energy and the environment renewable resources and alternative energy

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Post on 18-Dec-2015




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  • Energy and the Environment Renewable Resources and Alternative Energy
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  • Energy efficiency calculation: energy efficiency (in %) = energy in/energy out X 100 Ex. light bulb efficiency = proportion of electrical energy that reaches the bulb and is converted into light energy rather than into heat Most of our devices are fairly inefficient More than 40 % of all commercial energy used in the United States is wasted Most of it is lost from inefficient fuel-wasting vehicles (internal combustion engines), furnaces, and appliances and from leaky, poorly insulated buildings
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  • Energy Efficiency of Common Conversion Devices DeviceEfficiency Incandescent light bulb5% Fluorescent light bulb22% Internal combustion engine (gasoline) 10% Human body20%25% Steam turbine45% Fuel cell60%
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  • Renewable energy -- energy from sources that are constantly being regenerated or replenished. Important aspect of sustainability
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  • Renewables Major Renewable Energy Sources Hydropower Biomass Geothermal Wind Solar
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  • Solar Energy: We utilize two types Active Solar & Passive Solar Active Solar: Technologies like solar panels (photovoltaic cells) are used to convert solar energy into electrical energy.
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  • Active Solar Heating -- energy from the sun can be gathered by collectors and used to heat water or to heat a building Solar collectors, usually mounted on a roof to capture the suns energy
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  • Active Solar Energy In a solar water heating system, a liquid is pumped through solar collectors. The heated liquid flows through a heat exchanger that transfers the energy to water, which is used in a household.
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  • Photovoltaic cells Solar cells were invented more than 120 years ago, and now they are used to power everything from calculators to space stations. Sunlight falls on a semiconductor, causing it to release electrons. The electrons flow through a circuit that is completed when another semiconductor in the solar cell absorbs electrons and passes them on to the first semiconductor.
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  • Photovoltaic cells or solar cells convert the suns energy into electricity no moving parts, run on nonpolluting power from the sun So why dont solar cells meet all of our energy needs? produces a very small electrical current. So meeting the electricity needs of a small city would require covering hundreds of acres with solar panels. Solar cells also require extended periods of sunshine to produce electricity. This energy is stored in batteries, which supply electricity when the sun is not shining. Solar cells have great potential for use in developing countries, where energy consumption is minimal and electricity distribution networks are limited.
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  • Solar Panel Pros: gives off no pollution, the only pollution produced is the manufacturing of the devices in factories, transportation of the goods, and installation. produces electricity very quietly. harness electricity in remote locations. space saving, can be installed on top of many rooftops. cost-effective, initial investment cost may be high, once installed, they provide a free source of electricity, which will pay off over the coming years. decreases dependence on fossil fuels.
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  • Solar Panel Cons: initial cost only able to generate electricity during daylight hours. weather can affect the efficiency of solar cells. pollution can affect efficiency.
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  • Solar Potential for the US Solar also has a large potential for growth - total incoming solar radiation equates to about 3,000 times more solar energy than total energy used worldwide.
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  • Passive Solar: uses the suns energy to heat something directly.
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  • In passive solar building design, windows, walls, and floors are made to: collect, store, and distribute solar energy in the form of heat in the winter must be well insulated with thick walls and floors in order to prevent heat loss reject solar heat in the summer Doesn't involve the use of mechanical and electrical devices. Key take advantage of the local climate. Consider: window placement and size, thermal insulation, thermal mass, and shading.
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  • Passive solar buildings are oriented according to the yearly movement of the sun. In summer, the suns path is high in the sky and the overhang of the roof shades the building and keeps it cool. In winter, the suns path is lower in the sky, so sunlight shines into the home and warms it.
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  • Another use of passive solar heat water for household use.
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  • Passive Solar Pros: Renewable. No fuels required. Non-polluting. Carbon free except for production and transportation. Simple, low maintenance. Hot water provides some storage capacity. Operating costs are near-zero. Quiet. Few or no moving parts. Mature technology. Good return on investment. High efficiency. Can be combined with photovoltaic cells in highly efficient cogeneration schemes.
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  • Passive Solar Cons: Intermittent. Low energy density. Does not produce electricity. Supplemental energy source or storage required for long sunless stretches. Expensive compared to conventional water heaters. Construction/installation costs can be high. Hard to compete against very cheap natural gas. Visually unattractive to some. Manufacturing processes can create pollution. Produce low grade energy (heat vs. electricity). Dependent on home location and orientation.
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  • Hydropower HIGHEST DAM IN THE UNITED STATES Oroville on the Feather River in California 770 feet LARGEST HYDRO PROJECT IN THE UNITED STATES Grand Coulee on the Columbia River in Washington 6180 MW Largest form of alternative energy used About 20 % of the worlds electricity is produced by hydropower. The countries that lead the world in hydroelectric energy are China, Canada, Brazil, United States, Russia
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  • HydroelectricityPower from Moving Water Energy from the sun causes water to evaporate, condense in the atmosphere, and fall back to the Earths surface as rain. Gravity causes water to flow downwards -- this downward motion of water contains kinetic energy that can be converted into mechanical energy, and then can be converted into electrical energy at hydro-electric power stations
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  • Large hydroelectric power plants have a dam that is built across a river to hold back a reservoir of water. The water in the reservoir is released to turn a turbine, which generates electricity. The energy of this water is evident shown in the spillway. Three Gorges Dam
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  • How Hydropower Works Hydroelectric dams convert the potential energy, or stored energy, of a reservoir into the kinetic energy, or moving energy, of a spinning turbine. The movement of the turbine is then used to generate electricity.
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  • Large dam construction Industrialized (developed)countries have already tapped much of their potential. Non-industrialized (developing) countries have the most untapped potential such as Brazil, India, and China. A modern trend is micro-hydropower, which is electricity produced in a small stream without having to build a big dam. The turbine may even float in the water, not blocking the river at all. Micro-hydropower is much cheaper than large hydroelectric dam projects, and it permits energy to be generated from small streams in remote areas.
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  • Hydropower Generation Hydroelectric power production costs less than half of fossil fuel derived electricity (does not include construction costs).
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  • Future of Hydropower Tidal Power: Propeller Systems Tidal Power: Enclosures Tidal Power: Wave Systems
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  • Hydropower Pros: very clean, does not release air pollutants that cause acid precipitation inexpensive to operate provides other benefits such as flood control and water for drinking, agriculture, industry, and recreation
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  • Hydropower Cons: Provides about 5 to 10% of energy needs Expensive to build Dependability; prolonged droughts can cut electrical production in half or more. Ecosystem above/below the dam is changed Blocks migratory fish Destroys habitats When land behind a dam is flooded, people are displaced. Dam failure if a dam bursts, people living in areas below the dam can be killed. As a river slows down, the river deposits some of the sediment it carries. This fertile sediment builds up behind a dam instead of enriching the land farther down the river. As a result, farmland below a dam can become less productive (loss of nutrients). Recent research has also shown that the decay of plant matter trapped in reservoirs can release large amounts of greenhouse gases Loss of aesthetic value
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  • Wind Power Use dates back thousands of years in the form of windmills, sailing ships, etc.
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  • Wind PowerCheap and Abundant Energy from the sun warms the Earths surface unevenly, which causes air masses to flow in the atmosphere. We experience the movement of these air masses as wind. Wind power, which converts the movement of wind into electric energy, is t


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