- 2070 - Computer
Memory and Solar Cells. Nanowires will be
the next jump in solar cell efficiencies. Atomic level memory storage could radically
change our computing devices.
Both of these
solid state devices, photovoltaic and LEDs, are benefiting from the new nano
technology. Where will our needed energy
efficiency come from?
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- TO
LEARN MORE, CLICK ON ADDRESS BELOW:
FEEDBACK ENCOURAGED
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----------------------------- 2070 -
Computer Memory and Solar Cells.
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- In
the never-ending quest to improve computing technology, engineers have found a
way to store data on a single atom. A
hard drive today takes about 100,000 atoms to store a single bit of data -- a 1
or 0. Today, you can fit your personal
music library into a storage device the size of a penny. Using atomic level storage
you could fit Apple's entire music catalog of 26 million songs onto the same
area.
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- Atomic-level
storage could radically change our computing devices. A smartwatch or ring
could carry all your personal data, or businesses could keep potentially useful
information that today they can't currently afford to preserve. Storing lots of
information is important for artificial intelligence, which has a voracious
appetite for data used to train machine-learning systems.
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- Richard Feynman, said in a 1983 talk about the
possibilities of quantum computers that work at atomic scales: "We can in
principle make a computing device in which the numbers are represented by a row
of atoms, with each atom in either of the two states,"
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- To
make atomic storage practical we would need to make atomic-scale storage
economically manufacturable, fast at reading and writing data and stable enough
to store data for long periods of time
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- We
can store a bit of data on a single atom, but the scanning tunneling microscope
that is needed to read it is vastly larger. We use a single atom of the element holmium
carefully placed on a surface of magnesium oxide. Then a special-purpose microscope using a tiny
amount of electrical current is used to
flip the atom's orientation one way or the other, corresponding to writing a 1
or 0. We read the data by measuring the atom's electromagnetic
properties.
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- The
last big transformation in storage was the shift from the spinning magnetic
platters of hard drives to flash memory, chips that can read and write data
faster and that have no moving parts to wear out. Your phone and faster PCs use
flash memory that has improved through 3D stacking technology to add new layers
to memory chips.
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- A
promising successor to flash could be resistive random-access memory (ReRAM),
which could store data more densely than flash by changing how well a tiny
metallic filament conducts electricity.
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- It is not just
memory cells we need solar cells to power us into the 25th century. Looking out to the year 2050 here are the problems we will be facing:
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1. Energy
2. Water
3. Environment
4. Poverty
5. Terrorism
6. Disease
7. Education
8. Democracy
9. Population
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- In this list
Energy is the number one problem we will face.
Last year the world used 14,500,000,000,000 watts of power. Most of this energy is generated using gas
and oil. Only 0.5% of our energy comes
from solar, wind, or geothermal.
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- In the year
2050 we will be using somewhere between 30,000,000,000,000 watts and
60,000,000,000,000 watts of electricity.
By that time we will need to be generating 45% of our energy using
renewable sources. The best solution is
to get it from the Sun directly.
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- The Sun gives us 1,360 watts of energy for
every square meter of our surface. The
land surface area of Earth is 1.29*10^14 m^2 for a total energy input of
165,000,000,000,000,000 watts, 174,000 terawatts, and we only need 60 terawatts
by 2050. So, there is plenty of energy
there for the taking.
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- The United
States gets on average 200 watts per square meter of useable energy. Photovoltaic cells convert photons into
electricity directly. Today,
photovoltaic cells range in efficiency from 5% to 30%.
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- If we assume
that solar cells only give us 10% efficiency the US would still gain 20 watts /
m^2 from the Sun using solar cells. The
US uses 3.2 terawatts out of the world’s 14.5 terawatts. That amounts to 22% of the world’s
energy. The US would need 1.6*10^11
meters^2 of solar cells to generate that 3.2 terawatts of energy. That is 1.7% of the US land surface, about
the size of the state of Washington.
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- If we had six
of these large solar panels placed around the world it would give us a total of
19 terawatts of power, enough for the whole world that is only using 14.5
terawatts. The US has over 300 million
people. Counting homes and businesses
there are probably 400 million roof tops.
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- Assume the
average roof top can hold a 10 x 30 meter solar panel. That would total 1.2*10^11 m^2 of solar
panels on roof tops. This is close to
the 1.6*10^11 m^2 that we need. If we
can increase solar cell efficiency from 10% to 11% that would more than cover
energy needs for the US. Some
semiconductor solar cells are already 30% efficient. The problem is they are so expensive they can
only afford to use them on satellites and space craft.
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- This gets us
to the heart of the problem. Solar cells
are too expensive. It costs $30,000 to
put solar panels on the roof of your house.
On 400 million roofs that would be $12 trillion , even bigger than the
US National Debt. Today, other sources
of energy are so much cheaper:
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----------------------------------------. Total lifetime
cost per kilowatt hour:
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- Coal 1-4 cents
- Natural
Gas 2.3 - 5
- Oil 6 - 8
- Wind 5 - 7
- Nuclear 6 - 7
- Solar 25 - 50
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- In 2004 the
US, solar, wind, and geothermal energy only represent 0.5% of the energy
generated. 86 % comes from coal and gas
(2004: 85.65 / 99.74 total quadrillion
BTU)
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- What about
nuclear. The US has 103 nuclear
plants. Each producing 1,000,000,000
watts of electricity. A total of 0.1
terawatts. We need 3.2 terawatts, or
3200 nuclear plants. We have to build 3,100
more plants. If we built one nuclear
plant each week it would still take us 60 years to build them all. This is not likely to happen. Nuclear is providing 8% of electricity we
consume (8.23 quadrillion BTU) and is generating 20% of electricity production
in the US.
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- Learning how
to make solar cells cheaper seems an obvious way to go. If we could reduce the production cost by a
factor of ten, to 2.5 - 5 cents it would become one of our most practical
sources of energy.
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- If you
operate a solar cell backwards it becomes a light emitting diode, put
electricity in and get light out. A lot
of the electricity generated in the US is used to produce light, 22%. LEDs can be 10 times more efficient than
incandescent light bulbs:
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- Incandescent ------------------ 5 % Efficiency
- Fluorescent
------------------ 25 %
- Electric
Discharge -------- 30 %
- White
LED ------------------- 50 %
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- If we can get
LED bulbs produced as cheap as incandescents we can reduce our energy
consumption by 20%.
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- Both of these
solid state devices, photovoltaic and LEDs, are benefiting from the new nano
technology. Nanowires that are 1/1000
the diameter of the human hair, 50 nanometers diameter, are grown on the cell
substrates. When photons hit the
semiconductor of solar cell the photon is absorbed and an electron is
released.
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- Using
nanowires to traverse the cell the electron flows the length inside this single
crystal. The electron is quickly and
efficiently piped to the cathode of the circuit. Without nanowires impeded the electron would
have to bounce and jump from atom to atom throughout the semiconductor before
reaching the cathode. The nanowires
offer a significant improvement in light - electricity conversion efficiency. The same efficiencies happen when in reverse
the electron travels through a semiconductor to generate a photon.
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- The
manufacturing process is cheap. The
nanowires are grown as single crystals on the substrates in a wet process like
growing grass. None of the traditional expensive semiconductor processes are
used. If these processes become perfected we may see solar cells costing 10
fold less than they cost today.
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-------- Footnotes ---------------------------------------------------
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- (1) - Surface area of the Earth = 4*pi*radius^2 =
4*pi*(6.368*10^6 meters)^2 = 5.11*10^14 meters^2. Assume 25% of the Earth is land then 1.29*10^14
meters^2 * 1,360 watts / m^2 = 173,800 * 10^12 watts. 174,000 terawatts reaches our land mass.
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- (2) - 1.6*10^11
m^2 =
61,780 miles^2 and the state of Washington is 66,544 miles^2. A solar panel 93% the size of Washington
State. So, we would only have to
sacrifice one state to provide all the energy needs for the other 49
states. Just cover the state of
Washington with solar cells that are 10% efficient. Of course, Kansas would probably be a better
choice, they get more sunshine year round.
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------ “Jim Detrick” -----------
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------------------------- Thursday, April 19,
2018 --------------------------------
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