Chapter 3C Main ideas

1. Overview of Energy Resources

Electricity is the largest energy sector in the U.S. and electricity productions is dominated by non-renewable resources. Renewable resources are responsible for less than a quarter of all electricity production. The basic method of generating electricity relies on spinning a turbine to generate electricity. What causes the turbine to spin varies among energies with fossil fuels, nuclear, biomass, and geothermal all generating steam; hydroelectric, tidal, and wave using flowing water; wind using flowing air; and solar generating energy directly from the sun with no turbine involved.

2. Steam Powered Electricity

Fossil fuels, nuclear, biomass, and geothermal energy all create steam to power a turbine. Fossil fuels are created by the burial and alteration of land plants (coal) and ocean organisms (oil and gas). Biomass burns unaltered plant material and is therefore less energy dense than the altered plant material in coal, but renewable. Nuclear energy relies on the fission of uranium atoms and is very energy dense but non-renewable. Geothermal energy uses the immense amount of heat from inside the Earth.

3. Water Powered Electricity

All water powered electricity is renewable. Hydropower and tidal energy rely on flowing water to spin turbines. With hydropower this is water either held behind a dam or flowing through a turbine without a major dam as is the case with run-of-river hydropower. Tidal energy can rely on a similar dam design or can use tidal stream technology, which operates much like an underwater wind turbine.

Wave power is slightly different, in that instead of having a turbine to spin, hydraulic pistons are used in many wave energy converters. The rocking motion of waves causes the pistons to be pushed back and forth to generate electricity.

4. Wind Powered Electricity

Wind is generated by unequal heating and cooling of the Earth. This drives the movement of air masses from high to low pressure areas and this movement is captured by wind turbines. Wind turbines can be used on land or offshore in oceans and lakes where wind action is more constant. Offshore turbines are not as space limited and can also be bigger allowing an individual turbine to generate more electricity.

5. Solar Powered Electricity

Solar photovoltaic cells use energy from solar photons to cause electrons to flow. The flow of electrons is electricity and can be harnessed. Solar energy used to be the most expensive form of electricity and has now become the cheapest.

6. Energy Resource Comparisons

All energy sources have advantages and disadvantages associated with them. Decisions on which energy sources to fund require weighing the pros and cons of each to minimize potential impacts. Fossil fuels are overall highest in greenhouse gas emissions, highest in death rates, and lowest in job creation.