Our biggest sources of energy basically rely on fire—burning fossil fuels. To build a sustainable energy future, we have to start relying on the other three classical elements.
Strip our biggest sources of energy to their most elemental, and you are left with fire—the burning of fossil fuels. To build a sustainable energy future, we will have to start relying a lot more on the other three classical elements: water, wind, and earth. This year, discover teamed up with the American Society of Mechanical Engineers, the Institute of Electrical and Electronics Engineers (ieee, and the National Science Foundation to bring leading energy experts to Capitol Hill, where they briefed Washington insiders and charted the scientific, technological, and political challenges that lie ahead on the road to a new energy economy.
1 EARTH: Tap Into the Heat Beneath Your Feet
THE CHALLENG Geothermal energy has been around so long that it hardly deserves to be called “alternative”; people have been tapping hot water below the Earth’s surface to generate electricity for a century. But geothermal accounts for only about 16 terawatt-hours a year in the United States, less than half of 1 percent of total electricity consumption. As with wind energy, geothermal is simple in principle but hard to do successfully in practice. Too often, drilling results in wells that are hot but have no water or wells that are simply not hot enough. A symptom of the industry’s woes is that federal funding for geothermal energy has fallen from about $450 million in 1979 (in 2011 dollars) to below $50 million this year.
THE NEW ENERGY ECONOMY Geophysicist David Blackwell of Southern Methodist University says that lack of attention is a mistake. He estimates that there are 100 to 500 gigawatts of potential geothermal energy locked beneath the United States. What is needed to successfully exploit all that energy, according to Nevada geologist James Faulds, is investment in more detailed geologic mapping, three-dimensional modeling of underground water flows, and
testing of water chemistry that can indicate the temperature of subsurface waters. More surveys of ancient hot springs, which can point to the locations of still-active geothermal systems, would help too.
Such support for geothermal energy is suddenly looking more likely due to an unlikely ally: the natural gas industry, which is in the midst of a giddy boom driven by the widespread adoption of the controversial drilling technique known as fracking. “We’re discovering that many of the gas wells that have already been drilled produce significant amounts of hot water,” says Karl Gawell, executive director of the Geothermal Energy Association. Many of those fracked wells could be reengineered to have a second life as sources of geothermal energy.
Wastewater Treatment of the Future
Today a typical plant consumes 0.7 kilowatt-hours of energy to clean a cubic meter of wastewater. But that same cubic meter contains about 2 kilowatt-hours of potential chemical energy. Next generation plants will not only be more efficient but also will extract energy from the organic material and nitrogen in sewage.
2 WATER: Turn Wastewater Into Energy
THE CHALLENGE Every day you are literally flushing energy down the toilet. “You can’t talk about energy as a resource and water as a resource independently,” says Tom Peterson, an engineer at the National Science Foundation. In California alone, 19 percent of all the electricity and 30 percent of the natural gas is used to move, treat, and heat water.
THE NEW ENERGY ECONOMY Since transporting water eats up so much electricity, developing ways to recycle the water that goes down the drain could yield big energy savings. The nation’s model for this kind of innovation is Las Vegas. “We reuse virtually 100 percent of our wastewater,” says Patricia Mulroy, general manager for Las Vegas Valley Water District. Over the past 20 years, the district has modernized its water reclamation system, which now returns 70 billion gallons of treated wastewater annually to Lake Mead, the source of 90 percent of Las Vegas’s water. With the nation’s water infrastructure nearing the end of its design life, Stanford engineer Richard Luthy says now is the time to build a more energy-efficient system. “We need to avoid pumping water over long distances and focus on systems that produce water for reuse where it’s generated,” he says.
And the wasted energy in each flush lies not just in the water—there is also energy in the waste itself. One gallon of typical domestic wastewater contains enough organic compounds and nitrogen to power a 100-watt lightbulb for five minutes. The exciting implication is that next-generation wastewater treatment plants could use new technologies, including microbe-powered fuel cells, to capture enough methane, hydrogen, and other fuels from wastewater to generate all the energy they need, and then some. “We can reclaim high-quality water from wastewater at almost no energy cost,” Luthy says. “It could go from being a liability to an asset.”