EDITOR: | May 20th, 2015 | 8 Comments

Nixon on ‘Electric Dreams’ and Moore’s Law for Batteries

| May 20, 2015 | 8 Comments
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electric-carThere is no Moore’s law for batteries – so says Dr. Fred Schlachter of the American Physical Society, Washington, DC and he’s right.

If I’d read Fred’s paper before I started looking closely at battery technology I might have never discovered that there actually is a Moore’s law at work here.

Hold on, I hear you say, you can’t both be right.

Bear with me…

I was writing a book on the future of transport fuels [1] and looking at how batteries and conventional fuels compare. Surprisingly this was not an easy question to answer with a standard Google search. Questions for which there is no immediate answer invite my curiosity, this indicates there is something interesting to be discovered.

I had to go deep into the literature to uncover reliable data on battery energy density trends over the past 100 years [2]. When I plotted a graph of energy density over time, an exponential line rather like Moore’s law appeared.

It seems that the amount of energy a battery can store is doubling every 22 years. The big rises in performance are driven by a change in the underlying technology, starting with lead-acid batteries 100 years ago to the current high performing Lithium ion batteries we use today.

So how can we both be right? It turns out that Fred and I are looking at battery technology over different timescales. Looking at a short timescale produces a view within one technology, which tends to be linear. Looking at a longer timescale shows the performance leaps with different technologies that create the exponential rise.

Both of us have come to the same conclusion though. However you look at battery technology, it will be some time yet before we see the small containers of energy that will power the electric cars of the future for the same distance as conventional fuels such as gasoline and diesel.

“So what?” I hear you say

I do admire electric cars; companies such as Tesla make extraordinarily desirable machines. There is even a world motorsport championship called Formula-e to race state of the art machines. And yet all electric cars have an Achilles heel. They can only go so far before they need a recharge, it is called range anxiety. This is why the rules of Formula-e state that the drivers can change cars during the race.

Engineers have worked hard to address range anxiety and can now claim 300 – 500 km on one battery charge. Impressive.

Yet when I look at a European mid range diesel car, one tank of fuel could take me over 1200 km before I need to refuel. Cars need to carry their fuel around with them so the amount of power you can pack into a given volume is important. A measure of this is called the energy density of the fuel, the bigger the number the further you can travel before refuelling.

As we have seen, the best battery technology is based on Lithium-ion designs. These have an energy density of approximately 0.8MJ/kg. This compares with an energy density for diesel of 46.2MJ/kg. This context makes the battery development trend less impressive now.

Graphene is currently in the news as a new wonder material for battery and super-capacitor energy storage technology.  Graphene may well prove to be a leap forward. However bear in mind the scale of the challenge: Even though battery energy density is doubling every 22 years – at this rate of development it will take over 100 years to reach the equivalent energy density of diesel.

Much as I admire the developments in electric cars, dear reader, be mindful that they will have to carry rather large and heavy battery packs around for some time to come. The next time you hear claims of dramatic improvements in battery technology, just remember that conventional fuels will take some beating because Moore’s law for batteries operates on a much longer timescale than computers.

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[1] Nixon, Adrian. Diesal? and other future transport fuels. 1st ed. Halifax, UK: Nixor Limited, 2013.
[2] Chen-Xi Zu and Hong Li. (2011) Thermodynamic analysis on energy densities of batteries. doi: 10.1039/C0EE00777C


Editor:

Adrian Nixon began his career as a scientist and is a Chartered Chemist and Member of the Royal Society of Chemistry. As a scientist and ... <Read more about Adrian Nixon>


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Comments

  • Chris Donaghue

    Adrian this is an illuminating article. I previewed your transportation fuel ebook on Amazon, and I was wondering what I would find in there about biodiesel? Biodiesel is the only thing that can detoxify petroleum, at 20%. It can be mixed at any ratio with any liquid petroleum except gasoline, but it can clean up gasoline spills. It’s being mandated all over the world. Diesel fuel in Canada is 2% biodiesel. But it needs to get up to at least 5%. It is such a superior fuel that the cetane index is so much higher that the effects are compounding and exponential. 5% biodiesel lowers GHG’s by 17%, and increases lubricity by 20%. It carries more than its own weight. And it is the only thing that can detoxify petroleum, and has nothing in common with ethanol.

    May 20, 2015 - 2:58 PM

  • Adrian Nixon

    Chris, Glad you found the article interesting. You make some insightful points about biodiesel. I do say a lot more about this in the book.
    When I researched Biodiesel I found that some of the ethics and sustainability of the fuel disturbed me. You’ll be familiar with the concerns about displacing food crops to grow fuel crops when people are starving in the world. So I looked for people who are making diesel and gasoline by alternative methods. Microbial production of diesel seems to be the most sustainable emerging technology. So I coined the term ‘Diesal’ to describe fuels made by this alternative microbial route. I’ll explore this in a future column entry if that would be of further interest. Thanks for the comment – and let me know if I’ve answered your question properly too. Adrian

    May 20, 2015 - 4:04 PM

  • Chris Donaghue

    I agree that taking food off the table is a concern, but it doesn’t need to be the case. By microbial I am guessing you mean bacterial algae? I want to see this realised.That it isn’t ready is why I don’t work in biodiesel anymore, but expect some articles on that by me in the near future.

    May 20, 2015 - 4:28 PM

  • Dr. Fred Schlachter

    Thanks for mentioning my opinion piece from April 2013 Proceedings of the National Academy of Sciences, the title of which is “No Moore’s Law for Batteries.” The Editors removed the quotes I had placed around “Moore’s Law'” This “law” is an empirical finding which has become a self-fulfilling prophecy, rather than a law of nature, such as the Second Law of Thermodynamics.

    Let me remind the reader that “Moore’s Law” behavior is exponential, evidenced by a straight line on a semi-log plot, or, in popular vernacular, doubling over many time periods with the same time period for each doubling (as, for example, doubling every two years for the past forty years). Simply doubling over some time period is NOT exponential, it is simply doubling. Doubling over several time periods (the same time period in each period) is required to demonstrate exponential behavior. At least four or five time periods are necessary, not just one or two.

    As I made clear in my article, the exponential increase of computer power over a long period of time is due to advances in lithography and technology, and has no fundamental meaning, nor is an exponential increase to be expected in any other area of technology. In fact, ongoing improvements in processors will slow and eventually stop as feature sizes approach atomic dimensions, if heat dissipation does not stop improvement before that limit is reached.

    There is absolutely no reason to expect the specific energy of batteries to increase in any regular fashion. Indeed, most improvement in battery performance has come about from changing chemistry rather than from ongoing improvement within a given chemistry, which has been incremental. I believe this is the “different time scales” referred to by the author. There has been improvement in battery specific energy from lead-acid through nickel-metal-hydride to the present leader, lithium-ion chemistry. Improvement, however, has been far from “doubling every 22 years.” The first sentence of the reference provided by the author, Zu and Li (2011), is as follows: “The average increase in the rate of the energy density of secondary batteries has been about 3% in the past 60 years.” This statement indicates that the specific energy of batteries has not quite doubled in the past 60 years.

    A recent EPRI report [Arshad Mansoor, EPRI, January 1, 2013] shows specific energy data from 1860 through the present, over five battery technologies. This report shows a doubling of specific energy over a 60-year period, roughly consistent with Zu and Li. This is far indeed from doubling many time periods of 22 years.

    I leave it to the author to show data with specific energy doubling over several 22-year periods, which would indicate exponential growth (a “Moore’s Law” behavior). I maintain my view that there is no multi-period doubling of the specific energy of batteries, which would indicate exponential growth.

    I suggest that particular care be used in citing Zu and Li. Figure 1 shows development of primary batteries (batteries which are not rechargeable), thus not relevant to transportation or many other applications. Figure 2 shows development of secondary (rechargeable) batteries, but includes data for Na/S and other batteries which are far from ready for use in the real world, as there are major issues to their implementation. Thus the most reliable quote from the paper is in the abstract: “The average increase in the rate of the energy density of secondary batteries has been about 3% in the past 60 years.”

    Given the need to show at least 4 or 5 periods of improvement in specific energy density, and taking 60 years as an approximate doubling time (the real doubling time is greater than 60 years), something like 240-300 years of doubling every 60 years would be required to show exponential growth. This is longer than the time since the first useful battery, lead-acid, was first invented.

    Thus there is no evidence at all that there is a “Moore’s Law” for batteries, as I stated in my 2013 paper, over any time period since practical batteries were first invented.

    May 22, 2015 - 12:06 AM

  • alvarita

    Moore’s Law has generally been understood to be a doubling of semiconductor component density every two years, and was only meant to apply to like devices. Moore’s original estimate was a two-fold increase every year which he revised some ten years later. Dr. Schlachter is quite correct pointing out that a physical limit is being approached that will likely render Moore’s Law a subject of historical conversation. The point is that Moore’s Law was not intended to be a universal law and it certainly does not apply to batteries in any way, shape, or form. If it did, we would be able to power an aircraft carrier for a few days with an iPad sized battery that is recharged by solar cells the size of an umbrella, assuming solar cell development also adhered to Moore’s Law, which it didn’t and doesn’t. Now, don’t let the Tesla battery junkies get wind of this thread…a whole bunch of them have been counting on Moore’s Law to make them rich and green, and who would want to spoil their party?

    May 22, 2015 - 1:25 AM

  • Tracy Weslosky

    Good morning Dr. Fred Schlachter –

    It is with great pleasure that we have had you comment on InvestorIntel, and this is to let you know that we have noticed — thank you.

    In lieu of your commentary, I have asked Adrian to respond via another column. And I quite look forward to Adrian’s response…

    Thanks again for visiting.

    May 22, 2015 - 9:53 AM

  • Nixon and Dr. Schlachter Debate: “No Moore’s Law for Batteries” | InvestorIntel

    […] last column published earlier this week titled Electric Dreams’ and Moore’s Law for Batteries, I would like to start by thanking Dr. Fred Schlachter for making time to comment in detail on my […]

    May 22, 2015 - 4:34 PM

  • Tracy Weslosky

    We have continued this debate on a 2nd column titled: Nixon and Dr. Schlachter on the “No Moore’s Law for Batteries” debate. http://bit.ly/1FINiNP

    May 22, 2015 - 4:37 PM

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