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 EnergyKinetic

PotentialChemicalNuclear

HeatGravitational

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 energyKE = ½ m v2

Potential energyPE = m g h

½ m v12 + m g h1 = ½ m v2

2 + 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

PowerPower 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 contains150 Cal = 150,000 cal =

0.150 kWhor

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) – 61.25 kWh/month (735 kWh/year)

Energy DensityHow 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 Car

GasolineEmissions 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. GasolineCars 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 CO2, 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: GeothermalPumps 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 reservoirDisplacement of animals and

other organisms

Advantages:

Controls water flow Fairly consistent energy

supply

Understanding Energy: Wind/Tidal PowerGenerates 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.

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?

How much energy does the US consume?

Energy Information Administration (EIA)

CO2 EmissionsNuclear 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.