Description/achievement of initiative
While most of the simulations reported in the standard literature use the concept of so-called pseudo-stationary states, the collaborative approach of PIMENT (St-Pierre-de-la-Réunion) and LIMSI integrates, in the framework of the 'Dynamic simulation of linear Fresnel solar receptors' initiative, the dynamic behavior of the linear receptor, opening the possibility to simulate operation in tropical climates. Our model also integrates various non-linear effects, such as temperature-dependent thermophysical properties and heat-transfer-coefficient. Increasing the solar flux received by solar absorbers or PV cells with the help of fixed mirrors is not a new idea . The ALEPh project aims at drawing a general conclusion on the optimal geometric setting and materials to produce electricity in a given location and climate. This work is done in collaboration with LGEP (Orsay, expert in PV semiconductor physics and PV cells characterisation), LMD (Palaiseau expert in theory and measurements of meteorological data, and in solar resource forecasting). In 2013, LIMSI and IRSTEA obtained the PEPS project Formhydable from CNRS-INSIS-Energie. Secondary refrigeration loops (filled with a fluid most often neutral with respect to the environment) replace large scale direct-cooling units, e.g. in supermarkets or in hospitals, thus reducing emissions of refrigerant gases with high global warming potential (the smaller the cooling unit, the less it leaks). In 2013, the LBM project was inaugurated. The interest for liquid metal batteries (LMBs) as a solution to meet future electrical energy storage problems is renewed with the studies of Prof. D. Sadoway's group at MIT. In these galvanic cells, three layers of fluids (liquid metal electrode--electrolyte--liquid metal electrode) of different densities are stably stacked over each other by gravity. Another project the CNRS has been involved is the Mélange de micro-nageurs
As the numerical procedure is efficient enough, operation over two years were simulated within some hours only, showing that that technology can be of economic interest in isolated places like La Réunion. Those performance results include the efficiency losses due to procedures which are required for sake of material security during (and mostly after) cloudy spells. Indeed, oppositely to pseudo-stationary models, ours opens the possibility to evaluate the effectiveness of various control strategies when clouds appear and disappear. We elaborated and numerically tested a strategy based on forward extrapolation feedback control moderated by a time constant related to current fluid velocity. The purpose is to maintain the fluid film-temperature under its safety maximum, even in severe situations.Within the ALEPh project, the photovoltaic process combines optical, electrical, thermal, meteorological and grid-related physics. As electrical factors (the most important ones) are non-linear and temperature dependent, while the temperature itself depends on PV performance, simulating this performance is a non-linear problem. This work combines experiments on the SIRTA’s outdoor platform (Palaiseau) on the behaviour of PV panels and two models developed at LIMSI. The Infinite Row Model (IRM) is based on Cartesian optics and analytical solutions. The Ray Tracing Model (RTM), developed under the EDStar environment, focuses attention on irradiation heterogeneities and photocurrent mismatches. These models include reflection, absorption and transmission of visible and near-infrared radiations, calculation of the irradiation, and temperature dependence of cell efficiency. The ALEPh experiment proves a gain from 5 to 32% in daily electricity production.Within PEPS, in collaboration with IRSTEA, the group constructed a first-generation model of a very simple loop, inserted between the evaporator of the cooling unit and just one heat-exchanger where cold is finally used. Ice slurries have been used for long in industrial environment because they offer the advantage of large changes in specific enthalpy (phase change) over reduced temperature glide. New types of slurries are currently under study, clathrate-hydrates, which are ice-like crystalline compounds, mainly made of water molecules that form cages around host molecule(s) thanks to their hydrogen-bonds. Fusion temperature of hydrate slurries lies over zero Celsius (e.g. 7 or 10°C); in addition, it can be adjusted to the designed application. As far as the LMB is concerned, Intense electrical currents passing through LMBs might trigger Magneto-Hydro-Dynamical (MHD) instabilities and thus induce fluid flows that can destroy the integrity of the stratified structure of the battery. This problem is studied with our numerical MHD code SFEMaNS extended with a new multiphase MHD module that allows to simulate flows in LMBs.
Arrangements for Capacity-Building and Technology Transfer
Coordination mechanisms/governance structure