The energy transition will depend on a significant increase in the production of renewable electricity, particularly generated by wind farms and photovoltaic panels. The specific feature of these two technologies is that they depend on weather conditions, implying variable production that cannot be managed. Hence a potential lack of synchronization between electricity production and demand. In order to maximize the share of renewable energies in the energy mix, IFPEN proposes technological innovations for the integration of variable renewables in the networks, thereby supporting the development of technically and economically viable energy storage sectors.
Energy management systems
Energy storage can deliver a variety of services to the network (arbitrage or load management during peaks, for example): depending on their specific characteristics (investment and operating costs, yield, acceptable depth of discharge, etc), the various storage technologies vary in their suitability to meet these needs. IFPEN is developing a multicriteria analysis approach capable of identifying the best technical solutions in terms of their economic and environmental challenges. Its research activities incorporate the simulation of the system concerned throughout its life span and are hinged around the capacity to develop Energy Management Systems or EMS.
«An EMS is a system of computer-aided tools designed to optimize the performance of energy systems, applying strategies making it possible to fully exploit a storage system within a specific network. Such systems are of interest in contexts as diverse as:
- Smart Cities, where they operate on various levels (building, district, town/city). An EMS aggregates historic data and produces production and consumption forecasts in order to optimize storage and demand management (charging stations, for example). Combined with smart networks, an EMS enables the optimal management of complex situations,
- remote sites where it is necessary to manage a storage system to create an electricity network or support a fragile electricity network.
Our optimization, data science and system control expertise, combined with the performance of our testing facilities enable us to develop Energy Management Systems with a view to proposing three types of services:
- steer the integration of renewable energies in electricity consumption and identify associated investments. Our objective is to propose a web-based electricity invoice optimization tool that incorporates possibilities of producing electricity from renewable energies, according to various electricity buying/selling models. Our long-established battery modeling expertise enables us to incorporate storage battery aging into the calculations,
- balance a network by managing complex situations. We are working on remote storage system planning and management services. To predict electricity consumption and production, we rely on historical data and develop smart models (machine learning). Our microgrid equipment at our Lyon site enables us to test and validate our developments,
- storage system hybridization, such as, for example, recourse to photovoltaic and wind power producers to reinforce the capacity of hydroelectric power stations (PSPPs). This hybridization of hydraulic storage systems is a problem encountered in remote electricity networks (islands, Africa), requiring the creation of a management system to coordinate hydraulic and solar electricity production operations. Our reflection process is centered on the simulation and dimensioning of the system as a whole.»
Philippe Pognant-Gros, EMS project manager, IFPEN
Advanced adiabatic compressed air energy storage (AA-CAES)
Compressed air energy storage has existed since 1978 (Huntorf power plant in Germany) in the form of enhanced gas plants with a maximum energy efficiency of 50%. In these old Compressed Air Energy Systems (CAES), the heat produced by compression is lost. A more sophisticated concept is Advanced Adiabatic Compressed Air Energy Storage (AA-CAES): this solution makes it possible to store compression heat and achieve a far higher degree of efficiency.
«Using the AA-CAES principle, we are developing a system based on:
- in its first version, components that already exist, such as compressors and turbines,
- in a second version, new components such as thermal energy storage (TES) systems.
It operates as follows:
- storage is based on air compression and heat storage,
- air is passed through turbines following re-heating to release the energy from storage.
This technology is particularly interesting because it can be located close to where it is required: for energy quantities of up to a few dozen MWh, the air storage facility can be installed above ground. We are focusing our developments on two aspects:
- improved management of heat transfers during air compression and expansion phases:
- process optimization,
- choice of pressure ranges,
- use of materials and improved exchanger design,
- reduction in the cost of air storage units, via the development of alternatives to the use of steel tubes, which are too expensive.»
David Teixeira, compressed air energy storage project manager, IFPEN
Electrochemical storage via Redox flow batteries
Electrochemical storage, particularly via Redox Flow Batteries, is suitable for applications requiring the storage of significant quantities of energy, especially since the large-scale roll-out of the solution makes considerable cost reductions possible.
Redox flow batteries are, in fact, rechargeable accumulators that have the capacity to store energy in the liquid phase:
- two liquid electrolytes containing electro-active species in solution circulate within the two positive and negative compartments of an electrochemical reactor, these compartments being separated by an ion-exchange membrane,
- the electrolytes are stored in tanks.
The main components of a flow battery are:
- stacks: individual cells are mechanically combined and electrically connected in series to achieve standard direct current voltages,
- electrolyte tanks,
- pumps and pipes necessary to enable the electrolytes to flow,
- the BMS (Battery management system),
- the DC/AC conversion system (PCS / Power conversion system)
«The specific characteristic of Redox battery technology lies in the separation, in terms of design, between:
- the power, governed by the active section of the electrodes and the membrane (reactor size) and by the circulating electrolyte flow (pump flow rate)
- and the quantity of energy stored, which depends on the quantity of electrolytes present in the tanks.
This technology thus offers unique modularity, since the batteries can be scaled to the desired power and energy and thus be adapted for use in a large number of applications. However, the relatively low energy density of the electrolytes does represent an important drawback: the preferred fields of application for these batteries thus lie in the intermediate power ranges from around 10 kW to several MW, and storage times of between two and ten hours.
To facilitate the roll-out of the technology, our research activities are aimed at:
- developing new, cheaper and more efficient electrolytes than existing ones, such as vanadium, notably by creating organic systems
- optimizing system management using multi-physical and multi-scale modeling
- understanding elementary mechanisms (electrochemical reactions, matter transfer) via multi-scale characterization (laboratory, pilot and demonstrator).»
David Pasquier, Energy Storage project manager, IFPEN
Watch a video on Redox flow batteries with David Pasquier, project manager, IFPEN (in French):