Bringing storage out of storage

Issue 39 – June 2012

Why storage technologies deserve a place of honour in Smart Grids

EES (Electrical Energy Storage) is becoming increasingly important as alternative energy sources, such as wind and solar, feed into the grid. EES allows for power flow to be controlled, reducing generation costs and balancing power fluctuation.

The need for balance and control

Today, power generally flows in one direction only, from the power station, via the transmission and distribution grid, to the final consumer. Maintaining balance is complex but achievable via centralised facilities. Since electricity is normally consumed at the same time as it is generated it will become increasingly difficult to maintain power stability and quality as decentralised power generation such as roof-top photovoltaics, but also large wind farms, sporadically feed power into the grid. Future power systems will not only need to accommodate bi-directional power flows and an increasing transmission of information, they will also have to integrate renewable often intermittent energy sources while mitigating congestion and maintaining voltage in the appropriate range.

The Smart Grid is expected to control the demand side as well as the generation side, so that the overall power system can be more efficiently and rationally operated. It includes control and other technologies as well as IT and communications. One technology that is today largely underdeveloped and lacks sufficient attention is Electrical Energy Storage (EES).

Reducing generation cost, increasing reliability

EES will allow utilities to reduce overall generation cost and achieve higher efficiency with intermittent renewables as well as accommodate descentralised generation by storing surplus energy for later use. Excess production during off-peak hours can be used during peak demand; this helps make full use of the generation potential and reduces the cost of electricity. Energy Storage also allows an increase in the reliability of the network and provides back-up during power failures.

In some cases, EES can reduce investment in power system infrastructure such as transformers, transmission lines and distribution lines through load levelling in certain areas at times of peak demand. EES for this purpose may also be used to enhance frequency control capability.

Mitigate congestion, maintain voltage

EES installed in customer-side substations can control power flow and mitigate congestion, or maintain voltage in the appropriate range. It helps to smooth out intermittent generation such as those by wind and sun and modulates excessive power fluctuation and undependable power supplies.

Mobile power sources

Energy storage can also support the electrification of existing equipment so as to integrate it into the Smart Grid. Electric vehicles (EVs) are a good example since they have been deployed in several regions, and some argue for the potential of EVs as a mobile, distributed energy resource to provide a load-shifting function in a Smart Grid. EVs are expected to be not only a new load for electricity but also a possible storage medium that could supply power to utilities when the electricity price is high.

Better planning of local consumption

Storage will facilitate energy management in homes and buildings. With intelligent consumption management and economic incentives consumers can be encouraged to shift when they use energy. Users may accomplish this by buying energy when surplus power is available, often at a lower price and storing it for later use.

Finally in micro-grids and decentralised generation, storage will allow for optimising and planning local consumption. This approach is successfully applied in many communities in Japan.

Better Smart Grids

Here are some examples in which EES will contribute to make Smart Grids better:

  • Increased penetration of renewable energy requires more frequency control capability in the power system. EES can be used to lessen the imbalance between power consumption and generation allowing network operators to control charging and discharging.
  • EES can reduce investment in power system infrastructure such as transformers, transmission lines, and distribution lines through load levelling at times of peak demand. EES for this purpose may also be used to enhance frequency control capability.
  • EES can reduce the need for costly spinning reserves, reducing total generation costs. Storage of electricity generated by low-cost power plants during the night is reinserted into the power grid during peak periods.

Reproduced from IEC newsletter, e-tech, May 2012

Published in energy.