Sources of Energy: Student Learning Goal The student will be able to describe a variety of renewable and non-renewable sources of energy and identify the strengths and weaknesses of each. (E3.5)

Sources of Energy SPH4C

Steam Turbines Both coal and nuclear power plants use steam turbines to turn their generators.

Steam Turbines Burning coal is an exothermic chemical reaction: it produces heat.

Coal: advantage The main advantage of coal is that it is the cheapest way of producing power. (China in particular has vast reserves.)

Coal: disadvantage The main disadvantage is that the burning releases pollutants: not only greenhouse gases such as carbon dioxide but also toxins such as mercury.

Coal: disadvantages Producing coal is also environmentally destructive. If coal is less than 70 m underground, it is removed by digging open pits:

Coal: disadvantages Or by removing mountaintops:

Coal: disadvantages A lot of coal is deeper underground, but mining it risks miners’ respiratory health and safety. The much-publicized rescue of the Chilean coal miners

Nuclear plants In nuclear plants, it is the radioactive decay of uranium that produces the heat to boil the water. The water that turns the steam turbine is in a separate loop.

Nuclear: advantage The main advantage of nuclear power is that it does not produce any pollutants.

Nuclear: disadvantages However, disposing of the nuclear fuel after use can be a problem because it is still radioactive.

Nuclear: disadvantages And mining uranium produces toxic, radioactive tailings (in Canada, half a million tonnes each year).

Hydro “Hydro” is short for hydroelectric, power generated by water turbines that turn the energy of the water flow into the rotational energy needed to power a generator.

Hydro Across Canada, hydro is the #1 source of energy (#2 in Ontario).

Hydro: Advantage Hydro plants are clean in that they do not emit pollutants, including greenhouse gases. The Sir Adam Beck generating complex.

Hydro: Explained Video by Ontario Power Generation: http://www.youtube.com/watch?v=cEL7yc8R42k

Hydro: Disadvantage But they still disrupt ecosystems because of the large dams required. Satellite view of the Three Gorges Dam in China, capable of generating 18.2 GW.

Dams The building of a dam results in flooding above the dam, displacing populations. Three Gorges before Three Gorges after

Dams Dams also create barriers to fish spawning (reproduction) areas. Bonneville Dam (Oregon) spawning ladder for salmon

Dams And the lakes formed above dams are vulnerable to sedimentation, when the silt that would flow downstream builds up in the lake.

Low-impact hydro Low-impact hydro dams are smaller and carefully planned to minimize disruption. 6% of Ontario’s energy now comes from these dams.

Water as a resource The careful use of water as a power source is particularly important because water is a resource itself.

Water as a resource Farming accounts for 70% of the world’s water use.

Water as a resource And as the world’s population grows and the demand for food grows, water use by farming will increase unless we use more sustainable practices, e.g. drip irrigation.

Solar Energy Solar energy is power generated by harnessing the energy of the Sun’s rays.

Active Solar Technology Mirrors and metal plates can be used to concentrate the sun’s rays to heat air or water. This is called active solar technology.

Solar Ovens Concentrating the Sun’s rays can even be used to cook food in solar ovens.

Concentrating Solar Techonology Mirrors can even be used to concentrate the Sun’s rays to heat water to drive generators. Solar Two, Mojave Desert, California

Solar panels Solar panels are most effective when they are angled toward the Sun (not necessarily straight up).

Solar panels Solar panels are most effective when they are angled toward the Sun (not necessarily straight up). The most effective angle will be equal to the latitude of the panel.

Solar Cells Solar panels contain photovoltaic cells. The cells are made of semi-conductors such as silicon. When light strikes the cell, an electric current is produced.

Solar = DC This current is direct current (DC). It can be stored in a rechargeable battery or be converted to AC (by an inverter) to be used by household appliances.

Solar = $ Houses with solar panels can sell energy back to the grid when they are producing more than is needed.

Disadvantages The disadvantages of solar energy are: The expense needed to build the panels It doesn’t produce energy at night (or as much when cloudy)