Background

Research and Analysis

Hydrogen Fuel Cells

A little background...
In order to understand a hydrogen fuel cell, you first should understand what hydrogen is. Hydrogen is the simplest element known to man. Each atom of hydrogen has only one proton. It is also the most plentiful gas in the universe. Stars are made primarily of hydrogen. Hydrogen gas is lighter than air and, as a result, it rises in the atmosphere. This is why hydrogen as a gas (H 2 ) is not found by itself on earth. It is found only in compound form with other elements, for example, when hydrogen combines with oxygen, is water (H 2 O). Hydrogen has the highest energy content of any common fuel by weight(about three times more than gasoline), but the lowest energy content by volume (about four times less than gasoline). It is the lightest element, and it is a gas at normal temperature and pressure.

What it is...
Hydrogen Fuel Cell is an up and coming possible solution for the automotive industry.The what the hydrogen does, is it acts as a fuel to make what is similar to a battery. It has two electrodes, an anode and a cathode, separated by a membrane. Oxygen passes over one electrode and hydrogen over the other. The hydrogen reacts to a catalyst on the electrode anode that converts the hydrogen gas into negatively charged electrons (e-) and positively charged ions (H+).The electrons flow out of the cell to be used as electrical energy. The hydrogen ions move through the electrolyte membrane to the cathode electrode where they combine with oxygen and the electrons to produce water. Unlike batteries, fuel cells never run out.

How it works...
Below is a great visual reference on how the hydrogen fuel cell works. It shows how the hydrogen enters one electrode, and oxygen enters the other.



Hydrogen atoms enter the cell at the anode (negative electrode), where a catalyst (at the electrolyte) causes a chemical reaction that strips off their electrons (e-). These newly ionized hydrogen atoms (h+) now have a positive electrical charge. The negative electrons (e-) become the DC (direct current) electricity that flows through wires and cables to provide power to the load (motor). If the load requires AC (alternating current) electricity, these negative electrons must first flow through an inverter that converts them from DC to AC. Oxygen enters the cell at the cathode (positive electrode) and in some cell types (such as the Proton Exchange Membrane fuel cell), it combines there with the negative electrons (e-) returning from the load and the hydrogen ions (h+) that have traveled from the anode through the electrolyte. In other types of fuel cells, the oxygen combines with the electrons (e-) and then goes through the electrolyte to the anode and picks up the hydrogen ions (h+). The remaining waste is the result of the combination of the two hydrogen particles and the single oxygen particle, which we know is H20, or water.

**Different types...**
 Proton Exchange Membrane (PEM) - Efficiency is 40 to 50 percent at about 175 degrees F. Cell output ranges from 50 to 250 kW. The electrolyte is a flexible polymer. Their relatively low operating temperature and flexible electrolyte make them ideal for automotive use. Alakine **-** perate at about 70 percent efficiency at temperatures between 300 and 400 degrees F. Cell output range is 300W to 5kW and they use a liquid electrolyte of potassium hydroxide (KOH) and water and can potentially leak. Molten Carbonate - Operate at about 60 to 80 percent efficiency at temperatures of about 1200 degrees F. Cell output is about 200 MW. Carbonate ions from the electrolyte are depleted in the reactions and require the injection of additional carbon dioxide. Phosphoric Acid - Efficiency ranges from 40 to 80 percent at about 300 to 400 degrees F. Cell output is around 200 kW. The phosphoric acid electrolyte is corrosive to internal cell parts. Solid Oxide - Operational efficiency is about 60 percent at temperatures of 1800 degrees F. Cell output is up to 100kW. The Solid electrolyte is prone to cracking.

Some benefits...
When we compare the waste from the hydrogen fuel cell and a standard gas motor, we can see that the hydrogen fuel cell gives off a much more "eco-friendly" waste. Water is not harmful at all, whereas carbon dioxide from a gas motor is harmful to the earths atmosphere. Although the Hydrogen Fuel Cell System is a very productive method for transportation without harm to our earth's atmosphere, there are also several problems with the application, such as the power it can put out. It has been a main reason the popularity has not shot as well as it could have because it is not well designed for large automobiles. It also is known to overheat a lot more than a normal battery and this is a conflict many auto industries are facing in development currently.

Fuel cells are a very useful power source. Some examples of different items that us fuel cells are, the spacecraft, remote weather stations, large parks, rural locations, and in certain military applications. A fuel cell system that runs on hydrogen is very compact and lightweight, and it has no major moving parts. Because fuel cells have no moving parts and do not involve combustion, in ideal conditions, they can achieve up to 99.9999% reliability. This equates to around one minute of down time in a two year period.

Below you can see a great example of how the hydrogen and oxygen give energy to power something and how the byproduct of the entire process is simply water.



The impact today...
Today, there are an estimated 400 to 500 hydrogen-fueled vehicles in the U.S., mostly in California. Most of these vehicles are buses and automobiles powered by electric motors. They store hydrogen gas or liquid on board and convert the hydrogen into electricity for the motor using a **fuel cell**. Only a few of these vehicles burn the hydrogen directly (producing almost no pollution). The present cost of fuel cell vehicles greatly exceeds that of conventional vehicles in large part due to the expense of producing fuel cells. One of the main problems that hydrogen car producers are having, is the refueling situation. Customers need a place that they can refuel their hydrogen car. Currently, there are 63 hydrogen refueling stations nationwide, about half of which are located in California. This is the so-called “chicken and egg” problem that hydrogen developers are working hard to solve. Basically what they are talking about is who will buy hydrogen cars if there are no refueling stations? And who will pay to build a refueling station if there are no cars and customers?

In summary...
How a hydrogen fuel cell works, is that water undergoes electrolysis, and this separates the hydrogen from the oxygen. The oxygen disburses, and the hydrogen gets stored for power. The hydrogen provides the fuel to create a "battery". Once the hydrogen is used, it combines with the oxygen and the byproduct is water.

Overall, there is much potential in the Hydrogen Fuel Cell for an alternative way to transport the world as we know it.

Sources...
http://inventors.about.com/od/sstartinventions/ss/Physics_Illustr_2.htm http://www.greencar.com/features/hydrogen-fuel-cells/ http://alternativefuels.about.com/od/researchdevelopment/a/fuelcellhowwork.htm