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General Science 101 Chapter 1 - Energy and Power and the Physics of Explosions
Chapter 1: Energy and Power and the Physics of Explosions What is energy? Energy can be defined as the ability to do work. Energy must be conserved and cannot be created nor destroyed. This means that energy can transform into other forms (heat, chemical, mechanical, biological, etc.) To put it simply, energy makes the Earth go around and what allows us to exist!
Energy Types of Energy Kinetic Potential Chemical Nuclear Heat Gravitational Since energy is conserved, it must transform from one type to another. Kinetic energy – energy of motion KE = ½ m v 2 Potential energy – stored energy PE = m g h
Energy Conservation of Energy Kinetic energy KE = ½ m v 2 Potential energy PE = m g h ½ m v m g h 1 = ½ m v m g h 2 ½ m v m g (0) = ½ m (0) 2 + m g h 2 ½ m v 1 2 = m g h 2 v 1 2 = 2 g h 2
Power Power is the rate at which energy is used (energy over time). Power is measured in Joules per second (J/s) or Watt (W)
How to measure energy! We measure energy using different units. -In Chemistry and Biology, people use the calorie (cal) or kilocalorie (Cal). -1 Cal = 1000 cal. -1 Cal is equal to a food calorie This is amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius. -In Industries, people use the kilowatt-hour (kWh) -1kWh ~ 1000 Cal -In Physics, people use the joule (J) -1kWh = 3.6 million J One can of soda contains 150 Cal = 150,000 cal = kWh or 630,000 J Not an endorsement of Coke products!
How to measure energy! The average household uses 12,000 kWh of energy each year. That is equivalent to: ~80,000 cans of soda (~150 Cal each) ~120,000 bananas (~100 Cal each) ~2,000,000 grams of coal ~360 gallons of Gasoline The United States uses ~4,000,000,000,000 kWh per year We have to generate it somehow. 16 W bulb (on 10 hours) – 4.8 kWh/month (57.6 kWh/year) 100 W bulb (on 10 hours) – 30 kWh/month (360 kWh/year) Refrigerator – 36.7 kWh/month (440 kWh/year) Dishwasher – 41 kWh/month (492 kWh/year) Clothes Washer – 24.9 kWh/month (299 kWh/year) Electric Clothes Dryer – 74.7 kWh/month (896 kWh/year) Stove & Oven (self-cleaning) – kWh/month (735 kWh/year)
Energy Density How energy sources compare! What is interesting about this?
Understanding Energy: TNT vs. CCCs Chemical Reactions and energy transfer are key! Requires digestion, which is a slow process, the chemical energy than has to convert into heat and other materials. Transfers chemical energy to heat quickly. This quickness produces gases that explode.
Understanding Energy: Batteries While batteries contain 340 times less energy than their weight in gasoline, they provide a unique opportunity for portable devices. Electrical energy storage – Requires massive storage units, which lowers the energy density
Understanding Energy: Gasoline Similar to TNT, Gasoline converts chemical energy to explosive energy and heat. However, gasoline needs air to do this.
While electric cars run off of batteries, those batteries must charge and that power has to come from somewhere. This is typically a coal or natural power plant. Therefore, electric cars are not zero emission vehicles unless you charge them with a zero emission source (nuclear, solar, wind, etc.) The breakdown: Electric CarGasoline Emissions 0.23 lbs./MJ (Coal)0.16 lbs./MJ Cost per Mile$0.01$0.04 This ignores manufacturing costs and price of vehicle or emissions due to energy production. Electric vs. Gasoline Cars Edition Chevy Cruz Telsa Model S
Understanding Energy: Hydrogen Fuel Liquid Hydrogen gas has ~3 times more chemical energy per gram than gasoline. Sounds good…but! It is ~3 times less energy per gallon. 1 kilogram of hydrogen ~ 1 gallon of gasoline Compressed hydrogen gas has 6 times less. Combines hydrogen and oxygen to produce energy and water Hyundai Blue Hydrogen cannot be found. It has to be made! Electrolysis makes hydrogen and oxygen from water.
Understanding Energy: Uranium Uranium has a huge energy density (30 million times that of TNT) Fission reactions break apart uranium to produce energy and lighter radioactive elements Uranium takes advantage of chains reactions to break atoms and produce large amounts of energy. This is a achieved through the critical mass.
Harnessing Energy – The Steam Engine Since the 1800’s, Steam has been the easiest manner to transfer energy. - Boats - Trains - Power Plants It is just matter of how you heat the water.
Understanding Energy: Coal/Natural Gas Both generate a considerable amount of CO 2, but they produce the most energy for the United States. Similar to a nuclear power plant, coal and natural gas plants burn their fuel to boil water and turn a turbine. Uranium takes advantage of chains reactions to break atoms and produce large amounts of energy. This is a achieved through the critical mass.
Understanding Energy: Nuclear Power Nuclear power has minimal waste, but that waste is radioactive for 1000s of years. Takes advantage of the energy produced by the fission of Uranium in a controlled environment. Generation IV Reactors could revolutionize the nuclear power industry by using a lead convection cooled system.
Understanding Energy: Geothermal Pumps water deep into the ground where it is heated by the earth. Steam then travels up and pushes a turbine.
Understanding Energy: Solar Power (Concentrated) Collects sunlight and boils water to generate electricity through a turbine. These types of solar collector plants are very efficient, but require large amounts of area.
Understanding Energy: Solar Power (Panels) Solar panels use advanced materials to convert sunlight into an electric current 150 (cheap) – 400 (expensive) W/m 2 ~3000 sun hours per year (varies by place) 0.4 kW * 3000h = 1200 kWh/year for one panel Therefore, the average household needs approximately 10 panels to get 12,000 kWh per year. Assuming you buy the expensive ones!
Understanding Energy: Hydroelectric Uses river water to push a turbine and generate electricity. Possible environmental concerns: Impact of a reservoir Displacement of animals and other organisms Advantages: Controls water flow Fairly consistent energy supply
Understanding Energy: Wind/Tidal Power Generates power by having a turbine turned by wind or the tidal forces.
Cost of Energy Nuclear power is the cheapest, but public apprehension continues to hold the building of newer plants. Coal is still the work horse for the United States, China, and India, which means the CO 2 emissions are not stopping anytime soon. Solar has wonderful possibilities, but needs to become more cost effective and efficient.
The amount of energy used by each state divided by its population. Essentially, how much each person (on average) uses in that state. Millions of BTU per capita Energy Information Administration (EIA) How much energy does the US consume?
Energy Information Administration (EIA)
CO 2 Emissions Nuclear power is the cheapest, but public apprehension continues to hold the building of newer plants. Coal is still the work horse for the United States, China, and India, which means the CO 2 emissions are not stopping anytime soon. Solar has wonderful possibilities, but needs to become more cost effective and efficient. This will be covered more extensively when we look at Climate Change
Energy Take Aways Energy is defined as the ability to do work, which means it is critical for life. There are many ways to generate energy (Chemical, Mechanical, Solar, Atomic…). Most energy source include boiling water…a slight modification of a steam engine. Some sources are better than others, but the ability to store energy is one of our biggest challenges.