Photovoltaic Thermal Collector Research Articles

Thermodynamic performance analysis and modified thermo-ecological cost optimization of a hybrid district heating system considering energy levels

Utilization of the renewable resources in district heating systems can reduce the use of fossil fuels, operating costs and protect the environment. In this study, an integrated hybrid system consisting of concentrating photovoltaic/thermal collectors (PV/T), geothermal (GSHP) and absorption (AHP) heat pumps is considered for district heating. The thermodynamic performance of the system at various conditions is explored through detailed simulations. A modified thermo-ecological cost (TEC) method is used to optimize the structure of the PV/T by considering contributions of different flows. The results show that a higher solar irradiance level and a higher PV coverage ratio have a positive impact on the thermal performance of the hybrid system. The TEC-based optimization shows that a 66% PV coverage ratio of PV/T yields a minimum thermo-ecological heating cost of 6.86 J/J, which is slightly lower than cost with a conventional method. Based on the sensitivity analysis, other key parameters except the operating time and the PV coverage ratio have a negative influence on the economic performance of the district heating system, because of the increasing cumulative exergy consumption of the GSHP or PV/T.

Indoor Test Conditions of Thermal Collector Channel Using Water as a Working Fluid to Enhance the Electrical and Thermal Efficiency of the PV / T System

The hybrid (PV/T) system or photovoltaic thermal collector generates the electrical and thermal energy simultaneously. The main objective of this study was to design, manufacture and evaluate the work of the PV/T system as a thermal collector to enhance heat transfer, by using (distilled water) as a working fluid used to cool (PV/T) system. The experimental setup of the system was constructed, using the optimal water guides for each configuration and was evaluated using the numerical results. thermal absorber collector of (PV/T) system is the box made of a heat-insulating material (foam), inside which contains a water guides that is operated by a CNC machine used to distributed of liquid inside of PV/T system, then installed later in the back surface of the photoelectric panel using epoxy wax, here, designed the thermal absorber collector channel to be within the geometrical shape of the PV panel to observe the rules placed to install the PV panels previously prepared. Results obtained from the numerical analysis indicated that the rectangular channel with round water guides, linear distribution [d = 10mm, h = 3mm, n = 66] has the best design used to heat transfer. The results showed that the thermal aggregation channel with round fluid flow guides, at linear distribution, had a 14.595% PV/T for maximum electrical efficiency and a 94.514% PV/T for maximum thermal efficiency for experimental results, where the total efficiency increase with increasing the flow rate, for all experience the was the volume flow rate is 5L/min minute and solar radiation was 1000 w/m2.

Efficiency limits of concentrating spectral-splitting hybrid photovoltaic-thermal (PV-T) solar collectors and systems

Spectral splitting is an approach to the design of hybrid photovoltaic-thermal (PVT) collectors that promises significant performance benefits. However, the ultimate efficiency limits, optimal PV cell materials and optical filters of spectral-splitting PVT (SSPVT) collectors remain unclear, with a lack of consensus in the literature. We develop an idealized model of SSPVT collectors and use this to determine their electrical and thermal efficiency limits, and to uncover how these limits can be approached through the selection of optimal PV cell materials and spectral-splitting filters. Assuming that thermal losses can be minimized, the efficiency limit, optimal PV material and optimal filter all depend strongly on a coefficient w, which quantifies the value of the delivered thermal energy relative to that of the generated electricity. The total (electrical plus thermal) efficiency limit of SSPVT collectors increases at higher w and at higher optical concentrations. The optimal spectral-splitting filter is defined by sharp lower- and upper-bound energies; the former always coincides with the bandgap of the cell, whereas the latter decreases at higher w. The total effective efficiency limit of SSPVT collectors is over 20% higher than those of either standalone PV modules or standalone ST collectors when w is in the range from 0.35 to 0.50 and up to 30% higher at w ≈ 0.4. This study provides a method for identifying the efficiency limits of ideal SSPVT collectors and reports these limits, along with guidance for selecting optimal PV materials and spectral-splitting filters under different conditions and in different applications.

Modelling of photovoltaic-thermal collectors for the provision of electricity and low temperature heat—Comparison of different flow rate control approaches to optimize the electrical yield

• Locally adapted flow rate control approaches can increase the electrical yield of PVT collectors by up to 2.80%. • Compared to a reference case, an increase in additional electrical yield of up to 27% is possible. • Constant flow rate control approaches provide a flat distribution of temperature increase. • Variable flow rate control approaches provide a distribution peak of temperature increase. Photovoltaic-thermal (PVT) collectors can provide heat and electricity. A quasi-stationary model of a PVT collector is presented and validated based on measured data. Subsequently, the electrical and thermal performance of such a collector is simulated for different locations. These simulations focus on different flow rate control approaches with the aim of maximizing the electrical yield. The simulation results show that the two control approaches presented in this paper have the potential to increase the electrical output for all locations. The increase in additional electrical output at locations with higher solar radiation is significantly higher than the increase in solar radiation between the locations investigated. Additionally, the cooling fluids’ temperature differences for such PVT collectors vary between the investigated control approaches, where variable flow rates lead to a steadier increase in cooling fluids’ temperature. In conclusion, the flow rate needs to be adopted to the pre-defined main goal of the respective PVT collector. The use of variable flow rates by providing low-temperature heat at a more constant temperature level appears to be advantageous in this context.

Development and Performance of Roof-Based Building-Integrated Photovoltaic-Thermal Systems: A Review

Abstract A building-integrated photovoltaic-thermal (BIPVT) system integrates building envelope and photovoltaic-thermal collectors to produce electricity and heat. In this paper, the electrical and thermal performance of roof-based BIPVT systems developed in the recent two decades and their effects on heating and cooling load of the building are reviewed. According to the use of thermal energy from the photovoltaic (PV) panels, the roof-based BIPVT are classified into three classes: cooling of PV, air heating, and water heating. Each class is further divided into several types according to the designs of the integrated PV roofs. Compared with BIPV systems, the total efficiency of most BIPVT systems is significantly improved. However, the decrease in electricity output and adverse impact on the indoor environment is also found for some designs of BIPVT systems in some climates. The advantages and disadvantages of various designs are discussed. Issues to be further studied in the future are also provided in this review.

10-year simulation of photovoltaic-thermal road assisted ground source heat pump system for accommodation building heating in expressway service area

The photovoltaic-thermal (PVT)-ground source heat pump (GSHP) system has been proved to have great potential in improving building energy efficiency, but ordinary PVT collector requires a large installation area and limits the popularization of PVT. In this paper, a novel solar energy collector, called photovoltaic-thermal road (PVTR), is proposed to replace the traditional PVT collector, and a novel energy system that is PVTR-GSHP system is proposed. In order to study the system performance, taking a typical expressway service accommodation building in Beijing as an example, a 10-year simulation is carried out to analyze the heating operation characteristics of the proposed system. Moreover, the effects of the PVTR area, the length and layout of ground heat exchanger (GHE) on the system performance are also discussed. Results show that, when the length of GHE is 5000 m, and the number of boreholes is 25 and the borehole depth is 100 m, the minimum area of PVTR satisfying the soil heat balance and meeting the system power consumption are 187.2 m2 and 216 m2, respectively. When the PVTR area is 216 m2, the minimum GHE length satisfying the soil heat balance is 4000 m. Finally, to realize system zero energy consumption and soil heat balance, the best combination of GHE length and PVTR area is 4000 m and 216 m2 under the cases of this paper. And in this case, the average COPHP and COPsys in ten years are 5.59 and 2.31 respectively.

Experimental Performance of an Advanced Air-Type Photovoltaic/Thermal (PVT) Collector with Direct Expansion Air Handling Unit (AHU)

In addition to electrical energy generation, photovoltaic/thermal (PVT) systems utilize heat from building-integrated photovoltaic (BIPV) modules for domestic hot water and space heating. In other words, a PVT system can improve the electricity efficiency of BIPVs while using the waste heat of BIPVs as a source of thermal energy for the building. By generating thermal and electrical energies simultaneously, PVT systems can improve the utilization of solar energy while enhancing the energy performance of buildings. To optimize the performance of an air-type PVT collector, it is necessary for the system to extract more heat from the PV module. Consequently, this approach decreases PV temperature to improve PV electrical energy generation. The thermal and electrical performance of an air-type PVT collector depends on its design, which affects airflow and heat transfer. Moreover, the performances of the PVT collector can differ according to the coupled facility in the building. In this study, the thermal and electrical performances of an advanced air-type PVT collector with a direct expansion air handling unit (AHU) were analyzed experimentally. For this purpose, six prototypes of an advanced air-type PVT collector were developed. Furthermore, a direct expansion AHU with a heat recovery exchanger (HRX) was designed and built. The advanced PVT collectors with a total capacity of 740 Wp were installed in an experimental house and were coupled to the direct expansion AHU system with a maximum airflow of 700 CMH. The performance of PVT collectors was analyzed and compared with the BIPV system. Results showed that building-integrated photovoltaic/thermal (BIPVT) collectors produced 30 W more power than the BIPV system. When operating the AHU system, the temperature of the BIPVT collector was generally lower than the BIPV. The maximum difference in temperature between BIPVT and BIPV was about 22 °C. During winter season, the BIPVT collector supplied preheated air to the AHU. The supplied air temperature from the BIPVT collector reached 32 °C, which was 15 °C higher than outdoor air temperature.

Energy-exergy analysis of an infrared dryer equipped with a photovoltaic-thermal collector in glazed and unglazed modes

In this study, the manufacturing and testing of an infrared dryer equipped with a PV/T solar collector were investigated. The total energy for the drying process is provided by solar energy. This study sought to compare the experimental results of glazed and unglazed modes and observe the effect of volume flow rate variations on the drying process of the products to determine the dryer’s energy and exergy efficiency and analyze the drying kinetic of potato slices. The amount of inlet airflow to the PV/T was controlled during the experiment. The power of the fan is supplied directly from two photovoltaic panels and the surplus amount of electrical energy is assigned to an infrared radiation source to enhance the process. Despite the low energy consumption of the current system, the products’ drying time was significantly reduced compared to similar systems. As a result, in glazed experiments, the drying time is prolonged in a range of 12–25% for 3 mm thicknesses and between 5 and 25% for 7 mm thicknesses compared to unglazed experiments. The maximum system energy efficiency and system exergy efficiency were 9% and 0.5%, respectively, calculated for 7 mm slices in unglazed tests.

Integrated performance analysis of a space heating system assisted by photovoltaic/thermal collectors and ground source heat pump for hotel and office building types

Utilizing the solar and geothermal energy in space heating systems can save fossil fuels and reduce emissions. In this study, compound parabolic concentrator (CPC) photovoltaic/thermal collectors (PV/T), absorption and ground source heat pumps are integrated to a novel space heating system for use in hotel and office buildings. A full simulation model of the system is constructed and validated by using the Engineering Equation Solver software. The heating system is analyzed against its energy, environmental, economic, and flexibility performance using multiple variables including the PV coverage ratio, ambient temperature, solar beam irradiance, and electricity price. The results show that integrating solar and geothermal energy can be effective to supplement the space heating demand. The best integrated performance point of the office building gives a 32% energy saving ratio, 9% annual cost savings ratio, 23% emission reduction ratio, and 67% excess adjustable ratio compared to a pure ground heat pump system. This research provides new directions of integrated performance evaluation of heating systems assisted by renewable energy resources.

Performance and CO2 emissions assessment of a novel combined solar photovoltaic and thermal, with a Stirling engine micro-CHP system for domestic environments

This paper presents a novel installation where a set of photovoltaic modules and solar thermal collectors work in conjunction with a micro-CHP Stirling Engine to provide a reliable and self-sufficient energy system. A literature review showed that, while there are implementations of micro-CHP systems in household environments, there are no installations where the micro-CHP unit worked in conjunction with solar systems, photovoltaic and thermal. With the usage of Li-ion battery storage and a hot water tank for heat storage, as well as the micro-CHP unit, the system increases its reliability and independence from climatic conditions. The results obtained show that this system can supply 75.6% of the total energetic demand of a typical household, while achieving a reduction of 36.2% in the CO2 emitted to produce all the consumed energy in the system. The complete thermal demand has been met, while the usage from the electric grid has been required to meet 33.5% of the electric demand. However, with an increase in battery capacity to 20 kWh (doubling the actual capacity), the system is expected to become fully autonomous, as 31.8% of the electricity generated in the modules was exported to the grid due to saturation in storage capacity. In the thermal energy balance, sufficient heat was generated to provide enough energy for space heating or cooling, as well as domestic hot water.

Photovoltaic Thermal (PVT) with Advanced Tube Design and Working Fluid - A Review

This paper reviews the state-of-the-art cooling classification methods for photovoltaic system (PVs) modules and evaluates water or nanofluid, in details, the performance of radioactive cooling method. This review also covers the future development of absorber tubes photovoltaic thermal collector PVT. Daily heat budgets of PV modules with different absorbed tubes used in solar cells to reduce the temperature of the surface were analysed. This paper provides an overview of the various solar absorber tubes of Photovoltaic thermal (PVT) collector technologies, including their efficiencies, benefits, drawbacks, and research opportunities. The results show that the shape and diameter of the tube, the mass flow rate and the working fluid improved the total efficiency for the PV cell.

Experimental study about utilization of MWCNTs and graphene nanoplatelets water-based nanofluids in flat non-concentrating PVT systems

Although the increment the performance of photovoltaic thermal (PVT) systems by using the nanofluids as working fluids have gained the attention of researchers during the last two decades, there is still, a lack in the literature study associated to this application. This study contributes to the investigations and researches of applying the nanofluids to increase the performance of PVT collectors. A flat non-concentrating PVT collector has been designed, constructed and, outdoor tested in Karabuk University, Turkey. The considered working fluids in this study are multiwall carbon nanotubes (MWCNT), and graphene nanoplatelets dispersed in water as a base fluid with a concentration of 0.5 wt.%. The experiments were run with a volume flow rate of 0.5 L per minute for the aforementioned nanofluids and distilled water (as a reference fluid). The study results have shown and revealed that the MWCNT-water nanofluid presented a better performance in terms of eletrical energetic efficiency 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 enhanced the total energetic efficiency by 53.4% for distilled water, 57.2% for MWCNT-water, and 63.1% for graphene-water.

Experimental Study of Electrical and Thermal Efficiencies of a Photovoltaic Thermal (PVT) Hybrid Solar Water Collector with and Without Glass Cover

Investigating the thermal and electrical gains and efficiencies influence the designed photovoltaic thermal hybrid collector (PVT) under different weather conditions. The designed system was manufactured by attaching a fabricated cooling system made of serpentine tubes to a single PV panel and connecting it to an automatic controlling system for measuring, monitoring, and simultaneously collecting the required data. A removable glass cover had been used to study the effects of glazed and unglazed PVT panel situations. The research was conducted in February (winter) and July (summer), and March for daily solar radiation effects on efficiencies. The results indicated that electrical and thermal gains increased by the increase in solar radiation. The average rise in PVT water collectors' thermal energy efficiency with a glass cover for three cases was 5% compared with the unglazed PVT water collector. While the maximum total efficiencies of 79 % and 69.5 % for glazed and unglazed collectors were recorded under maximum solar radiation of 1100 W/m2 and maximum water flow rate in the tubes system for July. The recorded result seemed promising and significant, indicating that the manufactured system is useful for adjusting PVT thermal and electrical efficiencies for cold and hot weather conditions.

Possibilities Study of Using Hybrid Solar Collectors in Northeastern Libya Residential Home

The majority of electricity generated in Libya comes from fossil fuels. More oil and gas will be consumed, resulting in higher CO 2 emissions, as energy demand is projected to grow sharply in the near future. A feasibility study of a climate photovoltaic solar thermal collector and its relation to solar photovoltaic and solar water heating systems is being conducted. Based on population consumption in northeastern Libya, the study aims to determine the daily and annual electrical load coverage of 10.5 and 3942 kWh/year, respectively. The Polysun software simulation was used to analyze the electrical and thermal efficiency environment of Almarj city as a case study. Three of 280 W monocrystalline crystal solar collectors were used to generate 1445 kWh/year. By the number of collectors from five to seven, 3420 kWh/year can be generated. Increasing the number of collectors to nine protected 10.5 kWh/day, resulting in 4733 kWh/year of electrical energy, and the average annual consumption of a house is about 10,529 kWh. If the Libyan network losses are ignored, the device will use 263,225 MWh over its 25-year lifespan, resulting in a fuel cost of $47,380. The estimated annual savings per house is 1895 dollars, and the reduction of carbon dioxide emissions for light oil, heavy oil, and gas is 252, 195, and 15447 kg, respectively. Based on the existing study, the hybrid system has a substantial economic viability system compared to other solar systems, depending on the demand for power, heat, or a combination of both. As a result, the Almarj residential on-grid electrical loads, fossil fuel demand, global warming, and pollution to the atmosphere will all be reduced. https://dorl.net/dor/20.1001.1.13090127.2021.11.2.15.4

Experimental Study of Electrical and Thermal Efficiencies of a Photovoltaic Thermal (PVT) Hybrid Solar Water Collector with and Without Glass Cover

Investigating the thermal and electrical gains and efficiencies influence the designed photovoltaic thermal hybrid collector (PVT) under different weather conditions. The designed system was manufactured by attaching a fabricated cooling system made of serpentine tubes to a single PV panel and connecting it to an automatic controlling system for measuring, monitoring, and simultaneously collecting the required data. A removable glass cover had been used to study the effects of glazed and unglazed PVT panel situations. The research was conducted in February (winter) and July (summer), and March for daily solar radiation effects on efficiencies. The results indicated that electrical and thermal gains increased by the increase in solar radiation. The average rise in PVT water collectors' thermal energy efficiency with a glass cover for three cases was 5% compared with the unglazed PVT water collector. While the maximum total efficiencies of 79 % and 69.5 % for glazed and unglazed collectors were recorded under maximum solar radiation of 1100 W/m2 and maximum water flow rate in the tubes system for July. The recorded result seemed promising and significant, indicating that the manufactured system is useful for adjusting PVT thermal and electrical efficiencies for cold and hot weather conditions.

The Technical Design Concept of Hi-Tech Cook Stove for Urban Communities using Non-Wood Agricultural Waste as Fuel Sources

The purpose of this study is to conceptualize an urban Hi-Tech Cook-Stove (HTCS) design using agricultural waste. Several steps need to be carried out. First, determine the cooking activities depend on the family size and food categories. Second, calculate the energy required for cooking. Third, determine the mass of biomass fuel required. Fourth, calculate the fuel consumption rate. Fifth, design the dimensions of the stove by considering the ergonomics, easy in manufacturing, installation, etc. Sixth, estimate the volume of each component. The result shows that the fuel supply must adjust the flow rate of fuel, air to fuel ratio controlled by a simple mechanical-electric compressor, monitor the combustion chamber visually/automatically, and the dust must be collected/disposed of automatically/mechanically. HTCS must consider the pellets from the higher heating value and faster of biomass with a certain composition of chopped and fibre, also the safety and comfort, such as overheating control, air exhaust control, combustion control, cooling control. For the future, the HTCS technical design concept must be integrated with the electricity and hot water from solar energy by using a hybrid photovoltaic-thermal (PVT) collector and urban biogas digester in the development of smart grids and smart cities.

Case Studies of Solar Heat Transfer Performance in a Water-Based Serpentine Photovoltaic-Thermal (PVT) Collector with CFD Simulation and Experimental Validation

Case Studies of Solar Heat Transfer Performance in a Water-Based Serpentine Photovoltaic-Thermal (PVT) Collector with CFD Simulation and Experimental Validation

Comparison of the Critical Mass Flow Rates for Two Serpentine Designs of the Photovoltaic Solar Thermal Collector

A recent analysis on the photovoltaic (PV) cell efficiency for the photovoltaic solar thermal collector (PVT), cooled by forced fluid flow, revealed that there is, in general, a critical mass flow rate that corresponds to the maximum PV cell efficiency for a PVT. The derived new equations are applicable for laminar and transition or turbulent flow regimes and could yield directly the critical mass flow rate as compared with existing methods that use repeated computational trials. To demonstrate further the generality of the method, this paper reports results on comparing the critical mass flow rates for two serpentine designs with different technical details, namely Design A and Design B, using the new equations. It is shown that Design A and Design B have critical mass flow rates of 0.041 and 0.014 kg/s, respectively. The corresponding Reynolds numbers are 4078 and 2785 for Design A and Design B, respectively. It is shown that the critical mass flow rate is different from one design to another. The importance of the critical mass flow rate is summarized.

Alternative determination of critical mass flow rate for the photovoltaic solar thermal collector in forced fluid mode

From existing equations, which have been validated by experimental measurements in the literature, the photovoltaic (PV) cell efficiency for the photovoltaic solar thermal collector (PVT), cooled by forced fluid flow, is shown to be a function of the mass flow rate. This study shows, with calculus, that there is, in general, a critical mass flow rate which corresponds to the maximum PV cell efficiency. The derived new equations are applicable to laminar regime and transition or turbulent flow regimes. These equations can yield directly the critical mass flow rate, as compared with existing methods that use observation on the results obtained by repeated computational trials.

Analysis of a vacuum-based photovoltaic thermal collector

In this study, a new design of photovoltaic thermal (PV/T) collector is proposed. This design uses a vacuum layer above the silicon wafer and not exists in the traditional PV/T collector. This layer is used to decrease the heat loss from the top surface of the PV/T collector. The analysis is conducted using a 3D thermal modeling. The new collector design with the vacuum layer achieved a 26.6% increase in the thermal power while keeping the electrical the same at Reynolds number of 50 and solar radiation of 1000 W/m2. In addition, the degradation of the vacuum pressure slightly influence the thermal performance while increasing the vacuum pressure from 0.01 Pa to 10 Pa. While further increase in the vacuum pressure from 10 Pa to 1.013×105 Pa substantially decreases the gained thermal power with insignificant increase in the electrical power.