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السيارات الاقتصادية **************السيارات الصديقة للبيئة !!!!!!!!!!!!!!!!!!

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  1. [11]
    حسن هادي
    حسن هادي غير متواجد حالياً
    عضو متميز
    الصورة الرمزية حسن هادي


    تاريخ التسجيل: Nov 2006
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    Hydrogen vehicle

    Hydrogen vehicle refers to a personal transportation vehicle, such as an automobile, that uses hydrogen as its on-board fuel for motive power, but can also refer to other vehicles, such as an aircraft, that use hydrogen in a similar fashion. The power plants of such vehicles convert the chemical energy of hydrogen to mechanical energy (torque) in one of two methods: electrochemical conversion in a fuel-cell or combustion :
    • In combustion, the hydrogen is burned in engines in fundamentally the same method as traditional gasoline cars.
    • In fuel-cell conversion, the hydrogen is reacted with oxygen to produce water and electricity, the latter of which is used to power an electric traction motor.
    The molecular hydrogen needed as an on-board fuel for hydrogen vehicles can be obtained through various thermochemical methods utilizing natural gas, coal (by a process known as coal gasification), liquefied petroleum gas, biomass (biomass gasification), by a process called thermolysis, or as a microbial waste product called biohydrogen or Biological hydrogen production. Hydrogen can also be produced from water by electrolysis. If the electricity used for the electrolysis is produced using renewable energy or nuclear power, the production of the hydrogen would (in principle) result in no net carbon dioxide emissions.
    Hydrogen is an energy carrier, not an energy source, so the energy the car uses would ultimately need to be provided by a conventional power plant. A suggested benefit of large-scale deployment of hydrogen vehicles is that it could lead to decreased emissions of greenhouse gases and ozone precursors. [1] The pollution generated at the point of use in the vehicle would be greatly reduced compared to conventional automobile engines. Further, the conversion of fossil fuels would be moved from the vehicle, as in today's automobiles, to centralized power plants in which the byproducts of combustion or gasification can be better controlled than at the tailpipe. However, there are both technical and economic challenges to implementing wide-scale use of hydrogen vehicles, as well as better and less expensive alternatives. The timeframe in which challenges may be overcome is likely to be at least several decades, and hydrogen vehicles may never become broadly available. [2] [3] [4][5]

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  2. [12]
    حسن هادي
    حسن هادي غير متواجد حالياً
    عضو متميز
    الصورة الرمزية حسن هادي


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    Research and prototypes

    Hydrogen powered Ford Focus


    Hydrogen does not come as a pre-existing source of energy like fossil fuels, but rather as a carrier, much like a battery. It can be made from both renewable and non-renewable energy sources. A potential advantage of hydrogen is that it could be produced and consumed continuously, using solar, water, wind and nuclear power for electrolysis. Currently, however, hydrogen vehicles utilizing hydrogen produced using hydrocarbons, produce more pollution than vehicles consuming gasoline, diesel, or methane in a modern internal combustion engine, and far more than plug-in hybrid electric vehicles.[4] This is because, although hydrogen fuel cells generate no CO2, production of the hydrogen creates additional emissions.[6] While methods of hydrogen production that do not use fossil fuel would be more sustainable,[7] currently such production is not economically feasible, and diversion of renewable energy (which represents only 2% of energy generated) to the production of hydrogen for transportation applications is inadvisable.[4]
    The recorded number of hydrogen-powered public vehicles in the United States was 200 as of April 2007, mostly in California,[8] and a significant amount of research is underway to try to make the technology viable. The common internal combustion engine, usually fueled with gasoline (petrol) or diesel liquids, can be converted to run on gaseous hydrogen. However, the more energy efficient use of hydrogen involves the use of fuel cells and electric motors. Hydrogen reacts with oxygen inside the fuel cells, which produces electricity to power the motors. One primary area of research is hydrogen storage, to try to increase the range of hydrogen vehicles, while reducing the weight, energy consumption, and complexity of the storage systems. Two primary methods of storage are metal hydrides and compression.
    High-speed cars, buses, submarines, airplanes and rockets already can run on hydrogen, in various forms at great expense. NASA uses hydrogen to launch Space Shuttles into space. There is even a working toy model car that runs on solar power, using a reversible fuel cell to store energy in the form of hydrogen and oxygen gas. It can then convert the fuel back into water to release the solar energy.[9]

    [edit] Hydrogen fuel difficulties

    For more details on this topic, see Fuel cell.
    While fuel cells themselves are potentially highly energy efficient, and working prototypes were made by Roger E. Billings in the 1960s, at least four technical obstacles and other political considerations exist regarding the development and use of a fuel cell-powered hydrogen car.

    [edit] Low volumetric energy

    Hydrogen has a very low volumetric energy density at ambient conditions, equal to about one-third that of methane. Even when the fuel is stored as a liquid in a cryogenic tank or in a pressurized tank, the volumetric energy density (megajoules per liter) is small relative to that of gasoline. Because of the energy required to compress or liquefy the hydrogen gas, the supply chain for hydrogen has lower well-to-tank efficiency compared to gasoline. Some research has been done into using special crystalline materials to store hydrogen at greater densities and at lower pressures.
    Instead of storing molecular hydrogen on-board, some have suggested that using hydrogen reformers to extract the hydrogen from more traditional fuels including methane, gasoline, and ethanol, or using reformed gasoline or ethanol to power fuel cells.[citation needed] However, using gasoline for this purpose would promote continued dependence on fossil fuels.

    [edit] Fuel cell cost

    Currently, hydrogen fuel cells are costly to produce and fragile. Scientists are studying how to produce inexpensive fuel cells that are robust enough to survive the bumps and vibrations that all automobiles experience. Also, many designs require rare substances such as platinum as a catalyst in order to work properly. Such a catalyst can also become contaminated by impurities in the hydrogen supply. In the past few years, however, a nickel-tin catalyst has been under development which may lower the cost of cells.[10] Fuel cells are generally priced in USD/kW, and data is scarce regarding costs. Producer Ballard is virtually alone in publishing such data. Their 2005 figure was $73 USD/kW (based on high volume manufacturing estimates), which they said was on track to achieve the U.S. DoE's 2010 goal of $30 USD/kW. This would achieve closer parity with internal combustion engines for automotive applications, allowing a 100 kW fuel cell to be produced for $3000. 100 kW is about 134 hp.[11]

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  3. [13]
    حسن هادي
    حسن هادي غير متواجد حالياً
    عضو متميز
    الصورة الرمزية حسن هادي


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    عملية انتاج الهيدروجين صناعيا
    نختتم موضوعنا بعملية انتاج الهيدروجين وبامكانكم متابعة الروابط المتداخلة مع كل التقدير والمنى بان يكون الموضوع مفيدا مع التقدير والمودة
    ************************************************** ***********************************
    Hydrogen production






    Hydrogen production is commonly completed from hydrocarbon fossil fuels via a chemical path. Hydrogen may also be extracted from water via biological production in an algae bioreactor, or using electricity (by electrolysis) or heat (by thermolysis); these methods are presently not cost effective for bulk generation in comparison to chemical paths derived from hydrocarbons. Cheap bulk production of hydrogen is a requirement for a healthy hydrogen economy.

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  4. [14]
    حسن هادي
    حسن هادي غير متواجد حالياً
    عضو متميز
    الصورة الرمزية حسن هادي


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    From hydrocarbons
    Hydrogen can be generated from natural gas with approximately 80% efficiency, or other hydrocarbons to a varying degree of efficiency. The hydrocarbon conversion method releases greenhouse gases. Since the production is concentrated in one facility, it is possible to separate the gases and dispose of them properly, for example by injecting them in an oil or gas reservoir (see carbon capture), although this is not currently done in most cases. A carbon dioxide injection project has been started by Norwegian company Statoil in the North Sea, at the Sleipner field.

    [Steam reforming

    Commercial bulk hydrogen is usually produced by the steam reforming of natural gas. At high temperatures (700–1100 °C), steam (H2O) reacts with methane (CH4) to yield syngas.
    CH4 + H2OCO + 3 H2 - 191.7 kJ/mol The heat required to drive the process is generally supplied by burning some portion of the methane.

    [edit] Carbon monoxide


    gasification


    Additional hydrogen can be recovered from the carbon monoxide (CO) through the lower-temperature water gas shift reaction, performed at about 130 °C:
    CO + H2O → CO2 + H2 + 40.4 kJ/mol Essentially, the oxygen (O) atom is stripped from the water (steam) to oxidize the carbon (C), liberating the hydrogen formerly bound to the carbon and oxygen.



    Biological production

    Main article: Biological hydrogen production (Algae)
    Hydrogen can be produced in an algae bioreactor. In the late 1990s it was discovered that if the algae is deprived of sulfur it will switch from the production of oxygen, i.e. normal photosynthesis, to the production of hydrogen.
    It seems that the production is now economically feasible by trespassing the 7-10 percent energy efficiency (the conversion of sunlight into hydrogen) barrier.
    Hydrogen can and is produced in bioreactors that utilize feedstocks other than algae. The most common feedstock being waste streams. The process involves bacteria feeding on hydrocarbons and exhaling hydrogen and CO2. The CO2 can be sequestered successfully by several methods, leaving hydrogen gas. A prototype hydrogen bioreactor using waste as a feedstock is in operation at Welch's grape juice factory in North East, Pennsylvania.

    [ Electrolysis


    Hydrogen from renewable resources



    Electrolysis of water
    When the energy supply is chemical, it will always be more efficient to produce hydrogen through a direct chemical path. But when the energy supply is mechanical (hydropower or wind turbines), hydrogen can be made via electrolysis of water. Usually, the electricity consumed is more valuable than the hydrogen produced, which is why only a tiny fraction of hydrogen is currently produced this way.
    When the energy supply is in the form of heat (solar thermal or nuclear), the only existing path to hydrogen is currently through high-temperature electrolysis. In contrast with low-temperature electrolysis, high-temperature electrolysis (HTE) electrolysis of water converts more of the initial heat energy into chemical energy (hydrogen), potentially doubling efficiency, to about 50%. Because some of the energy in HTE is supplied in the form of heat, less of the energy must be converted twice (from heat to electricity, and then to chemical form), and so less energy is lost. HTE has been demonstrated in a laboratory, but not at a commercial scale.

    [Photoelectrochemical Water Splitting

    Using electricity produced by photovoltaic systems offers the cleanest way to produce hydrogen. Water is broken into hydrogen and oxygen by electrolysis--a photoelectrochemical (PEC) process. Research aimed toward delveloping higher-efficiency multijunction cell technology is underway by the Photovoltaic industry.

    [ High-temperature electrolysis)

    Main article: High-temperature electrolysis
    HTE processes are generally only considered in combination with a nuclear heat source, because the other non-chemical form of high-temperature heat (concentrating solar thermal) is not consistent enough to bring down the capital costs of the HTE equipment. Research into HTE and high-temperature nuclear reactors may eventually lead to a hydrogen supply that is cost-competitive with natural gas steam reforming.
    Some prototype Generation IV reactors operate at 850 to 1000 degrees Celsius, considerably hotter than existing commercial nuclear power plants. General Atomics predicts that hydrogen produced in a High Temperature Gas Cooled Reactor (HTGR) would cost $1.53/kg. In 2003, steam reforming of natural gas yielded hydrogen at $1.40/kg. At 2005 gas prices, hydrogen cost $2.70/kg [citation needed]. Hence, just within the United States, a savings of tens of billions of dollars per year is possible with a nuclear-powered supply. Much of this savings would translate into reduced oil and natural gas imports.
    One side benefit of a nuclear reactor that produces both electricity and hydrogen is that it can shift production between the two. For instance, the plant might produce electricity during the day and hydrogen at night, matching its electrical generation profile to the daily variation in demand. If the hydrogen can be produced economically, this scheme would compete favorably with existing grid energy storage schemes. What is more, there is sufficient hydrogen demand in the United States that all daily peak generation could be handled by such plants[1].However the Generation IV reactors are not expected until 2030 and its not sure the reactors can compete by then in safety and supply with the distributed generation concept.

    [ Thermochemical production

    Some thermochemical processes, such as the sulfur-iodine cycle, can produce hydrogen and oxygen from water and heat without using electricity. Since all the input energy for such processes is heat, they can be more efficient than high-temperature electrolysis. Thermochemical production of hydrogen using chemical energy from coal or natural gas is generally not considered, because the direct chemical path is more efficient.
    None of the thermochemical hydrogen production processes have been demonstrated at production levels, although several have been demonstrated in laboratories.

    Other methods

    نأمل ان نكون قد وفقنا للاقتراب من اتمام الموضوع مع كل المودة والتقدير والله ولي التوفيق

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  5. [15]
    حسن هادي
    حسن هادي غير متواجد حالياً
    عضو متميز
    الصورة الرمزية حسن هادي


    تاريخ التسجيل: Nov 2006
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    سيارة بي إيم دابليو 7 بالهيدروجين
    1. خزان الوقود يستوعب 8 كيلوغرامات من الهيدروجين السائل
    2. خزان البنزين بسعة تبلغ 74 لترا
    3. صمام الضغط
    4. جهاز الاحتراق الداخلي الذي يشتغل بالبنزين أو الهيدروجين السائل
    تستعد شركة "بي إيم دابليو" الألمانية لصناعة السيارات لطرح النماذج الأولى للسيارات ذات المحركات التي تعمل بالهيدروجين ، متقدمة بذلك على منافسيها الآخرين.
    وتشتغل السيارة بالهيدروجين السائل المخزن في حوض مخصص لذلك الغرض. وتصل سرعتها إلى 100 كيلومتر في الساعة، في الثواني الست الأولى لإقلاع السيارة، وتقطع مسافة 300 كيلومتر بدون حاجة المحرك إلى أي تغذية.
    ويقوم المحرك بإحراق الهيدروجين ويبعث في الجو بخار الماء الصافي بدلاً من غاز ثاني أكسيد الكربون الملوث.
    وبخلاف سيارات الهيدروجين المنافسة التي طرحتها الشركات الأخرى والتي تعتمد على خلايا الوقود، فإن محرك الهيدروجين في سيارة "البي إيم دابليو" 7 يحتوي على آلية للاحتراق شبيهة بتلك الموجودة في السوق تسمح بتشغيل المحرك بالوقود العادي.

    مع المودة BMW

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  6. [16]
    حسن هادي
    حسن هادي غير متواجد حالياً
    عضو متميز
    الصورة الرمزية حسن هادي


    تاريخ التسجيل: Nov 2006
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    نأمل ان يكون الموضوع مفيدا وتقبلوا منا كل المودة والتقدير

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  7. [17]
    ابراهيم الأمير
    ابراهيم الأمير غير متواجد حالياً
    جديد


    تاريخ التسجيل: Feb 2008
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    تحية للاخوة

    بسم الله الرحمن الرحيم
    الإخوة الأحباء
    نظرا لما نعانيه من ارتفاع مفرط في اسعار النفط ومشتقاته فأنا ابحث عن طرق بديلة لما يلي
    1- التدفئه والإستخدامات المنزلية
    2- السيارات
    3- الكهرباء العامة للمنازل

    لدي افكار علمية جيدة من جهة نظري
    ارجو ممن لديه فكرة وحب التواصل ان يراسلني وعنواني هو
    ibr_amir2006***********
    مع اجمل امنياتي للجميع

    اخوكم
    ابراهيم الأمير

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