A method for the optimization of a grid-connected wind turbine system is presented. The behaviour of the system components is coupled in a non-linear way, and optimization must take into account technical and economical aspects of the complete system design. The annual electrical energy cost is estimated using a cost model for the wind turbine rotor, nacelle and tower and an energy output model based on the performance envelopes of the power coefficient of the rotor, C P , on the Weibull parameters k and c and on the power law coefficient ˛of the wind profile. In this study the site is defined with these three parameters and the extreme wind speed V max . The model parameters vary within a range of possible values. Other elements of the project (foundation, grid connection, financing cost, etc.) are taken into account through coefficients. The optimal values of the parameters are determined using genetic algorithms, which appear to be efficient for such a problem. These optimal values were found to be very different for a Mediterranean site and a northern European site using our numerical model. Optimal wind turbines at the Mediterranean sites considered in this article have an excellent profitability compared with reference northern European wind turbines. Most of the existing wind turbines appear to be well designed for northern European sites but not for Mediterranean sites.

In the modelling of heat, mass and momentum transfer phenomena which occur in a capillary porous medium during drying, the liquid and gas flows are usually described by the generalised Darcy laws. Nevertheless, the question of how to determine experimentally the relative permeability relations remains unanswered for most materials that consist of water and humid air, and as a result, arbitrary functions are used in the drying codes. In this paper, the emphasis is on deducing from both numerical and experimental studies a method for estimating pertinent relations for these key parameters. In the first part, the sensitivity of liquid velocity and, consequently, of drying kinetics in the variation of the relative permeabilities is investigated numerically by testing various forms. It is concluded that in order to predict a realistic liquid velocity behaviour, relative permeabiIities can be linked to a measurable quantity: the capillary pressure. An estimation technique, based on simulations coupled with experimental measurements of capillary pressure, together with moisture content kinetics obtained for low or middle temperature convective drying, is deduced. In the second part, the proposed methodology is applied to pine wood. It is shown that the obtained relations provide closer representation of physical reality than those commonly used. Nomenclature AV (AV)j aw By C Cp D D.C.Fm g ha hb hb averaging volume j phase volume within the averaging volume AV water activity resistance factor in the effective diffusitivity coefficient of vapour in the medium mass fraction of the vapour in the gaseous phase constant pressure heat capacity [J kg -1 K-1] diffusivity [m 2 s -1] convective drying condition assumed to remain constant during the overall process total moisture mass flux [kg m -2 s -1] gravity vector [m s -2] intrinsic averaged enthalpy of dry air [J kg-X]: h~ = Cp~(T -T~) specific averaged enthalpy of bound water [J kg-1]: hb = ht -Hb intrinsic averaged enthalpy of bound water [J kg-l]:hb = hz -p-~ jo Hbd(pb) 304 F. COUTURE ET AL. hi h~ h~ Hb H o I.C. J k K k~ L n P q Q RH T Tinfh T~ t S U v W z intrinsic averaged enthalpy of free water [J kg-l]: hz = CpL(7" --Tr) intrinsic averagedenthalpy of solid [J kg-1]: h~ = Cp~IT -T~) intrinsic averaged enthalpy of vapour [J kg-1]: h~ = Hv 4-Cp, (T -T~) heat of desorption [J kg -~] latent heat of vaporisation at the reference temperature T~ [J kg -1 ] Initial conditions of the medium flux intrinsic permeability [m 2] volumetric mass rate of evaporation [kg m -3 s -1] relative permeability thickness of the medium [m] exterior normal unit vector pressure [Pa] source term total heat flux [W m -2] external relative humidity [%] temperature [K or ~ C] wet bulb temperature [K or ~ reference temperature [K]: Tr = 273.16 K time [s] saturation conserved quantity velocity [ms -11 moisture content (in dry basis) space variable [m] Greek Symbols 6z space step [m] e porosity ej volume fraction for the phase j: ej = (AV)s/AV heat source [W m -3] ), effective thermal conductivity [W m -...

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Sorption isotherms of banana, mango, and pineapple have been experimentally found at 40, 50, and 60 C by use of the salt method for a range of water activities from 0.056 to 0.85. The sorption capacity of these fruits increases with the temperature for a given water activity. The experimental curves have been simulated by the GAB and BET models. The BET model ensures a better representation of the experimental results for water activity lower than 0.35 with maximum deviation of 1.0, 1.5, and 2.0 kgwÁkgdm À1 for respectively banana, mango and pineapple. On the contrary, the GAB model enables the representation of the whole desorption isotherms and the estimation of the water content corresponding to monolayer saturation and of the isosteric heat of sorption. It also takes into account the temperature effect. The isosteric sorption heat of the three studied products are deduced from experimental results and empirical correlations are proposed leading to a satisfactorily representation.