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A photovoltaic-thermoelectric (PV-TE) system is modeled theoretically and demonstrated experimentally. Mathematical formulations of the system are proposed according to energy conservation and finite-time thermodynamics, which can be applicable to analyze and optimize the system that consists of commercial photovoltaic (PV) cells and thermoelectric generators (TEGs). The genetic algorithm is introduced to maximize the system's power by optimizing multiple parameters. In Yan'an City, which is located in the northern Shaanxi Province in northwest China, the actual solar irradiance is recorded for almost a full year and the proposed model is verified. Theoretical and experimental results are analyzed and compared. It is found that there are several independent structure parameters in the PV-TE systems and they should be optimized simultaneously to maximize the performance. The PV-TE system's maximum theoretical average power of 0.343 W is 2.69 % greater than the solo PV cell's maximum theoretical power of 0.334 W. The measured average power of the system of 0.317 W is 0.32 % more than that of a solo PV cell of 0.316 W. The duration of strong lighting in Yan'an City reaches 8 h every day for nearly one year and the irradiation intensity can approach 1000 W/m2. The solar radiance is weakly affected by the seasonal changes of four seasons but is greatly affected by rainy days and cloud thickness. The research findings can serve as a helpful guide for the specific implementation of the PV-TE system and exploitation of solar energy resources in northwest China. • The novel model of a tandem commercial PV-TE system is established. • The genetic algorithm optimizes parameters to maximize the power of the system. • The maximum power of the system is 2.69 % higher than that of a solo PV cell. • The experiment power of the system is 0.32 % higher than that of a solo PV cell. [ABSTRACT FROM AUTHOR]

Empirical modeling of heat pipe heat exchangers (HPHX) is the most economical and appropriate method for predicting its performance and estimating long-term economic benefits in the industrial field. Unfortunately, no models can predict the performance of HPHX with baffles that show complex flow characteristics, such as a combined flow arrangement of parallel flow and counterflow. This study presents the empirical model for HPHX with baffles, which predicts thermal performance and pressure drop based on empirical correlations and theoretical relations. It fabricated the HPHX with baffles composed of 95 copper two-phase closed thermosyphons (TPCTs) and measured its effectiveness, heat transfer rate, and pressure drop. We validated the presented model based on our experimental results and literature data. The validation results confirm that it can predict the HPHX performance with high accuracy, not only for the presence of baffles but also for various HPHX geometries (heat exchanger dimensions, number of baffles, etc.) and operating conditions (temperature and flow rate of hot and cold fluids). Finally, we analyzed and discussed the composition of HPHX performance, and as a result, enhancing forced convection between the working fluid and the TPCT bundle is a vital key to improving thermal performance, especially for HPHX that utilize gas (or air) as the working fluid. It was also found that the wall material had a negligible impact on thermal performance, so it was reasonable to consider stainless steel, which is more resistant to corrosion and erosion than copper. Our results are expected to be a great reference for engineers designing and manufacturing HPHX in the industrial field. • The empirical model for heat pipe heat exchanger (HPHX) with baffles is presented. • The proposed model is validated based on our experimental results and literature data. • The influence of each component on HPHX performance is analyzed by a validated model. [ABSTRACT FROM AUTHOR]

Residential buildings account for 84 % of Italy's built environment, playing a pivotal role in the EU's aim to cut GHG emissions by 55 % through enhanced energy efficiency and climate adaptation. This necessitates comprehensive energy retrofit initiatives, especially in sectors like social housing, which has been relatively overlooked in terms of energy efficiency strategies. This study focuses on a multi-story building from the 1980s in Rome, implementing an innovative energy system proposed by the RESHeat European project. This system, aimed at standardizing energy retrofits for late 20th-century social housing, leverages the underexplored potential of water-source heat pump (WSHP) systems. The novelty of this research extends to its examination of multi-family housing, a sector that has seen less attention compared to public spaces and smaller residential buildings. Through experimental validation and annual dynamic simulations using TRNSYS and Simulink, the research compares the existing heating system with a proposed upgrade that includes a WSHP and Photovoltaic-Thermal (PVT) panels. This upgrade demonstrated a significant efficiency improvement, achieving an annual COP of 6.1 for the WSHP and a 36 % Primary Energy Savings (PES) from the PVT panels, showcasing the effectiveness of these technologies in enhancing the energy profile of multi-family residential buildings. [Display omitted] • A multi-energy system for a 1980s social housing in mild climate is presented. • A dynamic model based on a water-source HP and cooled PV panels was set. • Experimental validation of building and plant components were conducted. • Combining heat pump and PVT panels a seasonal COP of 5.4 can be achieved in heating. • Solar fraction of 0.98 ensured by PVT contributes to a Primary Energy Saving of 36 %. [ABSTRACT FROM AUTHOR]

n -Dodecane combustion was investigated experimentally and numerically in present study. Pyrolysis experiments of n -dodecane at pressures of 0.0066, 0.039, 0.197 and 1 atm, temperatures from 750 to 1430 K were studied in a flow reactor. Mole fractions of n -dodecane, argon and pyrolysis products (including active radicals) were evaluated. A kinetic model of n -dodecane was developed by validating both present and literature reported experiments. The rate of production analysis reveals H-abstraction and C C bond fission reactions are main consumption pathways of n -dodecane. The β -C C scission reactions of alkyls contribute to the formation of alkenes, which are mainly consumed via the allylic C C fission reactions. As a soot precursor, benzene is largely produced from the recombination of C 3 species. Moreover, effects of carbon chain length on flow reactor pyrolysis were investigated for n -decane, n -dodecane and n -tetradecane. The decay of n -tetradecane is the fastest, followed by n -dodecane and n -decane, indicating that the pyrolysis reactivity of n -alkanes increases as the carbon chain length increases from C 10 to C 14 n -alkanes. Ignition delay times and laminar burning velocities (LBVs) of n -alkanes under similar conditions were also compared, the result shows that effects of the carbon chain length on ignition delay times and LBVs are slight. [ABSTRACT FROM AUTHOR]

We present herein the development, experimental validation, and application of a volume element model for 3D dynamic building thermal simulation. The 3D spatial domain in the VEM is discretized with lumped hexahedral elements using ray crossings and ray/triangle intersection techniques that yield sufficiently accurate geometric representation of a building. Subsequently, energy balance is applied to each element in the mesh, and the resulting system of ordinary differential equations is integrated in time to obtain spatiotemporal indoor temperature and relative humidity fields. In this work, we adjusted the model by comparing the simulated indoor air temperatures to the experimental measurements as we calibrated model parameters with high uncertainty. The adjusted model was validated using different experimental data sets, and the numerical results were in a good agreement with the measurements. We employed the validated model to conduct a case study in which the sensible heat gain and loss as well as the time lag were evaluated as functions of different envelope thermal masses. Results showed the trivial effect of floor thermal mass on heat gain, and the changes in sensible heat gain and envelope thermal mass were not linearly proportional, alluding the existence of an optimal envelope design. [ABSTRACT FROM AUTHOR]

Considering the need for a reliable and environmentally friendly energy storage solution for addressing renewable energy intermittency issue and following the developments on Isothermal Compressed Air Energy Storage (I-CAES) systems, a new finned piston compressor which is characterized by increased heat transfer area and coefficient has been designed, analyzed, manufactured and experimentally tested. This compressor includes two sets of concentric annular fins with different diameters: the mobile fins are pushed into the space between the stationary fins through a driver shaft and compress the air trapped in the interconnecting annular chambers while keeping the air temperature close to ambient. Modeling of heat transfer and fluid flow in such a complicated geometry with a transient, non-linear, multi-layer, multi-dimensional nature can be best done by equivalent electric analogies with variable resistances and capacitors and employing a lumped method. Using bond graph representation method and based on a previously developed model for a classic reciprocating compressor, energy conversion has been modeled using a conjugate heat transfer and fluid flow model. Results of the simulation are presented and have been validated using an experimental test bench and to provide contrast to current technology, compared to a classic reciprocating compressor. The heat transfer along one cycle has increased in the finned compressor by 32 times compared to a classic piston compressor. The results also reveal that however the volumetric efficiency is decreased slightly in the finned compressor (−8%), the exergetic efficiency has increased from 55.1% in a classic piston to 78.4% in the finned piston. [ABSTRACT FROM AUTHOR]

Phase change materials (PCM) are used in many industrial and residential applications for their advantageous characteristic of high capacity of latent thermal storage by means of an isothermal process. In this context, it is very useful to have predictive mathematical models for the analysis of the thermal performance and for the thermal design of these layers. In this work, an experimental validation of an analytical model that resolves the steady periodic heat transfer problem in a finite layer of PCM is presented. The experimental investigation was conducted employing a PCM with thermophysical and thermochemical behavior very close to those hypothesized in the formulation of the analytical model. For the evaluation of the thermophysical properties of the PCM sample used, an experimental procedure created by the authors was employed. In all tests realized in a sinusoidal and non-sinusoidal periodic regime, the comparison between the measured and calculated trends of the temperature at different sample heights and of the surface heat fluxes show an excellent agreement. Moreover, also having verified the analytical total stored energy, the analytical model constitutes a valid instrument for the evaluation of the latent and sensible contribution and the trend in time of the position of the bi-phase interface. [ABSTRACT FROM AUTHOR]

District heating networks (DHN) are generally considered as a convenient, economic and environmental-friendly way to supply heat to a large amount of buildings. Some modelling methods are required to consider the dynamic behaviour of district heating networks to design them correctly, spare the investment costs and limit the heat losses related to the use of a too high operating temperatures. For the same reasons, the DHN control or retrofit of installations also requires the assessment of the DHN dynamic behaviour. To achieve this, the heat transport in DHN, which is one of the key issues in the behaviour of a whole centralized heating system, has to be correctly modelled. Previous work evidenced current limitations of one dimensional finite volume method to model heat transport in pipes and proposed an alternative method considering the thermal losses and the inertia of the pipes. The present contribution intends to experimentally validate this model on a test rig available at the Thermodynamics laboratory of the University of Liege (ULg, Belgium) and on an existing district heating network. For both experimental facilities, the current model shows good agreement between the experimental data and the simulation results for a large range of water velocities. Moreover, it is shown that the thermal inertia of the pipe has a significant influence on the outlet pipe temperature profile. [ABSTRACT FROM AUTHOR]

Clamping mechanisms have significant effect on the performance of polymer electrolyte membrane (PEM) fuel cells. In this paper, PEM fuel cell with new clamping mechanism is designed to study the contact pressure distribution over the active area of PEM fuel cell's membrane electrode assembly (MEA). The clamping pressure is pneumatically exerted on the PEM fuel cell assembly. A comparison between the conventional and new clamping mechanism is carried out with simulation, and the numerical results are validated against experimental investigation performed in the fuel cell technology research laboratory. The experimental results are gathered using embedded pressure measurement films in the designed single cell. The results achieved via finite element method are in good agreement with experimental results. It is concluded that the contact pressure distribution of MEA for the new clamping mechanism is more uniform than the conventional one. [ABSTRACT FROM AUTHOR]

A system model that can accurately simulate the instantaneous solar transmittance through multilayer glazing façade (MGF) and shading device can provide a solid foundation for the thermal and daylighting performance calculation of MGF as well as indoor visual comfort evaluation. Traditional optical models for venetian blind and glazing façade meet with their limitations to analyze new prototype of shading blind like photovoltaic (PV) blind which has quite different surface optical properties compared with conventional venetian blind. The present study proposed a new system model for MGF using shading blind with arbitrary geometrical and optical features which is suitable for a wide range of applications. Three major calculation types for modeling of shading blinds cover all the possible situations in application. Guess Integer-Valued Function is adopted for delivering a general description on direct radiation transport. The direct-direct, direct-diffuse and diffuse-diffuse radiation transports are separately considered. A series of experiments were carried out to validate the model under various parameter settings and different weather conditions. Parametric study revealed some new findings in the evaluations of influence of ambient radiation situations, geometrical and optical features of blind space on both solar transmittance and solar absorption by blind layer. [ABSTRACT FROM AUTHOR]

In this paper, nonlinear grey-box model and model predictive control (MPC) of a cascade-type polymer electrolyte membrane (PEM) fuel cell stack are presented. The aim of this study is to track the desired voltage trajectory of the dead-end cascade-type PEM fuel cell stack. The stack is integrated with humidifiers and water separators, and both anode side and cathode side of the stack operate in a dead-end mode. The framework of this paper is threefold: i) nonlinear grey-box modeling of the cascade-type PEM fuel cell stack with integrated humidifiers and water separators and validation of the obtained model, ii) linearizing and proposing model order reduction (MOR) by using singular perturbation method, and iii) designing model predictive controller to attain output tracking. Performance of the controller is validated off-line through experimental tests carried out on 400 W cascade-type PEM fuel cell stack consisting of 4 cells. Results show that the proposed controller tracks the desired trajectories with a high accuracy. [ABSTRACT FROM AUTHOR]

Inspired by traditional Chinese architecture, a curved PV roof integrated with copper indium gallium selenide (CIGS) cells is designed, which not only manifests Chinese aesthetic elements but also could generate electricity. Considering solar radiation distribution on curved PV cells different from that on traditional flat cells, this paper builds a radiation distribution model to calculate the radiation on the curved surface and an electrical model based on 5-parameter model to predict the power output of PV cells with different connections (independent output; in parallel; in series). An experimental rig was built, and the theoretical model was validated. Results showed that the CIGS cells on the west side of the curved surface performed better in electricity generation than the CIGS cells on the east side did; the CIGS cells in parallel generated more power than the cells in series did. The annual performance prediction shows that CIGS cells on the west side generate 155.18 kWh, which is 21.49% more than on the east side; CIGS cells in parallel generate 275.96 kWh, which is 12.56% more than the cells in series; The electrical generation of the curved PV roof is 7.41% less than the flat roof does. Parametric analysis is also conducted. • Simulation model of the electrical performance of a curved PV roof is built. • Different connection methods of the curved PV cells are discussed. • Impacts of some parameters on the electrical performance are analyzed. • Annual electrical performance analyses are investigated in Hefei. • Flat and curved PV roofs are compared numerically. [ABSTRACT FROM AUTHOR]

The objective of this work is to develop a thermodynamic model considering non-stoichiometric restrictions. The model validation was done from experimental works using a bench-scale fluidized bed gasifier with wood chips, dairy manure, and sorghum. The model was used for a further parametric study to predict the performance of a pilot-scale fluidized biomass gasifier. The Gibbs free energy minimization was applied to the modified equilibrium model considering a heat loss to the surroundings, carbon efficiency, and two non-equilibrium factors based on empirical correlations of ER and gasification temperature. The model was in a good agreement with RMS <4 for the produced gas. The parametric study ranges were 0.01 < ER < 0.99 and 500 °C < T < 900 °C to predict syngas concentrations and its LHV (lower heating value) for the optimization. Higher aromatics in tar were contained in WC gasification compared to manure gasification. A wood gasification tar simulation was produced to predict the amount of tars at specific conditions. The operating conditions for the highest quality syngas were reconciled experimentally with three biomass wastes using a fluidized bed gasifier. The thermodynamic model was used to predict the gasification performance at conditions beyond the actual operation. [ABSTRACT FROM AUTHOR]

In this paper, we are interested on the study of the incidence angle effect on the aerodynamic structure of an incurved Savonius wind rotor. The numerical model is based on the resolution of the Navier-Stokes equations in conjunction with the standard k-ε turbulence model. These equations were solved by a finite volume discretization method. The software “Solidworks Flow simulation” has been used to characterise the flow characteristics in different transverse and longitudinal planes. To confirm the computer method validity, an experimental validation has been done using a wind tunnel equipped by the incurved Savonius wind rotor. [ABSTRACT FROM AUTHOR]

In this paper, model order reduction (MOR) of cascade-type polymer electrolyte membrane (PEM) fuel cell stack with integrated humidifiers and water separators is investigated. The purpose of this work is to attain orders of magnitude improvement in numerical simulation speed. Both the anode and the cathode of stack operate in a dead-end mode. The reduced-order model (ROM) is developed for continuous and discrete form of the cascade-type PEM fuel cell models. The obtained ROM is verified with the full nonlinear model, which full-order model itself is validated using experimental data from cascade-type 4-cells PEM fuel cell stack. Responses of different orders of ROMs are compared to those of full-order model to determine the minimum order of the model that approximates the behavior of the original model properly. The results predicted by the developed reduced-order model nearly follow the full nonlinear model and experimental results. According to the low computational cost of ROM, the derived model can be further used for real-time control and diagnostic applications. [ABSTRACT FROM AUTHOR]

To improve the performances of photovoltaic panels, water-based cooling systems have been considered as an interesting solution. This study proposes a novel mono-dimensional thermal model that includes the spray cooling phenomena on the back surface. The model is based on the energy balance method with a Finite Difference approach providing the thermal field across the thickness, and was validated with data of an experimental setup with a PV panel equipped with two spray nozzles. Simulations were carried out over a large number of days in the summer period with a short time step (5 s). Results showed an average RMSE of 1.37 °C, RMSEP of 0.005% and NSE of 96.5% for the back surface temperature, and an average RMSE of 3.39 W, RMSEP of 0.36% and NSE of 99.6% for the electric power. A further assessment of the cooling phenomenon highlighted the contribution of sensible and latent energy exchanges to the panel energy balance. Finally, a comparison of the performances with a non-cooled PV panel showed an average increase of 7.8% of the electric power in solar radiation peak hours and a reduction of 28.2% of the average cell temperature. • A novel thermal model including spray cooling for PV panels was proposed. • The model was validated with experimental data. • An accurate analysis of the cooling phenomena was conducted. • The average efficiency in summer increased by 5.4%. [ABSTRACT FROM AUTHOR]

In this paper, numerical investigations were carried out to study the bucket design effect on the turbulent flow around unconventional Savonius wind rotors. The numerical model is based on the resolution of the Navier–Stokes equations in conjunction with the standard k-ε turbulence model. These equations were solved by a finite volume discretization method. The software “Solidworks Flow simulation” has been used to characterise the flow characteristics in different transverse and longitudinal planes. Experimental results are conducted on an open wind tunnel equipped by an incurved Savonius wind rotor. The good agreement between numerical and experimental results confirms the validity of the numerical method. [ABSTRACT FROM AUTHOR]

A Stirling engine with nominal output power of 1 kW is tested using air and helium as working gases. The influence of working pressure, engine speed and temperature of the hot source is studied, analyzing instantaneous gas pressure as well as instantaneous and stationary temperature at different positions to derive the effective power. A zero dimensional finite-time thermodynamic, three zones model of a generic Stirling engine is developed and successfully validated against experimental gas temperature and pressure in each zone, providing the effective power. This validation underlines the interest of different working gases as well as different geometric configurations for different applications. Furthermore, the validated model allows parametric studies of the engine, with regard to geometry, working gas and engine kinematics. It is used in order to optimize the kinematic of a Stirling engine for different working points and gases. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the modeling and the experimental validation of air and water solar collectors used in humidification–dehumidification (HDH) solar desalination unit. The solar desalination process is currently operating under the climatological conditions of Sfax (34 N, 10 E), Tunisia. To numerically simulate the air and water solar collectors, we have developed dynamic mathematical models of the solar collectors. The resulting distributed parametric systems of equations are transformed into a system of ordinary differential equations (ODEs) using the orthogonal collocation method (OCM). A comparison between numerical and experimental data was conducted. It was found that the two-temperature mathematical model describes more precisely the real behaviour of the water solar collector than the one-temperature mathematical model. It was also shown that the developed mathematical models are able to predict accurately the trends of the thermal characteristic of the water and air solar collectors. As a result, the proposed models can be used to size and test the behaviour of such a type of water and air solar collectors. [Copyright &y& Elsevier]

High pressure ratio partial admission axial impulse turbines are typically employed for underwater vehicles due to small mass flow rate and machining constraints. However, little work has been focused on the generic design methodology for high pressure ratio partial admission axial impulse turbines. The experimental results and empirical correlations are mostly established upon low pressure ratio axial turbines. In this paper, the meanline turbine design method is first documented together with the performance prediction method at off-design points. The numerical loss breakdown method is then described to thoroughly verify empirical correlations. Both the meanline and numerical methods are thoroughly validated against experimental results and the difference among meanline, numerical and experimental results is less than 10%. A case study is then performed and a 13 kW partial admission axial impulse turbine is designed. The suitability of empirical correlations is confirmed by comparing the losses between the meanline and numerical methods, and the difference less than 5% at design and off-design points is attained. This paper provides the insight into the design methodology for high pressure ratio partial admission axial impulse turbines. • A meanline design method is proposed for high pressure ratio partial admission axial impulse turbines. • The turbine off-design performance prediction method is presented. • The experimental investigation of high pressure ratio partial admission axial impulse turbines is conducted. • The meanline method is validated against experimental results. [ABSTRACT FROM AUTHOR]

The safe startup of micro gas turbine (MGT) generator system is the premise of normal operation. The whole start-up process contains motor startup, ignition, speed acceleration, motor switching to generator and power acceleration. Motor switching to generator happens at the self-sustaining state, which is significant to safe start-up process. However, characteristics of MGT generator system at self-sustaining state are hardly to investigate due to the lack of performance maps and complete experiments. Therefore, this work analyzed start-up schedule and presented a theoretical and experimental study on the self-sustaining performance of MGT generator system, based on the self-designed 30 kW MGT generator system built in Jiangjin Turbocharger Plant, China. The self-sustaining speed boundary and fuel consumption area is determined from the aspects of safe startup. A novel principle for determining the self-sustaining point (SSP) is proposed. Results show that the self-sustaining state can be achieved only when speed is over 26,750 rpm, and the SSP is determined at the speed of 30,750 rpm based on the proposed principle. Finally, the self-sustaining TIT and natural gas flow are compared with the experimental data, with two relative errors both almost within 4%. This method is instructive to the MGT generator system startup process. • The startup process of MGT generator system is analyzed based on the operation laws of MGT. • Self-sustaining boundary and fuel consumption area are determined during the startup process. • A novel principle for determining the self-sustaining rotational speed is proposed. • Experimental tests at different environmental temperature and speed are conducted. • Error analysis between the model calculations and experimental data is made. [ABSTRACT FROM AUTHOR]

A multi-functional dual-air-channel solar wall system with phase change material (PCM) is presented. It can generate electricity in the whole year and provide hot water in non-heating season, space heating in heating season. This system improves the shortcoming of traditional solar wall system that cannot work continuously at nighttime. Firstly, several continuous full-day experiments were conducted to investigate the thermal and electrical performance in each working mode. Secondly, mathematical model of the system was established and validated. Thirdly, parameter analyses were introduced to evaluate the performance of this system in different conditions. The main results are: (1) The system achieved good electrical and thermal performance in each working mode, and continuous indoor space heating was enhanced during nighttime in winter and transition season; (2) Through the model validation, the accuracy of established model was acceptable; (3) Proper increase of the PV cells coverage and channel height can improve the comprehensive performance of the system; (4) For a better continuous space heating performance during nighttime, phase change range of PCM is more suitable to be 19–21 °C in the selected experimental winter days and 22–24 °C in the transition season days. • A multi-functional solar wall system with PCM was proposed and investigated. • Several continuous full-day experiments were conducted in each working mode. • Effective functions were achieved by analyzing the experimental results. • Mathematical model was established and validated. • Parametric analyses were conducted and discussed based on the model. [ABSTRACT FROM AUTHOR]

This paper deals with the design of an innovative load controller for heavy-duty gas turbine (GT) power generators and with its practical implementation on real industrial power plants. A robust controller based on the Sliding Mode control technique is designed, in order to improve the performance of the GT system with respect to the traditional Proportional-Integral-Derivative regulation. The main aim of this paper is to fill the gap between theoretical studies and the real deployment of the advanced GT controller based on the Adaptive Sliding Mode control, an improved variant of the traditional Sliding Mode. The main focus of this work is to solve the main limitations of previous works for an effective deployment of the proposed controller on real industrial devices. This work is developed in collaboration with Ansaldo Energia S.p.A., the interaction with the industrial partner is one of the key points of this paper allowing the implementation of the proposed controller on real industrial microprocessors and the validation in a Real Time Simulation environment at the Ansaldo Energia S.p.A. R&D laboratories. The controller validation, performed in a Hardware-In-the-Loop set-up, showed highly satisfactory results and important improvements in comparison with the traditional regulation of the GT power generator. • Adaptive Sliding Mode control for gas turbine power Generators. • Increasing the tradition power plant performance to host RES. • Controller design adaptation for the implementation on a rea industrial controller. • Validation of the proposed controller in a real gas turbine power generator architecture. • Experimental validation on a high-fidelity Real-Time Model in a Hardware in the Loop set-up. [ABSTRACT FROM AUTHOR]

Performance improvement of the thermoelectric cooler depending on both the thermoelectric material development and the system design optimization will be positive and significant for various applications of thermoelectric cooling technology. This paper introduced a typical thermoelectric cooling model and constructed the overall heat transfer and electric-heat conversion model. Based on the dimensional analysis method, we deduced and obtained several necessary non-dimensional coefficients such as dimensionless cooling power, working current, and thermal conductance for analyzing the performance of the thermoelectric cooler. The dimensionless working current and thermal conductance reveal the relationship between the cooling capacity caused by the Peltier effect, the inner heat conduction of the PN material, and the total heat transfer capacity of the cold-side and hot-side. The multi-parameters analysis results show that the cooling power will reach up to the maximum when K d , I d , and ω vary from 0.1 to 0.3, 0.08 to 0.12, 0.3 to 0.45, respectively. For validation, we constructed an experimental system for testing the cooling performance. Experimental results show that the optimal thermal conductance allocation ratio of the cold-side is the same as the simulation results. That is, the overall consideration of dimensionless coefficients is feasible and significant for ameliorating the thermoelectric cooling performance. • Introduced several dimensionless coefficients by dimensional analysis method. • Derived the dimensionless expressions of heat transfer rates and temperatures. • Obtained the optimal heat transfer area allocation, dimensionless working current and thermal conductance. • Validated the feasibility of the proposed method by the proposed experimental system. [ABSTRACT FROM AUTHOR]

Organic Rankine cycle (ORC) is being widely researched in the application of waste heat recovery and renewable energy utilization. The ORC using zeotropic mixtures (MORC) attracts much attention owing to the ability to match better in heat transfer. The system with fluctuant heat source often encounters challenges of safety and efficiency and this issue drives the development of dynamic research. Modeling methods including finite volume (FV) and moving boundary (MB) can well predict the dynamic behavior of system with pure fluids, but the situation with zeotropic mixtures are unclear because of composition shift effect. In this case, this paper establishes the dynamic model of MORC by these two methods separately and compares the simulation with experiment. Results indicate that both methods have similar high accuracy and the composition shift effect in MORC dynamic simulation could be acceptably ignored. The following study on dynamic characteristics shows the response speed of ORC system with R134a/R245fa tends to increase with mass fraction of R134a. The system response speed with the disturbance of fluid mass flowrate is the fastest comparing to exhaust temperature and flowrate. This work contributes to provide abundant reference for dynamic modeling of MORC and lay a foundation for the subsequent control design. ● Dynamic modeling of MORC using finite volume method and moving boundary method separately. ● Introducing a valve model between condenser and receiver to avoid flow reversal. ● Verifying the established two models with experiment and confirming the acceptance of ignoring composition shift in simulation. ● The system response speed of ORC with R134a/R245fa tends to increase with mass fraction of R134a. [ABSTRACT FROM AUTHOR]

Savonius turbine is a popular vertical shaft power generation turbine for its small starting torque and outstanding cost effectiveness. Installing the deflector on the Savonius turbine is a cost-effective way to increase its power performance. In this study, a passive positioning system is proposed, so as to settle the matter that the deflector is unable to be kept in the suitable position autonomically. The system acclimatizes itself to the inflow automatically with the help of the rear deflector that is impinged by the incoming flow. In order to demonstrate power performance of the presented system, the influence of the rear deflector on Savonius turbine is experimentally and numerically investigated through towing tank tests and 2D CFD simulations. The results indicate that: the lower deflector length and farther distance from the center of rotation, the weaker effect on the power coefficient. Considering the engineering requirements of power generation device, the optimal placement of the deflector is achieved. When the distance from the center of rotation is 0.82 times than the turbine's diameter, the suppressing effect on the power coefficient is less than 3 % in this operating condition. • A passive aligning system is proposed to keep deflector in the suitable position. • The influence of the rear deflector is studied experimentally and numerically. • The length and location of the deflector is analyzed in different conditions. • The optimal placement of the deflector is suggested finally. [ABSTRACT FROM AUTHOR]

This paper presents a coupled electrical-thermal model for solar photovoltaic (PV) modules, under an unsteady state and various conditions, including ambient temperature, solar radiation and wind velocity. Validation shows that the electrical and thermal models present high agreement with the experimental data. The developed model after validation is then applied to investigate the distribution of thermal resistance, the influence of environmental conditions and cooling methods. Results show that the radiative and convective thermal resistances play a significant role in PV electrical-thermal performance, while conductive thermal resistance can be neglected for simplification in some cases. The results also demonstrate the effects of weather conditions including solar radiation, ambient temperature and wind velocity on PV performance vary and they need to be selected carefully during parameters design. Moreover, a dynamic estimation of different seasons and a long-term evaluation of an entire year for a specific PV array have been done to assess the performance of the coupled model. The simulated results are in good agreement with the experimental data in spite of the weather conditions, in which the relative errors of daily energy in four different seasons are just 1.06%–6.17%, while the average monthly energy based on the proposed model (1185.4 kWh) only deviates 4.66% from that extracted by PVsyst software (1132.6 kWh), which both verify the accuracy of the proposed model again. • A coupled electrical-thermal model is developed to predict PV temperature and electrical power simultaneously. • Unsteady state conditions are considered in the model to make it more accurate than NOCT and Sandia model. • The radiation and convection thermal resistance play an irreplaceable role in PV electrical-thermal performance. • The relative error between simulated and measured electrical energy in four different seasons is 1.06%–6.17%. [ABSTRACT FROM AUTHOR]