feul cells - بيوتات الكيمياء التعليمية

 
 

اخر المواضيع : الموضوع : الاستراتيجيات الحديثة فى الإدارة العليا وكيفية صناعة القرار   ( الكاتب : مركز الريادة     الزيارات : 10     الردود : 0 )         الموضوع : الكيميائيون ... نوادر و أمثال (الجزء الثاني))   ( الكاتب : طالب علم4     الزيارات : 3172     الردود : 7 )         الموضوع : تفـــاعل الإضـــافة في الألكينـــات .." فــــــــلاش "   ( الكاتب : ابو ياسين ع     الزيارات : 2007     الردود : 1 )         الموضوع : لو سمحتوا جداً محتاج الجواب ؟ الله يجزاكم الجنة .   ( الكاتب : bytocom     الزيارات : 27     الردود : 1 )         الموضوع : سؤال:مالفرق بين dna &rna?   ( الكاتب : Candle     الزيارات : 90     الردود : 2 )         الموضوع : خلية جلفانية وقياس جهد الخلية   ( الكاتب : ابو زاملي     الزيارات : 8699     الردود : 34 )         الموضوع : اختبار دوري3 الفصل 3 كيمياء الصف الثالث المنهج المطور   ( الكاتب : العنادطبعي     الزيارات : 954     الردود : 4 )         الموضوع : *^ امتحان نهائي كيمياء الفصل الدراسي الثاني - 1433 هـ ^*   ( الكاتب : dsirdah     الزيارات : 362     الردود : 1 )         الموضوع : لو أتيح لك أن تكتب عبارة واحدة ماذا ستكتب؟؟؟   ( الكاتب : akash     الزيارات : 7723     الردود : 131 )         الموضوع : انجازي بمدرستي ....معرض العلوم والتكنولوجيا   ( الكاتب : akash     الزيارات : 156     الردود : 1 )         
عودة   بيوتات الكيمياء التعليمية > ... > خدمات الطلاّب

عدد الضغطات : 9,393
إضافة رد
 
أدوات الموضوع
  #1   -->
قديم 21-05-2006, 09:53 PM
الصورة الرمزية لـ zeeko
zeeko zeeko غير متصل
كيميائي
 
تاريخ الانتساب: 10 2004
المكان: اليمن
مشاركات: 41
zeeko على طريق التميز و النجاح
افتراضي feul cells

الأخوه الأعزاء
لدي بحث عن خلايا الوقود فهل ممكن الحصول علي المساعده.............
رد مع اقتباس
  #2   -->
قديم 24-05-2006, 03:16 PM
NAWAF NAWAF غير متصل
كيميائي
 
تاريخ الانتساب: 05 2004
مشاركات: 27
NAWAF على طريق التميز و النجاح
افتراضي


› Introduction to How Fuel Cells Work

Photo courtesy Ballard Power Systems
A prototype fuel-cell car

You may have heard a lot recently about fuel cells. According to many news reports, we may soon be using the new energy-saving technology to generate electrical power for our homes and cars. The technology is extremely interesting to people in all walks of life because it offers a means of making power more efficiently and with less pollution. But how does it do this?

In this article, we'll take a quick look at each of the existing or emerging fuel-cell technologies. We'll detail how one of the most promising technologies works, and we'll discuss the potential applications of fuel cells.





What is a Fuel Cell?

If you want to be technical about it, a fuel cell is an electrochemical energy conversion device. A fuel cell converts the chemicals hydrogen and oxygen into water, and in the process it produces electricity.
The other electrochemical device that we are all familiar with is the battery. A battery has all of its chemicals stored inside, and it converts those chemicals into electricity too. This means that a battery eventually "goes dead" and you either throw it away or recharge it.

With a fuel cell, chemicals constantly flow into the cell so it never goes dead -- as long as there is a flow of chemicals into the cell, the electricity flows out of the cell. Most fuel cells in use today use hydrogen and oxygen as the chemicals.


The fuel cell will compete with many other types of energy conversion devices, including the gas turbine in your city's power plant, the gasoline engine in your car and the battery in your laptop. Combustion engines like the turbine and the gasoline engine burn fuels and use the pressure created by the expansion of the gases to do mechanical work. Batteries converted chemical energy back into electrical energy when needed. Fuel cells should do both tasks more efficiently.

A fuel cell provides a DC (direct current) voltage that can be used to power motors, lights or any number of electrical appliances.

There are several different types of fuel cells, each using a different chemistry. Fuel cells are usually classified by the type of electrolyte they use. Some types of fuel cells work well for use in stationary power generation plants. Others may be useful for small portable applications or for powering cars.

The proton exchange membrane fuel cell (PEMFC) is one of the most promising technologies. This is the type of fuel cell that will end up powering cars, buses and maybe even your house. Let's take a look at how they work...


قام بآخر تعديل NAWAF يوم 24-05-2006 في 03:18 PM.
رد مع اقتباس
  #3   -->
قديم 24-05-2006, 03:24 PM
NAWAF NAWAF غير متصل
كيميائي
 
تاريخ الانتساب: 05 2004
مشاركات: 27
NAWAF على طريق التميز و النجاح
افتراضي

Proton Exchange Membrane
The proton exchange membrane fuel cell (PEMFC) uses one of the simplest reactions of any fuel cell. First, let's take a look at what's in a PEM fuel cell:





Figure 1. The parts of a PEM fuel cell


In Figure 1 you can see there are four basic elements of a PEMFC:

The anode, the negative post of the fuel cell, has several jobs. It conducts the electrons that are freed from the hydrogen molecules so that they can be used in an external circuit. It has channels etched into it that disperse the hydrogen gas equally over the surface of the catalyst.
The cathode, the positive post of the fuel cell, has channels etched into it that distribute the oxygen to the surface of the catalyst. It also conducts the electrons back from the external circuit to the catalyst, where they can recombine with the hydrogen ions and oxygen to form water.
The electrolyte is the proton exchange membrane. This specially treated material, which looks something like ordinary kitchen plastic wrap, only conducts positively charged ions. The membrane blocks electrons.
The catalyst is a special material that facilitates the reaction of oxygen and hydrogen. It is usually made of platinum powder very thinly coated onto carbon paper or cloth. The catalyst is rough and porous so that the maximum surface area of the platinum can be exposed to the hydrogen or oxygen. The platinum-coated side of the catalyst faces the PEM.





Figure 2 shows the pressurized hydrogen gas (H2) entering the fuel cell on the anode side. This gas is forced through the catalyst by the pressure. When an H2 molecule comes in contact with the platinum on the catalyst, it splits into two H+ ions and two electrons (e-). The electrons are conducted through the anode, where they make their way through the external circuit (doing useful work such as turning a motor) and return to the cathode side of the fuel cell.

Meanwhile, on the cathode side of the fuel cell, oxygen gas (O2) is being forced through the catalyst, where it forms two oxygen atoms. Each of these atoms has a strong negative charge. This negative charge attracts the two H+ ions through the membrane, where they combine with an oxygen atom and two of the electrons from the external circuit to form a water molecule (H2O).

This reaction in a single fuel cell produces only about 0.7 volts. To get this voltage up to a reasonable level, many separate fuel cells must be combined to form a fuel-cell stack.

PEMFCs operate at a fairly low temperature (about 176 degrees Fahrenheit, 80 degrees Celsius), which means they warm up quickly and don't require expensive containment structures. Constant improvements in the engineering and materials used in these cells have increased the power density to a level where a device about the size of a small piece of luggage can power a car.


رد مع اقتباس
  #4   -->
قديم 24-05-2006, 03:25 PM
NAWAF NAWAF غير متصل
كيميائي
 
تاريخ الانتساب: 05 2004
مشاركات: 27
NAWAF على طريق التميز و النجاح
افتراضي

رد مع اقتباس
  #5   -->
قديم 24-05-2006, 03:27 PM
NAWAF NAWAF غير متصل
كيميائي
 
تاريخ الانتساب: 05 2004
مشاركات: 27
NAWAF على طريق التميز و النجاح
افتراضي

Table of Contents:
› Introduction to How Fuel Cells Work
› What is a Fuel Cell?
› Proton Exchange Membrane
› Problems with Fuel Cells
› Efficiency of Fuel Cells
› Gasoline and Battery Power
› Surprised?
› Other Types of Fuel Cells
› Automobiles
› Portable Power
› Buses
› Home Power Generation
› Large Power Generation
› Lots More Information
› Shop or Compare Prices
رد مع اقتباس
  #6   -->
قديم 31-05-2006, 09:07 PM
الصورة الرمزية لـ zeeko
zeeko zeeko غير متصل
كيميائي
 
تاريخ الانتساب: 10 2004
المكان: اليمن
مشاركات: 41
zeeko على طريق التميز و النجاح
افتراضي

الف الف شكر أخي العزيز علي تعاونك هذا وإنشاء الله يقدرني الله أرد لك هذا الجميل
رد مع اقتباس
إضافة رد


زوار هذا الموضوع الآن : 1 (0 عضو و 1 ضيف)
 
أدوات الموضوع

ضوابط المشاركة
غير مصرّح لك بنشر موضوع جديد
غير مصرّح لك بنشر ردود
غير مصرّح لك برفع مرفقات
غير مصرّح لك بتعديل مشاركاتك

وسوم vB : نشيط
كود [IMG] : نشيط
كود هتمل : خامل

الانتقال السريع


التوقيت حسب جرينتش +3. الساعة الآن 01:01 PM.


Powered by: vBulletin® Version 3.8.7 Copyright ©2000-2014, Jelsoft Enterprises Ltd.
Translated By vBulletin®Club©2002-2014
Ads Management Version 3.0.1 by Saeed Al-Atwi