دورات هندسية

 

 

الصيغ العامة للطاقة المتجددة..! Common Forms of Renewable Energy

صفحة 1 من 3 12 3 الأخيرةالأخيرة
النتائج 1 إلى 10 من 27
  1. [1]
    الصورة الرمزية د.محمد باشراحيل
    د.محمد باشراحيل
    د.محمد باشراحيل غير متواجد حالياً

    إستشاري الملتقى

    تاريخ التسجيل: Mar 2009
    المشاركات: 7,042
    Thumbs Up
    Received: 127
    Given: 15

    الصيغ العامة للطاقة المتجددة..! Common Forms of Renewable Energy

    الصيغ العامة للطاقة المتجددة

    السلام عليكم ورحمة الله وبركاته



    المرفق عبارة عن محاضرة للدكتور بانج من جامعة هونج كونج
    عن الأنواع المتجدة من الطاقة.

    سرد فيها الأنواع المعروفة وإستخداماتها في العالم
    وتطبيقاتها في هونج كونج بشكل خاص.

    المحاضرة مختصرة ومفيدة ومباشرة

    عرف فيها الطاقة المتجددة كالتالي:

    " هي الطاقة المشتقة من العمليات الطبيعية والتي تتجدد بصورة ثابتة.
    يتم إشتقاقها في مختلف انواعها ، مباشَرة او بطريقة غير مباشِرة ،
    من الشمس أو من الحرارة المتولِدة من باطن الأرض."

    أترككم مع المرفق ،

    والله الموفق.

  2. [2]
    الساحر
    الساحر غير متواجد حالياً
    عضو فعال جداً
    الصورة الرمزية الساحر


    تاريخ التسجيل: Sep 2006
    المشاركات: 348
    Thumbs Up
    Received: 6
    Given: 0
    بارك الله فيك علي هذه المعلومات

    0 Not allowed!


    الطــــــــــــــــويل

  3. [3]
    عبدالرحمن همام
    عبدالرحمن همام غير متواجد حالياً
    عضو فعال جداً
    الصورة الرمزية عبدالرحمن همام


    تاريخ التسجيل: Aug 2008
    المشاركات: 305
    Thumbs Up
    Received: 0
    Given: 0
    شكرا جزيلا
    جعلها الله في ميزان حسناتك

    0 Not allowed!


    لا اله الا الله
    محمد رسول الله


  4. [4]
    الساحر
    الساحر غير متواجد حالياً
    عضو فعال جداً
    الصورة الرمزية الساحر


    تاريخ التسجيل: Sep 2006
    المشاركات: 348
    Thumbs Up
    Received: 6
    Given: 0
    انشاء الله نلقي متك كل جديد...........وبارك الله فيك

    0 Not allowed!


    الطــــــــــــــــويل

  5. [5]
    د.محمد باشراحيل
    د.محمد باشراحيل غير متواجد حالياً
    إستشاري الملتقى
    الصورة الرمزية د.محمد باشراحيل


    تاريخ التسجيل: Mar 2009
    المشاركات: 7,042
    Thumbs Up
    Received: 127
    Given: 15
    اقتباس المشاركة الأصلية كتبت بواسطة عبدالرحمن همام مشاهدة المشاركة
    شكرا جزيلا
    جعلها الله في ميزان حسناتك
    العفو مهندس عبدالرحمن همام..

    وجزاك خير الجزاء وأثابك خيري الدنيا والآخرة.

    0 Not allowed!



  6. [6]
    د.محمد باشراحيل
    د.محمد باشراحيل غير متواجد حالياً
    إستشاري الملتقى
    الصورة الرمزية د.محمد باشراحيل


    تاريخ التسجيل: Mar 2009
    المشاركات: 7,042
    Thumbs Up
    Received: 127
    Given: 15
    اقتباس المشاركة الأصلية كتبت بواسطة الساحر مشاهدة المشاركة
    بارك الله فيك علي هذه المعلومات
    اقتباس المشاركة الأصلية كتبت بواسطة الساحر مشاهدة المشاركة
    انشاء الله نلقي متك كل جديد...........وبارك الله فيك
    الله يسعدك
    أخي الفاضل الساحر

    وفقنا الله وإياك لكل خير.

    0 Not allowed!



  7. [7]
    Ind. Engineer
    Ind. Engineer غير متواجد حالياً
    عضو فعال
    الصورة الرمزية Ind. Engineer


    تاريخ التسجيل: Feb 2009
    المشاركات: 125
    Thumbs Up
    Received: 1
    Given: 0
    الله يعطيك العافية ..المحاضرة حلوة ..لكن مختصرة..

    0 Not allowed!


    الكمال في الحياة هدف لايمكن تحقيقه ...
    كن افضل ما تستطيع..وهذا يكفي.
    ( + )= ( + + )

  8. [8]
    د.محمد باشراحيل
    د.محمد باشراحيل غير متواجد حالياً
    إستشاري الملتقى
    الصورة الرمزية د.محمد باشراحيل


    تاريخ التسجيل: Mar 2009
    المشاركات: 7,042
    Thumbs Up
    Received: 127
    Given: 15
    Renewable sources
    Main article: Renewable energy
    Renewable energy is an alternative to fossil fuels and nuclear power, and was commonly called alternative energy in the 1970s and 1980s.

    [edit] Biomass, biofuels, and vegetable oil


    Sugar cane residue can be used as a biofuel


    Main articles: Alcohol fuel, Biomass, Vegetable oil economy, vegetable oil as fuel, biodiesel, Ethanol fuel Biomass production involves using garbage or other renewable resources such as corn or other vegetation to generate electricity. When garbage decomposes, the methane produced is captured in pipes and later burned to produce electricity. Vegetation and wood can be burned directly to generate energy, like fossil fuels, or processed to form alcohols.
    Vegetable oil is generated from sunlight and CO2 by plants. It is safer to use and store than gasoline or diesel as it has a higher flash point. Straight vegetable oil works in diesel engines if it is heated first. Vegetable oil can also be transesterified to make biodiesel, which burns like normal diesel.

    [edit] Pros



    This section does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (April 2008)
    • Biomass production can be used to burn organic waste products resulting from agriculture. This type of recycling encourages the philosophy that nothing on this Earth should be wasted. The result is less demand on the Earth's resources, and a higher carrying capacity for Earth because non-renewable fossil fuels are not consumed.
    • Biomass is abundant on Earth and is generally renewable. In theory, we will never run out of organic waste products as fuel, because we are continuously producing them. In addition, biomass is found throughout the world, a fact that should alleviate energy pressures in third world nations.
    • When methods of biomass production other than direct combustion of plant mass are used, such as fermentation and pyrolysis, there is little effect on the environment. Alcohols and other fuels produced by these alternative methods are clean burning and are feasible replacements to fossil fuels.
    • Since CO2 is first taken out of the atmosphere to make the vegetable oil and then put back after it is burned in the engine, there is no net increase in CO2.
    • By combining the use of biomass with geo-sequestration of CO2 then this could result in a net decrease of CO2 in the atmosphere.
    • Vegetable oil has a higher flash point and therefore is safer than most fossil fuels.
    • Transitioning to vegetable oil could be relatively easy as biodiesel works where diesel works, and straight vegetable oil takes relatively minor modifications.
    • The World already produces more than 100 billion gallons a year for food industry, so we have experience making it.
    • Algaculture has the potential to produce far more vegetable oil per acre than current plants.
    • Infrastructure for biodiesel around the World is significant and growing.
    [edit] Cons


    This section needs additional citations for verification.

    Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (April 2008)
    • Direct combustion of any carbon-based fuel leads to air pollution similar to that from fossil fuels.
    • Some researchers claim that when biomass crops are the product of intensive farming, ethanol fuel production results in a net loss of energy after one accounts for the fuel costs of petroleum and natural-gas fertilizer production, farm equipment, and the distillation process.[35]
    • There is a long list of reasons why even non-food based cellulosic ethanol cannot solve our energy crisis or global warming problems.[36]
    • Direct competition with land use for food production and water use.
    • Current production methods would require enormous amounts of land to replace all gasoline and diesel. With current technology, it is not feasible for biofuels to replace the demand for petroleum.
    • Even with the most-optimistic current energy return on investment claims, in order to use 100% solar energy to grow corn and produce ethanol (fueling machinery with ethanol, distilling with heat from burning crop residues, using NO fossil fuels at all), the consumption of ethanol to replace only the current U.S. petroleum use would require three quarters of all the cultivated land on the face of the Earth.[37]
    [edit] Geothermal energy

    Main article: Geothermal power
    Geothermal energy harnesses the heat energy present underneath the Earth. Two wells are drilled. One well injects water into the ground to provide water. The hot rocks heat the water to produce steam. The steam that shoots back up the other hole(s) is purified and is used to drive turbines, which power electric generators. When the water temperature is below the boiling point of water a binary system is used. A low boiling point liquid is used to drive a turbine and generator in a closed system similar to a refrigeration unit running in reverse.

    [edit] Pros

    • Geothermal energy is base load power.[38]
    • Economically feasible in high grade areas now.[38]
    • Low deployment costs.[38]
    • Geothermal power plants have a high capacity factor; they run continuously day and night with an uptime typically exceeding 95%.
    • Once a geothermal power station is implemented, the energy produced from the station is practically free, minus maintenance costs. A small amount of energy is required in order to run a pump, although this pump can be powered by excess energy generated at the plant.[citation needed]
    • Geothermal power stations are relatively small, and have a lesser impact on the environment than tidal or hydroelectric plants. Because geothermal technology does not rely on large bodies of water, but rather, small, but powerful jets of water, like geysers, large generating stations can be avoided without losing functionality.[citation needed]
    • Geothermal is now feasible in areas where the Earth's crust is thicker. Using enhanced geothermal technology, it's possible to drill deeper and inject water to generate geothermal power.[39]
    • Geothermal energy does not produce air or water pollution if performed correctly.
    [edit] Cons

    • Geothermal power extracts small amounts of minerals such as sulfur that are removed prior to feeding the turbine and re-injecting the water back into the injection well.[citation needed]

    • Geothermal power requires locations that have suitable subterranean temperatures within 5 km of surface.[citation needed]

    • Some geothermal stations have created geological instability, even causing earthquakes strong enough to damage buildings. [40]
    [edit] Hydroelectric energy


    This section does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (April 2008)
    Main article: Hydroelectricity
    In hydro energy, the gravitational descent of a river is compressed from a long run to a single location with a dam or a flume. This creates a location where concentrated pressure and flow can be used to turn turbines or water wheels, which drive a mechanical mill or an electric generator.

    [edit] Pros

    • Hydroelectric power stations can promptly increase to full capacity, unlike other types of power stations. This is because water can be accumulated above the dam and released to coincide with peak demand.
    • Electricity can be generated constantly, so long as sufficient water is available.
    • Hydroelectric power produces no primary waste or pollution.
    • Hydropower is a renewable resource.
    • Hydroelectricity assists in securing a country's access to energy supplies.
    • Much hydroelectric capacity is still undeveloped, such as in Africa.
    • The resulting lake can have additional benefits such as doubling as a reservoir and providing opportunities for leisure activities such as watersports and fishing as is the case with Kielder Water in Northumberland, UK.
    [edit] Cons

    • The construction of a dam can have a serious environmental impact on the surrounding areas. The amount and the quality of water downstream can be affected, which affects plant life both aquatic, and land-based. Because a river valley is being flooded, the local habitat of many species are destroyed, while people living nearby may have to relocate their homes.
    • Hydroelectricity can only be used in areas where there is a sufficient and continuing supply of water.
    • Flooding submerges large forests (if they have not been harvested). The resulting anaerobic decomposition of the carboniferous materials releases methane, a greenhouse gas.
    • Dams can contain huge amounts of water. As with every energy storage system, failure of containment can lead to catastrophic results, e.g. flooding
    • Dams create large lakes that may have adverse effects on Earth tectonic system causing intense earthquakes. [41]
    • Hydroelectric plants rarely

    0 Not allowed!



  9. [9]
    د.محمد باشراحيل
    د.محمد باشراحيل غير متواجد حالياً
    إستشاري الملتقى
    الصورة الرمزية د.محمد باشراحيل


    تاريخ التسجيل: Mar 2009
    المشاركات: 7,042
    Thumbs Up
    Received: 127
    Given: 15
    Solar power

    The CIS Tower, Manchester, England, was clad in PV panels at a cost of £5.5 million. It started feeding electricity to the national grid in November 2005.


    Main articles: Solar energy, Photovoltaics Solar power involves using solar cells to convert sunlight into electricity, using sunlight hitting solar thermal panels to convert sunlight to heat water or air, using sunlight hitting a parabolic mirror to heat water (producing steam), or using sunlight entering windows for passive solar heating of a building. It would be advantageous to place solar panels in the regions of highest solar radiation. In the Phoenix, Arizona area, for example, the average annual solar radiation is 5.7 kWh/m²/day,[42] or 2080.5 kWh/m²/year. Electricity demand in the continental U.S. is 3.7*1012 kW·h per year. Thus, at 20% efficiency, an area of approximately 3500 square miles (3% of Arizona's land area) would need to be covered with solar panels to replace all current electricity production in the US with solar power. The average solar radiation in the United States is 4.8 kwh/m²/day,[43] but reaches 8–9 kWh/m²/day in parts of the Southwest.
    China is increasing worldwide silicon wafer capacity for photovoltaics to 2,000 metric tons by July 2008, and over 6,000 metric tons by the end of 2010.[44] Significant international investment capital is flowing into China to support this opportunity. China is building large subsidized off-the-grid solar-powered cities in Huangbaiyu and Dongtan Eco City. Much of the design was done by Americans such as William McDonough.[citation needed]
    See also: Solar power in China

    [edit] Pros

    • Solar power imparts no fuel costs.
    • Solar power is a renewable resource. As long as the Sun exists, its energy will reach Earth.
    • Solar power generation releases no water or air pollution, because there is no combustion of fuels.
    • In sunny countries, solar power can be used in remote locations, like a wind turbine. This way, isolated places can receive electricity, when there is no way to connect to the power lines from a plant.
    • Solar energy can be used very efficiently for heating (solar ovens, solar water and home heaters) and daylighting.
    • Coincidentally, solar energy is abundant in regions that have the largest number of people living off grid — in developing regions of Africa, Indian subcontinent and Latin America. Hence cheap solar, when available, opens the opportunity to enhance global electricity access considerably, and possibly in a relatively short time period.[45]
    • Photovoltaic systems are subsidized, up to $5 USD per watt in some American states.[46]
    • Passive solar building design and zero energy buildings are demonstrating significant energy bill reduction, and some are cost-effectively off the grid.
    • Photovoltaic equipment cost has been steadily falling, the production capacity is rapidly rising, and the U.S. Administration expects its Solar America Initiative to help make amortized PV electricity price competitive for the new generation of zero energy buildings.[47]
    • Distributed point-of-use photovoltaic systems eliminate expensive long-distance electric power transmission losses.
    • Photovoltaics are much more efficient in their conversion of solar energy to usable energy than biofuel from plant materials.[48]

    [edit] Cons

    • Solar electricity is currently more expensive than grid electricity.
    • Solar heat and electricity are not available at night and may be unavailable due to weather conditions; therefore, a storage or complementary power system is required for off-the-grid applications.
    • Solar cells produce DC which must be converted to AC (using a grid tie inverter) when used in currently existing distribution grids. This incurs an energy loss of 4–12%.[49]
    • The energy payback time — the time necessary for producing the same amount of energy as needed for building the power device — for photovoltaic cells is about 1–5 years, depending primarily on location.[50]

    [edit] Tidal Power Generation

    Main article: Tidal power
    Tidal power can be extracted from Moon-gravity-powered tides by locating a water turbine in a tidal current, or by building impoundment pond dams that admit-or-release water through a turbine. The turbine can turn an electrical generator, or a gas compressor, that can then store energy until needed. Coastal tides are a source of clean, free, renewable, and sustainable energy.[citation needed]

    [edit] Wind power


    This section needs additional citations for verification.
    Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (April 2008)

    Wind power: worldwide installed capacity and prediction 1997-2010, Source: WWEA


    Main article: Wind power
    This type of energy harnesses the power of the wind to propel the blades of wind turbines. These turbines cause the rotation of magnets, which creates electricity. Wind towers are usually built together on wind farms.

    [edit] Pros

    • Wind power produces no water or air pollution that can contaminate the environment, because there are no chemical processes involved in wind power generation. Hence, there are no waste by-products, such as carbon dioxide.[citation needed]
    • Power from the wind does not contribute to global warming because it does not generate greenhouse gases.[citation needed]
    • Wind generation is a renewable source of energy, which means that we will never run out of it.
    • Wind towers can be beneficial for people living permanently, or temporarily, in remote areas. It may be difficult to transport electricity through wires from a power plant to a far-away location and thus, wind towers can be set up at the remote setting.[citation needed]
    • Farming and grazing can still take place on land occupied by wind turbines.[citation needed]
    • Those utilizing wind power in a grid-tie configuration will have backup power in the event of a power outage.[citation needed]
    • Due to the ability of wind turbines to coexist within agricultural fields, siting costs are frequently low.[citation needed]

    [edit] Cons

    • Wind is unpredictable; therefore, wind power is not predictably available. When the wind speed decreases less electricity is generated. This makes wind power unsuitable for base load generation.[citation needed]
    • Wind farms may be challenged in communities that consider them an eyesore or view obstructor.[51]
    • Wind farms, depending on the location and type of turbine, may negatively affect bird migration patterns and may pose a danger to the birds themselves.[citation needed]
    • Windfarms may interfere with radar creating a hole in radar coverage and so affect national security. [52]

    [edit] Increased efficiency in energy use


    This section needs additional citations for verification.
    Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (April 2008)
    Efficiency is increasing by about 2% a year, and absorbs most of the requirements for energy development. New technology makes better use of already available energy through improved efficiency, such as more efficient fluorescent lamps, engines, and insulation. Using heat exchangers, it is possible to recover some of the energy in waste warm water and air, for example to preheat incoming fresh water. Hydrocarbon fuel production from pyrolysis could also be in this category, allowing recovery of some of the energy in hydrocarbon waste. Meat production is energy inefficient compared to the production of protein sources like soybean or Quorn. Already existing power plants often can and usually are made more efficient with minor modifications due to new technology. New power plants may become more efficient with technology like cogeneration. New designs for buildings may incorporate techniques like passive solar. Light-emitting diodes are gradually replacing the remaining uses of light bulbs. Note that none of these methods allows perpetual motion, as some energy is always lost to heat.
    Mass transportation increases energy efficiency compared to widespread conventional automobile use while air travel is regarded as inefficient. Conventional combustion engine automobiles have continually improved their efficiency and may continue to do so in the future, for example by reducing weight with new materials. Hybrid vehicles can save energy by allowing the engine to run more efficiently, regaining energy from braking, turning off the motor when idling in traffic, etc. More efficient ceramic or diesel engines can improve mileage. Electric vehicles such as Maglev, trolleybuses, and PHEVs are more efficient during use (but maybe not if doing a life cycle analysis) than similar current combustion based vehicles, reducing their energy consumption during use by 1/2 to 1/4. Microcars or motorcycles may replace automobiles carrying only one or two people. Transportation efficiency may also be improved by in other ways, see automated highway system.
    Electricity distribution may change in the future. New small scale energy sources may be placed closer to the consumers so that less energy is lost during electricity distribution. New technology like superconductivity or improved power factor correction may also decrease the energy lost. Distributed generation permits electricity "consumers," who are generating electricity for their own needs, to send their surplus electrical power back into the power grid.

    [edit] Energy transportation


    This section needs additional citations for verification.
    Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (April 2008)
    See also: Pipeline transport
    While new sources of energy are only rarely discovered or made possible by new technology, distribution technology continually evolves. The use of fuel cells in cars, for example, is an anticipated delivery technology. This section presents some of the more common delivery technologies that have been important to historic energy development. They all rely in some way on the energy sources listed in the previous section.

    An elevated section of the Alaska Pipeline.


    • Fuels
    Shipping is a flexible delivery technology that is used in the whole range of energy development regimes from primitive to highly advanced. Currently, coal, petroleum and their derivatives are delivered by shipping via boat, rail, or road. Petroleum and natural gas may also be delivered via pipeline and coal via a Slurry pipeline. Refined hydrocarbon fuels such as gasoline and LPG may also be delivered via aircraft. Natural gas pipelines must maintain a certain minimum pressure to function correctly. Ethanol's corrosive properties prevent it from being transported via pipeline. The higher costs of ethanol transportation and storage are often prohibitive.[53]
    • Electric grids
    Electricity grids are the networks used to transmit and distribute power from production source to end user, when the two may be hundreds of kilometres away. Sources include electrical generation plants such as a nuclear reactor, coal burning power plant, etc. A combination of sub-stations, transformers, towers, cables, and piping are used to maintain a constant flow of electricity.
    Electric Grid: Pilons and cables distribute power


    Grids may suffer from transient blackouts and brownouts, often due to weather damage. During certain extreme space weather events solar wind can interfere with transmissions. Grids also have a predefined carrying capacity or load that cannot safely be exceeded. When power requirements exceed what's available, failures are inevitable. To prevent problems, power is then rationed. Industrialised countries such as Canada, the US, and Australia are among the highest per capita consumers of electricity in the world, which is possible thanks to a widespread electrical distribution network. The US grid is one of the most advanced, although infrastructure maintenance is becoming a problem. CurrentEnergy provides a realtime overview of the electricity supply and demand for California, Texas, and the Northeast of the US. African countries with small scale electrical grids have a correspondingly low annual per capita usage of electricity. One of the most powerful power grids in the world supplies power to the state of Queensland, Australia.

    0 Not allowed!



  10. [10]
    د.محمد باشراحيل
    د.محمد باشراحيل غير متواجد حالياً
    إستشاري الملتقى
    الصورة الرمزية د.محمد باشراحيل


    تاريخ التسجيل: Mar 2009
    المشاركات: 7,042
    Thumbs Up
    Received: 127
    Given: 15
    Energy storage
    Main articles: Energy storage, grid energy storage Methods of energy storage have been developed, which transform electrical energy into forms of potential energy. A method of energy storage may be chosen based on stability, ease of transport, ease of energy release, or ease of converting free energy from the natural form to the stable form.

    [edit] Compressed air vehicles

    Main articles: Compressed air vehicle, Air car The Indian company, Tata, is planning to release a compressed air powered car in 2008.

    [edit] Battery-powered vehicles

    Main articles: battery, battery electric vehicle Batteries are used to store energy in a chemical form. As an alternative energy, batteries can be used to store energy in battery electric vehicles. Battery electric vehicles can be charged from the grid when the vehicle is not in use. Because the energy is derived from electricity, battery electric vehicles make it possible to use other forms of alternative energy such as wind, solar, geothermal, nuclear, or hydroelectric.

    [edit] Pros

    • Produces zero emissions to help counteract the effects of global warming, as long as the electricity comes from a source which produces no greenhouse gases.
    • Batteries are a mature technology, no new expensive research and development is needed to implement technology.
    • Current lead acid battery technology offers 50+ miles range on one charge.[54]
    • The Tesla Roadster has a 200-mile (320 km) range on one charge.
    • Batteries make it possible for stationary alternative energy generation such as solar, wind, hydroelectric, or nuclear
    • Electric motors are 90% efficient compared to about 20% efficiency of an internal combustion engine.[55]
    • Battery electric vehicles have fewer moving parts than internal combustion engines, thus improving the reliability of the vehicle.
    • Battery electric vehicles are quiet compared to internal combustion engines.
    • Multiple electric vehicles sold out including the General Motors EV1 and the Tesla Roadster proving the demand for battery electric vehicles.
    • Operation of a battery electric vehicle is approximately 2 to 4 cents per mile, about a sixth the price of operating a gasoline vehicle.[56]
    • The use of battery electric vehicles may reduce the dependency on fossil fuels, depending on the source of the electricity.

    [edit] Cons

    • Current battery technology is expensive.
    • Some of the principal materials required in battery production, such as Lithium, are becoming increasingly scarce[1]
    • Battery electric vehicles have a relative short range compared to internal combustion engine vehicles, and recharge times are typically much longer than the time to fill a conventional fuel tank.
    • Some batteries (like the Gel battery and the Lead-acid battery) are highly toxic. Spent vehicle batteries present a potential environmental hazard. They are all best recycled at end of life.
    • Grid infrastructure and output would need to be improved significantly to accommodate a mass-adoption of grid-charged electric vehicles, although the problem is less if electric vehicles will recharge primarily at night, when electricity demand is currently lowest.
    • Some batteries perform less efficiently in cold weather, and a battery electric vehicle lacks a convenient source of waste engine heat to warm the passenger compartment. Accordingly, the test-marketing of some electric vehicles such as the General Motors EV1 took place in warm-weather parts of Arizona and California.
    • Some batteries also perform poorly in hot weather.

    [edit] Hydrogen economy

    Main article: Hydrogen economy
    Hydrogen can be manufactured at roughly 77 percent thermal efficiency by the method of steam reforming of natural gas.[57] When manufactured by this method it is a derivative fuel like gasoline; when produced by electrolysis of water, it is a form of chemical energy storage as are storage batteries, though hydrogen is the more versatile storage mode since there are two options for its conversion to useful work: (1) a fuel cell can convert the chemicals hydrogen and oxygen into water, and in the process, produce electricity, or (2) hydrogen can be burned (less efficiently than in a fuel cell) in an internal combustion engine.

    [edit] Pros

    • Hydrogen is colorless, odorless and entirely non-polluting, yielding pure water vapor (with minimal NOx) as exhaust when combusted in air. This eliminates the direct production of exhaust gases that lead to smog, and carbon dioxide emissions that enhance the effect of global warming.
    • Hydrogen is the lightest chemical element and has the best energy-to-weight ratio of any fuel (not counting tank mass).
    • Hydrogen can be produced anywhere; it can be produced domestically from the decomposition of water. Hydrogen can be produced from domestic sources and the price can be established within the country.

    [edit] Cons

    • Other than some volcanic emanations, hydrogen does not exist in its pure form in the environment, because it reacts so strongly with oxygen and other elements.
    • It is impossible to obtain hydrogen gas without expending energy in the process. There are three ways to manufacture hydrogen;
      • By breaking down hydrocarbons — mainly methane (steam reforming). If oil or gases are used to provide this energy, fossil fuels are consumed, forming pollution and nullifying the value of using a fuel cell. It would be more efficient to use fossil fuel directly.
      • By electrolysis of water — The process of splitting water into oxygen and hydrogen using electrolysis consumes large amounts of energy. It has been calculated that it takes 1.4 joules of electricity to produce 1 joule of hydrogen (Pimentel, 2002).
      • By reacting water with a metal such as sodium, potassium, or boron. Chemical by-products would be sodium oxide, potassium oxide, and boron oxide. Processes exist which could recycle these elements back into their metal form for re-use with additional energy input, further eroding the energy return on energy invested.
    • There is currently modest fixed infastructure for distribution of hydrogen that is centrally produced,[58] amounting to several hundred kilometers of pipeline. An alternative would be transmission of electricity over the existing electrical network to small-scale electrolyzers to support the widespread use of hydrogen as a fuel.
    • Hydrogen is difficult to handle, store, and transport. It requires heavy, cumbersome tanks when stored as compressed hydrogen, and complex insulating bottles if stored as a cryogenic liquid hydrogen. If it is needed at a moderate temperature and pressure, a metal hydride absorber may be needed. The transportation of hydrogen is also a problem because hydrogen leaks effortlessly from containers.
    • Some current fuel cell designs, such as proton exchange membrane fuel cells, use platinum as a catalyst. Widescale deployment of such fuel cells could place a strain on available platinum resources.[59] Reducing the platinum loading, per fuel cell stack, is the focus of R&D.
    • Electricity transmission and battery electric vehicles are far more efficient for storage, transmission and use of energy for transportation, neglecting the energy conversion at the electric power plant. As with distributed production of hydrogen via electrolysis, battery electric vehicles could utilize the existing electricity grid until widespread use dictated an expansion of the grid.

    [edit] Energy storage types

    • Chemical
    Some natural forms of energy are found in stable chemical compounds such as fossil fuels. Most systems of chemical energy storage result from biological activity, which store energy in chemical bonds. Man-made forms of chemical energy storage include hydrogen fuel, synthetic hydrocarbon fuel, batteries and explosives such as cordite and dynamite.
    • Gravitational
    Dams can be used to store energy, by using excess energy to pump water into the reservoir. When electrical energy is required, the process is reversed. The water then turns a turbine, generating electricity. Hydroelectric power is currently an important part of the world's energy supply, generating one-fifth of the world's electricity.[60]
    • Electrical capacitance
    Electrical energy may be stored in capacitors. Capacitors are often used to produce high intensity releases of energy (such as a camera's flash).
    • Mechanical

    • Pressure:
    Energy may also be stored pressurized gases or alternatively in a vacuum. Compressed air, for example, may be used to operate vehicles and power tools. Large scale compressed air energy storage facilities are used to smooth out demands on electricity generation by providing energy during peak hours and storing energy during off-peak hours. Such systems save on expensive generating capacity since it only needs to meet average consumption rather than peak consumption.[61]
    • Flywheels and springs
    Energy can also be stored in mechanical systems such as springs or flywheels. Flywheel energy storage is currently being used for uninterruptible power supplies.
    [edit] Sustainability

    The environmental movement emphasizes sustainability of energy use and development. Renewable energy is sustainable in its production; the available supply will not be diminished for the foreseeable future - millions or billions of years. "Sustainability" also refers to the ability of the environment to cope with waste products, especially air pollution. Sources which have no direct waste products (such as wind, solar, and hydropower) are seen as ideal in this regard.
    The status of nuclear power is controversial. The uranium supply might last a very long time with nuclear reprocessing, with an almost-unlimited supply from sea water available once ground based mining is exhausted.
    Fossil fuels such as petroleum, coal, and natural gas are not renewable. For example, the timing of worldwide peak oil production is being actively debated but it has already happened in some countries. Fossil fuels also make up the bulk of the world's current primary energy sources. With global demand for energy growing, the need to adopt alternative energy sources is also growing. Fossil fuels are also a major source of greenhouse gas emissions, leading to concerns about global warming if consumption is not reduced.
    Energy conservation is an alternative or complementary process to energy development. It reduces the demand for energy by using it more efficiently.

    [edit] Energy resilience


    This article needs additional citations for verification.
    Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (September 2008)
    Some observers contend that the much talked about idea of “energy independence” is an unrealistic and opaque concept. They offer “energy resilience” as a more sensible goal and more aligned with economic, security and energy realities.
    The notion of resilience in energy was detailed in the 1982 book Brittle Power: Energy Strategy for National Security.[62] The authors argued that simply switching to domestic energy would be no more secure inherently because the true weakness is the interdependent and vulnerable energy infrastructure of the United States. Key aspects such as gas lines and the electrical power grid are centralized and easily susceptible to major disruption.
    They conclude that a “resilient energy supply” is necessary for both national security and the environment. They recommend a focus on energy efficiency and renewable energy that is more decentralized.[63]
    More recently former Intel Corporation Chairman and CEO Andrew Grove has touted energy resilience, arguing that complete independence is infeasible given the global market for energy.[64] He describes energy resilience as the ability to adjust to interruptions in the supply of energy.
    To this end he suggests the U.S. make greater use of electricity.[65] Electricity can be produced from a variety of sources. A diverse energy supply will be less impacted by the disruption in supply of any one source. He reasons that another feature of electrification is that electricity is “sticky” – meaning the electricity produced in the U.S. is more likely to stay there because it cannot be transported overseas.
    According to Grove, a key aspect of advancing electrification and energy resilience will be converting the U.S. automotive fleet from gasoline-powered to electric-powered. This, in turn, will require the modernization and expansion of the electrical power grid. As organizations such as the Reform Institute have pointed out, advancements associated with the developing smart grid would facilitate the ability of the grid to absorb vehicles en masse connecting to it to charge their batteries.[66]

    0 Not allowed!



  
صفحة 1 من 3 12 3 الأخيرةالأخيرة
الكلمات الدلالية لهذا الموضوع

عرض سحابة الكلمة الدلالية

RSS RSS 2.0 XML MAP HTML