As the world shifts to alternative forms of energy, ways to make homes less dependent on the grid continue to gather steam. Fuel cells, which are more efficient and have lower emissions than internal combustion engines seem like a logical candidate for taking up the slack, so the Fraunhofer Institute for Ceramic Technologies and Systems (IKTS) in Dresden is partnering with the heater manufacturer Vaillant to develop a domestic fuel cell system that uses natural gas to produce both heating and electricity.
Fuel cells have been around since 1838, and have long seemed like the power source of tomorrow, but it wasn’t until the 1960s that the first commercial fuel cells appeared, when they were used to power spacecraft. Though they’ve seen some applications in the automotive industry in the 1990s and the Ene-Farm home fuel cell became the world's first commercialized fuel cell system targeted at household heating and electricity generation with its release in Japan in 2009, fuel cells have struggled to find widespread adoption.
Part of the reason is their complexity and another is that they tend to be very expensive due, in part, to the need for precious metals like platinum for catalysts. Because such catalysts are easily poisoned by impurities, fuel cells also have a reputation for poor reliability. The Fraunhofer approach was to come up with a fuel cell for the home that’s simple, and can be installed and maintained like a common household gas heater that runs on natural gas.
Like the Bloom Box and SOFC system developed at the Technical Research Centre of Finland (VTT), the Fraunhofer system is based on solid oxide fuel cell (SOFC) technology, which uses a ceramic electrolyte to produce electricity as oxygen combines with hydrogen. SOFC's work at a higher temperature than other fuel cell designs, such as those used in cars. Where proton exchange membrane fuel cells (PEMFCs) car fuel cells can only reach 80⁰ C (176⁰ F), SOFCs can reach up to 850⁰ C (1,562⁰ F). In other applications, such heat is a problem, but for home applications it can be turned to the homeowner’s advantage for keeping the home warm or heating water.
Since ceramics can withstand high temperatures, its suitable for a SOFC, and this higher temperature makes it simpler to design and cheaper to operate. It also avoids using platinum or other precious metals as a catalyst, which brings down the cost.
Like most fuel cells systems, the individual CD-like Fraunhofer cells are very low power, producing less than a volt, so they need to be organized into stacks. In practice, the fuel cell is hooked up to the domestic gas supply. As the gas enters, a reformer breaks up the gas into a hydrogen-rich mixture, which reacts with the stack in what is called “cold combustion” to produce heat and electricity. Meanwhile, there’s an afterburner to increase efficiency from the exhaust gases.
According to Fraunhofer, the current design is as compact as a gas heater, and can be installed in the same places as a heater. But instead of producing just heat, it also puts out one kilowatt of electricity as well, which is about enough for a family of four. The technology is currently undergoing trials involving 150 units in homes in Europe as part of the Callux practice test to see how well they function in a domestic environment.
Fraunhofer and Valiant are now working on decreasing the cost of the fuel cells and increasing their service life.
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