First the bad news: With oil prices rising and energy demand from emerging economies ballooning, no single energy source will emerge to replace fossil fuels.
The good news is that that's OK. Even if nothing ever rules the world like oil did last century, different regions will adapt by tapping the technologies and energy sources that suit them best.
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"We'll really be looking at a tapestry...as opposed to the silver bullet notion that one source will break through and dominate," says Barry Rabe, a professor of environmental policy at the University of Michigan - Ann Arbor.
So just how will our grandchildren meet their energy needs? We'll continue to use oil and natural gas for decades, if not centuries, but as a shrinking portion of our energy pie. We'll also use commonly proposed alternatives like corn-based ethanol and nuclear generators.
But there are also big changes ahead, both in terms of what we use and how much we use technologies that already exist. Take wind generation. The industry is growing at about 30 per cent a year, says Edward Guinness, co-manager of the Guinness Atkinson Alternative Energy Fund. That's faster than other renewable energy sources like solar and hydro-power. The price of wind-generated energy is currently competitive with fossil fuels, Guinness says.
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Solar power is also poised to grow quickly. Today about 0.1 per cent of the world's energy comes from solar power, most of it using photovoltaic cells. Guinness thinks that could grow to 10 per cent over 20 to 35 years as manufacturing processes are improved.
The expansion of solar thermal technology will also grow the sector. Government subsidies, favorable regulatory programs and the popularity of solar with consumers are also likely to boost usage.
Newer ideas could also turn into future energy sources. Have you ever thought we might harness the power of bending floorboards, or turn algae into fuel? It could happen.
Moreover, the future of energy is not just a question of what, but of how.
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"I think the things that would really blow us away if we could jump forward 20 years would not be the giant fields of windmills, but the 1,000 changes in daily life that have taken place in order to save energy," says Alex Steffen, executive editor of Worldchanging.com, which covers sustainable technology.
Those changes will go far beyond switching to low-energy light bulbs. One trend Steffen forecasts is that power sources will move closer to home. "I think we're going to see a lot more local energy, especially in places that are gifted with lots of sunshine, or wind, or strong rivers," Steffen says. As houses and small communities produce their own energy, it will flow back and forth on "smart infrastructure"-- two-way power grids that deliver from as well as to the home.
Take hydro-power, for instance. "If we're going to see new hydro development in North America, it wont necessarily be massive like the Hoover Dam, but micro-hydro," Rabe says. Places still unconnected to large-scale energy grids, like sub-Saharan Africa, are especially poised to take advantage of local-level options.
The future just might be bright after all. By the time the world's oil reserves do dry up, it's technologically possible that we will have weaned ourselves off of fossil fuels.
