Power generation using diesel generators is already common practice - how does your system differ from conventional diesel generators?
Diesel generators convert diesel fuel into electricity using an internal combustion engine, possibly with additional utilization of the resulting waste heat. This task can be fulfilled much better in a coupled reformer-fuel cell system with modern catalytic converter technology:
- Without the emission of NOx
- Without the use of large moving engine components, thus
- Much less maintenance required
- Much lower noise emissions
- With a significantly lower heat signature (important for military and surveillance applications)
Motorized diesel generators have an optimum load point, beyond which efficiency drops rapidly. Because the efficiency of a fuel cell is less dependent on the system load, it can also be operated at partial load (away from the optimum load point) with high efficiency, unlike the engine system.
Our focus is also on optimum performance with the smallest possible size and system efficiency by utilizing all material flows. This enables us to achieve an overall system efficiency in the range of 35%, which is 10% more than for combustion engines of a comparable size (25%)!
How do you achieve the high power densities in your reformer systems?
In order to couple a diesel reformer with a PEM fuel cell, the product of autothermal reforming must be purified. This can be done in various ways:
- By pressure swing adsorption (this requires a larger installation space and is therefore rather unsuitable for land vehicles and smaller maritime applications)
- By membrane separation (the required operating pressure is quite high)
- By catalytic gas purification, essentially the carbon monoxide that is unavoidably produced during the reforming process is almost completely removed in a two-stage catalytic process.
How do you achieve the high power densities in your gas cleaning reactors?
The basic design of the IMM reactor technology for catalytic gas purification is that of a plate heat exchanger. This allows the heat generated during the gas purification reactions to be removed very efficiently.
This eliminates the need for multi-stage reactor concepts, as required for conventional fixed-bed reactors:
- Instead of two-stage water-gas shift reactors, we at IMM apply a unique single air-cooled reactor stage.
- Instead of a conventional two- or even three-stage selective oxidation, we at IMM apply a single-stage reactor with evaporation cooling.
This saves an enormous amount of installation space and control engineering effort.
The catalysts for the reforming and gas purification reactions were developed at IMM and are highly active. Our catalyst for the water-gas shift reaction is holding the world record for activity for many years – along with an extremely high stability and robustness.
Fraunhofer Institute for Microengineering and Microsystems IMM