Batteries, Energy Storage, and Its Impact

By Gusten Soeprapto

Energy storage is a broad phrase, for the purposes of this essay we will consider energy storage that which can be hold and/or release electricity indirectly or directly on demand.

The first thing you might think of when seeing the phrase energy storage is the common AAA battery which is the standard size for what are called Dry Cell batteries which also includes the D, C, AA, and AAAA battery sizes. A dry cell battery is essentially a device that has an electrolyte immobilized as a paste which has just enough moisture to allow electrons to flow, as opposed to a Wet Cell which contains a liquid commonly lead-acid. Dry cells nowadays usually are alkaline batteries, to refresh an alkaline is anything with equal or higher pH than water, so an alkaline battery is a battery which uses an alkaline as an electrolyte such as Potassium-Hydroxide (KOH) along with Zinc (Zn) and Manganese-Dioxide (MnO2) to create a reaction. These batteries for the most part are discardable and thus are known as ‘Primary cells’ as opposed to rechargeable ‘secondary cells’. Alkaline D, C, AA, AAA, and AAAA Dry cell batteries all share a voltage of 1.5 Volts. In the cases mentioned the battery on the atomic-scale works by removing the 2 electrons from the zinc atom’s outermost orbit.

Moving on, the second thing you might have thought of when seeing the phrase energy storage would be the lithium-ion battery which is a secondary cell battery. The first secondary cell battery was the aforementioned Wet Cell lead-acid battery though they have come out of favour in recent times, just by the name you can infer why. The lithium-ion battery is the secondary cell that is most commonly used nowadays and for good reason, it has a good specific energy density for a battery (100-265 Watt-Hour/Kg or 360000- 954000 J/Kg), it has a relatively high voltage (3.6 Volts), and the “Memory Effect” phenomena where a battery loses its energy capacity if it is recharged after being partially discharged is not present so pulling and plugging the charger repeatedly won't have much negative effect. Unsurprisingly lithium-ion batteries use Lithium Ions! Lithium atoms get rid of the lone electron on its outermost orbit thus giving a positive charge to the lithium atom.

With all that said batteries cannot store that much energy, a li-ion battery for example as previously mentioned has a specific energy of 360000- 954000 Joules/Kilogram though that sounds like a lot, compared to say gasoline which has a specific energy of 4600000 J/Kg and the fact that a microwave oven runs on 1200 watts meaning that the 1kg li-ion battery could be depleted in 5 - 13.25 Minutes in the end it really isn’t much. But so far we’ve only talked about chemical solutions, but are they really enough? Can large lithium-ion battery installations hold the power of upcoming developments in renewable energy. Energy storage methods for renewables are semi-mandatory as there will be days that are cloudy or when the wind won’t come. So far, we’ve only discussed chemical solutions but here is the nuclear option.

The Radioisotope Thermoelectric Generator (RTG) would not fit in the normal conception of what is called a battery but in function it is considered a type of nuclear battery. The RTG cannot receive energy directly but it is a portable steady way of outputting power, it will continually output energy until its radioactivity ceases or halves, which can be decades, centuries, or months. RTGs consist of an isotope which generates heat surrounded by components which take advantage of the thermoelectric effect to convert the heat into electricity. RTGs were used in various Soviet lighthouses and are still in use in spacecrafts/satellites. Unsurprisingly the most effective isotope (Polonium-210) is also the most radioactive, though since it’s alpha radiation it can be held, just not consumed, 1 gram if perfectly distributed could kill 50 million people; it’s also immensely hot at 500C constantly. It has a power output of 140 Watts/Gram and a Half-Life of 138.376 days which a simple calculation would yield that it would have a total energy until it halves of 1673796096000 (or 1.7 trillion) Joules/Kilogram, keep in mind that heat/radiation capturing methods do not have perfect efficiency though. Soviet Lighthouse RTG’s voltage can range from 7-30 Volts.

That total energy number sounds ludicrous though it is in-line with other nuclear phenomena such as fission which is used in atomic bombs do it more swiftly (Many billions of times more swiftly).

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[For a more technical look, let’s take a more familiar isotope: Plutonium-239, 1 mole of plutonium is 244 grams, 1000 grams/244 grams so 1 kg of Plutonium239 is 4.0983606557377049180327868852459 moles. The fission of a single plutonium atom is 3.3181077e-11 Joules, 4.0983606557377049180327868852459(6.022e+23) * 3.3181077e-11 is 81891985940164 Joules. 1 kg of Plutonium-238(The isotope used in RTG) releases 570 W/Kg and a half-life of 87.7 years so it has a total energy until it halves of 1576453104000 Joules, so dividing the two yields that decay is 50x weaker than fission, why this is I honestly don’t know]

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Now the glaring issue is that the RTG are primary batteries like the aforementioned chemical dry batteries. Are there any nuclear secondary batteries? No such thing exists, not realistically, though there are devices that can turn energy into antimatter at hyper-low efficiency and even then, antimatter can hardly be contained [Calculating from some claims it can be as low as 0.0000000008% though no source has been given]

Going back to more conventional methods a very old method could be used for energy storage, the flywheel. Flywheel batteries are one of the mechanical ways of storing energy, in old times they span in the air at a spinning rate of 5000 RPM but in the modern day of course they are made to spin in a vacuum or something close to that at around 60000 RPM or 1000 spins a second. Flywheels have a good efficiency of energy out to energy in of up to 90%. Again, using battery terminology they are considered secondary batteries as they can consistently receive and output energy repeatedly. Their specific energy can range from 360000 – 500000 J/Kg, which is slightly less than the Lithium-Ion battery and much less than the Radioisotope Thermoelectric Generator but it is still higher than a Wet Cell Battery say a Lead-Acid battery (which has a specific energy of 108000-180000 J/Kg) or any of the various Dry-Cell batteries. Flywheels are sturdy, they do not break easily as they are mechanical and that is their main advantage. Flywheel batteries are used in locomotives, rail vehicles, and some NASA prototypes.

The last energy storage method which will be mentioned is Pumped Hydroelectric Energy Storage or PHES/PHS for short, it is currently the largest form of grid energy storage or large-scale energy storage available. PHS is a local way of storing energy in the form of gravitational potential energy for hydroelectric energy generation methods or dams in less fancy language. PHES has an energy efficiency of around 80% so only a fifth is of the surplus energy is lost.

The impact of good energy storage would be incredible as currently if a surplus of energy is created there is no benefit. Dry Cell batteries would not be a good candidate for storing our energy as they cannot be recharged. Wet Cell batteries can be recharged but aren’t ideal as they can contain lead and sulfuric acid. Lithium-Ion is the quintessential modern battery as it has a higher specific energy that either dry or wet cell batteries, is a solid inside, and can be recharged, Li-Ion is used in modern energy storage installations paired with renewable energy productions. Radioisotope Thermoelectric Generators cannot be directly recharged, though you can use energy to make the isotope used in them they still aren’t ideal as there is no way to switch one off and radioactive materials can be greatly expensive, prohibited, and even highly dangerous in some cases but the upside is that it has absurdly high total energy though how fast it gives it out varies. Flywheel is rechargeable but even in a vacuum has less specific energy than Lithium-Ion, flywheels though are cheap, simple, and will likely be used in the future. Pumped Hydroelectric Energy Storage is in use and will likely continue use as there is no reason not to use it, the technique sadly cannot be expanded to other renewable or even non-renewable energy sources. Lithium-Ion appears to be the top-contender for global specifically renewable energy sources here, and that is not much of a surprise, though hopefully the other methods will be used in much more specialized areas

Good luck on the battery filled future!

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Sources [*P means presumably or from what I could gather]:

- Prof. Tom Stoebe [*P], University of Washington. “Materials Science Battery Case study”. 1998-2003[*P]. https://depts.washington.edu/matseed/batteries/MSE/index.html

- Klaus Schmidt-Rohr (2018). Journal of Chemical Education 2018 95 (10), 1801-1810. “How Batteries Store and Release Energy”. pubs.acs.org/doi/10.1021/acs.jchemed.8b00479

- Energizer Brands, LLC. “Alkaline Manganese Dioxide Handbook and Application Manual” https://data.energizer.com/pdfs/alkaline_appman.pdf

- University of Washington, Clean Energy Institute. “Lithium-Ion Battery” https://www.cei.washington.edu/education/science-of-solar/battery-technology/

- Panasonic (2010). “Batteries: OEM & Industrial”, Lithium-Ion [November 22, 2010 Archive] https://web.archive.org/web/20101122215008/http://www.panasonic.com/industrial/batteries-oem/oem/lithium-ion.aspx [Open the PDFs for the info]

- Argonne National Laboratory, EVS (August 2005). Human Health Fact Sheet, Polonium https://web.archive.org/web/20070630224919/http://www.ead.anl.gov/pub/doc/polonium.pdf [Archive from 2007 though dated August 2005]

- Anton Beck[*P], Epetech. Battery Cell Comparison. https://www.epectec.com/batteries/cell-comparison.html

- Ed Douglass, Douglas Electrical Components. Next-gen Of Flywheel Energy Storage. [Archive from 10 July 2010] https://web.archive.org/web/20100710052927/http://www.pddnet.com/article-next-gen-of-flywheel-energy-storage/

- Jonah G. Levine B.S., Michigan Technological University (November 27 2007). “PUMPED HYDROELECTRIC ENERGY STORAGE AND SPATIAL DIVERSITY OF WIND RESOURCES AS METHODS OF IMPROVING UTILIZATION OF RENEWABLE ENERGY SOURCES”. https://web.archive.org/web/20120913151458/https://www.colorado.edu/engineering/energystorage/files/MSThesis_JGLevine_final.pdf [Archive from 13 September 2012]

Plutonium section:

- Dennis Miotla (21 April 2008). Briefing for Nuclear Energy Advisory Committee. “Assessment of Plutonium-238 Production Alternatives”. https://energy.gov/sites/prod/files/NEGTN0NEAC_PU-238_042108.pdf

- M.G Sowerby, National Physics Laboratory. Table of Chemical & Physical constants. Nuclear fission and fusion, and neutron interactions. https://web.archive.org/web/20100305114800/http://www.kayelaby.npl.co.uk/atomic_and_nuclear_physics/4_7/4_7_1.html