Liquid Metal Battery: The Next Generation Permanent Battery

Intermittency may not be the most serious problem in renewable energy, but we could perhaps consider it as the most “nagging”. Even if we could more or less calculate the average amount of energy that renewable sources could generate, we could never manipulate it in a way that we would always have the right amount of energy when we need it. That is why we always rely on battery banks for load balancing and energy regulation.

And even if we have lead-acid batteries to store the energy that they generate, the batteries just don’t have the energy density that we need to completely eliminate the energy production problem that is usually easier to deal with economically (for now) using conventional non-renewables.

Would there be any new type of battery that could fit exactly with our energy needs then? Is there any battery that has a high energy density, but can last longer and could be made a lot cheaper? Apparently there is, and this technology could forever change our view on how powerful and long-lasting batteries could truly be.

The Battery that Can Repeat Charge Cycles Forever

Liquid metal batteries, as its name suggests, are batteries that uses liquid metal as electrodes. The metals used for the anode and cathode are of different kinds, with the salt mixture sitting right between. Unlike regular batteries, liquid metal batteries operate at a higher temperature to keep the metals in their liquid state. The technology uses a method that is fundamentally similar to the process of smelting aluminum (Hall–Héroult process).

One notable advantage of liquid metal batteries over conventional batteries is that it is potentially capable of eliminating intermittency through reliable sustainability. The theoretical energy output efficiency of a liquid metal battery is rated at 80%-90%, and is considerably more energy dense that some of the batteries that we commonly use today. The heat needed to make it operational can be initially supplied by the “recharging” source, which would then be sustained by the system independently as it produces energy.

The chemical reactions during the charge/discharge process in a liquid metal battery are completely 100% reversible. This means that liquid metal batteries can potentially keep on working as long as the structural integrity of the battery allows it to.

Samples Liquid Metal Batteries

The choice for the salt and metal to be used is actually not too narrow, as there are many independent types of liquid metal batteries that are very different from each other. It should be noted however, that the electrodes and electrolytes should have carefully graded densities, so that one floats on top of the other (for a very inexpensive assembly process).

• Sodium-Sulfur Battery – this is first known type of liquid metal battery. It is also commonly known as the NaS battery, and it was developed for large-scale non-mobile applications. The configuration for this type of liquid battery uses a solid electrolyte between the sodium and the sulfur electrodes. Because of its relative efficiency, there have been proposals to use and install it on space stations. The Space Shuttle mission STS-87 carried a test battery and was able to confirm its efficiency for space use. The largest known sodium-sulfur battery today is at Presidio, Texas. It is as large as a standard home, and provides 4 megawatts of backup energy for the entire town.
• Antimony-Magnesium Battery – it is a newer type of liquid metal battery that was based on what could be the best elemental combination for metals and salts. It was designed and invented by Donald Sadoway, a professor at MIT who is one of best supporters of liquid metal battery technology. Unlike the NaS battery, this uses a molten salt between the two liquid metal electrolytes. The first test battery of this type was a small 1 kilowatt-hour battery that is about the size of three D batteries. The design of this liquid metal battery type is made to be easily scalable, with the farthest end of the scale being a 2 megawatt-hour intermodal container-sized battery that can be used to meet the daily energy demands of 200 regular households.

Would liquid metal battery technology go in direct competition with metal-air batteries someday? Unlikely perhaps. We have to remember that liquid metal batteries are never designed for mobile uses. They are best suited for non-mobile grid power applications, for example as a permanent replacement for lead-acid battery banks of renewable energy systems.

Photo credit: Some rights reserved by p.Gordon via Flickr

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Christian Crisostomo (250 Posts)

Christian Crisostomo is just your average tech geek that loves to see man's newest and most recent technological exploits. He holds great interest in the potentials of green technology, and is enthusiastic about the continuous development of environment-friendly alternative energy.

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