Environmental Engineering Reference
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processes as nanophysics, the physics that applies on the size scale of atoms and
small nuclei, such as protons, deuterons, and 3 He. Needed also are basic aspects of
materials including plasmas and semiconductors. Our hope is to provide a basic
picture based on Schrodingers equation with enough details to account for nuclear
fusion reactions in plasmas and photovoltaic cells in semiconductors. Fromour point
of view, oil, gas, coal, and nuclear fission materials are not renewable sources of
energy because of the short timescales for their depletion. We focus on the energy
that comes from the sun, directly as radiation, and indirectly on earth in the form of
winds, waves, and hydroelectric power.
Beyond this, we consider the vast amounts of deuterium in the oceans as a
sustainable source of energy, once we learn how to make fusion reactors work on
earth. The heat energy in the earth, geothermal energy, is renewable but its overlap
with nanophysics is not large. In a similar vein, the energy of tidal motions, which is
extracted from the orbital energy of themoon around the earth, is a long-termsource,
but it is not strongly related to nanophysics.
The main opportunities for nanophysics are in photovoltaic cells and related
devices, aspects of energy storage, and in various approaches toward fusion based on
deuterium and possibly lithium. We want to learn about the nanophysical nuclear
fusion energy generation in the sun for its own importance, as an existence proof for
fusion, and also as a guide to how controlled fusionmight be accomplished on earth.
1.1.1
Direct Solar Influx
The primary energy source for earth over billions of years has been the radiation from
the sun. The properties of the sun, including its composition and energy generation
mechanisms, are now known, as a result of years of research. Our purpose here is to
summarize modern knowledge of the sun, with the intention of showing how the
energy production of the sun requires a quantummechanical view of the interactions
of particles such as protons and neutrons at small distance scales. The Schrodinger
equation, needed for understanding the rather simple tunneling processes that must
occur in the sun, will be used later to get a working understanding of atoms,
molecules, and solids such as semiconductors.
1.1.1.1 Properties of the Sun
Themass of the sun is M
10 30 kg, its radius R s ¼
10 6 km, at distance
¼
1.99
0.696
10 8 km) from earth. The suns composition by
mass is approximately 73.5%hydrogen and 24.9%helium, plus a distribution of light
elements up to carbon. The suns surface temperature is 5778 - 5973 K, while the
suns core temperature is estimated as 15.7
D es about 93 million miles (1.496
10 6 K. (Much of the data for the sun
have been taken from Principles of Stellar Evolution and Nucleosynthesis by
Donald D. Clayton (University of Chicago, 1983) and Sun Fact Sheet by D. R.
Williams (NASA, 2004)).
We are interested in the energy input to the earth by electromagnetic radiation,
traveling at the speed of light, from the sun. A measurement is shown in Figure 1.3
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