Flat Solar Collector Research Articles

Perspectives of using Israel's experience in solar hot water supply in Ukraine

This article raises questions about the use of alternative energy sources, the relevance of which currently and in the near future does not cause any doubts. Particular attention is paid to the problem of the average use of alternative sources in the energy sector of Ukraine. At the same time, the emphasis is placed on such a direction of ensuring comfortable living conditions as satisfaction of the population with stable and inexpensive heat for heating and hot water supply systems with the use of modern solar energy systems.To achieve this goal, the article formulated a number of problems that could more fully represent the disturbed topic.Some aspects of the state of the world energy market and the need to develop renewable energy sources, including solar radiation, are set out in the material to highlight the problems raised.With a view to possible use in the Ukrainian energy sector of solar radiation, Israel's many years of experience in the successful use of hot water heliosystems for domestic needs was considered.The estimation of the climatic conditions of Ukraine, which represents the good possibilities of using solar thermal energy in providing the proper conditions for comfortable living, is given.The state approaches in Ukraine and Israel for realization of national programs of development of solar energy, aimed at increasing the share of heat received in this direction in the general energy system are considered.The international, European and national standards of both states regarding the requirements for solar collectors with comparative analysis of indicators for their testing are presented.The state of production, practical use of equipment for solar hot water supply systems is analyzed, the main manufacturers and suppliers of this equipment are presented in the markets of both countries. In the tabular form a comparative analysis of the main technical characteristics of flat solar collectors of the leading manufacturers of the European Union and the State of Israel, presented in the Ukrainian market is presented.The list of problems, which is a restraining factor in realization of tasks on development of solar power systems, is shown. After the article conclusions and recommendations on the above-mentioned problems are made.

Computer model of control of a flat solar collector with a thermosifon circulation

This paper discusses the possibility of creating a digital platform based on Mojo v3 for monitoring the operation of a dual-circuit solar collector. In the proposed system, measurements are made from 6 digital sensors (DS18B20 Dallas), 16 wires are used. Using Dallas sensors and the appropriate software, you can monitor the temperature level and the amount of heat. The use of 6 digital sensors significantly increases the efficiency of control over the system and increases the speed of data processing. The possibilities of configuring sensors for the platform Mojo v3, as well as the control circuit of the solar collector are considered.

Use of microbial fuel cells and solar collectors in the multifunctional energy container

The results of studies of a multifunctional energy container are given. The use of microbial-fuel cells for generating electricity, as well as flat liquid solar collectors for generating thermal energy, has been investigated in the energy container.

Research and Calculation of the Coefficient for the Solar Radiation of a Flat Solar Collector

Research and Calculation of the Coefficient for the Solar Radiation of a Flat Solar Collector

EXERGY ANALYSIS OF DOUBLE-CIRCUIT FLAT SOLAR COLLECTOR WITH THERMOSYPHON CIRCULATION

In the present work, an exergy analysis was done of two-circuit flat solar collector with thermosiphon circulation. The article presents a mathematical model of energy and exergic analysis of flat solar collectors, as well as calculations of solar radiation efficiency, temperature, flow rate of the fluid, exergy rates and exergy loss rates are done. The significance of the results achieved is high, since experimental studies can detect inefficient components of the solar heating system. The exergetic efficiency of a dual-circuit flat solar collector with a thermosiphon circulation describes irreversibility of the process according to thermodynamic parameters. This is caused by a large the degree of overheating achieved at the end of the processes of compression and evaporation, which leads to large differences in heat exchange temperature based on the heat pump cycle. The exergy efficiency value for the entire system is 70. Maximum values energy efficiency and exergy at noon, 32.5% and 2.23%, respectively. The efficiency of exergy is 4%, and the highest the loss of exergy is the difference between the absorber plates and the sun, accounting for 52.86% of the total exergy rate.

Comparative study of two types of mini chicanes concentrators implanted in solar collector

Saving energy and protecting the environment are the cornerstones of the modern concept of energy consumption. Following the Algerian program on renewable energies and energy consumption, dictated by Algeria's new energy transition policy, 40% of electricity production should come from renewable energies by the year 2030. The present article accompanies this policy and makes an attempt to improve the energy efficiency. This work presents a comparative experimental study of two models of flat plate air solar collectors, namely a solar collector with black mini solar concentrators (BMSC) and another model, similar to the first one, with the same geometry and dimensions, and supplied with mini solar concentrators and mirrors (MSCMR) instead of black mini solar concentrators. A comparison of the temperature profiles for these two models of solar collectors is performed in this work, in the two cases of free convection and forced convection. Comments on this innovative design are presented and the results obtained are found encouraging.

Theoretical And Mathematical Analysis Of Double- Circuit Solar Station With Thermo Siphon Circulation

This article discusses the mathematical models of the individual structures and modes of operation of a double-circuit solar collector with thermo siphon circulation. To perform this task, we considered a new design of a flat solar collector with thermo siphon circulation, in which the heat transfer coefficient was increased by eliminating additional partitions between the panel and thermal insulation. The efficiency of the solar collector is achieved due to the presence of the metering tank and the heat pump in the tank, where the condenser and evaporator are made in the form of a “spiral in a spiral” type heat exchanger, and the heat exchanger pipelines are placed one above the other, which allows increasing the area and intensity of heat exchange. The result of this work is a theoretical and mathematical analysis of the unsteady thermal regime of flat solar collectors on the modes of operation under consideration. Based on the results of the analysis, it is possible to optimize individual structural elements, as well as to predict the thermal regime and select alternative solutions for the design of flat solar collectors and the choice of operating modes.

A novel PVT/PTC/ORC solar power system with PV totally immersed in transparent organic fluid

A novel hybrid PVT/parabolic trough concentrator (PTC)/organic Rankine cycle (ORC) solar power system integrated with underground heat exchanger has been proposed. The evaporator unit consists of a transparent flat PVT solar collector and a PTC connected in series. The first transparent solar collector has transparent covers and consists of solar cells totally immersed within a pressurized transparent organic fluid that allows the solar radiation to reach the solar cells, cools them effectively, and captures all thermal losses from the solar cells. The second concentrator is a conventional one with opaque black receiver used to reheat the transparent organic fluid to higher temperatures. Both solar collectors (the PVT and PTC) perform as the boiler and superheater for the ORC. The performance of the proposed system is investigated by a steady-state mathematical model. The results show that, at design conditions, the efficiency of the PV modules stabilizes around 12%, absorber efficiency varies within 64% to 75%, and the ORC efficiency varies within 7% to 17%.

An active indirect solar system for food products drying

Abstract An energy independent active indirect solar drying system for the study of food products drying at specific climate conditions was developed and tested. As a model material, sliced tomato was selected because of its short shelf live, high humidity and potential to be a high value dried product. Indirect solar dryer enabled complete protection of the dried material against sunlight, birds, insects, rain and dust during the drying process. The solar dryer system design includes a rectangular section (1000 × 600 × 400) mm chamber and a flat solar collector (1500 × 600 × 100) mm with the surface area of 0.9 m2. Air flow was induced by a fan installed at the inlet of the collector and powered by a photovoltaic solar panel and a battery system. Temperature and humidity of air were monitored at the collector inlet, collector outlet and the drying chamber outlet. The key element of the collector is a 10.5 m long rectangular section aluminum pipe (55 × 35) mm coated with an absorption layer. The maximum dryer capacity is around 3 kg of wet material (sliced tomato) per batch. Average air temperature increase in the collector was measured to be 30 °C during the winter season. Air relative humidity decreased from 21 % to 15 % after passing through the collector. The moisture of tomato slices decreased from the initial value of 92 % down to 22 % during the time of the experiment (30 h). Quality of tomatoes dried using the designed solar dryer differed significantly in color as well as in texture from those dried by the commonly used methods, like an open sun drying system. Equilibrium moisture content of the product was reached after 30 h in December when the maximum outside temperature was 17.6 °C. The tomato mass decreased from 333 g to 33.15 g; the mass loss being approximately 90 %. The heated air temperature and humidity at the dryer inlet and outlet were influenced by the change of the ambient temperature and humidity during the day. Variation of the drying rate with the change of the ambient temperature and humidity was observed. During summer, when the sun radiation increases, the drying time for sliced tomato with 9 mm thickness decreased from 25 h to 15 h. The sample thickness also has an impact on the drying process. When the sample thickness increased from 9 mm to 12 mm, the drying time increased from 15 h to 20 h of active device time.

Design and Experimental Investigation of a Novel Solar Collector with a W-Shape Cover

In the current study, we developed and tested a new type of solar collector named W-shape solar collector. It is a solar collector with single air pass between the transparent cover and the absorber. The cover has double glass whereby the upper glass is flat and the lower glass is w-shape. The absorber is also W-shape. This combination gave rise to an undulatory airflow circulation in the new collector. This modular solar collector allowed the functioning of several configurations of flat plate solar thermal collector. After realization of the prototype, an experimental characterization was done during a natural period of sunshine in the town of Ngaoundere between November and December 2016. It consisted in characterizing the solar radiation, the input/output temperatures of the solar collector, the temperature of the absorber and the air velocity profile. During the experiments, the solar collector was directed facing the south and tilted either by 45°or by 30° compared to the horizontal plan. Temperature profile analysis showed at noon sun and air velocity of 0.3 m/s, the outlet air temperature of the w-shape solar collector gives 75°C while that of the flat collector gives only 60°C. Nevertheless, the temperature of the flat absorber was higher than that of the W-shape absorber. This allowed us to conclude that the convection heat transfer coefficient of the W-shape solar collector improved than the flat solar heat collector. Also the efficiency profiles highlight the positive contribution of the W-shape in the improvement of the thermal performances of a solar collector.

Techno‐economic analysis of applying linear parabolic and flat plate solar collectors for heating a building and their comparative evaluation

In this study, utilizing two types of solar collectors, including linear parabolic (LPC) and flat solar (FPC) collectors to heat a residential building was investigated from technical and economical point of views. The performance of these two systems were obtained and compared with each other in the cold months of the year in the South‐East of Iran. The building and the heating systems were simulated in the TRNSYS software. Both the heating systems were separately analyzed from the energy and economic point of views. Results showed that the FPC and LPC heating systems delivered 51.3% and 46.7% of the received solar energy to the building, respectively. The results also showed that the solar fractions of the LPC and FPC heating systems are 22% and 8.6%, respectively. It was found that the thermal storage tank in the FPC hearing system is more useful than the LPC heating system as the LPC heating system with storage tank has a lower rate of heat loss compared to the system with no thermal storage tank. The rate of return investments in the FPC and LPC heating systems were 18.1% and 22.8%, respectively. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13121, 2019

ВИЗНАЧЕННЯ ОПТИМАЛЬНОГО КУТА НАХИЛУ ПЛОСКОГО СОНЯЧНОГО КОЛЕКТОРУ ЗАЛЕЖНО ВІД ЙОГО ОРІЄНТАЦІЇ ТА ВІРОГІДНОСТІ СОНЯЧНОГО СЯЯННЯ

A method of determining the optimum angle of inclination of a flat solar collector to the plane of the horizon, depending on its orientation and the probability of sunshine in the area of construction, is developed. The curves of maximum (astronomical) and statistical duration of sunshine in hours for Sarny city of Rivne region are given. These curves depend on the number of the year day. The probability of sunshine is also shown depending on the day of the year. This curve was calculated as the ratio of the statistical sunshine duration to the maximum. The statistical duration of sunshine was taken from the observations of an actinometric station in Sarny city and the maximum duration was calculated in the program developed by the authors. Also there is surface of incoming solar radiation in one square meter depending on the orientation and angle of inclination of the plane of the solar collector to the plane of the horizon. The shape of this surface gives a clear idea of this dependence, but is inconvenient for practical use. The surface itself is formed from curves of dependence of energy supply on one meter square of the collector plane from the angle of its inclination to the plane of the horizon. These curves were calculated for ten collector orientations. The orientation varied from south to east in ten degree increments. All curves have one maximum. This made it possible to build the optimal curve collector angle to the plane of the horizon from its orientation. For comparison, a similar curve was shown. But it was built without taking into account the probability of sunshine. This curve illustrates the substantial dependence of optimal angle of the probability of sunshine (optimally be much greater angles). The method can be used (if statistics are available for the construction area) for other periods of the year, for example, spring-summer-autumn, given that in certain areas of construction snow may lie on the collector planes for a long time. Other periods of the year may also be used for climate-related reasons, such as electricity schedules. Keywords: flat solar collector, astronomical and statistical duration of insolation, the probability of sunshine, optimum tilt angle, integral atmospheric transparency coefficient, orientation of the solar collector, mass of atmosphere.

Исследование предварительного подогрева теплоносителя комплексным энергозамещающим устройством в тепловых процессах переработки молока

Energy input affects the final cost of dairy products. The paper features energy cost optimization in dairy industry and, in particular, in the production of cultured milk foods. The present research studies the options for renewable energy sources in dairy industry: solar system is becoming a very promising means of energy saving in the southern regions. The authors proposed a complex energy substitution device, which can reduce the electricity costs by 60–70%, according to preliminary calculations. The results obtained in the theoretical underpinning of design parameters and operation modes were checked by experimental studies. For the experiment, the authors designed and manufactured a water heating system based on flat solar collectors. An instrument complex registered temperature values in eight different control points and transferred the signals to a PC hard disk. The article presents the parameters of the equipment in pasteurization and milk fermentation processes with the use of the complex energy substitution device for water heating. The equipment can be used by large-scale dairy enterprises, since the area of the collectors for the preliminary water heating is 2 m2, which provides 150 litters of water with a temperature of 45–60°C. As the normative parameters of the temperature during the milk fermentation process is 32–35°C, and the water temperature in the device is 45–60°C, it can be concluded that the thermal costs are fully covered.

Performance Estimation of Solar Flat Plate Air Heating System Using Helical Tapes

Solar flat plate collectors (FPC) are used for heating spaces, water heating, and many other purposes. The present technology of solar flat collectors uses vertical fins. The solar flat plate collector having absorber with vertical fins is provided with a helical tape in the fluid flow path. The absorber plate in the solar flat plate collector has an area of 100 cm x 50 cm. The solar flat plate collector has nine ducts with an area of 27.5 cm x 9.5 cm each. The helical tapes attached have a start angle of 64 deg which pass along the whole length of the duct. The helical tapes have a crosssection area of 1.5 mm x 4 mm. The pitch of the helical tapes is 100 mm. These fins have been attached between the vertical fins of the thickness of 1mm and a height of 10.5 cm. Data such as inlet temperature, outlet temperature efficiency and convective heat transfer coefficient are calculated. The mass flow rate of air is 10.28 kg/s and the air is subjected to solar radiation between 628.98 W/m2 and 708.59 W/m2. The values are noted down, and the and the efficiency is noted to have a 10% rise. The effectiveness of the solar plate collector will increase using a helical fin. A comparative analysis will be done between the conventional flat plate collector and the setup with the helical tapes. The study will show that the helical tapes in flat plate collector will be the best alternative compared to conventional flat plate collector.

CFD simulation of natural convection and heat transfer in a flat solar thermal collector with fins on the glazing - horizontal case

This study is based on a CFD simulation of a flat horizontal solar thermal collector containing fins on its inner face of the glazing. The walls of the solar collector with insulation are considered adiabatic and the rest of the walls are at constant different temperatures. The principal objective of this work is to study the effects of the number of fins that changed from 0 to 30, as well as their length varied from 0 to 0.8 on the air flow and heat transfer characteristics. It has been observed that the heat transfer rate is strongly affected by the number of fins and the length of the fins. The obtained result showed that the increase of the fins reduces the heat loss by convection by 54 %.

Numerical study of heat transfer in a flat plat thermal solar collector with partitions attached to its glazing

Heat transfer in the air-gap of a horizontal flat plat thermal solar collector contain partitions attached to its glazing has been studied numerically. The absorber and the glazing are kept at constant and different temperatures, while the vertical walls (insulation) were kept adiabatically. A conjugate formulation was used for mathematical formulation of the problem and a computer program based on the control volume approach and the SIMPLER algorithm was used. The main aim of the current paper is to study numerically the effects of number of fins and their length on the air pattern and heat transfer. It was observed that the heat transfer rate through the air-gap is affected greatly and hence can be controlled by the number of attached fins to the glazing of the solar collector as well as the fin lengths, and the addition of partitions reduces the heat losses by convection by 90%.

Numerical laminar forced convection modelling in a ceramic and concrete solar collector with non-circular duct

The paper presents simulations of laminar forced convection in non-circular piping of flat solar collectors made of ceramics or concrete, which are characterized by a low thermal conduction coefficient. The cross-sections of piping in the shape of a regular polygonal, elliptic, superellipse (Lamé curve) and Cassini oval were used for the calculations. In order to perform the simulation, a simplified two-dimensional model of laminar forced convection in a straight axis duct was used and the issue of H2 (constant axial wall heat flux with uniform peripheral wall heat flux) for materials with low thermal conductivity was applied. The calculations were made using the boundary element method (BEM) in a calculation program written by Fortran by the author. In the work, the number of Poiseuille, Nusselt and dimensionless parameters for the evaluation of heat exchangers such as the area goodness factor and the volume goodness factor were determined in the function of characteristic geometrical parameters of the assumed cross-sectional shapes of the flat solar collector piping.

The Graphic Analytical Method of Flat Solar Collector Energetic and Optical Characteristics

The Graphic Analytical Method of Flat Solar Collector Energetic and Optical Characteristics

An experimental study of solar thermal system with storage for domestic applications

Building sector consumes a greater portion of energy for heating and cooling applications. The utilization of fossil fuels for space and water heating in buildings cause a negative effect on the environment by producing larger CO2. In this study solar thermal water heating system for building application have been analyzed from the first and second law perspectives of thermodynamics considering various scenarios and water consumption pattern. The solar flat collector is very commonly used to extract energy from sunlight. Therefor energy and exergy efficiency curves for the solar flat collector were presented. The energetic and exergetic values for the system were calculated based on the experimental values for the overall system, the heat exchanger and the pumps using the approach of exergetic product/fuel basis. The greatest and lowest relative irreversibility’s occurred at the solar collector and the heat exchanger with values of 85.73% and 2.45%, respectively, and the system overall exergy efficiency was determined to be 20.28%. The energy and exergy efficiencies of the solar collector were analyzed at three different cases depending on the mass flow rates in the solar collector and the secondary circuit of the system. Three different mass flow rates were applied to the inlet of the secondary circuit to observe the efficiency effect on the solar collector circuit. This study can assist in selecting a proper solar collector and storage size for buildings of various capacity and possible improvement in the design of the system components.

Numerical analysis of heat transfer rate from absorber of a flat-plate type solar collector to the tube

Flat plate type solar collector is known as the simplest solar collector. However, its thermal efficiency is very low in comparison with other type of solar collector such as evacuated tube. The heat transfer mechanism in the flat plate type solar collector should be elaborated to improve thermal efficiency of a flat plate type solar collector. In this work, commercial code computational fluid dynamics is employed to explore heat transfer rate from the collector plate to the collector tube. The objectives are to explore the fluid flow characteristics in the solar collector and to estimate the useful heat transfer rate. The solar collector is modelled as a two-dimensional computational domain. The conservation mass, momentum equations and energy equations are developed and solved iteratively. Temperature and pressure distributions are plotted and velocity vector is presented. The results reveal that the heat transfer rate from the absorber plate is 28.955 Watt. The transfer rate from the air to the pipe is 24.06 Watt. On the other hand, heat loss to the atmosphere is 4.92 Watt.