Basic Research Needs for Solar Energy Utilization - Office of ...
Basic Research Needs for Solar Energy Utilization - Office of ...
Basic Research Needs for Solar Energy Utilization - Office of ...
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EXECUTIVE SUMMARY<br />
World demand <strong>for</strong> energy is projected to more than double by 2050 and to more than triple by<br />
the end <strong>of</strong> the century. Incremental improvements in existing energy networks will not be<br />
adequate to supply this demand in a sustainable way. Finding sufficient supplies <strong>of</strong> clean energy<br />
<strong>for</strong> the future is one <strong>of</strong> society’s most daunting challenges.<br />
Sunlight provides by far the largest <strong>of</strong> all carbon-neutral energy sources. More energy from<br />
sunlight strikes the Earth in one hour (4.3 × 10 20 J) than all the energy consumed on the planet in<br />
a year (4.1 × 10 20 J). We currently exploit this solar resource through solar electricity — a<br />
$7.5 billion industry growing at a rate <strong>of</strong> 35–40% per annum — and solar-derived fuel from<br />
biomass, which provides the primary energy source <strong>for</strong> over a billion people.<br />
Yet, in 2001, solar electricity provided less than 0.1% <strong>of</strong> the world's electricity, and solar fuel<br />
from modern (sustainable) biomass provided less than 1.5% <strong>of</strong> the world's energy. The huge gap<br />
between our present use <strong>of</strong> solar energy and its enormous undeveloped potential defines a grand<br />
challenge in energy research. Sunlight is a compelling solution to our need <strong>for</strong> clean, abundant<br />
sources <strong>of</strong> energy in the future. It is readily available, secure from geopolitical tension, and poses<br />
no threat to our environment through pollution or to our climate through greenhouse gases.<br />
This report <strong>of</strong> the <strong>Basic</strong> <strong>Energy</strong> Sciences Workshop on <strong>Solar</strong> <strong>Energy</strong> <strong>Utilization</strong> identifies the<br />
key scientific challenges and research directions that will enable efficient and economic use <strong>of</strong><br />
the solar resource to provide a significant fraction <strong>of</strong> global primary energy by the mid<br />
21st century. The report reflects the collective output <strong>of</strong> the workshop attendees, which included<br />
200 scientists representing academia, national laboratories, and industry in the United States and<br />
abroad, and the U.S. Department <strong>of</strong> <strong>Energy</strong>’s <strong>Office</strong> <strong>of</strong> <strong>Basic</strong> <strong>Energy</strong> Sciences and <strong>Office</strong> <strong>of</strong><br />
<strong>Energy</strong> Efficiency and Renewable <strong>Energy</strong>.<br />
<strong>Solar</strong> energy conversion systems fall into three categories according to their primary energy<br />
product: solar electricity, solar fuels, and solar thermal systems. Each <strong>of</strong> the three generic<br />
approaches to exploiting the solar resource has untapped capability well beyond its present<br />
usage. Workshop participants considered the potential <strong>of</strong> all three approaches, as well as the<br />
potential <strong>of</strong> hybrid systems that integrate key components <strong>of</strong> individual technologies into novel<br />
cross-disciplinary paradigms.<br />
SOLAR ELECTRICITY<br />
The challenge in converting sunlight to electricity via photovoltaic solar cells is dramatically<br />
reducing the cost/watt <strong>of</strong> delivered solar electricity — by approximately a factor <strong>of</strong> 5–10 to<br />
compete with fossil and nuclear electricity and by a factor <strong>of</strong> 25–50 to compete with primary<br />
fossil energy. New materials to efficiently absorb sunlight, new techniques to harness the full<br />
spectrum <strong>of</strong> wavelengths in solar radiation, and new approaches based on nanostructured<br />
architectures can revolutionize the technology used to produce solar electricity. The<br />
technological development and successful commercialization <strong>of</strong> single-crystal solar cells<br />
demonstrates the promise and practicality <strong>of</strong> photovoltaics, while novel approaches exploiting<br />
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