Demands are high for low-power electronics
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Energy Sector Analysis
One option for improving energy consumption is to look beyond silicon for new materials that could make transistors more energy efficient.
Demands are high for low-power electronics By Angela Saini
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ever have our personal gadgets been so small and yet expected to do so much. The thirst for energy of our multifunctional cell phones and personal computers has a frustrating impact on their battery lives and also drives up energy usage. It is difficult to compile figures for just how much energy this is in total, but in 2011, researchers at the University of California–Berkeley put a very rough upper estimate of the average power consumed by Internet use globally, including by laptops, smartphones, and data servers, at around 300 gigawatts—nearly two percent of all power. Expert analysis carried out for the New York Times newspaper in 2012 estimated that data servers across the world use 30 gigawatts. Environmental concerns about this, as well as demand from consumers for devices that don’t need recharging so often, are pushing the development of electronics that can run on far less power. But that is not to say that energy savings have not already been made. Koomey’s Law, devised by research fellow in energy and finance at Stanford University, Jonathan Koomey, in collaboration with Microsoft and Intel, states that the energy efficiency of computer chips (defined here as electricity used relative to processing power) doubles roughly every year and a half (see graph). It is a trend that has been shown to be relatively stable since the construction of the first general purpose computer in 1946. “The key driver for efficiency in microprocessors is shrinking the size of transistors,” said Koomey. The amount of power used by a transistor is directly proportional to its size. These energy savings have moved almost in parallel with the well-known Moore’s Law, which states that the number of transistors per square inch on an integrated circuit doubles every two years. However, while this rapid pace of miniaturization has transformed the scale and price of gadgets and improved efficiency, as the computer chip shrinks, the leakage current that is lost increases. The smaller chips become, the greater the losses. Even losses as tiny as a few hundred picoamps per transistor become more significant when multiplied by a million or billion transistors on a single chip. Another problem with scaling down transistors is that it cannot happen forever. Gordon Moore, one of the founders of Intel Corporation and the person behind Moore’s Law, suggested this year that it may reach its asymptotic limit within a decade. As a result, researchers and chip designers are looking for other avenues to improve energy efficiency. Angela Saini, [email protected]
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MRS BULLETIN
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VOLUME 40 • JULY 2015
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www.mrs.org/bulletin • Energy Quarterly
Around 80% of the power used by a chip is spent in switching transistors. The minimum voltage at which a transistor will switch is roughly one-eighth of a volt, even tho
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