PVT Systems Research Articles

Exergy-rational utilization of solar energy with advanced PVT systems and heat pipe technology in 100% renewable cities

This paper responds to the EU goals of decarbonization with solar energy leading to fifth-generation district energy systems (5DE). The dilemma of low-exergy (low-temperature) district heating systems with renewable and waste thermal sources and the temperature-incompatibility of the current comfort heating equipment demanding higher supply temperatures is addressed. Until innovative, low-exergy equipment and higher-exergy solar photo-voltaic-heat systems are developed, various methods of optimum temperature peaking and existing equipment oversizing are presented. Central temperature peaking at the plant site and the individual prosumer buildings are compared. A case study is presented, which involves an individually optimized solar prosumer building with an optimum mix of heat pump oversizing and commercial radiator oversizing. Results show that CO2 emissions responsibility-based optimum mix compared to economy-based optimum mix reduces the responsibility by 30%. This analysis was repeated by cascading two smaller heat pumps instead of a larger one to increase the overall COP. This change further improved the solution by 4% points. Results have also been compared to a modified case where cascaded heat pumps are coupled with low-exergy heat pipe radiators. This coupling resulted in much more improvement by an additional 52% points. The paper concludes that the key is low-exergy heating and cooling equipment. Then the fifth-generation district energy systems with supply temperatures as low as 320 K (47°C) and return temperatures as low as 300 K (27°C) will be possible with renewable and waste energy sources if the one-way distance between the plant and the district is not more than 1.6x10-5 km/kW times the thermal capacity of the district raised to a power of 1.5.

Thermodynamic analysis of a photovoltaic thermal system coupled with an organic Rankine cycle and a proton exchange membrane electrolysis cell

In this study, the performance of a Photovoltaic Thermal-Organic Rankine Cycle (PVT-ORC) system combined with a Proton Exchange Membrane Electrolysis Cell (PEMEC) is investigated. A combined numerical/theoretical model of the system is developed and used to evaluate the effect of various system design parameters. In addition, the effects of using water, ethylene glycol, and a mixture of water and ethylene glycol (50/50) as the working fluid of the PVT system and R134a, R410a, and R407c as the working fluid of the ORC cycle on the performance of the PVT-ORC-PEMEC system are studied. Based on the results, R134a and water demonstrated the best performance as the working fluid of the ORC and PVT systems. Moreover, the electrical efficiency of the combined PVT-ORC system is 15.65% higher than the electrical efficiency of the conventional PVT system. Also, the maximum hydrogen production rate of the proposed PVT-ORC-PEMEC system is calculated to be 1.70 mol/h.

Energy and Life Cycle Assessment of Zinc/Water Nanofluid Based Photovoltaic Thermal System

Cooling the PV surface in a Photovoltaic Thermal system is a pivotal operational aspect to be taken into account to achieve optimized values of performance parameters in a Photovoltaic Thermal System. The experimental design used in this study facilitates the flow of varying concentrations of Zn-water nanofluid in serpentine copper tubing installed at the rear of the PV panel thereby preventing the PV surface temperature from increasing beyond the threshold value at which a decrease in electrical efficiency starts to occur. This fusion of solar thermal with PV devices leads to better electrical and thermal efficiency values resulting in decreased cell degradation over time and maximization of the lifespan of the PV module and the energy output from the PV system. Due to the superior thermal heat properties of nanofluids, their usage in such systems has become increasingly widespread. Life cycle metrics which include Energy Payback period, Energy Production Factor and life cycle conversion efficiency were evaluated for the PVT system by exhaustively chalking fundamental parameters such as embodied energy of the PVT setup and the total energy output from the PVT system. This research aims to be a major milestone in the evolutionary journey of Photovoltaic Thermal modules by guiding the engineers working on the theory, design and implementation of PVT systems towards its economic feasibility, environmental impact and energy sustainability.

Overview on Recent PVT Systems with Jet Impingement

Jet impingement cooling has been utilized to improve the performance of solar energy technologies such as solar collectors, PV systems, PVT systems, and CPV systems. This article provides an overview of current PVT systems using jet impingement. The distinctions between each study, such as research results and PVT system design, are examined and contrasted. The summary demonstrates that solar collectors are the most widely utilized solar energy technology owing to their direct manufacture. There are 20 solar collector studies, 5 for photovoltaic, 9 for photovoltaic thermal, and 8 for concentrator photovoltaic. Geometric characteristics such as jet diameter, spacing, and nozzle height are critical for maximum performance. Furthermore, numerous kinds of coolant jets, such as air, water, and nanofluid, may be seen from the overview. Hybrid systems, such as PVT or CPVT systems, perform better since they create thermal and electrical energy. As a result, more research into developing the hybrid system is advised.

Numerical simulation on the efficiency of PVT system integrated with PCM under the influence of using fins

In current article, several 3D models of PVT/NEPCM (photovoltaic thermal system integrated with nano-enhanced phase change material) are evaluated numerically. The impact of different quantities of trapezoidal fins on the efficiency of PVT/NEPCM collectors (i.e. PVT/NEPCM without fins, with 10, 14, and 18 fins), with utilization of Al 2 O 3 /RT35-HC 0.04%vol. as NEPCM and SiC/water nano-fluid 0.04%vol. as coolant is investigated. Moreover, the effect of different solar flux intensities on the efficiency of the PVT/NEPCM collector was examined. Additionally, a 3D PVT/nano-fluid system with SiC/water nano-fluid as coolant is modeled to conduct a comparative investigation between PVT/NEPCM and PVT system. To model the charging and solidification of NEPCM, an enthalpy-porosity approach is applied. Furthermore, to model governing equations using computational fluid dynamic (CFD), a pressure-based finite volume technique with a transient solver is chosen. In order to provide coupling among the velocity and pressure, the SIMPLE model was utilized. Based on the numerical results, by utilizing trapezoidal fins in paraffin zone, the PV average temperature, and outlet temperature of coolant reduce, while the melting fraction of NEPCM enhances. Furthermore, the outcomes of study indicate that for the highest irradiation, the thermal performance of PVT/NEPCM system with 18 fins reaches 79.54%, which is 9.47% higher than the PVT/NEPCM without fins. Moreover, the liquid fraction of NEPCM for the PVT/NEPCM system with 18 fins reaches 57.15%, which is 2.94% higher than the system with 14 fins, 3.3% higher than the system with 10 fins, and 16.74% higher than the system without fins. • The effect of different number of fins on the performance of PVT/PCM is evaluated. • A 3D model of PVT system is developed to compare PVT/PCM and PVT systems. • Employing fins reduces the surface temperature of photovoltaic unit by 1.79 °C. • The temperature distribution is more uniformed in case of PVT/PCM compared to PVT. • Fin utilization enhances the melting fraction of PCM by 16.74%.

Heat transfer efficiency and electrical performance evaluation of photovoltaic unit under influence of NEPCM

In present study, a design of PVT unit involving PCM has been analyzed. The influence of several types of nanofluids and NEPCMs at different concentrations on the system efficaciousness is assessed. The SiC, ZnO, MCNT (multi-walled carbon nanotube), Al2O3, Cu, and Ag nanoparticles are utilized within water and phase change material at concentrations of 0, 0.02, 0.04. The impact of different flow rates and various solar radiation intensities are also evaluated. In addition, the influence of using multilayer of PCMs (including OM35, RT35HC, and eicosane) with different combinations inside the PCM receptacle on the productivity of component is assessed. At last, a comparison study between PVT, PVT/PCM, PVT-TE (thermoelectric module), and PVT-TE/PCM collector is conducted to assess the impact of TE module integration with the PVT systems from the electrical and thermal perspectives. To simulate the procedure of the charging of paraffin, the enthalpy-porosity approach is used. In addition, a transient solver and pressure-based finite volume approach are selected to perform the simulation. Based on the acquired results, enhancing the flow rate of coolant from 3.77 to 7.54 ml/s leads to 7.21% reduction in liquid fraction. It also de-elevates the average PV temperature, average outlet temperature, and the PCM temperature by 7.06%, 35.13%, and 3.62%, respectively. Enhancement of the NEPCM concentration from 0 to 4% improves the escalating charging rate, however, it de-elevates the temperature of PV unit and the Tout of coolant slightly.

Self-Sufficiency and Energy Savings of Renewable Thermal Energy Systems for an Energy-Sharing Community

Due to increased grid problems caused by renewable energy systems being used to realize zero energy buildings and communities, the importance of energy sharing and self-sufficiency of renewable energy also increased. In this study, the energy performance of an energy-sharing community was investigated to improve its energy efficiency and renewable energy self-sufficiency. For a case study, a smart village was selected via detailed simulation. In this study, the thermal energy for cooling, heating, and domestic hot water was produced by ground source heat pumps, which were integrated with thermal energy storage (TES) with solar energy systems. We observed that the ST system integrated with TES showed higher self-sufficiency with grid interaction than the PV and PVT systems. This was due to the heat pump system being connected to thermal energy storage, which was operated as an energy storage system. Consequently, we also found that the ST system had a lower operating energy, CO2 emissions, and operating costs compared with the PV and PVT systems.

Advances in PV and PVT cooling technologies: A review

Cooling with nanofluids has been one of the most promising cooling strategies used to minimize PV module temperature and enhance the performance of the system. This article presents a comprehensive literature survey on the recent advancements in solar PV cooling technologies, the role of nanofluids on the performance of PV thermal systems, the available analyses of PV cooling techniques, the usage of nanofluid as coolant and optical filter, and the effect of combined nanofluid and nano-PCM on the overall performance of the photovoltaic systems. The research outcome indicates that incorporation of active and passive cooling techniques brings about greater reduction in the PV cell temperature that translates to enhancement of PV-efficiency. Using nanofluids in PVT systems was found to improve the PV-efficiency by more than 60% while integration with PCM improves the PVT system efficiency by 32%. It goes without saying that combination of nanofluid and PCM is more effective cooling approach for the enhancement of PV-efficiency. Nanofluids have been shown to perform excellently for spectral splitting applications. The current study identifies the challenges in relation to the use of nanofluids in solar PVT systems.

Experimental investigation of the usability of the rifled serpentine tube to improve energy and exergy performances of a nanofluid-based photovoltaic/thermal system

This experimental study aims to energetically and exergetically compare the performance of a PVT system with sheet-and-plain serpentine tube collector (base PVT system) with two cases of modified PVT systems. The modified PVT systems are the replacements of plain serpentine tube with rifled serpentine tube with 3 ribs (3-start rifled PVT system) and 6 ribs (6-start rifled PVT system). The electrical parameter of the PV module without cooling is compared with the three cases of the PVT system with cooling. The cooling fluid is water/magnetite nanofluid. The effect of nanofluid flow rates (20–80 kg/h) and nanoadditive volume concentrations (0–2%) over the three cases of the PVT system is investigated to propose a suitable combination of flow rate and NA concentration offering the best energetic and exergetic performances. Thus, the 6-start rifled PVT system achieved a maximum of 22.5% and 3.8% higher overall energy efficiency, and 5.9%, and 1.9% higher overall exergy efficiency than the base and 3-start rifled PVT systems at flow rate and concentration of 80 kg/h and 2%. Finally, the electrical power generated by the base, 3-start rifled, and 6-start rifled PVT systems achieved maximum enhancement of 27.5%, 29.5%, and 31.5% compared to the PV module without cooling.

Experimental Study to Improve the Exergy Performance of Water Based Photovoltaic Thermal Collector (PV/T System) Using Water Guides

Photovoltaic panels can convert solar irradiance into (electrical and thermal) energy. The PV / T system was developed, created, and its performance tested in this experimental analysis. The experiment was performed with a flow rate of water from 1 L / min to 5 L / min on the PV / T collector channel. The movement of water with the guides allows the PV / T collector to improve thermal heat transfer convection. The output of (electrical and thermal) energy increase with the increase in radiation. The PV / T system performance varies with different volume flow rate that was reported for (1-5) L/min in this experiment, where the total energy increase with increasing the flow rate. Energy and exergy tests are performed, and findings show the maximum electrical and thermal energy output for a water-based PV / T system is 58.38 W and 465.8W at solar radiation 1000 W/m2. Meanwhile the maximum electrical and thermal efficiency of PVT systems is 14.595%, 94.49 % respectively at 5 LPM. While the maximum electrical percentage improvement in PV / T systems electrical output by the use of guides device is (36.78%), compared with traditional PV module.

The challenges of solar hybrid PVT systems in the food processing industry

This paper assesses the challenges of alternative solar systems based on hybrid PVT collectors coupled with an absorption chiller (AbCH, single-stage NH3-H2O) in the food-processing industry, from the technical, economic and environmental points of view. This type of industry is usually characterised by a constant cooling demand throughout the year, hot water demand for production processes and electricity consumption for factory equipment and lighting. To the authors’ knowledge, this work constitutes one of the first studies to address the integration of PVT-water collectors with a single-stage NH3-H2O AbCH for industrial applications. Two alternative PVT-water collectors are analysed, covered and uncovered. A biomass boiler is proposed as an auxiliary heater. To compare the proposed solar solutions, a vegetable and fruit processing and canning factory is considered as a representative case study. Hourly transient simulations considering the real factory demands and real weather data are performed over a year. Two main challenges are found for the solar systems based on the covered PVT collectors, an AbCH and a biomass boiler: the overlapping of the cooling and hot water demands of the food-processing industry, and the high hot water temperatures required. If, alternatively, the current electrical chillers are retained, the system based on uncovered PVT collectors has a reasonable-to-attractive payback time (14.3 years). When the potential environmental benefit is quantified (through carbon pricing), all the proposed solar systems become economically attractive, i.e., with positive total cost savings at the end of the system lifetime. Still, the high cost of PVT collectors, along with the considerably lower price of fuels compared to electricity, hinder the potential of systems that displace fossil fuels.

Development of flat-plate building integrated photovoltaic/thermal (BIPV/T) system: A review

The concept of building integrated photovoltaic/thermal system was introduced in the 1990 s and attraction towards this increased in 2000 because it provides net zero energy building by enhanced solar utilization. This work represents review of the flat-plate building integrated photovoltaic/thermal (BIPV/T) system, including current developments, experimental and numerical studies and parametric effect on the building performance. Flat-plate BIPV/T system reviewed here are: air-based system, water-based system and hybrid system in which, nano fluid, phase change material, cushion structure and heat pipe etc. are covered. From the study it is found that Performance of BIPV/T depends on design parameters and local weather condition. Also, more thermal energy is obtained by BIPV/water system as compared to BIPV/air system. This work provides overview of research, development, application and status of system. From most of the studies of BIPV/T systems and facades it has been observed that the variation of thermal efficiency is in the range of 22–55% for air-based systems and 30–60% for water-based systems. Further the electrical efficiency variation is in the range of 10–18% for air-based systems and 10–17% for water-based systems. It has been observed that the variation of thermal efficiency increases upto a mass flow rate of 0.1 kg/s after which the change is marginal to justify for thermal gain. Also, the electrical efficiency remains nearly unchanged at all mass flow rates. The highest thermal efficiency of 72% has been observed for Nano-PCM-PVT system which indicates that nano particles and PCM has a great potential for PVT systems.

Evaluation and comparison of different flow configurations PVT systems in Oman: A numerical and experimental investigation

The electrical efficiency of photovoltaic modules reduces with increase in cell temperature. However, using photovoltaic/thermal systems to enhance thermal, electrical, and overall outcomes is an excellent option. In this study, three water cooling PVT systems that have variable flow channels (web type, direct type, spiral type) installed, tested, evaluated, and compared with conventional PV in terms of electrical performance. The systems were tested outdoor in Sohar, Oman. The water mass flow rate was tested at 40 kg/h. The proposed systems reduced cell temperature on average by a minimum of 3 °C. The temperature reduction improves the voltage, power, and efficiency significantly. The highest average maximum voltage, current and power were observed for the spiral flow PVT system, which are 17.7 V, 2.89 A and 51.3 W, respectively. The overall efficiency for the conventional PV, web, direct and spiral type PVT systems were around 7.8%, 18.5%, 28.0% and 35.0%, respectively. The spiral flow collector found to produce the best efficiency compared to web and direct flow collectors. The results confirm that the use of the proposed PVT design is very suitable for the Sultanate of Oman and neighboring countries with similar environmental conditions.

Hybrid concentrated photovoltaic thermal technology for domestic water heating

There is an increasing reliance on renewable energy especially Solar Energy as the fossils are on the way to depletion.It offers an environmental friendly solution with an affordable comparative paradigm. Solar photovoltaic-thermal collectors have remained of the particular interest because of their higher overall efficiencies. Most of its applications related with solar hybrid PVT systems focuses more on electrical output rather than thermal output, and the contacting fluid is allowed to act as a coolant to assure that the solar cell operates in the ranges specified by the manufacturer to guarantee higher electrical efficiency. This ultimately allows fluid to retain higher temperature that could be utilized for meeting the heating demand of any residential household. First, the PVT analyses are performed over a system comprising of Fresnel-based Solar Module to allow higher irradiance to fall for relative higher conversion of efficiency and to achieve higher temperature ranges in the contacting fluid (water). The electrical parameters are compared, and a significant increase in the power ranges is concluded. Secondly, a simulated thermal structure of the heating tank is presented that utilises the heated water from the PVT system in meeting the heating demand of a residential household. When accounting all the electrical parameters, approximately 10% increase is noticed in power produced, and sufficient energy used for the traditional heating of water is retained.

C7+ Reservoir Fluid Characterisation: Modification of Lohrenz Splitting Correlation

Petroleum reservoir fluid is commonly classified as individual components of C1 – C6 and lumped-up component of C7+. C7+ are hydrocarbon components of C7-heptane and above, that is, heavy hydrocarbons that are minimal in natural gas. De-lumping or splitting of C7+ into individual components is vital for accurate and efficient estimation of fluid properties. A number of correlations exist in literature and pressure-volume-temperature software for this. The least accurate and simple model by Lohrenz, Bray & Clark (1984) was modified in this work. Efficiency of the new model is highly comparable with existing models in the rigorous PVT systems for computing intensive and extensive natural gas properties.

Experimental investigations of using MWCNTs and graphene nanoplatelets water-based nanofluids as coolants in PVT systems

In this study, a photovoltaic thermal collector)PVT(has been constructed in Karabuk University, Turkey to investigate the effects of utilizing multiwalled carbon nanotubes (MWCNT) and graphene nanoplatelets dispersed in water as a base fluid with a concentration of 0.5 wt% on the performance of PVT systems. Outdoor experiments were run with volume flow rate of 0.5 L/min for the aforementioned nanofluids and distilled water as a reference fluid. The study results, which were analyzed from energetic and exergetic viewpoints, have shown and revealed that the MWCNT-water nanofluid presented a better performance in terms of photovoltaic energetic conversion compared to graphene nanoplatelets-water nanofluid and distilled water, while graphene nanoplatelets-water nanofluid revealed the highest thermal energetic efficiency. Moreover adding thermal unit to photovoltaic module (PV) enhanced the total energetic efficiency by 53.4% for distilled water, 57.2% for MWCNT-water, and 63.1% for graphene-water. From the exergetic viewpoint, the increase in total exergetic efficiency was 11.2%, 12.1%, and 20.6% for PVT collector cooled by distilled water, MWCNT-water nanofluid, and graphene nanoplatelets-water nanofluid respectively.

Investigation of TiO2 and MWCNT Nanofluids-based Photovoltaic-Thermal (PV/T) System

Nanofluids as a new generation of cooling fluid has been found in recent years to improve the heat-transfer coefficient and enhance the system performance. This study presents investigation conducted on the performances of TiO2 and MWCNT nanofluids-based PVT systems. The preparation of nanofluids using two step method and dispersing of surfactant for a stable nanofluid. The experimental investigation with the effect of different concentration, mass flow rate (0.012 kg/s to 0.0255 kg/s) and solar radiation (500 W/m2 to 900 W/m2) on the performance of nanofluids-based PVT system is presented. The lowest temperature of the PV module and highest fluid’s change of temperature were recorded when the collector uses TiO2 fluid 1.0 wt% which is 2.01°C and 1.80°C.

Numerical and experimental investigation of the effect of operating conditions on performance of PVT and PVT-PCM

Irradiations incident on the photovoltaic module are converted only 15–20% into electrical energy and remaining are transformed into heat and drop electrical efficiency. Therefore, to harness both the thermal and electrical energy, hybrid photovoltaic thermal system is an optimum option. Moreover, phase change materials add more advantages of PV cell cooling and heat storage. A novel thermal collector has been designed as PVT and PVT-PCM systems to improve the heat transfer and performance. The 3D numerical analysis is done with COMSOL Multiphysics® software, and is validated at different volume flow rates of 0.5LPM to 3LPM, by experimental investigation at conditions of keeping the inlet water and ambient temperature at 27 °C and solar irradiation at 1000 W/m2. The experiment is carried out in indoor weather under controlled operating parameters and conditions with passive cooling of the module. Maximum 12.4% and 12.28% electrical efficiency of PVT is achieved numerically and experimentally respectively. Similarly, 12.75 and 12.59% electrical efficiency for PVT-PCM is obtained for experimental and numerical cases respectively. For PVT system, 10.13 and 9.2% electrical performance is improved. For PVT-PCM the electrical performance improvement is obtained as 12.91 & 12.75% numerically and experimentally respectively.

A Detailed Optimisation of Solar Photovoltaic/Thermal Systems and its Application.

Abstract There have been various studies and experimental results analysing the operational behaviour of PVT, most of which has been done at steady state or quasi-state. Variable factors can be controlled to optimise the PVT output such as mass flow rate, irradiation falling on the PVT through tracking or incidence angles in a day and fixed factors that depend on the design of the chosen PVT system as well as location parameters such as ambient temperature, wind speed, Transport Fluid used, Difference in Structure, Packing Density, Nominal operating temperature, stagnation temperatures, Fill Factor, Thickness of each layer, Location and Latitude and Heat removal factor (harp or serpentine design). The aim of this research is to validate and predict the dynamic behaviour of PVT systems while accurately describing the factor responsible for the loss of efficiency at any point in time under various weather constraints. A commercial system was considered (Solar Angel PVT system) here and is simulated for an entire year. The system was modelled in MATLAB and solved in implicit RK-4 method. The research question finds out to establish the basis for a standard testing protocol for assessing PV-T performance throughout various differences. It also analyses the long-term dynamic performance of PV/T technology by providing evidential data analysis (solar irradiance, heat and electricity, ambient temperature, operational temperatures, flow rates and thermal storage capacity) while completing an assessment of PVT behaviour with respect to an equivalent PV under different weather conditions. The flow rates, heat removal factor and the location affect the thermal behaviour of the PV/T to a greater extent than nominal temperatures and stagnation temperatures.

Evaluation and analysis of nanofluid and surfactant impact on photovoltaic-thermal systems

The use of nanofluids as a heat transfer agent has spread and expanded as its thermal conductivity is higher than the base fluid, so its use has been increased in heat exchangers and PVT systems. In this study, water was used as a base fluid and nano-silicon carbide as an additive to improve the thermal conductivity of the resulted nanofluid and its thermophysical properties were studied using five surfactants. In this study, the stability time of nanofluid was the main variable investigated. The stability of nanofluid depends on the surfactant used to slow the suspended nanoparticles deposition in the emulsion. The deposition process significantly reduces the thermal conductivity of nanofluids and thus reduces heat transfer. The study results indicated that the time of nanoparticles suspended in emulsion depend mainly on the type of the surfactant used and the ultrasonication time. The used surfactants are: ammonium cetyl cetyl (CTAB), sodium dodecyl sulfate (SDS), tannic acid+ammonia solution, dodecylbenzenesulfonate (SDBS), and Sodium deoxycholate. Ammonium cetyl cetyl (CTAB) and tannic acid+ammonia solution gave the highest stability period (more than two months) with ultrasonication mixing time for six hours by adding 0.1 ml. The addition of larger amounts of surfactant (more than 0.75 ml) increased the stability time for all nanofluids used. The maximum stability time achieved was 88 days when cetyl cetyl (ammonium cTAB) was added by 0.5 ml. The density, viscosity, and thermal conductivity measurements showed that there was no significant change with the change of the surfactant used. The addition of larger amounts of surfactant (more than 0.5 ml) caused a very limited increase in the density and viscosity of nanofluids. It also caused a small reduction in thermal conductivity.