The Need for Energy Storage
The prospect of energy storage deployment on a large scale is seen as a “game changer” for the global energy industry. The need for energy storage arises from a confluence of industry drivers. Today’s grid was not designed for optimal efficiency nor for its current uses. Modern electrical loads and the increased deployment of renewable energy are causing grid instability with technical, financial and social consequences. The grid is increasingly facing high capital costs to manage grid peak demands and needs large infrastructure investments to improve its reliability. At the same time, overall renewable energy generation needs to be used more efficiently to be profitable, independently of the grid. Through a large number of applications, energy storage addresses many of these issues by better aligning electricity production with electricity demand, while also improving the quality and reliability of electricity delivery. Additionally, by improving grid and renewables efficiency, energy storage can also play a pivotal role towards a low carbon future.
Types of Energy Storage
It is therefore surprising that in the EU only 5% of installed electricity capacity is currently stored, and almost entirely in the form of hydroelectric storage. The other stationary storage technologies (mechanical, thermal, electric chemical and electrochemical) are in various phases of development and have very different characteristics.
Amongst these storage technologies, electrochemical storage has long been the focus of much research, given its attractive features and potential range of applications. Electrochemical storage systems fall into two groups: solid state batteries and flow batteries. Solid state batteries are known as ‘closed systems’ (where the relationship between power (kW) and energy (kWh) is fixed) and the energy is stored as an electrode. These include conventional lead acid batteries and lithium-ion batteries.
Flow batteries (redox and hybrids) are also referred to as ‘open systems’. In flow batteries, the energy is stored in the form of electrolytes (a solution) which circulates through cells containing the electrodes and is stored in separate tanks. Here, power and energy are totally independent and can be tailored to individual applications, a significant advantage over closed systems. Flow batteries are usually named after the two metals used in the chemical reaction, such as Zinc-Bromine. Vanadium redox, the only type which uses a single metal, has long been regarded as one of the best potential solutions for large sale stationary energy storage.