Energy Storage Technologies


A flywheel is a mechanical battery that stores kinetic energy in a rotating mass.   When electricity demand is low, the flywheel uses power from the electrical grid to drive a motor that spins the flywheel at high speeds, allowing the flywheel to store excess energy from the grid. When demand is high, the flywheel’s momentum causes the motor to act as a generator, which then slows down the flywheel, putting power back onto the grid.

Solid State Batteries

A solid state battery has both solid electrodes and solid electrolytes. They are able to convert stored chemical energy into electrical energy.  The electrolytes allow ions to move between the electrodes and terminals, allowing currents to flow from the battery to provide energy.   Types of Solid State Batteries include:

  • Electrochemical Capacitors
  • Lithium Ion Batteries (LI-ION)
  • Nickel Cadmium Battieres (NI-CD)
  • Sodium Sulfur Batteries (NAS)

Pumped Hydro

Pumped Hydro is a type of energy storage used by power systems for load balancing.  Pumped hydro storage facilities work by storing energy as water, pumped from lower reservoirs to higher reservoirs. When electricity demand is high, power is generated by releasing the stored water through turbines, similar to conventional hydropower stations.  When electricity demand is low, the excess generation capacity is used to pump water into the upper reservoir. Pumped Hydro works both as a turbine and a generator. Differing from conventional hydroelectric stations, pumped hydro storage stations are a net consumer of electricity as a result of the hydraulic and electrical losses incurred in the cycle of pumping from the lower to upper reservoirs.

Compressed Air

Compressed Air Energy Storage takes air, compresses it and stores it under pressure in underground caverns.  When electricity demand is high, the pressurized air is heated and expanded in an expansion turbine which drives a generator for power production. There are various ways of storing the energy underground, one of which is via underwater accumulators. 

Electric Vehicles 

Electric vehicles - and their batteries - can be considered as both controllable load during periods of lower demand and, with the appropriate technologies, a source of supply during times of higher demand. Using smart electric vehicle charging stations, customers would supply the grid or use the electricity to meet their own energy needs.

Thermal Energy

Not all stored energy necessarily comes directly back to the power grid as electricity. Off-peak energy can be stored as thermal energy, which can then be used to supply heating and/or hot water needs, reducing electricity consumption during on-peak periods.  Increasingly, solar thermal systems are being used around the world to supplement or replace the electrical energy drawn from the grid for such uses.  Ice storage systems do just the opposite where off-peak energy is used to make large blocks of ice to help cool buildings during peak hours. Other more sophisticated, high-temperature thermal storage systems can also be used to generate steam for electricity production to supply back to the grid.    

Fuel production

Electricity can be used as an input in the production of other types of fuels such as hydrogen and biofuels, which can also act as an energy storage medium.  These fuels can then be used to generate electricity to send back into the grid at optimum times − or for other non-electrical energy needs. Off-peak electricity can also be used for compressing natural gas − an emerging need in the transportation sector.  

Magnetic fields

Magnetic fields are capable of storing electrical energy, and when coupled with superconductors, the storage potential can be significant. Some pilot projects involving superconducting magnetic energy storage are currently under development at various laboratories and utility equipment providers around the world. However, the future success of these new forms of energy storage devices is highly dependent on the cost of the  superconductors themselves.