PVT Solar Collectors Research Articles

A comprehensive numerical investigation of bi-dimensional analysis of PVT system using square channel absorber

Abstract This paper offers a comprehensive numerical investigation of PVT solar thermal performance using the Finite Difference Method (FDM) for both longitudinal bi-dimensional transient and steady state analysis, which is the unique aspect of this study. Likewise, a thorough analysis of the use of two distinct cooling absorber PVT solar collectors is conducted under realistic climatic conditions. The current modeling methodology can be considered a useful tool that enables rapid bi-dimensional PVT system analysis. The findings show that, in comparison to the PVT tube configuration (587 kWh/m2, 178 kWh/m2), the direct flow square channel has more yearly thermal and electrical gain outputs (608 kWh/m2, 196 kWh/m2). Furthermore, the design of directly flow channels has the advantages of easier integration and effective conduction heat transfer between the fluid and absorber panel. A good agreement between the measured and predicted data was obtained once the current results were compared with theoretical and experimental data in the literature. 

Energy and exergy analysis of a long-term nonlinear dynamic roll bond PVT solar collector model under Tunisian (North Africa) climatic conditions

Roll-bond type PVT modules drew little attention while offering a higher energy exchange area and an efficient heat transfer solution. Furthermore, comparative studies including exergetic assessment on PVT systems are very limited in the literature. In this paper, a novel and detailed nonlinear dynamic roll bond PVT model is performed under real-world weather conditions that provide reasonable and realistic system performance. By incorporating local solar, thermal, exergy, and electrical models based on five diode parameters, a thorough analysis is conducted. Likewise, a unique, rigorous exergy comparison between PV, thermal, and roll bond PVT systems is conducted. Results reveal that there appears to be a direct relationship between wind velocity and changes in ambient temperature which affect exergy efficiency. Higher irradiance and lower wind speeds lead to increased thermal losses, which lower the electrical exergy efficiency of the PV and PVT solar collectors.The exergy analysis reveals that a PVT system outperforms PV + ST, and findings show that for thermal and electrical parts, the yearly average efficiencies are 33.7 % and 12.27 %, respectively. Findings enable a fast and an accurate assessment of fill factor (FF), which is temperature-dependent, over the course of a year’s worth of PVT collector operation.

Second-law analysis of nanofluid-based photovoltaic/thermal system modeling and forecasting model based on artificial neural network

The PVT solar collectors can produce the thermal energy and power in a same frame. The improvement of the PVT's efficiency leads to reducing the system size and capital costs. To this end, this paper studied the irreversibilities of the Al2O3Cu/water hybrid nanofluid (NF) in a PVT solar collector considering two single and double serpentine channels (SS and DS). The influences of Re and nanoparticle concentration (φ) on the thermal and frictional entropy generation rates (S˙th and S˙fr) were investigated and the thermal, electrical and overall exergy efficiencies (ψth, ψe, ψov) of the PVT with SS and DS channels were compared and discussed. Based on the results, the DS channel exhibited S˙fr of almost 75 % lower than SS channel due to lower nanofluid inlet velocities and velocity gradients. In addition, S˙th for the DS channel is nearly 65 % lower and 26 % higher than that for the SS channel at Re numbers of 500 and 2000, respectively. Besides, the Re escalation from 500 to 2000 intensifies S˙fr by almost 94 % at different φs in the SS and DS channels. The increase in φ from 0 % to 1 % escalates S˙fr by almost 99.98 % times for two configuration regardless of the Re number. ψth of the DD channel is nearly 14.5 % and 12.77 % higher than that of the SS channel at Res of 500 and 2000, respectively. Besides, ψe of the PVT with the DS channel is 2.36 % higher than that with SS channel at Re=500 at four studied φs. Moreover, the maximum ψe for the PVT with the DS and SS were obtained as 22.29 % and 21.28 %, respectively, which are associated with Re=1500 and φ=0.25 %. Additionally, a predictive model was presented to determine the total entropy generation rate based in the Re and φ as the inputs.

The numerical analysis of Al2O3[sbnd]Cu/water hybrid nanofluid flow inside the serpentine absorber channel of a PVT; the overall efficiency intelligent forecasting

The improvement of overall efficiency of a PVT solar collector leads to reducing the system's size and cost. The application of single and double serpentine absorber channels in a PVT system was investigated considering the Al2O3Cu/water hybrid nanofluid (NF) within the ranges of 0–1% and 500–2000 for the nanoparticle volume fractions (φs) and Res, respectively. The results demonstrated that the double serpentine channel increases the convective heat transfer coefficient, h, and pumping power by 4.36% (or 18.12%) and 10.42% (or 29.78%), respectively, at Re number of 500 (or 2000) within the studied range of φ. The increase in φ from 0% to 1% at a constant Re leads to improving h by 17–25% for both serpentine channels. In addition, the electrical efficiency at different Re numbers improved by 2% and reaches to 15.52% for two configurations as φ escalates from 0% to 0.25% and the further increase in φ is insignificant. However, the thermal efficiencies of the single and double serpentine channels were obtained as 32–38% and 38–43% within the Re range of 500–2000. Moreover, the highest overall efficiency of the single and double serpentine channels were obtained as 84.30% and 90.47% at Re=1000 and φ=1%. Besides, the greatest PEC factor of 1.23 was obtained for the double serpentine channel at Re=1500 and φ=1% followed by PEC of 1.09 for this configuration at Re=1000 and φ=1%. Furthermore, a neural network predictive model was adopted to predict the overall efficiency of the PVT based on the Re and φ and the results showed that the model can predict the overall efficiency with high accuracy.

The entropy generation analysis of a PVT solar collector with internally needle finned serpentine absorber tube

The entropy generation in two different PVT absorbers with and without needle fins (WNF and WONF) was calculated by performing a 3 D numerical analysis. The effect of Re (500–2000) and nanoparticle concentration, φ (0–1%) on thermal and viscous irreversibilities (S˙thand S˙fr) were examined and two configurations of the study were compared. The outputs showed that, Re escalation within the studied range of φ decreases S˙th (or increases S˙fr) almost 8.74% (or 93.88%) and 10.53% (or 94.80%) for WONF and WNF configurations, respectively. In addition, the increase in φ from 0% to 1% reduces S˙th and S˙fr by 26% and 14%, respectively, for both configurations at different Re numbers. Moreover, the use of needle fins escalates S˙fr by 49.14%-54.08% and decreases S˙th by 63.03%-65.40% over the WONF at Re range of 500–2000. The more intensification of irreversibilities are observed near the channel turns and near the channel inlet.

Performance and economic analysis of a reversed circular flow jet impingement bifacial PVT solar collector

As the world shifts towards a more sustainable future, solar energy has emerged as a preeminent and economically feasible alternative to traditional energy sources, gaining widespread adoption. This study presents a reversed circular flow jet impingement (RCFJI) which aims to improve the performance of a bifacial PVT collector. An indoor experiment using a solar simulator to assess the energy, exergy, and economic efficiency of a RCFJI bifacial PVT collector. The study was carried out using a solar irradiance ranging from 500-900W/m2 and a mass flow rate between 0.01-0.14 kg/s. Energy performance-wise, the highest photovoltaic efficiency achieved was 11.38% at solar irradiance of 500 W/m2, while the highest thermal efficiency achieved was 61.4% under 900 W/m2, both obtained at 0.14 kg/s mass flow rate. Regarding exergy performance, the highest photovoltaic exergy obtained was 47.27 W under 900 W/m2 at 0.14 kg/s, while the highest thermal exergy was 9.67 W at 900 W/m2 at 0.01 kg/s. Overall, higher solar irradiance is more desirable for energy and exergy performance. Meanwhile, economic point of view, lower solar irradiance is preferable. Based on the findings, the optimal mass flow rate was 0.06 kg/s.

Mathematical modeling and experimental validation of bifacial photovoltaic–thermal system with mirror reflector

This research examines the feasibility of employing bifacial photovoltaic (bPV) panels on PVT solar collectors to improve electrical efficiency. Bifacial PVT (bPVT) collector with a V-groove mirror reflector is developed in this paper. The mathematical model is developed based on energy balance equations by using the inverse matrix method. The experimental findings are compared with the theoretical results to verify the mathematical model. The experiments on a bPVT collector are conducted at different mass flow rates and solar radiation intensities in the range of 0.032–0.092 kgs−1 and 508–820 Wm−2, respectively. The findings show that the temperature differential and bPV panel temperature decrease as the mass flow rate increases. Consequently, this adds to the increased electric and thermal energy of a bPVT collector. The theoretical findings report an overall performance of 58.2% at mass flow rate of 0.092 kgs−1 and solar radiation of 820 Wm−2. According to the experimental analysis, the highest energy efficiency obtained is 59.24% at the same parameter. In conclusion, this research contributes to the development of PVT collector system technology where the theoretical and experimental studies have proven the feasibility to integrate the bifacial PV and reflector on PVT solar collectors.

The entropy generation analysis and optimization of a water/silver nanofluid flow inside a photovoltaic thermal collector considering plain, ribbed, and porous-ribbed absorber tubes

BackgroundThe application of three (a) plain, (b) ribbed and (c) porous-ribbed absorber tube in a PVT solar collector was numerically investigated from the second law of thermodynamic points of view. MethodsThe 3-D laminar forced convection numerical analysis and optimization were performed for Res of 500–2000 and considering water/silver NF with the nanoparticle concentration ratios of 0–2%. Significant findingsThe results showed that the lowest thermal entropy generation rate (S˙th) is associated with the porous-ribbed configuration which is nearly 323% (or 253%) and 1211% (or 1059%) lower as compared to the plain (or ribbed) absorber tube. The moderate frictional entropy generation rate (S˙fr) was obtained for the porous-ribbed configuration which was 23.45% higher and 14.50% lower than that for the plain and ribbed tubes, respectively. The thermal exergy efficiency for the PVT with the porous-ribbed tube was nearly 50% and 46% higher than that with the plain and ribbed absorber tubes, respectively. However, the electrical exergy efficiency of the PVT with the porous-ribbed tube were superior to the ribbed and plain tubes only at low Res of 500 and 1000, while a reverse trend was obtained for the higher Res.

Development and performance comparison of a modified glazed CPC hybrid solar collector coupled with a bifacial PVT receiver

Innovative concentrating PVT solar collector concepts based on a CPC geometry concept were developed to outperform the asymmetric Solarus CPVT collector and therefore decrease the energy/performance gap between CPVT and PV/ST solar collectors.The updated reflector geometry proved to be the most suitable reflector geometry for CPVTs, where the electrical peak efficiency per gross area reached 10.6%, which is +16.5%rel higher than the electrical peak efficiency of the Solarus CPVT. Optical efficiencies of η0 = 62.3% and η0 = 61.8% for CPC 1 and CPC 2 have been achieved, respectively.A PV module (0.5 m2) combined with an ST solar collector (0.5 m2) system to be able to deliver the same overall energy yield as the newly developed CPVT collector (1 m2) requires on average +0.02 m2 (at 45 °C), −0.06 m2 (at 55 °C) and −0.15 m2 (at 65 °C) of installed area, for a wide range of latitudes.A CPC-PVT system to increase its competitiveness requires a material cost reduction and at the same time an increased overall efficiency. Nevertheless, the energy/performance gap between a system composed of PV + ST technologies and a CPC-PVT decreased significantly.

A New Solar Assisted Heat Pump System with Underground Energy Storage: Modelling and Optimisation

The objectives of this work are: (a) to present a new system for building heating which is based on underground energy storage, (b) to develop a mathematical model of the system, and (c) to optimise the energy performance of the system. The system includes Photovoltaic Thermal Hybrid Solar Panels (PVT) panels with cooling, an evacuated solar collector and a water-to-water heat pump. Additionally, storage tanks, placed underground, are used to store the waste heat from PVT panels cooling. The thermal energy produced by the solar collectors is used for both domestic hot water preparation and thermal energy storage. Both PVT panels and solar collectors are assembled with a sun-tracking system to achieve the highest possible solar energy gain. Optimisation of the proposed system is considered to achieve the highest Renewable Energy Sources (RES) share during the heating period. Because the resulting optimisation problem is nonlinear, the classical gradient-based optimisation algorithm gives solutions that are not satisfying. As alternatives, three heuristic global optimisation methods are considered: the Genetic Algorithm (GA), the Particle Swarm Optimisation (PSO) algorithm, and the Jaya algorithm. It is shown that the Jaya algorithm outperforms the GA and PSO methods. The most significant result is that 93% of thermal energy is covered by using the underground energy storage unit consisting of two tanks.

Numerical study of a hybrid photovoltaic/thermal PVT solar collector using three different fluids

Hybrid photovoltaic and thermal (PV/T) systems have been widely used for the combination of PV modules and solar thermal collectors to generate both electrical energy and heat at the same time. In the present work, a numerical model has been developed to simulate the performances of a hybrid photovoltaic/thermal (PV/T) solar collector. Furthermore, a comparative study has been performed between the hybrid PV/T working with three conventional working fluids; air, water, and specified nanofluid (AL2O3+ water). The obtained results show that the use of the Alumina nanofluid is the best choice to increase the heat removal, and to improve the performances of the collector with the values of 73.28%, 10.37% and 99.21% for the thermal, the electrical and the global efficiency respectively. On the other hand, the PVT collector working with air as the primary fluid is the worst in terms of electrical, thermal, and global performances with the lowest values of 9.506 %, 41.55%, and 65.315% respectively.

Experimental investigation of a CPVT collector coupled with a wedge PVT receiver

This paper presents an experimental investigation of a photovoltaic-thermal solar collector (commonly known as PVT) that generates both electricity and heat from the same gross area. PVT solar collectors, in theory, achieve higher combined electrical and heat yields. Additionally, PVT enables a thermal coupling between PV cells and a heat transfer cooling medium. Electrical and thermal outdoor testing measurements have been performed on a low concentration PVT solar collector based on a parabolic reflector geometry with a wedge PVT receiver. Several outdoor experiments have been carried out and presented, such as daily instantaneous electrical and thermal performance efficiency diagrams, as well as optical efficiency charts. Moreover, an electrical Incidence Angle Modifier (for both transversal and longitudinal directions) assessment has been performed and presented. Furthermore, an overall heat loss coefficient of 4.1 W/m2.°C has been attained. A measured thermal optical and electrical efficiency of 59% and 8% have been achieved, respectively. Additionally, the placement of the wedge receiver shown to be very sensitive to high incidence angles, as the electrical transversal Incidence Angle Modifier factor decreases significantly after reaching its electrical peak efficiency at 10°.

Performance evaluation of non-uniform illumination on a transverse bifacial PVT receiver in combination with a CPC geometry

PVT collectors co-generate electricity and heat from the same gross area, thus achieving higher combined heat and electric yields. A comprehensive evaluation has been carried out on non-uniform solar irradiation profile distributions on four symmetric low concentration CPC PVT (LCPVT) solar collector design concepts. Additionally, an electrical and thermal performance evaluation of symmetric truncated LCPVT solar collectors based on a CPC reflector geometry with a central transverse bifacial PVT receiver has been carried out, through a numerical ray-tracing model software and a multi-paradigm numerical computing environment software. A simplified thermal (quasi-dynamic testing method for liquid heating collectors described in the international standard for solar thermal collectors ISO 9806:2017) and electrical performance models were employed to evaluate the LCPVT design concepts. The evaluation was carried out for heating Domestic Hot Water (DHW) for a Single Family House (SFH) in Fayoum (Egypt), where energy yields between 351 and 391 kWh/m2/year have been achieved. The non-uniform solar irradiation assessment showed that the PV cells are exposed to high levels of radiation due to the specific reflector geometry. Furthermore, the study showed that the CPC geometries are very sensitive to the shading effect, as partial shadowing is substantial for high incidence angles.

A novel PVT/PTC/ORC solar power system with PV totally immersed in transparent organic fluid

A novel hybrid PVT/parabolic trough concentrator (PTC)/organic Rankine cycle (ORC) solar power system integrated with underground heat exchanger has been proposed. The evaporator unit consists of a transparent flat PVT solar collector and a PTC connected in series. The first transparent solar collector has transparent covers and consists of solar cells totally immersed within a pressurized transparent organic fluid that allows the solar radiation to reach the solar cells, cools them effectively, and captures all thermal losses from the solar cells. The second concentrator is a conventional one with opaque black receiver used to reheat the transparent organic fluid to higher temperatures. Both solar collectors (the PVT and PTC) perform as the boiler and superheater for the ORC. The performance of the proposed system is investigated by a steady-state mathematical model. The results show that, at design conditions, the efficiency of the PV modules stabilizes around 12%, absorber efficiency varies within 64% to 75%, and the ORC efficiency varies within 7% to 17%.

Solar combined cooling, heating and power systems based on hybrid PVT, PV or solar-thermal collectors for building applications

A modelling methodology is developed and used to investigate the technoeconomic performance of solar combined cooling, heating and power (S-CCHP) systems based on hybrid PVT collectors. The building energy demands are inputs to a transient system model, which couples PVT solar collectors via thermal store to commercial absorption chillers. The real energy demands of the University Campus of Bari, investment costs, relevant electricity and gas prices are used to estimate payback times. The results are compared to: evacuated tube collectors (ETCs) for heating and cooling provision; and a PV-system for electricity provision. A 1.68-MWp S-CCHP system can cover 20.9%, 55.1% and 16.3% of the space-heating, cooling and electrical demands of the Campus, respectively, with roof-space availability being a major limiting factor. The payback time is 16.7 years, 2.7 times higher than that of a PV system. The lack of electricity generation by the ETC-based system limits its profitability, and leads to 2.3 times longer payback time. The environmental benefits arising from the system’s operation are evaluated. The S-CCHP system can displace 911 tons CO2/year (16% and 1.4 × times more than the PV-system and the ETC-based system, respectively). The influence of utility prices on the systems’ economics is analysed. It is found that the sensitivity to these prices is significant.

Energy analysis of a thermal system composed by a heat pump coupled with a PVT solar collector

Abstract The development of heat pump technology in the tertiary sector can lead to a reduction in greenhouse emissions and enhanced exploitation of renewable energy sources, including solar energy. The present paper investigates the potentiality of an energy system equipped with photovoltaic thermal (PV) hybrid solar collectors, a storage tanks for the heat source and a heat pump for the space heating of a small office located in three different European cities. The behaviour of the heat pump according to the heat taken from the photovoltaic panels and stored in the tank has been analysed. An energy analysis was performed according to the efficiency of the heat pump and then the thermodynamic parameters of the system were evaluated. The analytical model of each subsystem of the thermal plant was developed in Matlab where hourly simulation during the period of heating season were performed. Therefore, a comparison between the results obtained for Rome, Milan and Cracow provided the heating energy demand covering rate for each of the cities in different subsystem efficiency conditions. When thermal and electrical efficiency of PVT are set respectively to 0.6 and 0.15 and the efficiency of storage unit heat exchanger is considered equal to 0.9 the heating demand covered for Rome is 70%, for Milan is 62%, while for Cracow is 47%. Those values show a good potential for supporting heat-pump based PV-T heating systems.

Electrical and thermal performance evaluation of symmetric truncated C-PVT trough solar collectors with vertical bifacial receivers

One way to reduce solar collectors’ production costs is to use concentrators that increase the output per photovoltaic cell. Concentrating collectors re-direct solar radiation that passes through an aperture into an absorber/receiver. Symmetrical truncated non-tracking C-PVT trough collectors based on a parabola and compound parabolic concentrator (CPC) geometries have been developed. The collector type has a central vertical bifacial (fin) receiver and it was optimized for lower latitudes. In this paper, the electrical and thermal performance of symmetric truncated non-tracking low concentrator PVT solar collectors with vertical bifacial receivers is analysed, through a numerical ray-tracing model software and a multi-paradigm numerical computing environment. A thermal (quasi-dynamic testing method for liquid heating collectors described in the international standard for solar thermal collectors ISO 9806:2013) and electrical performance models were implemented to evaluate the design concepts. The evaluation was made for heating Domestic Hot Water for a Single Family House in Fayoum (Egypt), where CPC geometries with a concentration factor of 1.6 achieved 8 to 13%rel higher energy yields (in kWh/m2/year) than the Pure Parabola geometries.

Performance Improvement Analysis on PVT Solar Water Collectors Connected in Series and Parallel

Performance Improvement Analysis on PVT Solar Water Collectors Connected in Series and Parallel

Transient analysis, exergy and thermo-economic modelling of façade integrated photovoltaic/thermal solar collectors

This paper presents a detailed exergetic and technoeconomic analysis of a Building Integrated PhotoVoltaic Thermal (BIPVT) system. BIPVT system, consisting of flat-plate PVT solar collectors, is integrated in the south facing façade of a non-residential high-rise building. BIPVT collectors produce: i) thermal energy for space heating purposes, by a radiant floor system; ii) Domestic Hot Water (DHW); iii) electricity. Electric air-to-water heat pumps/chillers and a condensing gas fired boiler are used as auxiliary systems for space heating/cooling and DHW, respectively. In addition, the system also includes an electricity storage system coupled to the BIPVTs in order to mitigate the effects of solar energy intermittency and to obtain a virtually grid-independent system.In order to compare the proposed BIPVT system to a conventional building, a reference building model, i.e. without BIPVTs, energy storage and radiant floor, is considered. Here, the space heating and cooling energy is supplied by air-to-water heat pumps (one for each floor), DHW is produced by a condensing boiler and electricity is supplied by the national grid. The comparison is performed for three thermal zones, well representative of the thermal behaviour of the whole building. In this paper, a detailed dynamic simulation model is developed by means of well-known tool TRNSYS 17, in order to predict the transient behaviour of BIPVT system. Energy and exergy balances are taken into account to determine, for the 1-year operation, the exergy destructions and exergetic efficiencies of each of the investigated components. The economic viability of the proposed system is also discussed and the resulted Simple Pay Back period is about 4 years. From the carried out exergy analysis, the average exergetic efficiency of electricity storage system is about 90%, whereas the condensing boiler one is close to 2% all year long. In addition, an exergy analysis on the proposed BIPVT system located in several European weather zones is also carried out, as well as a suitable exergy analysis is performed by varying the capacity of the electricity storage system. Such analyses aim to assess the weather condition and the size of electricity storage effects on the destroyed exergy and exergetic efficiency of BIPVT collectors and electricity storage, respectively. It resulted that, the highest destroyed exergy of BIPVT occurs in Larnaca (150 MWh/year) vs the lowest one in Belfast (87 MWh/year), whereas the BIPVT collectors exergetic efficiencies range from 8.4% for Larnaca to 8.8% for Belfast.

Experimental and theoretical performance investigation of asymmetric photovoltaic/thermal hybrid solar collectors connected in series

Abstract In this study five asymmetric hybrid solar collectors with flat plate receiver connected in series are investigated experimentally and mathematically through analytical expressions deriving from heat transfer and thermodynamics fundamentals. The main objective of this study is to evaluate the collectors' performance in terms of thermal energy and exergy production under various operating conditions thus the experiments are performed at open circuit mode regarding their electrical part and with water as working fluid. Concerning the theoretical analysis, the developed model combines optical, thermal and flow analysis for the determination of both first and second law efficiencies and it is validated against experimental data with an acceptable agreement being observed. Following the model validation, the performance of the collectors is analyzed in terms of thermal and exergy efficiency, thermal losses and absorber temperature. After the thermal analysis, the mathematical model is further developed so as to take into account the electrical production for the overall performance evaluation of the compound parabolic PVT solar collectors. Among the main findings, the final experimental results proved that these solar collectors connected in series work efficiently throughout the year as they are able to produce about 2.2 kW useful energy in summer, 2.8 kW in spring and 2.6 kW in autumn.