Energy

Part 1 – Types, Usage, and Projections

Definitions

Energy = the ability to do work Measured in joules

Power = work/ time Measured in watts = joules/second

Forms of Energy

Form Description

Mechanical Two types, potential (“resting energy”) and kinetic (“moving energy”)

Thermal Heat – the vibration and movement of atoms and molecules within substances

Chemical Stored energy in chemical bonds

Electrical Energy from the motion of electrons

Nuclear Energy stored in the nuclei of atoms

Electromagnetic Energy that travels by waves

Power and UnitsUnit or Prefix Description

Btu (British Thermal Unit)

>Amount of energy required to raise the temperature of 1 lb. of water by 1°F.

>Unit of energy used in the US (most other countries its joule)

>1 watt = 2.3btu/hr

Horsepower >1 horse power = 746 watts = 2,540 btu/hr

>primarily used in the auto industry

Kilo- > 1,000 or 103; 1kW = 103 watts

Mega- (M) >1,000,000 of 106; 1MW = 106 watts

Kilowatt hour (kWh)

>Unit of energy = 1,000 watt hours or 3.6 megajoules

> Commonly used for billing

Conversions – Sample APES problems Thorpeville is a rural community with a population of

8,000 homes. It gets electricity from a small, municipal coal-burning power plant just outside of town. The power plant’s capacity is rated at 20 megawatts with the average home consuming 10,000 kilowatt hours (kWh) of electricity per year. Residents of Thorpeville pay the utility $0.12 per kWh. A group of entrepreneurs is suggesting that the residents support a measure to install 10 wind turbines on existing farmland. Each wind turbine is capable of producing 1.5 MW of electricity. The cost per wind turbine is $2.5 million to purchase and operate for 20 years.

Conversions – Sample APES problems a) The existing power plant runs 8,000 hours

per year. How many kWh of electricity is the current plant capable of producing?

Conversions – Sample APES problems b) How many kWh of electicity do the residents

of Thorpville consume in one year?

Conversions – Sample APES problems c) Compare answers in (a) and (b). What

conclusions can you make?

Conversions – Sample APES problems d) Assuming the population of Thropeville

remains the same for the next 20 years, and that elecricity consumption remains the stable per household, what would be the cost (expressed in $ per kWh) of electricity to the residents over the next 20 years if they decided to go with the wind turbines?

Conversions – Sample APES problems e) What are pros and cons of the existing coal-

burning plant compared to the wind farm? (Hint: use information you calculated plus what you know about these forms of energy)

Conversions – Sample APES problems An electric water heater requires 0.30 kWh to

heat a gallon of water. The thermostat is set to 150°F. The cost of electricity is $0.20 per kWh. A washing machine with a flow rate of 6.0 gallons per minute runs four times each Saturday. Each time is runs it takes in water for a total of 15 minutes.

Conversions – Sample APES problems a) How much total water does the washing

machine use in one year?

Conversions – Sample APES problems b) Calculate the annual cost of the electricity for

the washing machine, assuming that 3.0 gallons per minute of the water used by the machine comes form the hot-water heater.

Thermodynamics

1st law: Energy cannot be created or destroyed.

2nd law: When energy is converted from one form to another, a less useful form results (energy quality). Energy cannot be recycled to a higher quality.

Energy consumption

Prehistory to industrial revolution – wood Industrial revolution to mid 20th century – coal Mid 20th century to today – petroleum

Natural gas and coal experience booms in later half of the 20th century due to technological advances

Energy consumption by Source

Energy consumption in the US US was self-sufficient until the late 1950’s

Then consumption began to outpace production leading to oil imports

What happened to change this?

Energy consumption by sector Industry > transportation > residential > commercial

Petroleum In 1998, net imports of oil surpassed the domestic supply US accounts for 25% of world consumption of petroleum

US Production vs. Consumption In US most energy comes from non-renewable sources Renewable = biomass, geothermal, hydropower, solar

energy, and wind energy

Commodity US Production US Consumption

Oil 18% 39%

Natural Gas 27% 23%

Coal 33% 23%

Nuclear 10% 7%

Renewable 9% 3.6%

Hydroelectric 5% 4%

US Energy

Commodity Consumption

Commodity % of total world usage

Oil 40

Natural Gas 23

Coal 23

Production By Sector

Sector %

Transportation 27

Industrial 38

Residential and commercial

36

Future Energy SourcesShort-term Fossil Fuels Most economic,

reliable, and realistic sources of energy are: Already have the

infrastructure and technology to acquire

Not the most Environmentally Friendly

Will run out of some day

Long-term Renewables Nuclear Need to develop

infrastructure and technology to make efficient Eg: charging stations for

electric cars and car batteries that can charge in minutes not hours