Harnessing the motion of water is one of the most ancient ways humans have generated power. Today, hydropower accounts for about 20 percent of the world’s electricity, a figure that has stayed the same since the 1990s.
But even when a dam isn’t involved, water is key to producing most of the world’s electricity. In gas, coal, nuclear and many other types of power plants, the fuel is actually used to turn water into steam, and generators convert the steam’s energy into electricity. In honor of this year’s World Water Week, here are some of the unexpected ways water plays a vital role in modern energy production, and some of the surprising uses for water in the possible power sources of the future:
There may not be a lot of energy in a falling raindrop—otherwise they’d surely hurt. But French scientists have figured out a way to harness what’s available. A team at the French Atomic Energy Commission built a device using a special plastic that converts the vibrational energy of a raindrop hitting it into electricity. Such an invention couldn’t produce a lot of power: a downpour generated up to 12 milliwatts, or enough to power a couple standard laser pointers. But the system would have an advantage over solar, as it would work in the dark and, of course, in a rainstorm.
With a device called a fuel cell, hydrogen can be turned into electricity. But even though the element is abundant, getting pure hydrogen alone has long been a challenge. Today, nearly all the world’s supply comes from fossil fuels, mostly natural gas. Researchers, however, have been working on ways to split hydrogen from water without using more energy than the fuel cell can produce. Some projects, for example, are exploring bacteria and solar-thermal techniques.
Seawater-derived Jet Fuel
In a more extreme twist on hydrogen power, the U.S. Navy announced earlier this year that they have developed a method for turning seawater into jet fuel. The process begins by using electricity to split water into hydrogen and oxygen. Then the hydrogen is combined with carbon dioxide that had been dissolved in the water to produce a hydrocarbon, aka jet fuel. But anyone looking to the oceans as a solution to all our energy problems will be disappointed. The process is energy-intensive and really only an option if you’ve got a nuclear-powered ship on hand and need jets in the air more than electricity on deck.
Build a really tall tower with an upper lip, then blow a fine mist of water over that lip. The mist absorbs heat from the air and evaporates. That results in cool, dense air flowing to the bottom of the structure, where it gets diverted through huge wind turbines that produce electricity. This method, which was patented back in 1975, works best in hot, arid places and requires a lot of water. It will finally get its first test in 2018, with a tower taller than the Empire State Building slated for construction in Arizona.
Geothermal energy relies on heat from inside Earth to produce power. But you can’t simply plug a toaster into the nearest magma pocket. In some places, such as Iceland and California, seismic activity breaks up the rocks, allowing water to circulate near geologic hotspots. Steam then naturally rises to the surface, where it can drive generators. In sites where hot rocks are deeper below the surface, cold water can be pumped down through wells to be heated, and the hot water can be extracted from other wells. Some buildings even use geothermal heat pumps, but they usually rely on air or an antifreeze, not water, to move energy.
Traditional biofuels—such as wood—don’t need additional application of water before being harvested. But many of the newer biofuel sources drink up even more water than nature provides. Crops such as corn and sugarcane are now grown specifically to create ethanol, and they require irrigation. As much as 8 percent of U.S. freshwater may go to such biofuel production by the year 2030, according to one estimate.
In hydraulic fracturing, water is pumped deep underground to create cracks that allow access to trapped oil or natural gas. Each well can require up to 7 million gallons of water to release all that fossil fuel. In some areas, such as California and Texas, diverting water for fracking is depleting already stressed supplies. Such tension may increase, according to a new report from the World Resources Institute, which notes that 40 percent of the countries that have areas suitable for fracking already have limited water resources.