Environmental Engineering Reference
In-Depth Information
8 ThesolarradiationinterceptedannuallybytheEarthisestimatedat3.9millionexajoules
( Section 4.4 . ).
9 Sputnik was the first artificial satellite, launched by the Soviet Union in 1957.
10 In direct current (DC), the flow of electric charge is only in one direction
(conventionally from a positive to a negative pole), whereas in alternating current (AC),
the movement of electric charge periodically reverses direction. AC is the form in which
electric power is delivered to businesses and residences. This is why a power inverter is
needed.
11 Bars of monocrystalline silicon are produced by dipping a 'seed crystal' into a crucible
of molten silicon. In this process, a larger crystal of silicon 'grows' around the seed.
12 Multijunction concentrators have achieved more than 40 per cent conversion efficiency
in laboratory tests. To maximise efficiency, CPV systems use solar tracking (the array
follows the path of the sun through the sky) and must be located in areas that receive
plentiful direct sunlight. Diffuse light, which occurs in cloudy and overcast conditions,
cannot be concentrated.
13 Average global PV module factory prices dropped from about 22 U.S. dollars per watt
in 1980 to less than 1.5 U.S. dollars per watt in 2010. PV electricity generation costs range
from 14 to 36 U.S. cents per kilowatt-hour. In regions of high solar irradiance in Europe
and the United States (> 1,800 kilowatt-hours per square metre per year) costs are in the
range of 19-22 U.S. cents.
14 Their principal source was the second-century satirist Lucian.
15 Since the 1970s there have been a number of attempts to replicate Archimedes's deadly
heat ray, including a 2005 experiment at the Massachusetts Institute of Technology. It
was found that the bronze mirrors available at that time could hardly have ignited vessels
hundreds of metres from Syracuse's walls (Zamparelli 2005a , 2005b ) .
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