- Email: [email protected]
Performance of PVT solar collector with compound parabolic concentrator and phase change materials
Accepted Manuscript Title: Performance of PVT Solar Collector with Compound Parabolic Concentrator and Phase Change Materials Author: M.F.I. Al-Imam R.A. Beg M.S. Rahman M.Z.H. Khan PII: DOI: Reference:
S0378-7788(15)30473-4 http://dx.doi.org/doi:10.1016/j.enbuild.2015.12.038 ENB 6356
To appear in:
ENB
Received date: Revised date: Accepted date:
6-11-2015 18-12-2015 21-12-2015
Please cite this article as: M.F.I. Al-Imam, R.A. Beg, M.S. Rahman, M.Z.H. Khan, Performance of PVT Solar Collector with Compound Parabolic Concentrator and Phase Change Materials, Energy and Buildings (2015), http://dx.doi.org/10.1016/j.enbuild.2015.12.038 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Performance of PVT Solar Collector with Compound Parabolic Concentrator and Phase Change Materials
Department of Mechanical Engineering, Rajshahi University of Engineering and Technology, Rajshahi, Bangladesh. 2
Department of Glass and Ceramic Engineering, Rajshahi University of Engineering and
3
us
Technology, Rajshahi, Bangladesh.
cr
1
ip t
M. F. I. Al-Imam1*, R. A. Beg1, M. S. Rahman2, M. Z. H. Khan3*
Department of Chemical Engineering, Jessore University of Science and Technology, Jessore 7408, Bangladesh. *
an
Corresponding authors email: [email protected], [email protected]
M
Abstract
In this study we examine the solar radiation conversion into thermal energy and energy storage
d
into phase change material (PCM) in the photovoltaic thermal (PVT) collector system. In order
te
to get better solar radiation satisfactory compound parabolic concentrator (CPC) has been mounted on PVT collector. In this study outdoor experiments were carried out to compare
Ac ce p
performance study between clear day and semi-cloudy day in winter season. PVT solar collector with CPC that act as a solar collector, a PCM tank and CPC was integrated into one piece because of simplicity structure for PCM storage in same unit. No connection pipe i,e small area needed for installation and continuous tracking was not needed for better concentration ratio. Total heat loss, total useful energy, thermal efficiency and overall efficiency of the collector by varying different parameters were evaluated using modified equations derived for the energy storage system from the basic derivation of Hottel-Bliss-Whillier. The results shows that thermal efficiency of solar collector varies from 40%-50% for clear day and around 40% for semicloudy day. The overall efficiency of the PVT collector between 55%-63% for clear-day and around 46%-55% for semi-cloudy day whereas corresponding top loss value around 3 W/m2k for clear day and around 2.5W/m2k for semi-cloudy day. Up to around 3m from entrance, the plate
1 Page 1 of 24
temperature was increased and then it became nearly steady. But in case of applying same system without PCM temperature was increased sharply.
cr
ip t
Keywords: Solar energy, thermal efficiency, thermal model, compound parabolic concentrator.
us
1. Introduction
Solar energy could be one of primary source of renewable energy that has environmental advantages compared with conventional energy sources. Its main advantage it is ecologically
an
clean and does not produce any waste products or polluting air which provides human activity for sustainable development [1-7]. Conversion of solar energy systems may be classified into
M
two systems such as thermal energy system and electrical energy system. These two collection systems can be combined to form photovoltaic-thermal systems. For betterment efficiency of electrical conversion of photovoltaic modules which needed heat accumulated in the solar cells
d
system is recovered in the form of low-temperature thermal energy [2]. Some of last few years,
te
air and water depend heat carrying fluids have been studied, for different Photovoltaic-Thermal (PVT) systems which developed, and reported in literature. As an example, a hybrid PVT solar
Ac ce p
system studied and produced electrical power system and hot water and suitable for the various climatic conditions. [3-5] Stores or supplies heat by a PCM is a material that at its melting/solidification temperature using its high thermal energy storage system with its latent heat [4]. Using various manufacturing techniques PCM have integrated in solar heating systems such as storage water heater containing a PCM-filled layer of capsules to get hot water during semi-cloudy hours [5,6]. Concentrated solar radiation fall on the absorber plate of a solar collector by using various solar concentrators. Last decades, different PVT systems have been studied, developed, and reported in literature based on air and water as heat carrying fluids. To produce hot water and electrical power system suitable for the climatic conditions of Cyprus, Kalogirou et al. have studied a hybrid PVT solar system [7]. A wall mounted solar PVT collector system and its thermal and electrical behavior was discussed by Ji [8]. They have suggested that an increase of the mass flow rate of the 2 Page 2 of 24
working fluid was beneficial for PVT cooling. To reduce the energy consumption in buildings and to provide electrical and thermal energy for domestic users, utilization of a PVT water heating collector for walls in buildings has many advantages [9].
ip t
Different types of solar concentrators are used in last few years but use in this study a compound parabolic concentrator (CPC). Both direct and reflected solar radiation falls on the CPC were used to heat up the system of solar collector [10,11]. With regard to different parameter such as
cr
collector length, speed of wind, air mass flow rate in which thermal behavior of the solar air heater was analyzed [12-18]. Photovoltaic-thermal collector system is suitable for better
us
utilization of space, savings when supporting construction and conversion together with electrical and thermal energy. It may be used electrical energy generation and hot water for
an
private house, industrial processing work.
Due to the large temperature differences high power output and high efficiencies results from
M
high-temperature energy sources [19]. Use of CPC helps solar radiation to concentrate onto the absorber plate of a thermoelectric collector. Tchinda et al. [11] have investigated theoretically a
d
solar air heater with a CPC. By using various manufacturing techniques PCM was integrated in solar heating systems. Storage water heater containing a layer of PCM-filled capsules is one the
te
techniques used to get hot water during off-sunshine hours [20]. Double rectangular enclosure
23].
Ac ce p
with the top enclosure filled with paraffin wax was also used as a system in previous study [21-
The aim of this work is to characterize and analyze the thermal performance of a PVT solar collector by using CPC and phase change materials. Furthermore, the overall efficiency of the PVT collector was examined.
3 Page 3 of 24
Nomenclatures
Ac ce p
te
Greek Symbols η0 Optical efficiency
d
M
an
us
cr
ip t
Apv Area of photovoltaic plate (m2) hp-c Convection coefficient pipe and cover (W/m2K) hr,p- c Radiation coefficient (W/m2K) hw Wind convection coefficient (W/m2K) hr,c-s Radiation coefficient cover and sky (W/m2K). H Total solar radiation on collector (W/m2). q Energy on photovoltaic (W) Q Useful energy (W) R1 Thermal resistance between plate and PCM (m2k/W). R2 Thermal resistance of back insulation (m2k/W). R3 Thermal resistance back of collector and ambient (m2k/W). R4 Thermal resistance between plate and glass cover (m2k/W). R5 Thermal resistance between glass and ambient (m2k/W). R6 Thermal resistance side of collector and ambient (m2k/W). S Net energy absorbed by collector (W/m2). Ta Ambient temperature (k). Tc Temperature of glass cover (k) Tp Plate surface temperature(k) Tb Temperature of bottom of collector (k) Ut Top heat loss coefficient(W/m2K), X Insulation thickness(m)
2. Experimental work and procedure 2.1 Materials
Corkwood was used to insulate for maximize heat retention and thermocouples for temperature measured. 2.54 cm diameter copper pipe and 0.6 mm plate was used to construct the collector with center to center distance 7.55 cm. PCM was filled into collector from its lateral side through perfect inlet allowing the PCM to be in contract with absorber plate. Solar collector tilted at angle of 35° to the south-directed collector was mounted at the roof top of the Metrology lab.
4 Page 4 of 24
Reflector wall was parabolic in shape and surface of the wall was made of glass as shown in Figure 1.
ip t
2.2 Description of the PVT design
The collector was made with a back layer of paraffin PCM to act as a thermal storage media.
cr
With a thin layer of PCM under the absorber plate, during sunshine hours some heat will be stored within the PCM. Melting point of used PCM was 56 °C & Latent heat of fusion is 256
us
kJ/kg. The temperature of the inlet outlet water, the temperature of the absorber plate is measured by thermocouples. The water flow rate through the test 0.2 kg/s from a constant level
an
water tank. The water source and the inlet to the collector to maintain the flow rate of water to the system by a ball valve. The solar collector with CPC consists of a single glass cover, a
M
concentrating reflector and an absorber plate. In this case of CPC, the angle θc based on the position of the sun corresponding to the earth rotation. For a CPC having tilted from the horizontal and its axis in north-south direction such that the plane of the sun’s position is normal
d
to the absorber plate, the acceptance angle is depend on sunshine collection required for a range
te
of time. The maximum concentration ratio was 1.82 with a reflector distance 1.66m and height of the CPC of 1.89m as shown in Figure 2. Directed and reflected incident solar radiation fall on
Ac ce p
the CPC to heat up the collector system. This location was considered perfect for the geographical location of Rajshahi, Bangladesh. Experimentation started at 11am and ended at 4pm and was performed during Dec-Feb’2014.
2.3 Mathematical analysis
Performance of the system is evaluated by calculating the various performance factor of the collector, which include; Top loss coefficient, Total useful energy, Useful energy of water, thermal Efficiency, photovoltaic Efficiency, temperature variation of wax, plate and PCM. Apply implement above this measurement for a solar collector system which use the basic equation of Hottel-Bliss-Whillier with some modification. It was possible to improvement of overall loss coefficient for a solar collector to modify by the mathematical equation. In this study thermal 5 Page 5 of 24
network for single glass cover system Figure 3. At some typical location on the solar collector plate where temperature Tp, solar energy of amount S is absorbed by the plate. This solar energy S was distributed to loss through the top, bottom and edges and to useful energy gain of the
ip t
system. Overall loss coefficient from the collector system may be given by: UL=Ut+Ub+Ue
(i)
cr
Energy loss through the bottom of the collector is represented by three series resistor. R2 represents the resistance to heat flow through the insulation and R3 represents the convection and
us
radiation resistance to the environment. For better insulation R3 value was zero. In a welldesigned system the edge loss may be small so that it is not necessary to predict it with great
an
accuracy [12]. Back loss coefficient of the system is express by: Ub=Ue =K/x
(ii)
M
The loss coefficient for the top surface is the result of convection and radiation between parallel plates. The energy transfer between the plate at Tp and the glass cover is depending on the energy
d
loss to the surroundings from the cover glass [12]. Top loss coefficient is calculated from: (iii)
te
Ut=[1/(hp-c +hr,p- c) +1/(hw+hr,c-s)]-1
The useful energy gain of the system is the sum of PCM is used to heat and water carried heat
Ac ce p
from the system. Total useful energy of the system is given by: Qu=ApFR[S-UL(Ti-Ta)]
(iv)
And the useful energy of water denoted by the equation by: Qw =mcp(T0-Ti)
(v)
Thermal efficiency of this system is express by: ηt=Qu/HAp η0CR
(vi)
Photovoltaic efficiency is calculated from: η=P/qApv
(vii)
6 Page 6 of 24
3. Results and Discussion For evaluating thermal performance of PVT solar collectors, top heat loss coefficient is required. The thermal performance evaluation of flat plate collectors, and the design, simulation of heat
ip t
losses depends on the correct value of Ut with vertical configuration. Different variables like Top heat loss coefficient, Ut, has to be computed for various values of different variables like ambient temperature (Ta), wind heat transfer coefficient (hw), absorber plate temperature (Tp), angle of
cr
inclination of collector (β), and air gap spacing between absorber plate and glass cover (L).
us
Numerical solutions of empirical equations have been used for computing top heat loss coefficient of a flat plate collector [24-29].
an
Several tests on the solar collector are performed during some days in December, January & February. Clear and semi-cloudy day of those month results on PVT solar collector system are presented in Figure 4 and Figure 5, respectively. Total loss coefficient shows comparable values for the clear day and semi-
M
cloudy day in December, January and February. Graph show slightly larger value for clear day such value may be explained by the higher plate temperature for clear day compare to semi cloudy day. It is observed that increase of top loss & total loss was sharply up to 1pm due to plate temperature increase but it
d
became slight slower after the next point. This graph also shows that total heat loss coefficient varying
te
from 3.5 to 4.5 W/m2K for clear day but total loss coefficient was near to equal for semi cloudy day because of the plate temperature variation with time. The friction and heat transfer coefficient for a flat
Ac ce p
plate can be determined by solving the conservation of mass, momentum, and energy equations (either approximately or numerically). The convection heat transfer coefficient, in general, varies along the flow direction. The mean or average convection heat transfer coefficient for a surface is determined by(properly) averaging the local heat transfer coefficient over the entire surface. (Figure 4 and 5)
Kostic et al. [30] had studied the influence of reflectance from the flat plate solar radiation concentrators by using water as the energy carrier on energy efficiency of PVT collector. A new design for a double pass PVT air collector was developed and illustrated by Othaman et al. [31, 32] with CPC and reported that the thermal and electrical output of the PVT system increases with increase in air mass flow rate. To achieve a significant efficiency enhancement of the PVT collector, they mentioned the utility of fins as an integral part of absorber plate which showed a good agreement between theoretical and experimental results. Matrawy et al. have used metal slats between the absorber plate and bottom plate of a solar air
7 Page 7 of 24
heater and reported an enhanced efficiency of a solar collector [33]. Several researchers reported about the scope for performance improvement by heat extraction in the absorber plate with fins [32-36]. In Figure 6, the curve shows average total loss coefficient increases with average plate temperature because high temperature indicates more loss for collector. Average plate temperature was around 87°C
ip t
on clear days and 70°C on semi cloudy days. The solar radiation absorbed by the absorber plate increases the temperature of the system. During low and off-sunshine hours, part of thermal energy is transferred to
cr
the circulating water as observed during experiments. The heat is transfer from liquid PCM to the circulating water until the PCM solidifies. To dampen the rate at which various temperatures in the
us
system change usually PCM employed in a flat plate collector as described by other researchers and thus the system can be dealt with steady-state condition [37-42]. The solar energy stored in a salt-hydrate PCM held in the collector could be discharged to cold water flowing through a surface heat exchanger located
an
in a layer of stationary heat transfer liquid floating over an immiscible layer of PCM.
M
(Figure 6)
The plate temperature was found to increase up to a distance of around 3m from water entrance, after
d
which an almost steady temperature was noticed because of using PCM and proper distribution of
te
temperature was noticed as shown in Figure 7. In this graph at 1pm, presentation line indicates high plate temperature compare to with other two lines because the solar radiation absorbed by the absorber plate
Ac ce p
increases the temperature of the system. But the plate temperature increasing trend with distance from entrance obtained for a similar system without the PCM in back layer. In a semi-cloudy day, plate temperature of the system was almost same as shown in Figure 8 at all three times during due to fluctuation of solar radiation.
(Figure 7 and 8)
Total useful energy is the sum of heat carried by water and heat transfer to PCM. At low sunshine hour around after 3pm useful energy of water line above the total useful energy line indicate part of thermal energy was transfer to the circulating water as shown in Figure 9. Total useful energy and useful energy 8 Page 8 of 24
of water slightly increase up to 2pm after that useful energy is decrease up to next point. Lastly useful energy of water increase indicates direction of heat flow from the PCM to water. Thermal efficiency was measured by the useful energy gain of the system divided by the total solar radiation incident on the collector. Thermal efficiency of the collector, was from around 40% - 50% for those three months as
ip t
shown in Figure 10. A decrease trend of thermal efficiency with time was performing for clear day, which directly related to the increase trend of the overall loss coefficient with time. Efficiency through the semi-cloudy day of those months seems nearly constant value and this result effect nearly steady change
an
(Figure 9 and 10)
us
cr
of top or total loss coefficient with time.
Photovoltaic-thermal efficiency indicates total efficiency of the collector (sum of thermal efficiency and
M
PV efficiency). Total efficiency decrease with time and total efficiency varies from 55%-63% which was 40%-50% for thermal application. Total efficiency nearly steady with time in semi cloudy day and this
te
d
result varies from 46%-55% as shown in Figure 11.
Ac ce p
(Figure 11)
The increasing trend of the top loss coefficient with time shows a slightly decreasing trend for the clear days of January and February. On the other hand the efficiency after mid-day seems almost constant for the clear and semi cloudy days and reflects the nearly steady change of top loss coefficient with time. Marginal variations can be seen for the thermal efficiency of the three months, which shows fluctuations in the climatic conditions with to a conventional. However, employment of PCM as a storage media and the combination of collector and storage in one unit is more useful for a solar system as observed through the study and also by other previous reports [37-42].
9 Page 9 of 24
4. Conclusion The following findings have been drawn from the experimental investigations on the PVT solar collector with CPC. Convection and radiation loss between plate, glass and surrounding was maximum indicate
ip t
highest top loss which value around 3 W/m2K for clear day and around 2.5 W/m2K for semi-cloudy day. Thermal efficiency of solar collector varies from 40%-50% for clear day and around 40% for semi-cloudy day, which value around 35% for locally made flat plate collector. Overall efficiency of the PVT solar
cr
collector was between 55%-63% for clear day and around 46%-55% for semi-cloudy day. The plate temperature gradually increase up to 3 m from water entrance to the solar collector, after which absorber
us
plate temperature value all most same was indicate but increasing trend up to total length of the pipe. These values obtained from without PCM collector system. Useful energy of water temperature was
an
found to be higher compare with useful energy indicating the storage capacity of the PCM.
[1]
M
References
S.A. Kalogirou, Y. Tripanagnostopoulos, Hybrid PV/T solar systems for domestic hot
d
water and electricity production, Energy Conversion and Management 47 (18) (2006) 3368-
[2]
te
3382.
I. Dincer, Evaluation and selection of energy storage systems for solar thermal
[3]
Ac ce p
applications, International Journal of Energy Research 23 (12) (1999) 1017–1028. J. Prakash, H.P. Garg, G. Datta, A solar water heater with built-in latent heat storage,
Energy Conversion and Management 25 (1) (1985) 51–56. [4]
K.S. Reddy, Thermal modeling of PCM-based solar integrated collector storage water
heating system, ASME Transactions – Solar Energy Engineering 129 (4) (2007) 458–464. [5]
Z. Chen, M. Gu, D. Peng, Heat transfer performance analysis of a solar flat-plate
collector with an integrated metal foam porous structure filled with paraffin, Applied Thermal Engineering 30 (14-15) (2010) 1967–1973. [6]
H.E. Qarnia, Numerical analysis of a coupled solar collector latent heat storage unit using
various phase change materials for heating the water, Energy Conversion and Management 50 (2) (2009) 247–254. [7]
S.A. Kalogirou, Y. Tripanagnostopoulos, Energy Convers. Manage. 47 (2006) 3368.
[8]
J. Ji, J. Hun, T.T. Chow, H. Yi, J. Lu, W. He, W. Sun, Energy Build. 38 (2006) 1380. 10 Page 10 of 24
[9]
S. Dubey, S.C. Solanki, A. Tiwari, Energy Build. 41 (2009) 863.
[10]
J.A. Duffie, W.A. Beckman, Solar Engineering of Thermal Processes, 3rd ed., Wiley,
Hoboken, NJ. 2006. [11]
R. Tchinda, Thermal behaviour of solar air heater with compound parabolic concentrator,
[12]
ip t
Energy Conversion and Management 49 (2008) 529-540.
N.K. Bansal, D. Buddhi, Performance equations of a collector cum storage system using
[13]
cr
phase change materials, Solar Energy 48 (3) (1992) 185–194.
Y. Rabin, I. Bar-Niv, E. Korin, B. Mikic, Integrated solar collector storage system based
[14]
us
on a salt-hydrate phase-change material, Solar Energy 55 (6) (1995) 435–444.
A.D. Gracia, E. Oró, M.M. Farid, L.F. Cabeza, Thermal analysis of including phase
an
change material in a domestic hot water cylinder, Applied Thermal Engineering 31 (17-18) (2011) 3938–3945. [15]
L.F. Cabeza, H. Mehling, S. Hiebler, F. Ziegler, Heat transfer enhancement in water
M
when used as PCM in thermal energy storage, Applied Thermal Engineering 22 (10) (2002) 1141–1151.
T.J.N. Schoen, Building-integrated PV installations in The Netherlands: Examples and
d
[16]
operational experiences, Solar Energy 70 (6) (2001) 467. J. Ji, J. Hun, T.T. Chow, H. Yi, J. Lu, W. He, W. Sun, Effect of fluid flow and packing
te
[17]
Ac ce p
factor on energy performance of a wall-mounted hybrid photovoltaic/water-heating collector system, Energy and Buildings 38 (12) (2006) 1380-1387. [18]
S. Dubey, S.C. Solanki, A. Tiwari, Energy and exergy analysis of PV/T air collectors
connected in series, Energy and Buildings 41 (8) (2009) 863-870. [19]
J. Chen, S. Lue, B. Liao, J. Energy Res. Technol. 127 (37) (2005).
[20]
J. Prakash, H.P. Garg, G. Datta, A solar water heater with a built-in latent heat storage,
Energy Conversion and Management 25 (1985) 51–56. [21]
K.S. Reddy, Thermal modeling of PCM-based solar integrated collector storage water
heating system, ASME Transactions – Solar Energy Engineering 129 (2007) 458–464. [22]
H. El Qarnia, Numerical analysis of a coupled solar collector latent heat storage unit
using various phase change materials for heating the water, Energy Conversion and Management 50 (2009) 247–254.
11 Page 11 of 24
[23]
I. Al-Hinti, A. Al-Ghandoor, A. Maaly, I. Abu Naqeera, Z. Al-Khateeb, O. Al- Sheikh,
Experimental investigation on the use of water-phase change material storage in conventional solar water heating systems, Energy Conversion and Management 51 (2010) 1735–1740. [24]
H.C. Hottel, B.B. Woretz, The performance of flat plate solar heat collectors, Trans
[25]
ip t
ASME 64 (1942) 94–102.
S.A. Klein, Calculation of flat-plate collector loss coefficients, Solar Energy 17 (1975)
[26]
cr
79–80.
J.A. Duffie, W.A. Beckman, Solar engineering of thermal processes, 2nd ed. New York:
[27]
us
Wiley, 1991.
V.K. Agarwal, D.C. Larson, Calculation of top heat loss coefficient of a flat-plate solar
[28]
an
collector, Solar Energy 27 (1981) 69–71.
A. Malhotra, H.P. Garg, A. Patil, Heat loss calculation of flat-plate solar collectors, J
Therm Eng (J Ind Soc Mech Eng) 2 (1981) 59–62.
V. Badescu, Optimal control of flow in solar collector systems with fully mixed water
M
[29]
storage tanks, Energy Convers Manage 49 (2008) 169–84. L.T. Kostic, Tomislav, T.M. Pavlovic, T. Zoran, Z.T. Pavlovic, Influence of reflectance
d
[30]
from flat aluminum concentrators on energy efficiency of PV/Thermal collector, Appl Energy 87 M.Y. Othman, Baharudin, B.Y.K Sopian, M.N. Abu Bakar, Performance analysis of a
te
[31]
Ac ce p
double-pass photovoltaic/thermal (PV/T) solar collector with CPC and fins, Renewable Energy 30 (2005) 2005–2017. [32]
M.Y. Othman, B.Y.K. Sopian, M.N. Abu Bakar, Performance studies on a finned double-
pass photovoltaic-thermal (PV/T) solar collector, Desalination 209 (2007) 43–49. [33]
P.G. Charalambous, G.G. Maidment, S.A. Kalogirou, K. Yiakoumetti, Photovoltaic
thermal (PV/T) collectors: A review, Appl Therm Eng. 27 (2007) 275–286. [34]
J.K. Tonui, Y. Tripanagnostopoulos, Air-cooled PV/T solar collectors with low cost
performance improvements, Solar Energy 81 (2007) 498–511. [35]
K.K. Matrawy, Theoretical analysis for an air heater with a box type absorber, Solar
Energy 63 (1998) 191–198. [36]
C.D. Ho, H.M. Yeh, T.W. Cheng, T.C. Chen, R.C. Wang, The influence of recycle on
performance of double pass flat solar air heaters with internal fins attached, Appl Energy 86 (2009) 1470–1478. 12 Page 12 of 24
[37]
A. Koca, H.F. Oztop, T. Koyun, Y. Varol, Energy and exergy analysis of a latent heat
storage system with phase change material for a solar collector, Renewable Energy 33 (2008) 567–574. [38]
A.A. El-Sebaii, A.A. Al-Ghamdi, F.S. Al-Hazmi, A.S. Faidah, Thermal performance of a
[39]
ip t
single basin solar still with PCM as a storage medium, Applied Energy 86 (2009) 1187–1195. M. Mazmana, L.F. Cabeza, H. Mehling, M. Nogues, H. Evliya, H. Paksoy, Utilization of
cr
phase change materials in solar domestic hot water systems, Renewable Energy 34 (2009) 1639– 1643.
A.K. Bhargava, A solar water heater based on phase-changing material, Applied Energy
us
[40]
14 (1983) 197–209.
N.K. Bansal, D. Buddhi, Performance equations of a collector cum storage system using
an
[41]
phase change materials, Solar Energy 48 (1992) 185–194. [42]
Y. Rabin, I. Bar-Niv, E. Korin, B. Mikic, Integrated solar collector storage system based
d
M
on a salt-hydrate phase-change material, Solar Energy 55 (1995) 435– 444.
te
Highlights
Ac ce p
• We examine the solar radiation conversion into thermal energy and energy storage • Compound parabolic concentrator has been mounted on photovoltaicthermal collector • Overall efficiency of the PVT solar collector was higher • The plate temperature gradually increase from water entrance to the solar collector
13 Page 13 of 24
ip t cr us an M
Figure 1: Sectional view (top) and top view (bottom) of the PVT solar collector system with various
Ac ce p
te
d
dimensions (dimensions in m) used in this study.
14 Page 14 of 24
ip t cr us an
Ac ce p
te
d
M
Figure 2: The geometry of the investigated PVT solar collector
15 Page 15 of 24
ip t cr us an
Ac ce p
te
d
M
Figure 3: Thermal network for the PVT collector system with compound parabolic concentrator.
16 Page 16 of 24
ip t cr us an
Figure 4: Variation of total loss and top loss coefficient with time on clear day in December, January, and
Ac ce p
te
d
M
February.
17 Page 17 of 24
ip t cr us an
Figure 5: Variation of total loss and top loss coefficient with time on semi-cloudy day in December,
Ac ce p
te
d
M
January and February.
18 Page 18 of 24
ip t cr us an M
Ac ce p
te
d
Figure 6: Relation between average total loss coefficient and average plate temperature.
19 Page 19 of 24
ip t cr us an
Figure 7: Variation of plate temperature with distance from entrance on clear day in December, January
Ac ce p
te
d
M
and February.
20 Page 20 of 24
ip t cr us an
Figure 8: Variation of plate temperature with distance from entrance on semi-cloudy day in December,
Ac ce p
te
d
M
January and February.
21 Page 21 of 24
ip t cr us an M
Figure 9: Variation of solar radiation, total useful energy and useful energy of water with time in
Ac ce p
te
d
December, January and February.
22 Page 22 of 24
ip t cr us an
M
Figure 10: Compare variation of Thermal efficiency with time on clear day and semi-cloudy day in
Ac ce p
te
d
December, January and February.
23 Page 23 of 24
ip t cr us an
M
Figure 11: Photovoltaic- Thermal efficiency compare with time on clear and semi-cloudy day in
Ac ce p
te
d
December, January and February.
24 Page 24 of 24
S0378-7788(15)30473-4 http://dx.doi.org/doi:10.1016/j.enbuild.2015.12.038 ENB 6356
To appear in:
ENB
Received date: Revised date: Accepted date:
6-11-2015 18-12-2015 21-12-2015
Please cite this article as: M.F.I. Al-Imam, R.A. Beg, M.S. Rahman, M.Z.H. Khan, Performance of PVT Solar Collector with Compound Parabolic Concentrator and Phase Change Materials, Energy and Buildings (2015), http://dx.doi.org/10.1016/j.enbuild.2015.12.038 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Performance of PVT Solar Collector with Compound Parabolic Concentrator and Phase Change Materials
Department of Mechanical Engineering, Rajshahi University of Engineering and Technology, Rajshahi, Bangladesh. 2
Department of Glass and Ceramic Engineering, Rajshahi University of Engineering and
3
us
Technology, Rajshahi, Bangladesh.
cr
1
ip t
M. F. I. Al-Imam1*, R. A. Beg1, M. S. Rahman2, M. Z. H. Khan3*
Department of Chemical Engineering, Jessore University of Science and Technology, Jessore 7408, Bangladesh. *
an
Corresponding authors email: [email protected], [email protected]
M
Abstract
In this study we examine the solar radiation conversion into thermal energy and energy storage
d
into phase change material (PCM) in the photovoltaic thermal (PVT) collector system. In order
te
to get better solar radiation satisfactory compound parabolic concentrator (CPC) has been mounted on PVT collector. In this study outdoor experiments were carried out to compare
Ac ce p
performance study between clear day and semi-cloudy day in winter season. PVT solar collector with CPC that act as a solar collector, a PCM tank and CPC was integrated into one piece because of simplicity structure for PCM storage in same unit. No connection pipe i,e small area needed for installation and continuous tracking was not needed for better concentration ratio. Total heat loss, total useful energy, thermal efficiency and overall efficiency of the collector by varying different parameters were evaluated using modified equations derived for the energy storage system from the basic derivation of Hottel-Bliss-Whillier. The results shows that thermal efficiency of solar collector varies from 40%-50% for clear day and around 40% for semicloudy day. The overall efficiency of the PVT collector between 55%-63% for clear-day and around 46%-55% for semi-cloudy day whereas corresponding top loss value around 3 W/m2k for clear day and around 2.5W/m2k for semi-cloudy day. Up to around 3m from entrance, the plate
1 Page 1 of 24
temperature was increased and then it became nearly steady. But in case of applying same system without PCM temperature was increased sharply.
cr
ip t
Keywords: Solar energy, thermal efficiency, thermal model, compound parabolic concentrator.
us
1. Introduction
Solar energy could be one of primary source of renewable energy that has environmental advantages compared with conventional energy sources. Its main advantage it is ecologically
an
clean and does not produce any waste products or polluting air which provides human activity for sustainable development [1-7]. Conversion of solar energy systems may be classified into
M
two systems such as thermal energy system and electrical energy system. These two collection systems can be combined to form photovoltaic-thermal systems. For betterment efficiency of electrical conversion of photovoltaic modules which needed heat accumulated in the solar cells
d
system is recovered in the form of low-temperature thermal energy [2]. Some of last few years,
te
air and water depend heat carrying fluids have been studied, for different Photovoltaic-Thermal (PVT) systems which developed, and reported in literature. As an example, a hybrid PVT solar
Ac ce p
system studied and produced electrical power system and hot water and suitable for the various climatic conditions. [3-5] Stores or supplies heat by a PCM is a material that at its melting/solidification temperature using its high thermal energy storage system with its latent heat [4]. Using various manufacturing techniques PCM have integrated in solar heating systems such as storage water heater containing a PCM-filled layer of capsules to get hot water during semi-cloudy hours [5,6]. Concentrated solar radiation fall on the absorber plate of a solar collector by using various solar concentrators. Last decades, different PVT systems have been studied, developed, and reported in literature based on air and water as heat carrying fluids. To produce hot water and electrical power system suitable for the climatic conditions of Cyprus, Kalogirou et al. have studied a hybrid PVT solar system [7]. A wall mounted solar PVT collector system and its thermal and electrical behavior was discussed by Ji [8]. They have suggested that an increase of the mass flow rate of the 2 Page 2 of 24
working fluid was beneficial for PVT cooling. To reduce the energy consumption in buildings and to provide electrical and thermal energy for domestic users, utilization of a PVT water heating collector for walls in buildings has many advantages [9].
ip t
Different types of solar concentrators are used in last few years but use in this study a compound parabolic concentrator (CPC). Both direct and reflected solar radiation falls on the CPC were used to heat up the system of solar collector [10,11]. With regard to different parameter such as
cr
collector length, speed of wind, air mass flow rate in which thermal behavior of the solar air heater was analyzed [12-18]. Photovoltaic-thermal collector system is suitable for better
us
utilization of space, savings when supporting construction and conversion together with electrical and thermal energy. It may be used electrical energy generation and hot water for
an
private house, industrial processing work.
Due to the large temperature differences high power output and high efficiencies results from
M
high-temperature energy sources [19]. Use of CPC helps solar radiation to concentrate onto the absorber plate of a thermoelectric collector. Tchinda et al. [11] have investigated theoretically a
d
solar air heater with a CPC. By using various manufacturing techniques PCM was integrated in solar heating systems. Storage water heater containing a layer of PCM-filled capsules is one the
te
techniques used to get hot water during off-sunshine hours [20]. Double rectangular enclosure
23].
Ac ce p
with the top enclosure filled with paraffin wax was also used as a system in previous study [21-
The aim of this work is to characterize and analyze the thermal performance of a PVT solar collector by using CPC and phase change materials. Furthermore, the overall efficiency of the PVT collector was examined.
3 Page 3 of 24
Nomenclatures
Ac ce p
te
Greek Symbols η0 Optical efficiency
d
M
an
us
cr
ip t
Apv Area of photovoltaic plate (m2) hp-c Convection coefficient pipe and cover (W/m2K) hr,p- c Radiation coefficient (W/m2K) hw Wind convection coefficient (W/m2K) hr,c-s Radiation coefficient cover and sky (W/m2K). H Total solar radiation on collector (W/m2). q Energy on photovoltaic (W) Q Useful energy (W) R1 Thermal resistance between plate and PCM (m2k/W). R2 Thermal resistance of back insulation (m2k/W). R3 Thermal resistance back of collector and ambient (m2k/W). R4 Thermal resistance between plate and glass cover (m2k/W). R5 Thermal resistance between glass and ambient (m2k/W). R6 Thermal resistance side of collector and ambient (m2k/W). S Net energy absorbed by collector (W/m2). Ta Ambient temperature (k). Tc Temperature of glass cover (k) Tp Plate surface temperature(k) Tb Temperature of bottom of collector (k) Ut Top heat loss coefficient(W/m2K), X Insulation thickness(m)
2. Experimental work and procedure 2.1 Materials
Corkwood was used to insulate for maximize heat retention and thermocouples for temperature measured. 2.54 cm diameter copper pipe and 0.6 mm plate was used to construct the collector with center to center distance 7.55 cm. PCM was filled into collector from its lateral side through perfect inlet allowing the PCM to be in contract with absorber plate. Solar collector tilted at angle of 35° to the south-directed collector was mounted at the roof top of the Metrology lab.
4 Page 4 of 24
Reflector wall was parabolic in shape and surface of the wall was made of glass as shown in Figure 1.
ip t
2.2 Description of the PVT design
The collector was made with a back layer of paraffin PCM to act as a thermal storage media.
cr
With a thin layer of PCM under the absorber plate, during sunshine hours some heat will be stored within the PCM. Melting point of used PCM was 56 °C & Latent heat of fusion is 256
us
kJ/kg. The temperature of the inlet outlet water, the temperature of the absorber plate is measured by thermocouples. The water flow rate through the test 0.2 kg/s from a constant level
an
water tank. The water source and the inlet to the collector to maintain the flow rate of water to the system by a ball valve. The solar collector with CPC consists of a single glass cover, a
M
concentrating reflector and an absorber plate. In this case of CPC, the angle θc based on the position of the sun corresponding to the earth rotation. For a CPC having tilted from the horizontal and its axis in north-south direction such that the plane of the sun’s position is normal
d
to the absorber plate, the acceptance angle is depend on sunshine collection required for a range
te
of time. The maximum concentration ratio was 1.82 with a reflector distance 1.66m and height of the CPC of 1.89m as shown in Figure 2. Directed and reflected incident solar radiation fall on
Ac ce p
the CPC to heat up the collector system. This location was considered perfect for the geographical location of Rajshahi, Bangladesh. Experimentation started at 11am and ended at 4pm and was performed during Dec-Feb’2014.
2.3 Mathematical analysis
Performance of the system is evaluated by calculating the various performance factor of the collector, which include; Top loss coefficient, Total useful energy, Useful energy of water, thermal Efficiency, photovoltaic Efficiency, temperature variation of wax, plate and PCM. Apply implement above this measurement for a solar collector system which use the basic equation of Hottel-Bliss-Whillier with some modification. It was possible to improvement of overall loss coefficient for a solar collector to modify by the mathematical equation. In this study thermal 5 Page 5 of 24
network for single glass cover system Figure 3. At some typical location on the solar collector plate where temperature Tp, solar energy of amount S is absorbed by the plate. This solar energy S was distributed to loss through the top, bottom and edges and to useful energy gain of the
ip t
system. Overall loss coefficient from the collector system may be given by: UL=Ut+Ub+Ue
(i)
cr
Energy loss through the bottom of the collector is represented by three series resistor. R2 represents the resistance to heat flow through the insulation and R3 represents the convection and
us
radiation resistance to the environment. For better insulation R3 value was zero. In a welldesigned system the edge loss may be small so that it is not necessary to predict it with great
an
accuracy [12]. Back loss coefficient of the system is express by: Ub=Ue =K/x
(ii)
M
The loss coefficient for the top surface is the result of convection and radiation between parallel plates. The energy transfer between the plate at Tp and the glass cover is depending on the energy
d
loss to the surroundings from the cover glass [12]. Top loss coefficient is calculated from: (iii)
te
Ut=[1/(hp-c +hr,p- c) +1/(hw+hr,c-s)]-1
The useful energy gain of the system is the sum of PCM is used to heat and water carried heat
Ac ce p
from the system. Total useful energy of the system is given by: Qu=ApFR[S-UL(Ti-Ta)]
(iv)
And the useful energy of water denoted by the equation by: Qw =mcp(T0-Ti)
(v)
Thermal efficiency of this system is express by: ηt=Qu/HAp η0CR
(vi)
Photovoltaic efficiency is calculated from: η=P/qApv
(vii)
6 Page 6 of 24
3. Results and Discussion For evaluating thermal performance of PVT solar collectors, top heat loss coefficient is required. The thermal performance evaluation of flat plate collectors, and the design, simulation of heat
ip t
losses depends on the correct value of Ut with vertical configuration. Different variables like Top heat loss coefficient, Ut, has to be computed for various values of different variables like ambient temperature (Ta), wind heat transfer coefficient (hw), absorber plate temperature (Tp), angle of
cr
inclination of collector (β), and air gap spacing between absorber plate and glass cover (L).
us
Numerical solutions of empirical equations have been used for computing top heat loss coefficient of a flat plate collector [24-29].
an
Several tests on the solar collector are performed during some days in December, January & February. Clear and semi-cloudy day of those month results on PVT solar collector system are presented in Figure 4 and Figure 5, respectively. Total loss coefficient shows comparable values for the clear day and semi-
M
cloudy day in December, January and February. Graph show slightly larger value for clear day such value may be explained by the higher plate temperature for clear day compare to semi cloudy day. It is observed that increase of top loss & total loss was sharply up to 1pm due to plate temperature increase but it
d
became slight slower after the next point. This graph also shows that total heat loss coefficient varying
te
from 3.5 to 4.5 W/m2K for clear day but total loss coefficient was near to equal for semi cloudy day because of the plate temperature variation with time. The friction and heat transfer coefficient for a flat
Ac ce p
plate can be determined by solving the conservation of mass, momentum, and energy equations (either approximately or numerically). The convection heat transfer coefficient, in general, varies along the flow direction. The mean or average convection heat transfer coefficient for a surface is determined by(properly) averaging the local heat transfer coefficient over the entire surface. (Figure 4 and 5)
Kostic et al. [30] had studied the influence of reflectance from the flat plate solar radiation concentrators by using water as the energy carrier on energy efficiency of PVT collector. A new design for a double pass PVT air collector was developed and illustrated by Othaman et al. [31, 32] with CPC and reported that the thermal and electrical output of the PVT system increases with increase in air mass flow rate. To achieve a significant efficiency enhancement of the PVT collector, they mentioned the utility of fins as an integral part of absorber plate which showed a good agreement between theoretical and experimental results. Matrawy et al. have used metal slats between the absorber plate and bottom plate of a solar air
7 Page 7 of 24
heater and reported an enhanced efficiency of a solar collector [33]. Several researchers reported about the scope for performance improvement by heat extraction in the absorber plate with fins [32-36]. In Figure 6, the curve shows average total loss coefficient increases with average plate temperature because high temperature indicates more loss for collector. Average plate temperature was around 87°C
ip t
on clear days and 70°C on semi cloudy days. The solar radiation absorbed by the absorber plate increases the temperature of the system. During low and off-sunshine hours, part of thermal energy is transferred to
cr
the circulating water as observed during experiments. The heat is transfer from liquid PCM to the circulating water until the PCM solidifies. To dampen the rate at which various temperatures in the
us
system change usually PCM employed in a flat plate collector as described by other researchers and thus the system can be dealt with steady-state condition [37-42]. The solar energy stored in a salt-hydrate PCM held in the collector could be discharged to cold water flowing through a surface heat exchanger located
an
in a layer of stationary heat transfer liquid floating over an immiscible layer of PCM.
M
(Figure 6)
The plate temperature was found to increase up to a distance of around 3m from water entrance, after
d
which an almost steady temperature was noticed because of using PCM and proper distribution of
te
temperature was noticed as shown in Figure 7. In this graph at 1pm, presentation line indicates high plate temperature compare to with other two lines because the solar radiation absorbed by the absorber plate
Ac ce p
increases the temperature of the system. But the plate temperature increasing trend with distance from entrance obtained for a similar system without the PCM in back layer. In a semi-cloudy day, plate temperature of the system was almost same as shown in Figure 8 at all three times during due to fluctuation of solar radiation.
(Figure 7 and 8)
Total useful energy is the sum of heat carried by water and heat transfer to PCM. At low sunshine hour around after 3pm useful energy of water line above the total useful energy line indicate part of thermal energy was transfer to the circulating water as shown in Figure 9. Total useful energy and useful energy 8 Page 8 of 24
of water slightly increase up to 2pm after that useful energy is decrease up to next point. Lastly useful energy of water increase indicates direction of heat flow from the PCM to water. Thermal efficiency was measured by the useful energy gain of the system divided by the total solar radiation incident on the collector. Thermal efficiency of the collector, was from around 40% - 50% for those three months as
ip t
shown in Figure 10. A decrease trend of thermal efficiency with time was performing for clear day, which directly related to the increase trend of the overall loss coefficient with time. Efficiency through the semi-cloudy day of those months seems nearly constant value and this result effect nearly steady change
an
(Figure 9 and 10)
us
cr
of top or total loss coefficient with time.
Photovoltaic-thermal efficiency indicates total efficiency of the collector (sum of thermal efficiency and
M
PV efficiency). Total efficiency decrease with time and total efficiency varies from 55%-63% which was 40%-50% for thermal application. Total efficiency nearly steady with time in semi cloudy day and this
te
d
result varies from 46%-55% as shown in Figure 11.
Ac ce p
(Figure 11)
The increasing trend of the top loss coefficient with time shows a slightly decreasing trend for the clear days of January and February. On the other hand the efficiency after mid-day seems almost constant for the clear and semi cloudy days and reflects the nearly steady change of top loss coefficient with time. Marginal variations can be seen for the thermal efficiency of the three months, which shows fluctuations in the climatic conditions with to a conventional. However, employment of PCM as a storage media and the combination of collector and storage in one unit is more useful for a solar system as observed through the study and also by other previous reports [37-42].
9 Page 9 of 24
4. Conclusion The following findings have been drawn from the experimental investigations on the PVT solar collector with CPC. Convection and radiation loss between plate, glass and surrounding was maximum indicate
ip t
highest top loss which value around 3 W/m2K for clear day and around 2.5 W/m2K for semi-cloudy day. Thermal efficiency of solar collector varies from 40%-50% for clear day and around 40% for semi-cloudy day, which value around 35% for locally made flat plate collector. Overall efficiency of the PVT solar
cr
collector was between 55%-63% for clear day and around 46%-55% for semi-cloudy day. The plate temperature gradually increase up to 3 m from water entrance to the solar collector, after which absorber
us
plate temperature value all most same was indicate but increasing trend up to total length of the pipe. These values obtained from without PCM collector system. Useful energy of water temperature was
an
found to be higher compare with useful energy indicating the storage capacity of the PCM.
[1]
M
References
S.A. Kalogirou, Y. Tripanagnostopoulos, Hybrid PV/T solar systems for domestic hot
d
water and electricity production, Energy Conversion and Management 47 (18) (2006) 3368-
[2]
te
3382.
I. Dincer, Evaluation and selection of energy storage systems for solar thermal
[3]
Ac ce p
applications, International Journal of Energy Research 23 (12) (1999) 1017–1028. J. Prakash, H.P. Garg, G. Datta, A solar water heater with built-in latent heat storage,
Energy Conversion and Management 25 (1) (1985) 51–56. [4]
K.S. Reddy, Thermal modeling of PCM-based solar integrated collector storage water
heating system, ASME Transactions – Solar Energy Engineering 129 (4) (2007) 458–464. [5]
Z. Chen, M. Gu, D. Peng, Heat transfer performance analysis of a solar flat-plate
collector with an integrated metal foam porous structure filled with paraffin, Applied Thermal Engineering 30 (14-15) (2010) 1967–1973. [6]
H.E. Qarnia, Numerical analysis of a coupled solar collector latent heat storage unit using
various phase change materials for heating the water, Energy Conversion and Management 50 (2) (2009) 247–254. [7]
S.A. Kalogirou, Y. Tripanagnostopoulos, Energy Convers. Manage. 47 (2006) 3368.
[8]
J. Ji, J. Hun, T.T. Chow, H. Yi, J. Lu, W. He, W. Sun, Energy Build. 38 (2006) 1380. 10 Page 10 of 24
[9]
S. Dubey, S.C. Solanki, A. Tiwari, Energy Build. 41 (2009) 863.
[10]
J.A. Duffie, W.A. Beckman, Solar Engineering of Thermal Processes, 3rd ed., Wiley,
Hoboken, NJ. 2006. [11]
R. Tchinda, Thermal behaviour of solar air heater with compound parabolic concentrator,
[12]
ip t
Energy Conversion and Management 49 (2008) 529-540.
N.K. Bansal, D. Buddhi, Performance equations of a collector cum storage system using
[13]
cr
phase change materials, Solar Energy 48 (3) (1992) 185–194.
Y. Rabin, I. Bar-Niv, E. Korin, B. Mikic, Integrated solar collector storage system based
[14]
us
on a salt-hydrate phase-change material, Solar Energy 55 (6) (1995) 435–444.
A.D. Gracia, E. Oró, M.M. Farid, L.F. Cabeza, Thermal analysis of including phase
an
change material in a domestic hot water cylinder, Applied Thermal Engineering 31 (17-18) (2011) 3938–3945. [15]
L.F. Cabeza, H. Mehling, S. Hiebler, F. Ziegler, Heat transfer enhancement in water
M
when used as PCM in thermal energy storage, Applied Thermal Engineering 22 (10) (2002) 1141–1151.
T.J.N. Schoen, Building-integrated PV installations in The Netherlands: Examples and
d
[16]
operational experiences, Solar Energy 70 (6) (2001) 467. J. Ji, J. Hun, T.T. Chow, H. Yi, J. Lu, W. He, W. Sun, Effect of fluid flow and packing
te
[17]
Ac ce p
factor on energy performance of a wall-mounted hybrid photovoltaic/water-heating collector system, Energy and Buildings 38 (12) (2006) 1380-1387. [18]
S. Dubey, S.C. Solanki, A. Tiwari, Energy and exergy analysis of PV/T air collectors
connected in series, Energy and Buildings 41 (8) (2009) 863-870. [19]
J. Chen, S. Lue, B. Liao, J. Energy Res. Technol. 127 (37) (2005).
[20]
J. Prakash, H.P. Garg, G. Datta, A solar water heater with a built-in latent heat storage,
Energy Conversion and Management 25 (1985) 51–56. [21]
K.S. Reddy, Thermal modeling of PCM-based solar integrated collector storage water
heating system, ASME Transactions – Solar Energy Engineering 129 (2007) 458–464. [22]
H. El Qarnia, Numerical analysis of a coupled solar collector latent heat storage unit
using various phase change materials for heating the water, Energy Conversion and Management 50 (2009) 247–254.
11 Page 11 of 24
[23]
I. Al-Hinti, A. Al-Ghandoor, A. Maaly, I. Abu Naqeera, Z. Al-Khateeb, O. Al- Sheikh,
Experimental investigation on the use of water-phase change material storage in conventional solar water heating systems, Energy Conversion and Management 51 (2010) 1735–1740. [24]
H.C. Hottel, B.B. Woretz, The performance of flat plate solar heat collectors, Trans
[25]
ip t
ASME 64 (1942) 94–102.
S.A. Klein, Calculation of flat-plate collector loss coefficients, Solar Energy 17 (1975)
[26]
cr
79–80.
J.A. Duffie, W.A. Beckman, Solar engineering of thermal processes, 2nd ed. New York:
[27]
us
Wiley, 1991.
V.K. Agarwal, D.C. Larson, Calculation of top heat loss coefficient of a flat-plate solar
[28]
an
collector, Solar Energy 27 (1981) 69–71.
A. Malhotra, H.P. Garg, A. Patil, Heat loss calculation of flat-plate solar collectors, J
Therm Eng (J Ind Soc Mech Eng) 2 (1981) 59–62.
V. Badescu, Optimal control of flow in solar collector systems with fully mixed water
M
[29]
storage tanks, Energy Convers Manage 49 (2008) 169–84. L.T. Kostic, Tomislav, T.M. Pavlovic, T. Zoran, Z.T. Pavlovic, Influence of reflectance
d
[30]
from flat aluminum concentrators on energy efficiency of PV/Thermal collector, Appl Energy 87 M.Y. Othman, Baharudin, B.Y.K Sopian, M.N. Abu Bakar, Performance analysis of a
te
[31]
Ac ce p
double-pass photovoltaic/thermal (PV/T) solar collector with CPC and fins, Renewable Energy 30 (2005) 2005–2017. [32]
M.Y. Othman, B.Y.K. Sopian, M.N. Abu Bakar, Performance studies on a finned double-
pass photovoltaic-thermal (PV/T) solar collector, Desalination 209 (2007) 43–49. [33]
P.G. Charalambous, G.G. Maidment, S.A. Kalogirou, K. Yiakoumetti, Photovoltaic
thermal (PV/T) collectors: A review, Appl Therm Eng. 27 (2007) 275–286. [34]
J.K. Tonui, Y. Tripanagnostopoulos, Air-cooled PV/T solar collectors with low cost
performance improvements, Solar Energy 81 (2007) 498–511. [35]
K.K. Matrawy, Theoretical analysis for an air heater with a box type absorber, Solar
Energy 63 (1998) 191–198. [36]
C.D. Ho, H.M. Yeh, T.W. Cheng, T.C. Chen, R.C. Wang, The influence of recycle on
performance of double pass flat solar air heaters with internal fins attached, Appl Energy 86 (2009) 1470–1478. 12 Page 12 of 24
[37]
A. Koca, H.F. Oztop, T. Koyun, Y. Varol, Energy and exergy analysis of a latent heat
storage system with phase change material for a solar collector, Renewable Energy 33 (2008) 567–574. [38]
A.A. El-Sebaii, A.A. Al-Ghamdi, F.S. Al-Hazmi, A.S. Faidah, Thermal performance of a
[39]
ip t
single basin solar still with PCM as a storage medium, Applied Energy 86 (2009) 1187–1195. M. Mazmana, L.F. Cabeza, H. Mehling, M. Nogues, H. Evliya, H. Paksoy, Utilization of
cr
phase change materials in solar domestic hot water systems, Renewable Energy 34 (2009) 1639– 1643.
A.K. Bhargava, A solar water heater based on phase-changing material, Applied Energy
us
[40]
14 (1983) 197–209.
N.K. Bansal, D. Buddhi, Performance equations of a collector cum storage system using
an
[41]
phase change materials, Solar Energy 48 (1992) 185–194. [42]
Y. Rabin, I. Bar-Niv, E. Korin, B. Mikic, Integrated solar collector storage system based
d
M
on a salt-hydrate phase-change material, Solar Energy 55 (1995) 435– 444.
te
Highlights
Ac ce p
• We examine the solar radiation conversion into thermal energy and energy storage • Compound parabolic concentrator has been mounted on photovoltaicthermal collector • Overall efficiency of the PVT solar collector was higher • The plate temperature gradually increase from water entrance to the solar collector
13 Page 13 of 24
ip t cr us an M
Figure 1: Sectional view (top) and top view (bottom) of the PVT solar collector system with various
Ac ce p
te
d
dimensions (dimensions in m) used in this study.
14 Page 14 of 24
ip t cr us an
Ac ce p
te
d
M
Figure 2: The geometry of the investigated PVT solar collector
15 Page 15 of 24
ip t cr us an
Ac ce p
te
d
M
Figure 3: Thermal network for the PVT collector system with compound parabolic concentrator.
16 Page 16 of 24
ip t cr us an
Figure 4: Variation of total loss and top loss coefficient with time on clear day in December, January, and
Ac ce p
te
d
M
February.
17 Page 17 of 24
ip t cr us an
Figure 5: Variation of total loss and top loss coefficient with time on semi-cloudy day in December,
Ac ce p
te
d
M
January and February.
18 Page 18 of 24
ip t cr us an M
Ac ce p
te
d
Figure 6: Relation between average total loss coefficient and average plate temperature.
19 Page 19 of 24
ip t cr us an
Figure 7: Variation of plate temperature with distance from entrance on clear day in December, January
Ac ce p
te
d
M
and February.
20 Page 20 of 24
ip t cr us an
Figure 8: Variation of plate temperature with distance from entrance on semi-cloudy day in December,
Ac ce p
te
d
M
January and February.
21 Page 21 of 24
ip t cr us an M
Figure 9: Variation of solar radiation, total useful energy and useful energy of water with time in
Ac ce p
te
d
December, January and February.
22 Page 22 of 24
ip t cr us an
M
Figure 10: Compare variation of Thermal efficiency with time on clear day and semi-cloudy day in
Ac ce p
te
d
December, January and February.
23 Page 23 of 24
ip t cr us an
M
Figure 11: Photovoltaic- Thermal efficiency compare with time on clear and semi-cloudy day in
Ac ce p
te
d
December, January and February.
24 Page 24 of 24