Philippe Poggi

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.

Stochastic study of hourly total solar radiation in Corsica using a Markov model

The aim of this paper was to study total solar radiation using a Markov chain, with a view to setting up a solar data generator. This meteorological parameter was transformed into another, called the clearness index, and was classified into 20 states. The various transition probabilities between each state were computed. Markov chain properties were investigated and confirm the choice of a first order. The occurrence probability of same state sequences was then studied. It was shown that it can be modelled using a probability law, called the shifted negative binomial (SNB) distribution. Finally, an hourly solar data generator was set up based on these two models, and the real and simulated series from a probability point of view were compared. This confirmed a good agreement of the proposed generator to obtain a typical meteorological year for solar data. Copyright

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.

Costing of a stand-alone photovoltaic system

We have used a life-cycle cost analysis for a stand-alone photovoltaic system with and without an auxiliary engine generator. Because of different published cost calculations, we apply average values or new estimates in the analysis based on examinations of component lifetimes, maintenance operations, fuel consumption, components costs, percentage of installation completed, and discount rates.

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.