Good morning, and thanks to the organizers for inviting me to speak at this conference on science and energy. I have been assigned a broad topic, and I am going to speak broadly about it. As a physicist I care a lot about energy. It is a concept that weaves its way through the entire history of modern science, and ties together all the disciplines at every level of relevance to human affairs. Literally everything that happens in the universe requires energy to make it happen. The only other concept that comes close to having the same universal significance is information. Everyone here this morning knows that we are living through an extraordinary revolution in information technology. It is worth asking whether a comparable revolution in energy is about to occur, and whether there might be a link between current revolutionary science and a possible revolution in energy technology.

We ought to be clear about what is a revolution in science or technology, and this is somewhat a matter of opinion, especially when we are trying to decide whether we are living in one. The eminent science historian I. Bernard Cohen published a long treatise on this subject in 1985 and concluded that we really can only tell after the fact, but that some revolutions are more obvious than others. The current information revolution is obvious because it has transformed our way of life within a single generation. In science, the revolutionary quality of quantum mechanics and relativity were acknowledged almost immediately, and are manifest today in their ubiquitous influence on our understanding of nature. I would argue that what is revolutionary in today's science, at least that part related to energy, is not its content but its methods. Information technology has revolutionized how we retrieve data from experiments, how we communicate our ideas, how we work with colleagues, how we recruit and interact with students and mentors. It has even altered the mode and significance of work-related travel and conferences such as this one. Scholarship has not seen such a radical transformation since the introduction of the printing press in the 15th century.

It is partly because of rapidly advancing information technology that the instrumentation we use for science is also in a revolutionary phase. The ubiquitous inexpensive digital computing power that is driving the information revolution is linked to steady advances in instrumentation for imaging, analyzing and manipulating matter at very small scales – ultimately at the atomic level. This is new. The knowledge that things are made of atoms is not. We call the revolutionary fields "technologies" – biotechnology, nanotechnology, and "infotechnology." We do not call them sciences, which is appropriate. Not that the science from which these technologies spring is unimportant, but to state my point again, it is not the science that is revolutionary but the associated technologies to which it is linked. This distinction needs to be emphasized because exploiting science for societal objectives is a complex business whose different parts need to be managed consciously if they are to work productively together. Instrumentation like the Spallation Neutron Source here at Oak Ridge, and the x-ray light sources elsewhere, are essential ingredients of the recipe for innovations in energy technology, and they must be sustained together with the community of scientists and engineers working on specific applications. This is an important issue particularly in the United States where the funding of large scale instrumentation and the funding of research projects that require it are separated in different agencies and appropriated by different subcommittees within Congress.

I will come back to science, but our main interest is in revolutions affecting what we are calling our "energy challenges." So as not to leave you in suspense, I do not think we are living through an energy revolution right now comparable to the one in information technology, and I cannot envision a future change in energy technology as abrupt and transformational as the one in information technology during the past two decades. That is not to say energy technology is static, or that no exciting developments will occur. Three times during the past two centuries societies have been shaken – it is fashionable to use the word disrupted – by true revolutions in energy technology. The earliest was the introduction of practical steam power toward the end of the eighteenth century. Steam technology powered the industrial revolution in the 1800's. Two other momentous developments occurred in 1900's, and either one by itself deserves to be called disruptive. One was electric power and the other was the appearance of efficient internal combustion engines. Used only for lighting at first, electricity soon began to displace steam as the proximate motive power for factory machinery and even for short haul rail transportation. The gasoline engine developed rapidly enough to power the Wright brothers' first airplane flight in 1903. The twentieth century became the century of ubiquitous electric lighting, electric appliances, and the automobile, airplanes and diesel engines.

As we ponder the future course of energy technology, it is worth keeping in mind some characteristics of these earlier energy revolutions. I will mention three. The first is what you might call the geographical aspect of the technologies. When steam displaced water power, it set manufacturing free from the limits geography imposed on factory locations. Manufacturing continued to develop near its origins beside streams and rivers, but the main advantage of these turned to transport of coal and raw material. The use of water for transport was enhanced by a vigorous period of canal building both in Britain and America. Steam, however, was an ideal power source for rail transportation, and canals rapidly gave way to railroads. Railroads were truly disruptive, and changed forever the ancient pattern of social development along the world's river valleys. The development of smaller self-contained engines, and particularly the efficient internal combustion engine, advanced this evolution a giant step further and dispersed human occupation away from the transportation routes and nodes established by the prior technologies of water and rail. Geography is an important aspect of electrical power too. Alternating current technology won out over direct current because its higher voltages could transmit power more efficiently at a greater distance from its primary source. The cornucopia of small electrically powered devices produced by Edison and Westinghouse and others gave further impetus to the dispersion of society into low population density areas where domestic help and centralized services were unavailable. Each successive energy revolution decreased the significance of geographical location for human endeavors. The range of productive activities that could occur in any given region grew progressively broader and less dependent on local conditions and resources.

A second interesting characteristic of these disruptive energy innovations is what I will call the diffusion of powered work. Prior to the industrial revolution, non-animal energy sources for functions other than heat and light consisted of wind and flowing water, which had been employed in mills since ancient times. Mills established the paradigm of a central motive force linked to productive machinery. The peripheral machinery was indifferent to the type of power source. Steam at first simply replaced wind or water wheels or animal driven windlasses at the mill site. But with a rapid sequence of mechanical improvements (none of which, by the way, owed anything to science) the concept of a steam engine emerged – a free standing, even portable, source of motive power much like an animal but far more energetic and robust and far less expensive to maintain. The progression of smaller, ever more efficient engines powered by steam, electricity or chemical fuel made it possible to consider powering activities that previously had been performed only by human hands. Electrically operated devices, in particular, brought power-assisted work into the home and workplace and fueled a wave of innovation that persists to this day. Early applications to big steam-driven machinery for agriculture, transportation, and factory based manufacturing were joined by a succession of smaller engines, mostly electrical, for domestic and small office operations, recreation, and entertainment. The miniaturization of engines created an entirely new market for labor saving devices, and the market in turn created a strong innovation pull.

The third characteristic of these nineteenth century energy technologies, and indeed of any technology mighty enough to be called revolutionary, is the system infrastructure needed to exert their disruptive impact. In the case of steam power, the technology for rudimentary systems of rails and extremely short-range mechanical power transmission systems were already in place, thanks to the mining industry and water powered factories, and only needed to be extended to new purposes. By contrast the electricity infrastructure, including generation and transmission concepts, lighting devices, and motors, had to be developed from scratch. Early electric entrepreneurs such as Edison and Tesla in the U.S. and Ferranti in Britain, tried to provide all of these at once, and largely succeeded. In these days of rapid translation from research lab to product, we think of the past as slower paced, but within three years of Faraday's discovery of magnetic induction in 1831, rotating coil generators were being sold commercially in London (to the telegraph industry). The earlier gas-light industry, also perhaps meriting revolutionary status for its social impact, especially on reading habits, had shown the importance of distribution systems, and the even older telegraph industry had strung wires densely within urban centers and along the rail routes, creating a paradigm that electrical power transmission was to copy in its own way. Internal combustion engines exerted their revolutionary impact only as a system of roads grew to carry the cars they powered, which they did explosively when Henry Ford's production methods made the cars affordable. The logistical systems of roads, rails, pipes, and transmission lines and all the ancillary equipment for building, monitoring, and maintaining them, were the means by which the energy innovations achieved their revolutionary effect.

I could also mention as a common characteristic the interconnectedness of all these revolutionary energy technologies. Electricity required steam turbines; steam engines required coal; internal combustion engines employed electrical ignition components as well as petroleum products, which also powered steam and later diesel engines in ships and locomotives. Nearly every basic energy technology ever invented exists today in some form in some niche application, each playing its role in the complex energy economy of our time. If history is a guide, it is highly unlikely that a future technology will completely displace any of the older ones.

Nuclear fission heaters for steam generation, for example, have become an important secondary fuel source, but this technology has not been disruptive as many predicted it would be, and I think the same will be true of fusion power when we finally make it work. Fusion, like fission, will be incorporated along with other energy sources into the electrical distribution network so end users will be only dimly aware of its existence. The real disruptive energy innovations will not be these gargantuan sources of primary power, but smaller scale enabling technologies that extend but do not replace the energy paradigms we have today.

What these new enabling technologies may be is no mystery to this audience, but before I turn to them, I want to draw your attention to two important differences in the energy environment between the 21st century and the 19th. The first is the obvious one that a wide range of energy technologies exists today that did not exist one hundred fifty years ago. That means countries that are still developing do not need to go through all the evolutionary steps that led the industrialized nations to their present state. Consequently the rate of industrialization of recently developed countries is much greater than the pace of the 19th century industrial revolution. If it were not for the second important difference all energy economies in developing countries would look like those in the highly developed G8 nations – they would simply import and adapt the pre-existing technologies. The crucial second difference is concern for sustainability.

Sustainability is an entirely new driver for energy technologies, and it is the chief characteristic of what we are calling our "energy challenges." The concept of sustainability acknowledges the finiteness of natural resources, the vulnerability of the environment, and the limited tolerance of populations for hazardous or otherwise undesirable side effects of technologies. We see its impact in the search for renewable energy sources and for sources that do not release carbon dioxide into the atmosphere. In the long run sustainability is a necessity, not an option, and it will certainly have an impact on the shape of energy technologies at mid-21st century.

It is time now to say a few words about technical responses to the problem of sustainability and how they are related to the current revolutionary capabilities of science. First, it is obvious that all problems related to the use of energy are diminished if we use less of it. What are commonly called "conserving" or "energy efficient" technologies are pervasive in their impact. In this regard a very healthy "green chemistry" trend can be identified in the industrial sector that extends back several decades. Originally the aim was to reduce regulated contaminants, but pollution prevention efforts were soon seen to reduce production costs overall. Today major chemical companies are funding research into new approaches to chemical synthesis and production that reduce the number of reagents, the amount of waste product, and the consumption of energy and non-renewable resources. Catalysts are key ingredients of chemical production, and they operate on the molecular level – a level open to exploration by the powerful methods of nanotechnology. This year's Nobel Prize in Chemistry went to scientists who elucidated an elegant catalytic process that holds much promise for reducing the energy requirements for key chemical processes. I think breakthroughs in catalysis are likely to be the first economically significant payoff of nanotechnology. Energy efficiency is also enhanced by miniaturization, and by the delocalization of electrical generation which reduces transmission losses.

Transmission losses, which are very serious for electrical distribution, can be eliminated completely if electricity could be generated where needed. At the present time, only photovoltaic sources, and in some locations wind power, have this capability. We have seen slow, steady improvement in photovoltaic efficiencies over decades, and combined with the reduction in power requirements for useful devices, these incremental advances have led us to the threshold of practical large scale deployment. Solar power is already favored for niche applications where extensions of the electrical distribution system are too expensive.

A serious problem with solar and wind electrical sources is their intermittent performance. The obvious solution to this problem is improved battery technology, which is coming along more slowly than I would have predicted ten years ago. But here too the revolutionary new tools for understanding and manipulating atomic-scale structures are paying off. The combination of improved solar cell efficiencies and substantially improved battery performance will have a very significant impact on energy infrastructure. It would render the electrical distribution system unnecessary and create true geographical independence for many important applications, particularly in the domestic sector. Battery improvements by themselves exert a very high leverage on applications, as we know from our experience with portable computers, cell phones, and other devices. Fuel cell improvements would provide comparable benefits. All these potentially disruptive advances depend on the improvement of material properties at the nano-scale.

The proliferation of small scale, stand alone electrical generators and efficient batteries will change the function of the electrical distribution grid, with energy exchanges taking place in both directions from end users. The grid, already complex and difficult to manage, will become more like the Internet, with multiple users drawing and supplying power as different transient generators kick in or out of service. Real time simulation of grid performance, and associated extensive modeling of the entire interconnected energy distribution systems may become necessary for reliable grid operations. Only a fraction of our logistical systems for all energy technologies is well characterized today. As the grid becomes more complex, and energy technologies even more interconnected, better documentation, simulation, and analysis of logistical systems will become essential.

One of my favorite candidates for a disruptive energy technology is solid state lighting, whose low energy consumption is already being exploited in flashlights, traffic signals, and indicator lights of all kinds, including those on our cell phones. Improvements in conversion efficiencies in the visible spectrum can be expected given the very large efficiencies currently achieved in infra-red operation. The replacement of incandescent and fluorescent lighting with solid state devices, and associated savings in wiring and maintenance will be disruptive in the lighting industry, but will not be revolutionary because the technology replaces an older technology that does more or less the same thing.

Transportation in developed countries is one of the least efficient uses of energy, and we currently hope to improve performance of personal vehicles with a combination of electric drives, fuel cells, and a new system of hydrogen fuel generation and distribution. If the hydrogen is generated in a process that sequesters or avoids carbon, then the whole cycle will be environmentally friendly as well as more efficient. This concept is also very sensitive to improvements in battery technology. In this concept hydrogen is simply another medium for transmitting energy from a central source to peripheral uses.

You can see that all these examples depend on improvements in various materials – catalysts, photovoltaics, batteries, fuel cells, solid state light sources, even hydrogen storage media – in each case the relevant materials have desirable functional properties that originate in their small scale structure. And it is here that our current revolutionary science capabilities can have significant impact. In our industrially developed nations, no single application will have the revolutionary effect of the steam engine, but at multiple points in the existing complex energy infrastructure the materials advances we can expect from science will profoundly influence the cost and environmental impact of many end uses. As we contemplate how we will meet our energy challenges, we need to keep the entire system in mind, from primary fuels to social behavior.

The energy infrastructure is so rich with possibilities for improvement that I cannot do them justice in these brief remarks. It is this richness that we must exploit to enable future generations in every country to enjoy a sustainably high standard of living into the indefinite future. The link between today's revolutionary science capabilities and our energy challenges occurs at the nanoscale, and it is fitting that today's meeting is taking place at a laboratory devoted in large measure to this exciting frontier. This workshop is important, and I am pleased that it has attracted experienced and influential participants. Thank you for giving me an opportunity to make these very general observations. I look forward to reading the results of your deliberations.