M. S. Dresselhaus* & I. L. Thomas
*Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
†Office of Basic Energy Sciences, U.S. Department of Energy, 19901 Germantown Road, Germantown, Maryland 20874-1290, USA
Fossil fuels currently supply most of the world’s energy needs, and however unacceptable their long-term consequences, the supplies are likely to remain adequate for the next few generations. Scientists and policy makers must make use of this period of grace to assess alternative sources of energy and determine what is scientifically possible, environmentally acceptable and ...view middle of the document...
Nuclear plants produce radioactive fission products. Hydroelectric plants require dams and large lakes. Solar energy and wind energy require large areas and are limited geographically. Geothermal sources are limited to very few locations. Schemes using small temperature gradients in the earth or oceans have lowthermal efficiencies, and hence require very large heat-exchanger areas.
At present most of the world’s energysupplycomes from fossil and nuclear sources (see Fig. 1). And although mankind is increasinglyhaving to face the issues of resource limitation and environmental pollution, these sources will continue to be important in providing energy worldwide for the next few generations. Below, accordingly, we look briefly at the prospects for these energy sources, emphasizing the importance of addressing the issue of CO2 sequestration now, and keeping the nuclear energy option open. But to meet increasing global demands for energy and to allow for the depletion of fossil fuel supplies in the coming years, alternative ‘clean’ energy sources, which do not depend on fossil fuels and which have a tolerable
Natural gas 19.29
Crude oil 12.54
Fossil fuels 57.67
Domestic production 72.52
Natural gas 22.10
Fossil fuels 81.56 |
Consumption 96.60 |
Residential and commercial 34.17
Crude oil and products 22.53
Nuclear 7.73 Renewables 7.37
Figure 1 Energyflowdiagramfor theUnitedStatesfor 1999, inquads (1 quad= 1015 Britishthermal units= 2.9x1011 kWh). Theaverage energyconsumptionintheUnitedStatesis0.4x10–6 quadsper person
per year, andtheUSpopulationisabout 5%of that onplanet Earth. Energy consumptionislargecomparedwithfoodconsumption(1.2x104 kJ per
dayper person, whichtranslatestoonly0.4x10–8 quadsper personper year). Somecorrespondingnumbersfor worldenergyconsumptionfor 1999, inquads, are: petroleum149.7; natural gas87.3; coal 84.9; nuclear 25.2; hydro, geothermal, solar, windandother renewables29.9; total worldenergyproductionis377.1 quads(ref. 8).
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NATURE | VOL 414 | 15 NOVEMBER 2001 | www.nature.com
Figure 2 Dynamometer testingontheHondaInsight, ahybridelectric vehiclethat hasrecentlyenteredthemarket place.
environmental impact, must be developed. The five following articles1–5 review the present status of several such sources. Renew- able means of producing and storing electricity are expected to be increasingly important in the future and, given the recent strides in condensed-matter physics and materials technology, could compete with existing technologies. For technologies using renewable energysources, remarkable stepsforward are takingplace in the...