Wednesday, July 23, 2003
The Hydrogen Conundrum
The hydrogen economy is just waiting to happen, if one were to believe a lot of what one reads in the media. If only the damned automobile industry could be convinced to shift to hydrogen-as-fuel. There has always been a problem with this line of thinking, a hydrogen conundrum, if you will. Richard Muller addresses the conundrum in the current issue of Technology Review.
The key fact is this: Hydrogen is not a source of energy. It is only a way of storing and transporting it. Although hydrogen is the most abundant element in the Universe (and in the more immediate neighborhood, it makes up 90 percent of the atoms in the Sun and Jupiter), there is virtually no hydrogen gas on Earth. Our gravity is so weak that essentially all our primordial hydrogen except that which bound itself into heavier compounds escaped into space billions of years ago. So hydrogen fuel must be manufactured by extracting it from water and methane. You get out from hydrogen fuel only the energy you put into extraction, or from burning carbon in the process.
He adds -- Hydrogen is far from an ideal automobile fuel. Even in its densest form (liquid), hydrogen has only one-third as much energy per liter as gasoline. If stored as compressed gas at 300 atmospheres (a more practical option), it delivers less than one-fifth the energy per volume as gasoline. Such low energy density means that fuel storage would take up lots of room in a hydrogen-powered car or, alternatively, a modest-sized fuel tank would severely restrict the vehicle's range between fill-ups.
Is carbon sequestration the answer? Muller doesn't think so.
Serious research programs are underway to find a way to sequester carbon dioxide, whether it comes from hydrogen production or any other process that burns fossil fuels. One cheap solution could be to bury it in depleted gas and oil wells. My pessimistic bet, though, is that sequestering will be expensive. Politicians will choose to dump carbon dioxide into the atmosphere, and pay the hidden price of pollution, rather than ask the public to pay an up-front price at the pump.
The key fact is this: Hydrogen is not a source of energy. It is only a way of storing and transporting it. Although hydrogen is the most abundant element in the Universe (and in the more immediate neighborhood, it makes up 90 percent of the atoms in the Sun and Jupiter), there is virtually no hydrogen gas on Earth. Our gravity is so weak that essentially all our primordial hydrogen except that which bound itself into heavier compounds escaped into space billions of years ago. So hydrogen fuel must be manufactured by extracting it from water and methane. You get out from hydrogen fuel only the energy you put into extraction, or from burning carbon in the process.
He adds -- Hydrogen is far from an ideal automobile fuel. Even in its densest form (liquid), hydrogen has only one-third as much energy per liter as gasoline. If stored as compressed gas at 300 atmospheres (a more practical option), it delivers less than one-fifth the energy per volume as gasoline. Such low energy density means that fuel storage would take up lots of room in a hydrogen-powered car or, alternatively, a modest-sized fuel tank would severely restrict the vehicle's range between fill-ups.
Is carbon sequestration the answer? Muller doesn't think so.
Serious research programs are underway to find a way to sequester carbon dioxide, whether it comes from hydrogen production or any other process that burns fossil fuels. One cheap solution could be to bury it in depleted gas and oil wells. My pessimistic bet, though, is that sequestering will be expensive. Politicians will choose to dump carbon dioxide into the atmosphere, and pay the hidden price of pollution, rather than ask the public to pay an up-front price at the pump.
