The German company Stornetic attempts to enter the grid frequency regulation market using carbon fiber flywheel energy storage

I first read about mechanical flywheels as a means of electrical energy storage more than thirty years ago when I was in graduate school. The amount of progress in practical applications during the intervening three decades has not been impressive. Steel flywheels in vacuum chambers using magnetic levitation bearings have found a market niche in uninterruptible power supplies (UPS) where the flywheels supply 10 to 15 seconds of electrical energy during a power interruption, allowing time for some other backup source (e.g. a diesel gen set) to come on line.

Flywheels made out of carbon fiber are mechanically stronger than steel flywheels and thus can spin faster and store more energy (The energy stored is proportional to square of the angular speed) and can thus provide longer time periods of energy backup in a given physical foot print. However, carbon fiber flywheels are more expensive than steel flywheels. A company called Pentadyne introduced carbon fiber flywheels into the UPS market but ultimately declared bankruptcy. A company called Beacon Power introduced carbon fiber flywheels into the power grid frequency regulation market, but they subsequently joined Pentadyne in bankruptcy. Neither of these flywheel designs is completely dead since Pentadyne was acquired by Phillips Service Industries and Beacon Power was acquired by Rockland Capital LLC. However, the long term succes of both of these enterprises is still questionable.

A new entry into the field of carbon fiber flywheels for grid energy storage is a German company called Stornetic. Interestingly Stornetic is a spin off from a company called Enrichment Technology Company (ETC) whose core technological expertise is in high speed gas centrifuges used to produce enriched uranium fuel for nuclear reactors. Apparently ETC felt that their expertise in high speed rotating machinery was a good match with flywheel energy storage.

In this brochure Stornetic states that their basic flywheel unit can deliver 22kW of power and store 3.6kWh of energy. These numbers imply 10 minutes worth of energy storage at the maximum power rating which is much longer than the 10 to 15 seconds delivered by steel flywheels in UPS system. These kind of discharge times open up the application space of grid power frequency regulation if the cost is low enough. Whether or not ETC and Stornetic can deliver carbon fiber flywheel energy at significantly lower costs than has been achieved in the past remains to be seen.

Porous carbon films derived from carbide films allow integration of thin film supercapacitors into silicon micro-circuitry

The Drexel University nano-materials group together with a group of french researchers lead by Patrice Simon of Paul Sabatier university have recently published in Science a paper describing methods for thin film carbon supercapacitors into standard silicon based micro-circuitry. The carbon is deposited on top of a silicon substrate as a titanium carbide (TiC) film. After chlorination most of the TiC film is converted into a high surface areas porous carbon film which can be used to create a micro supercapacitor. The residual TiC act as a stress buffer with the underlying Si film. Regarded a energy storage devices supercapacitors have very high power density and very long cycle life (> 1 million). However, their energy density is more than an order of magnitude lower than lithium ion batteries.

The Drexel university announcement of these new ‘energy storage on a chip’ devices is quite enthusiastic about potential micro-electronics applications, but does not really describe the application space that is being targeted. I would be extremely surprised if the energy density is high enough to compete with lithium ion batteries, but there may be lower energy requirement applications that can use this technology. The article emphasizes the fact the the carbon films are flexible and can thus be integrated into flexible circuitry. Possibly wearable electronics is one the imagined applications for this new technology.

Australian company Tractile produces PV/Solar Thermal roof tiles for building integrated energy harvesting systems

The Australian company Tractile is another entrant in the solar PV / solar thermal integrated energy harvesting systems. They promise the usual advantages relative to PV only systems of shorter payback times and higher PV efficiency due to active cooling of the solar cells. They offer this advantage in the form of Solar PV / Solar thermal roofing tiles which can be integrated with non-energy harvesting tiles in a roofing installation. If you are putting on a new roof anyway the excess labor cost associated with adding solar energy harvesting will be lower than in the case of adding solar energy harvesting to an existing roof.