The Science of Energy

John

Course Notes

Lecture Series by Michael Wysession, Ph.D.
Professor of Earth and Planetary Sciences
Washington University

 

Energy and Human Civilization

The human demand for energy is increasing. There are many different energy sources, though no single solution on which is best. There is a cost and benefit for all energy resources. Energy affects the economics, politics and even some philosophical beliefs in human civilization.

 

Forms of Energy and Conversions

Some forms of energy:

  • matter
  • light
  • gravitational
  • motion (kinetic / potential)
  • nuclear
  • chemical
  • thermal
  • electromagnetic

Units of energy

  • Amount of Energy
    • joules
    • calories
  • Rate of Energy
    • watts
    • hp

 

Thermodynamics

  • Heat is the transfer of energy (a rate/flow of energy)
  • First Law of Thermodynamics = work lost in friction equals the amount of energy transferred as heat
  • Second Law of Thermodynamics = heat flows from hot to cold; aka entropy will increase (things will become more disordered as energy is dispersed)
  • Radiation = transmission of energy through electromagnetic waves
  • Convection = transfer of heat/energy through a material or medium. eg fire boiling a pot of water
  • Conduction = physical contact causing heat transfer. eg touching a hot object heats the finger tips

 

Electricity

  • A transfer medium for energy
  • Any energy source can be converted into electricity
  • Can travel long distances with little energy loss – highly efficient
  • Electricity can be re-converted into any energy source, thereby being able to power almost anything

Electricity uses the force of electromagnestism

  • gravity
  • electromagnetic force
  • strong / weak nuclear force

In the United States, the major sources for electricity are:

  • Coal 39%
  • Gas 27%
  • Nuclear 19%
  • Hydro 6%
  • Wind 4%
  • Biomass 2%
  • Petroleum 1%
  • Geothermal 1%

 

Chemical Energy

  • Chemical enegy is a type of potential energy as it is stored in the chemical compound. As the chemical bond is broken apart we extract the energy from it. The main types of chemical energy are:
    • Biomass – includes photosynthesis, fossil fuels, animal by products, plants (ethanol from corn)
    • Combustion – opposite of photosynthesis, it takes the chemical energy and converts to heat and light

 

Energy Sources

 

Coal

Coal provides about 28% of world’s total energy and about 40% for world’s electricity. Coal is from old plant organisms decomposed. There is an abundance of coal on the planet but the deposits that are easy to reach have been vastly used up. The remaining deposits are deeper and more costlier. At some point, the cost of digging up the coal is greater than its benefit.

Petroleum

This includes oil and gas. From organic material fossilized. Gas is generally the methane gas which recently has been easier to reach and efficiently extract due to fracking. Petroleum requires a refining stage, thereby increases cost. Also, petroleum leaked into the environment can be hazardous, thereby increases risk and cost.

Much of the oil is being mined from the big 5 Middle East countries as well as Canada, Venezuela and United States. Much of the natural gas is mined from Russia, Iran, Qatar and United States.

Nuclear

There are two types of nuclear power – nuclear fission and fusion. Nuclear fission is the breaking apart of atoms through chain reaction. It accounts for about 11% of the world’s electricity. Generally we use Uranium for this reaction, which has to be mined. Uranium ores are in far less concentration that coal or other energy sources.

Though fusion reactions have also been created and controlled, though at small scales, it has been very difficult to increase it’s efficiency. Generally we are only able to get back what we put in from these reactors. It is a much cleaner source of nuclear energy as the nuclear waste from fusion have half-lives of only a few decades whereas fission based waste can last thousands of years. Technology in this area continues to develop.

Solar

All energy sources actually come from the Sun except for nuclear, geothermal and tidal. Some ways we can convert sunlight into energy are:

  • Use photosynthetic organisms to convert sunlight into chemical energy
  • Photovoltaic panels that covert the sunlight directly into electricity using semiconducting materials. These material types are evolving quickly and we’re creating more efficient panels
  • Concentrated solar power (CSP) is using the sunlight to boil water which then runs a steam powered generator.
  • Stirling Engines – runs a thermodynamic cycle of air (instead of water) which cause a piston cylinder to expand thereby generating kinetic energy.

Wind Power

Use of wind turbines that turn a generator for kinetic energy. The turbines and propellers are constantly evolving as we increase the efficiency. The propellers work the same as an airplane using the Bernoulli principle in that blade shaped a certain way will allow the air to move through it while moving it.

Wind power relies on the meteorology and measuring / predicting wind patterns. There are factors such as global climate (Coriolis force) or Earth’s rotation that can affect these winds.

Hydroelectric Power

Hydroelectricity is ultimately a form of solar power as the sun drives the water cycle (sun causes evaporation, which causes the weather, which results in rains and ultimately runs the turbines). One of the drawbacks of hydroelectric power is the effect a dam may have on the ecology of surrounding environment.

Biofuels

This is a type of chemical energy – taking apart plant biomass into another form of energy such as ethanol/gasoline. Ethanol is currently the most popular and widely used bio fuel. It is a cheaper replacement to fossil fuels, though the efficiency is a bit less as there is cost involved with growing the bio fuel source (plants) and then harvesting/processing.

Geothermal

Energy from within the planet Earth. It is a type of thermo energy that is in abundance, but often difficult to tap as it is not widely available – depends on geographical location. This energy source is usually only found near highly active geothermal locations.

 

Energy Storage

 

Compressed Air

A type of potential energy as the decompression can create kinetic energy to turn a turbine. This generally has low efficiency as there is thermal loss during storage (compression).

Flywheel

Is winding up a flywheel and thereby another type of potential energy. This is very efficient however the cost of creating the flywheel is expensive.

Thermal

This relying solely on the thermodynamic energy. The efficiency depends greatly on the type of insulation, which can be costly.

Batteries

This is using a type of chemical energy and highly efficient. (Lithium ion, sodium sulfur, vanadium, etc). This is also a type of electricity as it controls the flow of electrons from one terminal to another (anode/negative to cathode/positive).

 

The Economics and Politics of Energy

 

Due to the high demand and limited supply of energy on this planet, there are many economical and political factors to controlling the energy sources and uses. For petroleum, the Organization of the Petroleum Exporting Countries (OPEC) highly control the exports of those resources. Governments also regulate the flow and storage through taxation or even military force. They can also create incentives or subsidies to direct the future of energy use, for example pushing for more efficient transportation vehicles. In the United States, government agencies monitor and can penalize individuals, groups or companies that may violate the policies or regulations.