-
-
-------------------- 2622 - NANOTECHNOLOGY - solar cells from nanowires?
-
- I let my wife solve all the daily problems. I only work on the big problems, like how to solve the world’s energy needs in the next three decades. Here is the solution I came up with. Our feedback is encouraged.
-
- Looking out to the year 2050 here are the top 10 problems we will be facing:
-
-------------------------------------------- 1. Energy
-------------------------------------------- 2. Water
-------------------------------------------- 3. Environment
-------------------------------------------- 4. Poverty
-------------------------------------------- 5. Terrorism
-------------------------------------------- 6. Disease
-------------------------------------------- 7. Education
-------------------------------------------- 8. Democracy
-------------------------------------------- 9. Population
-
- In this list Energy is the number one problem we will face. In one year the world uses 14,500,000,000,000 watts of power. Most of this energy is generated using gas and oil. Only 1 % of our energy comes from solar, wind, or geothermal.
-
- 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. 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 174,000,000,000,000,000 watts, 174,000 terawatts, and we only need 60 terawatts by 2050. So, there is plenty of energy there for the taking.
-
- 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, three times more than we will need in 2050.
-
- The United States surface area gets on average 200 watts per square meter of useable energy. Photovoltaic cells convert photons into electricity directly. If we cover the surface area with solar panels, how much surface area would it take? Today, photovoltaic cells range in efficiency from 5% to 30%.
-
- 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.
-
- 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.
-
- 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 today.
-
- The US has over 300 million people. Counting homes and businesses there are probably 400 million roof tops. 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 from roof tops alone. 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.
-
- 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. If you have $30,000 cash you can put it into an investment, collect interest, and give the $125 per month to PG&E. Today, other sources of energy are so much cheaper (total lifetime cost per kilowatt hour):
-
--------------------------- Coal 1-4 cents
-
--------------------------- Natural Gas 2.3 - 5
-
--------------------------- Oil 6 - 8
-
--------------------------- Wind 5 - 7
-
--------------------------- Nuclear 6 - 7
-
--------------------------- Solar 25 - 50
-
- Today, in the US, solar, wind, and geothermal energy only represent 0.5% of the energy generated. 86 % of our energy comes from coal and gas (2004: 2.84 /3.3 total terawatts)
-
- 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 (0.27 terawatts) and is generating 20% of electricity production in the US.
-
- 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.
-
- There is another benefit to cheap solar cells, 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:
-
----------------------------- Incandescent 5% Efficiency
-
----------------------------- Fluorescent 25
-
----------------------------- Electric Discharge 30
----------------------------- White LED 50
-
- If we can get LED bulbs produced as cheap as incandescents we can reduce our energy consumption by 20%. You are already seeing these LEDs in stop lights and auto tail lights.
-
- Both of these solid state devices, photovoltaic and LEDs, are benefiting from the new nanotechnology that is in the works. Nanowires that are 1/1000 the diameter of the human hair, 50 nanometers diameter and 300 nanometers long, are grown on the cell substrates.
-
- When photons hit the semiconductor of solar cell the photon is absorbed and an electron is released. Using nanowires to traverse the cell the electron flows the length of the semiconductor inside this single crystal. In this way, the electron is quickly and efficiently piped to the cathode of the circuit.
-
- Without nanowires the electron would be impeded inside the semiconductor having to bounce and jump from atom to atom before reaching the cathode. In this way 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.
-
- The major benefit is that 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 nanowires production is perfected we may see solar cells costing 10 fold less than they cost today.
-
- The energy consumption in quadrillion BTUs.
-
- To convert to terawatts, for example, US consumption is 100 quadrillion BTUs in 2004. 100*10^15 BTU.
-
- 1 kilowatt hour = 3412.14 BTU.
-
- 29,000 *10^12 / 8,760 hours/ year = 3.3 terawatts consumed in the year 2004.
-
- And then there is the conservation of energy. That is another topic but should likely be critical if we are going to have time to invent these other solutions.
-
-------------------------------------------- Other Reviews available:
-
- 2621 - NANOTECHNOLOGY - in quantum mechanics.? - Today nanotechnology is being used by countless universities and corporations to create products that will be entering the commercial markets, soon. Nanotechnology will be found in information technology, communications, biology, medicine, and energy. You will likely see the changes in biology and medicine first.
-
- 1987 - nanotechnology from chemistry to biology. - Nanotechnology from Chemistry to Biology. The computer technology is advancing into smaller and smaller architectures. Where is the limit? What are new alternatives that can extend past the limit?
-
- 1230 - Nanotube weirdness of the very small.
-
- 851 - The nanotube radio.
-
- February 18, 2020 627 2622
----------------------------------------------------------------------------------------
----- Comments appreciated and Pass it on to whomever is interested. ----
--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email feedback, corrections, request for copies or Index of all reviews
--- to: ------ jamesdetrick@comcast.net ------ “Jim Detrick” -----------
- https://plus.google.com/u/0/ -- www.facebook.com -- www.twitter.com
--------------------- Tuesday, February 18, 2020 --------------------
-----------------------------------------------------------------------------------------
No comments:
Post a Comment