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Two studies conducted in Guadeloupe (West Indies) and Réunion (Indian Ocean) islands were designed to investigate the benefits of producing sugarcane as an energy crop and to assess the influence of agroclimatic factors on energy efficiency, respectively. In this context, it is essential to know the low heating value of the dry above-ground biomass (LHVd, MJ/kg) and its energy yield (EY, MJ/m2) in order to select the best varieties and set up a payment method for growers. Eighteen Poaceae (sugarcane and Erianthus) cultivars were compared under wet tropical environmental conditions in Guadeloupe. Three sugarcane cultivars were studied in four contrasting environments in Réunion. The partition sampling and biomass measurement procedures were identical at both locations. Low heating value (LHV) predictions were achieved using near-infrared reflectance spectroscopy (NIRS) after specific calibration (Guadeloupe), or arithmetically after lignocellulosic compound prediction (Réunion). In both studies, LHV variability was very low and slightly dependent on the site, cultivar and above-ground biomass components (millable stalks and tops, and green and dead leaves). Considering the overall dry above-ground biomass (DAB, kg/m2), the LHVd was calculated by averaging 159 samples (mean 16.65 MJ/kg) in Guadeloupe and 315 samples (mean 16.45 MJ/kg) for Réunion. An excellent linear relationship between the DAB and its EY, regardless of cultivar, age and environment, was found (n = 474 and R² = 0.99). Sugarcane energy content assessment could thus be simplified by measuring the DAB, while enabling development of a faster method of payment for growers based on the DAB measurement and the correlation between DAB and EY. Finally, the findings of this study should allow growers to rapidly determine the commercial value of their sugarcane crops, and also enable purchasers to assess the amount of recoverable energy. (Résumé d'auteur)

It is well known that the efficiency of PV modules decreases with increasing module temperatures. Many studies have paid attention to the development and validation of heuristic models to calculate the PV module temperature in higher latitudes, however only a few focus on the thermal behaviour of PV modules in tropical regions of the world, where constantly high temperatures prevail. Also, little is known about the effect of including wind speed in these thermal models. This study evaluates three of such models - one that excludes wind, and two others including the wind influence - using hourly data for two tropical locations. Results show that the average hourly wind speeds in Singapore and Jayapura (Indonesia) are low and therefore the influence of the wind on the PV module temperature is minor. The three evaluated models produce about the same results with RMSE between 1.5-3.8 °C during daytime, which corresponds to a deviation in power output in the range of 0.3-1.6 %, depending on the PV module technology.

This paper introduces an adaptive current control strategy for DC-DC boost converters without input-output voltage sensing. In addition, accurate current control is achieved in the presence of dynamical uncertainties. Unlike many controllers available for DC-DC converters, the adaptive controller's stability is guaranteed by Lyapunov stability theory. A comparison to PI counterpart has been carried out. Results show higher performance, which lead to more efficient operations of DC-DC converters.

A new two-stage gasifier with fixed-bed has recently been installed on CIRAD facilities in Montpellier. The pyrolysis and the gasifier units are removable. In order to characterise the pyrolysis products before their gasification, experiments were carried out, for the first time onlywith the pyrolysis unit and this paper deals with the results obtained. The biomass used is Pinus pinaster. The parameters investigated are: temperature, residence time and biomass flow rate. It has been found that increasing temperature and residence time improve the cracking of tars, gas production and char quality (fixed carbon rate more than 90%, volatile matter rate less than 4%). The increase of biomass flow rate leads to a bad char quality. The efficiency of tar cracking, the quality and the heating value of the charcoal and the gases, indicate that: temperature between 650 °C and 750 °C, residence time of 30 min, biomass flow rate between 10 and 15 kg/h should be the most convenient experimental conditions to get better results from the experimental device and from the biomass pyrolysis process. The kinetic study of charcoal generation shows that the pyrolysis process, in experimental conditions, is a first-order reaction. The kinetic parameters calculated are comparable with those found by other researchers. (Resume d'auteur)

The cleaning of syngas is one of the most important challenges in the development of technologies based on gasification of biomass. Tar is an undesired byproduct because, once condensed, it can cause fouling and plugging and damage the downstream equipment. Thermochemical methods for tar destruction, which include catalytic cracking and thermal cracking, are intrinsically attractive because they are energetically efficient and no movable parts are required nor byproducts are produced. The main difficulty with these methods is the tendency for tar to polymerize at high temperatures. An alternative to tar removal is the complete combustion of the syngas in a porous burner directly as it leaves the particle capture system. In this context, the main aim of this study is to evaluate the destruction of the tar present in the syngas from biomass gasification by combustion in porous media. A gas mixture was used to emulate the syngas, which included toluene as a tar surrogate. Initially, CHEMKIN was used to asses...

The complexity of reality can be better represented by models able to involve uncertainty and time patterns. We present a general formulation of a stochastic dynamic multiobjective optimization model and we provide different solution concepts based on its transformation into different deterministic equivalent models. We provide two applications to sustainable decision making in portfolio management and optimal workforce allocation.

Abstract This study considers effects of pressure of up to 110 kbar on line position and fluorescence lifetime τ for 4 T 1 → 6 A 1 transition in LMA:Mn 2+ and LMA:Mn 2+ , Nd 3+ . Energy transfer between Mn 2+ and Nd 3+ in LMA:Mn 2+ , Nd 3+ has also been considered. Results indicate pressure induced line shift towards longer wavelengths, a red-shift in both crystals with the same rate of 0.182 nm kbar −1 . Pressure influences fluorescence lifetime τ in the considered crystals differently; whereas for LMA:Mn 2+ increasing pressure causes slow linear decrease of τ , and for LMA:Mn 2+ , Nd 3+ τ increases linearly as pressure raises. Energy transfer efficiencies decrease with pressure. High pressure induced red-shift can be explained by a simple model.

Abstract Performance of wood gasification genset is sensitive to the moisture content in the feedstock and the electrical load (demand of users). This study investigates the influence of these process parameters on the electrical efficiency of the genset (ηglobal), the electrical engine efficiency (ηengine), the cold gas efficiency (CGE), and the syngas composition. Experimental tests were carried out by varying the moisture content from 11% to 23% and the electrical power from 4.7 kW to 12.8 kW on a commercial gasifier equipped with precise measuring tools. The increase of the performance when the electrical load is increased or when the moisture content in the wood chips is decreased is both quantified and discussed. Such behaviour was mainly explained by differences in engine filling rates and reactor temperatures.