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PART 14 — The “Other” Solar Energy
Back to the Basics — the Sun’s Central Role
Human beings love the sun! There are
very few who don’t welcome the return of
daylight every morning or the return of the
sun’s warmth every spring. The sun is such a
constant feature in our lives, that it is often
taken for granted. This is especially true
when considering energy policy choices.
With the exception of nuclear power and
geothermal energy, our entire civilization is
powered directly or indirectly by the sun!
Because human beings are thinkers and
dreamers, we have calculated the vast
amount of energy received free by the earth
each day from the sun. We have wondered
how that energy could be put to use. One
early idea was to let the sun’s heat dry meat for preservation, dry clothes and dry mud bricks for building materials. Solar reflection ovens have been developed that can
cook food, bake bread or distill water. The photovoltaic effect of certain materials converting sunlight into electricity
was discovered in 1839. The first genuine photo cell was
built around 1883 with an efficiency of less than 1 percent.
Today, commercially available silicon-based solar cells have
efficiencies approaching 15 to 17 percent.
One of the first indirect uses of solar energy was the
capture of wind with sails to power ships and windmills to
grind grain. The energy in wind comes from the sun heating the earth’s atmosphere. A second indirect use of solar
energy is using running water to drive a wheel to produce
useful mechanical or electric energy. Running water starts
out as water evaporated by the sun’s heat, which then condenses as rain or snow, which falls on an area of higher elevation and then flows to a lower elevation.
The Basic Problems With Using Solar Energy
However, there are three basic problems involving the
use of solar energy, either directly or indirectly. The first
problem is intermittency. The energy is available only
when the sun shines, the wind blows or the water flows.
Therefore, some method of storing the energy is needed.
For example, if rainfall is seasonal, a dam can be built on a
stream or river to store water for a continuous flow. But
water behind a dam takes up lots of land and affects fish
migration, both of which are big environmental issues
today. Batteries can be used to store solar- or wind-generated electricity, but they are big, expensive and store relatively little power for their size.
The second problem is low energy density. Although
massive amounts of solar energy hit the earth daily, they
are spread over a wide area. Therefore, the amount of energy received per square meter is small compared to other
fuels (See Part 5 – Figure 2 – Energy Densities Table). Direct or indirect solar energy can be made more dense or
“concentrated” by expanding the surface area used to col20D
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lect the energy. For example, we can use multiple and/or
larger sails on ships, larger blades on wind turbines, and
employ acres of land for solar panel farms. Another approach would be to use a smaller amount of solar energy
over a longer time, which is what occurs when drying
clothes or using the sun to dry mud bricks.
The third problem is portability. Because the sun’s energy only strikes a fixed location for fixed periods of time,
there is no known way to “carry” the direct use of solar energy from one point to another. The invention of the sail to
propel ships does provide portability of indirect solar energy, provided the wind doesn’t stop blowing.
Nature’s Solution — Photosynthesis
Interestingly, nature solves all three problems with solar
energy using photosynthesis, which is illustrated in figure
1. As you will recall from your grade school studies, photosynthesis is the process plants and some algae use to convert unusable sunlight to usable chemical energy stored in
sugar. Plant cells use the
Figure 1
green plant pigment chlorophyll to produce nature’s
basic “green” energy fuel,
which is the basic food of all
living things, and as a byproduct releases the oxygen
we absolutely need to stay
alive.
Let’s take a closer look at
the chemical equation for
photosynthesis: 6CO2 +
6H2O + sunlight → 6O2 +
C6H12O6. Now most of us
don’t speak like chemists.
You would read the equation
as: Each plant cell takes six
molecules of carbon dioxide
plus six molecules of water
plus sunlight to yield six
molecules of oxygen and one Source: www.emc.maricopa.edu/
big molecule of glucose
(sugar). When we breathe, human beings (and other animals) reverse the process. We breathe in six molecules of
oxygen and combine it with one molecule of glucose released through food digestion, and then exhale six molecules of carbon dioxide and six molecules of water vapor
while releasing the stored solar energy to power the cells in
our bodies.
So nature solves the problem of intermittency by storing solar energy as chemical energy. The problem of energy density is solved by accumulating a large amount of
sugar throughout the plant’s relatively long growing season. And the problem of portability is solved in two ways.
Humans and animals can move from one plant to another to eat the food. In between plants, the food is carried (stored) and digested in our stomachs and then
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“burned” through respiration.
Human beings as dreamers
and thinkers looked for better
ways to do things without relying
on the brute muscle power of
men and livestock. First, wood
was burned for heat and light,
then plant and animal oils were.
Note that these fuel sources all
originally derived their energy
from the sun through photosynthesis. Then, people discovered
coal, petroleum oils and fossil
fuels, which had even higher energy densities. But where did fossil fuels come from?
“Fossil” fuels are believed to
have formed mostly during the
Carboniferous period about 360
to 286 million years ago. “Carboniferous” gets its name from
carbon, which is the basic element in coal, oil and gas. Carbon
is also a basic element in carbon
dioxide, glucose (sugar) and all
living plants and animals on earth.
During this period, the land was
covered with swamps filled with huge
trees, ferns and other leafy plants.
The water was filled with algae,
which is made up of millions of individual green plants
(and is the green stuff
you see on stagnant
ponds of water). After
those plants died,
they sank to the bottom. This process repeated itself over millions of years.
Eventually, this material was covered
by tons of rock, which provided the
intense pressure needed to turn the
ancient, dead plant matter into coal,
oil and/or natural gas, which are really different kinds of carbon compounds.
Amazingly, we find that fossil fuels
are also the result of photosynthesis!
Except nature has accumulated the
results of millions of years of annual
photosynthesis combined with the
energy supplied by pressure to further concentrate the amount of
stored sunlight in the form of chemical energy available to us. Fossil fuels
therefore have a high energy density
and the added advantage of being
both storable and portable. If we didn’t have them, we would need to invent a substitute, which is what grain
planet to survive, then how can it be
a “pollutant” as determined by our
current EPA? Such a basic question
forces one to ask — is this EPA decision science or politics? A related
question is, since fossil
fuels originally come
from plants that pulled
carbon dioxide out of
the air when they were
living, is returning that
carbon to its original
source really “polluting”?
And finally, if carbon is key to all
life on earth and fuels our human
civilization, then wouldn’t carbon
taxes and/or regulation be a tax on or
regulation of all life and human industry? Because of the large tax revenues to be raised and major changes
required to implement such a carbon
tax/regulatory plan, no thinking person would readily agree to the proposal. Unless, of course, there was a
“crisis” requiring such a change. But
isn’t that exactly what some are suggesting? Is that assertion of “crisis”
science, politics or just another suit
of the Emperor’s new clothes?
“If carbon is key to all life on earth and fuels
our human civilization, then wouldn’t
carbon taxes and/or regulation be a tax on
or regulation of all life and human industry?”
and sugar cane alcohol and biodiesel
fuels are intended to be.
So How Does This Relate To Energy
and Environmental Politics?
Now that we have an understanding of the “big picture,” in the next
several editorials we can begin to discuss “carbon” policy as it relates to
energy production and the economy.
Sometimes it is necessary to review
the “basics” to clarify some key questions before getting carried away with
the details of today’s political debate.
For example, if carbon dioxide is a
necessary input for green plants to
live, and then to create the food and
oxygen needed for all life on this
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