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-------------------- 2480 - ENERGY - Conservation of Energy
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- Over consumption of Energy is far outstripping our supply. Alternatives are coming on line too slow to keep up. It all boils down to the laws of physics.
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- In the Review 646 we learned that Energy can never be destroyed. It can be changed into Mass or into other forms of Energy but it is always in the Universe at the same total amount. Next we learned that Entropy always increases in a system, meaning that Energy is always seeking its lowest level and the atoms are always gravitating towards randomness.
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- Entropy in Thermodynamics prevents ever getting something for nothing in our Universe. There will never be a perpetual motion machine built. We also learned in the 646 Review that it is the Symmetry in the laws of physics that creates the Laws of Conservation, including the Law of Conservation of Energy.
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- Energy is a Force acting in a Space. Energy is Force acting over a Distance, E = F*dx. Space and Distance and Motion are always Relative. You must have a reference frame in order to measure them.
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- Force is the product of mass and acceleration, F = m*a, in units kilograms * meters / second^2. If we multiply Force by Distance we get the amount of Energy it took to put a mass in motion. Energy is units of kilograms * meters^2/second^2. Note the meters is meters^2, meters times meters. The name given to kg*m^2/sec^2 is “Joules” of Energy.
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- In the last Review 646 we learned that a 1000 kilogram car traveling on a level highway at 30 meters/second has 450,000 Joules of Energy. ( This is a 2,205 pound car traveling at 60 miles per hour.) The Kinetic Energy of a 1000 kg car traveling 30 meters/second = ½ * 1000 kg * (30 m/s^2) = 450,000 Joules of Energy, KE = ½ m *v^2.
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- The energy loss in 10 seconds slowed the car to 50 mph, or 25 meters/second when the foot was off the accelerator and the car coasted down the highway until it reached the slower speed. Kinetic Energy = ½*1000 kg * (25 m/s^2) = 312,500 Joules of energy. The difference in energy is 137,000 Joules.
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- This loss of energy tells us how much energy it takes to keep the car running at a velocity of 60 mph. The energy loss took 10 seconds, so the energy / second = 13,700 joules/second, or 13,700 watts (A watt is a Joule per second). Traveling at 60 mph is 1/60 miles per second.
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- So, we are consuming 13,700 Joules/second * 60 seconds/mile, or 822,000 Joules per mile. A gallon of gas contains 110,000,000 Joules of chemical energy. If the car was 100% efficient we would be getting 110,000,000 Joules/gallon / 822,000 miles/Joule = 134 miles / gallon.
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- We checked our mileage and we are actually getting only 19 miles / gallon. Therefore, our car is 19 mpg / 134 mpg = 14 % efficient. This was on a level highway in a straight line, usually car efficiency is much less than 14%.
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- A car is a big mass and 60 mph is an average speed. A particle accelerator can accelerate a pulse of 3,000,000,000,000 protons (The same number in an average living cell) to a speed of 99.9995% the speed of light. We need to use the theory of relativity to calculate the energy at these speeds but remarkably it works out to be about the same as the car, 450,000 Joules of Energy.
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- The Kinetic Energy of a big thing going slow can be the same as a small thing going fast.
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- Our bodies are engines too. We burn food instead of gasoline in order to sustain energy needed for living. Each person eats about 2,000 Calories per day. There are 4,200 Joules of energy in a Calorie.
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- That means each person consumes 8,400,000 Joules of energy each day. There are 86,400 seconds in each day. Therefore, in Joules/second, or watts, each person burns about 97 watts per day. In other words, every person walking around is burning about the equivalent of a 100 watt light bulb.
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- However, each person consumes much more energy than that 100 watts of food. Every house uses electric energy to provide lights, refrigeration, heat, television, cooking, etc. On average in the American household 3,000 watts per day / person is consumed.
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- That is just at home, if we include energy at work and at all the stores we shop, and movie theaters we attend, etc, this increases to 10,000 watts per day. 10,000 watts per day in America is about 5 times the world average.
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- The U.S. consumes 10^17 BTU’s per year, in year 2004. One BTU is 1,000 Joules. So, that is 10^20 Joules per year. There are 3*10^7 seconds in a year. And, 300 million people in the US. So, the average American is consuming (10^20 Joules/year) / (3*10^7 seconds/year) / (3*10^8 people) = 10,000 watts of energy per person.
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- The Sun sends us about 100 watts of energy per square meter of level ground on Earth, on an average sunny day. A solar panel of 300 square meters, the size of the average house roof, that was 10% efficiency could provide 100 watts/meter^2 * 300 meters^2 = 3,000 watts, which is what is needed for the average American household.
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- However, solar cells are not even 10% efficient at this time, more like 2% efficient and 25 cents per cell. When they become 10% efficient and 2 cents per cell they will become a practical energy alternative for most households.
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- Hydroelectric power is another alternative that relies on the renewable energy of rains, or the tides. If California would construct a tidal basin off the coast that was 1000 kilometers long and 10 kilometers wide, (621 miles long and 6.2 miles wide about the length of the California coast), then the incoming tides would fill the basin with sea water to a level of 1 meter.
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- The volume of the water would be 10^6 m*10*4m*1m = 10^10 m^3. Each cubic meter weighs 1000 kilograms, so the total tidal basin weighs 10^13 kilograms. The Potential Energy = mass * acceleration of gravity * height = 10^14 kilogram * meters / second, or 10^14 Joules of Potential Energy.
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- There are 10^5 seconds per day, so the energy in watts equates to 10^9 watts. If each person consumes 10,000 watts, all that work in building this tidal pool would only take care of 100,000 people. That is a town the size of Santa Rosa. That would take care of us but what would the rest of California do for energy?
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- How about nuclear energy? A small pebble bed nuclear reactor can produce 10^8 watts of power, enough for 10,000 people. A town the size of Santa Rosa would need 10 nuclear reactors. That is not likely to happen. We could put all 10 nuclear reactors in Sebastopol and pipe the energy over to Santa Rosa. That is not likely to happen either.
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- Sebastopol is a nuclear free zone so they would recommend using wind power instead since they are against nuclear power. Windmills 100 meters (300 feet) tall can produce 10^6 watts of power from a wind speed of 10 meters / second ( 20 mile per hour wind ).
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- Santa Rosa would need 100 of these wind mills across the tops of the hills in Sebastopol. Or, maybe, we could put one hundred 300 foot windmills off the coast of Bodega and pipe the energy in from there. We might need a few extra windmills due the energy loss in the transmission line to Santa Rosa.
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- Nuclear fusion is another alternative. The Sun and all the stars generate their energy using nuclear fusion. Unfortunately, that technology is another 20 to 50 years off before it is even feasible as a practical alternative for us Earthlings. Physicists are trying hard, but fusion is very difficult to produce and control. It will take several technology breakthroughs before it happens.
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- OK, let’s just go back to the basics. Let’s burn wood. Trees are excellent solar collectors. They look good and help our environment. They harness the energy of the Sun and put it into cellulose. Trees can give us about 1 watt of wood burning energy per square meter of forest. Since the Sun is providing about 100 watts per square meter to the trees, that amounts to only 1% efficiency in burning wood. Plus, wood burning , like coal and oil, gives us pollution in the air and water to deal with.
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- Let’s face it Earthlings, we are going to probably need every one of these alternatives simultaneously up to the maximum of their current capabilities to replace oil and gas as our energy sources.
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- Not, only that, it should be obvious that we must learn how to conserve energy. We must reduce our energy consumption per person by dramatic amounts. Remember, we are 500% higher in energy consumption than the world average.
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- Technology can help but education is probably more powerful in the short run. Ironically, education is what will solve our technology challenges in the long run as well. Someone in school today has to invent and perfect new alternative energy sources.
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- I hope this review on the conservation of energy helped in this education. Doing the math is an education in itself. I enjoy the math. Just wish it had a better story to tell.
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- November 11, 2019 2480 647
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--------------------- Monday, November 11, 2019 --------------------
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