Hydrogen fusion (updated)

By Greg Richards

James Lewis is quite correct in describing hydrogen in context as merely a method of energy conversion and transport and not a source of energy.

However, there is a context where hydrogen is a source of energy and that is hydrogen fusion, the process that powers both the stars and the hydrogen bomb. In hydrogen fusion, hydrogen atoms are brought together so forcefully that some of them fuse into helium with the loss of a small amount of matter (approximately 0.64%) which is converted directly into energy by E=MC².

The Lawrence Livermore National Laboratory (LLNL) is engaged in a project to attempt controlled fusion. It is in the process of building the world's largest laser which would provide the conditions for the ignition of a very small amount of hydrogen fuel (so-called heavy hydrogen, or deuterium). This project is called the National Ignition Facility and can be seen here.

LLNL has been working on controlled fusion for over twenty years. Success has proved elusive, as it has with a different technique developed initially in Russia, called a Tokamak reactor, where deuterium is confined magnetically as a plasma. The Tokamak approach failed - so far - due to instabilities induced in the plasma by the compression.

According to the current schedule, LLNL expects ignition - i.e., a successful test that would generate more energy than it consumes - by 2010 or a bit earlier. If achieved, this would be a landmark event. It would point the way to a new, abundant, and relatively clean source of energy, although there would still be much engineering work to be done. Deuterium, the fuel for hydrogen fusion, occurs naturally in seawater, albeit as a small proportion to the whole (.02%). This is sufficient that the fusion energy content of 1 gallon of seawater is roughly equivalent to 300 gallons of gasoline!

There are many details that have to be solved that are beyond this brief piece. Not the least of them is that initial fusion reaction would also use tritium, which does not occur naturally. The deuterium-tritium reaction releases a flux of "extra" neutrons that would be absorbed by the containment vessel and gradually break it down. So there is no free lunch with controlled fusion, but it also does not generate the long-lived waste isotopes characteristic of nuclear fission plants.

So, let's hope that the NIF remains on schedule and that it achieves the landmark of controlled fusion ignition by 2010!

Update: Tom Bruner writes:

Regarding the burning or smashing of hydrogen, I join Greg Richards in wishing the Lawrence Livermore National Laboratory, and all fusion researchers, the very best of luck in their efforts to bring fusion to the masses. However, it seems that controlled fusion has been "within the next ten years" since I was in high school and Nixon was president. So if it's down to 3 years now, we should see it within the next 15 or 20. The first commercial plant would go online a decade or so after that if lead time is comparable to other power plants.

However, with regard to hydrogen as an energy transport mechanism, it probably becomes economically viable when hydrogen fission is used to liberate the hydrogen from the source molecule. The transmission loss described by James Lewis still applies, of course, but the sheer amount of power available from a fission plant provides a certain economy that may overcome the inefficiency of the transport process if employed on a commercial scale.

Vehicles present a special problem in any case: they must store an energy source of some kind. Barring a Mister Fusion device, an energy source must be transported to and stored by vehicles to keep them safe and relatvely small. Current battery technology limits range of of pure electric vehicles too much to be practical in most cases. This leaves us with hydrogen, or petroleum based fuel.

We are limited in our domestic crude oil production by environmental concerns, justified or not. We are limited in our fission power production capacity by safety concerns, justified or not. We are limited in our fusion power production because the technology has not yet arrived.

The good news is that some very talented people are working on the problem.