Vidic, 2:00
R13
ENERGY AND THE ENVIRONMENT: HOW CONCENTRATING SOLAR
POWER CAN PROTECT THE ENVIRONMENT
Vincent Antoine Verret (viv14@pitt.edu)
THE ISSUE: ACQUIRING LAND ON
WHICH TO BUILD CONCENTRATING
SOLAR POWER PLANTS
In the Energy industry there are many methods of
generating the electricity that we use power our society. A
good many of these energy sources have impacts on the
environment in which we live. Our current main energy
source, the combustion of fossil fuels or natural gas creates
greenhouse gases that heat the atmosphere and affect the
climate. Others have an effect on plant and animal life in the
surrounding areas. Solar powered electricity generation is one
of the many major developments for renewable, clean energy
sources. It has little to no effect on the climate, and has no
components that interfere with animal life, outside its initial
construction.
There are two major issues with the principle of using the
sun to generate electricity on a utility scale. The first issue is
the issue of the sun only being visible for half of a day. This
issue is solved by using Concentrating Solar Power with a
form of Thermal Energy Storage. This uses the sun to heat a
fluid when then heats water to turn an electricity generating
turbine. This allows some of the energy output by the sun to
be kept to be used when the sun no longer shines on the plant.
The other issue is that at our current stage of technological
development, solar power is incredibly inefficient.
Concentrating Solar Power Plants at present can only reach an
efficiency of 15% [1]. This means that only twenty percent of
the energy that reaches the plant from the sun is actually
converted into electricity. Because of this fact, in order to
create a utilities scale plant on par with output of more
traditional energy sources, Concentrating Solar Power Plants
must be very large and take up very significant plots of land.
This a very great concern when designing a solar power plant
of any kind. This especially applies to Concentrating Solar
Power, as the heliostats (mirrors) that reflect the sun’s light
do nothing on their own, and thus cannot just be place as an
addition to an existing building like a set of photovoltaic
panels. The plant must be designed around their placement.
This creates the issue, where does the land come from.
Does some own it already? Will the plant have to displace a
population so that it can function? As such, engineers must
design these plants in a way that has minimal impact on
nearby communities and companies, without sacrificing the
efficiency of the plant to do so.
WHY CONCENTRATING SOLAR
POWER OVER PHOTOVOLTAIC POWER?
Currently there are two technologies that allow us to
generate electricity using the sun’s rays. The first is the
photovoltaic cell. Photovoltaic cells, more commonly referred
to as solar panels, use the energy of the sun to produce an
electric current directly. This means that if one were to store
the energy created by a photovoltaic cell, it would have to be
stored in a battery which has limited life. A more long term
method for energy storage is to use concentrating solar power
to generate electricity, a method more similar to the way
electricity is generated by nuclear power plants and coal
plants. As demonstrated in Figure 1, CSP uses mirrors to
focus sunlight onto a heat storage medium. When used
without Thermal Energy Storage, the light is reflected to boil
water and drive a turbine. When Thermal Energy Storage is
used, the light is reflected onto a Heat Transfer Fluid (HTF)
that is pumped either directly to the boiler, or is pumped to
heat a the energy storage medium with a high energy density.
The energy storage is usually a mixture of nitrate or nitrite
salts. When the sun is obscured, the storage medium is
pumped to heat the Heat Transfer Fluid and stored to be
reheated. The heat transfer fluid is then pumped to the boiler,
which drives the turbine [2].
FIGURE 1 [3]
A flow diagram of a Andasol-1, a parabolic trough plant
with Thermal Energy Storage
Using Thermal Energy Storage, a plant can remain in
operation when the sun is obscured and is thus a more reliable
source of electricity than a photovoltaic plant.
SOLAR POWER IN CONTRAST TO
OTHER SOURCES OF ENERGY
University of Pittsburgh, Swanson School of Engineering 1
2013-10-29
Vincent Antoine Verret
With every source of energy there always a perceived
main problem that prohibits its use. With fossil fuel plants,
there is the issue of the pollution of the air that results. The
combustion of fossil fuels produces greenhouses gases that
trap the heat of the sun in Earth’s atmosphere. In the long term
this will have effects on Earth’s climate. Climate change is
already causing habitats to disappear for many kinds of
animals. The unsustainable practice of burning fossil fuels
will have an effect on humans as well. With power plants that
depend on nuclear fission, there is the issue of radiation and
safety. In the United States there was the incident at Three
Mile Island in 1979. In Ukraine in 1986 there was the accident
at the Chernobyl Nuclear Power Plant that lead to the
establishing of the 30 kilometer Zone of Alienation. Just two
years ago in Japan there was the Fukushima Daiichi nuclear
disaster as a result of the tsunami in March. The safety hazards
of these resources make them, in their current state of
research, unethical to use according to the code of ethics of
the Institute of Electrical and Electronics Engineers, which
states that its members “accept responsibility in making
decisions consistent with the safety, health, and welfare of the
public, and to disclose promptly factors that might endanger
the public or the environment” [4]. With the possibility of
irradiation of local areas, engineers are obliged work in the
public interest and keep possible dangers in check [5].
On the other side of sources that can be tapped for energy
there is hydroelectricity which involves the turning of
turbines using the kinetic energy of flowing water, either by
damming a river or by creating a hydroelectric farm off the
coast. The disadvantage of hydroelectric power is the
necessity of water and the impact of a dam on river fauna.
Wind farms also have an effect on avian population. These
too must be constructed in areas of strong winds. The IEEE
code ethics takes issue with environmental impact on animals
here too [4].
Concentrating Solar power plants require do not the
combustion of fossil fuels, nor do they have the issue of
radiation emissions that nuclear energy sources suffer from.
The only requirement of a solar power plant is high intensity
sunlight found in near tropical areas. However, heating water
to be constantly vaporizing into steam requires more than the
sun shining on it, it requires the redirection of the energy
produced by the sun from several spots to a single point. To
heat a storage medium to temperatures exceeding 500 oC
requires even more, as the storage medium will lose heat as it
kept so that it can be used when the sun is obscured [6].
Renewable Energy Laboratory in their 2013 report on the
subject recommends the construction of large plants in largely
unpopulated areas that receive near constant daytime sunlight
like the Mojave Desert in Nevada [7] These regions, far from
any population center, would cause minimal damage were
there major accidents. Safety is paramount in ethics [8]. These
areas are flat, minimizing difficulties in designing a support
infrastructure that does not interfere with people’s daily
goings and have a large amount of space on which we can
construct the systems necessary for a solar power plant. A
strong maintenance infrastructure is important. If there is an
issue with generation and the plant needs to be shut down for
any reason, the length of the blackout is shortened. A strong
power system that can support a large area is useless if it only
works some of the time. The situation can be compared to the
issues with the Intel Pentium Chip in 1994 in which the chip
would make errors in calculation. Intel’s response was to offer
replacements to those who could demonstrate that they
needed a replacement chip for their applications of the device.
This was considered too little, as the flaw was unpredictable
and thus no one could know that they would need a new chip
[9]. Similarly a power system must be designed so that it can
be trusted as reliable. The citizenry should not have to worry
that their electricity will cut out any moment.
COMBATING INNEFICIENCY
As previously stated, the efficiency of a concentrating
solar power plant maxes near 20% [1]. In order to produce the
large amounts of energy necessary for powering a settlement,
the plants must be vast in size. In large open spaces like
deserts and plains, the view of the sun is unobstructed except
during night time and cloudy times. Being out of the way,
plants in empty regions like these are fully capable of
expanding outward in ways that minimize shading. Shading
means that heliostats are too large and too close together,
which causes them to block each other’s line of sight with the
sun or the target to which they are reflecting light. To show
how much unused space is required refer to Figure 2.
THE ISSUE OF SIZE
While Concentrating Solar Power Plants have the
advantage of lack of emission, carbon or radioactive, there is
the issue of size. For their output, solar power plants of any
kind require a significant plot of land dedicated to their use.
Were a solar plant to be constructed near populated areas, the
construction would displace a portion of the population that is
not insignificant. To resolve the issue of land, the National
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Vincent Antoine Verret
FIGURE 2 [3]
The Gemasolar Solar Power tower plant in Seville,
Spain.
Parabolic Trough plants take much more room individually,
as shown in Figure 3.
FIGURE 3 [3]
Andasol 1 (foreground) and Andasol 2 (background) in
Andalusia, Spain
Gemasolar is solar power tower in in Spain, operated by
Torresol Energy. It has a net energy output of 17 MW day and
night. This is because Gemasolar makes use of a technology
called Thermal Energy Storage. This allows storage of the
energy captured in a nonelectric format. The concept of
thermal energy storage revolves around directing the solar
energy to a Heat Transfer Fluid that can be kept at high
temperatures with insulation. When the stored energy is
needed, the heat is then transferred to water which then
evaporates and drives the turbine [6]. This design allows
energy to be conserved and dispatched as needed to the power
grid. By using solar power as a singular energy source, energy
facilities can be condensed in size, as no ancillary energy
sources are needed.
There are two kinds of Concentrating Solar Power plants
that use Thermal Energy Storage. Gemasolar is a Solar Power
Tower. Solar Power Towers dispense with a separate Heat
Transfer Fluid and uses the energy storage medium as the heat
transfer fluid. This means it spends less time flowing and thus
conducts less heat into the piping vessels. While Solar Power
Towers are more efficient than their alternative, the Parabolic
Trough plant, they have a limited size, as there is a
temperature at which the heat storage medium can no longer
retain the energy it absorbs. This means that excess heliostats
will waste resources, as the energy they redirect to the storage
medium is immediately lost as radiated heat [1] [3]. The other
type of Concentrating Solar Power plant, the Parabolic
Trough, does not redirect energy directly to the storage
medium. Parabolic trough plants have row upon row of
parabolic heliostats that each have a separate target. They
reflect sunlight into a pipeline that runs above the heliostats
carrying the heat transfer fluid. The heat transfer fluid’s flow
is split so that some goes to heat the storage medium, while
the rest goes to a heat exchanger to boil water and turn the
plant’s steam turbine. This means that additional heliostats
correspond to separate pools of heat transfer fluid. Any excess
heat can be immediately used instead of radiating from the
storage medium. Though they have a much higher capacity,
CONCLUSION: THE CHOICE IS
CONCENTRATING SOLAR POWER
With the world’s dependence on fossil fuels and natural
gas, the environment is at risk of being irreversibly changed
by climate change. The greenhouse gases emitted by the
combustion of fuels are causing the atmosphere of the Earth
to be heated up. This heating is altering the landscape of the
planet. Sea levels are slowly rising and the Polar Ice Caps are
melting, endangering many kinds of arctic animal species.
The temperatures of Earth’s seas are also rising, killing of
various kinds of ocean life. To avoid this, we as a society must
work to design a more ethical means of powering our
machines. A way that does not endanger the lives of humans
when they malfunction. Nuclear plants, while efficient,
currently endanger lives with their radiation when there is a
major malfunction. Wind resources require a very significant
land commitment and require a windy area to generate enough
electricity. Hydroelectric plants affect water life where they
are built. The use of Concentrating Solar Power with Thermal
Energy Storage technology allows us to generate electricity
even when the source of the energy is no longer present. It
beats back solar energy’s greatest downfall and provides a
clean, renewable source of energy. The only negative impact
of building a solar plant is that the land on which it is built
cannot be used for something else [7]. Solar Energy provides
an ethical renewable energy resource that endangers no one.
References
[1] V. Quaschning. (2009). “Renewable Energy and Climate
Change.” John Wiley & Sons. (Print book). p. 157-158
[2] K. Lovegrove, W. Stein. (2012). “Woodhead Publishing
Series in Energy, Volume 21: Concentrating Solar Power
(CSP) Technology: Principles, Developments and
Applications.” Woodhead Publishing. (Print book). p.16-64
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Vincent Antoine Verret
[3] R. Dunn, P. Hearps, M. Wright. (2011). “Molten-Salt
Power Towers: Newly Commercial Concentrating Solar
Storage.” Proceedings of the IEEE. (Online Article).
http://ieeexplore.ieee.org/xpls/icp.jsp?arnumber=6035949
[4] “Institute of Electrical and Electronics Engineers: Code of
Ethics” http://www.ieee.org/about/corporate/governance/p78.html
[5] C. Fleddermann. (2000). “Engineering Ethics Cases for
Electrical and Computer Engineering Students.” IEEE
Transactions
on
Education.
(Online
Article).
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=8
65202
[6] S. Kuravi, J. Trahan, et al. (2013). “Thermal energy
storage technologies and systems for concentrating solar
power plants.” Progress in Energy and Combustion Science.
(Online
Article)
http://ac.elscdn.com/S0360128513000026/1-s2.0-S0360128513000026main.pdf?_tid=6df1aeda-4038-11e3-8d0600000aab0f01&acdnat=1383009865_2fd65c60b5f435b4d0f
7d36eeabfacd9
[7] S. Ong, C. Cambpell, et al. (2013). “Land-Use
Requirements for Solar Power Plants in the United States.”
National Renewable Energy Technical Reports. (Online
Article). http://www.nrel.gov/docs/fy13osti/56290.pdf
[8] (2007). “National Society of Professional Engineers: Code
of
Ethics.”
http://www.nspe.org/resources/pdfs/Ethics/CodeofEthics/Co
de-2007-July.pdf
[9] D. Rummer. (2000). “Ethics in Electrical Design.” EC&M
Electrical Construction & Maintenance. (Online Article).
http://web.ebscohost.com/ehost/detail?vid=3&sid=661c2df0
-4f76-4c7d-b8b810854fdbbab1%40sessionmgr114&hid=108&bdata=JnNpd
GU9ZWhvc3QtbGl2ZQ%3d%3d#db=mth&AN=3830334
ADDITIONAL SOURCES
(2012). “Concentrating Solar Power.” Solar Energy Industries
Association.
(Online
Blog).
http://www.seia.org/sites/default/files/cspfactsheet120223144940-phpapp01.pdf
R. Sitch. (1997). “The Castle.” Miramax Films. (Film).
ACKNOWLEDGMENTS
I would like to thank: Chandler Campbell, for keeping me
awake long enough to write this paper; and Sawano Hiroyuki,
for composing the soundtracks I listened to while writing.
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