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44
Page 44-52 © MAT Journals 2018. All Rights Reserved
Journal of Thermal Energy Systems
Volume 3 Issue 3
Estimation of Captured Energy Using Novel Receiver for
Scheffler Dish Solar Collector
1Arjun Vyas, 2Dhaval Sodha, 3Jaydeep Chanani, 4Jaydip Fataniya, 5Parth Patel,
6Dhruv Patel, 7Deepjyoti Basak
1,2,7Assistant Professor, 3,4,5,6Students
Department of Mechanical Engineering, Parul University, Vadodara, Gujarat, India
Email:1arjun.vyas@paruluniversity.ac.in,7deepjyoti.basak@paruluniversity.ac.in
DOI: http://doi.org/10.5281/zenodo.1988961
Abstract
The study of appropriate receiver design is necessary for Scheffler dish solar collector to
identify the efficiency of capture of solar energy. In this study experimental analysis work
was carried out with an intention to prepare heat balance sheet of Scheffler dish solar
collector using novel receiver. The objective behind this study is to prepare a work for future
research in direction of increasing the energy collection efficiency of system.The study
reveals that with the help of developed novel receiver around 30 minutes of time is sufficient
to start receiving net positive energy capture from the system. Also two peak regions are
observed where maximum outputof steam was obtained during afternoon. The research work
has obtained around 80% of energy collection with the help of novel receiver for Scheffler
dish in comparison with the value available in the literature.
Keywords: Solar collector, concentrated solar thermal, heat balance sheet
INTRODUCTION
Capturing renewable energy in an efficient
way to reduce our dependency on fossil
fuels is the main objective of today‟s
engineering community working for
sustainability. Sun is the primary source
for all the renewable energies [1]. Solar
energy is radiant light and heat from the
Sun that is harnessed using a range of ever
evolving technologies such as solar
heating, photovoltaic, solar thermal
energy, solar architecture, molten salt
power plants and artificial photosynthesis
[2][3]. There is a continuous
developmentin technology to use solar
energy for cooking[4][5], water
heating[6][7], water distillation and
desalination[8][9], space heating[10][11],
milk pasteurization[12] and many more
areas[13]. The abundant solar radiation
can be used to meet the demand of low to
medium process heat required by various
industries and institutions. Concentration
of solar radiation to produce temperature
in the range of 100 to 450˚C or more is
called concentrated solar thermal (CST)
technology [14]. There are six
commercially available CST technologies
in India [15], namely,
Fixed focus automatically tracked
elliptical dish (Scheffler)
Dual axis tracked parabolic dish
Fresnel reflector based dish (Arun
dish)
Single axis tracked parabolic trough
concentrator
Non-imaging concentrators
Linear Fresnel reflector
Abedani et al‟s work on variation of
aperture size directly influenced the light
entry as well as radiated heat losses
through the aperture.At an optimum
temperature of 212.3oC, the global
maximum exegetic efficiency was foundto
be 21.41% with the respect to thermal
efficiency of 49.83% [16].A Scheffler
collector is a fixed focus solar radiation
concentrator which has a capacity to
increase the temperature of the receiver up
to 200 °C[17].
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Page 44-52 © MAT Journals 2018. All Rights Reserved
Journal of Thermal Energy Systems
Volume 3 Issue 3
This paper presents the energy analysis of
the receiver of a Scheffler dish solar
collector, to calculate the various losses
incurred in the process for capturing solar
energy by using peripheral temperature
distribution around the receiver. The aim
of this paper is to identify the energy loss
mechanism and prepare heat balance sheet
by conducting experiments to capture solar
radiation. This work will provide a new
dimension to researchers to develop novel
processes and modifications in current
technology available that convertssolar
energy into heat energy (steam).
Materials and Methods
Scheffler dish solar collector
Scheffler dish is a small lateral section of a
parabolic [18], which concentrates sun‟s
radiation over a fixed focus, with an
automatic single axis tracking.Key
components of Scheffler dish based system
can be classified on the basis of their
individual functionsas shown in Table 1:
The dish uses automatic daily tracking and
manual seasonal tracking mechanism to
ensure maximum optical efficiency of the
Scheffler dish solar collector [18].
Table:1.List of the components and instruments used
Components
Specification/Materials of the component
Photograph
Reflector dish
Solar grade mirror with low iron content. All
sections & bars made of standard mild steel
and channels of aluminium
Receiver
Black painted Aluminium receiver with a
provision to fill water inside it via lid.
Condenser Drum
PVC drum with cemented base for structural
stability and thermal protection and no-leak
sealed lid provision.
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Page 44-52 © MAT Journals 2018. All Rights Reserved
Journal of Thermal Energy Systems
Volume 3 Issue 3
K-Type Thermo
couple
Range - –454 to 2,300F (–270 to 1260 C)
Accuracy - Standard: +/- 2.2C or +/- .75%
Quantity – 7
Anemometer
Range – 0.0 – 45.0 m/s
Accuracy - ±3% ± 0.1
Operating temperature – 0- 50 °C
Operating humidity – Less than 80% RH.
In built temperature sensor – K-type
thermocouple
Solar Flux Meter
Range – 1999 W/
Accuracy - ±10 W/
Operating temperature – 5 - 40°C
Relative humidity – Below 70% RH
Data Logger
Used to display the temperature of thermo
couple
Range – 0 to 1200°C
Measurement
beaker
Used to collect and measure the condensate
from the PVC drum.
Two plastic beakers of 200ml.
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Page 44-52 © MAT Journals 2018. All Rights Reserved
Journal of Thermal Energy Systems
Volume 3 Issue 3
Receiver of Scheffler dish solar collector
An experimental model to capture the
solar energy was developed using local
available materials as listed in Table 1.
The main aim of making customised
receiver for the Scheffler dish solar
collector is derived from the idea of
experimentation. Using this receiver model
the following parameters are expected:the
surface temperature of the receiver, steam
temperature, heat energy conversion from
solar energy, energy loss mechanisms and
their measurements and finally to take
benefit of this research work in
understanding the applicability of
Scheffler dish solar collector in low and
medium temperature applications.
Fig:1.Developed receiver setup
Experimental setup with Scheffler dish
solar collector and thedeveloped
receiver
As can be seen from Figure 2 the
developed receiver is kept in direct focus
to the Scheffler dish solar collector.The
instruments attached with the receiver
vessel areK-type thermocouple, pressure
gauge, steam collection pipe and steam
regulating valve.For temperature
measurement we set the six thermo
couples at different positions, named
cooker surface temperature (T1, T2, T3, and
T4), steam temperature (T5), condenser
temperature (T6), and ambient temperature
(T7). All thermo couplesareconnected with
data logger thatshows the temperature of
all thermocouples.The pressure gauge
helps to keep the track of the pressure built
in the receiver. Steam regulating valve is
used to control the flow of steam. One end
of steam pipe is connected with steam
valve and other end is connected with
condenser drum, where steam is collected.
CAD model of the developed receiver is
shown in Figure 2.
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Page 44-52 © MAT Journals 2018. All Rights Reserved
Journal of Thermal Energy Systems
Volume 3 Issue 3
Fig: 2.CAD model of developed receiver
All the experiential work was carried out
at Bakshipanch School, Goraj, Vadodara
in the month of April 2018. Solar energy
recorded at the locationwhere experiments
were conductedmeasured during the days
of experimentation (7th, 8th, and 9th April,
2018) and plotted in Figure 3.
Fig:3.Direct Normal Irradiance Vs Time of the day
RESULTS AND DISCUSSION
After doing series of experiments in the
month of April, a set of readings of three
days are considered and the resultsshown
here. Figure 4 indicates the temperatures at
different locationsof the receiver
peripheral surface. It is clearly visible from
the chart that the highest temperature was
obtained at alocation where the solar
radiation wasbeing focused. It is
interesting to know that temperatures T2,
T3 and T4 which are located at the side
and back of the receiver surface have
almost same temperature values; however
T2 located at the farthest peripheral
distance from T1 temperature location.
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Page 44-52 © MAT Journals 2018. All Rights Reserved
Journal of Thermal Energy Systems
Volume 3 Issue 3
Fig:4.Peripheral temperature distribution of receiver vessel Vs time of the day
Apart from surface temperature of the
receiver, it is important to measure the
temperature of steam produced,
condensate temperature and ambient
temperature which are shown in Figure
5.The steam control valve was kept open
and hence constant condensate was
obtained and its measurement was taken as
shown in Figure 6.
Fig:5.Steam,condensate and ambient temperatures Vs Time of the day.
Fig:6.Volume of water collected Vs time of the day
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Page 44-52 © MAT Journals 2018. All Rights Reserved
Journal of Thermal Energy Systems
Volume 3 Issue 3
Figure 7 shows the absorbed energy by the
developed receiver and also the energy
transferred to water by means of steam
produced throughout the day. It is to be
noted that the energy absorption and loss
are two simultaneous processesoccurring
during the whole day of the experiment.
The key observation is that within 30
minutes from the start of the experiment
the amount of energy absorbed is equal to
the conduction, convection and radiation
losses from the receiver developed.
Also as shown in Figure 7 after the energy
absorbed (purple line) crosses radiation
loss (green line) and conduction and
convection loss (red line), the difference
between the energy captured and energy
lost increases gradually. There are two
peaks shown in the Figure 7.The smaller
peak during the time period from 12:45 to
14:00 is the indication of Solar Noon at the
location which is also observed from
Figure 3 with peak Irradiance value. The
larger peak during the time period from
14:15 to 16:15 indicates maximum
absorbed energy into the system, which
may be an expectedbehaviour as a
combined effect of irradiance value and
lower convection loss caused by higher
ambient temperature during that period.
From these two regions of peak described
above, if correlated with Figure 6 than
frequent higher volume condensate is
obtained during 14:15 to 16:15 i.e. in the
larger peak region.
Table 2 indicates the hat balance sheet of
the experimentation conducted during the
month of April 2018. It is evident from the
table that energy accumulated in the
receiver developed is higher than the
energy transferred to the working fluid
(water in our case). This observation can
be explained by saying that thermal
resistance of water-aluminium interface is
higher than the thermal resistance inside
the receiver wall. Secondly, it is found that
energy lost to the atmosphere via
conduction and convection loss from the
receiver is slightly higher than the energy
transferred to water through the receiver
wall.
Figure 7 and Table 2 indicate a similar
phenomenon of dominance of radiation
loss over the conduction and convection
loss which occur due to higher surface
temperature of the receiver. In order to
increase the capturing efficiency of the
Scheffler dish solar collector it is essential
to reduce the radiation and conduction-
convection loss from the receiver surface.
Also it is essential to work in the direction
to reduce the thermal resistance at the
water-aluminium interface which helps to
increase the transfer of absorbed solar
energy to heat water and produce higher
amount of steam for different process
applications like cooling, heating, drying
etc. After calculating the energy absorbed
and lost, when the total energy value was
compared with the value available
instandard literature some gap was found.
After reviewing the experimentation and
observing the system components, the
authorbelieves that the unaccounted loss of
energy might be due to slight error in
tracking mechanism, loss due to
inaccuracy in focus, fine dust
accumulation and degradation in the
optical properties of the mirror.
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Page 44-52 © MAT Journals 2018. All Rights Reserved
Journal of Thermal Energy Systems
Volume 3 Issue 3
Fig:7.Captured energy and loss of energy Vs time of the day
Table:2.Heat balance sheet from experimental analysis
Particulars
kwh/day
kcal/day
%
Particulars
kwh/day
kcal/day
%
A] Total or gross
heat supplied
20.42
17562
100
B] Heat expenditures
a) Heat energy absorbed
9.00
7740
44
b)Conduction and
convection loss
3.19
2746
16
c) Radiation loss
4.13
3552
20
d) Unaccounted loss
4.10
3524
20
Balance
20.42
17562
100
20.42
17562
100
CONCLUSION
The development of receiver for Scheffler
dish solar collector is a successful attempt
in achieving the required temperature for
many residential and industrial
applications (cooling, heating, drying).
Also it is evident that the method used
hereis successful in creating heat balance
sheet which can be of use to many
researchers interested in working with
Scheffler dish solar collector. Figures5, 6,
7 and Table 2 can be used as work for
future research in the direction of
increasing the collection efficiency of
thesystem. Also modelling the process of
boiling and condensation using this work
can be useful in the field of water
desalination technology which is the need
of today‟s world.
ACKNOWLEDGEMENT
Authors would like to express their
gratitude to Royal Academy of
Engineering (RAE), Parul University
(PU), Larsen & Toubro(L&T) and
University of Surrey as this research paper
is out of research work carried out as part
of Industry Defined Research Project
entitled „Green Refrigeration Systems
Using Solar Energy‟ funded by Royal
Academy of Engineering, UK under
Newton Bhabha Fund under the Higher
Education Partnership – India
Program.They are also thankful to
Munisevashram for helping in conducting
the experiments in their premise.
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Cite this article as:
Arjun Vyas, Dhaval Sodha, Jaydeep
Chanani, Jaydip Fataniya,, Parth Patel,
Dhruv Patel, & Deepjyoti Basak. (2018).
Estimation of Captured Energy Using Novel
Receiver for Scheffler Dish Solar Collector.
Journal of Thermal Energy Systems, 3(3),
44–52.
http://doi.org/10.5281/zenodo.1988961
