Post 8 : Fuel Cell

Fuel  Cell

1. PEMFC 

     Fuel cell is an electrochemical device that generates electricity by combining hydrogen(H2) and oxygen(O2). If you want to keep a fuel cell generating electricity, just add more H2 and O2 to it. In other words, fuel cells won't go die, as long as we supply gas to them. Let's us look at the most promising kind of fuel cell, Polymer Electrolyte Membrane Fuel Cells (PEMFC). Among all fuel cells, PEMFC is more likely to be commercialized. The picture below shows a PEMFC's stucture.

pic. 1

 

2. How it works

     1. electrode : The anode conducts the electrons, so that they can go to the external circuit.

                           The cathode conducts the electrons back from the external circuit to the catalyst.

    

     2. electrolyte : In a PEMFC, the electrolyte is the proton exchange membrane. It only allows positively charged ions to go through. In this case, the proton exchange membrane let protons(H+) move from anode to cathode, and keep electrons from going into eletrolyte.

 

     3. catalyst : A catalyst is a substance whuch, without itself changing, quickens chemical reaction.

 

 

     The reaction occuring in a PEMFC is given by the picture below.First, hydrogen gas enters anode. When a H2 molecule comes to catalyst, it splits into two protons and two electrons. Then, the electrons go to the external circuit, and the protons move toward cathode. When electrons come to cathode from the external circuit, they react with protons and O2 molecules and form water and heat. 

 

pic.2

 

 3. Hydrogen cars

      According to this video, the Honda FCX clarity has been driven by people in the U.S. and Japan, and it is now testing in some European countries. There is a term called "Fuel Cell Stack" in this video that might confuse you. Since a single fuel cell can only generate electricity of 0.7 volts which can only light up some small device like a bulb. To increase the voltage of the electricity generated, we let the cell stacked in series.
      There are lots of advantage of using hydrongen cars. They are efficient, quite and they don't have any emission. What's more, their performance is good. Take the Honda FCX clarity for example, it performs very well at its top speed of 100 miles per hour!!(based on the video)

 

 

referance :

pic.1 and pic.2 : drawn by me             

 

 

 

 

 

 

Post 7 : Hydrogen Economy

Hydrogen Economy

1. Definition

       "The hydrogen economy is a proposed system of delivering energy using hydrogen. The term hydrogen economy was coined by John Bockris during a talk he gave in 1970 at General Motors (GM) Technical Center."(1#)

 

2. Using hydrogen as a kind of fuel

     A process of using hydrogen as a fuel can be divided into three parts. They are production, storage of hydrogen and generation of electricity. 

      

(1) production of hydrogen

     Actually, there are tons of ways to produce hydrogen. I will only introduce two of them. One is "steam reforming" and the other one is "electrolysis".

 

steam reforming : Use hot steam to separate hydrongen from hydrocarbon(碳氫化合物). This method is the cheapest one among all hydrogen-production so far. It is obviously that this process need a lot of energy(heat). However, if the energy used in this production come from fossil fuel, the goal of "zero-emission" won't be achieved. Thus, it is quite a challenge of this method.

 

 

pic.1

electrolysis : Eletrolyze(電解) water to obtain hydrogen and oxygen. Since water is a weak electrolye, so we often add some strong electrolye, such as acid, base and salt to provide enough ions. Notice that this process need electricity. Green energy like solar power and wind power are ideal sources of the electicity needed. However, as I mention in my previous post, we haven't found economic way to take advantage of these green energy yet. Fossil fuel is still the cheapest fuel so far.

 

 

 

(2) storage of hydrogen

 

     Since hydrogen is a dangerous gas, the storage of hydrogen is very difficult. The most common way to store hydrogen is to fill hydrogen into a iron jar with high pressure (about 100 atm). I think you guys are familiar with the gas storage tank in our campus. And there is also a method of  storing hydrogen with a kind of alloy(合金) called "hydrogen storage metal". It is said that we can use lower pressure to store hydrogen through this alloy.

 

 

 pic.2

 

 

(3) generation of electricity

 

     It will too much content, if I introduce the way of generating electricity by hydrogen in this post.(I promiss I will talk anout it in next post) So, I will talk about one of the example of using hydrogen as a fuel, hydrogen car.  A car hydrogen car(pic.3) is powered totally or partly by hydrogen fuel cell(I will talk more about it next time). Just like cars using fossil fuel, hydrogen car also need "gas" stations(pic.4) to fuel up.

 

 pic.3

 

 

 

pic.4

 

 







   

 

 reference:
1# : http://zh.wikipedia.org/zh-tw/%E6%B0%AB%E8%83%BD
pic.1 : drawn by myself
pic.2 : http://www.hightech.url.tw/index.php/2012-06-06-14-12-38/29-green-energy/217-hydrogen-storage
pic.3 : http://big5.chinabroadcast.cn/gate/big5/auto.cri.cn/261/2013/10/16/461s119799.htm
pic.4 : http://www.carnews.com/article.php?id=11062

Post 6: Our Mighty Sun

 Our Migthy Sun

1. sun : the center of the solar system

        "Sun is the star of our solar system, its diameter is about 1392684km (about 109 times of that of earth!!!), and its mass is about 1.989*10^30 kg(about 3.3*10^5 times of that of earth!!!)"(#1). Let me give you an idea about the size of sun. If our earth is as big as a golf ball,that you can easily hold in hands, then sun will be as big as the tuned mass dumper(阻尼器) of Taipei 101!

 

pic.1

 



 

          Although the mass and volume of sun are both enormous, its density is only 1.410 g/cm^3 which is around a quarter of that of earth. The density of sun is lower than that of earth, because sun is mainly composed of "light" element, such as Hydrogen and Helium. The picture below shows the composition of sun.

pic.2

            If we take sun as an power generator, then Hydrogen will be the fuel. The reaction that generates tons of light and heat is called "Nuclear Fusion." I will just introduce nuclear fusion shortly at here, if you are really intrested in it, you can visit this website http://atropos.as.arizona.edu/aiz/teaching/a250/pp.html.  Four proton(氫原子核) are converted into a Helium's nucleus(氦原子核) and energy. In fact,  a Helium's nucleus is a little bit lighter than four proton, that is, some mass "disappear" during the reaction. By mass-energy equivation, mass can be converted into energy. Thus the mass dose not just vanish during nuclear fusion, it is just transfered into energy.       

 

 

 

pic.3

 2. Solar power on earth

      Sun is a very kind, generous man, "the power he gives us is ten thousand times of the energy we use per year!"(#2) Remeber that I mentioned almost all green energy come from sun at my first post? Now, let me show you this amazing fact by the pcture below. It's a pity that we can't take advantage of solar power very well because we haven't developed a method to harness it efficiently. However, witnessing a lot of advanced coutries invest a lot of money in developing solar power, I am conviced that a revolution of energy will take place in the near future!

 

pic.4

 

 

 

reference:

#1:  http://en.wikipedia.org/wiki/Sun

#2: 瑞昇文化 <用再生能源打造非核家園>

pic.1: golf ball : http://www.zazzle.com/golf_ball_sticker-217715007674811102

          101 TMD : http://chinese.engadget.com/2008/08/27/3c-101-top/

pic.2:  http://www.solarviews.com/eng/sun.htm#views   (statistic)

pic.3: http://atropos.as.arizona.edu/aiz/teaching/a250/pp.html

pic.4: 瑞昇文化 <用再生能源打造非核家園> (statistic)

          http://www.nipic.com/show/3/9/7a147a794aaf74c6.html (animals)