Renewable Technologies >> Fuel Cells
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 Fuel Cells

What are fuel cells?
Fuel cells convert fuel and air directly to electricity, heat and water in an electrochemical process. Unlike conventional engines, they do not burn the fuel and run pistons or shafts, and so have fewer efficiency losses, low emissions and no moving parts.
 
What are the different types of fuel cells?
There are several different types of fuel cells but they are all based around a central design, which consists of two electrodes (electrical conductors), a negative anode and a positive cathode. These are separated by a solid or liquid electrolyte that carries electrically charged particles between the two electrodes. A catalyst, such as platinum, is often used to speed up the reactions at the electrodes.
 
Fuel cells are classified according to the nature of the electrolyte and their operating temperature. Each type requires particular materials and fuels and is suitable for different applications. Namely,

Electrolyte
Temperature (C)
Alkaline (AFC)
90
Proton Exchange Membrane (PEMFC)
80-100
Direct methanol fuel cell (DMFC)
90
Phosphoric acid (PAFC)
140
Molten carbonate (MCFC)
800
Solid oxide (SOFC
800-1000
Regenerative fuel cell
 
 

What is the principle on which fuel cells operate?
A fuel cell consists of an electrolyte sandwiched between two electrodes. Oxygen passes over one electrode and hydrogen over the other, generating electricity, water and heat.
A fuel cell system that includes a "fuel reformer" can use the hydrogen from any hydrocarbon fuel. On the other hand, high temperature fuel cells do not need a fuel reformer and can directly use fossil fuels such as natural gas, coal gas, etc. Since the fuel cell relies on chemistry and not combustion, emissions from this type of system are still much smaller than emissions from the cleanest fuel combustion processes.
 
What are the current uses of fuel cell technology?
Currently, the cost of fuel cells is too high for them to be put in general use. Ongoing research aims to reduce the cost and thus increase demand.
 
Overview of the technology
A fuel cell is an electro-chemical energy converter. At the simplest conceptual level it combines hydrogen with oxygen to produce water and electricity. As it is essentially an electro-chemical device, it functions rather like a battery but, unlike a battery, it doesn't store the energy itself. It is a flow process which draws liquid or gaseous fuel from a separate tank and if necessary converts it to hydrogen in a reformer. The hydrogen is then combined with oxygen from air in the fuel cell to produce water and electricity. The energy conversion process in the fuel cell is therefore intrinsically clean and silent.
 
A fuel cell generally uses hydrogen as a fuel but other fuels such as natural gas, methanol and even coal can also be used. However, in most fuel cell types these fuels must first be transformed into hydrogen by means of a reformer or a coal gasifier. The direct outputs from fuel cells are electrical power and heat. Depending on the fuel cell type, it is possible to deliver electricity and heat from 80C to 800C.
 
What are the various aspects of the technology and its applications?
The central working part of a Proton Exchange Membrane (PEM) fuel cell is the membrane electrode assembly, which is a layered structure consisting of an anode, polymer electrolyte membrane and cathode. Hydrogen gas is fed to the anode and diffuses through it to a thin platinum catalyst layer at the boundary between the anode and polymer membrane. Here the hydrogen is converted into protons and electrons. At the cathode, the protons and electrons come together again and combine with oxygen from air to form water, which is carried away. Heat is generated in the process.
 
What are the key advantages of fuel cells?
A fuel cell is energy efficient and emits few pollutants.
Its additional intrinsic advantages are the quiet operation of electro-chemical energy conversion and the lack of moving/wearing parts. Its flexibility to vary the capacity or to use different fuel makes it very versatile and to develop a wide range of modular systems. These can be adapted to a variety of markets.
 
The fuel cell's efficiency, versatility, multi-fuel capability and modular structure make it uniquely suited for use in a wide variety of stationary, vehicular and portable energy/power applications. Fuel cell cars using hydrogen as a fuel only emit water vapour - they do not emit pollutants Those using other fuels produce near-zero emissions.
The benefits are national energy security, cleaner air, and economic opportunity.
 
What is the future potential of fuel cells technology?
Fuel cells in vehicles combine very high-energy efficiency with zero exhaust emissions and potentially low noise without diminishing its performance and range.
 
In the medium to long term, fuel cells have a strong energy saving potential for decentralised co-generation in households and buildings and for power production.
 
In the long term they could replace a large part of the current combustion systems in all energy end use sectors.
 
What does it offer the EU specifically?
The acquisition and exploitation of fuel cell technology is of great importance for the European Union's continued economic prosperity.
 
How does it contribute to achieving EU objectives?
Fuel cells are strategically important for key European economic, social, environmental and energy issues. These include:
  • Providing security of supply and diversification of EU primary energy sources;
  • Promoting sustainable development;
  • Reducing pollutant emissions and greenhouse gases;
  • Providing cost-competitive clean energy for improving industrial competitiveness and facilitating the full liberalisation of the energy market;
  • Meeting the growing demand for energy in developed/ industrialised countries in a secure and sustainable way; and
  • Reinforcing the trend towards decentralised electricity supply.
A look into the future
 
What are the future applications of fuel cells?
The ultimate goal of fuel cell research is to produce a totally non-polluting mobile, stationary, or portable power generator. Fuel cells generally need a supply of pure hydrogen in order to operate and the ideal solution is to generate hydrogen by non-polluting and renewable methods, such as from solar power, and to supply this directly to the fuel cell. However, this is currently unrealistic, so another way of supplying hydrogen must be developed.
 
What is the use of this technology in the short, medium and long term?
Fuel cell technology is an emerging technology which is expected, in the medium to long term, to replace a large part of the current combustion system in industry, buildings and road transport.
 
In the long term, fuel cells and hydrogen are expected to form an integral part of RES- based energy supply, with hydrogen as the major energy carrier.
 
What are the research requirements?
The medium and long-term goals for fuel cell technology are a reduction in the cost of fuel cell production; use in buildings, in vehicular and decentralised electricity production, and advanced materials research into low and high temperature fuel cells.
 
How can we develop a stronger market for fuel cell technology?
In view of the huge potential market, the competitiveness of EU industry is a major issue. Currently, US and Japanese fuel cell companies greatly exceed EU fuel cell manufacturers in number, size and experience. Today, public spending for European fuel cell research amounts to approximately 60 million a year which is far below that of the US and Japan. Strong EU support for better-integrated European research is a prerequisite for new companies to become competitive with US and Japanese manufacturers.
 
At the same time as researching technologies, the European Union must take an overall prospective, creating a stable commercial environment within which technological exploitation can occur.
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