Concentrated Photovoltaic Thermal Collector Research Articles

Development and evaluation of an electro-Fenton-based integrated hydrogen production and wastewater treatment plant coupled with the solar and electrodialysis units

The development of plants for the simultaneous production of green energy and clean water, in addition to improving the energy system performance, can facilitate the achievement of sustainable development. Meanwhile, hydrogen is one of the promising fuels that can overcome the intermittent penalties of renewable energy sources. In addition, due to environmental restrictions, the industry is forced to effectively treat wastewater for reuse. This article describes the evaluation of an economic model and optimization of an integrated hydrogen production and wastewater treatment plant based on an electro-Fenton process (EFP)-based photoelectrochemical stack (PES), a solar unit, and an electrodialysis unit. The wastewater supplied to the plant is the effluent of a textile factory. In addition, a concentrating photovoltaic thermal collector (CPVT) has been used as a solar unit in the plant. In the offered plant, the electrodialysis unit is able to produce the required alkaline and acid of the PES unit as well as desalinated water. The developed economic model is based on estimating the cost of hydrogen production per kilogram of hydrogen output (i.e., Levelized Cost of Hydrogen, LCOH) on a large scale plant (1072 kg H2/day). In this regard, approximately 230 m3/day of wastewater from the textile factory is treated. Relying on the proposed process can minimize the external chemical requirements of the hydrogen production and wastewater treatment plant. The value of LCOH for the planned plant was estimated to be 5.16 USD/kgH2. However, under the developed optimization, the LCOH value can be declined by almost 7.6%. According to calculations, the profitability of the wastewater treatment process can be approximately 0.082 M USD per year. It was also found that, the value of LCOH exhibits the most sensitivity to variations in operating capacity factor and the least sensitivity to variations in utilities consumption rate. A sensitivity analysis is also developed to identify effective solutions in evaluating the economic performance of the planned plant.

Energy exergy and economic evaluation of a CCHP configuration powered by CPVT collectors dynamically

This study presents a dynamic simulation of a combined cooling, heating, and power (CCHP) configuration powered by concentrating photovoltaic thermal (CPVT) collectors. The desired configuration comprises CPVT collectors, a phase change material (PCM) storage tank, an organic Rankine cycle (ORC), an absorption chiller, and heat exchangers. The evaluation has been carried out for a residential building using EES, MATLAB, and TRNSYS software. Moreover, an auxiliary heater has been used to provide the thermal energy of the desired configuration in case of low or no solar irradiation. The desired configuration has been evaluated from energy, exergy, and economic points of view during the warm months of the year (May to September). Also, the influences of key parameters of the desired system such as the CPVT area, CPVT flow rate, and PCM melting temperature on the performance of the desired configuration have been examined. The results indicate that the solar fraction enhances by about 161 % when the CPVT area changes from 100 m2 to 400 m2. Also, CPVT has found to be the main contributor to exergy destruction, accounting for 49% of the total. The maximum energy and exergy efficiencies of the desired configuration are obtained at the CPVT area of 400 m2 with values of 72.26 % and 79.03 % respectively. On the other hand, the lowest payback period occurs at 100 m2 with value of 11 years.

Optical Modelling of a Fresnel Mirror Field for the Development of a Spectral Splitting CPVT Collector

Concentrating photovoltaic thermal (CPVT) collectors could contribute to supply renewable mid-temperature heat and electricity simultaneously, e.g. for applications in the industrial sector. Although CPVT can be still seen as a niche technology, it has a high potential for the future. One of the technological challenges of CPVT are the contradictory temperature requirements within the receiver, as the thermal part should provide temperatures as high as possible, while the electrical part consisting of conventional PV cells shows best efficiency at low temperature. Therefore, this research work focuses on the development of a CPVT collector with integrated Spectral Splitting, which is an approach to overcome the discrepancy of internal temperature demands. The basis for the developed CPVT collector is a Fresnel mirror field consisting of 28 mirror stripes and providing a gross area of 13.34 m². The presented paper describes the optical modelling of this Fresnel mirror field, which was necessary before working on the receiver design in order to yield the dimensions of expected focus image on the receiver input plane. Furthermore, the resulting concentrated irradiance is a major parameter for calculating thermal and electrical efficiencies of the system, thus, this was another target for the modelling work. The optical model for the Fresnel mirror field was developed in MATLAB™ in a general way, as the number of mirrors and all geometric parameters are set as input variables. This makes it possible to use it not only for the available mirror field, but also for the design and optimisation of any other Fresnel mirror system. The model calculates the single mirror angles depending on the sun position and considers all four mechanisms of internal shading that are typical for such concentrators. Furthermore, the cosine losses in transversal and longitudinal direction are calculated. The results of the modelling are satisfying, as the experimental validation on the present mirror field was successful. The model provides comprehensive outcomes like the geometric efficiency depending on the sun´s elevation angle, the mean geometric efficiency at varying geometric parameters, local and mean irradiance in the receiver input plane, as well as mean irradiance and total solar input depending on time.

Performance Evaluation of Novel Concentrating Photovoltaic Thermal Solar Collector under Quasi-Dynamic Conditions

Concentrating Photovoltaic Thermal (CPVT) collectors are suitable for integration in limited roof space due to their higher solar conversion efficiency. Solar sunlight can be used more effectively by CPVT collectors in comparison to individual solar thermal collectors or PV modules. In this study, the experimental investigation of a novel CPVT collector called a PC (power collector) has been carried out in real outdoor conditions, and the test set-up has been designed based on ISO 9806:2013. A quasi-dynamic testing method has been used because of the advantages that this method can offer for collectors with a unique construction, such as the proposed collector, over the steady-state testing method. With a quasi-dynamic testing method, it is possible to characterize the collector within a wide range of incidence angles and a complex incidence angle modifier profile. The proposed novel collector has a gross area of 2.57 m2. A maximum power output per collector unit area of 1140 W is found at 0 °C reduced temperature (1000 W/m2 irradiance level), while at a higher reduced temperature (70 °C), it drops down to 510 W for the same irradiance level. The data have been fitted through a multiple linear regression method, and the obtained efficiency curve coefficients are 0.39, 0.192, 1.294, 0.023, 0.2, 0, −5929 and 0 for Kθd, b0, c1, c2, c3, c4, c5 and c6, respectively. The experimental characterization carried out on the collector proved that the output powers calculated by using the obtained parameters of the quasi-dynamic testing method are in good agreement with experimental points.

Performance Assessment of Coupled Concentrated Photovoltaic-Thermal and Vacuum Membrane Distillation (CPVT-VMD) System for Water Desalination

Numerical simulations were carried out to assess the technical and economic feasibility of a solar water desalination system that has a novel hybrid Concentrating Photovoltaic Thermal (CPVT) collector coupled with a Vacuum Membrane Distillation (VMD) process. A special characteristic of this CPVT is its triangular receiver with PV cells facing the reflecting surface. This type of receiver has the advantage of generating more electricity with less PV surface area and great potential to be used to hybridize conventional parabolic thermal collectors. TRNSYS was employed to analyze the annual performance of the CPVT-VMD system evaluating parameters such as solar fraction, specific permeate production and specific energy production for different coastal cities. In the dynamic simulations, local annual weather data and specific information about the characteristics and operating conditions of a real CPVT collector and a VMD module were considered. From the parametric analysis the optimal surface area of collectors and the input temperature of the VDM module were determined. A maximum specific permeate of 218.410 m 3/m2VMD for Acapulco, MX, and a minimum of 170.365 m 3/m2VMD for Singapore, SG, were achieved for the proposed CPVT-VMD system of four solar collectors with an operating set temperature of 55 °C. An economic profit was found after 7 years for Acapulco city, which showed great potential to use solar energy from hybrid CPVT collectors for a VMD process to provide freshwater in coastal cities.

Energetic and Exergetic Analyses of Experimentally Investigated Hybrid Solar Air Heater

Solar energy is a type of renewable energy that is readily available, but it must be converted to a usable form using a highly efficient method. The global energy problem that has surfaced in recent years shows the importance of both practical and scientific studies on using solar energy for space heating. Solar air heaters are large volume systems used for space heating. Research on the geometry and surface forms of solar air collectors is focused on reducing system volume and optimizing the use of solar energy. A photovoltaic (PV) module can be cooled with a fluid to prevent a decrease in efficiency due to heat while generating electrical power. The subject of this study is the idea of using the heat from cooling the modules to support a solar air heater. The improvement of the thermal performance of a solar air collector with a cooling thermal load of the concentrated photovoltaic thermal collector (CPV/T) was experimentally investigated. The heat exchanger, which removes the heat of the water-ethylene glycol circulating in the photovoltaic thermal collector, is mounted in the solar air heater’s chamber of one of the two identical solar air heaters, and the first hybrid unit was obtained (i.e., first unit). The ordinary one was called the second unit. Heated air left the first and second units at average temperatures of 45.87°C and 38.83°C, respectively. Although the airflow rates in the units are the same, the air temperature in the first unit was increased by 18.13%. The heat contribution of the heat exchanger to the first unit was 128.96 W. The first and second law efficiencies of the first and second units were calculated as 51.89%, 15.22%, and 45.4%, 10.34%, respectively. The energetic and exergetic improvement of the first unit was found to be 6.49% and 4.88%, respectively. The local solar utilization capability is 797.76 kW·h/year and 609.12 kW·h/year for the first and second units, respectively. The waste heat from the CPV/T collector cooling cycle, which is 188.64 kW·h/year, was recovered for heating air in the first unit. The recovery of waste heat for use in the first unit provided a significant performance improvement over the second unit. The environmental contribution of the waste heat recovery means 144 kg CO2 emission per year less in emission release.

Novel design of concentrating photovoltaic thermal collector – A comparative analysis with existing configurations

The aim of this paper is to propose a novel concentrating photovoltaic thermal (CPVT) collector based on parabolic trough concentrator with a semi-cylindrical receiver, and provide a comprehensive comparative analysis of the proposed configuration with the main existing CPVT collectors. To this end, a thermal model of the considered solar collectors is developed to investigate the impact of the receiver’s design on the collector’s performance in terms of their thermal, electrical, primary energy and exergy efficiencies. A residential building, located in the Moroccan city of Ouarzazate, characterized by its hot semi-arid climate, is considered as a case study to investigate the integration of solar collectors in air-conditioning application. A performance, economic and environmental analyses of CPVT driven cooling system are conducted by means of key indicators such as, solar coefficient of performance (SCOP), discounted payback period (DPP), levelized cost of cooling (LCOC), savings-to-investment ratio (SIR) and saved greenhouse gases (GHG) emissions.The results revealed that the proposed CPVT collector exhibited the highest primary energy efficiency with a value of 0.798. The performance outcomes of the solar cooling systems proved that a SCOP of 0.488 was achieved by the proposed CPVT collector followed by those based on the triangular, tubular and rectangular receivers with a value of 0.436, 0.406 and 0.367 respectively. Furthermore, from an economic perspective, the novel CPVT configuration has been proven to be the most cost-effective one with a LCOC, DPP and SIR of 0.129 $/kWh, 12.3 years and 1.488, respectively. Moreover, this configuration was found to be the most eco-friendly one with the lowest greenhouse gases emissions. This study could contribute to the promotion of the sustainable CPVT technology and is expected to be a guideline to select the most suitable configuration of CPVT collectors for solar cooling purposes.

Electrical Efficiency Increase in CPVT Collectors by Spectral Splitting

Concentrating photovoltaic-thermal (CPVT) collectors have to face the challenge of contrary temperature requirements in the single receiver parts. The PV cells require low temperatures to achieve high efficiency, whereas the thermal part should generate high temperatures for providing industrial heat. The approach of “Spectral Splitting” can offer a solution for compact CPVT receivers; however, a clear quantification of the expected conversion efficiency is difficult. Therefore, this paper describes a modelling methodology for obtaining electrical and thermal performance parameters for a Spectral Splitting configuration using semiconductor-doped glass combined with appropriate heat transfer fluid. The PV technologies c-Si, CIGS and CdTe are considered. The presented model yields distinct results for maximising the electrical efficiency, calculates the reduction in waste heat dissipation within the cells and assesses the impacts of concentration factor and cell temperature. An optimised configuration could be found with CIGS cells, impinged by a selected wavelength spectrum between 868 nm and 1100 nm, where the theoretical efficiency reaches 42.9%. The waste heat dissipation within the cells is reduced by 84.9%, compared to a full-spectrum operation. The depicted CPVT receiver design using bendable thin-film PV cells will be realised as a prototype in a subsequent project phase.

Thermal modelling and experimental evaluation of a novel concentrating photovoltaic thermal collector (CPVT) with parabolic concentrator

In the present study, a zero-dimensional thermal model has been developed to analyze a novel low concentration photovoltaic-thermal (CPVT) collector. The model has been developed by driving heat transfer and energy balance equations for each part of the collector and then solving all the equations simultaneously. Moreover, a Monte-Carlo ray-tracing software has been used for optical stimulations of the parabolic trough solar collector. The novel CPVT collector has been experimentally tested at Gävle University (Sweden) and the model has been validated against the experimental results. The primary energy saving equivalent to the thermal-electrical power cogeneration of the CPVT collector has been determined. The effect of glass cover removal, heat transfer fluid (HTF) inlet temperature and mass flow rate on the collector performance has been investigated. The optimum HTF mass flow rates of the collector for maximum electrical yield and overall primary energy saving were determined under specified operating conditions by considering the pump consumption. The effect of mean fluid temperature on the thermal and electrical efficiencies has been studied and the characteristic equation of the thermal efficiency has been obtained. The thermal and electrical peak efficiencies of the collector have been found to be 69.6% and 6.1%, respectively.

Comparative investigation of concentrated photovoltaic thermal-thermoelectric with nanofluid cooling

Thermoelectric modules are capable of converting heat into electric energy via the Seebeck effect. Therefore the addition of the thermoelectric generator modules (TEG) between the PV module and the absorber plate inside a concentrated photovoltaic thermal (CPVT) solar collector can be a feasible way for to enhance their electrical generation. A comparison between the CPVT only system and CPVT system integrated with TEG (CPVT-TE) is conducted using numerical simulation. Therefore CPVT-TE with water and CPVT-TE with 0.5% graphene/water nanofluid is investigated. A transient study using the finite volume method is presented, and computation is performed for all the considered solar systems for a typical sunny day and cloudy day under London climatic conditions. The CPV and the outlet fluid temperatures, as well as, the energy and exergy calculations are carried out to assess the performance of all the considered solar systems.The results reveal that the improvements in the total electrical power generated by the CPVT-TE with 0.5% graphene/water nanofluid and CPVT-TE compared to CPVT collector are 11.15% and 9.77%, respectively for the summer day, while, that for the winter day is 5.14% and 4.58%, respectively. The reductions in the thermal power provided by the CPVT-TE with 0.5% graphene/water nanofluid and CPVT-TE compared to CPVT collector are 6% and 11.76%, for the summer day, while, that for the winter day are 4.86% and 10.53%, respectively. Moreover, the total exergies generated by 0.5% graphene/water nanofluid CPVT-TE and water CPVT-TE collectors increased by 4.88% and 0.68% respectively, for the summer day, while that for the winter day are 2.99% and 0.95% respectively, in comparison with the conventional CPVT system.

Using photovoltaic thermal technology to enhance biomethane generation via biogas upgrading in anaerobic digestion

Anaerobic Digestion (AD) is identified to be a promising method to address the dilemma of solid waste recycling, and biogas produced from AD has also been identified as an important alternative to fossil fuels, pertaining to energy crisis and climate change. As the applied technology of anaerobic digestion is fixed, required thermal energy for biogas production in an anaerobic digester varies dramatically with the ambient temperature. The conventional way is to combust the biogas on the spot for heat preservation in the digester, and the additional natural gas will be needed for supplement in colder area. To mitigate the consumption of fossil fuel and increase the amount of available biogas for bio-methane production, a hybrid system by integration of Concentrated PhotoVoltaic Thermal (CPVT) collectors and biogas upgrading technology is proposed. The heat produced from CPVT collectors is for heat preservation in the digester, and generated electric power is used in the biogas plant and biogas upgrading unit for bio-methane production. The annual performance analysis indicates that, comparing with the conventional design, the new design saves 2.6% amount of natural gas consumption, reduces 48.38% amount of electricity from power grid and increases 86.08% amount of biomethane production. Besides, the new design can supply 829.4 MWh electricity to the power grid in a year. This research provides a new way to utilize biogas by integration with solar utilization technologies.

MXene based new class of silicone oil nanofluids for the performance improvement of concentrated photovoltaic thermal collector

In this research work, MXene with a chemical formula of Ti3C2 is used for the first time with silicone oil to improve thermo-physical properties of MXene based silicone oil. This paper focuses on preparation, characterization, thermal properties, thermal stability and performance investigation of new class of silicone oil nanofluids induced with MXene in three different concentrations for a Concentrated Solar Photovoltaic Thermal (CPVT) collector.The thermal conductivity of the silicone oil-based MXene nanofluids is measured using a Transient Hot Bridge (THB) 500. Viscosity is measured using a Rheometer at various temperatures including 25, 50, 75, 100, and 125 °C. PerkinElmer Lambda 750 is used to measure optical absorbance. The highest thermal conductivity enhancement is found to be 64% for 0.1 wt% concentration of silicone oil-MXene nanofluid compared to pure silicone oil at 150 °C. The viscosity of MXene with silicone oil nanofluids is found to be independent of addition of MXene nanoparticles in the silicone oil base fluid. Viscosity is reduced by 37% when temperature is raised from 25 °C to 50 °C for different concentrations of MXene with silicone oil. Silicone oil-based MXene nanofluid with 0.1 wt% concentration is thermally stable up to ~380 °C. Introducing more MXene nanoparticles into silicone oil improves electrical efficiency of PV module due to better cooling of MXene based nanofluids. Higher solar concentration is resulted in higher average temperature of the PV module. This consequently raises thermal energy gain which is useful for different applications.

Effect of packing factor on electrical and overall energy generation through low concentrated photovoltaic thermal collector in composite climate condition

In present research paper, one attempt has been carried out to show the performance of photovoltaic thermal collector with the effect of packing factor. Earlier many studies has been investigated on photovoltaic thermal collector design, parameters, climate and weather condition, exergoeconomic and enviroeconomic analysis. But here, effect of packing factor has been shown in results and it is concluded, electrical and overall exergy increases when packing factor increases, and, thermal energy and overall energy increases when packing factor decreases. Now according to demand of electrical and thermal energy, this packing factor can be optimized with collector size. In present study, the most suitable packing factor has been optimized as 0.5 where, collector area is 1 m2. At this value of packing factor, the maximum outlet water temperature with flow rate 0.01 kg/s has been observed 45 0C in a clear day, month of January at New Delhi. The maximum daily electrical, thermal, overall exergy gain have been obtained as 3.97, 1.86 and 5.83 kWh, respectively.

Techno-economic analysis of solar trigeneration system

In this work, a techno-economic analysis of concentrated photovoltaic/thermal collector (CPVT) driven desalination and cooling plant is presented. The system comprises of a CPVT collector, a humidification-dehumidification (HDH) desalination unit and vapour compression refrigeration (VCR) unit. The CPVT collector having 10 m2 aperture area and a triple junction PV panel placed at the receiver supplies required hot water to the HDH desalination system. Chilled water generated from 0.5 hp compressor operated VCR unit is supplied to the dehumidifier of HDH desalination. The process of cooling and dehumidification using chilled water result in increased desalination yield and resulting air is suitable for air conditioning purpose. The work is aimed to evaluate the annual performance of the trigeneration plant and to estimate the unit cost of fresh water and payback period. The annual performance of the plant is evaluated for the typical metrological year data for the location of Vellore, India. Results show that the annual desalination, electricity and cooling output are 4.2 m3/yr and 3.46 MWh/yr and 0.788 MWh/yr respectively. The daily average desalination and cooling output are 11.12 L/day and 2.47 kWh/day respectively. The annual electricity consumption of the solar cogeneration plant is 6570 kWh/yr. The estimated unit cost of fresh water is ¹10/L. By considering the interest rate of 9 % and total life time of the plant as 20 years, the payback period is estimated to be 6.5 years.

Assessment of the Impact of Stagnation Temperatures in Receiver Prototypes of C-PVT Collectors

Concentrating Photovoltaic Thermal (C-PVT) solar collectors produce both thermal and electric power from the same area while concentrating sunlight. This paper studies a C-PVT design where strings of series-connected solar cells are encapsulated with silicone in an aluminium receiver, inside of which the heat transfer fluid flows, and presents an evaluation on structural integrity and performance, after reaching stagnation temperatures. Eight test receivers were made, in which the following properties were varied: Size of the PV cells, type of silicone used to encapsulate the cells, existence of a strain relief between the cells, size of the gap between cells, and type of cell soldering (line or point). The test receivers were placed eight times in an oven for one hour at eight different monitored temperatures. The temperature of the last round was set at 220 °C, which exceeds the highest temperature the panel design reaches. Before and after each round in the oven, the following tests were conducted to the receivers: Electroluminescence (EL) test, IV-curve tracing, diode function, and visual inspection. The test results showed that the receivers made with the transparent silicone and strain relief between cells experienced less microcracks and lower power degradation. No prototype test receiver lost more than 30% of its initial power, despite some receivers displaying a large number of cell cracks. The transparent and more elastic silicone is better at protecting the solar cells from the mechanical stress of thermal expansion than the compared silicone alternative, which was stiffer. As expected, larger cells are more prone to develop microcracks after exposure to thermal stress. Additionally, existing microcracks tend to grow in size relatively fast under thermal stress. EL imaging taken during our experiment leads us to conclude that it is far more likely for existing cracks to expand than for new cracks to appear.

A hybrid system for power, desalination, and cooling using concentrated photovoltaic/thermal collector

ABSTRACT In this work, a mathematical modeling of a hybrid system using concentrated photovoltaic thermal (CPVT) collector integrated with combined desalination and cooling plant is presented. The hybrid system performance is analyzed throughout the day during summer (21/06/2018) and winter solstice (22/12/2018) in the geographical location of Vellore, India. The effect of meteorological variables on system performances such as hot water temperature, PV efficiency, desalination yield, chilled air temperature, and plant energy utilization factor (EUF) are analyzed. The overall plant performance is also compared with conventional solar flat plate collector driven desalination and cooling plant. The developed model is validated with experimental work. The highest EUF of CPVT driven plant in summer and winter solstice are 0.29 and 0.31, respectively. The comparative study reveals that use of CPVT collector to operate desalination and cooling plant improves the plant EUF. The highest increase in plant EUF of 49% is attained at a hot water temperature of 47.5 °C. Further, economical evaluation of CPVT operated desalination and cooling plant is carried out to estimate the unit cost of fresh water and payback period. Based on energy cost and interest rate in Vellore, India, the unit cost of fresh water and payback period are estimated to be ₹ 10/L and 6.5 years, respectively.

Numerical Modelling of a Concentrating Photovoltaic Thermal Collector

In this paper, the performance evaluation of a concentrating photovoltaic thermal (CPVT) collector is carried out. By writing energy, balance for the various components of CPVT collector, a set of nonlinear equations is obtained to calculate the temperature of different parts of the system. The electrical parameters of the CPVT collector are calculated by the four-parameter model of current-voltage. The simulation results of the present study are in good accordance with the previous studies data. The results show that with the fluid velocity increase from 0.08 to 0.43 m/s, the electrical efficiency and thermal efficiency increase by 1.05% and 2.2%, respectively. The thermal efficiency is enhanced by 9.4% as the receiver width is increased from 0.06 to 0.2 m. With the increase of diameter pipe from 0.017 to 0.06 m an increase of 2.75% and 3.9% is observed in the thermal and electrical efficiencies, respectively. The thermal efficiency has an ascending/descending trend with the increase of collector length. The increase of fluid inlet temperature from 273.15 to 363.15 K reduces the thermal and electrical efficiencies by 7.3% and 4.05%, respectively. The increase of the incident beam radiation from 300 to 1000 W/m2 enhances the electrical efficiency by 4%, while the thermal efficiency has an ascending/descending trend. The ambient temperature increase causes an increase of 5.1% in thermal efficiency. The effect of receiver width and ambient temperature on electrical efficiency is negligible.

Exergy performance assessment of a linear parabolic trough photovoltaic thermal collector

This paper presents the exergy performance assessment of a linear parabolic trough photovoltaic thermal collector. The governing equations of a concentrating photovoltaic thermal collector (CPVT) are obtained through an energy balance for the various components of the system. The electrical analysis of PV cells is carried out by a four-parameter model of current-voltage. By introducing the various exergy components in the system, the system exergy efficiency is obtained. The simulation results of present study are in good agreement with previous studies data. The results show that the exergy efficiency variation with respect to the fluid velocity and channel diameter is negligible. Increasing fluid velocity from 0.08 to 0.43 m/s increases the electrical efficiency and thermal efficiency 1.05% and 2.2%, respectively. An increase of receiver width from 0.06 to 0.2 m increases the exergy efficiency and thermal efficiency by 1.47%, and 9.4%, respectively. Increasing channel diameter from 0.017 to 0.06 m increases the thermal efficiency and electrical efficiency 2.75% and 3.9%, respectively. By increasing the collector length from 3 to 90 m initially the thermal efficiency increases to 62.5% and then decreases to 60%. The exergy efficiency has a slight change with increasing collector length. An increase of fluid inlet temperature from 20 to 90 °C increases the exergy efficiency by 8.2%. Meanwhile, the thermal and electrical efficiencies reduce by 6.5% and 3.35%, respectively. An increase of the incident beam radiation from 50 to 1000 W/m2 enhances the electrical efficiency by 6.6% and increases the exergy efficiency by 15.7%, while the thermal efficiency has an ascending/descending trend. The increase of ambient temperature increases the exergy efficiency and thermal efficiency by 7.6% and 5.1%, respectively. The impact of receiver width and ambient temperature on electrical efficiency is negligible.

Simulation and performance analysis of concentrating photovoltaic/thermal collector (CPV/T) with three-sided thermal insulation based on coupled optothermal model

The present paper is focused on drawing a high performance modeling and computation of a low concentrating collector combined into a Photovoltaic/Thermal system. A 3-D computational model based on 3D-4Rays technique and volume finite method is developed. The collector consists of a trough parabolic concentrator of a 20× concentration rate and two axis tracking system. The absorber is composed of a square duct in which Triple-junction PV cells are connected in series into its lower surface and a three-sided insulated multi-layer water channel, which acts as a cooling system introducing heat recovery capability.A steady pressure-driven laminar flow of a Newtonian fluid is assumed with constant properties inside water microchannel. This coupled model is initially used to simulate and analyze the temperature distributions within the PV cells, and then the thermal and electrical behavior of the proposed system. The results of the coupled model are compared with the analytical model in terms of thermal and electrical performances, such as PV cell temperature, electrical efficiency, and outlet water temperature. In addition, the impact of non-uniform illumination on the PV solar cells is also investigated. The results of the analysis indicated that a discontinuity of the thermal conductivity along the absorber tube duct, post shading and non-uniformities of PV cells temperature distributions causes a reduction in thermal efficiency of slightly more than 6% while significantly effecting the overall electrical performance.

Comparative thermodynamic analysis of densely-packed concentrated photovoltaic thermal (CPVT) solar collectors in thermally in-series and in-parallel receiver configurations

Abstract In this study, two densely-packed concentrated photovoltaic thermal (CPVT) solar collector configurations are optically and thermodynamically designed and analyzed and then exergoeconomically and environmentally assessed and compared. The designs are composed of parabolic dish concentrators, multi-junction photovoltaic (MJPV) cells, segmented thermoelectric generator (sTEG) couples with interconnectors, and finned minichannel heat extractors (mHXs). In configuration I, the receiver assembly components are connected thermally in-series whereas in configuration II they are connected thermally in-parallel. Geometric relations are employed to size the concentrator with design evaluations taking place with the aid of ray trace simulations. To better homogenize the reflected flux, the receiver is slightly shifted from the effective focal plane of the concentrator. Optical analysis reveals that the dish reflector is very sensitive to incidence angle deviations. It is found that the thermally in-series configuration offers an average annual exergy efficiency of 29.1% compared to 19.3% for the thermally in-parallel configuration. Both configurations offer comparable average annual energy efficiencies with a slight environmental and exergoeconomic advantage towards the thermally in-parallel configuration. The thermally in-series configuration is shown to provide a higher economic and thermodynamic value when electrical output is given preference over thermal output. The thermally in-parallel configuration, on the other hand, is favored in applications where thermal energy streams at multiple outlet temperatures are simultaneously desired, including a high-temperature thermal output. From an environmental viewpoint, both configurations are found capable of displacing a considerable amount of primary energy and CO2-equivalent emissions. While from an exergoeconomic viewpoint, for a system lifetime of 25 years, it is shown that the investment cost needs to be brought to approximately 21,000 AED for the proposed CPVT units to yield a positive lifecycle net present value (LCNPV). The annual escalation rate of electricity is observed to have a significant effect on the LCNPV of the collectors. Both environmental and exergoeconomic performance indices are shown to be sensitive to the thermal energy application meant for the CPVT collectors. Exergy analysis reveals that a drop in electrical exergy is offset by a rise in thermal exergy when higher system operation temperatures are used. The performance of both designs is simulated and compared on a monthly basis using weather data of Abu Dhabi, UAE.