It converts chemical energy directly into electrical energy and is, on the face of it, simple.
Reality is that there still hasn’t been a real market breakthrough for the fuel cell; the Achilles heel being over complexity.
However, Fraunhofer and Vaillant have developed what they say is a simple fuel cell device for home use.
“One always speaks of a fuel cell system,” says Dr Matthias Jahn from the Fraunhofer Institute for Ceramic Technologies and Systems (IKTS) in Dresden.
“But a single cell doesn’t produce enough voltage to obtain a sufficient electrical power.
“In a fuel cell stack, several cells are connected one to the other. Each is about the size of a CD. We call the groups, stacks.”
Fuel cells convert natural gas directly into electrical energy. They are many times more efficient than combustion engines, such as the car engine.
These require an intermediate step. First, they convert chemical energy into thermal energy (heat) and mechanical energy (force). In the process, a large portion of the originally available energy is lost.
Together with the heater manufacturer Vaillant, the IKTS has developed a compact, safe and sturdy fuel cell system that generates electricity and heat in private households from natural gas.
The researchers were responsible for the construction of the prototype, the design of the overall system, design of the ceramic components and development of the reformer and the afterburner.
A number have been built and are currently being tested in private households under the Callux programme, which is Germany’s biggest practical test for fuel cell heating systems for domestic use.
They are described as being as compact as classical gas heaters that only produce heat. Moreover, they can comfortably be mounted on a wall and be easily maintained.
With an output of one kilowatt, they cover the average current consumption for a four-person household.
The German Federal Ministry of Transport and Digital Infrastructure BMVI is promoting Callux.
Currently, in the European demonstration project ene.field, about 150 further mini-cells units are being installed in several European countries.
In addition, Vaillant started the production of a small-scale series early this year.
Parallel to the practical test, the two partners are already working on new models with emphasis on decreasing production costs and increasing the lifetime of the equipment.
The principle of the fuel cell has been known for over 175 years. So far, however, there has not been a market breakthrough.
The main reason was the invention of the electric generator. It knocked the more complex fuel cell out of the running.
Only in the 1960s was the technology put into practice by NASA in some Apollo moon missions. In the late 1990s, there were other projects in the automotive industry, which have so far not been able to prevail.
The reasons are that the fuel cell is too complex, too expensive, and too unreliable.
“In our project with Vaillant, we have made great strides to bring the technology close to the market,” says Jahn.
“Vaillant is already producing a small-scale series, which is sold in funded projects to customers. But, for the market breakthrough, the costs still have to be decreased significantly.”
The miniature power station for home use is based on a solid fuel cell (SOFC). SOFCs operate at a much higher temperature in comparison to competing approaches, such as the proton exchange membrane fuel cell (PEMFC), which is used in cars, for example.
While PEMFCs only reach 80C, SOFCs can reach up to 850 degrees. This allows the SOFCs to be built much more simply and cheaply, according to Jahn.
The electrolyte of an SOFC only transfers oxygen ions, not electrons. Otherwise, there would be a short circuit.
“Ceramic is particularly well suited as a material for the electrolyte. It has the desired conductivity and can also endure high temperatures,” says Jahn.
As a result, even without the use of precious metals, all reactions are said to proceed smoothly, which is necessary for the direct conversion of chemical energy into electrical energy.
If the fuel cell heater is connected to the gas network, a reformer initially converts the natural gas into a hydrogen-rich gas. This then reacts in the stack with the oxygen of the air in a noiseless “cold combustion”, producing power and heat.
