Electrical and thermal energy assessment of series connected N partially covered photovoltaic thermal (PVT)-compound parabolic concentrator (CPC) collector for different solar cell materials

Accepted Manuscript Electrical and thermal energy assessment of series connected N partially covered photovoltaic thermal (PVT)-compound parabolic concentrator (CPC) collector for different solar cell materials Vineet Saini, Rohit Tripathi, G.N. Tiwari, I.M. Al-Helal PII: DOI: Reference:

S1359-4311(17)30465-9 https://doi.org/10.1016/j.applthermaleng.2017.09.119 ATE 11176

To appear in:

Applied Thermal Engineering

Received Date: Revised Date: Accepted Date:

21 January 2017 13 July 2017 23 September 2017

Please cite this article as: V. Saini, R. Tripathi, G.N. Tiwari, I.M. Al-Helal, Electrical and thermal energy assessment of series connected N partially covered photovoltaic thermal (PVT)-compound parabolic concentrator (CPC) collector for different solar cell materials, Applied Thermal Engineering (2017), doi: https://doi.org/10.1016/ j.applthermaleng.2017.09.119

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Electrical and thermal energy assessment of series connected N partially covered photovoltaic thermal (PVT)-compound parabolic concentrator (CPC) collector for different solar cell materials Vineet Saini a, Rohit Tripathi *b, G. N. Tiwari c, I.M. Al-Helal d a

b

c

d

AIARS (M&D), Amity University, Sector-125, Noida, UP -201303, India

Centre for Energy Studies, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India.

Bag Energy Research Society (BERS), SODHA BERS COMPLEX, Plot No. 51, Mahamana Nagar, Varanasi, UP, India

Department of Agriculture Engineering, College of Food & Agriculture Sciences, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia

Abstract In the present communication, N-partially covered photovoltaic thermal (PVT) collector integrated with compound parabolic concentrator (CPC) connected in series has been considered to evaluate the annual electrical gain, overall thermal energy and exergy by considering five different solar cell materials. In the present paper, concentration ratio (CR) is considered as Aa:Ar is 2. Following cases have been named as [case (i)]: mono crystalline silicon (c-Si) based solar cells/PV module, [case (ii)]: poly crystalline silicon (p-Si) based solar cells/PV module, [case (iii)]: amorphous silicon (a-Si) based solar cells/ PV module, [case (iv)]: cadmium telluride (CdTe) based solar cells/ PV module and case (v): copper-indium-galliumselenide (CIGS) based solar cells/ PV module. The electrical efficiency for considered all five cases of N PVT-CPC collector have been compared on hourly basis and further, monthly thermal and electrical gains have been obtained for a year by numerical computation. The mass flow rate and number of collector of PVT-CPC collector have been optimized. Numerical computations have been carried out for all weather conditions at New Delhi, India. It has been observed that proposed case (i) has been found to be better than other other proposed cases from electrical, an overall thermal energy and exergy based on annual performance. Keywords: PVT; Compound parabolic concentrator (CPC); solar cell materials.

*Corresponding author: Tel.: +91 9958268783 1

E-mail Address: [email protected] 1. Introduction In recent years, solar energy has been strongly presented as a wide energy source. One of the simply available and most direct applications of solar energy is the conversion of sun radiation into thermal and electrical power. Radiation of sun can be utilized for water heating in domestic and industrial hot water systems, swimming pools as well as solar fluids for power generation by steam turbine. Solar water heating systems classify into mainly two parts: collector and water tank. Solar collector collects solar radiation from sun and converts this radiation into heat by using a fluid and electrical power. Solar heating system can either be active or passive but active systems are found common in use. Active systems can work with pump or motor to circulate the fluid from collector to storage tank. The basic theoretical concepts of photovoltaic thermal (PVT) collector have identified [1-2]. They have presented that solar collector are known as PVT collector which consists PV cells or panel and thermal absorber. It is capable to generate the electrical as well as thermal gain simultaneously. PVT collectors further identified mainly in concentrated PVT and flat plate PVT collector [3] and [4]. Here, it is concluded that the concentrated PVT generates higher overall energy and exergy as compare to flat plate PVT collector, due to larger area is available to collect the sun radiation on receiver. Charalambous et al. [5], Zondag 2008 [6], Chow [7] and Ibrahim et al. [8] studied the recent advancement on PVT collector. They have reported that two types of configuration have been used in PVT collector: tube in plate and tube in collector. And it also stated that a fluid is flowing below the PVT collector increases the electrical efficiency of PV module and also generate the thermal gain by extracting the additional heat from the collector. Chow et al. [9] presented a photovoltaic-thermosyphon collector with rectangular flow channels.

2

A numerical thermal model of PVT collector was developed based on the finite-difference control volume method. The model validation showed that the numerical model has been able to give accurate prediction of the daily thermal performance. Sopian et al. [10] studied performance of single-pass and double-pass combined photovoltaic thermal collectors are analyzed with steady-state models. They have observed that the improved performance of a double-pass photovoltaic thermal solar collector over the singlepass case could be attributed to the productive cooling of the photovoltaic cells and reduction in the temperature of the glass cover. Hence, higher photovoltaic cell efficiency was obtained. Hence, the double pass hybrid solar collector could produce more heat and, at the same time, had a productive cooling effect on the photovoltaic cells. It should also be noted that an improved performance of the double-pass photovoltaic thermal solar collector was achieved at very little increase in collector capital cost. Tiwari and Sodha [11] developed thermal model of an integrated photovoltaic and thermal solar (IPVTS) water/air heating system. Four configurations have been considered namely: (a) UGT, (b) GT, (c) UGWT and (d) GWT. It is found that the characteristic daily efficiency of IPVTS system with water is higher than with air for all configurations except GWT. It is also observed that an overall thermal efficiency of IPVTS system for summer and winter conditions is about 65% and 77%, respectively. Fraisse et al. [12] studied a solar water heating collector and PV cells in form of PVT collector. The annual photovoltaic cell efficiency is 6.8% which represents a decrease of 28% in comparison with a conventional non-integrated PV module of 9.4% annual efficiency. Chow et al. [13] and [14] studied energy and exergy analysis of PVT collector with and without glass cover. The energetic efficiency of the glazed PVT collector was found always better than the unglazed collector. The overall energy and exergy

3

analysis of PVT collector are validated by experimental study. It is concluded that overall exergy efficiency of water-cooled unglazed PVT collector was usually higher than for a glazed PVT collector. The overall energy and exergy evaluation of a PVT collector have presented [15]. It is identified that the overall exergy and thermal efficiency has found maximum at the hot water withdrawal flow rate of 0.006 kg/s. The energy of a PVT water collector has evaluated with 500800 W/m2 solar radiation range [16]. It has observed that 68.4 % overall efficiency of PVT water collector has obtained at flow rate 0.041 kg/s and 800 W/m2 solar radiation. The basic parameters of different solar cells specified in detail. The comparison of electrical efficiency of semitransparent and opaque PV modules reported and further, semitransparent PV cells studied with five different types of solar cells [17]. Cost analysis was also carried out for the same modules and solar cells. It is observed that silicon based solar cell possess maximum annual electrical gain resulting minimum cost per unit electrical energy whereas CIGS has been found to be having lowest cost among all. Energy matrices of hybrid photovoltaic thermal (HPVT) water collector studied with different PV technology [18]. It is concluded that c-Si PV module was chosen best for production of electrical power. The characteristics parameters of the PV cell for concentrating and non-concentrating solar radiation reported respectively, tested experimentally. The experimental study of the two-stage photovoltaic thermal system was established with a 1.8 m2 mirror PVT stage and a 15 m2 mirror heating stage and 1.8 m2 mirror PVT stage and 30 m2 mirror heating stage [19]. The performance of a V-trough photovoltaic thermal concentrator has been carried to evaluate the performance and concluded that better electrical output could be achieved [20].

4

A PVT with a combination of a booster diffuse reflector and vacuum tube was proposed for generation of electricity and hot water production [21]. A silicon monocrystalline PV module was used to appropriate reflectors in order to increase insolation in conjunction with a closed loop cooling facility to efficient extract the PV panel’s heat. Thermal modelling and the temperature dependent electrical efficiency for partially covered N number of PVT-compound parabolic concentrator, connected in series derived by Tripathi et al. [22-23]. They have also compared the thermal performance for winter and summer season and concluded that higher thermal efficiency is found in winter season. The annual overall energy and exergy and carbon credits have evaluated for N-PVT-CPC collector connected in series by considering all type of whether condition (a-d type) [24]. Further, a comparison of performance has been carried out for the output of series collector: N-PVT-CPC collector, N-CPC collector, N-PVT collector and NFPC collector with molten sat as a fluid for New Delhi, India [25]. The conclusion has been found that N-CPC collector is best suited for thermal performance to other proposed systems. Further, other study has been discussed for N-PVT-CPC collector at constant collection temperature mode as point of industrial application and annual overall energy and exergy have been obtained and water and air have been used for cold climate condition [26-29]. An experimental validation has been performed for a fully covered PVT-CPC collector by considering two different tracking based cases: case (i): fixed position (non-tracking) and case (ii): Manual MPPT (maximum power point tracking) [30]. Here, case (ii) has been found to be suited best for thermal performance (overall energy and exergy). A detailed and extensive study has been carried out for energy matrices and exergo-economic analysis of N concentrated PVT collector. Here, three systems have been considered to compare the performance and the cost analysis has been obtained for n=30, 40 and 50 years, respectively [31].

5

The objective of present study is to choose the best solar cell material where the maximum electrical gain can be obtained for series connection of N-PVT-CPC collector which was not studied earlier. The attempt has been taken for five different solar cell materials. The comparative study has been performed to evaluate annual electrical and thermal gain and overall energy and exergy by considering five cases (i-v) [case (i): mono crystalline silicon (c-Si) based solar cells or module, case (ii): poly crystalline silicon (p-Si) based solar cells/module, case (iii): amorphous silicon (a-Si)/thin film based solar cells/module, case (iv): cadmium telluride (CdTe) based solar cells/module and case (v): copper-indium-gallium-selenide (CIGS) based solar cells/module] for partially covered N PVT-compound parabolic concentrator collector connected in series, at clear day condition, New Delhi, India. 2. System description In present communication, the partially covered N photovoltaic thermal compound parabolic concentrator (PVT-CPC) collector connected in series has been studied. The series connection is needed to achieve higher temperature of fluid. Water has been considered as a working fluid. This study has been focused on electrical and thermal performance of N PVT-CPC collector with different types of solar cells. The cross section side view and cut section view via XX’ of first partially covered PVT-CPC collector has been shown in Figs. 1 (a-b). The area of each collector (Ar) of N PVT-CPC collector is 1 m2. The each collector of N PVT-CPC has been covered partially by semitransparent (glass to glass) PV module (Arm=0.25 m2) and rest part of receiver is covered by toughened glass (Arc=0.75 m2). The PV module has been placed at lower portion on each collector of present system. The aperture area (Aa) of each collector of PVT-CPC is 2 m2. The concentration ratio in the present system is 2 (Aa: Ar=2:1). The side view and top side view of partially covered (25% of PV module) N PVT-CPC water collector connected in series, have

6

been shown in Figs. 2. The inlet temperature and final outlet fluid (water) temperature at Nth collector of partially covered PVT-CPC have been considered as Tfi and T foN, respectively. The working principal of N PVT-CPC collector is followed [25]. Here, five cases have been proposed on the basis of solar cell material as cases (i-v) [mono crystalline silicon based solar cells or module, poly crystalline silicon based solar cells/module, amorphous silicon/thin film based solar cells/module, cadmium telluride based solar cells/module and copper-indium-galliumselenide based solar cells/module, respectively]. Four types of weather conditions in India are defined by Meteorological Department (IMD) Pune, India.

- for clear days- sunshine hours are available for greater than or equal to 9 hours per day, and if diffuse radiation is less than 50% or more than 25% of global radiation.

-

hazy days- sunshine hours are available in between 7 to 9 hours per day and if diffuse radiation is less than 50% or more than 25% of global radiation. - hazy and cloudy days- sunshine hours are available in between 5 to 7 hours per day, and if diffuse radiation is less than 75% or more than 50% of global radiation. - cloudy days- sunshine hours are available in less than or equal to 5 hours per day, and if diffuse radiation is more than 75% of global radiation. The basic input parameters of PVT-CPC collector have been placed in Table 1. The specifications and basic parameters for different types of solar cells have been obtained from Table 2. The number of available days to different types of weather conditions for New Delhi, India has been given in Table 3. 3. Thermal modelling

7

To write down the basic energy balance equations for present system, few assumptions have been considered. (a) Partially covered PVT-CPC water collector is supposed in quasi steady state. (b) Heat losses due to current flow, in semitransparent PV modules are neglected. (c) Heat capacity of insulator, absorber and solar cell materials are neglected. (d) Zero temperature gradient across thickness of PV module, insulation and glass materials have been considered. (e) Heat flow is one unidirectional. 3.1. Lower portion of the PVT-CPC Collector Energy balance equation for solar cell of semitransparent PV module (Figs. 1a and 1b) (1) From Eq. (1), one can find solar cell temperature ( ) as follows:

(2)

Energy balance for absorber plate below the Photovoltaic module

(3) From Eq. (2) and (3), one can get an expression for as

(4)

Expressions for

,

and

appendix-A. 8

have been given in

Energy balance for flowing water as fluid below the absorber plate (5) From Eqs. (2) and (4), Eq. (5) can be rewritten as follows: (6) where,

is the collector efficiency factor.

The solution of the above equation can be obtained by using initial condition i.e. (

)

as

(7)

The outlet water (as fluid) temperature at end of PV module can be evaluated as

(8) After knowing

from Eq. 8, the outlet water temperature of first PVT-CPC collector

is

given by

(9)

Now in present system, the outlet of very first collector and the outlet of second last collector fluid temperature

is inlet of second water collector

is the inlet of Nth collector. Similarly, the outlet

at end of Nth collector’s PV module. The expression for TfoN and

in the present system has been derived [22] and one can get the following 9

(10)

(11)

Expressions for

and

have been presented in appendix-A

The rate of useful thermal energy from partially covered N-PVT-CPC collector has been calculated with help of Eq. (10), by following equation [16] (12) And, the rate of thermal exergy from N-identical PVT-CPC collector has been evaluated by following expression [16]

(13)

where

= mass flow rate of water,

= specific heat of water,

= inlet water temperature and

Ta= ambient air temperature. The average flowing fluid temperature

can be obtained as follows:

(14) where

and

are the outlet temperature at (N-1)th collector of PVT-CPC collector

and the temperature at the end of the PV module of N th collector of PVT-CPC, respectively. After getting temperature (

from above Eq. (14), it is essential to find the expression of average solar cell ) with the help of Eq. (2) as [22].

10

(15)

The temperature dependent electrical efficiency of solar cells of a number (N) of PVT-CPC water collectors has been determined by following expression (16) where,

efficiency at STC (standard test condition),

temperature of Nth PVT-CPC collector and

o

C,

is the average solar cell

is temperature coefficient of solar cell efficiency.

Further, with the help of Eq. (16), the above equation can be rewritten following [22]:

(17) From Eq. (17), the temperature dependent electrical efficiency of PV modules of N PVT-CPC collector is following [16]

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(18) Further, the rate of usable electrical energy gain or exergy from N-identical PVT-CPC collector has been solved with the help of Eq. (18) by following equation [16]. (19) The rate of overall thermal energy of partially covered N PVT-CPC collector can be obtained from following expression [16]. Overall thermal energy= thermal energy + thermal equivalent of electrical energy [18-19]. . .

.

Qthe,overall , N  Quthe , N 

Q xele, N

(20)

0.38

Exergy of partially covered N PVT-CPC collector system will be calculated based on second law of thermodynamics. With the help of Eq. (13) and Eq. (19), the rate overall exergy can be obtained as follows [16] (21) 4. Methodology In order to obtain an annual overall thermal energy and exergy for partially covered N PVT-CPC collector, the numerical computations have been carried out for water: as a fluid and comparison has been made for different types of PV technology or solar cells. The methodology or flow chart have been given in Fig. 3. 5. Results and Discussion The variation of total radiation, beam radiation on horizontal surface and ambient air temperature for time of the clear sky day for New Delhi (2010) have been obtained from India 12

Meteorological Department (IMD), Pune, India. Further, hourly values of total radiation, beam radiation have been calculated at 30o (latitude) inclination for New Delhi, India by using MATLAB 2013. The results of hourly variation of beam radiation and ambient air temperature have been shown in Fig. 4. Hourly variations of ambient air temperature and the average beam radiation for a clear day of each month in a year have been shown in Figs. 5 and 6. Here, the maximum ambient air temperature has been obtained in month of May and minimum in January whereas maximum average beam radiation has been obtained in month of January and minimum in July. Hourly variation of average solar cell temperature (

and temperature dependent electrical efficiencies

of different material types of PV modules (??mN), considering five cases (i-v) at partially covered at Nth collector of partially covered PVT-CPC (25% of PV module area and 75% of glass area on each collector) have been shown in Fig. 7. Here, it is noted that electrical efficiencies of PV modules (??mN) are inversely proportional to the average solar cell temperature (

, which is expected due to losses occurs at higher solar cell

temperature. The electrical efficiency for amorphous based silicon PV module [a-Si: case (iii)] has been noted minimum and maximum for mono-crystalline silicon based PV module. Variation of mass flow rate to maximum outlet fluid (water) temperature with number of collectors has been obtained for case (i) only, in Fig. 8. Here, the mass flow rate (

) and

number of collector (N) have been optimized as 0.012 kg/s and N=6, due to limitation of boiling temperature of water which cannot be exceed above than 100 0C. Hourly variations of outlet water temperature (TfoN) for N-PVT-CPC collector for cases (i-v) have been shown in Fig. 9. It can be seen that the outlet fluid (water) temperature is more or less

13

equal to each other for all cases (i-v). The monthly electrical gain, overall thermal energy and exergy for clear days [type ‘a’] have been shown in Figs. 10. Here, the maximum gains have been obtained in month of September due to maximum availability of number of clear days. The maximum gain has been obtained for case (i) whereas minimum for case (iii). Monthly variation of electrical gain, overall thermal energy and exergy of proposed case (i) for considering different weather condition [types ‘a’, ‘b’, ‘c’ and ‘d’], New Delhi, India have been shown in Figs. 11. Here, maximum gains have been obtained in type ‘b’ and ‘c’ weather conditions due higher availability of respective days. The total net annual electrical gain, overall thermal energy and exergy for proposed case (i) of N-PVT-CPC collector by considering different weather conditions have been shown in Fig. 12. The net annual electrical gain, overall thermal energy and exergy have been obtained as 165.02 kWh, 5313.85 kWh and 512.80 kWh. Now, this same procedure has been adopted to evaluate net annual electrical, overall thermal energy and exergy for all proposed cases (i-v) of N-PVT-CPC collector by considering all weather conditions for New Delhi, India. Net annual electrical gain, overall thermal energy and exergy for all proposed cases (i-v) of NPVT-CPC collector by considering all weather conditions [types ‘a’, ‘b’, ‘c’ and ‘d’] of the same location have been shown in Figs. 13. It is seen that case (i) is dominating to other proposed cases by obtaining maximum gains. It is also observed that minimum gains have been obtained for case (iii) due to maximum solar cell temperature. 7. Conclusions Certain conclusions have been prepared on the basis of the present analysis:

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 The six number of collectors with mass flow rate 0.012 kg/s are able to produce 98 0C temperature of water in case (i) [mono crystalline silicon based solar cells] of partially covered N PVT-CPC collector connected in series (Fig. 8).  The maximum net annual electrical gain has been obtained for case (i) [mono crystalline silicon based solar cells], which is around 2 times higher than the gain obtained for case (iii) [amorphous thin film based solar cells] [Fig. 13 (a)].  Case (i) of partially covered N-PVT-CPC collector has been chosen best for thermal as well as electrical gain for annual basis including all different climate condition, New Delhi whereas case (iii) [amorphous silicon based solar cells] has been found as most poor material to achieve energy and exergy point of view (Figs. 13). Appendix A Following analytical terms are utilized in thermal modelling and numerical computation for PVT-compound parabolic concentrator collector system:

;

;

;

;

;

15

;

;

;

;

;

;

;

;

;

;

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[2] E.C. Kern, M.C. Russel. Combined photovoltaic and thermal hybrid collector system. In: Proceedings of the 13th IEEE Photovoltaic Specialists, Washington, DC, USA (1978) 1153– 1157. [3] J.S. Coventy. Performance of a concentrating photovoltaic/thermal solar collector. Solar Energy 78 (2005) 211–222. [4] J.I. Rosell, X. Vallverdu, M.A. Lechon, M. Ibanez. Design and simulation of a low concentrating photovoltaic/thermal system. Energy Conversion and Management 46 (2005) 3034–3046. [5] P.G. Charalambous, G.G. Maidment, S.A. Kalogirou. Photovoltaic thermal (PV/T) collectors: a review. Applied Thermal Engineering 27 (2007) 275–286. [6] H.A. Zondag. Flat-plate PV–thermal collectors and systems: a review. Renewable and Sustainable Energy Reviews 12 (2008) 891–959. [7] T.T. Chow. A review on photovoltaic/thermal hybrid solar technology. Applied Energy 87 (2010) 365–379. [8] A. Ibrahim, M.Y. Othman, M.H. Ruslan, S. Mat, K. Sopian. Recent advances in flat plate photovoltaic/thermal (PV/T) solar collectors. Renewable and Sustainable Energy Reviews 15 (2011) 352–365. [9] T.T. Chow, W. He, J. Ji. Hybrid photovoltaic-thermosyphon water heating system for residential application. Solar Energy 80 (2006) 298–306. [10] K. Sopian, H.T. Liu, K.S. Yigit, S. Kakac, T.N. Veziroglu. Performance analysis of photovoltaic thermal air heaters. Energy Conversion and Management 37 (1996) 1657–1670. [11] A. Tiwari, M.S. Sodha. Performance evaluation of hybrid PV/thermal water/air heating system: a parametric study. Renewable Energy 31 (2006) 2460–2474.

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12] G. Fraisse, C. Me´ne´zo, K. Johannes. Energy performance of water hybrid PV/T collectors applied to comb systems of Direct Solar Floor type. Solar Energy 81 (2007) 1426–1438. [13] T.T. Chow, G. Pei, K.F. Fong, Z. Lin, A.L.S. Chan, J. Ji. Energy and exergy analysis of photovoltaic–thermal collector with and without glass cover. Applied Energy 86 (2009) 310– 316. [14] A. Tiwari, S. Dubey, G.S. Sandhu, M.S. Sodha, S.I. Anwar. Exergy analysis of integrated photovoltaic thermal solar water heater under constant flow rate and constant collection temperature modes. Applied Energy 86 (2009) 2592–2597. [15] Ahmad Fudholi, Kamaruzzaman Sopian, Mohammad H. Yazdi, Mohd Hafidz Ruslan, Adnan Ibrahim, A. Kazem Hussein Performance analysis of photovoltaic thermal (PVT) water collectors. Energy conversion and management 78 (2014) 641-651. [16] S. Agrawal, G.N. Tiwari. Building Integrated Photovoltaic Thermal Systems: For Sustainable Developments (2010) RSC publishing, Cambridge, UK. [17] A. Gaur, G.N. Tiwari. Performance of photovoltaic modules of different solar cells. Journal of solar energy (2013) ID 734581, 1-13. http://dx.doi.org/10.1155/2013/734581 [18] R.K. Mishra, G.N. Tiwari. Energy matrices analyses of hybrid photovoltaic thermal (HPVT) water collector with different PV technology. Sol. Energy 91 (2013) 58–67. [19] R. Kunnemeyer, T.N. Anderson, M. Duke, J.K. Carson. Performance of a V-trough photovoltaic/thermal concentrator, Sol. Energy 101 (2014) 19–27. [20] G. Li, G. Pei, J. Ji, Y. Su. Outdoor overall performance of a novel air-gap-lens walled compound parabolic concentrator (ALCPC) incorporated with photovoltaic/thermal system, Appl. Energy 144 (2015) 214–223.

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[21] M. Mohsenzadeh, R. Hosseini. A photovoltaic/thermal system with a combination of a booster diffuse reflector and vacuum tube for generation of electricity and hot water production, Renew. Energy 78 (2015) 161-173. [22] R. Tripathi, G. N. Tiwari, I.M. Al-Helal. Thermal modelling of N partially covered photovoltaic thermal (PVT)–Compound parabolic concentrator (CPC) collectors connected in series. Solar Energy 123 (2016) 174–184. [23] R. Tripathi, S. Tiwari, G.N. Tiwari. Performance of Partially Covered N Number of Photovoltaic Thermal (PVT)-Compound Parabolic Concentrator (CPC) Series Connected Water Heating System. International Journal of Electrical, Computer, Energetic, Electronic and Communication Engineering 10 (1) (2016) 111-116. [24] R. Tripathi, G.N. Tiwari, V.K. Dwivedi. Overall energy, exergy and carbon credit analysis of N partially covered photovoltaic thermal (PVT) concentrating collector connected in series. Solar Energy 136 (2016) 260–267. [25] R. Tripathi, G.N. Tiwari. Energetic and exergetic analysis of N partially covered photovoltaic thermal- compound parabolic concentrator (PVT-CPC) collectors connected in series. Solar Energy 137 (2016) 441–451. [26] Tripathi R, Tiwari S, Tiwari GN. Energy analysis of partially covered Number (N) of photovoltaic thermal-compound parabolic concentrator collectors connected in series at constant collection temperature mode. Emerging trends in electrical electronics & sustainable energy system (ICETEESES-2016), IEEE international conference on, (2016) 12-17. [27] Tripathi R, Tiwari GN, Dwivedi VK. Overall energy and exergy performance of partially covered N-photovoltaic thermal (PVT)-compound parabolic concentrator (CPC) collectors

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connected in series. IEEE International Conference on Power Electronics, Intelligent Control and Energy Systems (ICPEICES) 2016; 12-17. DOI: 10.1109/ICPEICES.2016.7853669 [28] Tripathi R, Tiwari GN. Annual energy, exergy and environmental benefits of N half covered concentrated photovoltaic thermal (CPVT) air collector. 1st Springer International Conference on Emerging Trends and Advances in Electrical Engineering and Renewable Energy (ETAEERE) 2016; 12-19. [29] Tripathi R, Tiwari S, Tiwari GN. Energy performance of partially covered N photovoltaic thermal-compound parabolic concentrator (PVT-CPC) collector for cold climate condition. In IEEE second international conference on Innovative Applications of on Computational Intelligence on Power, Energy and Controls with their Impact on Humanity (CIPECH) 2016; 178-182. DOI: 10.1109/CIPECH.2016.7918762 [30] Tripathi R, Tiwari GN. Annual performance evaluation (energy and exergy) of fully covered concentrated photovoltaic thermal (PVT) water collector: An experimental validation. Solar Energy 2017; 146:180–190. [31] Tripathi R, Tiwari GN, Dwivedi VK. Energy matrices evaluation and exergoeconomic analysis of series connected N partially covered (glass to glass PV module) concentrated photovoltaic thermal collector: At constant flow rate mode. Energy Conversion and Management 2017; 145:357-370. Nomenclature Absorptivity of the solar cell

Solar cell temperature (0C)

Mass flow rate of water (kg/s)

Absorption plate temperature (0C)

Transmissivity of the glass

Thickness of absorption plate (m)

20

Specific heat of water (J/kg K)

Thermal conductivity of absorption plate (W/m K)

Temperature

coefficient

Inlet water temperature (0C)

of

efficiency (K-1) Total length of receiver area (m)

Water temperature (0C)

Total length of aperture area (m)

Outlet water temperature at the end of PV module (0C)

Length of receiver covered by glass

Efficiency at standard test condition

or PV module (m) Length of aperture covered by glass

Outlet water temperature at the end of

or PV module (m)

portion covered by glass (0C)

Solar cell efficiency

Outlet water temperature at the end of Nth PV module (0C)

PV module efficiency

Outlet water temperature at the end of Nth PVT-CPC water collector (0C)

Breath of receiver (m)

Heat transfer coefficient from bottom of PVT to ambient (W/m2 K)

Breath of aperture (m)

Heat transfer coefficient from top of PVT to ambient (W/m2 K)

Area of receiver covered by PV

Heat transfer coefficient for space

module (m2)

between the glazing and absorption plate (W/m2 K)

21

Area of receiver covered by glass

Overall heat transfer coefficient from

(m2)

cell to ambient (W/m2 K)

Area of aperture covered by PV

Overall heat transfer coefficient from

module (m2)

cell to plate(W/m2 K)

Area of aperture covered by glass

Heat

(m2)

blackened plate to water (W/m2 K)

Thickness of glass cover (m)

Overall heat transfer coefficient from

transfer

coefficient

from

plate to ambient (W/m2 K) Thermal

conductivity

of

glass

Overall heat transfer coefficient from

(W/m K)

module to ambient (W/m2 K)

Beam radiation (W/m2)

Overall heat transfer coefficient from glassing to ambient (W/m2 K)

Ambient temperature (0C)

Penalty factor due to the glass covers of module

Thickness of insulation (m)

Penalty factor due to plate below the module

Thermal conductivity of insulation

Penalty factor due to the absorption

(W/m K)

plate for the glazed portion

Product of effective absorptivity

Penalty factor due to the glass covers

and transmittivity

for the glazed portion

Collector efficiency factor

Packing factor of the module

22

X

Xo Absorption plate

Glazed surface

Solar cell

Air gap Inlet

Outlet

L

Insulation Cut section of metallic tubes

Figure 1 (a). Cross section side view of proposed partially covered PVT- compound parabolic concentrator first water collector where Arm=0.25 m2 and Arc = 0.75 m2.

b Solar cell

Figure 1 (b). Cut section XX' front view of partially covered PVT-compound parabolic concentrator first water collector.

23

1st collector Tfo1

2nd collector

Nth collector

3rd collector

Tfo2

Outlet, TfoN

Tfo3

Inlet, Tfi

Figure 2 (a). Series connection of N partially covered PVT-compound parabolic concentrator water collector.

1st collector PV module

2nd collector

Nth collector

Reflector

Tfo2

TfoN Outlet

TfoN-1

Tfo1 Absorber plate

Tfi Inlet Tube

Stand

Insulator

Figure 2 (b). Isometric view of series connected N partially covered PVT - compound parabolic concentrator (CPC) collector.

24

Methodology

Eq. 11 through Eqs. 1-10, has been solved to evaluate outlet fluid tem. for cases (i-v)

Step 1

Step 3

Eq. 17 through Eqs. 14-16, have been used to evaluate electrical efficiency of PV cells for cases (i-v) ??cN

TfoN Eqs. 12 and 13 have been solved to evaluate hourly thermal energy and exergy for cases (i-v)

Step 2

Step 4

Eq. 18 and 19 have been used to calculate hourly electrical gain for cases (i-v)

Step 5 Eqs. 20 and 21 have been solved for cases (i-v) for evaluating hourly overall thermal energy and exergy gain

Daily electrical gain, energy and exergy= Ʃ [hourly (08.00 to 16.00 hr.) overall thermal energy and exergy for cases (i-v)]

Step 6

Monthly electrical gain, energy and exergy= [Daily overall thermal energy and exergy for cases (i-iii)] * [No. of typical day in a month]

Step 7

Annual electrical gain, energy and exergy= Ʃ [all (1-12) monthly overall thermal energy and exergy for cases (i-v)]

Step 8

Figure 3. Methodology chart for evaluating annual electrical and thermal gain of partially covered N PVT- compound parabolic concentrator collector with different types of PV cells [cases (i-v)].

25

1000

15

900

14

Solar radiation, I (W/m2)

16

13

800 700 600 500

It

12

Ib Ta

11 10 9

400

8

300

7

200

6

100

Ambient air temperature, Ta(0C)

1100

5 7

8

9

10

11

12

13

14

15

16

17

Time of the day (hr)

Ambient air temperature, Ta(0C)

Figure 4. Hourly variation of Total, Beam radiation and ambient air temperature of a clear day in month of January for New Delhi, India.

Jan Feb March April May June July Aug Sep Oct Nov Dec

clear day condition only

38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 7

8

9

10

11

12

13

14

15

16

17

Time of the day (hr)

Figure 5. Hourly variation of ambient air temperature of clear days in each month in a year for New Delhi, India.

26

Clear day condition only

700

Average beam radiation, bI(W/m2)

600 500 400 300 200 100 0 Jan Feb MarchApril May June July Aug Sep Oct Nov Dec

No. of months

Figure 6. Monthly variation of average beam radiation of clear days at latitude (300) for New Delhi, India.

Tc-case(i) mN-case(i)

(0C) Average solar cell temperature, T c

120

0.14

Tc-case (ii) mN-case (ii)

Tc-case (iii) mN-case (iii) 0.13

110

0.12

Tc-case (iv) mN-case (iv) Tc-case (v) mN-case (v)

100 90 80

0.11 0.10 0.09

70

0.08

60

0.07

50 40

0.06

30

0.05

20

0.04 7

8

9

10

11

12

13

14

15

16

Electrical efficiency of PV module, mN (in fraction)

130

17

Time of the day (hr)

Figure 7. Hourly variation of average solar cell temperature and electrical efficiency of different types PV module [cases (i-v)] of a clear day in month of January for New Delhi, India.

27

TfoN,max(oC)

200 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20

1st PVT-CPC collector 2nd II 3rd II 4th II 5th II 6th II

PV module area=25%

0.002

0.004

0.006

0.008

0.010

0.012

Mass flow rate (kg/s)

Figure 8. Variation of mass flow rate to the maximum outlet temperature at Nth collector of PVTCPC [case (i)] of a clear day in month of January for New Delhi, India.

Outlet fluid temperature at Nth collector, TfoN(0C)

100

case (i) case (ii) case (iii) case (iv) case (v)

25 % PV, mf=0.012 kg/s, N=6

90 80 70 60 50 40 30 20 7

8

9

10

11

12

13

14

15

16

17

Time of the day (hr)

Figure 9. Hourly variation of outlet fluid (water) temperature at Nth collector of PVT-CPC [case (i-v)] of a clear day in month of January for New Delhi, India.

28

Monthly electrical gain (kWh)

5

case (i) case (ii) case (iii) case (iv) case (v)

25 % PV, mf=0.012 kg/s, N=6

4

3

2

1

0 Jan feb march april may june july aug sep oct

nov dec

No. of months

Figure 10 (a). Monthly variation of electrical gain at Nth collector of partially covered PVT-CPC [case (i-v)] of clear days [Type ‘a’] for New Delhi, India.

case (i) case (ii) case (iii) case (iv) case (v)

25 % PV, mf=0.012 kg/s, N=6

Overall thermal energy (kWh)

180 160 140 120 100 80 60 40 20 0 Jan feb march april may june july aug sep oct

nov dec

No. of months

Figure 10 (b). Monthly variation of overall thermal energy at Nth collector of partially covered PVT-CPC [case (i-v)] of clear days [Type ‘a’] for New Delhi, India.

29

case (i) case (ii) case (iii) case (iv) case (v)

25 % PV, mf=0.012 kg/s, N=6

Overall exergy (kWh)

20

15

10

5

0 Jan feb march april may june july aug sep oct

nov dec

No. of months

Figure 10 (c). Monthly variation of overall exergy at Nth collector of partially covered PVT-CPC [case (i-v)] of clear days [Type ‘a’] for New Delhi, India. 25 % PV, mf=0.012 kg/s, N=6

a type b type c type d type

6

Electrical gain (kWh)

5 4 3 2 1 0

Jan feb march april may june july aug sep oct

nov dec

Month of the year

Figure 11 (a). Monthly variation of electrical gain at Nth collector of partially covered PVT-CPC [case (i)] by considering different weather conditions [Types ‘a’, ‘b’, ‘c’ and ‘d’], for New Delhi, India.

30

25 % PV, mf=0.012 kg/s, N=6 220

Overall thermal energy (kWh)

200

a type b type c type d type

180 160 140 120 100 80 60 40 20 0

Jan feb march april may june july aug sep oct

nov dec

Month of the year

Figure 11 (b). Monthly variation of overall thermal energy at N th collector of partially covered PVT-CPC [case (i)] by considering different weather conditions [Types ‘a’, ‘b’, ‘c’ and ‘d’], for New Delhi, India.

25 % PV, mf=0.012 kg/s, N=6

Overall exergy (kWh)

25

a type b type c type d type

20

15

10

5

0

Jan feb march april may june july aug sep oct

nov dec

Month of the year

Figure 11 (c). Monthly variation of overall exergy at N th collector of partially covered PVT-CPC [case (i)] by considering different weather conditions [Types ‘a’, ‘b’, ‘c’ and ‘d’], for New Delhi, India.

31

5313.85

Energy/exergy (kWh)

5000

4000

3000

2000

1000

512.80 165.02

0

Electrical gain

overall thermal energy

overall exergy

Figure 12. Total annual electrical energy, overall thermal energy and exergy obtained at N th collector of partially covered PVT-CPC [case (i)] by considering different weather conditions [Types ‘a’, ‘b’, ‘c’ and ‘d’], for New Delhi, India.

165.02

162.45

Annual electrical gain (kWh)

160 140

112.48

120 100

114.05

81.32

80 60 40 20 0

c-si

p-si

a-si

CDTe

CIGS

Types of PV materials

Figure 13 (a). Total annual electrical gain obtained at N th collector of partially covered PVT-CPC [case (i-v)] by considering different weather conditions [Types ‘a’, ‘b’, ‘c’ and ‘d’], for New Delhi, India.

32

Annual overall thermal energy (kWh)

5313.85

5305.65

c-si

p-si

5255.24

5245.11

5264.12

CDTe

CIGS

5000

4000

3000

2000

1000

0

a-si

Types of PV materials

Figure 13 (b). Total annual overall thermal energy obtained at N th collector of partially covered PVT-CPC [case (i-v)] by considering different weather conditions [Types ‘a’, ‘b’, ‘c’ and ‘d’], for New Delhi, India.

512.80

510.25

c-si

p-si

Annual overall exergy (kWh)

500

485.98

496.12

479.89

a-si

CDTe

CIGS

400

300

200

100

0

Types of PV materials

Figure 13 (c). Total annual overall exergy obtained at N th collector of partially covered PVTCPC [case (i-v)] by considering different weather conditions [Types ‘a’, ‘b’, ‘c’ and ‘d’], for New Delhi, India.

33

Table 1. Values of design parameters of partially N-PVT-CPC water collector system, used in

m2

W/m2 oC m2

W/m2 oC

m2 m2 m2 m2

W/m2 W/m2 m2

W/m2

m2

W/m2 ρ = 0.84

W/m oC m W/moC,

J/kg K (water)

m

= 0.012 kg/s

W/m oC,

0.8 Tube diameter = 0.0125 m

m W/m2 oC

W/m2 oC W/m2 oC

W/m2 oC analytical computation.

Table 2. Specifications and basic parameters of different types of solar cells [16 and 17]. Types of solar cells c-Si [case (i)] p-Si [case (ii)] a-Si [case (iii)] CdTe [case (iv)] CIGS [case (v)]

Temp. coefficient ( ), in ( 0C-1)

Module efficiency ( ), in %

0.9

0.89

0.0040

16

0.9

0.89

0.0040

14

0.85

1

0.0026

6

0.8

1

0.0020

8

0.8

1

0.0045

10

34

Table 3. Number of available days in corresponding weather conditions for New Delhi, India. Type of days

Jan

Feb

March

April

May

June

July

Aug

Sep

Oct

a

3

3

5

4

4

3

2

2

7

5

6

3

47

b

8

4

6

7

9

4

3

3

3

10

10

7

74

c

11

12

12

14

12

14

10

7

10

13

12

12

139

d

9

9

8

5

6

9

17

19

10

3

2

8

105

Total days in year =365

35

Nov

Dec

Total

Highlights  The study has been done on comparison of five different solar cell material for evaluation of

thermal gain as well as electrical gain.  Mass flow rate and number of desired collectors for N PVT-CPC collector has been

optimized.  The comparative study of solar cells for partially covered N-PVT-CPC collectors has been

analyzed on annual performance.

36