MIT: Liquid Batteries Have Huge Potential

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“Professor Donald Sadoway and Materials Processing Center Research Affiliate David Bradwell observe one of their small test batteries in the lab. The battery itself is inside the heavily insulated metal cylinder at center, which heats it to 700 degrees Celsius.” (Photo: Patrick Gillooly; Source: MIT)

According to new research conducted by the Massachusetts Institute of Technology and published in the Journal of the American Chemical Society, renewable sources of energy such as the sun and wind could become economically competitive with traditional sources of energy via the use of “liquid batteries.”

While MIT has made many announcements in the past of inventions of that could potentially be cheaper than traditional energy storage systems such as the lithium-ion or lead-acid batteries in use today, this is perhaps the most promising I have seen.

Wind & Solar Intermittency, & Solutions Up Until Now

The sun does not always shine, the wind does not always blow, wind speeds fluctuate, and the amount of sunlight we receive varies due to clouds. Thus, the power we can generate from wind and solar energy fluctuates.

According to the United States Department of Energy 2011 Annual Energy Outlook, the average cost of wind power in the U.S is only 9.7 cents per kWh (kilowatt-hour) of electricity. Wind power’s problem is no longer the cost to generate it. It is now mainly intermittency.

Fluctuations in the amount of power generated by a wind farm can be compensated for by adjusting other hydroelectric, nuclear, or fossil-fueled natural gas or coal power plants. If a wind farm generates more than necessary, other power plants can be turned down to compensate for that, and back up again when there is less than enough wind power available. The ability of nuclear and coal power plants to adjust is very limited, however, because they take long to make major adjustments in power production.

Energy storage, on the other hand, enables wind farms to independently supply power without the help of other power plants. Battery banks are a form of energy storage system that can achieve this, but they have traditionally been too expensive to compete.

MIT’s Liquid Batteries

According to MIT, liquid batteries are inexpensive and last longer than traditional batteries. The three materials contained in the liquid batteries each settle in separate layers due to the difference in their densities, which, in this case, is a good thing. They need to be separate.

This project was conducted with the importance of material availability and abundance in mind. “We explored many chemistries,” Donald Sadoway, the John F. Elliott Professor of Materials Chemistry at MIT and the senior author of the new paper, says. All three layers of the materials used are abundant and inexpensive.

The combination published in the new paper: The negative electrode (anode) is in the top layer and is made of magnesium; the middle layer, the electrolyte, consists of a salt mixture containing magnesium chloride; and the bottom layer, which is the positive electrode (cathode), is made of antimony.

This battery operates at a temperature of 700 °C, which is 1,292 °F.

Discharging: The battery generates an electric current as each magnesium atom (this is in the negative electrode) loses two electrons, then becoming magnesium ions which travel to the other antimony electrode. The magnesium ions then reacquire two more electrons and become magnesium again because of this. This causes an alloy to form with the antimony.

Charging: When the battery is supplied with an electric current, this process is reversed and the electrons are driven out of the antimony electrode, and back to the magnesium electrode.

As I often emphasize: batteries do not actually store electricity, they generate it. When you charge a battery,  you supply it with an electric current that drives a chemical reaction of which the one mentioned above is an example.  You reverse that process to make the battery generate electricity.

This looks like an exciting new development. What do you think?

Source: MIT News Office

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Nicholas Brown

Has a keen interest in physics-intensive topics such as electricity generation, refrigeration and air conditioning technology, energy storage, and geography. His website is:

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