Energy and the Environment Renewable Resources and Alternative Energy
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Energy and the EnvironmentRenewable Resources and Alternative EnergyEnergy 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
Energy Efficiency of Common Conversion DevicesDeviceEfficiencyIncandescent light bulb5%Fluorescent light bulb22%Internal combustion engine (gasoline)10%Human body20%25%Steam turbine45%Fuel cell60%Renewable energy -- energy from sources that are constantly being regenerated or replenished. Important aspect of sustainability
Renewables Major Renewable Energy Sources HydropowerBiomassGeothermalWindSolar
Solar Energy: We utilize two typesActive Solar & Passive SolarActive Solar:Technologies like solar panels (photovoltaic cells) are used to convert solar energy into electrical energy.
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
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.
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.
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 requirecovering hundreds of acres with solar panels. Solar cells alsorequire extended periods of sunshine to produce electricity.This energy is stored in batteries, which supply electricitywhen the sun is not shining.
Solar cells have great potential for use in developing countries, whereenergy consumption is minimal and electricity distributionnetworks are limited.
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. 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.
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.Passive Solar: uses the suns energy to heat something directly.
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 wintermust be well insulated with thick walls and floors in order to prevent heat lossreject 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.
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.
Another use of passive solar heat water for household use.
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.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.
HydropowerHIGHEST DAM IN THE UNITED STATESOroville on the Feather River in California770 feet
LARGEST HYDRO PROJECT IN THE UNITED STATESGrand Coulee on the Columbia River in Washington6180 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
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 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
How Hydropower WorksHydroelectric 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.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.
Hydroelectric power production costs less than half of fossil fuel derived electricity (does not include construction costs).Future of HydropowerTidal Power: Propeller Systems
Tidal Power: EnclosuresTidal Power: Wave Systems
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
Hydropower Cons:Provides about 5 to 10% of energy needsExpensive to buildDependability; prolonged droughts can cut electrical production in half or more.Ecosystem above/below the dam is changedBlocks migratory fishDestroys 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. Thisfertile sediment builds up behind a dam instead of enriching theland 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 gasesLoss of aesthetic valueWind PowerUse dates back thousands of years in the form of windmills, sailing ships, etc.
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 the fastest growing energy source in the world. Simple technology Wind energy turns the fan blades, which turn the turbine to generate electricity.
Technology development more efficiently capturing wind (blade types) making towers that can work in high winds
To optimize output, it is best to position wind turbines in areas of constant wind, yet these areas typically have high winds and can damage the windmills.
Wind turns the blades and gears are used spin the generator. In California, large wind farms supply electricity to 280,000 homes.
In windy rural areas, small wind farms with 20 or fewer turbines are also becoming common.
Because wind turbines take up little space, some farmers can add wind turbines to their land and still use the land for other purposes.Farmers can then sell the electricity they generate to the local utility.
Pasadena, CAScientists estimate that the windiest spots on Earth could generatemore than ten times the energy used worldwide.
One problem of wind energy is transporting electricity from rural areas where it is generated to urban centers where it is needed.
In the future, the electricity may be used on the wind farm to produce hydrogen from water. The hydrogen could then be trucked or piped to cities for use as a fuel.
Midwest has more than 90% of US potential Montana, Wyoming, Colorado, New Mexico, North Dakota, South Dakota, Nebraska, Kansas, Oklahoma, Texas, Iowa and MinnesotaWind Power ProsCost is very competitive, production costs are about 5 cents per kilowatt-hour (coal electricity is around 15 cents). subsidies helped to create a viable market.It is estimated that the costs could be lowered to 3-4 cents per kilowatt-hour as wind technology improves. Improvements in technology may also open less windy areas up for economically useful and viable wind power.
Wind Power ConsReliability is a key issue, as the wind does not always blow. Requires a storage mechanism that compensates for reliability.Recently, aesthetics has become a significant issue.Killing of birds and bats from high blade tip speeds.Disruption of natural wind patterns.
Atlantic City, NJ
BiomassBasicsEnergy from the sun, via photosynthesis in plants.This is the same energy we use as food.This is the same energy that made fossil fuels; fossil fuels are concentrated over time by the heat and pressure within the Earth.The oldest form of energy used by humans: wood fire, a form of biomass. In the developed world, biomass that was once thought of as waste is being used for energy.
What is biomass?Energy from plants and plant-derived materialsAny plant tissue can be used for energy, but the faster the plant grows, the more useful it is.
BiomassPower from Living Things
Plant material, manure, and any other organic matter that is used as an energy source
Fossil fuels are organic and can be thought of as biomass energy sources, but fossil fuels are nonrenewable.
Renewable biomass fuels, such as wood and dung, are major sources of energy in developing countries.
Although wood is a renewable resource, if trees are cut down faster than they grow, the resulting habitat loss, deforestation, and soil erosion can be severe. In addition, harmful air pollution may result from burning wood and dung.
The consumption of wood as an energy source has increased by nearly 80 percent since 1960.
In developing countries such as Nepal, Burma, Guatemala, Congo (DRC), and Kenya, the use of fuelwood places an enormous burden on local environments. More than half of all wood cut in the world is used as fuel for heating and cookingMethane can be burned to generate heat or electricity.
In China, more than 6 million households use biogas digesters to ferment manure and produce gas used for heating and cooking.
In 2002, Britains first dung-fired power station started to produce electricity. This power station uses the methane given off by cow manure as fuel.
Similarly, some landfills in the United States generate electricityby using the methane from the decomposition of trash.
BiomassHow does it work? How do we convert biomass energy to useful forms of energy? Direct burning Gasification Co-firing FermentationMethods to convert biomass to energy
Direct burning: Plant material is chipped, dried, and then burned to boil water, make steam, and then electricity. This is a relatively inefficient technology and the most polluting method of energy from biomass.
Gasification: The conversion of biomass into a gas and carbon powder. Process begins with pyrolysis. Biomass is combined with hot sand (800C). This reduces biomass to gases and carbon powder.
Cofiring: The use of biomass in combination with coal. Biomass cheaper than coal, so cofiring is cheaper than burning coal alone. It also produces less sulfur oxide pollution. It is easy to adapt current systems to cofiring.
Fermentation: The production of alcohol (ethanol mainly) from sugars in biomass. The alcohol can be burned alone, or mixed with gasoline. Mixtures can range from 10% ethanol (often used to reduce pollution) to 100% ethanol. Ethanol is about as expensive as gasoline currently (although comparisons are hard to make due to the many subsidies for both). The net energy yield from ethanol is low. Alcohol liquid fuels can also be derived from biomass.
For example, ethanol, an alcohol, can be made by fermenting fruit or agricultural waste.
In the United States, corn is a major source ofethanol.
Cars and trucks can run on ethanol or gasohol, a blend of gasoline and ethanol.
Gasohol produces less air pollution than fossil fuels do. For this reason, some U.S. states require the use of gasohol in vehicles as a way to reduce air pollution.
Ethanol as a source of energy must compete with food production, and will have less dependability from year to year as climate change affects crops.
Currently we get less than 1% of our energy in industrialized countries from biomass.
While biomass is compelling, as our population continues to grow the competition for arable land and water needed for food production is going to make a number of biomass options unsuitable....