radiation to
the receiver at a single focal point so it is really high reliable
collector type. With 2 axis tracking system, these type of
collector is a environmentally friendly alternative to acquire
sun energy that suitable for wide open area as deserts (Fig 5.).
This collector type could concentrate energy to provide steam
temperatures around 500 to 1,000 °C [11] [12].
International conference on Innovative Engineering Technologies (ICIET’2014) Dec. 28-29, 2014 Bangkok (Thailand)
http://dx.doi.org/10.15242/IIE.E1214063 120
Fig. 5 Diagram of big dish Technology
IV. COMPARISON AND SELECTION THE SUITABLE SOLAR
COLLECTOR TYPE
The main criteria to consider which collector type that the
most suitable for HSBTS, is efficiency, the value of
investment, the patterns of use, net solar aperture, stagnation
temperature and working fluids.
A. Total cost and land use
After reviewed the existing collector technologies, the
comparative data of total cost, construction and maintenance
cost, and land use are shown as Fig 6 [15] [16].
Fig. 6 Comparative data of solar collector types in total cost and land
use criteria
The Parabolic Dish is the highest of total cost when
compare to another types while solar tower is the highest of
land use and Linear Fresnel and Parabolic trough are no
different in total cost. To select a type for different area, land
use might less concern than total cost, parabolic trough and
linear Fresnel are attractive option. Giorgio Cau and Daniele
Cocco [14] also support this choice, they concern about
medium size solar concentrating power plant and found that
both linear Fresnel and parabolic trough are good choice for
medium plant, if the total cost is the main criteria then
parabolic trough is the best choice but if land use is main
criteria linear Fresnel is the best one. However to choose the
best one form both criteria they suggest that an economic
analysis is required to identify the one.
B. Efficiency and Reliability
The comparative data of efficiency of collectors is shown as
Fig 7.
Fig. 7 Comparative data of solar collector types in efficiency criteria
The solar tower is the highest efficiency and high reliability
type that should be the best choice for solar collector if both
efficiency and reliability are main criteria. However the other
types that got medium on reliability and lower efficiency are
best for other criteria too.
C. Temperature tolerance
After using simulating model from TRNSYS 15 for
different solar collectors in the same solar data and working
system. The tolerances for temperature are shown as Fig 8.
Fig.8 Comparative data of solar collector types in temperature
tolerance criteria
Energy output from simulating for different solar collectors
with a year solar data in Thailand are shown as Fig 9.
Fig 8 shown that solar tower has a wide working
temperature while linear Fresnel is really the lowest
temperature tolerance rank. But the suitable one for HSBTS in
Thailand should the one that got tolerance about 150-200 °C.
So it should be solar tower and linear Fresnel types for this
criteria. Fig 9 shown that solar tower has a highest energy
output but the lowest energy output is parabolic trough, even
it has high efficiency but it got low reliability. To selects type
of collector in energy output criteria, it was up to propose of
used.
International conference on Innovative Engineering Technologies (ICIET’2014) Dec. 28-29, 2014 Bangkok (Thailand)
http://dx.doi.org/10.15242/IIE.E1214063 121
0
5
10
15
20
25
30
35
5-6
6-7
7-8
8-9
9-10
10-1
1
11-1
2
12-1
3
13-1
4
14-1
5
15-1
6
16-1
7
17-1
8
18-1
9
Ener
gy o
utp
ut
(kW
h)
day-hour
Parabolic trough Solar Tower
Linear Fresnel Parabolic Dish
Fig. 9 Comparative data of collector types in energy output
All main criteria to make a decision, which one is suitable
for the selected solar power plant systems. For HSBTS in
Thailand, it’s design for remote area, low temperature and low
cost, the Fresnel types are more suitable than other types. The
critical criteria for remote area are temperature tolerance and
total cost because suitable temperature tolerance for HSBTS
mean longer lifetime of system and total cost is really
important for investment in remote area. Fresnel types can
produce suitable temperature for steam (100-300 °C), lowest
land use, for Linear Fresnel type, and low cost. With this all
criteria, the most suitable for hybrid HSBTS is turn to Linear
Fresnel type. J.D. Nixon investigated the best solar thermal
collection technology for electricity generation in north-west
India. This study shown that the linear Fresnel lens with CPC-
type secondary is the recommend solar collector type because
of their potential low cost and high reliability make Fresnel
worthy of further investigation [16].
V. CONCLUSIONS
HSBTS in Thailand was analyzed to find the main criteria
for select a suitable solar collector type for Thailand plant.
The plant characteristic for Thailand is work for lower
temperature steam (150-200 °C), low cost and easy to setup
and operate in remote area. With this temperature range
criteria, the solar tower and Linear Fresnel Reflector are a
good choice to choose. However, with total cost and land use
criteria, Linear Fresnel reflector system is the best one that
more suitable for Thailand plant. From all criteria, found that
the most attractive solar collector type is linear Fresnel
because of the critical criteria for remote area in Thailand is
total cost, with lowest total cost, medium efficiency, medium
energy output and suitable temperature tolerance make Linear
Fresnel is the most attractive solar collector for remote area in
Thailand.
ACKNOWLEDGMENT
The authors are grateful to Prof.Jongjit Hirunlabh for useful
advice and suggestion.
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