Volume 3, Issue 11, November – 2018 International Journal of Innovative Science and Research Technology

ISSN No:-2456-2165

Enhancement of Optical Performance of a Three

Dimensional Compound Parabolic Concentrator
S.Senthilkumar P.Seethalakshmi R.Amsaveni
Head of the Department Selection Grade Lecturer, Lecturer
Department of Basic Sciences Department of Basic Sciences, Department of General Engineering
Kongu Polytechnic College Kongu Polytechnic College, Nachimuthu Polytechnic College
Perundurai, Erode - 638 060, India Perundurai, Erode - 638 060, India Pollachi, - 642003, India

Abstract:- A three Dimensional Compound Parabolic work out the optical efficiency of the novel Elliptical–
Concentrator (3-D CPC) has been developed to collect Hyperboloid Concentrators (EHC) [7]. An optical efficiency
solar energy and to achieve the highest possible of 63% has been established for a 2-D model of the EHC
concentration. The significant research work describes with the dimensions as followed: aperture length 1m, height
the methodology to bring out the performance of 3-D 0.85 m, receiver diameter 0.182 m and concentration ratio
CPC reflector profile that is designed and fabricated for of 8X. The reflectivity of EHC has been considered as 0.94.
a half acceptance angle of 4º in support of a spherical As a result of the three-dimensional nature of EHC, the
absorber with radius 100 mm. In the present work, two optical efficiency has been enhanced to 78% based on 3-D
types of absorber coating materials are used in 3-D CPC ray trace geometry. The limitation placed on 2D indicates
modules, one with a commercially available ordinary that the CPC has to include rays in the output whose angle
Black paint (3-D CPC IA) and another with a Black- exceed the critical angle that are causing waste of
Nickel-Tin (3-D CPC IB). The optical efficiencies of 3-D concentration [8]. This waste concentration can be regained
CPCs have been projected hypothetically and by the use of 3D structures which are practically necessary.
comparisons have made among the experimental values. Through the proper assembling of the 3-D CPCs, the
The study examines the values of optical efficiencies that minimal diffused element that present can be captured [9].
are experimentally determined are in good agreement A new methodology (approximate development method)
with the values that are predicted theoretically. Optical has been used to design 3-D CPC [10].
performance of 3-D CPC IB has been enhanced by
selective coating to the absorber. II. EXPERIMENTAL PROCEDURE

Keywords:- 3-D CPC; Optical Efficiency; Black Nickel– In the present work, two types of absorber coating
Tin; Solar Energy. materials have been used to the absorbers in the 3-D CPC
modules fabricated for half-acceptance angle of 4º to
I. INTRODUCTION achieve higher concentration ratio by approximate
development method. Figure.1 shows the experimental set-
Focusing collector is a tool to gather solar energy by up of 3-D CPC modules. The absorber is a spherical ball
means of high intensity of solar radiation on the energy with 200 mm outer diameter and 197 mm inner diameter. To
absorbing surface. Such collectors usually employ optical enhance the optical performance of the 3-D CPC modules,
system in the form of reflectors or refractors. Focusing one of the absorber is coated with a commercially available
collectors like Compound Parabolic Concentrators (CPC) ordinary Black paint (3-D CPC IA) and another absorber
are most common for applications with medium coated with Black Nickel-Tin (3-D CPC IB). The absorber
temperature. In 1974, CPC was first designed and for 3-D CPC IA is coated with dull black paint having
determined by Winston [1]. The design and constructional absorptivity (α) 0.90 and 3-D CPC IB is coated with Black
details are reported in [2, 3]. The most important benefit Nickel –Tin having absorptivity (α) 0.92. In the study of the
of 2-D CPC is, they can receive radiation reaching the 3-D CPCs, water is used as a heat transfer fluid. The
destination with large angular spread and so far concentrate temperatures have been measured by using Resistance
it on to linear receivers of small transverse width. The end Temperature Detector (RTD) in which the RTD (PT100)
result of mirror errors and receiver misalignments of 2-D measures the temperature in the range of - 50 to 100˚C. The
CPC were explained [4]. The varieties of 2-D CPCs inlet, outlet and atmospheric temperatures were calculated
expressed their greater part in terms of general using RTDs. This kind of concentrator operates simply on
characteristics, namely concentration, acceptance angle, the beam component of solar radiation despite the fact that
sensitivity to mirror errors, size of the reflector area and beam radiation has been calculated by means of a
average number of reflections were compared [5], moreover pyrheliometer. The flow rate of the fluid has been measured
generate an easy analytical technique to work out the by using a graduated jar and a stopwatch. A stable head tank
average number of reflections that make use of calculating has been employed by an online heater to endow with
optical losses for 2-D CPC. The feasible extensions of 2-D various inlet temperatures to provide a constant flow of
CPC to 3-D CPC were described and indicated that 3-D water. Moreover a wind velocity meter has been used to find
CPC propose a high concentration more than 2-D CPC [6]. the wind velocity.
A wide-ranging theoretical estimation of 2-D and 3-D ray
tracing techniques has been taken in the recent study to

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Volume 3, Issue 11, November – 2018 International Journal of Innovative Science and Research Technology
ISSN No:-2456-2165

Estimated
Absorber Expression
Module optical
coating for 
efficiency
Black
3-D CPC IA* m<n>  0.716
paint
Black
3-D CPC IA# a m<n>  0.645
paint
Black
3-D CPC IB * Nickel - m<n>  0.732
Tin
Black
3-D CPC IB # Nickel - a m<n>  0.659
Tin
Table 1:- Theoretical estimation of optical efficiency ()
Fig 1:- Experimental Set-Up
* Without glass cover, # with glass cover
III. THEORETICAL ESTIMATION OF OPTICAL
IV. EXPERIMENTAL DETERMINATION OF
EFFICIENCY OF 3-D CPCs
OPTICAL EFFICIENCY
The optical efficiency of 3-D CPC with top glass
The collector has been incorporated with water as heat
cover and glass envelope around the absorber [11] is given
transfer medium in the fluid loop. The open loop operation
as,
that has been established was more convenient since it was
 = a e m<n>   fref (1) effortless to uphold stable conditions and elevated flow
rates for longer periods. The flow rate was set aside
Where, a is the transmittance of the aperture cover; e sufficiently large and stable such that 0  (Tav – Ta)  1º,
is the transmittance of the glass envelope around the where Tav is the average of inlet and outlet water
absorber; m is the reflectance of the reflector material; temperatures and Ta is the ambient temperature. The inlet,
<n> is the average number of reflections;  is the outlet and atmospheric temperatures have been measured
absorptance of the material coated on the absorber; P is the using RTD’s and the beam radiation has been calculated
optical loss due to the gap width and fref is the multiple using pyrheliometer. The observation has been taken from
reflections between the absorber tube and glass envelope. 9.00 am to 4.00 pm on several clear sunny days, at
The average number of reflections was 1.4 for a half 2 minutes interval. For every different configuration of
acceptance angle 4º [12]. To avoid conduction losses 3-D CPC modules steady state conditions has been
between the absorber and reflector, the cusp is removed and obtained for 5 to 10 minutes around noon time on several
made flat. In view of the fact that, the receiver thermal days. The optical efficiency has been computed from the
losses of 3-D CPC are primarily radiative and the absorber observed data [14, 15]. Based on this, the optical efficiency
area is undersized, the convection suppressing cover is not was computed as,
essential for 3-D CPC modules [13]. The top view of 3-D η0 = m° CW (To - Ti) / Ib A (2)
CPC IA is shown in Figure.2. Necessary modifications in
the expression (Eq.1) for  were made for various CPC Where, m° is the mass flow rate of fluid; CW is the
modules and are presented in Table 1 along with the specific heat capacity of water; T o is the outlet temperature;
estimated values of optical efficiencies. Ti is the inlet temperature; A is the aperture area and I b is
direct (beam) component of solar irradiance. The
experiments were carried out on a number of clear sunny
days. The sample readings taken during steady state
conditions for 3-D CPC IA and 3-D CPC IB have been
presented in Table.2 and Table.3. The experimentally
determined optical efficiencies of various CPCs have been
shown in Table 4.

S.NO TA TI TO M° IB 
(°C ) (°C )(°C ) ( KG/S) (WM-2)
1. 30.5 29.1 32.8 6.666E-03 710 0.630
2. 31.3 30.3 33.9 6.666E-03 725 0.613
3. 31.4 30.2 34.0 7.142E-03 790 0.647
4. 32.5 31.1 34.7 7.142E-03 775 0.613
5. 32.2 31.2 34.9 6.666E-03 710 0.630
Fig 2:- Top view of 3-D CPC IA mean 0.626
Table 2:- Experimental investigation of optical efficiency
of 3-D CPC IA

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Volume 3, Issue 11, November – 2018 International Journal of Innovative Science and Research Technology
ISSN No:-2456-2165
S.NO TA TI TO M° IB  [8]. W T Welford, R.W., High Collection Non-Imaging
(°C ) (°C ) (°C ) ( KG/S) (WM-2) Optics, Academic Press, New York and London, 1989.
1. 31.5 30.2 34.2 5.932E-03 690 0.636 [9]. Garry Zamani Naman, N.SellamiS, N.Sarmah2, A.
2. 31.8 30.5 34.5 6.672E-03 770 0.641 Ivaturi, S. Senthilarasu, P.R.Bobbili, H.M.Upadhyaya,
3. 32.0 30.8 34.9 6.672E-03 780 0.649 T. K. Mallick, ”Compound Parabolic Concentrators
Designs for Equatorial Africa for the 1 st
4. 32.3 31.0 35.2 5.932E-03 730 0.632
AfricaPVSEC – Durban 2014.
5. 32.5 31.2 35.5 5.965E-03 750 0.633
[10]. Senthilkumar S, Perumal K, and Srinivasan PSS,
Mean 0.638 “Optical and Thermal Performance of a three-
Table 3:- Experimental investigation of optical efficiency dimensional compound parabolic concentrator for
of 3-D CPC IB spherical absorber”, Sadhana,Vol, 34, Part 3, pp.
369-380, 2009
V. SUMMARY AND CONCLUSIONS [11]. Rachel Oommen., and Jayaraman S.,“Development
and Performance Analysis of Compound Parabolic
From Table 4, the theoretically estimated optical Solar Concentrators with Reduced Gap Losses -‘V’
efficiency values are in good agreement with experimental Groove Reflector”, Renewable Energy, vol. 27,
optical efficiency values. It clearly shows that, the pp.259-275, 2002.
experimentally determined optical efficiency values of 3-D [12]. Winston, R., and Hinterberger, H., “Principles of
CPCs are higher than the 2-D CPC values that are reported Cylindrical Concentrators for Solar Energy”, Solar
earlier. Further, the optical efficiency values of 3-D CPC IB Energy. Vol. 17, pp. 255-258, 1975.
are higher than that of 3-D CPC IA and 2-D CPC due to the [13]. Magal,B.S., Solar Power Engineering, Tata Mc Graw-
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the enhancement of thermal performance of 3-D CPC IB “The Stretched Membrane Design of a Compound
which in turn enhances the overall efficiency of the Parabolic Trough Collector”, 'Renewable Energy for
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and Bansal, Tata McGraw Hill Publishing Co. Ltd.,
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[15]. Rabl, A., Gallagher, J.O., and Winston, R., “Design
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[16]. K.Perumal, "Development of Compound Parabolic
Solar Concentrators in India using Aluminised
Polyester Foil and Acrylic Sheet", Ph.D. Thesis,
Bharathiar University, Tamilnadu, India, 1990.
Table 4:- Optical efficiencies of various CPCs [17]. Rachel Oommen,“Development of Compound
*Black paint, #Black Nickel – Tin, $ NALSUN Parabolic Solar Concentrator with Reduced Gap
Losses- Application to Steam Generation”, Ph.D.
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