Christian Cristofari

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.

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.

Hourly Solar Irradiations Estimation : From Horizontal Measurements to Inclined Data

We quantify the accuracy of various well-known models of the literature: the seven first type of models calculate diffuse horizontal irradiations from global ones and the fifteen second type models compute global irradiation on inclined planes from diffuse and global components on a horizontal surface. Then, the two classes of models are combined and the adequacy of each association is calculated for experimental hourly data collected on a French Mediterranean site. We compared these combinations with the Olmo model transforming directly global irradiations on tilted planes from horizontal ones.

Coupling hydro and wind electricity production by water - pumping storage

We quantify the capability of coupling wind farm and hydraulic plant, in view to produce energy without fluctuations, like wind farm alone. In fact, we suppose the hydraulic plant is like a buffer, and the wind farm fed this buffer. The aim is to satisfy a certain quantity of energy, more particularly, a percentage of the peak load. We can so optimize the system : power of the wind farm with the power of the hydraulic plant.

Calculation of solar irradiance profiles from hourly data to simulate energy systems behaviour

In various studies of solar energy systems (sizing, estimation of production), we need solar irradiation data collected with a smaller time interval than those often available in databases (often hourly irradiations). We compare three models (constant, linear and extraterrestrial) which simulate an hourly profile of solar irradiance and allow the determination, with a given reliability, of minute data of global solar irradiation from hourly measured irradiations. These models are compared from the point of view of various statistical tests using data collected on a Mediterranean site. The extraterrestrial model shows very satisfying results and improves greatly the accuracy compared with a constant model.

Pumped hydroelectric storage coupling wind-solar resources: A solution for increase ren on islands electrical grid

The energy problem of islands differs from those in mainland countries because islands need to manage their own energy supplies. The islands are good test beds for the utilization of renewable energy production and storage technologies. We present the main problems related to the electrical production in small islands and by the utilization of renewable energy plants; the necessity to integrate some energy storages is shown and various storage means are classified. At last, the hydro pumping storage will be presented as a good solution for participating to the increase of the penetration rate of renewable energies, particularly in island electrical grid.

Patented twintex® hybrid PV/T collector: Level of performances and comparison with thermal solar collector

In the context of climate change in the world at the global level, various actions are taken for the development of Renewable Energy and particularly solar energy. Many technology solutions have been proposed such as solar hybrid collector whose objectives is to improve the PV panels performance by recovering heat looses with the heat removal fluid. The objectives of this article is to propose a hybrid photovoltaic-thermal collector manufactured in a polymer material twintex® patented by Saint-Gobin company, to have product lighter, cheaper and easier to handle. We expose the performance of this PV-T collector manufactured without air layer.

Study of the thermal behaviour of a production unit of concrete structural components

Abstract We propose an economic and technical optimisation of a small concrete structures workshop. The heat released by the chemical hydration reaction is modeled and validated with experimental data. A nodal model of the thermal response of the incubator internal air, using an electrical analogy approach, is realised. The equivalent time is calculated and a battery of air treatment units is sized to reach the mechanical resistance for handling in an acceptable deadline whatever the meteorological conditions are. The solution minimizing energy costs by studying the influence of inherent parameters of the system and step regimes of the workshop has been conducted.

Modelling of the Ventilation Unit for a Stand Alone Solar Collector

The work described in this paper concerns a part of the modelling of a standalone air solar collector producing low temperature heat. The main role of the system is to avoid freezing temperatures and to reduce humidity in a room or in an unoccupied home during a long time, with only solar radiation. In view to dispose an essential sizing tool for this solar collector, we developed a mathematical model based on energy balance equations and on the characteristics of the system. This model allows simulation of the aerolic and thermal behaviour of the solar collector. It was validated using experimental data collected by telemetry in six operating sites. We present here the behaviour model of the ventilation unit part.

Gross Error Detection of the Generator of a Wind Turbine

Data reconciliation and gross error detection are techniques used for improving the accuracy of data so that they satisfy the plant model. This paper present a method to identify and estimate gross errors for linear dynamic systems. An appliation is made in the domain of renewable energies, in particular the doubly fed induction generator (D.F.I.G) of a wind turbine. A dynamic integral measurement test is used to identify measurements as suspects of gross error. The method presented in a previous paper [1] is extended to allow gross error estimation.