Moore's Law for batteries: No dice

The REVAi/G-Wiz i electric car charging at an on-street station in London (Image: Wikipedia Commons)

Ever since Gordon Moore came up with the ubiquitous law bearing his name, it has been applied to paradigms far beyond those which it was intended for. This is perhaps not surprising; the history of science and technology - and of religion - has consistently demonstrated that the followers of a prophet usually extend his principles into domains which the prophet never really approved of.

Transistor technology does neatly seem to follow the Moore's Law curve and a few other cutting-edge technologies like genome sequencing also seem to do this. Yet Moore's proselytizers have extended his law to pretty much everything. The law especially seems to break down when applied to biomedical research; for instance a review from last year pointed out how the pace of drug development almost seems to have been following a reverse law, titled "Eroom's Law" of declining productivity. Kurzweilian prognostications notwithstanding, research in neuroscience might follow the same trajectory, with a burst of rapid mapping of neuronal connectivity followed by a long, fallow period in which we struggle to duplicate these processes by artificial means.

The basic reasons why an emerging technology may not follow Moore's Law is either because we tend to underestimate the complexity of the system to which the technology is applied, or we underestimate the basic principles of physics and chemistry which would inherently constrain a Moore-type breakthrough in that field. In case of medical research both these constraints seem to rear their ugly, emergent heads, and this is the main problem I have with futurists like Ray Kurzweil who seem to imagine an entire universe governed by Moore's Law-type exponential progress in every field. Not all levels of complexity are created equal, and we just don't have enough evidence to know how general Moore's Law (which I think should simply be re-named "Moore's Observation") is in the world of practical problem-solving.

The argument about basic science limitations may especially apply to much-touted battery research whose proponents often seem to declare the next breakthrough in battery technology as being just around the corner. But a perspective from Fred Schlachter from the American Physical Society in the Proceedings of the National Academy of Sciences puts a brake on these optimistic predictions. His point is simple: any kind of Moore's Law for batteries may be limited by the fundamental chemistry inherent in a battery's workings. This is unlike transistors, where finer lithography techniques have essentially enabled a repetitive application of miniaturization over the years.

There is no Moore’s Law for batteries. The reason there is a Moore’s Law for computer processors is that electrons are small and they do not take up space on a chip. Chip performance is limited by the lithography technology used to fabricate the chips; as lithography improves ever smaller features can be made on processors. Batteries are not like this. Ions, which transfer charge in batteries are large, and they take up space, as do anodes, cathodes, and electrolytes. A D-cell battery stores more energy than an AA-cell. Potentials in a battery are dictated by the relevant chemical reactions, thus limiting eventual battery performance. Significant improvement in battery capacity can only be made by changing to a different chemistry.

And even this different chemistry is going to be governed by fundamental parameters like the sizes of ions and the rates of chemical reactions and current flow. Schlachter goes on to note the problems that lithium batteries have recently encountered, including fires. There is thus no guarantee that there will be a breakthrough in battery technology that's equivalent to that in computer technology over the last thirty years. And the article is right that while we are waiting for such breakthroughs, it's a really good idea to push forward with improving energy efficiency in cars, making their lighter, smaller and and more powerful. Energy efficiency would not ultimately solve pollution problems since the cars would still be fueled by gasoline, but it would certainly take us a long way while we are waiting for the next battery breakthrough engineered by Moore's Law. A law which may not really hold when it comes to next generation electric technology.

First published on the Scientific American Blog Network.