Hybrid Solar Collector Research Articles

Simulation of unsteady natural convection flow of a Casson viscoplastic fluid in a square enclosure utilizing a MAC algorithm

AbstractNon‐Newtonian fluids are increasingly being deployed in energy systems and materials processing. Motivated by these developments, in the current study, a numerical simulation is performed on two‐dimensional, unsteady buoyancy‐driven flow in a square cavity filled with non‐Newtonian fluid (Casson liquid). The enclosure geometry features vertical isothermal walls (with one at higher temperature than the other) and thermally insulated horizontal walls. The conservation equations for mass, momentum, and energy are normalized via appropriate transformations and the resulting dimensionless partial differential boundary value problem is solved computationally with a marker and cell algorithm, which features a finite difference scheme along with a staggered grid system. The projection method is employed to evaluate the pressure term. Extensive visualizations of the impact of emerging physical parameters (Rayleigh number and Casson viscoplastic parameter) on streamline and isotherm distributions in the cavity are presented for fixed Prandtl number. Nusselt number, that is, heat transfer rate, is increased with rising values of the Casson viscoplastic fluid parameter for any value of Rayleigh number. The density of streamlines increases with increasing values of Casson viscoplastic fluid parameter upto 1. Overall, the Casson fluid parameter plays a vital role in controlling the convective heat transfer within the enclosure. The computations are relevant to hybrid solar collectors, materials fabrication (polymer melts), etc.

Enhanced generation of hydrogen, power, and heat with a novel integrated photoelectrochemical system

Hydrogen is an essential component of power-to-gas technologies that are needed for a complete transition to renewable energy systems. Although hydrogen has zero GHG emissions at the end-use point, its production could become an issue if non-renewable, and pollutant energy and material resources are used in this step. Therefore, a crucial step for the fully developed hydrogen economy is to find alternative hydrogen production methods that are clean, efficient, affordable, and reliable. With this motivation, in this study, an integrated and continuous type of hydrogen production system is designed, developed, and investigated. This system has three components. There is a solar spectral splitting device (Unit I), which splits the incoming solar energy into two parts. Photons with longer wavelength is sent to the photovoltaic thermal hybrid solar collector, PV/T, (Unit II) and used for combined heat and power generation. Then the remaining part is transferred to the novel hybrid photoelectrochemical-chloralkali reactor (Unit III) for simultaneous H2, Cl2, and NaOH production. This system has only one energy input, which is the solar irradiation and five outputs, namely H2, Cl2, NaOH, heat, and electricity. Unlike most of the studies in the literature, this system does not use only PV or only a photoelectrochemical reactor. With this approach, solar energy utilization is maximized, and the wasted portion is minimized. By selecting PV/T rather than PV, the performance of the panels is maximized because recovering the by-product heat as a system output in addition to electricity, and the PV/T has less waste and higher efficiency. The present reactor does not use any additional electron donors, so the wastewater discharge is only depleted NaCl solution, which makes the system significantly cleaner than the ones available in the literature. The specific aim of this study is to demonstrate the optimum operating parameters to reach the maximum achievable production rates and efficiencies while keeping the exergy destruction as little as possible. In this study, there are four case studies, and in each case study, one decision variable is optimized to get the desired performance results. Within the selected operating parameter range, all performance criteria (except exergy destruction) are normalized and ranked for proper comparison. The maximum production rates and efficiencies with the least possible exergy destruction are observed at the operating temperature of 30 °C. At 30 °C, 4.18 g/h H2, 127.55 g/h Cl2, 151 W electricity, and 716 W heat are produced with an exergy destruction rate of 95.74 W and 78% and 30% energy and exergy efficiencies, respectively.

Photovoltaic-thermal (PVT) technology: Review and case study

Nowadays, solar technology converts solar energy into electricity and heat separately. For electricity generation, the main obstacle is the fact that the photovoltaic cells produce less energy as the temperature increases. To overcome this, cooling techniques can be used to raise the efficiency of solar cells, in order to obtain greater power generation. The photovoltaic-thermal hybrid solar collector (or PVT) is an equipment that integrates a photovoltaic (PV) module, for the conversion of solar energy into electrical energy, and a module with high thermal conversion efficiency (T), which employs a thermal fluid. This optimization of solar conversion technology has the main objective of cooling the photovoltaic cells, for increased generation of electricity, while also resulting in useful thermal energy from the working fluid, therefore constituting a cogeneration equipment. The present work reviews the development and global panorama of PVT technology. Afterwards, a case study of a PVT system is presented, together with a theoretical and experimental study. A thermography analysis performed in this PVT system is also examined, which allows for a real-time study of its operating regimes in different conditions, mainly of its thermal behaviour, and for the diagnosis of hot spots that signal potential defects in the cells.

Cogeneration of energy in solar systems - a study case, Kosovo

<p>Nowadays the main goal of sustainable energy supply is the use of renewable energy sources and, in addition, the increased efficiency of the energy used. One possibility of using renewable energies is the use of solar energy through photovoltaic panels. Taking into account the meteorological characteristics of the country in which the study takes place, it appears that the use of photovoltaic panels will be available most of the time during the year. We applied a model of hybrid solar collectors for maintaining the cell temperature near 25°C by introducing a flat plate cover integrated with solar cells. This method represents a way to increase the efficiency of the solar collector. This will enable the production of electricity from the part of the photovoltaic panel incorporated into the solar collector, in which the water temperature will increase, and this heat from the water is due to the effect of sunlight and as a result of cooling the part of the photovoltaic panel. This represents an increase in the efficiency of the system and the main purpose of our analysis.</p>

Study into predicted efficiency of the application of hybrid solar collectors to supply energy to multi-apartment buildings

This paper reports a study into efficiency of the application of hybrid solar collectors, which can simultaneously generate both electricity and thermal energy to supply power to multi-storey buildings. The novelty of the work is that efficiency was predicted taking into consideration the dynamics over recent years and by extrapolating trends in prices up to the year2045 inthe market of renewable energy, in contrast to existing approaches that disregard their likely change over the considered period. The results of calculations were used to model a predicted market value of the equipment, taking into consideration a reduction in its price due to the improved technology for manufacturing the collectors, their installation, and operating costs, over a specified period. In this case, the dynamics in the «basic» and «green» tariffs for solar electric and thermal energy were considered. Values for the coefficients of determination have confirmed sufficient adequacy of the derived models. An example has been provided for determining the electric and thermal loading on a multi-apartment building equipped with gas stoves; the proper equipment for a hybrid solar collector has been selected. The structures and procedures have been proposed for connecting a hybrid collector to the systems the supply electricity and heat to the building. The collector’s modules the type of ATMOSFERA F2PV are arranged at the roof of the building, whose electric components are connected, through an inverter, to the inlet-distributor device in a building or to the low-voltage buses at a power substation with a voltage of 10/0.4 kV, which powers the building. A heat-carrier is fed from the collector, through storage capacities, to a thermal unit into the system of hot water supply and heating of the building. The obtained results of the study have made it possible to predict a probable energy efficiency (the amount of saved conventional fuel), economic (net discounted profit) and environmental efficiency (reduction in emissions that contribute to the global climate warming). The payback period has been determined by consistent calculation of net income for each year over the entire period of realization of investments provided the specified trend in market prices does not change. The paper presents the results from calculating the magnitude of investments and income for inhabitants per each apartment in the building from the implementation of the investment project.

The validation of a novel lumped parameter model for photovoltaic thermal hybrid solar collectors: a new TRNSYS type

Decarbonisation is one of the most important challenges facing researchers, and solar-assisted systems represent an important solution to reduce the energy consumption at the household-scale. The current work contributes to existing research by proposing and validating a novel lumped parameter simulation model for photovoltaic thermal hybrid solar collectors using field measurements carried out at an experimental facility. The modelling approach, which also considers the effect of the thermal capacitances of the elements composing the photovoltaic thermal collector, used an electrical analogy method to solve the transient heat transfer problem. The results of the simulations were compared with the experimental data collected during different weather conditions; the effects of the thermal capacitances of the collector were also investigated. The results were compared in terms of both average daily performance and instantaneous values of the variables characterizing the system. Although the differences were negligible, the results of the simulation analyses matched the measurements more precisely when the thermal capacitances were taken into consideration. Finally, the simulation model was implemented as a TYPE of Transient System Simulation (TRNSYS) software, and it is made freely available to facilitate future integrated computer simulations.

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

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

Hybrid system solar collectors - heat pumps for domestic water heating

This paper deals with the use of solar energy, heat pumps, and solar system-heat pump combinations for domestic water heating. The testing of solar tiles, flat plate collectors as an autonomous system, as well as flat plate collector-heat pump and solar tile-heat pump combinations, are presented. Black-coloured water absorbs solar radiation flows through solar tiles made of transparent polymethyl methacrylate (CH2C(CH3)COOCH3). At the same time, solar tiles are used as a roof covering and as a solar radiation collector. Hot water from solar tiles or a flat plate collector is directed to the heat pump, which increases the temperature of water entering the boiler heating coil. The heat of water heated in solar tiles or in flat plate collectors serves as a source of energy for the heat pump. Since the goal was realistically evaluate the efficiency of solar tiles in comparison with the flat plate collector, extensive measurements of both systems under identical condition were carried out. The experiments were carried out in rainy, cloudy, and clear weather.

Experimental determination of thermal conductivity and viscosity of different nanofluids and its effect on a hybrid solar collector

In this research, three different volume concentrations (ϕ = 0.05, 0.1 and 0.2%) of Al2O3/water, CuO/water and Al2O3–CuO/water (50:50) nanofluids are prepared by adopting a two-step nanofluid preparation method. Al2O3 and CuO nanoparticles with the average diameter of 50 nm and 27 nm were dispersed in distilled water. The thermal conductivity and viscosity of prepared nanofluids are measured for different temperatures by using KD2 Pro thermal property analyzed and Brookfield viscometer, respectively. The effects of nanofluids on the thermal, electrical and overall efficiency of photovoltaic thermal (PVT) solar collector are also studied. The experimental results revealed that the thermal conductivity and viscosity increase with the increase in percentage volume concentration and viscosity decreases with the increase in temperature. Furthermore, the obtained maximum thermal and electrical efficiencies of a PVT solar collector for 0.2% volume concentration of hybrid nanofluids are 82% and 15%, respectively, at peak solar radiation. The highest overall efficiency of a PVT collector with .2% volume concentration of hybrid nanofluid was 97% at peak solar radiation. Results recommend that nanofluids can be used as a heat transfer in PVT solar collector.

Integrated power generation cycle (Kalina cycle) with auxiliary heater and PCM energy storage

Kalian cycle is a modified Rankine cycle for power generation, that its working fluid is a mixture of ammonia-water instead of pure water and can be driven in higher temperatures comparing to the Rankine cycle. In this study a hybrid Kalina power cycle and solar thermal flat plate collector using phase change material (PCM) as thermal energy storage material is introduced and analyzed. Bandar Aabas (a city in south of Iran), because of its sunny days and use of the Persian Gulf sea water for cooling in the condenser has been selected. The amount of solar fraction in year is 83.8%. This integrated process requires 53.85 GWh heat load during the year that 45.13 GWh of energy per year in the system, is supplied by the sun during the hours of 7–19 and released energy from the PCM during the night from 19.01 to 6.59. Rest of the needed heat load for the integrated system of 8.72 GWh per year is provided with auxiliary heater. By using energy and exergy balance equations, all components were analyzed. According to the results, thermal efficiency of the Kalina cycle is 6.12%. Results of the exergy analyses show 23.21% of the total destroyed exergy in the cycle, occurred in one of the heat exchangers as the main component wasting exergy. Also it was found that most the exergy efficiency is related to the one of the heat exchangers and flash separator with 99.24% and 99.11%, respectively.

A comparative investigation of solar-assisted heat pumps with solar thermal collectors for a hot water supply system

The concept of a hybrid solar collector was newly proposed, which has a solar thermal receiver part and air-source receiver part that can operate as a fin-tube exchanger with fans when there is no solar radiation. This is the distinguishing feature of the hybrid solar collector. The solar-assisted heat pump system applying the hybrid solar collectors was also introduced. To analyze the proposed solar-assisted heat pump system, a simple thermodynamic model considering the electric power consumption for fans and circulation pumps was developed. The model results for the air-source heat gain were validated from the corresponding experimental data with the maximum error of 8.8%. Based on the parametric study, the increase of the collector area and the absorption coefficient led to the enhancement of the system performance of the solar-assisted heat pump with hybrid solar collectors. In addition, a comparative investigation was carried out for three different indirect solar-assisted heat pumps. Regarding of annual operation hour, the serial-type solar-assisted heat pump was worst at 3509 h over a year. On the other hand, the solar-assisted heat pump with hybrid solar collectors had the superior performance of 7036 h. If the efficiency of the hybrid solar collector was as superior as the conventional flat plate solar collector, the system COP of the suggested solar-assisted heat pump system in the winter season could be improved by 5.1% compared with that of the parallel-type solar-assisted heat pump system. Consequently, it clearly showed the feasibility of the suggested solar-assisted heat pump system as a standalone system for hot water supply due to the merits of significantly extending the annual operation hour, the simple system configuration, and the economic aspect with lower capital cost.

Experimental study on the heat gain of water in hybrid solar collector integrated with fin-and-tube heat exchanger with respect to air and water flow rate

Solar assisted heat pump system is the system using solar thermal energy that can lead to the improvement of performance of heat pump by transferring solar thermal energy obtained from solar collector to evaporator of the heat pump for evaporation of refrigerant. In traditional system, solar collector can get a thermal energy only from solar radiation. So, the collector is hard to be used when the solar radiation is not enough such as cloudy day or night even though these collector take up much space. Thus the hybrid solar collector that has fin- and-tube heat exchanger have been developed for getting a thermal energy from not only solar radiation but also ambient air. Due to the fin-and-tube heat exchanger, this collector can get a thermal energy from ambient air for heating chilled water by evaporation of refrigerant in heat pump system. At this time, heat gain of water from ambient air by the collector needs to be confirmed before combining with real heat pump system. Thus, in this study, heat gain of water in the hybrid solar collector was investigated experimentally with respect to air and water flow rate on the various temperature difference between inlet air and water. As a results, heat gain of water was shown maximum value of 900W and it was increased with increment of air and water flow rate. Also, heat gain of water was changed linearly with increment or decrement of temperature difference between inlet air and water on the specific air and water flow rate. Furthermore, relationship between heat gain of water and operating conditions was also confirmed that can be used for decision of collector area and heat pump capacity for designing solar assisted heat pump integrated with this collector.

Optical and mechanical tolerances in hybrid concentrated thermal-PV solar trough.

Hybrid thermal-PV solar trough collectors combine concentrated photovoltaics and concentrated solar power technology to harvest and store solar energy. In this work, the optical and mechanical requirements for optimal efficiency are analyzed using non-sequential ray tracing techniques. The results are used to generate opto-mechanical tolerances that can be compared to those of traditional solar collectors. We also explore ideas on how to relieve tracking tolerances for single-axis solar collectors. The objective is to establish a basis for tolerances required for the fabrication and manufacturing of hybrid solar trough collectors.

Numerical Analysis on Thermal Efficiency of Hybrid Solar Collector with Fin-and-Tube Heat Exchanger

Numerical Analysis on Thermal Efficiency of Hybrid Solar Collector with Fin-and-Tube Heat Exchanger

Theoretical and experimental analysis of the solar collectors performances

Here, the authors present a theoretical and experimental study for the hybrid solar collector system photovoltaic thermal (PVT) compared to the conventional thermal collector CTH and the photovoltaic panel PV using a mathematical model that is developed in order to predict the performance of the system. The model is based on the equations of the energy balances of each system to see these thermal and electrical performances. The system studied consists of a PV panel welded above the outside face of a thermal system in order to cool the PV cells and increase their electrical efficiency. The results of the experimental study were compared with the theoretical data and the model was validated.

Reflective mirrors effect on the performance of the hybrid PV/thermal water collector

Hybrid PV/Thermal collector is the collector which produced electricity and hot water or hot air at the same time and working as solar cells and solar heaters. This system has been designed to increase the electrical efficiency of the solar cells by withdrawing heat from the solar cells. The present study has been carried out in Kirkuk city (latitude 35.46 and longitude 44.39), water was used as a mean to gain heat from the solar cell by passing it in a thermal exchanger, placed at the lower part of the solar cell, two proto types built to compare the thermal and electrical performance of the hybrid solar collector, the study includes making experiments for the months of (February, March, and April 2017, with a different volume flow rates, three variable designed had been studied, which includes the effect of the reflectance mirrors, glass cover and the slope angle of the lower reflector on the performance of hybrid PV/thermal water collector. The existence of the reflectance mirrors lead to increase the temperature of the solar cell, therefore, its value was (92.7 °C) when using lower and upper mirrors with a glass cover, and (76.1 °C) when using only a lower mirror, and (71.35 °C) without reflecting mirrors. The cell surface decreased to (52.75 °C) of the uncooled solar cell. The existence of the reflectors increases the total values of the thermal and electrical efficiencies. The daily total efficiency in average was a result due to use two reflectors was (81.03%), this means a positive effect on the total efficiency, and the effects of the glass cover on the total efficiency is big, the daily average of the total efficiency with and without glass cover was (58.95%) and (49.97%) respectively, these results are accorded with the results of the previous articles.

Numerical Study on Radiation Effects to Evaporator in Natural Vacuum Solar Desalination System

The need for clean water is increasing day by day due to the increasing factor of living standard of mankind, hence designed natural vacuum solar desalination. The natural vacuum Solar desalination is studied experimentally. A small-scale natural vacuum desalination study consists of evaporator and condenser as the main components designed and manufactured. To transfer heat from the solar collector into the evaporator, the fluid transfer system uses a pump powered by a solar cell. Thus, solar collectors are called hybrid solar collectors. The main purpose of this exposure is to know the characteristics of the radiation effects on incoming energy on the evaporator during the process. This system is tested by exposing the unit to the solar radiation in the 4th floor building in Medan. The experiment was conducted from 8.00 to 16.00 local time. The results show that natural vacuum solar desalination with hybrid solar collectors can be operated perfectly. If the received radiation is high, then the incoming energy received by the evaporator will also be high. From measurements with HOBO microstation, obtained the highest radiation 695.6 W/m2, and the calculation result of incoming energy received evaporator obtained highest result 1807.293 W.

Tests and theoretical analysis of a pvt hybrid collector operating under various insolation conditions

The main goal of the study was to investigate the relationship between the orientation of the PVT (PhotoVoltaic Thermal) collector and the thermal and electric power generated. Extensive research was performed to find optimal tilt angles for hybrid solar thermal collectors, which combine photovoltaic as well as thermal collection in a single unit, known as PVT (PhotoVoltaic Thermal) modules for an office building with working hours between 7.00 and 16.00. The comprehensive study included field measurements of the modules in central Poland and tests under AM (air mass) 1.5 conditions in a certified laboratory KEZO (Centre for Energy Conversion and Renewable Resources) Polish Academy of Sciences in Jablonna. Furthermore, a PVT system was investigated using the simulation method based on the dedicated Polysun software. The PV characteristics and efficiency of the PV module and the relation between power or efficiency of the PVT module and incidence angle of solar-irradiance were studied. Optimal work conditions for commercial PVT modules were ascertained. In addition, it was found that the maximum efficiencies of PV module (ηPV), solar thermal-collector (ηc) and PVT hybrid collector (ηPVT) registered under field conditions were higher than the ones measured under laboratory conditions.

Experimental investigation on a hybrid solar collector to predict safe operating condition

ABSTRACTSolar energy, a non-polluting source of power generation is widely used in the recent times in many engineering applications. While using this solar energy on the solar panels with a tracking system, the panel gets damaged due to excess radiation. To overcome this problem, in the present work, fins and PCM (Phase Change Material) are used to reduce the temperature of the panel and thereby increases its life. Fins and PCM are attached to the photovoltaic panel and experiments were conducted with fins and PCM and the results are compared without fins and PCM. The experiment is conducted in the following means namely, tracking and without tracking. Besides, the temperature, voltage and current are measured and hence the power output was evaluated.

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

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