Photovoltaic Thermal Unit Research Articles

Investigation of the energy performance of thermal energy sharing for photovoltaic-thermal systems in a thermal prosumer network

This study analyzes the potential for energy saving through the integration of a photovoltaic-thermal (PVT) system with a heat pump (HP) in a community with a small-scale thermal network. An empirical study was conducted in a community to analyze and compare the performance of a HP and small-scale thermal network with hub thermal energy storage system that utilizes the surplus thermal energy produced by a PVT system installed in a residential house from other buildings with that of an existing electric hot water boiler. The energy saving analysis of the proposed system revealed that the energy consumption could be reduced by more than 70 % compared to the existing system. The HP exhibited a COP ranging between 4.2 and 4.7. Throughout the experiment, the integrated system collected an average of 23.77 kWh of heat energy daily from the PVT units. The annual domestic hot water load coverage from PVT through the thermal network was found to be 50.4 %. These results indicate that PVT systems combined with thermal networks and HPs can effectively reduce energy consumption in individual buildings and enhance energy efficiency within communities.

Critical analysis of enhanced photovoltaic thermal systems: a comparative experimental study of PCM, TEG, and nanofluid applications

Phase change materials (PCM), thermoelectric generators (TEG), and nanofluids are popular methods investigated for improving conventional photovoltaic thermal (PVT) systems. These methods are particularly used in warm climates where high temperatures negatively impact photovoltaic (PV) power output and energy efficiency. This experimental study evaluated the effects of 32 °C melting point PCM and TEG integration on PVT units, as well as 42 °C melting point PCM and nanofluid incorporation on concentrated PVT (CPVT) units. Technical, exergetic, and economic performance were compared using a small-scale PVT module. Low-cost commercially available materials were used to construct all PVT units. Industrial metal waste was introduced to enhance the thermal conductivity of paraffin wax and salt hydrate PCMs. The results indicated that applying PCMs, porous media, and concentrator plates increased energy generation, potentially offsetting their higher initial cost and achieving an energy cost of approximately $0.135/kWh. However, TEG and nanofluid implementation remained uneconomical, leading to a 15–35 % increase in energy cost. The water-based CPVT unit, enhanced with paraffin wax and copper fins, demonstrated the best technical performance. This unit achieved electrical, thermal, and exergy efficiencies of approximately 15.5 %, 37.4 %, and 16.7 %, respectively, with more than a 20 % reduction in cell temperature. The study also revealed that severe structural changes caused by corrosion of metallic materials in hydrated PCMs could alter the melting point by more than 30 %. This change negatively impacts heat storage capacity. Conversely, incorporating metal chips in non-hydrated PCMs improved the time to reach the melting point state by 30–60 minutes.

Techno-economic analysis and tri-objective optimization of a novel HDH desalination with PVT and vapor-compression chiller for sustainable water supply in remote areas

Desalination is a powerful tool for addressing freshwater scarcity. This study introduces a stand-alone desalination unit based on humidification-dehumidification, photovoltaic-thermal, and vapor-compression chiller technologies for providing sustainable water supply in remote areas. The system is evaluated from both technical and economic perspectives, and three refrigerants (R22, R134a, and R407C) are tested to determine the best option for the vapor-compression chiller. The system is comprehensively modeled using an artificial neural network trained for tri-objective optimization by employing a genetic algorithm. The optimization aims to maximize the freshwater production rate and gain output ratio while minimizing the cost rate. The results indicate that the photovoltaic-thermal unit comprises about 97% of the cost rate. At the optimum point, the freshwater production rates are 43.81 m3/day for R22, 40.56 m3/day for R407C, and 36.65 m3/day for R134a. The cost rates are highest for R407C at 48.04 $/h, followed by R134a at 45.72 $/h and R22 at 43.74 $/h. Similarly, the gain output ratio follows the same order, with R407C having the highest ratio of 1.28, followed by R134a with 1.27 and R22 with 1.24. The study concludes that R407C is the best option in terms of technical, economic, and environmental factors.

Environmental and energy analysis for photovoltaic-thermoelectric solar unit in existence of nanofluid cooling reporting CO2 emission reduction

BackgroundIt is crucial to introduce new strategies to intensify the efficiency of photovoltaic thermal (PVT) unit. The incorporation of a thermoelectric generator (TEG) within a solar unit can notably improve its electrical performance. Additionally, modifying the properties of the cooling fluid by incorporating nano-powders proves to be an effective approach in optimizing PVT systems. MethodsThis study delves into an inventive design for a PVT unit, exploring novel techniques to boost its performance. To enhance the cooling of the PV component, two strategies were employed: 1) the implementation of a new-style turbulator, and 2) the integration of confined jets. Thus, three cases were simulated: case 1 (without any enhancement), case 2 (with the turbulator), and case 3 (employing both techniques). Additionally, the TEG layer was incorporated with the PV layers to augment overall efficiency. The testing fluid, water, was infused with SiO2 nanoparticles, and their properties were determined using a homogeneous mixture formulation. For simulating the current 3D model, the Finite Volume Method was chosen, accounting for laminar flow in fluid zones and applying the pure conduction equation for solid zones. The impacts of altering geometry, heat flux (G), inlet velocity within the tube (Vi), and jet (Vj) on performance metrics (including PV electrical (ηPV), thermoelectric (ηTE), thermal (ηth), overall electrical (ηEl), total (ηTot)) have been detailed in the results section. Significant findingsBy implementing two cooling techniques, the uniformity of panel temperature experiences a notable enhancement of about 79.96 %. With an increase in the velocity of the nanofluid within the tube, there is an approximately 1.99 % improvement in the value of ηTot. Furthermore, when Vi=0.08 m/s, the values of ηEl, and ηTot see an increase of about 3.09 % and 12.59 %, respectively, upon the installation of the jet and turbulator. An augmentation in G leads to a rise in ηTot by approximately 5.32 % and 7.32 % for cases 1 and 3, respectively. When G = 810 W/m2, incorporating a jet and turbulator in the PVT system results in improvements of about 2.64 % in ηEl, and 10.45 % in ηTot. The increment of ηTot with switching from case 1 to case 3 enhances about 24.62 % with the rise of G. Moreover, as the inlet velocity of the jet increases, the values of ηTE, ηth, and ηTot enhance by about 3.43 %, 1.87 %, and 1.06 %, respectively.

Effects of self-cleaning technique and nanofluid cooling on performance of photovoltaic solar unit employing sinusoidal surfaces

The urgent need for electricity generation for both commercial and residential uses can be satisfied by photovoltaic units, but the serious flaws of these units arise from the negative effects of environmental factors like dust, shadow, radiation, and wind on their performance. The present study examines how PV panels operate under dusty conditions, using ANSYS FLUENT software and focusing on steady-state and laminar conditions. This study aims to numerically examine a three-dimensional (3-D) photovoltaic thermal (PV-T) unit with sinusoidal walls (PV-T-SW). The testing fluids examined in current paper are Al2O3-H2O nanofluid and H2O. Under the same initial and boundary conditions, three configurations were tested: a PV module, a straight channel PV-T unit, and the PV-T-SW, which are numerically compared and examined. An important element that declines the power generation efficiency is the deposition of dust on photovoltaic panels. The key novelty of the current study is that it provides a numerical modeling of the impact of dust in the presence and absence of a self-cleaning coating on a photovoltaic thermal system, as well as the optimal cooling mode and configuration. First, suitable temperature management systems are critical for achieving high-efficiency solar photovoltaics, and in heat exchange devices, the employment of corrugated structures has proven to be a helpful strategy because of the benefits of extended surface area. Finally, the electrical (ηele) and thermal (ηth) efficiency are assessed by taking into account the optical properties of dust deposition and hydrophobic coating. The factors evaluated are the impacts of varying nanofluid concentration, inlet flow Reynolds number (ranging from 500 to 1500), wavy channel amplitude, and wavelengths on cooling performance. The findings revealed that using 4 % water-aluminum oxide as an operating fluid instead of H2O improved the coefficients of heat transfer in the channel by 15.7 %. In addition, at the next step, when water-aluminum oxide was used as a coolant and the sinusoidal channel was examined with different geometrical characteristics, it was discovered that the 9 mm wavelength and 0.8 mm amplitude channel, in comparison to the simple form of the system, had superior heat transfer performance. Furthermore, the obtained data indicate that the ηele decreased by 40 % as the dust deposition happens, and it was discovered that the coating reduced that negative effect on the glass used to cover solar cells. Because of rising environmental issues and the expense of energy, thermal control of sources of energy that are renewable is becoming more and more important. The findings of this investigation can be used for future PV cooling innovation unit development and optimization.

Towards positive energy islands – a Danish case study

The Danish island of “Ærø” has the ambition of becoming the first Danish island to be self-sufficient in renewable energy and CO2 neutral by 2025, as well as fossil fuel free by 2030. This work investigates the feasibility of re-designing part of the island’s energy system to become the first Danish positive energy island (PEI), evaluating various design scenarios and opportunities for improving and modifying the current energy supply and distribution scheme. The district is modelled considering all building specifications and characteristics and the energy supply systems using the urban scale modelling tool City Energy Analyst (CEA). A simulation of the base-case scenario is performed to calibrate the performance. Different energy improvement strategies targeting building envelopes and energy generation and supply systems are created and implemented in CEA. Six improvement packages are created and simulated. It is demonstrated that a PEI could be built in the district under consideration through a comprehensive energy improvement package of envelope-targeting techniques, energy system upgrades, and the expansion of renewable energy systems. The package includes LED lighting, heat pump installation, and photovoltaic-thermal units. This will enable meeting the annual net need for electricity while producing 20% excess heat.

Techno-economic examination and optimization of a combined solar power and heating plant to achieve a clean energy conversion plant

Renewable energies are one of the best alternatives to fossil fuels, which have disadvantages such as exhaustibility and emission of environmental pollution. An alternative system consisting of a parabolic trough collector (PTC) and a photovoltaic thermal (PVT) is used to produce electric power and heating. By using the Kalina cycle and the organic Rankine cycle (ORC) coupled with the PVT unit, an attempt was made to recover as much as possible heat from the solar energy. Exergy and exergy-economic analyzes were performed on the proposed system, and appropriate criteria for evaluating the system were defined based on energy, exergy, and economic analyses. The exergy analysis results indicate that the highest exergy destruction rate in the ORC sub-system is associated with the PVT unit. The value of electrical cost for three studied cities, Doha, Tehran, and Ankara were calculated. Results present that the highest and lowest net output power were for Doha and Ankara and these cities also have the maximum and minimum electrical cost. In addition, using multi-objective optimization, the optimum states of introduced system in the Pareto diagram are presented and with the help of ideal point concept, the final optimum state is determined.

Thermodynamic investigation of novel hybrid plant with hydrogen as a green energy carrier

In this research, two thermodynamic cycles based on gas turbine (GT) have been thermodynamically modeled and compared. The basic cycle is a Brayton cycle with thermoelectric and a supercritical carbon dioxide cycle. In the proposed system, a supercritical carbon dioxide cycle with photovoltaic thermal (PVT) unit and a Kalina cycle have been added to the existing system to recover more dissipated heat from GT unit. Thermodynamic modeling of the mentioned cycles has been done with Engineering Equation Solver software. For each component of the systems, mass, energy and exergy balance has been carried out. Also, appropriate relationships are defined for evaluating systems. The results of energy analysis of the systems show that the proposed plant produces net power 33585 kW and the fuel flow in the combustion chamber is 1.67 kg/s. Also, the employed electrolyzer produces 16.90 kg/day of hydrogen. Also, the analysis of the second law showed that although the proposed system produces 18320 kW power more than the base cycle, it has more exergy destruction rate by about 1912 kW. The proposed system has energy and exergy efficiency by about 1.34% and 1.93% more than the basic system. The results of the exegy analysis also make it clear that the combustion chamber and PVT unit have the lowest exergy efficiencies. The parametric analysis indicated that the compressor pressure ratio and gas turbine inlet temperature have important influence on the overall performance of the system, while the effects of the working pressure of both supercritical carbon dioxide cycles are insignificant.

Insight into the investigation of Fe3O4/SiO2 nanoparticles suspended aqueous nanofluids in hybrid photovoltaic/thermal system

This experimental study aims to evaluate the energetic performance of a photovoltaic-thermal system with a serpentine tube collector. A photovoltaic-thermal unit with a serpentine tube collector is used to compare the unit's performance metrics to those of a PV panel without cooling. The considered heat transfer fluid is the hybrid nanofluid prepared using water and Fe3O4/SiO2 nanoparticles. Using irradiance data from an average day in Aligarh, India, the experiment is conducted in indoor environment in a solar simulator under regulated operating circumstances. Effects of mono and hybrid nanofluids are examined at 3% wt. concentration for varying flow rates (20, 30, 40 LPM). The experimentation analysis showed that the maximum drop in PV temperature at 20 LPM is 25 °C, 24 °C, and then 16 °C for Fe3O4/water, SiO2/water, and Fe3O4/SiO2 nanofluids-based PVT systems, respectively with a highest possible increase in electrical efficiency of 12.6 percent, 18.46 percent, and 24.34 percent, respectively, when compared to traditional PV systems. At a flow rate of 40 LPM, the best performance is obtained using a hybrid PVT method coupled with an aqueous Fe3O4/SiO2 nanofluid. Additionally, it is discovered that hybrid nano-fluid-based PVT systems exhibit 10.5% and 5% greater thermal efficiency than Fe3O4-Water and SiO2-Water PVT systems, respectively. The overall highest efficiency of 67% is achieved for hybrid nanofluid at a flow rate of 40LPM. The hybrid Fe3O4/SiO2 nanofluid is capable of serving as an acceptable cooling fluid for the PV/T collector, as evidenced by the PV/T system's notable improvement in thermal and electrical efficiency and prominent cooling impact. Keywords : Solar energy, Hybrid nano-fluid, Heat transfer, Electrical Power, Thermal Efficiency, PVT system. • The role of hybrid nanofluids for the performance of PVT systems was studied. • Hybrid nature of nanofluid make it more stable than mono-nanofluid. • Electrical and thermal efficiency were analysed at fixed concentration and varying flowrate. • Comparison of Fe 3 O 4 /SiO 2 nanofluid is carried out with individual mono-nanofluid.

Seasonal performance comparison analysis of the roll-bond photovoltaic thermal heat pump system in a multi-energy generation: An experimental study

Solar photovoltaic thermal heat pump systems contribute significantly to the building industry's goal of energy efficiency and “carbon neutrality” by producing multiple types of energy from the intensive use of solar energy to meet the varied and dispersed energy requirements of modern buildings. An experimental investigation of the roll-bond photovoltaic thermal heat pump system powered by a roll-bond photovoltaic thermal unit is presented in this study, together with the system's precise operating principle and the structural design of the unit. The theoretical underpinnings of experimental research are discussed, including the establishment of test platforms and error analysis, as well as the method for evaluating system performance, which includes solar power, heating, and cooling. Following that, continuous experiment monitoring under various weather conditions in Dalian is carried out throughout the year, which serves as the basis for system performance evaluation and comparison, with a focus on heating, power, and cooling. Comparison analysis results show that the heating and power generation performance in the summer season is the highest, with an average photovoltaic efficiency of 13.6% and an average heating coefficient of performance of 6.16, which is followed by the transition season and winter season, with an average photovoltaic efficiency and heating coefficient of performance of 11.9% and 6.05, 10.2% and 4.54, respectively. However, the performance of power and heating cogeneration in summer conditions fluctuates due to variations in solar radiation intensity. Furthermore, the system can run in cooling mode during the night, on overcast days, and on rainy periods to generate cooling capacity. The cooling performance is the highest during clear nighttime, followed by the overcast nighttime and overcast daytime, with an average cooling coefficient of performance of 2.99, 2.66, and 2.12, separately. Rain, as a cooling water source, significantly improves system cooling performance. The results show that the proposed roll-bond photovoltaic thermal heat pump system can generate high-efficient multi-energy under a variety of weather conditions while remaining stable over time, providing a valuable practical feasibility reference for renewable energy utilization in buildings in northern China.

Experimental study of a nanofluid-based photovoltaic/thermal collector equipped with a grooved helical microchannel heat sink

• Energetic and exergetic performances of a nanofluid-based PVT unit are assessed. • The unit is equipped with a grooved helical microchannel heat sink. • Aqueous suspension of magnetite nanoparticles is considered as coolant. • The Staggered PVT unit performs better that the parallel and plain PVT units. • Energetic and exergetic performance of units intensify with boosting Φ nf and M nf . Helical geometry is widely used in heat transfer systems due to the high heat transfer surface and the creation of swirling flow. Grooving the spiral channel can lead to the strengthening of these effects and improve the channel performance. In the present study, the energy and exergy performance of a nanofluid-based photovoltaic thermal unit equipped with a grooved helical microchannel heat sink is investigated experimentally. For this purpose, a plain helical microchannel heat sink, a parallel grooved helical microchannel heat sink and a staggered grooved helical microchannel heat sink are designed and fabricated. The employed nanofluid is the aqueous suspension of Fe 3 O 4 nanoadditives. The experiments were performed at different values of flow rates (20–80 kg/h) and nanoadditive concentrations (0.0–2.0 %). The highest thermal energy/exergy, electrical energy, and their corresponding efficiencies have been recorded at the mass flow rate of 80 kg/h and nanoadditive concentration of 2.0 %. It is seen that the overall energy efficiency of the staggered unit is 17.05 % and it is 6.96 % higher than the plain and parallel unit. Further, the staggered unit demonstrated the highest exergy efficiency (14.67 %) compared to other studied photovoltaic/thermal units.

Numerical study on the performance of photovoltaic thermal unit condenser with water/nanofluids as fluids medium

To fully exploit the use of water/nanofluids in the photovoltaic thermal (PVT) unit condenser and further increase renewable energy resources in energy mix, the current paper numerically studies the effect of operating water/PVT unit, Al3O2-water/PVT unit and Ag-water/PVT unit on the overall performance. In the ANSYS Fluent 18, the mathematical equations related to these models were discretized by the second order upwind scheme and solved at steady state, considering the fluid inside pipe as laminar flow. The results were obtained and discussed in terms of coefficient of performance (COP), Nusselt number (Nu), specific exergy (Ein,out) and outlet flow temperature (Tout), at different nanoparticle fractions and operating conditions of both flow and weather. A higher inlet mass flow rate of nanofluids (Ag-water and Al3O2-water) was recommended both for better COP and handling nanoparticles deposition problem. In addition, due to thermal conductivity difference, the maximum COP of about 3 was achieved from PVT unit condenser with Ag-water as fluid medium. The optimum conditions of flow and weather were proposed for the operation of three considered PVT units condenser.

Exergy studies in water-based and nanofluid-based photovoltaic/thermal collectors: Status and prospects

A hybrid solar photovoltaic-thermal collector is the combination of a solar thermal unit and a photovoltaic panel for the simultaneous generation of heat and electricity. In these systems, a fluid is used to cool photovoltaic panels and, thus, prevent their reduction of electrical efficiency. The hot fluid leaving the system can also be used in various kinds of engineering applications, from agriculture to heating, ventilation and air conditioning units, and process heat in utilities. Coolants used in photovoltaic-thermal units include air, water and nanofluids, among which air is less efficient than water and nanofluids due to its low specific heat capacity. Although extensive research has been done on the exergy performance of photovoltaic-thermal units, the number of published review articles in this field is very limited. This paper presents a critical review with some recommendations for future research on the topic of exergy examination of water-based and nanofluid-based photovoltaic-thermal units. As a first step, the concept and mathematical exergy relations are introduced. Then, water-based and nanofluid-based photovoltaic-thermal units are exergetically discussed in detail, followed by the description of novel units. At the end of each section, some suggestions are presented for future exergy examination of those types of photovoltaic-thermal units.

Application of hybrid nanofluids in a novel combined photovoltaic/thermal and solar collector system

Because of the low outflow temperature of the conventional photovoltaic thermal systems and lack of electrical production of the solar thermal collectors, a novel combined system is proposed to solve the two mentioned drawbacks. This novel system is achieved by connecting a photovoltaic thermal unit to a solar thermal collector in series. To increase the overall performance of this novel combined system, different hybrid nanofluids include (1) multiwall carbon nanotube-aluminum oxide (2) multiwall carbon nanotube-silicon carbide (3) graphene-aluminum oxide, and (4) graphene-silicon carbide are compared. The investigation is performed based on the three-dimensional simulation, and the Eulerian-Eulerian model is selected for the simulation of hybrid nanofluids. To estimate the performance of this novel combined system, the first and second laws of thermodynamics are used. Moreover, the share of entropy generation in all components of the system is calculated. The results indicate that the multiwall carbon-silicon carbide hybrid nanofluid with the average electrical and thermal energy efficiency of 13.85% and 56.55%, respectively, has the best performance compared to other fluids. Furthermore, in the combined system, different components of the solar collector produce more entropy generation than the components of the photovoltaic thermal module.

Numerical investigation on the performance and environmental aspect of roll bond photovoltaic thermal unit condenser incorporating fins on the absorber

To contribute to the sustainable energy production, the current paper proposed and numerically solved a model of roll bond photovoltaic thermal (RB-PVT) condenser with fins by using ANSYS Sotfware18. First, the effect of four different fin shapes and number was analyzed to determine the fin shape and number best suit for the study. Last, on the basis of RB-PVT unit condenser with 3 fins of straight rectangular shape, a sensitivity was conducted considering fin length and width in the range of 0.2–0.7 mm, and 195⁰-255⁰ and 345⁰-285⁰ for the position of fin on left and right side of the fixed one, respectively. The highest average values in heat dissipation flux, pressure drop and overall fin efficiency were respectively obtained to be 1792.693 W/m2, 86.471 kPa and 79.767% when varying fin(s) width and angle. In addition, the average refrigeration coefficient of performance (COP) of 5.079 and which is higher than that of previous studies was achieved. Meanwhile, the maximum average of 258.07 united state dollars (USD) would be saved to capture and store 8.603 tons of emissions (CO2), after every 5 years. RB-PVT unit with fins not only can improve the system performance but also can help achieving a clean environment.

Review on poly-generation application of photovoltaic/thermal systems

The efficiency and life cycle of photovoltaic cells reduce by increasing the working temperature, and nearly 50% of incoming sunlight that hits the solar cells convert to heat. Therefore, the thermal management of solar cells is essential. Several studies were conducted on develop, design, and fabricate systems that could satisfy this issue. Among them, the photovoltaic/thermal (PVT) systems currently are the most promising solution. The combination of the PV unit and collector forms a PVT unit that can simultaneously increases the electrical yield of the PV cell and generates heating for deferent applications. In the present paper first, details of PV construction and the influence of temperature on PV module were reviewed, and then several researches relevant to PVT systems are summarized and categorized them based on their types such as concentrating PVT, flat PVT, and Bi-fluid PVT systems and the kinds of coolant they employed such as air, water, glycol, and various type of nanofluid. In order to harvest the maximum thermal energy and electricity, this review paper emphasized on employing PCMs and nanofluids. Furthermore, the paper presents an exergy evaluation and uncertainty energy analysis for the PVT systems along with energy balance for each layer of the PVT collector. This review also presents the economic assessment and environmental evaluation of PVT systems and introduces the main application of the PVT system. The purpose of this investigation is to provide necessary information for the development and design of novel and efficient PVT systems.

Performance Comparison and Analysis of the Curtain-Wall-Type Liquid-Type Photovoltaic Thermal Unit According to the Pipe Connection Method

Recently, there has been increasing attention on the use of renewable energy in buildings, particularly, the photovoltaic thermal (PVT) system that uses both solar power and thermal energy. However, there is a limit to adopting the PVT system in real buildings because many architects value the aesthetics of buildings or spaces. This study developed a curtain-wall-type liquid-type PVT (CW-PVT) that can be installed on a wall as it integrates with the building. To analyze the system performance, a real-scale experimental plant was established in an outdoor environment. The performance of the CW-PVT unit was verified for two different module pipe connection types: parallel and serial. Meteorological variable data, the inlet and outlet fluid temperatures, surface temperature, and electrical energy generation of the modules were measured and collected using the measurement equipment according to the module pipe connection type. Consequently, the parallel-type method was approximately 10% more efficient than the serial type in energy production, whereas the serial-type method produced water with a temperature approximately 47% higher than that of the parallel type. Notably, it was advantageous to apply the parallel-type connection to maximize the energy generation efficiency in buildings where the system efficiency is vital and the serial-type connection in buildings where the high temperature of hot water is required.

Performance improvement of a desiccant based cooling system by mitigation of non-uniform illumination on the coupled low concentrating photovoltaic thermal units

A Low Concentrating Photovoltaic Thermal system typically employs compound parabolic concentrator to focus sunlight and enhance the quality of both thermal and electrical energy extracted. One of the major issues during this process is the introduction of non-uniform illumination on the photovoltaic panels which can cause hot-spots and significantly reduce both the reliability and the electrical output from this system. This non-uniform illumination can be mitigated by integrating homogenizers which are typically linear extensions to the compound parabolic concentrators profile also referred to as elongated compound parabolic concentrators. In this work, the performance of a 2.5× Elongated Compound Parabolic Concentrator truncated to 1.7× and connected to a desiccant based cooling system has been explored. For a detailed analysis of the system, a coupled 3-D optical, electrical, thermal and process efficiency model has been developed. A full-scale prototype of the modelled system is also fabricated using a 380-Watt peak photovoltaic panel. Experiments conducted on the developed system showed a peak outlet water temperature of 56 °C at a mass flowrate of 24 L per hour. Comparative studies between compound parabolic concentrators and elongated compound parabolic concentrators based low concentrating photovoltaic thermal system is also presented to showcase the overall improvement in the process efficiency due to the mitigation of non-uniformity. Using a 400 mm length of the homogenizer the spatial non-uniformity factor was found to drop from 0.5 to 0.29 under normal incidence angle and results in a rise of 12% in the electrical output when compared to a compound parabolic concentrators-based system. The coefficient of performance of the desiccant-based air-cooling system is found to increase by 50% when coupled with two series-connected elongated compound parabolic concentrators based low concentrating photovoltaic thermal system. The improvement in coefficient of performance is mainly because of thermal and electrical energy savings from the developed system amounting to 352 kWhe/year and 665 kWhth/year, respectively. Further, the mitigation of non-uniform illumination showed a performance improvement of 5% in the coefficient of performance of the air-cooling system compared to a compound parabolic concentrators-based system.

Assessment of photovoltaic thermal unit equipped with phase change material in different finned containers

In present research, PVT unit combined with paraffin in multiple finned containers is simulated and evaluated. The role of various types and numbers of fins from thermal and electrical perspectives is analyzed. Also, the influences of a) fin utilization, b) fin quantities, and c) fin configurations on the different system parameters are evaluated. The numerical approach is employed to model the PVT/PCM unit. The outcomes reveal that growing the number of fins facilitates the heat transmission into PCM, enhances the rate of melting, and declines the average surface temperature. The surface temperature (in the case of T-shaped fin) in the system with 10 fins reaches 309.6869 K which is 5.03%, and 13.31% less than the average surface temperature of systems with 6 fins and without fins, respectively. The liquid fraction in container with 10 fins reaches 46.83% which is 4.05% and 10.60% higher than value of liquefied fraction in PVT/PCM systems with 6 fins and without fins, respectively. Regarding the achieved results, adding nano-powders to paraffin, augment the liquefied fraction by 2.13% compared to pure PCM.

A new solar atmospheric water harvesting integrated system using CPV/T – Stirling engine – Absorption cooling cycle and vapor compression refrigeration cycle

This research theoretically investigates the performance of a new integrated solar atmospheric water harvesting system. The system consists of a concentrated photovoltaic thermal unit (CPV/T) to capture solar radiation and produce electricity. The rejected heat is utilized to drive an alpha-type Stirling engine and a single effect LiBr/H2O absorption cooling cycle (ACC). The power output of the Stirling engine and the CPV/T is used to drive a vapor compression refrigeration cycle (VCRC), whereas the cooling capacity of the cooling cycles is used to cool and dehumidify ambient air and generate potable water. Moreover, a heat recovery heat exchanger is employed to pre-cool the supply air before entering the evaporator, thus increasing the water production rate. The model is validated and solved numerically. A parametric study is conducted to show the effect of a variety of ambient and operating conditions on the system's performance. The highest water production rate is found, as expected, to be in hot and humid climates where the solar radiation, the ambient temperature, and the relative humidity are high. The freshwater production exhibits a non-monotonic behavior with increasing the air mass flow rate, and the maximum potable water production was identified. At solar radiation values of 0.6, 0.8, and 1 (kW/m2), the maximum water production was generated at air mass flow rate values of 1.6, 2.8, and 3.8 (kg/s), and the corresponding maximum water production were 13.37, 20.12, and 26.28 (L/h), respectively. It is found that this integrated system can produce up to 30 L/h under hot and humid ambient conditions, and pre-cooling of the supplied air yields better performance under drier conditions. The proposed system is suitable for small-scale applications where water demand is less than 180 L/day. It is found that the amount of electrical energy consumed per liter of produced water by this system is between 225 and 315 Wh/L approximately.