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Reforming fuel to obtain hydrogen
The problems with pure hydrogen lead to attempts to use traditional fuel – even gasoline – to produce the hydrogen for the fuel cell. Engines built on this principle are still more fuel efficient and – using appropriate measures – less polluting that traditional engines.
Fuel reformers are used to split the required hydrogen atoms from the larger molecules of traditional fuels like propane, methanol even diesel oil or gasoline.
The whole picture
We are thus looking at three major components which participate in the power generation with fuel cells:
- the cell itself
- the reformer
- the external circuit (car engine etc.)
The reformer produces hydrogen from other fuel. It is not required if hydrogen is used directly. The external circuit consists of any application, which uses the electrical current generated by the cell.
To avoid the loss of efficiency through the reforming process, researchers also work on improving the storage facilities for hydrogen.
Efficiency of fuel cell systems
Efficiency refers to how much of the released energy is actually put to purposeful use. Car engines provide an efficiency of about 20%. That means that 80% of the energy released by burning the fuel is lost through heat and friction and only 20% can be used to drive the car.
To answer the question for the fuel cell we look at each of the component of the system.
The fuel cell itself has an efficiency of 80%. However, if we use a reformer to produce hydrogen from methanol, for example, the efficiency drops to about 30 – 40 %. Electrical motors are also not 100% efficient, a reasonable value is 80%. That results in an overall efficiency of 24 – 32 %. Compared to traditional cars this is still an improvement of 20 – 60 %.
Battery powered cars have an efficiency of about 70%. But that does not include the method used for charging the battery. The required electricity might have been generated by burning coal. Coal based power plants have an efficiency of 40%. The overall efficiency thus is 28%.
In large stationary systems it is practical to use hydrogen directly, because the large storage facilities are not a problem here. The efficiency of such a system is then 80%, not considering the external use of the energy.
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