Storing energy consists of building reserves that can later be consumed on demand, without needing to call on a source of production. In today’s climate, with global warming driving society to increase our use of renewable energies, storing electricity is turning out to be one of the major challenges of the energy transition.
Energy storage refers to any technique that allows for the creation of energy reserves. One technique is to convert electricity into a different type of energy that is easier to store. Hydraulic storage, for example, consists of transforming electrical energy into mechanical energy by pumping water upwards and then storing it at a higher point. When it is released into a turbine, this water once again generates electricity thanks to the power of gravity.
Another solution consists of storing electrical energy in electrochemical form through an exchange of ions and electrons between two electrodes: this is the principle of a battery. Originally designed for mobile applications (high-tech devices, electric cars,) it is now used for stationary energy battery storage systems.
Energy storage is one of the key components in the integration of intermittent renewable energy sources, such as solar and wind power, into the “energy mix”. It compensates for their fluctuation, acting as a reserve that is filled during peaks in production and emptied out during lulls in production.
Stationary energy battery storage systems are one of the primary ways that electric car batteries can be reused once they can no longer be used to power a vehicle. Given a second lease on life, they are able to store energy in situations that are less limiting and less demanding in terms of energy and power density.
The Porto Santo Fossil Free Island project in the Madeira archipelago has two stationary energy storage systems that use second-hand batteries. These batteries come from Renault electric vehicles and are no longer up to the demands of powering a car. They are, however, perfectly suited for stationary use. They now act as voltage regulators and network stabilizers, and store intermittent energy produced by the solar and wind farms on the island, which is kept for local use.
In Belle-Île-en-Mer (an island on the french west coast), the program FlexMob’ile brings together local communities, transport operators, energy distributors and unions. Through this program, Renault will equip the island’s biggest resort with second-hand batteries from its electric cars. The batteries can be used to store the surplus of electricity produced by the building’s solar panels during the day, then later give it back to help charge self-service electric cars or heat vacation bungalows.
Other projects aim to use electric car batteries for stationary energy storage on a larger scale. This is the case, for example, for the Advanced Battery Storage program announced by Renault in late 2018. This plan aims to build a system capable of storing at least 60 MWh and providing 70 MW worth of power. In the long term, this system split between several sites in France and Germany will provide a reserve capable of meeting the annual consumption needs of more than 5,000 households. The goal is to offer specialized operators a tool to stabilize the frequency of the electricity grid in order to deal with imbalances between electricity consumption and production. These systems therefore become part of the framework to intelligent network management (smart grids).
At the heart of circular economy practices, the reuse of electric car batteries reinforces the competitivity of renewable energy, as it decreases CO2 emissions in the creation of ad hoc infrastructures. Stationary energy storage systems thus make solar- and wind-powered electricity production even more appealing.
They are the perfect complement to vehicle-to-grid projects, which consist of using electric car batteries as an energy reserve for the electric grid.
Democratizing energy storage also contributes to the emergence of auto-consumption scenarios in which a household or community may stock and consume the energy it produces directly.
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