A longstanding need
Electricity is consumed at it is produced. There is a need for continuous and flexible supply. An imbalance between supply and demand leads to instability and lower power supply quality. Electricity is also often generated some distance away from where it is needed and then has to be supplied to consumers via the grid, with the attendant possibility of failure or network congestion.
Power demand varies with the time of the day and season, and prices change accordingly. In the summer of 2011, as air conditioning units were switched on across Texas, causing sharp spikes in demand, to avoid blackouts the state grid operator had to buy all the electricity it could find on the spot market. In some cases this meant paying 30 times the normal price.
REs, which will provide a growing share of electricity, are often intermittent and unreliable. They can provide too much or not enough power or generate it when it is not needed, so EES can represent an interesting solution in balancing RE production and distribution.
EES is expected to play an essential role in the future Smart Grid. It could control power flow and mitigate congestion. It could also support the electrification of existing equipment for its integration into the Smart Grid. EVs (electric vehicles) are one example: they could act as a mobile distributed energy source and possible storage medium for supplying power to utilities at peak time.
The third role envisaged for EES in the Smart Grid environment is as an energy storage medium for EMS (Energy Management Systems) in homes and buildings. EMS are designed to involve customers and encourage them to modify their energy use patterns.
Advantages for all actors
EES presents many advantages for utilities, businesses and consumers and RE generators alike.
Time shifting is one advantage all derive benefit from. For utilities it means being able to balance supply and demand and to cope with peak time or sudden surges in demand by storing electricity at off-peak times and supplying it at peak times. For consumers, time shifting implies cost savings, as electricity can be used and purchased at off-peak times. For RE generators, time shifting means the possibility of storing surplus energy in EES and using it when necessary.
EES offers another advantage. It can provide three kinds of storage for different uses: a very short-term one (seconds) which ensures power quality, storage of medium duration (minutes to a few hours) to cope with sudden peaks of demand and a longer type (several hours to days) that enables all parties to benefit from lower generation costs and supply and demand to be balanced.
All of these actors may also profit from other specific benefits detailed in the White Paper.
Types and features
The White Paper lists the various EES systems and gives extensive details of their features and different characteristics with supporting diagrams and figures.
It separates EES systems into a variety of categories: mechanical (e.g. pumped hydroelectricity, which represents 99% of all available EES, plus compressed air and flywheel), electrochemical (e.g. secondary and flow batteries), chemical, electrical and thermal. These systems determine in great part the different markets in which EES is deployed.
From utilities to consumers
EES is widely used by utilities to reduce their costs and regulate supply. Pumped hydroelectricity is particularly valuable here: excess generation capacity available during low demand periods is used to pump water into a higher reservoir from where electricity can be generated during peak time. This time-shifting method of generating electricity ensures it is available when needed to meet excess demand and ensure regular supply and power quality. However, in some countries, physical limitations imposed by topography mean that there is no further potential for increased use of pumped hydroelectricity.
Utilities also use EES for off-grid systems, for instance on islands, where systems such as batteries connected to wind or solar generation and diesel-powered generators can be deployed.
Large consumers, including businesses, can also cut their peak time demand, purchase off-peak electricity and store it in EES – for example, batteries.
EES will help manage the supply and demand of REs whose output is naturally unpredictable. This is important for utilities, but also for households, which can use decentralized storage systems.
Smart Grid, smart homes
Today's grids are distributing power in one direction only: from power plants to end users. The future distribution system will be smarter, based around bi-directional flows that will also carry information. The decentralized installation of RE generation sources, such as wind and solar power, and their integration into the general grid will need managing.
The Smart house concept is seen as a means of using energy more efficiently, economically and reliably in residential areas. In the smart home, all the devices and appliances are connected so that they can "talk" to each other.
Future market and recommendations
In addition to a comprehensive description of EES technologies and of current and future applications and opportunities, the White Paper provides a projected forecast of the EES market in 2030, with results based on studies that cover almost all applications and others that focus on new applications specific to EES.
It also offers recommendations in the areas of policy (including regulation), research & development and standardization.
This wide-ranging and compelling 91-page document prepared by the Electrical Energy Storage Project Team, part of the MSB Special Working Group on technology and market watch, with a major contribution from the Fraunhofer Institut für Solare Energiesysteme, is essential reading for the power industry, all decision-makers and individuals interested in understanding future energy challenges and some of the measures that must be taken to meet them. It can be downloaded here