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09.09

Congress and the U.S. Department of Energy (DOE) are focusing intensified attention on the energy-water nexus, particularly in the context of efforts to develop advanced technologies which promise to substantially reduce water withdrawals and consumption by electric power plants.

“We have tended to think about these two essential resources independently,” Rep. Brian Baird, D-Wash., chairman of the House Science and Technology Subcommittee on Energy and Environment, said in opening a 9 July hearing by the panel. “However, the strong linkage between water and energy requires that we make a more concerted effort to ensure that water and energy technologies are being developed synergistically.”

Baird noted that if new power plants continue to be built with today’s technologies, consumption of water for electrical energy production could more than double by 2030, from 3.3 billion gallons per day in 1995 to 7.3 billion gallons per day.

Rep. Bob Inglis, R-S.C., the subcommittee’s ranking Republican, observed that electricity generation is the second largest use — only slightly behind agricultural irrigation — of freshwater withdrawals in the United States. “The technologies we use today are very water-inefficient, despite the availability of cooling systems that substantially reduce our water needs. As we change our choice of fuels in order to minimize our greenhouse emissions, we should also work to minimize the strain we put on our limited water resources.”

Inglis added that he is encouraged by the work of DOE’s National Energy Technology Laboratory (NETL), headquartered in Pittsburgh, Pa., to develop technologies that will reduce water withdrawals (water typically pumped from a river or lake, used for power plant cooling, then returned to the source) and water consumption (water which evaporates from cooling towers or is otherwise lost).

At the 9 July hearing, DOE Under Secretary Kristina M. Johnson, an IEEE Fellow, emphasized the increasing importance of the energy-water nexus and summarized the current status and planned future directions of research and development activities in this area, by NETL and other components of the DOE National Laboratories system.

“Water, once considered a nearly inexhaustible resource, is becoming constrained in many areas, and water requirements for electricity production may compete with other demands, such as agriculture and sanitation,” Johnson said. “The August 2007 drought in the southeastern United States underscored this issue with several nuclear plants in the region reducing their output by up to 50 percent due to low river levels. This situation could be exacerbated as more areas become drought-prone due to changing climate.”

In order to help reduce greenhouse gas emissions, DOE and the electric power industry have come under increasing pressure from environmentalists to develop and deploy improved technologies for carbon capture and sequestration.

Commenting on this emerging area, Johnson observed that “using today’s technologies, capturing carbon dioxide (CO2) from existing coal and natural gas plants, or from new fossil-fuel fired plants, would increase water consumption because capturing CO2 requires the addition of several processes that are both energy and water intensive. Processes that use solvents to capture CO2 require energy to regenerate the solvent so it can be used again.”

“Once CO2 is captured, it must be compressed for sequestration or beneficial use, with compressors usually having significant operating power and cooling requirements. These processes are common for both conventional fossil-based combustion processes and advanced technologies such as IGCC [Integrated Gasification Combined Cycle]. The added internal energy requirements for these processes can effectively subtract 10 to 30 percent of the energy from the net plant power output and also correspondingly increase water consumption,” the DOE official testified.

Another witness at the 9 July hearing, Richard L. Stanley, vice president, engineering division, GE Energy, told the House panel that “at GE, we see the importance of achieving water and energy efficiencies across our own portfolio of businesses.” This includes doubling GE’s level of investment in clean research and development from $700 million in 2005 to more than $1.5 billion by the year 2010.

“It could be said our economy runs on water,” Stanley testified. “Unfortunately, water demand already exceeds supply in many parts of the world. . . . Energy and water are co-dependent. In simplest terms, energy is required for producing water and water is required in the production of energy. Globally, the demand for both of these crucial resources is projected to grow at an alarming pace, with energy demand doubling and water demand tripling in the next 20 years.”

The GE executive contended that “the nexus between power generation and water usage is one of the world’s most complex and critical public policy challenges.”

Earlier this year, Sen. Jeff Bingaman, D-N.M., chairman of the Senate Energy and Natural Resources Committee, introduced a bill, S. 531, the Energy and Water Integration Act of 2009, to help deal more effectively with the energy-water nexus.

“I believe this bill is a good first step toward integrating energy and water policy,” Bingaman said at a 10 March hearing by his committee. “We may need to do more. . . . Developing new policies that integrate energy and water solutions will become increasingly vital as populations grow and environmental needs increase and a changing climate continues to affect our energy and water resources.”

Bingaman’s bill calls for three studies to be undertaken in this area: (1) a National Academy of Sciences study to assess water use associated with developing fuels in the transportation sector, and also water consumed in different types of electric power generation; (2) a DOE study to identify best available technologies and strategies for efficiently minimizing water use in electricity generation; and (3) a Bureau of Reclamation study to evaluate energy use in storing and delivering water from reclamation projects.

IEEE-USA 2008 President and IEEE Fellow Russell Lefevre told Today’s Engineer Online with regard to the energy-water nexus: "The Energy-Water nexus is a very important issue that is just starting to get the public attention it deserves. IEEE-USA is getting up to speed on the issue and welcomes input from members who are knowledgeable in the area."

Lefevre added that IEEE-USA has been “strongly promoting PHEV technology and, more broadly, electrifying the transportation sector. To the extent that is successful, it will put a much larger demand on power plants. In the near term I believe that means coal-fired plants, nuclear and thermal solar plants will have to generate more electricity. All require significant withdrawals of water now and will require more as the demand goes up. One of the concerns I have is that carbon capture and storage (CCS), which is being promoted as a way to help coal-fired power plants emit less carbon dioxide into the environment, requires significantly more water than conventional power plants.”

Barton Reppert is an independent science and technology writer who mainly focuses on Washington coverage of S&T policy issues. He previously worked for 18 years as a reporter and editor with The Associated Press in Washington, New York and Moscow.

Comments may be submitted to todaysengineer@ieee.org.