Term Paper on "H2 O2 Fuel Cell"

>Typically, the fuel cell is an energy conversion device that could efficiently use and capture the hydrogen power and it consists of electrolyte between two electrodes (an anode and a cathode). Typically, hydrogen ions generally moves through the cathode, electrode and combine with the electrons and oxygen to produce water. With this chemical process, fuel cells never run out.

Fuel cell could be used as back up power for distributed power generation, and remote location. More importantly, fuel cell has ability to power any portable application that uses batteries, portable generators and hand-held devises. Fuel cell is also a power energy device that could power transportation, which include trucks, personal vehicles, marine vessels and buses. Thus, hydrogen-oxygen fuel cell plays important roles in replacing the imported petroleum currently being used to power the cars and trucks.

One of the important benefits of hydrogen-Oxygen fuel cell is that they are pollution free and they are two or three times more efficient than traditional combustion technologies. A conventional combustion energy generates electricity between 33 and 35%. However, fuel cell systems generate electricity at the level reaching 60% efficiencies and higher with cogeneration. Under normal driving conditions, the gasoline engine in a conventional motor car is less than 20% efficient to convert chemical energy into gasoline power in order to move vehicles from one place to the other. On the other hand, hydrogen-oxygen fuel cell vehicles are much more energy efficient. They have ability to use between 40 and 60% of the fuel's energy leading to a 50% reduction in fuel consumption compared to the traditional convectional vehicle using a gasoline internal combustion engine. As being revealed in Table 1, fuel is more efficient than other power generation systems.

Table 1. Fuel Cell Comparison with other Power Generating Systems

Diesel: Reciprocating Engine

Turbine generator

Photovoltaic

Wind turbine

Fuel cells

Capacity range

500 kW -- 50 MW

500 kW -- 5 MW

1 kW -- 1 MW

10 kW -- 1 MW

200 kW -- 2 MW

Efficiency

35%

29 -- 42%

6 -- 19%

25%

40 -- 85%

Capital cost ($/kW)

200 -- 350

450 -- 870

1500 -- 3000

O & M. cost ($/kW)

0.005 -- 0.015

0.005 -- 0.0065

0.001 -- 0.004

0.01

0.0019 -- 0.0153

Typically, fuel cell is a dynamic and promising replacement of fossil fuels. It is effective to generate energy in places where there are no access to public grid or places requiring huge cost to generate electricity. Moreover, fuel cells have ability to deliver UPS (uninterrupted power supply) and are suited for variety of application because fuel cells have ability to move quietly and having fewer moving parts.

Objective this research is to investigate the basic technologies of Hydrogen-Oxygen fuel cell.

History

A German scientist named Christian Friedrich in 1838 first discovered the fuel cells and his findings were published in one of the scientific magazines of the time. However, Sir William Robert Grove and a Welsh scientist demonstrated the first fuel cell in Philosophical Magazine and Journal of Science on February 1839 based on the discovery of Christian Friedrich. (Grove, 1842). In 1955, in the United States, a chemist named Thomas Grubb modified the original fuel cell for the GE (General Electric) company. The GE chemist used a "sulphonated polystyrene ion-exchange membrane as the electrolyte." (Toria, et al. 2008 P. 8). In 1958, Leonard Niedrach, another GE chemist, devised a method to deposit platinum into the membrane, which served as catalysts for the reaction of oxygen reduction and hydrogen oxidation reactions. The usefulness of fuel cell during the period made GE to develop the technology with NASA. (Toria, et al. 2008 ). In 1959, Harry Ihrig successfully built a 15 kW fuel cell tractor, which was demonstrated across the United States state fairs.

In the United Kingdom, Francis Thomas Bacon, a British engineer successfully developed a 5 kW stationary fuel cell in 1959. In the late 1959, Bacon and his team successfully demonstrated a practical five-kilowatt unit of fuel cell capable of powering a welding machine. In 1960s, Pratt and Whitney secured Bacon's U.S. patents and developed hydrogen and oxygen fuel cell that could be used for space program as well as supplying electricity and drinking water. In 1991, Roger Billings developed the first hydrogen fuel to power an automobile. For several years, UTC Power is the first company to manufacture and commercialize stationary fuel cell systems, which are generally used for power plants in hospitals and many large office buildings. Meanwhile, UTC continues to be a sole and major supplier of fuel cells to NASA for the space vehicles, Space Shuttle program and Apollo missions.

Basic Technology of Hydrogen-Oxygen Fuel Cell

All fuel cell technologies have the same configurations using combination of an electrolyte and two electrodes to generate power. Typically, the electrolyte determines the type of chemical reactions that would take place within the fuel cells. While there is different range of designs for the oxygen-hydrogen fuel cells, however, they all operate using the same basic principles. The major difference between various fuel cell designs is their chemical characteristics. Mekhilefa, et al. (2012) argues that hydrogen-oxygen fuel cell deliver heat and power via an electrochemical reaction which is actually a reversed electrolysis reaction. The electrochemical reaction happens between oxygen and hydrogen to form water.

The equation (1) reveals the electrochemical reaction shown the basic operating principle of a fuel cell.

Equation (1)

2H2 (g) + O2 (g) ? 2H2O + energy

Hydrogen + oxygen ? water + (electrical power +heat) (1)

As being revealed in Fig 1, a fuel cell consists of four main parts, which include cathode, anode, external circuit and electrolyte. At the node level, hydrogen is oxidized into electrons and protons. While at the cathode, the oxygen is reduced to oxide species and produces a reaction to form water.

"Depending on the type of electrolyte, either oxide ions or protons ions are transported through an ion-conductor electron-insulating electrolyte while electrons travel through an external circuit to deliver electric power. Nevertheless, fuel cells often produce only very small amount of current due to diminutive contact area between electrodes, electrolyte and the gas. Another problem to be considered is the distance between electrodes." (Manahana et al. 2011 P. 982).

Fig. 1: A Fuel Cell Operating Principle

However, there is a need to consider a thin layer of electrolyte with flat porous electrodes for electrolyte and the gas penetration. The reaction to generate power using hydrogen-oxygen cell fuels is different and the chemical reactions depend on the different types of fuel cells. Within an acid electrolyte fuel cell, protons and electrons (H+) are released from an ionizing hydrogen gas at the anode electrode.

"The generated electrons pass though an electrical circuit and travel to the cathode while protons are delivered via electrolyte. This exchange releases electrical energy. Simultaneously at the cathode side, the water is forming as a result of the reaction between electrons from electrode and protons from electrolyte." (Mekhilefa, Saidurb, Safari, 2012 P. 982).

The reactions occurring between anode and cathode are revealed in the following equations:

Equation (2)

Anode: 2H2 ? 4H+ + 4e

Equation (3)

Cathode: O2 + 4e? + 4H +? 2H2O

The proton exchange membranes are acid electrolytes and some polymers, which contain free H+ ions. They allow the H+ ions passing through it because they provide effective proton delivering functions. Thus, there is a lost of electrical current when electrons are delivered through the electrolytes. Evaluation of different fuel cell technologies provides a… READ MORE