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 v2
Potential energy – stored energy
PE = m g h
Energy
Conservation of Energy
Kinetic energy
KE = ½ m v2
Potential energy
PE = m g h
½ m v12 + m g h1 = ½ m v22 + m g h2
½ m v12 + m g (0) = ½ m (0)2 + m g h2
½ m v12 = m g h2
v12 = 2 g h2
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!
Not an endorsement of Coke products!
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 = 0.150 kWh
or
630,000 J
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
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) – 61.25 kWh/month (735 kWh/year)
The United States uses ~4,000,000,000,000 kWh per year
We have to generate it somehow.
Energy Density
How energy sources compare!
What is interesting about this?
Understanding Energy: TNT vs. CCCs
Chemical Reactions and energy transfer are key!
Transfers chemical energy to heat
quickly. This quickness produces gases
that explode.
Requires digestion, which is a slow
process, the chemical energy than has
to convert into heat and other
materials.
Understanding Energy: Batteries
Electrical energy storage – Requires massive storage units, which lowers the
energy density
While batteries contain 340 times less energy than their weight in gasoline, they
provide a unique opportunity for portable devices.
Understanding Energy: Gasoline
Similar to TNT, Gasoline
converts chemical energy to
explosive energy and heat.
However, gasoline needs air to
do this.
Electric vs. Gasoline
Cars Edition
Telsa Model S
Chevy Cruz
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:
Emissions
Electric Car
0.23 lbs./MJ (Coal)
Gasoline
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.
Understanding Energy: Hydrogen Fuel
Combines hydrogen and oxygen to produce energy and water
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.
Hydrogen cannot be found.
It has to be made!
Electrolysis makes hydrogen
and oxygen from water.
Hyundai Blue
Understanding Energy: Uranium
Fission reactions break apart uranium to produce energy and lighter
radioactive elements
Uranium has a huge energy density (30 million times that of TNT)
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
Similar to a nuclear power plant, coal and natural gas plants burn their fuel to
boil water and turn a turbine.
Both generate a considerable amount of CO2, but they produce the most energy for
the United States.
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
Takes advantage of the energy produced by the fission of Uranium in a
controlled environment.
Nuclear power has minimal waste, but that
waste is radioactive for 1000s of years.
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/m2
~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 CO2
emissions are not stopping anytime soon.
Solar has wonderful possibilities, but needs to become more cost effective and efficient.
How much energy does the US consume?
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)
CO2 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 CO2 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.