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Electricity Now and When

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Science  18 Nov 2011:
Vol. 334, Issue 6058, pp. 921
DOI: 10.1126/science.334.6058.921
CREDIT: FOTOSEARCH

Whether it started with falling water or with the burning or radioactive decomposition of fuels, creating and delivering electrical power used to be a straightforward process of trying to balance generation, distribution, and demand at a reasonable cost to end users. Peak power requirements have grown, as has the size of the fluctuations between daily maximum and minimum requirements. Very little capacity exists for storing electricity, but an increased reliance on renewable sources, especially solar and wind power, will require better solutions to electricity storage to cope with their intermittent nature.

Dunn et al. (p. 928) review the present situation with regard to electrical energy storage, which is now dominated by sodium-sulfur (Na/S) and sodium–metal chloride (Na/MeCl2) batteries that operate with high-temperature electrolytes. Redox flow and lithium batteries are emerging options, and they also discuss the “rolling storage” of electricity in battery-powered vehicles. In a related Perspective (p. 917), Gogotsi and Simon demonstrate a need for a better way to assess and compare the properties of electrochemical capacitors and lithium ion batteries, because current metrics do not necessarily reflect device performance.

If there were efficient conversion methods, electrical energy could be stored as a fuel rather than directly as stored charge. This is often discussed in terms of a hydrogen economy, but that is by no means the only fuel of interest. Solid-oxide fuel cells, which operate at high temperatures, could allow distributed electrical generation from natural gas or regenerated fuels created from excess electrical power, or allow supplementation of the grid during peak power periods. Wachsman and Lee (p. 935) discuss developments that should allow lower operating temperatures and costs for these sources, which could widen their adoption as both stationary and mobile sources.

Two News stories describe aspects of better ways to harvest solar power. Cartlidge (p. 922) describes efforts to improve thermal storage, a technology that enables solar plants to continue generating electricity after dark. Service (p. 925) discusses recent progress in artificial photosynthesis to create hydrogen and hydrocarbon fuels, which could be used either for transportation or for centralized electricity generation.

A growing population and the push toward renewable and less polluting resources are driving the construction of a wider range of methods for electricity generation and a much more complicated electricity grid. In many developed countries, a reliable supply of electrical power is taken for granted, but in many developing countries, regular and widespread outages can be the norm. The research outlined in these pieces points to some of the ideas being considered to ensure that the lights can stay on.

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