A major announcement (hat tip to theWatt.com) came out of the Lucrene Fuel Cell Forum two weeks ago. The president of the conference, Ulf Bossel, presumably with the support of the organizing commity, announced that the pre-eminant European fuel cell conference would no longer be providing a forum for the discussion of hydrogen fuel cells. This is due to the unsuitability of hydrogen as a fuel to power our economy.
Fuel cells are energy converters, not energy sources. They will be part of a sustainable energy solution only if they can compete with other conversion technologies. This includes system parameters, fuels and applications. Time has come for a critical assessment.A series of technical reports on the subject by Ulf Bossel and others is available here. I discussed this on this week's theWatt.com podcast. I would like to reiterate some of the arguments here.
The European Fuel Cell Forum is committed to the establishment of a safe energy future. Therefore, it will continue to promote fuel cells for sustainable fuels, but discontinue supporting the development of fuel cells for hypothetical fuel supplies. Time has come for decisions. Keeping all options open is not an adequate response to mounting energy problems.
Therefore, the schedule of the European SOFC Forum will be continued in 2008 with an extended conference every second year. Beginning 2007 (July 2 to 6) sustainable energy topics will be emphasized in odd years. Despite earlier announcements the European PEFC Forum series will not be continued.
Just to provide a bit of background there are basically two general categories of fuel cells: ones that operate at low temperature − typically below the boiling point of water − and ones that operate at a high temperature of at least several hundred degrees. The proton exchange membrane or PEM fuel cell is the low temperature fuel cell, along with the direct methanol fuel cell. There are many more high temperature fuel cells − examples would be the solid oxide or molten carbonate types. The PEM is unique in that it's the only type that can only burn pure hydrogen; all of the other types can directly burn hydrocarbons of one type or another.
The proponents of the proton exchange membrane fuel cell have promulgated this concept of the 'hydrogen economy' that I'm sure all my readers have seen references too. Basically the hydrogen economy is the idea that we can shift from using fossil fuels to hydrogen as a chemical fuel to power our economy. The transformation would begin with the transportation sector and eventually propagate to providing residential fuel cells that could provide combined heat and power.
There are three major shortcomings of the hydrogen economy concept:
The storage problem is partly technological and partly the laws of physics. The basic difficulty comes from the fact that hydrogen has an extremely low density: liquid hydrogen a density of only 80 k/m3. In order to get hydrogen from a lighter than air gas to some usable stored form it needs to be compressed, liquefied, or chemically bonded. All of these means need to consume a large fraction of the energy of the hydrogen to get it to that state. Hydrogen is not like gasoline. You cannot pull up to a station and pump your tank full in a couple of minutes. A lot of people don't realize that pumping up a high-pressure compressed hydrogen tank can easily take 30 - 60 minutes.
The last problem is that of production; it is the most fundamental problem and it’s the basis of the schism that's occurred at the Lucerne Fuel Cell Forum. Unlike fossil fuels hydrogen doesn't exist in nature on Earth − we can't poke a hole in the ground and pump out hydrogen formed from long-dead plants. Hydrogen isn't an energy source; it's an energy currency, like electricity. Elemental hydrogen has to be produced from other compounds such as water or hydrocarbons.
When it comes to producing hydrogen from fossil fuels the high temperature fuel cell guys rightly get out their signing voice and break into their best rendition of, "Anything you can do I can do better..." from Mary Poppins. The solid oxide fuel cell and other types can all burn natural gas, gasified coal and biomass at a higher efficiency than converting those feedstocks to hydrogen and using a PEM cell.
That leaves producing hydrogen from the electrolysis of water, which is the supposedly ‘green’ option. The reality is that the electrolysis to fuel cell path is a terribly inefficient method to convert solar, wind, and nuclear energy to useful work. Let us consider the production of hydrogen from wind power. First you have to rectify the alternating current to direct current to power the electrolyzer, which is about 90 % efficient. An electrolyzer is optimistically 75 % efficient so you lose another quarter of your energy there. Then you need to store the hydrogen, by say compressing it under high pressure. This would consume about 20 % of the energy content of the hydrogen, and distributing it perhaps another 10 %. Now we finally have the hydrogen at the fuel cell but then we have to remember that the fuel cell is maybe 50 % efficient. The product of the fuel cell is direct current electricity, so in the end we’ve gone through a whole bunch of steps in a big circle. When you multiply all these factors together you find that the well-to-wheel (or source-to-sink) efficiency is only about 25 %.
The obvious question that Ulf Bossel and people such as myself ask is why go to all that trouble? Why not just transmit and use the electricity directly? High-voltage direct current electricity transmission is just as efficient as pipelining hydrogen. If we allow for 90 % efficiency for rectifying and 90 % for transmission we end up with 3.3 times more energy for the electricity economy than the hydrogen economy. If you want to include batteries the math doesn’t change much because the round-trip efficiency of batteries is really very high – 90 % for lithium-ion batteries. As Bossel states, hydrogen cannot compete with its own fuel source − in this case, electrons. This poor efficiency of the hydrogen economy that I’ve talked about is not something that has a solution through improved technology. The laws of thermodynamics maintain the limiting factor here. All the extra steps in the hydrogen case produce entropy, and there’s no way to get past certain theoretical limits to the efficiency of each stage.
The inefficiency of hydrogen isn’t something that we can afford environmentally. Would anyone consider it better to have three wind turbines rather than one, or three nuclear power plants rather than one? If you try to figure out how many power plants we would need to implement the hydrogen economy it becomes readily apparent what a fantasyland it is. The USA uses approximately 20 million barrels of oil per day. If we were to replace every gallon of gasoline with a kilogram of hydrogen we would require 1.4 TW of continuous power. However, there’s only 0.9 TW currently installed, of which about 2/3rds is used on average, so the idea of trying to use nighttime power to produce hydrogen won’t work. The existing infrastructure is incapable of powering a hydrogen economy – we’re talking about 1500 large nuclear power plants. So not only would we have to change our entire distribution network but we would also have to massively ramp up electricity production. The expense of the whole idea is terrifying.
This is sharply contrasted with trying to develop plug-in vehicles, electrified rail and such. Because the electricity path is so much more efficient we can actually dump almost all of our transportation energy needs on the existing electricity grid. If we throw in some efficiency improvements to the residential and commercial sectors then everything is peachy. The existing electrical grid that we have may not seem as sexy as hydrogen but it’s definitely the better option.
What's happened at Lucrene is that the rest of the fuel cell community have gotten tired of the empty promises of the hydrogen economy and are fighting back. PEM fuel cells have been receiving a disproportionate share of funding into all alternate energy technologies. What Ulf Bossel is saying is that is we have to refocus our efforts and monies onto technologies that we know will actually work rather than some idea put forth by a special interest group. Of course, the PEM researchers don’t want to hear this. Careers are at stake so I wouldn’t expect abandonment of the hydrogen economy concept quite yet.