12.4 Sustainable Sources of Electricity (Pages 506-512) Homework: Page 512 # 5, 6, 8 Key Concepts (Page 512)

Renewable sources of energy can be renewed within a reasonably short period of time. In Ontario, the renewable energy sources that contribute to electrical energy are wind, hydroelectric, and solar energy.

Other renewable energy sources include waves, tides, biomass, and geothermal. Solar photovoltaic cells are semiconductor materials that generate a direct current when light shines on them.

Wind Power Description: When wind turbines spin, they turn an electric generator that produces electricity. Advantage: Most large turbines can generate a few megawatts of electrical power. The cost of running wind turbines is very low.

Disadvantage: The wind speed at any location may vary during the day. Some people think that wind turbines are noisy and spoil the view. Turbines can be a danger to birds and humans nearby.

Solar energy (2) Energy that is converted directly from the Sun into electricity through the use of photovoltaic materials that generate a direct current when exposed to light. Advantages: The fuel for solar energy is free. There is very little impact on the environment. The cost of solar energy is dropping as the technology develops.

Disadvantages: Solar energy systems are still quite expensive. Solar systems are quite inefficient. DC that is produced must be converted to AC for home use. Energy must be stored in batteries for use at night or on cloudy days.

Ocean waves Description: Used to generate electricity as they rise and fall, compressing an air column that drives a turbine connected to a generator. Advantage: Canada is currently investigating ways to generate electricity using ocean waves. Disadvantage: Limited by proximity to the ocean

Tidal energy Description: The rising and falling tides spin generators within dams constructed across inlets and produce electricity Advantage: Tides are predictable, unlike winds Disadvantage: Depends on proximity to the ocean, tides vary on a 15-day cycle & they only generate electricity for about 10 hours a day

Biomass energy Description: Energy that is generated from plant and animal material. Advantage: Plant matter (or bio fuels) can be burned to power generators & much less acid rain and no heavy metals emitted Disadvantage: Burning biomass still adds CO2 to the atmosphere but does not add any of the other chemicals found in fossil fuels.

Geothermal energy Description: Produced from naturally occurring steam and hot water that is heated by rocks and trapped under Earth’s surface. When pumped to the surface, the steam drives turbines to generate electricity. Advantage: Few emissions from geothermal plants, provide base-load electricity with low running cost

Disadvantage: Suitable reservoirs of very hot water are deep underground and the cost of drilling to extract water is high

Conserving Energy Switching energy use to off-peak times Using less electricity in your daily life Discarding and/or replacing inefficient older appliances such as refrigerators, freezers, and window air conditioners Replacing incandescent bulbs with more efficient alternatives Having a smart meter installed to monitor your energy use