Looking into a crystal ball it's hard to bet against the possibility that the coming decades will be the era of the great renewable energy revolution.
Do a swift 180 and look back at the two decades just gone and it's fair to say that one technological advance stood out above all others as defining the period. In case you're not sure what it is I'll give you a clue: you're using it right now.
The Internet may have taken over the world in little more than 20 years but the history of its development goes back much further. In 1963, a computer scientist called J.C.R Licklider wrote a memorandum discussing a concept for an "Intergalactic Computer Network." Seen with hindsight the concept is pretty much a blueprint for what the Internet became.
The same year as the memoranda came out Licklider was appointed to a leading role at the Defense Department's Advanced Research Projects Agency (ARPA) to create a shared computer network known as the ARPANET. The ARPANET was one of the core networks that eventually led to the creation of what we recognize today as the world wide web and it was funded by the U.S. military.
We shouldn't be surprised by this, of course. It's a well-known irony of history that war has frequently helped advance the cause of technology: radio, radar and nuclear energy are just three obvious examples.
Right now something similar could be going on with renewable energy.
At a naval base on the Indian Ocean atoll of Diego Garcia, scientists from the U.S. military are developing a system to create energy from hot and cold seawater. Called Otec, the system uses the hot and cold water to alternatively heat up and cool a refrigerant-like ammonia which boils at room temperature and which is used to power a turbine.
The research, however, is only a small part of the military's green tech agenda. The U.S. military, from its top brass to its frontline troops, have embraced renewables in a way that would have been unimaginable a decade ago.
The military has declared it will get half of its power from clean energy sources by 2020 and Ray Mabus, the Navy secretary, has set a date of 2016 for the launch of the "Great Green Fleet" — a carrier strike group that will use fuels that are all a blend of biofuels and conventional fuels. The Marines have already begun using solar power packs at forward bases in Afghanistan and last year the Navy spent $12 million for 450,000 gallons of biofuel, the largest purchase of biofuel ever in the U.S.
Inevitably many in the renewable energy sector are licking their lips at the prospect of such lucrative contracts and since the U.S. military is the biggest consumer of energy in the world there should be plenty to go round. More important in the long-term, green tech firms recognize that the widespread deployment of their technology by the military would likely drive down production costs and help establish the industry on a more sustainable footing.
It's a turn of events that has attracted some heavyweight support.
"We need even more reliance on the military," former president Bill Clinton told a meeting of cleantech entrepreneurs recently. "If the military wants to build 20 facilities that are carbon-neutral within a few years, why not help him build 50? If the public fleet alone of military vehicles could make electric vehicles economic, why not give them the support to do it?"
In spite of Clinton's powerful endorsement, not everyone is so sure. Many environmentalists have an ideological block when it comes to endorsing the take up of renewables by an organization whose main business is war. Even those who are more sympathetic to the idea are troubled by the rather sticky question of motives.
Both the military and President Obama, who is the main instigator behind this push for a green military, have been clear from the outset that the military's only real priority in the take-up of green tech is energy dependence: in other words, freeing themselves from the bind of what Gen. James Mattis, a Marine commander in the first Iraq war, once called the "tether of fuel."
The military's concern is not global warming, but the prospect of Saudi Arabia or a nuclear-armed Iran holding them to ransom over an ever-dwindling oil supply.
This troubles environmentalists, who fear that rather than being the savior of the green energy movement, the military is simply exploiting clean tech as a way to stay relevant at a time of economic downturn when the necessity for such a large and costly army is being called into question.
In a recent article in the New Statesman, environmental campaigner John Naish argued that applying green technology to warfare was a step which could in fact make the world ultimately a more dangerous place. "Nuclear weapons halted the game for war hawks, as they meant that any conflict between superpowers would wreck the planet," Naish wrote. "Green tech has revived the possibility of a mass war in which the environment isn't destroyed."
Or put another way. "The military is developing these technologies so that they can fight wars in a post-climate-change future," Alex Randall, of the Centre for Alternative Technology, said in the same New Statesman article. "We would rather that funds were concentrated on technologies and policies that prevent climate change, and which thus prevent conflicts from happening."
The strange scenario of a green military has made for some unlikely bedfellows in the arguments against it.
Concerned environmentalists have been joined by staunch Republicans, who say the efforts to go green will take money away from more vital security programs at a time when the military budget is already absorbing $487 billion in cuts. Republican senators like John McCain claim the new measures are part of Obama's global warming agenda.
Not that these kind of arguments are much of a worry for those backing the plans. In a recent radio interview, Juliette Kayyem, a foreign affairs columnist at the Boston Globe who has served in the Obama administration, said McCain was "technically absolutely right" in his assessment of the situation.
"What is happening here is an effort to have the Pentagon, like most of the world, try to wean itself off of oil," Kayyem told NPR. "Walmart is doing this. Target, the big supply chain, private sector companies are doing it. This is not a surprise. And so McCain thinks he's criticizing some green agenda of the Obama administration. But what's lost in his criticism is that this is actually being driven by the military."
* Paul Willis, EarthTechling