The energy challenge is regularly on top of the world’s political, environmental, and economic agenda. Pushed by demographic growth, aspirations for better living conditions, and the development of digital technologies, electricity consumption is set to double between 2010 and 2030.
As a result, the use of renewable energy becomes a key factor in solving the equation between growing energy demand and the need to reduce greenhouse gas emissions. However, the increase in the introduction of renewable energy into the grid, which has been primarily designed to carry electricity from large power plants to consumers, creates new challenges. More popular renewable energy sources, like solar and wind, are intermittent by nature, which means energy production from these sources can be unpredictable or varied.
The rule of thumb for transmission and distribution grids is that what comes in should be equal to what goes out. If a source of energy suddenly produces less, the demand should be reduced (which is not always possible), or another source of energy should compensate. The same principle applies if a source of energy suddenly produces more; then more energy needs to be utilized. Intermittent renewable energy sources like solar and wind consequently require more flexibility from other energy sources connected to the grid. But this flexibility has a price and is not always technically feasible. To combat this challenge, excess energy needs to be stored and then released when needed.
Energy storage is not completely new to electricity grids. In many places in the world, excess electricity is used to step up water to high altitude dam lakes. When energy is required, pumped water is released and sent to turbines that produce electricity back. Water is then collected in low altitude dam lakes so that the cycle can start again. But this solution is not applicable everywhere. It requires mountains to make up the difference in height between the high altitude and the low altitude lake. The number of locations in the world where this can be implemented is limited. Additionally, the response time of this solution is not exactly compatible with the response time needed by renewable intermittencies.
The recent rise of mobile devices and promises of electrical vehicles have boosted technological developments in the field of electricity storage. New battery, supercapacitors, and flywheel technologies are popping-up on the market more frequently, and offering new and exciting perspectives for electricity storage integration into grids. New battery technologies like lithium-ion, sodium-sulphur, and flow batteries, are today the most advanced and can already be used to build large scale energy storage systems associated with intermittent renewable energy sources, or connected at different grid nodes.
A battery-based energy storage system is composed of two main elements: a large battery made by assembling a great number of battery cells most often located in a shipping container, and a power conversion station. At the heart of the power conversion station, one or several inverters ensure the conversion of DC energy coming from the battery to AC energy sent to the grid, or reversely the conversion of AC energy coming from the grid to DC energy used to reload the battery. When the energy storage system is associated with intermittent renewable energy sources like PV or wind, the AC energy used to reload the battery can also come from PV arrays or from wind turbines.
Stay tuned next week when we will publish a follow up blog post outlining some of the applications of a battery-based energy storage system.