Energy Storage

Electrostatic Battery

  • Capacitor

    • Capacitors store charge on the surface of their electrodes, they do not store any charge within it, therefor generally have a lower energy storage capability

    • When compared to traditional batteries, their capacity is much lower, but their discharge time is considerably lower as well. They also exhibit life cycles which are a few orders of magnitudes higher than batteries

    • Even with the use of super capacitors there are limitations, including lower voltages, or lower capacitance when serried

    • The main use of capacitors as energy storage comes in the form of power backup for memory circuits and in conjunction with batteries to provide a power boost if needed


Thermal Battery  

  • Molten Salt

    • Molten salt batteries are designed to store excess thermal energy built up during the day and release it at night as to have a constant energy supply

    • This method works as the sun’s thermal radiation is used to heat a high thermal capacity salt with a suitable melting point (usually 300℃+)

    • This mixture is then stored in an insulated container until the energy is required, at which point it is used to keep the generator running

    • There are many methods used to extract the heat, but most end up transferring the heat to water passing through a heat exchanger to create steam

  • Ice Battery

    • Ice batteries are mainly made for use with air conditioning units. They take advantage of lower off-peak electricity tariffs during the night to store cooling energy. This energy is then used during high-peak times to offset electricity usage.

    • During the night, these systems go into charging mode, in which they compress refrigerant and pump it through a series of copper coils in large insulated water tanks where it evaporates. This freezes the water in the tanks, storing it for use during the next day

Clockwork Battery

  • Springs

    • Clockwork batteries take advantage of energy storage within springs. The springs are wound up by a clockwork mechanism, and once released will drive a dynamo which provides electric power

    • These systems are only suitable for low capacity and low power applications, however their discharge time can be extended using gears

Kinetic Battery

  • Flywheel

    • Energy storage using a flywheel is old technology, and is rarely used any more as they are large and heavy

    • Modern highspeed rotating flywheels are used instead. They store energy in rotating drums which form the rotor of a motor generator

    • When there is excess electrical energy, it is used to speed up the flywheel, storing energy. When the load is increased, the stored energy is used and the flywheels speed falls

    •  There are some set backs accompanied with using flywheels, which have to do with the speed of rotation and the strength of the materials required due to the centripetal forces experienced

    • There are many benefits to using flywheels instead of batteries, a few include:

      • 5-10 times greater specific energy

      • Long lifespan, unaffected by number of charge/discharge cycles

      • High charge/discharge rates and no taper charge required

    • Flywheels see practical use as protection systems for interruptions to the national electricity grid. When the grid losses power and needs to initiate back-up generators, flywheels are used to provide ride-through time

Hydraulic Battery

  • Pumped Storage

    • Pumped storage hydroelectricity is a very commonly used method of energy storage around the world

    • This method is very simple and easily implemented. The water is pumped to a reservoir which is elevated at low-peak electricity times, then released through a generator at high-peak time

    • The round-trip loss is usually 20-30%, but due to its simplicity and huge capacity, it is a very attractive energy storage system

Magnetic Battery

  • Superconducting Magnetic Energy Storage

    • They store energy in the field created by direct current flowing in a large magnetic coil cryogenically cooled to a temperature below its superconducting critical temperature when an electrical currents flow without resistance or loss of energy. This is then converted back to AC electric current when needed

    • Their lifespan is very high and these systems have the highest round-trip efficiency of any storage device available, but we do not see many of these systems in production due to their high manufacturing and maintenance costs

Nuclear Battery

  • Radioisotope Thermoelectric Generator

    • These batteries are essentially nuclear powered heat generators which use energy emitted by the natural decay of radioactive isotopes of Plutonium which provide heat

    • Due to the thermoelectric process used to get the energy released the overall efficiency is only about 4%, but due to the extremely high energy density of the source this is not an issue

    • Radioisotope Thermoelectric Generators have 1000s of times higher energy density than Lithium Ion batteries