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CONTACT: NEST Energy Systems Phone: 928-460-2811 TL@nestenergysystems.com
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DOE
Report on Global Energy Resources Extracted from the April 2005
report entitled The U.S. Department of Energy,
Office of Science, Chair: Nathan Lewis (CIT) Current global energy consumption
is 4.1 × 1020 J annually, which is equivalent to an instantaneous
yearly-averaged consumption rate of 13 × 1012 W [13 trillion watts, or 13
terawatts (TW)]. Projected population and economic growth will more than double
this global energy consumption rate by the mid-21st
century
and more than triple the rate by 2100, even with aggressive conservation
efforts. Hence, to contribute significantly to global primary energy supply, a
prospective resource has to be capable of providing at least 1-10 TW of power
for an extended period of time. The threat of climate change
imposes a second requirement on prospective energy resources: they must produce
energy without the emission of additional greenhouse gases. Stabilization of
atmospheric CO2 levels at even twice their preanthropogenic value
will require daunting amounts of carbon-neutral energy by mid-century. The
needed levels are in excess of 10 TW, increasing after 2050 to support economic
growth for an expanding population. The three prominent options to
meet this demand for carbon-neutral energy are fossil fuel use in conjunction
with carbon sequestration, nuclear power, and solar power. The challenge for
carbon sequestration is finding secure storage for the 25 billion metric tons of
CO2 produced annually on Earth. At atmospheric pressure, this
yearly global emission of CO2 would occupy 12,500 km3,
equal to the volume of Lake Superior; it is 600 times the amount of CO2
injected
every year into oil wells to spur production, 100 times the amount of natural
gas the industry draws in and out of geologic storage in the United States each
year to smooth seasonal demand, and 20,000 times the amount of CO2
stored
annually in Norway’s Sleipner reservoir. Beyond finding storage volume, carbon
sequestration also must prevent leakage. A 1% leak rate would nullify the
sequestration effort in a century, far too short a time to have lasting impact
on climate change. Although many scientists are optimistic, the success of
carbon sequestration on the required scale for sufficiently long times has not
yet been demonstrated. Nuclear power is a second
conceptually viable option. Producing 10 TW of nuclear power would require
construction of a new one-gigawatt-electric (1-GWe)
nuclear fission plant somewhere in the world every other day for the next 50
years. Once that level of deployment was reached, the terrestrial uranium
resource base would be exhausted in 10 years. The required fuel would then have
to be mined from seawater (requiring processing seawater at a rate equivalent to
more than 1,000 Niagara Falls), or else breeder reactor technology would have to
be developed and disseminated to countries wishing to meet their additional
energy demand in this way. The third option is to exploit
renewable energy sources, of which solar energy is by far the most prominent.
United Nations (U.N.) estimates indicate that the remaining global, practically
exploitable hydroelectric resource is less than 0.5 TW. The cumulative energy in
all the tides and ocean currents in the world amounts to less than 2 TW. The
total geothermal energy at the surface of the Earth, integrated over all the
land area of the continents, is 12 TW, of which only a small fraction could be
practically extracted. The total amount of globally extractable wind power has
been estimated by the IPCC and others to be 2-4 TWe.
For comparison, the solar constant at the top of the atmosphere is 170,000 TW,
of which, on average, 120,000 TW strikes the Earth (the remainder being
scattered by the atmosphere and clouds). It is clear that solar
energy
can be exploited on the needed scale to meet global energy demand in a
carbon-neutral fashion without significantly affecting the solar resource. Solar energy is diffuse and intermittent, so effective storage and distribution are critical to matching supply with demand. The solar resource has been well established, and the mean yearly insolation values are well documented. At a typical latitude for the United States, a net 10% efficient solar energy “farm” covering 1.6% of the U.S. land area would meet the country’s entire domestic energy needs; indeed, just 0.16% of the land on Earth would supply 20 TW of power globally. For calibration purposes, the required U.S. land area is about 10 times the area of all single-family residential rooftops and is comparable with the land area covered by the nation’s federally numbered highways. The amount of energy produced by covering 0.16% of the Earth’s land area with 10% efficient solar cells is equal to that produced by 20,000 1-GWe nuclear fission plants. This many plants would need to be constructed to meet global demands for carbon-neutral energy in the second half of the 21st century if carbon sequestration were to prove technically nonviable and if solar energy were not developed. |
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