As new technologies like carbon capture and concentrating solar power emerge, extensive research and development is needed to understand the nexus between energy and water, experts told members of a House Science and Technology subcommittee yesterday.
In the movement from traditional energy sources toward cleaner, more efficient and renewable sources, some of the new technologies could use large amounts of water, making an understanding of the sector's impact on water use more critical, the experts added.
Rep. Brian Baird (D-Wash.), chairman of the Energy and Environment Subcommittee, claimed that if new power plants continue to be built with today's technologies, water consumption for energy generation will more than double to 7.3 billion gallons per day by 2030 from 1995 levels.
But even the new technologies could use large amounts of water.
For example, adding carbon capture technology to existing conventional coal-fired and natural gas-fired power plants would roughly double water consumption, Bryan Hannegan, vice president for environment and generation at the Electric Power Research Institute, said.
Adding carbon capture capabilities to today's power plants would result in a 30 percent reduction in power production and thermal efficiency, Hannegan continued, which means burning more coal to produce the same amount of power. That, in turn, would lead to more water usage for cooling.
Baird promised to "personally look into" carbon capture's water usage. "We've staked a tremendous amount of water on biomass and ethanol," Baird said. "But I also think we're staking a lot on CCS. I think too much."
Like carbon capture, next-generation biofuels could require massive amounts of water to produce. But those exact numbers are unknown, said Anu Mittal, director of natural resources and the environment at the Government Accountability Office. Her agency released a report yesterday that calls for more research and development on the water usage of commercial-scale next-generation biofuel production (see related story in today's Greenwire).
Little is known about the water use required to produce newer biofuels like those made from cellulosic feedstocks or algae because they have not been produced on a commercial scale, the report says.
"There are many uncertainties in the energy and water nexus," Mittal said.
Concentrating solar power, or solar thermal, is another emerging renewable technology that could have a serious impact on water resources. Solar thermal power plants trap the sun's heat by focusing mirrors onto thermal receivers and producing steam to drive turbines.
"Solar-based electricity will be a key enabler in achieving our renewable energy goal, but water is also a key ingredient for electrical power generation and must be allocated in a total systems management approach," said Terry Murphy, president of SolarReserve, a California-based solar company.
Lawmakers agreed with the experts that more research needs to take place to understand the interwoven relationship between energy generation and water.
"Energy and water are co-dependent," said Richard Stanley, vice president of the engineering division at General Electric Energy. "Energy is required for producing water, and water is required for producing energy."
"Climate variability and demand growth affect both our water and energy resources, and it is critical that we acknowledge that interdependency and develop technologies and adopt practices that allow us to manage these resources most effectively," Baird said.
Massive amounts of water are needed in today's thermoelectric power plants for cooling, said Kristina Johnson, undersecretary of energy at the Energy Department. And 90 percent of the nation's electricity is derived from thermoelectric plants. She said a 2005 DOE report estimated the U.S. thermoelectric power-generation sector withdrew 147 billion gallons of water per day, and 3.7 billion gallons were consumed each day for cooling systems.