BIZARRE technologies for generating energy that were previously ruled out as pipe dreams will have to be developed if nations are serious about tackling climate change.
That’s the view of 18 influential energy analysts in the US, who argue their case this week in the journal Science (vol 298, p 981). They say none of the power-generation technologies being developed now will be able to control greenhouse gas emissions and meet the world’s energy needs – which may rocket by 200 per cent by 2050.
They urge governments to undertake broad energy research programmes, exploring some of the stranger technologies dreamed up in recent years, like collecting solar power in orbit and beaming it back to Earth, and using space-based lenses called “parasols” to deflect solar energy away from our atmosphere.
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The 18 scientists hope to open up the bitterly polarised debate on global warming: while advocates of the Kyoto Protocol say climate stabilisation is vital and within reach of today’s technology, critics argue that it is unnecessary and exorbitantly expensive.
“We stake out a third position,” says atmospheric scientist Ken Caldeira of the US government’s Lawrence Livermore National Laboratory in California. “Climate stabilisation is important, but we can’t really do it with current technology, even if we wanted to.”
The world’s energy needs are rising far faster that we can bring emission-free generation such as nuclear and wind power on stream. Global power consumption for electricity, transport, heat and industry is now about 12 trillion watts, 85 per cent of which comes from fossil fuels. To stabilise the climate, the energy analysts estimate that the world will have to bump up emission-free power generation from today’s 2 trillion watts to as much as 30 trillion watts by 2050.
But nuclear power can’t fill the gap. Uranium supplies are limited and known reserves could supply 10 trillion watts for only 6 to 30 years. “That’s hardly a basis for energy policy,” the scientists write.
Breeder reactors create more fissile material than they consume, so you’d get more nuclear fuel, but developers have abandoned them because of low efficiency, safety issues, and the possibility of fuel being turned into weapons. And fusion reactors are still a very distant prospect, despite decades of research.
Vast satellites that harvest solar power are an attractive emission-free idea, says Martin Hoffert of New York University, one of the team. Sunlight is eight to ten times more intense in space, so arrays could generate more power than on the ground. Microwaves or laser beams could get power to any point on Earth, including areas without power grids. Energy might also be beamed down from massive solar arrays carpeting the Moon, via relay satellites.
The prospects for ground-based biomass, solar cells and wind power are limited, the team believes. You’d need to cover more than 10 per cent of the Earth’s land surface with biomass crops to generate 10 trillion watts, Caldeira says. Wind and solar power are only part-time energy sources, so generators would have to be linked to a computer-controlled global power network based on superconducting cables, which also eat energy to keep cool.
Another outlandish option might be to turn down the global thermostat by reducing solar heating. To do this, you’d place a 2000-kilometre wide Fresnel lens in orbit 1.5 million kilometres from Earth. Refraction would deflect about 2 per cent of Earth’s sunlight, enough to offset warming caused by further CO2 emissions. Caldeira has calculated that the process should work.
But Alan Nogee urges caution. As head of the Union of Concerned Scientists’ clean energy programme, he says today’s energy-efficient and renewable energy technologies can meet climate change goals. “It’s critical that we do not defer immediate action in the hope that more R&D can produce some exotic technologies that may not be needed – and which may have other harmful impacts.”
