The energy frontier

Insight into the fundamental processes through which energy is transformed can improve existing energy sources and open up novel technologies. History shows that the most far-reaching applications of fundamental science are often unforeseen. Our energy security relies not just on basic and applied science, but also on taking wider socioeconomic frameworks into account.

Novel technologies that will help to guarantee the worldwide energy supply are urgently needed. Although many aspects of energy science are of an applied nature, for instance finding ways to harness and store the power of wind and waves, research into basic science promises new and perhaps surprising possibilities for moving us beyond our dependence on fossil fuels.

In 1905, when Albert Einstein developed his famous formula, E = mc2, revealing the relationship between mass and energy, he could hardly have envisaged the civil nuclear programme that would emerge from our ability to unlock the energy stored in atomic nuclei. Even harder to foresee, a further half-century later, was that humans could be within grasp of producing almost unlimited amounts of clean energy through nuclear fusion.

Fusion energy is a formidable challenge, because it relies on combining hydrogen isotopes to form helium nuclei by confining a plasma at temperatures of hundreds of millions of degrees. Several promising approaches are currently being explored, including the giant ITER tokamak project in France, related stellarator designs — in particular the Wendelstein 7-X experiment under construction in Germany, and a number of laser-fusion projects. Commercial power plants could start operating in 2050, providing researchers can overcome significant materials science problems. Not all fundamental energy-related research involves such huge projects and long time-scales, however.

Energy transfer

Most people tend to associate ‘energy’ with the immaterial substance that lights our lamps or heats our houses. To scientists, however, energy is a central and well- defined concept that applies right down to molecular and atomic scales.

At the heart of each process relevant to our energy supply — ranging from photosynthesis to the workings of solar cells and batteries — is the movement of electrons from one atom or molecule to another. Understanding the mechanisms of eletron transfer is therefore of vital importance.

Elucidating the electron-transfer processes that take place in plants, for instance, might provide the blueprint for mimicking elements of photosynthesis using simpler, artificial systems1,2. This could allow scientists to realize the old dream of splitting water into hydrogen and oxygen by solar radiation with the help of a catalytic system (currently, molecular hydrogen is mostly extracted from natural gas, which requires large amounts of energy). As hydrogen can be converted to other forms of energy through various pathways, such a cheap and efficient source of clean hydrogen could revolutionize our energy resourses.

A hydrogen infrastructure, which would provide electricity from fuel cells or gas and steam turbines, can only become part of our energy mix if ways are found to store and transport molecular hydrogen. Although high-pressure storage or liquid hydrogen are presently the favoured methods, intense effort is being invested to find chemical compounds that offer higher storage den- sities3 — which is crucial for using hydrogen in cars.

Methane, which is the main component of natural gas, could also herald such a clean energy infrastructure. Not only is methane easier to handle than hydrogen, but there are also a number of pathways by which to produce it. One of the most efficient is to ferment biomass in the absence of oxygen; however, to improve the productivity of fermenters we need to understand these biochemical pathways in greater detail — perhaps to the point where we can use genetically modified organisms instead of natural strains.

Whether pure biological pathways or chemical transformations are employed, a fundamental understanding of the genetic and metabolic requirements for high biomass production will improve energy yields4,5.

Harnessing solar energy

Producing fuels and chemicals from biomass indirectly harnesses the power of the sun; photovoltaics produce one of the most versatile forms of energy — electricity — directly. Fundamental semiconductor physics paved the way for the silicon-based solar panels in operation today; however, polymeric materials promise more cost- efficient and flexible solutions — with the ideal being paint-on or spray-on solar cells. Before this goal can be reached, the efficiency of the materials must be improved and their lifetimes extended. This requires fundamental research into the synthesis of novel molecules and methods for assembling controlled nanostructures such as fullerenes, which were a serendipitous discovery6,7.

Mundane as it may seem, improving the electrodes of solar cells is also crucial if photovoltaics are to enter widespread use (novel electrodes will also greatly benefit fuel cells and batteries for mobile technologies). The transparent electrodes of todays solar cells rely on indium tin oxide, but indium is expensive and rare. Novel materials such as graphene — single layers of carbon atoms — might offer a cheaper alternative, if they can be easily manufactured8.

Fundamental materials science might also yield high-performance polymers and novel alloy steels, with excellent mechanical properties and lower weight, thus realizing immediate savings in fuel consumption. Similarly, high-temperature ceramics could allow an increase in the operating temperature and, thus, the efficiency of motors or turbines9. New thermoelectric materials that generate electricity from temperature differences, for example those in car engines, also hold promise for energy efficiency10.

When science is not enough

Energy issues are often discussed solely on a technological level. As the decades-long debates concerning nuclear energy deomonstrate, however, this is often insufficient. Future energy technologies, not least fusion, might have to overcome similar resistance to that faced by the nuclear industry. In a hydrogen economy, for example, the fear of explosions might prevent widespread introduction. Indeed, current discussions about the risks of carbon dioxide capture and sequestration — technologies that could allow us to burn fossil fuels without the damaging emissions – indicate that even this technology might not be easily accepted.

Input from the social sciences and economics is therefore vital when planning our energy future. Innovations related to novel energy systems should diffuse into society, as they require understanding and acceptance. As energy infrastructures are becoming more integrated within Europe and the world, questions of international law are gaining importance.

>> Input from the social sciences and economics is vital when planning our energy future.

This close interaction between science and the humanities, combined with continued investment in basic and applied research, is vital if we are to solve one of the biggest challenges of this century.

Single layers of graphite, graphenes, are a hot topic in materials science owing to their exciting physical properties. Researchers at the Max Planck Institute for Polymer Research have introduced chemical routes towards the large-scale and cheap synthesis of structurally perfect graphene layers. Graphene films with high transparency and conductivity can serve as window electrodes in organic solar cells, light-emitting diodes and liquid-crystal displays, replacing conventional electrodes (Pang, S. et al. Adv. Mater. 21, 3488, 2009).

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