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EmailEnergy Storage: Continued
November 30, 2007Page 9 of 15
- Electrical - Electrical storage is an efficient way of delivering power without the need for chemical or mechanical conversion. Storing electrical energy is likely the most efficient way of maintaining electricity because there is no conversion element required.
- Supercapacitors- Supercapacitors store electricity in their charge field and have almost infinite charge cycling. These storage devices contain of a thin-film polymer dielectric sandwiched in between two oppositely charged metal plates. Carbon nanotubes create porosity in the dielectric, which brings the metal plates closer and generates a more intense electric-field charge. Although they have a lower energy density than batteries, supercapacitors charge in milliseconds and emit high-voltage bursts, which are useful for starting engines in battery-drained ZEVs as well as for load leveling in power-generation systems.
- Superconducting Magnetic Energy Storage (SMES)- SMES systems capture DC currents in the magnetic field of a cryogenically frozen superconducting coil and store that energy for an infinite amount of time. They allow for nearly instantaneous power output at high bursts over short periods and are useful for load leveling and grid stabilization.
- Mechanical- Mechanical energy-storage methods rely on the potential energy of mechanical motion. Energy conversion from potential to kinetic energy involves some efficiency losses, though it is the least technically complex form of energy storage. A widely used form of mechanical energy storage is water pumping, where water is moved to a higher elevation and pumped through a turbine generator. Mechanical storage requires high capital investment and construction costs. However, it is the most commercially advanced of the green energy-storage technologies and the only technology currently available to provide pervasive base-load support for green power-generation sources.
- Flywheels- Flywheels are wheels suspended in vacuum tubes and supported by bearings. Hybrid systems in newer technologies combine magnetic bearings with high-temperature superconductor bearings and divide work between load support for the former and stabilization for the latter. Energy is stored as rotational energy, and is converted by slowing the flywheel to produce an electric current. Flywheels serve to fill gaps for uninterrupted power supplies and for enhancing the power quality of green power-generation technologies.
- Compressed Air Energy Storage (CAES)- CAS systems use off-peak power to pump pressurized air in underground caverns. Oil exploration and recovery companies have used similar technology for a number of years to stimulate dried oil reserves below ground. When load demands increase, the pressurized air is heated and released to spin turbines that generate electricity. CAS systems have the benefit of easy retrofitting into existing power plants. When combined with natural gas to raise heat, these systems emit fewer GHGs than natural gas alone.
| Supercapacitors |
| EEStor |
| Flywheels | |
| Pentadyne Energy Corp. | Vycon |
| Compressed Air Energy Storage (CAES) | |
| CAES Development Co. | General Compression |