Jean-Félix Durastanti

Study of Photovoltaic Energy Storage by Supercapacitors through Both Experimental and Modelling Approaches

The storage of photovoltaic energy by supercapacitors is studied by using two approaches. An overview on the integration of supercapacitors in solar energy conversion systems is previously provided. First, a realized experimental setup of charge/discharge of supercapacitors fed by a photovoltaic array has been operated with fine data acquisition. The second approach consists in simulating photovoltaic energy storage by supercapacitors with a faithful and accessible model composed of solar irradiance evaluation, equivalent electrical circuit for photovoltaic conversion, and a multibranch circuit for supercapacitor. Both the experimental and calculated results are confronted, and an error of 1% on the stored energy is found with a correction largely within % of the transmission line capacitance according to temperature.

A Circuit-Based Approach to Simulate the Characteristics of a Silicon Photovoltaic Module With Aging

The aging of photovoltaic modules results inevitably in a decrease of their efficiency all through their lifetime utilization. An approach to simulate the evolution of electrical characteristics of a photovoltaic module with aging is presented. The photovoltaic module is modeled by an equivalent electrical circuit whose components have time-dependent characteristics determined under accelerated tests. By entering sun irradiance and temperature, I–V and P–V curves as well as efficiency evolution can be simulated over years assuming equivalent time. The methodology is applied for the case of a monocrystalline photovoltaic module modeled by a one-diode circuit and aging laws are determined with experimental results of damp heat (DH) tests 85 °C/85% RH performed by Hulkoff (2009, “Usage of Highly Accelerated Stress Test (HAST) in Solar Module Aging Procedures,” M.S. thesis, Chalmers University of Technology, Goteborg, Sweden). A power degradation rate of 0.53%/yr is found. A parametric study shows that the rundown of optical transmittance of the upper layers with aging has the most important impact by reducing the initial efficiency by 11.5% over a 25-year exposure contrary to electrical degradations which cause a decrease of 1.85% of the initial efficiency.

Thermal study of an aluminium nitride ceramic heater for spray CVD on glass substrates by quantitative thermography

A thermographic approach is used to determine the temperature of an aluminium nitride hot plate as a glass substrate heater for depositing thin films by spray Chemical Vapour Deposition. In this context, the temperature of the hot plate is conditioned by the evaluation of both effective emissivity and environment temperature with a calibration curve of the commercial camera. We first examined the consistency of the thermosignal/temperature correspondence by employing the software calibration. The environment temperature is evaluated by means of a ruffled aluminium foil according to ASTM. The effective emissivity is measured in situ by using a commercial IR camera in the temperature range 40–540 °C with a better than 3% accuracy. Absolute value of effective emissivity is in agreement with spectrometric values up to 120 °C. Above this temperature, a strong dependence with temperature is highlighted. The radiometric temperature values are, thereby, corrected with an exactitude of temperature better than 2.5% in Celsius degree for the highest temperatures considered.

Investigation of damp heat effects on glass properties for photovoltaic applications

ABSTRACT Damp heat test was performed on soda-lime glass to characterise functional properties of glass in photovoltaic applications and define the ageing mechanism. In addition to the optical property measurements, SEM-EDX, XPS and FTIR analyses were carried out. The damp heat exposed samples presented an increased transmittance in UV, visible and near-IR ranges namely within (1900–2100 nm). The results were explained by hydration of glass network with heat. An ageing mechanism based on glass corrosion theories is discussed. Molecular water adsorption involves a leaching process of network modifier cations and especially sodium ions. Hydrolysis also occurs in silica network by reacting free molecular water. This phenomenon enhances concentration of hydroxyl groups in glass highlighted by FTIR measurements and promotes formation of silanol groups. A tin side dependence on sodium leaching which acts as a passivating barrier for ionic transport is highlighted which may be taken into consideration for photovoltaic module design.

Influence of the Window Thermal Diffusivity on the Silicon Wafer Temperature in a Rapid Thermal System

The heating of a silicon wafer in a rapid thermal process is studied by numerical simulation. In the model, the equations of conservation of mass and energy are solved with the finite-volume method and the determination of the solutions of the radiative transfer equation is based on the Monte-Carlo method. The results of numerical simulations, without optimization and in steady state, show a close relationship between the thermal profiles of the silicon wafer and the ones of the quartz window. By introducing a high thermal diffusivity value for the window, the homogeneity of the wafer temperature is improved by 54%. The effect of heat storage by the quartz window on the temperature profile of the silicon substrate is hence well appreciated. Finally, a selection of materials is proposed for the implementation of the high diffusivity infrared window.

Evolution of the Efficiency of a Photovoltaic/Supercapcitor System with Aging

The evolution of the optimization of photovoltaic/supercapacitor system according to its age is inquired. The system is modeled by an accurate equivalent circuit. The durations and energies of charge/discharge cycles are calculated for a 10 year use. The temporal and energy efficiencies are then deduced according to time, and optimal values are hence extracted. Results show that the optimal efficiencies can be kept constant over time at a value around 90% for the energy. However, the amount of energy stored and released by the supercapacitors is reduced over the years and the response time becomes shorter. So, the behavior of the system is modified with aging regarding its initial nominal functioning. This has to be considered to know the real profitability of the system.

Thermodynamic evaluation for a small scale compressed air energy storage system by integrating renewable energy sources

The present work aims to store renewable energy from wind and sun in the form of compressed air. Several scenarios to find the best operating conditions for a small scale compressed air energy storage system has been analyzed in this paper. The results show a primary efficiency of 52% to 68% for a configuration in which the heat extracted from the air during compression is returned to it during expansion. While for a configuration in which the heat is used for other purposes the theoretical primary efficiency has been found between 37% and 51%, but in this configuration the system its able to provide an important amount of hot and cold. According to consumer needs the current system can be configured to deliver hot, cold and electricity or only electricity.

A self - method for solving the problem of LWIR spectral band of camera for quantitative thermography

In a previous work, we succeeded in connecting normal LWIR apparent emissivity to the spectral one of an aluminium nitride ceramic plate. We showed a good agreement with the assumption of spectral bandwidth of the used IR system. Our aim in this paper is to justify the considered spectral band [7.5μm, 12μm]. Hence we have developed an analyzer of IR system. The analyzer proceeds by comparing thermosignals with integrated blackbody radiance and adapts spectral bandwidth in order to minimize the dispersion from linearity of the characteristic thermosignals / integrated radiance over a temperature range of the IR system. The capacities of the analyzer are tested for 6 commercial cameras. Each of these systems exhibits a similar formatting process implemented during the thermogram recording. The effective spectral bandwidth exhibits plausible values. It varies significantly from one model to the other and the residual non-linearity is connected to the NETD of the IR system. Applied to the same system which served to characterize the apparent emissivity, the analyzer permits to quantify the effective spectral band. We obtain an excellent agreement between the classical model of apparent emissivity and measurement, both in terms of accuracy and in terms of temperature dependence. The absolute error is 0.005 for emissivity and the temperature coefficient is less than 6 10 °C within the temperature range [40°C, 130°C].

Study of Fluid Flow Passing Through the Vicinity of the Critical Point

The fluid flow passing through the vicinity of the critical point in a micrometric capillary is studied in the steady state. A phenomenological analysis of the Navier–Stokes and the heat transfer equations is undertaken. The flow distribution is described by distinguishing three areas within the capillary. In the first upstream region, the mass flow rate is approximated and singularities are put into light when the fluid gets closer to the critical point. The second region is critical and corresponds to a free boundary layer where a thermomechanical coupling occurs due to fluid expansion. Convective heat transfer in this area is significant and is linked to the conductive heat of the first upstream area. In the third downstream area, the flow is connected to the free boundary layer by asymptotical matching, which enables finding the mass flow rate correction. Finally, a relationship is established between the mass flow rate and the critical point position. It is shown that the presence of the free boundar...

Numerical Tool for Extraction of Modal Parameters Based on Continuous Wavelet Transform

Any mechanical system possesses its own vibrating characteristics from which functioning can be understood and foreseen. Modal parameters such as natural frequencies and damping ratios are the main examples. This paper presents homemade numerical analyzer for characterizing them. The procedure is based on complex Morlet wavelet transform with particular use of translated version for better detection of closed modes. The code has been successfully tested through simulated signals. Experimental validation was carried out through the modal analysis of a gear motor on which repeatable and reliable results were obtained.