Use for network applications
Because electricity is more difficult to store than to transport, electric networks have been conceived and exploited at anytime to maintain the balance between supply and demand. Apart from applications on a remote spot or on an island, the electrochemical storage of energy is still marginally used. However, for 10 years, new Na-S and Li-ion battery technologies, with high performances and adequate life spans, have been used to handle the intermittent renewable energies i.e. photovoltaic and Aeolian, and to offer the electric networks new possibilities.
In the context of an energetic mass storage necessary to an efficient handling of the network and managing peak energy demands, redox-flow batteries represent a very booming domain. They are mainly stationary systems where stored capacity and power can be separated by storing reactants outside the electrochemical cell with pumps ensuring its supply in reactants. The idea of Li-ion redox-flow based on the flow of conductive inks/suspensions , and not on the flow of solutions, is presently shaping up.
Flywheels can be viewed as mechanical batteries as energy is stored via a solid rotating at high speed. We are talking about systems perfectly adapted to short-term network storage. The amount of stored energy is determined by the size of the rotating object, its shape and speed. In spite of the still weak energy densities, the advantages of these systems are a long life span and the absence of chemical risks. 20MW stations have already been installed in some distribution networks. Therefore the cost remains an issue.
Electrical Energy Storage has often been described as the “Holy Grail” of the electric utility industry. This phrase evokes the eagerness of utilities and other stakeholders to achieve cost-effective storage options, which could potentially cure many of the ills faced by the electric power enterprise. Whether we deal with batteries, redox-flows or flywheels, still today none of these technologies can compete, for cost reasons, with the hydroelectric storage. A number of demonstration projects, ranging in size from 5 to 50 MWh and using a variety of different chemistries, are underway. The outcomes from these projects over the next 2 to 4 years will have a substantial influence on the future of this technology. The recent developments involving Li-redox flow and alkali-redox flow batteries stand as great opportunities that leverage existing knowledge of Li-ion batteries with the advantages of redox-flow systems. The market is huge and full of opportunities.