scholarly journals Experimental and Theoretical Analysis of a Linear Focus CPV/T System for Cogeneration Purposes

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2960 ◽  
Author(s):  
Carlo Renno
Keyword(s):  
Focal Length ◽  
Concentration Field ◽  
Operating Conditions ◽  
Working Fluid ◽  
Fluid Temperature ◽  
Atmospheric Conditions ◽  
High Concentration ◽  
Environment Temperature ◽  
Temperature Levels ◽  
T System

The knowledge of the actual energy performances of a concentrating photovoltaic and thermal (CPV/T) system with a linear focus optics, allows to evaluate the possibility of adopting this type of system for cogeneration purposes. Hence, the main aim of this paper is the design, realization, setting and modeling of a linear focus CPV/T system in the high concentration field. An experimental linear focus CPV/T plant was created in order to determine its electrical and thermal performance under different working conditions in terms of environment temperature, sunny and cloudy conditions, focal length, etc. Moreover, a theoretical model of the linear focus CPV/T system was also studied. This model evaluates the temperatures of the working fluid that flows in the cooling circuit of the CPV/T system under several operating conditions. The temperatures of the triple junction (TJ) cells, experimentally evaluated referring to different solar radiation and atmospheric conditions, were considered as the input data for the model. The values of the fluid temperature, theoretically and experimentally determined, were thus compared with good agreement. The electrical production of the CPV/T system depends generally on the TJ cell characteristics and the concentration factor, while the thermal production is above all linked to the system configuration and the direct normal irradiance (DNI) values. Hence, in this paper the electric power obtained by the linear-focus CPV/T system was evaluated referring to the cogeneration applications, and it was verified if the TJ cell and the cooling fluid reach adequate temperature levels in this type of system, in order to match the electrical and the thermal loads of a user.

scholarly journals Theoretical and Experimental Evaluation of the Working Fluid Temperature Levels in a CPV/T System

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3077
Author(s):  
Carlo Renno
Keyword(s):  
Thermal Energy ◽  
Integrated System ◽  
Hot Water ◽  
Experimental Comparison ◽  
Working Fluid ◽  
Fluid Temperature ◽  
Cooling Fluid ◽  
Operation Conditions ◽  
Temperature Levels ◽  
T System

A linear focus Concentrator Photovoltaic and Thermal (CPV/T) system can match the thermal demands of a user. The evaluation of the cooling fluid temperature levels of a CPV/T system is fundamental to understand if this system is capable of satisfying the typical thermal requirements of a residential user (heating, cooling and domestic hot water). First, an experimental line-focus CPV/T system, realized in the Laboratory of Applied Thermodynamics of the University of Salerno (Italy), has allowed to determine the cooling fluid temperature at the CPV/T system outlet. Successively, the cooling fluid temperatures, experimentally obtained, have been compared with the same temperatures calculated by means of a theoretical model under the same operation conditions. A deviation in terms of the percentage relative error between theoretical and experimental results included between about 0.5% and 5%, has been found. The goodness of the theoretical–experimental comparison in terms of the temperature of the operation fluid at the CPV/T system outlet has represented a fundamental point to evaluate theoretically, by means of the TRNSYS software, the other levels of temperature of an integrated system, constituted by CPV/T system, thermal tank and user, for different temporal scenarios (hourly, weekly, monthly and yearly). The input data of the TRNSYS model are: Direct Normal Irradiance (DNI), Triple-Junction (TJ) cell temperature and environmental conditions. A tank model is also adopted to satisfy the thermal energy demand peaks, and the temperature stratification in the tank linked to the CPV/T system, as function of the height, is obtained in winter and summer. It is important to define these thermal levels to verify if a CPV/T system is capable to satisfy the residential user energy demands or a thermal energy integration is necessary in some periods of the year. A good stratification has been noted in the summer season, with temperature values that are variable between about 40 and 90 °C. From April to October, the tank average temperature is generally resulted about 10 °C higher than the temperature required by the fluid sent to the residential user, and a very low integration is then necessary. It has been verified that the CPV/T system covers a large part of the thermal energy needs of the residential user during the year; the coverage is limited only in the winter months.

scholarly journals Numerical Study of Natural Convection Heat Loss from Cylindrical Solar Cavity Receivers

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
M. Prakash
Keyword(s):  
Natural Convection ◽  
Cylindrical Cavity ◽  
Numerical Study ◽  
Three Dimensional ◽  
Working Fluid ◽  
Helical Coil ◽  
Fluid Temperature ◽  
Medium Temperature ◽  
Inclination Angles ◽  
Temperature Levels

The numerical study of the natural convection loss occurring from cylindrical solar cavity receivers is reported in this communication. These cavity receivers can be used with solar dish concentrators for process heat applications at medium temperature levels. Three cylindrical cavity receivers of diameter 0.2, 0.3, and 0.4 m with aspect ratio equal to one and opening ratios of 1 and 0.5 are used for the analysis. Fluent CFD software is used for the analysis of the three-dimensional (3D) receiver models. In this study the receiver tubes within the cylindrical cavity are modeled as a helical coil similar to those existing in actual systems. The flow of the working fluid within the helical coil is also modeled. The simulations are performed for fluid inlet temperatures of 150°C and 250°C and for receiver inclination angles of 0 (sideways-facing cavity), 30, 45, 60, and 90 degree (vertically downward-facing receiver). It is found that the convective loss increases with increasing mean fluid temperature and decreases with, increase in receiver inclination. The convective loss is found to increase with, opening ratio. These observations are true for all cavity receivers analysed here. A Nusselt number correlation involving Rayleigh numbers, receiver inclinations, and opening ratios is proposed for the convective loss.

Performance Analysis of Photovoltaic Thermal (PVT) Panels Considering Thermal Parameters

2016 ◽  
Author(s):  
W. J. A. Jayasuriya ◽  
A. U. C. D. Athukorala ◽  
A. T. D. Perera ◽  
M. P. G. Sirimanna ◽  
R. A. Attalage
Keyword(s):  
Wind Speed ◽  
Performance Analysis ◽  
Mass Flow ◽  
Flow Analysis ◽  
Operating Conditions ◽  
Solar Irradiation ◽  
Heat Transfer Fluid ◽  
Design Parameters ◽  
Working Fluid ◽  
Fluid Temperature

Solar PVT panels are getting popular for wider spectrum of applications for concurrent heat and power generation (CHP). These panels can provide the heating demand of buildings while generating electricity which becomes ideal for building applications of urban energy systems. Energy flow analysis of such panels and performance analysis of such systems becomes essential to design PVT systems matching with the operating conditions. A number of studies have used both theoretical and experimental methods to optimize PVT. However, this task is challenging due to interrelation of CHP production based on two different phenomena where classical optimization methods cannot be applied directly. Hence basic performance analysis considering primary design parameters plays a major role. In this study, a computational model is developed to evaluate sensitivity of design, operating and climatic parameters for a hybrid PVT system and to analyze the performances of PVT for five different design configurations. Five main configurations of the PVT system are considered based on the heat transfer fluid and the arrangements of glass and tedlar layers of PVT collector. This study presents comprehensive performance analysis conducted to evaluate the sensitivity of mass flow rate and working fluid temperature for the five different design configurations of PVT panels. Results show that glass-tedlar water collector performs better when compared to other configurations. Subsequently, the sensitivity of wind speed and solar irradiation is evaluated. The behavior of thermal and electrical efficiencies is analyzed at different wind speed and solar irradiation levels for a range of mass flow rates and working fluid temperatures. Important conclusions on the performance of PVT panels are given based on this detailed analysis.

scholarly journals Parametric Analysis of a Polygeneration System with CO2 Working Fluid

2021 ◽  
Vol 11 (7) ◽  
pp. 3215
Author(s):  
Evangelos Bellos ◽  
Christos Tzivanidis
Keyword(s):  
Heating Temperature ◽  
Operating Conditions ◽  
Critical Parameters ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Present System ◽  
High Heating ◽  
Pressure Medium ◽  
Polygeneration System ◽  
Temperature Levels

The objective of the present work is the investigation of a novel polygeneration system for power, refrigeration and heating production at two temperature levels. The present system uses CO2 as the working fluid, which is an environmentally friendly fluid. The total configuration is a combination of a transcritical refrigeration cycle coupled to a Brayton cycle with recompression, which is fed by a biomass boiler. The examined system, at nominal operating conditions, produces refrigeration at 5 °C, and heating at 45 °C and 80 °C. Additionally, the system can be converted into a trigeneration system where the two heating outputs are produced at the same temperature level. The system was studied parametrically by changing the following seven critical parameters: turbine inlet temperature, high pressure, medium pressure, heat exchanger effectiveness, refrigeration temperature, heat rejection temperature and high heating temperature. In nominal operating conditions, the system energy and exergy efficiencies were 78.07% and 26.29%, respectively. For a heat input of 100 kW, the net power production was 24.50 kW, the refrigeration production was 30.73 kW, while the low and high heating production was 9.24 kW and 13.60 kW, respectively. The analysis was conducted with a developed model in Engineering Equation Solver.

Numerical and Analytical Analyses of a High Temperature Heat Exchanger

2006 ◽  
Author(s):  
Donato Aquaro ◽  
Franco Donatini ◽  
Maurizio Pieve
Keyword(s):  
High Temperature ◽  
Heat Exchanger ◽  
Analytical Model ◽  
Electric Utility ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Working Fluid ◽  
Fluid Temperature ◽  
Test Loop ◽  
Temperature Heat

In this paper some analytical and numeric analyses of a high temperature heat exchanger are performed. This heat exchanger should be employed in a test loop of a EFCC (Externally Fired Combined Cycle), placed in a experimental facility owned by the Italian electric utility, ENEL. The heat exchanger is the crucial element in this cycle, as it undergoes temperatures above 1000°C and pressures of about 7 bars. The enthalpy of the combustion products of low cost fuels, such as coal, bottom tar, residuals from refineries, is used to heat a clean working fluid, in this case pressurized air. There are some outstanding benefits for the turbine, in regard to the manufacturing and maintenance costs, and also for its life. The heat transfer components are some bayonet tubes, assembled in 4 modules. A half of them is made of ceramic materials, the others of an advanced metallic material (ODS), due to the burdensome operating conditions. First of all, the heat exchanges are evaluated by means of a simplified analytical model. The radiant contribution also has been taken into account, due to the presence of non-transparent gases. Subsequently, the in-tube fluid temperature increase is calculated for all the heat exchanger modules, through an enthalpy balance and with some simplifying assumptions. Moreover, a comparison is made between the analytical solution and the results of a numerical model implemented in a CFD code. A good agreement is found, which indicates that the analytical model is reasonably valid. In fact, the whole heat exchanger temperature change is determined by means of the two methods with a difference of about 7% for both the streams. Finally, these results are to be compared with the experimental data which should be available in the near future, when the facility will begin working. Also, by this way, the developed calculation model would get a validation.

Performance Evaluation of Asymmetric CPC-PVT Collectors Connected in Series

2017 ◽  
Author(s):  
M. T. Nitsas ◽  
I. P. Koronaki
Keyword(s):  
Open Circuit ◽  
Operating Conditions ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Solar Collectors ◽  
In Series ◽  
Reflector Geometry ◽  
Temperature Levels ◽  
Useful Heat ◽  
Fundamental Equations

In this study, a series of thermal-photovoltaic collectors with hybrid reflector geometry and flat plate receiver is investigated experimentally and analytically through fundamental equations regarding solar collectors. The series of five compound parabolic thermophotovoltaic collectors are located in Athens, Greece and the experiments took place in June at open circuit state, i.e. the collectors were not electrically connected. The developed model combines optical and thermal analysis. The main objective of this study is to determine the thermal and the exergetic performance of the collectors under various operating conditions. For these reasons, the developed model is validated with the respective experimental data and afterwards, the solar collector model is examined parametrically for different tilt angles. The experiments are performed with water as heat transfer fluid and for low temperature levels up to 60°C. The final results proved that the investigated solar collectors are able to produce about 2.8 kW useful heat for low working fluid mass flow rates exhibiting at the same time an exergetic efficiency of nearly 1.4%. Also, the results of the developed model showed that the maximization of the produced thermal energy during summer occurs at a tilt angle of 10°.

scholarly journals Assessment of Hydrostatic Temperature Conditions Machine Plate Supports

2019 ◽  
pp. 1-6
Author(s):  
Almokhammad A. Mokhammad ◽  
Evgeny A. Sorokin ◽  
Maksim V. Brungardt
Keyword(s):  
Support System ◽  
Metal Cutting ◽  
Experimental Studies ◽  
Hydraulic Drive ◽  
Operation Time ◽  
Operating Conditions ◽  
Working Fluid ◽  
Fluid Temperature ◽  
Operational Conditions ◽  
Temperature Deformations

The working fluid temperature in the hydrostatic support system of the metal working machine plate is determined as a function of the drive operation time under different operating conditions. Temperature deformations of parts, units and assemblies of metal cutting machines are greatly influenced by the temperature of hydraulic drive working fluid, so the issues of optimization of working fluid temperature are given more attention. Experimental studies of the operating fluid temperature of the hydraulic support system of the faceplate and parameters affecting its changes were carried out under conditions close to operational conditions. Parts of different mass (0.5-3.8 t) were processed at different speeds of plate rotation

A Numerical Model for Off-Design Performance Prediction of Parabolic Trough Based Solar Power Plants

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Giampaolo Manzolini ◽  
Andrea Giostri ◽  
Claudio Saccilotto ◽  
Paolo Silva ◽  
Ennio Macchi
Keyword(s):  
Numerical Model ◽  
Performance Prediction ◽  
Power Plants ◽  
Solar Power ◽  
Operating Conditions ◽  
Working Fluid ◽  
Design Calculation ◽  
Fluid Temperature ◽  
Parabolic Trough ◽  
Design Algorithm

This paper deals with the development and testing of an innovative code for the performance prediction of solar trough based concentrated solar power (CSP) plants in off-design conditions. Off-design calculation starts from data obtained through the on-design algorithm and considers steady-state situations. The model is implemented in flexible software, named patto (parabolic trough thermodynamic optimization): the optical-thermal collector model can simulate different types of parabolic trough systems in commerce, including a combination of various mirrors, receivers and supports. The code is also flexible in terms of working fluid, temperature and pressure range, and can also simulate direct steam generation (DSG) plants. Solar plant heat and mass balances and performance at off-design conditions are estimated by accounting for the constraints imposed by the available heat transfer areas in heat exchangers, as well as by the characteristic curve of the steam turbine. The numerical model can be used either for single calculation in a specific off-design condition or for complete year simulation, by generating energy balances with an hourly resolution. The model is tested with a view to real applications and reference values found in literature: results show an overall yearly efficiency of 14.8% versus the 15% encountered in the Nevada Solar One. Moreover, the capacity factor is 25%, i.e., equal to the value predicted by sam®. Code potential in the design process reveals two different aspects: it can be used not only to optimize plant components and layout in feasibility studies but also to select the best control strategy during individual operating conditions.

Parametric Investigation of Concentrating PV/T System With Spectral Filtering Utilizing a 2-D Model

2015 ◽  
Author(s):  
Nick Brekke ◽  
Todd Otanicar ◽  
Drew DeJarnette ◽  
Parameswar Harikumar
Keyword(s):  
Optical Filter ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Fluid Temperature ◽  
Spectral Filtering ◽  
Temperature Variations ◽  
Cell Efficiency ◽  
Pv Cell ◽  
D Model ◽  
T System

Hybrid photovoltaic/thermal (PV/T) systems are continually being investigated, in particular the use of such systems in concentrating collectors as part of the ARPA-E FOCUS program. While many combined thermal and electrical models exist, most are limited to 0-D energy balance approaches or 1-D approaches where temperature variations through insulation, glazing and substrates are considered. Here, we develop a 2-D model for a concentrating PV/T system where the model accounts for temperature variations along the length of the collector. The proposed configuration consists of a GaAs cell laminated to an aluminum extrusion. The working fluid, a transparent high temperature heat transfer fluid with suspended nanoparticles, flows through the extrusion where it actively cools the PV cell before passing in front of the cell acting as an optical filter. The model includes PV cell efficiency, temperature, and bandgap dependence, a detail often neglected in prior works. This paper focuses on PV efficiency along the length of the system and outlet fluid temperature for both counter and parallel flow arrangements. Of particular interest here is the wavelength used in the design of the fluid filter and how changing the design impacts the exergetic efficiency and percent of exergy created as heat.

Stirling Engines With a Chemically Reactive Working Fluid—Some Thermodynamic Effects

1977 ◽  
Vol 99 (2) ◽  
pp. 284-287 ◽  
Author(s):  
M. M. Metwally ◽  
G. Walker
Keyword(s):  
Heat Pumps ◽  
Substantial Improvement ◽  
Regenerative Process ◽  
Operating Conditions ◽  
Working Fluid ◽  
Nitrogen Tetroxide ◽  
Specific Output ◽  
Stirling Engines ◽  
Compression And Expansion ◽  
Temperature Levels

Stirling engines operate on closed regenerative thermodynamic cycles with compression and expansion of the working fluids at different temperature levels. They may be used as prime movers, refrigerating machines, heat pumps, or pressure generators. Conventional machines use a gaseous working fluid, but substantial improvement in specific output may be gained with a partially reactive, condensing working fluid. The working fluid then consists of an inert gaseous carrier with a chemically reactive, condensing working fluid such as nitrogen tetroxide (N2O4). This may be liquid in the cold compression space and then evaporates and dissociates in the regenerative process to be in the elemental gaseous phase in the hot expansion space. The change of state of one component reduces the required compression work and has the effect of increasing the engine volume compression ratio with consequent benefit to the specific output. The results obtained using idealized theory show that an improvement may be gained in net cycle work of twice the output with a simple gaseous working fluid with no penalties in size, weight, or cost of the engine. The degree of improvement depends on the design and operating conditions of the engine. The effects of variation of some of these parameters are explored.

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