Gilles Notton

Correlations for direct normal and global horizontal irradiation on a French Mediterranean site

Abstract The purpose of this study is to establish some correlations on direct normal and global horizontal irradiation for a mediterranean site. The correlations have been developed for monthly mean values, daily and hourly values of irradiation data. We have used linear or polynomial regressions between energetical ratio and sunshine duration. For the monthly means and the daily values, the ratio I I M fits very well the sunshine duration while, for hourly values, we express I h I o,h as a function of H h H o,h . In all cases, these correlations are, for this mediterranean site, in good accordance with experimental data. Nevertheless, a study for other locations has to be developed.

Forecasting and simulating wind speed in Corsica by using an autoregressive model

Alternative approaches for generating wind speed time series are discussed. The method utilized involves the use of an autoregressive process model. The model has been applied to three Mediterranean sites in Corsica and has been used to generate 3-hourly synthetic time series for these considered sites. The synthetic time series have been examined to determine their ability to preserve the statistical properties of the Corsican wind speed time series. In this context, using the main statistical characteristics of the wind speed (mean, variance, probability distribution, autocorrelation function), the data simulated are compared to experimental ones in order to check whether the wind speed behavior was correctly reproduced over the studied periods. The purpose is to create a data generator in order to construct a reference year for wind systems simulation in Corsica.

PV-hybrid power systems sizing incorporating battery storage: an analysis via simulation calculations

A methodology is developed to determinate the optimal size of PV-hybrid subsystems and to optimize the stand-alone system management. Two particular parameters characterize the back-up engine generator: SDM and SAR, respectively the starting and the stopping thresholds calculated as a part of the nominal storage capacity. Using simulation calculations, the optimal configuration leading to the autonomy constraint, is determined on the basis of a minimization of the kWh cost. The operating back-up generator strategy study has shown that the smallest kWh cost is obtained for a system characterized by a SDM=30% and SAR=70% of the nominal battery capacity.

Autonomous photovoltaic systems: Influences of some parameters on the sizing: Simulation timestep, input and output power profile

In this paper, an optimized sizing method of an autonomous photovoltaic system is applied to a case study located in Corsica. Using a global systemic approach based on solar radiation data and load profile, the photovoltaic system operation behaviour is first simulated. The system autonomy constraint leads to an infinity of system configurations which can be reduced by additional physico-technical constraints. Adding, as a parameter, the kilowatt-hour cost and its minimization constraint, the best system configuration is determined. In this study of the influence of the temporal repartition of the load and of the simulation time step, we determine the important energy surplus produced by the optimized autonomous photovoltaic system.

Modelling and performance of a copolymer solar water heating collector

Abstract The performance of a solar flat-plate thermal collector wholly manufactured in a copolymer material is studied. The influence of different parameters of the system such as the insulation thickness, the flow rate and the fluid layer thickness is analysed. Thermal performance, productivity and efficiency of such a solar system is presented for a Mediterranean site. Yearly mean efficiencies are about 56.5% in no wind and about 49.0% for a wind speed of 5 m s−1. The use of polymer materials reduces the collector weight by 50% in comparison with a traditional metal collector, this renders easier installation.

Computer-aided analysis of the integration of renewable-energy systems in remote areas using a geographical-information system

The main objective of this project is to realize an integration plan for various renewable-energy systems in remote areas using a geographical-information system (GIS) in order to determine the optimal management and use of energy in these locations. The area studied is Corsica, an island located in the south-east of France. For the remote site considered, four systems supplying electricity are compared: a stand-alone photovoltaic (PV)/batteries system, a hybrid PV/batteries/back-up generator system, an engine generator and an extension of the existing electrical network. The most economic configuration was chosen as the best solution to electrify the remote site. Physical and technical-economical processes are integrated in the GIS. This GIS is used to determine the profitability boundaries for PV systems compared to a grid extension and under four different load profiles, and has led to the elaboration of an integration plan of renewable energies in south Corsica. The study has shown that for 60-90% of remote sites, a PV decentralized electricity system is the most economical means of electrification.

Utilization of meteosat satellite-derived radiation data for integration of autonomous photovoltaic solar energy systems in remote areas

Due to the importance of the relief of Corsica, striking contrasts occur and turn a coastal Mediterranean climate on the littoral into an alpine one in the high mountains. Firstly, we demonstrate, computing a spatial correlogram, that for such countries it is not possible to deduce the solar irradiation received on any part of the island from the meteorological network. Consequently, satellites offer a good alternative for determining these solar data. We demonstrate a good accordance between daily solar irradiation values estimated from Meteosat satellite data and measured data on the considered sites. From the previous data of daily horizontal total irradiations, hourly total irradiations on tilted planes have been computed. These data have been used in an optimal sizing method of PV system, easily applicable to any site. So, for each site on the island of Corsica, we can determine the best adapted PV system, and we analyse differences between sizing characteristics according to the site of installation. Lastly, we have shown very good accordance between sizing results calculated, on the one hand, from measured irradiation hourly data and, on the other hand, from daily satellite images.

Classification of typical meteorological days from global irradiation records and comparison between two Mediterranean coastal sites in Corsica Island.

Abstract In a view to make easier the use of meterological data as the input of energy systems simulations, this study proposes a methodology to reduce a long time series, of several variables into some typical meteorological days, characterizing classes with their frequency distributions and transition probabilities. To do it, we have defined parameters elaborated from hourly clearness index profiles computed from hourly horizontal and inclined irradiation recorded at two nearest Mediterranean coastal sites in Corsica Island. The classification used the aggregation Ward’s method, and the results are confirmed by discriminant analyses. Two studies based on different time steps (monthly and annual) have been investigated. The classes are more compact, and the variances of the meteorological and mathematical variables in a given class remain quite low by comparison with the mean. We show in the first part (monthly time step) that the recorded days are clustered in 3, 4 or 5 groups and in the second part (annual time-step on about 4 years of irradiation data), 3 typical meteorological days classes allows to characterize the irradiation profiles of both locations.

Sizing reduction induced by the choice of electrical applicances options in a stand-alone photovolatic production

The choice of electrical devices has an important part in energetic system sizing and profitability. “Conventional” and “highly efficient” electrical appliances have been studied from both energetic and economic points of view. We showed that it is possible to reduce the PV system sizing by three and the system cost by about four, only by choosing the best appliances without it changes the level of convenience.

Two estimation methods for monthly mean hourly total irradiation on tilted surfaces from monthly mean daily horizontal irradiation from solar radiation data of Ajaccio, Corsica

Abstract The sizing of a photovoltaic or a thermal solar system is generally based on monthly mean values of daily solar radiation on tilted surfaces. Many authors have demonstrated that it will be better to use monthly mean values of hourly radiation, particularly taking into account the Suns position and to predict long-term performances of solar systems. (Liu and Jordan, 1963; Clark et al. , 1984). Moreover, for most of the sites around the world, only monthly mean values of daily horizontal total irradiation are available for use in such calculations. We propose, by using well-known correlations in the literature, to estimate these monthly mean values of hourly total irradiation on tilted planes from monthly mean values of daily total horizontal irradiation, using three steps: • — determination of monthly mean value of hourly total horizontal irradiation; • — determination of monthly mean value of hourly diffuse horizontal irradiation; • — determination of monthly mean value of hourly total irradiation on tilted planes. In the first step, using the Collares Pereira and Rabl correlation, the root mean square error (RMSE) between correlated and experimental calculated data is 8%. In the second step, we used two methods: the first one utilizes the Erbs correlation and the second one is based on a local correlation which has been developed in our centre. Both of them gave identical results with an RMSE lower than 9%. We calculated monthly mean values of hourly total irradiation on three tilted planes (30°, 45° and 60°) and we compared these results with the experimental ones, obtaining a RMSE respectively of less than 10%. The method is then validated by these results.