RENEWABLE ENERGY RESOURCES

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1 RENEWABLE ENERGY RESOURCES

2 Energy Efficiency Energy efficiency the amount of useful energy produced compared to the amount wasted as heat (2 nd Law of Thermodynamics); built into the device or system, unavoidable waste Examples of levels of energy efficiency: human body: 20-25% incandescent lightbulb: 5% internal combustion engine: 20-25% steam turbine: 45%

3 Energy conservation Energy conservation making an effort to reduce the amount of energy used, some waste can be avoided Examples? Why should we try to increase both?

4 Energy Use by Source

5 Inexhaustible Energy Resources Inexhaustible energy resources are sources of renewable energy that are constant and will not run out in the future. Inexhaustible energy resources include the Sun, wind, water, and geothermal energy.

6 Solar Energy Solar energy is energy from the Sun. As the Sun s energy heats the Earth, it causes circulation in Earth s atmosphere and oceans. Global winds and ocean currents occur due to solar energy.

7 Solar Energy People use solar cells to actively collect energy from the sun. Solar power plants produce steam to turn turbine Solar heating Active and passive systems Photovoltaic cells Solar batteries use special semiconductors

8 Solar Energy Advantages Renewable and free High energy yield A very clean source of energy No air/water pollution during operation Low operating costs will pay for themselves over time

9 Solar Energy Disadvantages: Intermittent source Energy storage issues Low energy density Start up costs are expensive Inefficient the best solar cells are about 28% efficient

10 Energy from Wind Windmills can be used to generate electricity. When a large number of windmills are placed in one area for the purpose of generating electricity, the area is called a wind farm.

11 Energy from Wind

12 Wind Energy How it works Wind turbines directly generate electricity Quite efficient (not a heat engine) Wind Energy Potential shading gives potential for instate electrical needs numbers give total potential for total US needs

13 Energy from Wind Advantages High net energy yield Renewable and free Very clean source of energy Long operating life Low operating/maintenance costs Can be quickly built; not too expensive Now almost competitive with hydro and fossil fuels Land can be used for other purposes

14 Energy from Wind Disadvantages Energy storage issues An intermittent source of energy; need backup (eg stored energy) for low-wind days or must be connected to the electrical grid Only practical in areas that are windy enough Visual pollution danger to birds New (slow turning) designs largely eliminate this problem Low energy density of wind must use large areas of land

15 Energy from Water Electricity produced by water power is called hydroelectric energy. To generate the electricity, a large dam is built to retain water. As the water is released, its force powers generators that make electricity.

16 Energy from Water Advantages Cheap to operate long life and lower operating costs than all other power plants Renewable High yield lower energy cost than any other method Pretty plentiful some countries depend almost entirely on it Not intermittent (if reservoir is large enough) Reservoirs have multiple uses flood control, drinking water, aquaculture, recreation Less air pollution than fossil fuel combustion

17 Energy from Water Disadvantages: Human population displacement Reduces availability of water downstream Ecosystem impacts Barriers to migrating fish Loss of biodiversity both upstream and downstream Coastal erosion Reduces nutrient flow Water pollution problems Low dissolved oxygen (DO) Deposition of silt a big problem (also shortens dam life) The Size Issue Many (most) of the above problems are significantly worse for larger dams However, small dams have shorter lifetimes, less capacity, and are more intermittent

18 Geothermal Energy obtained by using hot magma or hot, dry rocks inside Earth is called geothermal energy. Geothermal energy is the same type of energy that causes volcanoes to erupt or water to shoot up as geysers.

19 Geothermal Bodies of magma heat large reservoirs of groundwater. Geothermal power plants use steam from the reservoirs to produce electricity.

20 Geothermal Advantages Renewable Easy to exploit in some cases CO 2 production less than with fossil fuels High net energy yield

21 Geothermal Disadvantages Not available everywhere Hydrogen Sulfide pollution Produces some water pollution (somewhat similar to mining) Expensive to build

22 Renewable Energy Resources Energy resources that can be replaced in nature or by humans within a relatively short period of time are referred to as renewable energy resources. Biomass energy is energy derived from burning organic materials such as wood, alcohol, and garbage.

23 Biomass energy Advantages Versatile Renewable No net CO 2 emissions (ideally) Emits less Sulfer and Nitrogen than fossil fuels

24 Renewable Energy Resources Disadvantages Low energy density/yield In some cases (eg, corn-derived bioethanol) may yield no net energy Land conversion Biodiversity loss Possible decrease in agricultural food productivity Usual problems associated with intensive agriculture Nutrient pollution Soil depletion Soil erosion Other water pollution problems.

25 Conservation Recycling is using old materials to make new ones. By reducing our use of resources, reusing resources whenever possible, and recycling resources, like aluminum, we can conserve our natural resources. (The 3 R s)