Renewable Energy Sources Section 10.3 Renewable Energy Sources

Renewable Energy Sources Renewable resource: is an energy source that is replaced nearly as quickly as it is used Solar energy is a renewable resource than can provide a source of energy for the foreseeable future Even if a small fraction of solar energy could be used, it would greatly reduce consumption of fossil fuels

Solar Cells Photovoltaic cells—(solar cell)—a device that is used to convert solar energy into electric energy Solar cells are made of two layers of semiconductor materials between two layers of conducting metal The process of converting radiant energy from the Sun directly to electricity is about 7-11% efficient

Using Solar Energy Producing electricity using solar cells is more expensive on a large scale than use of non-renewable fuel Cost /kwH for fossil-fuel power- $ .8 Cost/kwH for solar cell power--$ .28 Disadvantages: Electricity generated by solar cells must be stored in batteries However: lg. amts of energy are needed to manufacture batteries/ Lg. batteries contain heavy metals; i.e. lead; --environmental hazards

Hydroelectricity Hydroelectricity—electricity produced from the energy of moving water Currently, about 8% of electrical energy used in the US is produced by hydroelectric power plants Hydroelectric power plants—Efficient way to produce electricity w/almost no pollution After initial costs of building dams, hydroelectric plants—relatively cheap

More on Hydroelectricity Disadvantages: Artificial dams can disturb the balance of natural ecosystems ex: fish migration upstream may be blocked by some dams Some water sources suitable for a hydroelectric power plant are not near the people needing the power

Energy from the Tides Gravity of the Moon and Sun causes bulges in Earth’s oceans-tides Hydroelectric power can be generated by ocean tides Tide comes in/moving water spins a turbine that generates electricity Low tide/water behind the dam flows back out to the ocean, spinning turbines and generating electric power

Harnessing the Wind Windmills—can use the energy of the wind to generate electricity Only a few places on Earth consistently have enough wind to rely on wind power to meet energy needs Windmills are only about 20% efficient

More on Windmills Advantages Don’t pollute Don’t consume any resources Disadvantages: -can disrupt migration patterns of some birds -can be noisy

Energy from inside Earth Geothermal energy: The thermal energy that is contained in hot magma In some places, Earth’s crust has cracks or thin spots that allow magma to rise near the surface This produces hot springs/geysers, etc. Ex: Old Faithful **In some areas, the hot water can be pumped into houses to provide heat

Geothermal Power Plants Geothermal energy can be used to generate electricity Steam is converted to electrical energy The efficiency of geothermal power plants is about 16 percent However: use of geothermal energy is limited to areas where magma is relatively close to the surface

Alternative Fuels More than 2/3 of the petroleum used in the US powers cars and other vehicles Other options: electric cars/hydrogen gas as an alternative fuel/???? Biomass fuels: Biomass—renewable organic matter Can be burned in the presence of oxygen to convert stored chemical energy to thermal energy Burning biomass—probably the oldest use of natural resources for meeting human energy needs

Innovation Paper What is an innovation? An innovation is a CHANGE AGENT Something that promotes/introduces/encourages change YOUR ASSIGNMENT!!