One of the staunchest advocates for the adoption of alternative energy sources to stave off ill effects of global climate change is a voluble professor of physics at New York University named Martin Hoffert. Wheeling electricity around the world through high-temperature superconducting cables, building solar-power systems in space, mining asteroids and distant planets -- the sky's the limit (along with human imagination) in considering alternatives to our current greenhouse-gas-emitting energy system, Hoffert maintains. Here, in a candid interview with What's Up With the Weather? producer Jon Palfreman, Hoffert lays out his visionary prescription for a future without fossil fuels.

Even if there were no greenhouse effect, all of the fossil fuels will be depleted within a few hundred years. If humankind is going to have a future on this planet, at least a high-technology future, with a significant population of several billions of humans continuing to inhabit the Earth, it is absolutely inevitable that we'll have to find another energy source.

And the greenhouse effect has made finding such a source all the more urgent?

If not for the greenhouse effect, we may have been able to postpone that decision to the 22nd century, because there are massive coal reserves available, and coal can be made into synthetic fuels. We could have developed the world economy based on fossil fuels in countries that are presently developing, such as India and China. The problem then would not be energy but rather local air pollution and environmental problems. But with the greenhouse effect, we have to make the transition much earlier, perhaps in the early 21st century. That means that we have to look very seriously at the alternatives.

Such as?

The first alternative, of course, is renewables, which include solar energy in its various forms, biomass energy, wind power. Sometimes geothermal energy is included in that as well. But all of these sources of solar energy tend to be very episodic -- they're not always there -- and the power density is low, that is, the number of watts per square meter is pretty low. The fact that it's episodic is important. We can convert solar energy in photovoltaic cells with an efficiency of maybe 15 or 20 percent, but most people want to turn on the lights at night, and the sun isn't shining at night. So you need some kind of a system that will distribute the available renewable energy to the place where it's needed.

A global electric transmission grid that relies on superconducting cables may one day replace standard transmission lines.

Right now we use electrical transmission lines, which are reasonably efficient. But even transmitting at the highest voltages we can -- and the higher the voltage, the more efficiently we can send the energy out -- we cannot cost-effectively send energy more than a few thousands of kilometers. That means that we don't have electrical distribution systems, for example, that will allow us to collect solar energy on the part of the Earth where the sun is shining, where it's daytime, and sell it to the other part of the Earth where it's nighttime. If we had such a technology, that could make a very big difference in the viability of renewable energy.

Any in the works?

Well, Buckminster Fuller, one of the true American geniuses, proposed back in the 1970's, or earlier even, a global electrical transmission grid that could do this. It would be based on superconducting wires -- that is, wires that would have no electrical resistance and so there would be no cost penalty in sending electricity for thousands of kilometers around the world. That was before physicists had discovered high-temperature superconductors. Within the underlying physics exists the potential that the entire world could be interconnected.

You could imagine a kind of global deregulation, in which electricity would be sold at a common price worldwide, and where anyone who had renewable energy could sell the electricity to the grid. You could connect the buyers and the sellers, supply and demand, using presently understood computer technology to balance the load, and you could imagine renewables playing a very, very significant role with that particular technology.

To make renewables cost-effective, though, you need to use a lot of land.

	To rely entirely on energy derived from biomass, we would need to dedicate up to 10 percent of the world's land surface to growing wheat for fuel.

Yes, overcoming the low-density problem brings up inevitable land-use issues. Let me give you an example. Say that by 2050 you wanted to supply ten terawatts of power -- or ten trillion watts, which equals the current total energy consumption of all humankind -- and you wanted to do it with biomass energy. You would need an area equal approximately to 10 percent of the Earth's land surface area. That's equal to all the land that's used in human agriculture right now. If you needed 30 terawatts generated by biomass, you would need three times as much land.

So you can imagine a world where the only things on the planet would be human beings and wheat, and we would eat the wheat and we would use the wheat to make alcohol for our vehicles. But no other biological diversity would exist, because we would have appropriated all of the land surfaces to do that. That's the kind of issue that you have to deal with when you seriously talk about stabilizing carbon dioxide in the atmosphere.

You mentioned vehicles. What's down the pike, so to speak, for personal transportation?

When people talk about the transition from gasoline-powered automobiles to electrically powered, they usually end up with fuel cells. They're like batteries, except that the chemicals that react in them are kept outside rather than inside the fuel cell. Ultimately, what you need for automobiles is an energy carrier that has a high-energy density. Hydrogen might prove to be a very good energy carrier, or perhaps even flywheels, if they could be made strong enough and rotate fast enough. Neither of those would produce significant effluence.

The question is: Where will the energy come from to make the hydrogen or to turn the flywheels? I think we're pretty close to the technology, for example, for hydrogen-powered automobiles. In fact, there are hydrogen-powered automobiles, and Mercedes has made buses powered by hydrogen in fuel cells.

Will the electric car someday give way to hydrogen-powered vehicles that depend on platinum mined from asteroids?

There are some problems even there, though, that might require us to look for resources beyond this planet. Take electrolyzers and fuel cells, for instance. Electrolyzers can make hydrogen out of water with a suitable source of energy, and fuel cells can combine hydrogen and oxygen into water and provide energy. But the designs that we have right now that are practical require catalysts made out of platinum.

We did a calculation of how much platinum it would take to produce hydrogen at the rate of 10 terawatts, assuming we had a hydrogen economy. It's more platinum than exists on the Earth right now. John Lewis of the University of Arizona has estimated that it might be cost-effective to mine platinum in asteroids and export it to the Earth. It would be marginally cost-effective if we had a cheap enough space transportation system, which would be the next generation beyond what's presently being considered.

But in a hydrogen economy, you would have to have a way of making hydrogen that doesn't itself produce carbon dioxide.

Well, you don't have to. In fact, the people who want to sequester waste carbon in depleted gas reservoirs and in the deep ocean want to make hydrogen and put the extra carbon in the Earth or sea. If you want a long-term solution, you need a really high-energy density material. If your time horizon is long enough, we might use anti-matter. Anti-matter has a much higher energy concentration than even hydrogen does.

The potential exists in the underlying physics for what would seem to be near miracles. This is something Arthur C. Clarke once said, that any sufficiently advanced technology is indistinguishable from magic. I think that's certainly true. If you were to transplant someone from 100 years ago into the year 2000, the things we do now would certainly seem magical to them. We know they're not magical. What we understand of the physical universe limits us to what we can do, but within what's possible, we're only limited by the creativity of our scientific imagination and by our will to try to find the solution.

What about nuclear power?

	Despite its bad reputation in the public's eye, nuclear fission should not be dismissed out of hand, Hoffert feels.

Well, that, as you know, has been a very contentious issue in the United States and in other parts of the world. Since the Three Mile Island and Chernobyl nuclear accidents, no nuclear power plants have been built, and there are many, many sets of issues having to do with the disposal of radioactive materials and the proliferation of weapons-grade material and so forth.

But leaving those safety issues aside for the moment, how does nuclear compare with renewables?

Well, in contrast to renewable energy, nuclear power is a very high-density source of energy. Biomass energy per unit area can produce a few watts per square meter. By contrast, the boiler of a nuclear power plant, where the nuclear energy is being converted into steam, produces tens or hundreds of thousands of watts per square meter.

Light-water reactors like those used in the United States (above) rely on U-235, a very finite resource, while breeder reactors can turn the more common U-238 into a burnable nuclear fuel.

But like renewables, it's a limited source of energy, too.

Yes, there is a limited amount of uranium around the world, at least that we've been able to find. There's actually a lot of uranium in the Earth's crust, but you have to find uranium ore that's very concentrated. (And there's only a very minute fraction of fissionable uranium in natural uranium -- only about 0.3 percent.) If we look at the estimates of the available uranium ore around the world, at cost effective prices, and we ask the question, if we were to burn it in light-water reactors (conventional nuclear reactors used in the United States and Western Europe), how long would the reserves of uranium last if we were to extract energy at the rate of ten terawatts? Well, it turns out that you only have about ten years of U-235 power from all of the cost-effective uranium reserves. (U-235 is the isotope of uranium that undergoes nuclear fission.)

What about breeder reactors?

Well, breeder reactors could extend the amount of natural uranium by a factor of 100. That is, if you took the rest of the uranium, the isotope U-238, and irradiated it with neutrons in a breeder reactor, you could convert it to a burnable nuclear fuel. But it takes a long time to do this. It takes about 20 years to create the same amount of energy in the U-238. The other bitter pill about this is that, with breeders, you're making weapons-grade plutonium, which presents a whole other problem: having enormous inventories of plutonium around the world.

What about nuclear fusion?

Well, scientists have long believed that if we can make a hydrogen bomb, which we did in the 1950s, we should be able to extract energy from fusion. After all, about ten years after the first fission bomb, we had the first nuclear fission reactor. But it's now been 40 years since the first hydrogen bomb, and we still don't have a fusion reactor.

	We may eventually develop nuclear-fusion reactors that rely on helium-3 gathered from the atmospheres of other planets.

Fusion is much harder because to make it work, we have to create extremely high temperatures -- 100 million degrees Kelvin, if you can imagine that -- and we also have to hold together the atoms of hydrogen or hydrogen isotopes (such as deuterium or tritium) long enough so that they can react with one another.

I think we'll eventually be successful with fusion, but we need to have different systems and perhaps different fuels. One of the fuels now being considered instead of tritium is a helium isotope called helium-3. It would have a lot of advantages in a fusion power plant, because it wouldn't make the walls of the reactor radioactive. Unfortunately, there isn't much helium-3 on the Earth, though it turns out that the Apollo astronauts found helium-3 on the moon in concentrations that might be economically recoverable. If fusion reactors that rely on helium-3 could be made to work, then even at the very high costs of launching materials into space and recovering them, it may be marginally cost-effective to get helium-3 from the moon.

In the long run, there are advocates of space exploration who believe in helium-3 and who think that the best place to get it would be in the atmospheres of the outer solar system planets. The atmospheres of Jupiter, Saturn, Uranus, and Neptune all have significant amounts of helium-3. Some have even said that the outer solar system could become the Persian Gulf of the second half of the 21st century, should we go down that particular path.

Another path you've argued we should be investigating is a space-based solar power system.

There's a great potential for collecting solar power in space and beaming it to the Earth. That may sound like a really crazy idea. Why should you collect solar energy in orbit and then send the solar energy to the Earth? Why not put photovoltaic cells on the Earth's surface? The first answer is that between eight and ten times as much solar energy per unit area exists in space as on Earth. This is because our planet is rotating, it's a sphere, and because clouds cover its surface. And it's more highly concentrated.

Hoffert lists several reasons why a solar-power system based in orbit is a bright idea.

The second reason is that the technology exists for collecting this energy either with photovoltaic cells or otherwise, and by creating microwave beams to beam that energy to the places where it's most needed -- for example, tropical developing countries. As much as 40 percent of such regions may have no electricity at all.

What would such an orbital solar-power outfit entail?

There are many different designs that one can look at. One concept I've been associated with (and I don't want to necessarily promote this over others) is to gradually evolve a kind of orbital power-and-light business from communications satellites. Plans are afoot now to put thousands of satellites in low Earth orbit for purposes of cellular phone telecommunications, and also to sell global Internet links through satellites.

In my opinion, such a business could eventually evolve into one in which you could sell either bits of information or kilowatt-hours, using essentially compatible components: the same kinds of antennas in orbit and similar kinds of antennas on the ground. Of course, it has to be studied, but I think that the levels of microwave power, in terms of the objective health effects, will be below those that occupational health and safety regulations say are dangerous to humans.

Until now, it's been very interesting and exciting for us to explore the solar system and to find out how the universe works with the Hubble telescope, but for the enormous investments we've put into space, we haven't gotten very much return as a society. There are energy resources available in space, and it's possible to exploit them. So that could become a frontier that could also play a very big role in human energy consumption on the Earth.

	As at the turn of the 20th century, Hoffert feels that we're currently conservative in our thinking about technologies that might replace those that rely on fossil fuels.

And a 50- to 100-year time scale is not too long for that to happen in, when you consider what happened in the last 100 years. I mean, try to imagine what the world was like in 1900 compared to today, and the technologies that were being envisioned by even scientists and engineers back then, and what actually happened. For the most part, people were projecting very similar technologies to those then existing. Unfortunately, that's what we're doing now in trying to mitigate the fossil-fuel greenhouse effect.

What did they fail to predict?

The specific example I'm thinking about was at the Columbian Exposition in Chicago in 1893, which was sort of a showcase of technology at the end of the last century and the fin de siecle vision of what the future was going to be like. They missed the movies. They missed radar and lasers. They missed airplanes and automobiles and space travel with nuclear power. The computer was missed even by science fiction writers in the 1950's.

Who will enable the next wave of futuristic technologies?

Of course, that's an issue. In the competitive industrial environment that exists now, industry will not support anything that isn't going to bring a profit in three or at most five years. It would put the companies at competitive disadvantages to do that. Even industrial laboratories that used to support that kind of thing, such as Bell Labs (now Lucent Technologies), are focused overwhelmingly on the bottom line in a relatively short time frame of profitability.

Nuclear power is just one of dozens of 20th-century technologies that resulted from intense research and development by government.

So where did all of the technologies that drive our economy today come from? Well, commercial jet airplanes were spinoffs of military jet airplanes. Nuclear power was, of course, developed by governmental research. Communications satellites are a spinoff of space and satellite technology that NASA developed. Radar is an outgrowth of World War II technology, designed to detect incoming aircraft for the Battle of Britain and so forth. The Defense Advanced Research Projects Agency, an arm of the military, developed lasers. The military even developed the holy Internet, which is touted as the driving force of the national economy, as a way of transmitting packet information over phone lines in the event of a nuclear war. Cellular phones, compact discs -- all these things were developed by government research and development over many, many years at the cost of hundreds of billions of dollars.

The major problem we have regarding technological innovation right now is: How do we retain the momentum of invention and discovery in technology without the Cold War or without some sort of trans-rational fear that motivates the spending on research and development?

	Marty Hoffert is bullish on high technology as a potential solution to problems exacerbated by global warming.

What do you advocate doing?

Well, it's vitally important to confront the real issue, which in my view is the urgent need for a transition to a non-fossil fuel source of energy for our civilization. If we don't do it, we'll be faced with the alternative of possibly transforming our planet dramatically, changing the climate to one that we haven't seen for perhaps 100 million years. To make the transition, it will be necessary to recognize the magnitude of the problem and to develop a policy that addresses it.

What I'm proposing is a policy in which developed nations initiate programs of research and development for dramatically and drastically transformative systems of energy production on the Earth. Not all of these are going to work. But the ones that are successful -- and there is a possibility that several of them might be successful in some combination -- will totally transform our civilization and bring us into changes that are as dramatic as the changes that took place between the end of the 19th and the end of the 20th centuries.

Clearly, you're a technological optimist.

That should be pretty obvious from what I've said! I understand that there are those who are not disposed to solving the problems of technology by applying more technology. There's something to be said for those points of view. But at this point in our history, it is not our destiny to retreat from technology. We couldn't feed the population of the planet right now without the technology that's used in agriculture, without an enormous subsidy to agriculture in terms of fertilizer and so forth. At this point in our evolution, we are a tool-building and technological species. And it is in our interest to continually try to adapt to the situations that we're in with technologies that are appropriate.