A recent patent issued to compressed air energy storage (CAES) company SustainX could provide a significant improvement in grid storage of energy, especially for wind farms and solar power arrays.

Compressed air is one of the preferred methods for storing excess energy from renewable sources during periods of peak production. When there is increased demand, it can then be readily harnessed to provide additional electricity, instead of relying on fossil fuel burning 'peaker plants' or other, less desirable alternatives.

The problem with compressing air comes from thermodynamic effects. "Without heat transfer, a gas will increase in temperature as it is compressed; and as it gets hotter, it tends to resist further compression (i.e., each increment of compression must be performed on a volume of gas that is at higher pressure than if it had not been heated by prior compression)." SustainX has developed technology to provide isothermal compression and expansion which gives their system conversion efficiencies of over 90%. And, of course, better conversion efficiencies mean less energy is wasted.

With this technology, SustainX claims a 7x cost reduction over traditional CAES systems. Additionally, according to the company, "SustainX utilizes above-ground storage in the form of industrial-grade, off-the-shelf gas cylinders, eliminating the siting constraints and permitting concerns associated with classical underground CAES."

via: N A Windpower

MIT scientists have made new discoveries that could significantly increase the energy density of batteries several times beyond the current level of lithium-ion batteries. The advances are in lithium-air storage, which uses a porous carbon electrode in place of a heavy solid electrode in the battery. Oxygen from the air reacts with the lithium metal in the battery to store and discharge energy. The very open structure makes it possible to obtain such high levels of performance.

One of the biggest issues in battery development is the weight of the batteries. Whether for portable electronic devices or for hybrid and electric vehicles, the weight of the batteries is a factor that must be considered. Replacing the solid electrode with the lightweight carbon matrix has led to some of the highest levels of energy stored per pound of battery.

New methods of producing the carbon matrix for the battery creates a "carpet-like" material that is more than 90 percent open, which makes for a very lightweight battery. "These carpet-like arrays provide a highly conductive, low-density scaffold for energy storage," according to one of the researchers.

As an additional benefit, the researchers have found that the very open and regular nature of the battery allows scrutiny of its internal workings with a scanning electron microscope. Not only does this allow more research on the particulars of this battery, but it may also help with general research and understanding of why batteries have limited numbers of charge-discharge cycles before they cease being useful.

via: MIT press release