Why energy storage is really superficial

If you want to improve the performance of batteries and capacitors, one sure-fire way is to increase charge density. And the way to do this is to up-scale the surface area of your electrodes. Various configurations of carbon, both alone and in combination with other elements, can provide that increase, which is why we have reported on everything from nanoflowers to a carbon nanofoam.

The latest news in the battle for increased surface area comes from Rice University, where scientists have seamlessly combined carbon nanotubes a few atoms wide and 120 microns long onto one-atom thick graphene sheets, reports Science Daily. That means that if the nanotubes were the same width as an average house, they would rise up from the graphene ‘ground’ like mega-skyscrapers… into space.

As you can imagine, that’s a lot of surface area: 2,000 square metres per gramme of material, in fact. But what about practical applications? Researchers at Rice say their tests indicate the material already performs as well as the best carbon super-capacitors.

San Diego zoo debuts energy storage

It converts sunlight into energy, charges electric vehicles and delivers access power to the grid. And it keeps your car cool while you go feed the elephants. The newly unveiled parking lot at San Diego zoo has solar canopies that can produce up to 90kW of electricity, five car-charging stations and the possibility to deliver energy to the grid. Best of all, it has two lithium-polymer storage units, with a total capacity of 100kW.

According to an article on the KPBS site, the energy storage element is a first for this type of project. And the installation has so impressed the University of California in San Diego that it is considering building a similar power hub on campus.

New solar storage possibilities from MIT

Scientists at the prestigious Massachusetts Institute of Technology (MIT) have produced modified carbon nanotubes that can store solar energy indefinitely after being charged up by sunlight, says the university.

Although nano materials that store sunlight in chemical bonds have been produced before, researchers on this project say that the new material, which is made using carbon nanotubes in combination with a compound called azobenzene, has a much higher energy density than earlier solutions. In fact the energy density of this solutions is comparable to that of lithium-ion batteries.

Researchers trust rust for energy storage

An integrated solar cell that produces hydrogen as a form of energy storage is being investigated by researchers at the Ecole Polytechnique Fédérale de Lausanne (EPFL), in Switzerland. Converting solar to hydrogen is hardly a new idea, but so far solutions to the problem have been very costly. The EPFL system sidesteps this problem by using iron oxide, better known as rust, and water.

Of course, this is not common-or-garden rust but ‘nanostructured rust’: enhanced with silicon oxide and covered with a nanometer-thin layer of aluminum oxide and cobalt oxide. But it is still cheap to produce, say scientists at EPFL. The one drawback is low efficiency. At 1.4% to 3.6%, the prototype is not going into production anytime soon.

However, researchers are confident they can attain efficiencies of 10% in a few years, for less than USD$80 per square metre.

Electric vehicles for military energy storage

Southwest Research Institute is a member of a team recently awarded a $7 million contract from the US Army Corps of Engineers to demonstrate the use of electric vehicles plus generators and solar arrays to supply emergency power. The program, called the Smart Power Infrastructure Demonstration for Energy Reliability and Security, is intended to make military installations more energy efficient and secure.

Perfect battery exists at subatomic level

A battery with almost 100% efficiency is currently impossible… but only because today’s technology is way too big, say two European theoretical physicists. Robert Alicki, of the University of Gdansk in Poland, and Mark Fannes, of the University of Leuven in Belgium, are thinking very small indeed, by defining a battery that stores and releases energy using quantum mechanics, operating on a subatomic scale. The technology that would exploit their model, reported in Extreme Tech, may be decades away.

But it is claimed such quantum batteries might power the tiniest of devices and when used en mass, provide power storage that is much more efficient than current lithium-ion batteries.

Concrete steps forward in thermal energy storage

It is cheaper than molten salt and causes less damage to heat tank walls than packed rocks, say engineering researchers at the University of Arkansas, who have developed concrete layers as a means of capturing heat from solar energy. Phys.org reports that the concrete plates conduct heat with an efficiency of 93.9%.

Although this is slightly less efficient than the packed rock method, the specially developed concrete avoids the stress caused to tank walls because of the expansion and contraction of storage tanks during thermal cycling. In addition, energy storage using the new technique costs only USD$0.78 per kilowatt-hour, far below the US Department of Energy’s benchmark figure of $15 per kilowatt-hour.