A fuel cell system just only emitted water vapour when used pure hydrogen as fuel. Otherwise, when using hydrogen from hydrocarbon reforming (like: coal, natural gas, etc), we still need conduct the emission testing to determine a system have zero emission category. According to standard that released by United Technologies Corporation (UTC) on 2002, a fuel cell system categorized as zero emission technology when just emitted smallest air pollutants, and bellow showing the parameter:

NOx ≤ 1 ppm

SO2 ≤ 1 ppm

CO2 ≤ 2 ppm

The table show the air pollution which emitted by some type of fuel cells. Note: PEM (Polymer Electrolyte Membrane), PAFC (Posporic Acid Fuel Cell), SOFC (Solid Oxide Fuel Cell), MCFC (Molten Carbonate Fuel Cell).

Beside that, fuel cell very quietly when operate, except noise from support system, such as pump, fan, compressor, etc.

Highest Efficiency

Because of fuel cell use electrochemical reaction in energy conversion – not like in carnot engine that using internal combustion reaction, hence the fuel cell efficiency not limited by operational temperature (not limited by carnot cycle). So that efficiency on fuel cell higher than conventional carnot engine, as you can see bellow:

Rapid Load-Following

Fuel cell have good characteristic to follow changing of load. When Fuel cell with pure hydrogen implemented on mechanical engine (like: DC electric motor), it showingthe quickly respons to follow changing of load.

Low Operational Temperature

Fuel cell system very suitable when implemented on automotive industry that operate at low temperature. The advantage of fuel cell are just need few minute of warmup time, reduction of operational risk at high temperature (like: cracking, material melting point, breaking, etc), improvement of thermodynamic effiiciency.

Reduction on Energy Transformation

When fuel cell used to generate electric energy, it just need few step of energy transformation, which is chemical energy to electric energy. Different with conventional carnot engine that need more step of energy transformation to generate electric energy, which are :

Chemical Energy → Thermal Energy → Mechanical Energy → Electric Energy

Fuel cell tha used on electric motor has same step energy transformation compared with carnot engine, but fuel cell promise higher effiiciency on energy tranformation.

Shortly of Hydrogen Filling

Fuel cell system not need recharge treatment like at battery. Fuel cell system just need hydrogen that filling on hydrogen storage and this process faster that recharge a battery. You can imagine filling hydrogen like when you filling gasoline at filling station on your town. Beside that, battery can not installed on vehicle with the big quantity because will increase load on that vehicle.

References:

• Matthew M. Mench, Chao-Yang Wang and Stefan T. Thynell., An Introduction to Fuel Cells and Related Transport Phenomena, Dept of Mechanical and Nuclear Engineering, Pennsylvania State University, USA, pp: 3 – 4, 24/05/2001
• David Keenan, Fuel Cell Companies, Minnesota Futurists Financial Futures SIG, USA, 10/01/2004.
• Javit Drake, Fuel Cells: Concept Today, Practical Tomorrow?, Gillette Technical Center Needham, 29/03/2005.
• Anna Monis Shipley and R. Neal Elliott, Stationary Fuel Cells: Future Promise, Current Type, American Council for an Energy-Efficient Economy, Washington D.C, March 2004.
• Bruce Tonn and Das Sujit, An Assessment of Platinum Availability for Advanced Fuel Cell Vehicles, Oak Ridge, Tenn.: Oak Ridge National Laboratory, 2001.
• United Technologies Corporation, Benefits of the PC 25 Fuel Cell Power Plant, South Windsor Conn.: United Technologies Corporation, 2002.
• Bluestein, Joel (Energy and Environmental Analysis, Inc.), Personal Communication, October 2002.
• Stefan Geiger, Fuel Cells in Austria, Italy and Switzerland � A Survey of current Developments, www.fuelcelltoday.com, 2004.
• Anonim, Fuel Cell: Technology Comparison, 09/10/2006.
• Anonim, Advantages of Fuel Cell Vehicles, 09/10/2006

Hydrogen difficult to be produced and saved in storage media. Nowdays, hydrogen production methods are very expensive dan need a lot of energy (which mean: hydrogen production has less efficiency ). To overcome this barier, many industries used hydrocarbon reforming technology to produce hydrogen from hydrocarbon. This way choose just on transition era, before we reach hydrogen era where hydrogen can take from efficient water electrolysis methods.

Contaminants Sensitivity

Fuel cell need pure hydrogen as fuel, free from contaminants. Contaminants like sulfur, mixture of carbon compound could deactivate of fuel cell catalyst and when continuing it will destroy this catalyst. Different with internal combustion engine, where contaminants not much influent the combustion reaction.

Expensive of Platinum Catalyst

Fuel cell that applied on automotive industries need platinum catalyst to perform electrochemical reaction so that fuel cell could generate electric power. Platinum is a rare metal and very expensive. Base on geological survey from USA specialist, total reserve of platinum metal on the world just 100 million kg (Bruce Tonn and Das Sujit, 2001). Today, fuel cell with installed capacity 50kW need 100 gram platinum metal as catalyst (DOE, 2000). Assume we have a good fuel cell development (include: improve the thrifty of platinum usage, slow growth of fuel cell marketplace, less demand of platinum metal), estimated before 2030 there is no more again platinum metal on the world (Anna Monis Shipley and R. Neal Elliott, 2004). For that reason, we need research and exploration to discover the alternative catalyst that have similar function with platinum metal.

Freezing

Beside fuel cell generate electricity, it also generate thermal product which very useful to prevent freezing on normal environment temperature. But, when there is extreme lowest enviroment temperature (-10 s.d -20 Celcius) so that water product will freeze on the inside of fuel cell, this bad condition could be damage for fuel cell membrane (David Keenan, 10/01/2004). For that reason, we have to design a system that could keep fuel cell environment have normal temperature.

New and Advance Technology

We need develop some alternative material and construction method so that could reduce fuel cell production. Nowdays, commercial cost of fuel cell for power generation is ~$4000/kW (Javit Drake, 29/03/2005).

By intensive research and development we hope could release a fuel cell system that have competitive cost with conventional combustion engine (on: $20/kW) and with conventional power generation (on: $1000/kW) (Matthew M. Mench, 24/05/2001). New technology will reduce cost, weight, size with improvement on performance and lifetime operation a fuel cell system. Implementation of fuel cell on automotive industries must have minimal lifetime operational 4,000 hours (equivalent with vehicle that running on 100,000 mile with speed 25 mile per hour) and on power generation industries must have minimal lifetime operational 40,000 hours (Matthew M. Mench, 24/05/2001).

Lact of Infrastructures

Hydrogen production intrastructure installed yet, just on experimental scale and prototype. The available of reliable manufacture technology and mass production are the important key to force commercial fuel cell technology.

References:

• Matthew M. Mench, Chao-Yang Wang and Stefan T. Thynell., An Introduction to Fuel Cells and Related Transport Phenomena, Dept of Mechanical and Nuclear Engineering, Pennsylvania State University, USA, pp: 3 – 4, 24/05/2001
• David Keenan, Fuel Cell Companies, Minnesota Futurists Financial Futures SIG, USA, 10/01/2004
• Javit Drake, Fuel Cells: Concept Today, Practical Tomorrow?, Gillette Technical Center Needham, 29/03/2005
• Anna Monis Shipley and R. Neal Elliott, Stationary Fuel Cells: Future Promise, Current Type, American Council for an Energy-Efficient Economy, Washington D.C, March 2004
• Bruce Tonn and Das Sujit, An Assessment of Platinum Availability for Advanced Fuel Cell Vehicles, Oak Ridge, Tenn.: Oak Ridge National Laboratory, 2001
• United Technologies Corporation, Benefits of the PC 25 Fuel Cell Power Plant, South Windsor Conn.: United Technologies Corporation, 2002
• Bluestein, Joel (Energy and Environmental Analysis, Inc.), Personal Communication, October 2002
• Stefan Geiger, Fuel Cells in Austria, Italy and Switzerland – A Survey of current Developments, www.fuelcelltoday.com, 2004
• Anonim, Fuel Cell: Technology Comparison, 09/10/2006
• Anonim, Advantages of Fuel Cell Vehicles, 09/10/2006

Components that build one fuel cell (PEM – Polymer Electrolyte Membrane case) consist of :

• Anode – negative electrode where hydrogen gas enter the cell
• Cathode – postive electride where oxygen gas or air enter the cell and water vapour exit from cell
• Chatalyst – breaking molecule of hydrogen gas into positive ion (H+) and electron (e-)
• Electrolyte Membrane – where is only H+ can pass though this material
• Interconnect – connect between cells become a stack (usually consist about 100 to 200 cells)

This a simple explanation how fuel cells can generate DC electric energy :

Hydrogen gas flow though anode plate, then catalyst on anode side perform the hydrogen-oxidation reaction so hydrogen gas separated into H+ and electrons. Then H+ ions pass though the electrolyte membrane going to cathode side and the electrons flow though external-circuit. Electrons flowing on the external circuit are we know as DC electric energy and can be used directly for DC electric motor, DC lamp, etc. On the cathode side, electrons from external-circuit and oxygen gas perform the reduction reaction to making oxygen ions. Then the end occur reaction between hydrogen and oxygen ions become water vapour as the product. You can see bellow the reduction-oxidation reaction on the fuel cells :

There are many type of fuel cells base electrolyte type that used, that are :

• PEMFC (Polimer Electrolyte Membrane Fuel Cell)
• AFC (Alkaline Fuel Cell)
• PAFC (Phosphoric Acid Fuel Cell)
• MCFC (Molten Carbonate Fuel Cell)
• ITSOFC (Intermediate Temperature Solid Oxide Fuel Cell)
• SOFC (Solid Oxide Fuel Cell)
• DMFC (Direct Methanol Fuel Cell)

Each type of fuel cell have advantage and disavantage, depend where it will used for some applications. When you are using fuel cell for portable device (like laptop or mobilephone) or your motorcycle, you preferred use PEMFC. But when you are on remote area where there no electric availability, you should use SOFC or DMFC to generate electricity for your house.

For all of fuel cell type, we still have mainly problem that should be solve, which are : highly cost of catalyst and primary components, we still need optimize the efficiency of hydrogen production and make ecomonical analysis to perform this technology enter world marketplace. We should start now quickly!