The journal Science has devoted a special issue to puzzling out the Earth’s energy problem. Among the articles, foretelling the prospects of moving solar electricity from Africa to Europe, the downer that cellulosic ethanol has become, and the possibility of a nuclear renaissance, is a large chart that compares various energy sources in the way they consume other natural resources.
The surprising thing about the chart is that coal and oil don’t come out looking so bad. There’s a reason why these dense forms of energy fueled the Industrial RevolutionÂ (if only they didn’t spew so much CO2).
It’s not like we’re lacking in energy on Earth. The sun emits enough power (101,000 terawatts) to keep the world’s lights on 6,700 times over. That’s remarkable. Harnessing it, however, drinks up some 3.2 liters of water per kilowatt hour when it comes to solar thermal technologies (photovoltaic needs no water). Compare that to coal, which consumes 1.9 liters/kwh and oil, which takes about 1.6.
Since fresh water shortage is another crisis of the future, tying our energy needs to water needs seems like a bad idea. Land we seem to have more of, but does it make sense to power cities off renewable streams of energy that take more land than the cities themselves?
That’s the case with San Jose, according to the chart. If the California town was entirely powered off wind, the wind farm would have to be 53,000 hectares. San Jose itself is 46,000 hectares. Coal would need only 3,800 hectares to power San Jose, while natural gas would take 290. A shocking amount is needed for biomass, which would chew up some 270,000 hectares, some five times the size of San Jose.
So what’s the solution to our energy needs in a world of finite resources? Adrian Cho, who wrote the article, points out that experts believe there’s no single solution, but rather a myriad of technologies needed. Just consuming less energy helps a lot, too. Energy efficiency is the unsung hero of meeting the world’s energy demands.
Part of the takeaway for me is that there’s no such thing as “free energy.” It all has a cost – in carbon, in water, and in land use — that makes our decisions more like balancing a checkbook. If we go into debt with one cost, there will surely be pack back later.