Sulfur degradation of SOFC fuel cell anodes has been solved by researchers at Tufts University led by Maria Flytzani-Stephanopoulos who has developed "sorbent" materials that reversibly adsorb hydrogen sulphide (H2S) from the flow of gas that passes over a fuel cell’s anode. These cerium and lanthanum oxide sorbent surfaces can work at temperatures up to 800 °C. The work, published in the June 9 issue of Science (abstract), could be a significant step in making high-temperature fuel cells practical.
Removing sulfur from SOFC fuel cells has been a problem because they operate at temperatures that are too high for sorbents used in PEM fuel cells. Stephanopoulos's technology frees SOFC cells from having to work with natural gas or other sulfur-free fuels.
Research is being funded by the Army Research Laboratory, which wants to use SOFCs as backup power for tanks and trucks. Since these vehicles run on fuel oil, such as JP8, that's rich in sulfur, they need effective sulfur removal.
Instead of filtering gas through a thick sorbent bed, they pass it over the surface of a thin sorbent layer. Stephanopoulos calls the new design a "simple" solution to the sulfur problem. The system could be added to a SOFC using two small reactors -- one for fresh sorbents, the other for spent ones. Sulfur-free gases generated by the fuel cell would sweep the spent sorbents clean, allowing the same sorbents to be used over and over. "You don't need valves or pumps," she says, because all gases would diffuse naturally through the system. She adds that her sorbents could also outperform those used for in low-temperature fuel cells.
The adsorption and desorption processes are very fast, and removal of H2S to sub–parts per million levels is achieved at very short (millisecond) contact times. Any type of sulfur-free gas, including water vapor, could be used to regenerate the sorbent surface.
Stephanopoulos said her materials are ready to be used widely. They are small and cheap enough to be incorporated into SOFC systems, and will solve ‘the acute problem of sulfur poisoning,’ she said. Extensions to applications in proton exchange membrane fuel cells are obvious, she added, ‘our sorbent would also work at low temperatures.’
This is but one of the problems preventing the SOFC from being in wider use, including long startup times and material deterioration at high temperatures. The SOFC, in my opinion has more potential than the PEM in that it can be used for distributed energy/CHP applications in homes and businesses and combined cycle MW scale power production for electric utilities. Siemans had a 100 kW SOFC operating on natural gas in the Netherlands for over 20,000 hours, where it typically fed 109 kW into the local grid and 64 kW of hot water into the local district heating system and operated consistently at an electrical efficiency of 46%.
Resources:
More Powerful Fuel Cells Get Closer To Market, Susan Nasr, Technology Review, June 13, 2006
Sulfur removal fuels fuel cell future, Chemistry World, June 9, 2006
Great news! This will allow biogas from landfills and farm waste digestors to be used at 75% efficiency, in conjunction with a microturbine,instead of 20% in conventional internal combustion generation. Providing distributed backup power for wind and solar, a big step in local power generation.
It also gives electric vehicles a great backup power source that runs on multiple fuels, to provide extended range with 75% efficiency. With a battery powered vehicle warmup time is not a problem.
http://amazngdrx.blogharbor.com/blog/_archives/2006/2/19/1772543.html
Posted by: amazingdrx | June 16, 2006 at 06:30 AM
Actually the army could retrofit their hybrid hummer with one of these fuel cell/microturbines to replace the conventional diesel generator they now use.
Along with even a moderate nano tech lithium ion battery capacity.
http://www.evworld.com/archives/conferences/evs14/humvee.html
Posted by: amazingdrx | June 16, 2006 at 06:37 AM
If you have looked into solar energy as a method for heating your home, panels are usually the first things that come up.
There are, however, other unique methods.
The Solar Heating Aspect You Have Never Heard of Before
The power of the sun is immense. The energy in one day of sunlight is more than the world needs. The problem, of course,
is how does one harness this power. Solar panels represent the obvious solution, but they have their downside. First,
they can be expensive depending upon your energy needs. Second, they do not exactly blend in with the rest of your home.
Passive solar heating represents a panel free method of harnessing the inherent energy found in the sun for heating
purposes. If you come out from a store and open the door of your car in the summer, you understand the concept of passive
solar heating. A wide variety of material absorbs sunlight and radiates the energy back into the air in the form of heat.
Passive solar heating for a home works the same way as the process which overheats your car in the parking lot.
Posted by: heating | February 28, 2007 at 08:04 PM