Energy companies testing "liquid air" as a means of storing backup electricity

Highview Power Storage, a British company that develops energy storage systems for utility companies has received $18 million in funding from several backers to investigate the use of "liquid air" as a means of storing electricity for backup purposes. Liquid air is air that has been chilled to the point of liquefying—when warmed it expands, allowing for the possibility of driving turbines to create electricity.

One of the main problems with most renewable energy sources is that they can't produce electricity all the time—only when the wind is blowing, for example, or when the sun is shining. Because of that, developers have created energy backup systems. Such systems can store excess electricity for use when the primary source is unavailable. Most current systems rely on batteries, which work very well, but can become costly in the long term. Highview Power Storage is looking at using electricity from the grid to cool air till it liquefies, then storing it in huge tanks until it is needed.

The process is both simple and inexpensive. Air is pulled in from the environment, cleaned to remove C02 and water vapor (both freeze to a solid) and then chilled to -310F (-190C). The liquid is then stored in vacuum sealed tanks. When the need arises, the liquid is exposed to warm air, causing it to expand and in so doing, drives a turbine that creates electricity. The whole process has been found to be approximately 50 to 60 percent efficient, which means heating the liquid air creates just over half as much electricity as was used to chill and store it. That's not very good compared to batteries, of course, which are typically 90 percent efficient, but liquid air has other benefits. Foremost among them is that liquid air can store power for decades, while batteries need to be replaced periodically. Storing air is obviously a lot cleaner as well.

Highview Power Storage isn't the only company testing liquid air as a power source—Berkeley California based LightSail announced recently that it had raised $37 million to study the use of liquid air as a means of storing electricity. SustainX, based in New Hampshire also recently announced it had raised $20 million to do the same. In related news, engineering giant Ricardo is currently testing the possibility of using liquid air to power automobiles, though they remove the oxygen, leaving just liquid nitrogen.

View the original article here

Bacteria use hydrogen, carbon dioxide to produce electricity

Researchers have engineered a strain of electricity-producing bacteria that can grow using hydrogen gas as its sole electron donor and carbon dioxide as its sole source of carbon. Researchers at the University of Massachusetts, Amherst report their findings at the 113th General Meeting of the American Society for Microbiology.

"This represents the first result of current production solely on hydrogen," says Amit Kumar, a researcher on the study who, along with his co-authors are part of the Lovley Lab Group at the university.

Under the leadership of Derek Lovley the lab group has been studying Geobacter bacteria since Lovley first isolated Geobacter metallireducens in sand sediment from the Potomac River in 1987. Geobacter species are of interest because of their bioremediation, bioenergy potential, novel electron transfer capabilities, the ability to transfer electrons outside the cell and transport these electrons over long distances via conductive filaments known as microbial nanowires.

Kumar and his colleagues studied a relative of G. metallireducens called Geobacter sulfurreducens, which has the ability to produce electricity by reducing organic carbon compounds with a graphite electrode like iron oxide or gold to serve as the sole electron acceptor. They genetically engineered a strain of the bacteria that did not need organic carbon to grow in a microbial fuel cell.

"The adapted strain readily produced electrical current in microbial fuel cells with hydrogen gas as the sole electron donor and no organic carbon source," says Kumar, who notes that when the hydrogen supply to the microbial fuel cell was intermittently stopped electrical current dropped significantly and cells attached to the electrodes did not generate any significant current.

View the original article here

Green conversion of heat to electricity

Soon, it will be possible to produce electricity from heat over 30 degrees emitted from a waste incinerator, refinery, or data processor. The start-up Osmoblue has just confirmed the feasibility of this new concept.

A large proportion of the energy consumed – between 20% to 50%, according to some studies – is dispersed as heat. Although it is already possible to recycle heat at temperatures over 150 degrees to produce electricity or to heat homes, the rest is simply released into the environment. At a time when companies are forced to be concerned with their environmental impact, this deficiency must be remedied. The start-up OsmoBlue, based in EPFL's Laboratory of Microsystems, developed a process based on the principle of osmosis to convert heat over 30 degrees into electricity.

Osmosis is a natural phenomenon that occurs when the concentration between two solutions separated by a membrane differs, for example between saltwater and freshwater. A stream flows from the less concentrated to the more concentrated solution, which tends to balance the concentrations on each side of the membrane. The mechanical energy of this stream may be converted into electrical energy by a turbine and an alternator. Heat is again used to separate the fluid into two separate solutions, one of which is more concentrated than the other. It is, therefore, a closed circuit (see image) that does not consume water. Though this concept has attracted significant investment, it has struggled to become a reality due to low yields.

The OsmoBlue technology is advantageous because it can be implemented with any heat source: air, water, gas, etc. The efficiency of the machine is both dependent on temperature and the nature of the hot and cold sources (air, water, gas, or steam). Connected on one side to the heat source and the other to the power grid, modular systems could eventually be installed in existing structures, near the company's cooling system.

With a team of seven people, the young entrepreneur has completed a digital laboratory demonstrator and a digital model for evaluating the performance of the product. "For example, it allowed us to estimate that 10 megawatts of heat could produce between 100 and 600 kilowatts of electricity, the consumption of one hundred homes."

It was during a postdoctoral fellowship at Harvard University in the United States that Elodie Dahan had the idea to revisit the method of osmosis. Components have been revised in light of recent advances in materials engineering and microtechnology. A first prototype is currently being manufactured at EPFL. A pilot unit on a larger scale could then be installed in a regional waste incineration company in 2014.

View the original article here