Water: Green Energy’s Ace, the Achilles Heel of Conventional Power
October 30, 2013
I’ve discussed water as the limiting factor on conventional energy before. This is one more reason why it is wrong to suppose the next 30 years of energy production will be the same as last – and one more way that climate change is sneaking up to bite fossil fools on the ass.
New study out of Argonne, profiles Texas as a microcosm – but the situation is global.
..up to now, studies that have tried to glean the most economically viable mix of technologies for generating electricity have focused on the mix needed to meet some sort of cap on CO2 emissions.
“But that never considered the water,” he says, even as other studies looked at the water consumption that coal, nuclear, or gas-fired plants require for cooling and for steam to spin the turbines running the generators.
Researchers call this confluence of water and energy production in a world facing an ever-warming climate the water-energy nexus.
The issue made headlines in August 2008, when the Tennessee Valley Authority had to temporarily shut down three reactors at its Browns Ferry nuclear power plant in Athens, Ala., after a drought reduced water levels in the Tennessee River and a heat wave boosted the water temperatures. In principle, the plant still could have used the water for cooling its reactors, but the temperature of the effluent pumped back into the river would have exceeded limits set to protect aquatic life. Two years later, low water levels forced the utility to throttle back the reactors there to 50 percent capacity.
Similar concerns over water temperature and availability have affected nuclear plants from Kansas and the Connecticut coast to Europe.
Nuclear plants are not the only types of generating facilities affected.
In Texas, the state’s power plants should be able to tap existing surface-water supplies through 2030, according to a study published in January that looked at the impact of weather variability on the state’s electric utilities and their future access to water.
But population growth and the need for more power plants are expected to force utilities to slake their thirst from other sources. These range from aquifers containing drinkable or brackish groundwater to some limited additional consumption of water currently being used to irrigate “low value” crops, the report suggests.
All of these are likely to be more expensive than currently available surface water supplies, according to the report prepared by energy and water specialists at Argonne National Laboratoryin Argonne, Ill.; Sandia National Laboratory in Albuquerque, N.M.; and the University of Texas at Austin.
This report summarizes a study to determine the medium‐term (through the year 2030) impacts of future climate and drought scenarios on electricity generation by the Electric Reliability Council of Texas (ERCOT). Because water in reservoirs is used to cool many steam cycle‐based power plants, significantly low water levels can reduce the ability to cool power plants. This reduced cooling ability can come from physical supply limitations or environmental constraints (power plant effluent temperatures exceeding permitted limits).
Water is projected to be available for ERCOT thermoelectric power plant operations until 2030. However, water for new development will likely need to come from sources other than unappropriated surface water. This conclusion largely means that future water supplies for thermoelectric power will be more expensive than historical supplies. Specifics are as follows:
- In general, very little unappropriated surface water is available for any use, including thermoelectric power.
- Water availability from appropriated surface water supplies, assumed as “low‐value” agriculture, is limited. This appropriated water is present in quantities > 5,000 ac‐ft/yr in only a few HUC8 basins.
- Several HUC8 basins have wastewater, potable groundwater, and brackish groundwater availability at greater than 10,000 ac‐ft/yr (enough for a large power plant).
- A number of basins (14) with severely limited water supplies are targeted for siting of new electric power production.
David Lochbaum, a former engineer at Browns Ferry who now works with the Union of Concerned Scientists, said last week that nuclear power plants are about 33 percent efficient, so two-thirds of the waste heat they generate has to be cooled using water. Lochbaum said increasingly hot water in the Tennessee River places another potential burden on Browns Ferry operations.
Lochbaum was part of a conference call last week with area environmental advocates who said electricity generation poses an ongoing strain on water resources, especially in times of drought or the reduced rainfall levels being experienced in North Alabama this year.
A study by the River Network, released last week, found that it takes on average 40,000 gallons of fresh water to produce a megawatt of electricity. The water is used, polluted or consumed in making the electricity, said Wendy Wilson, national director of the River Network’s energy and climate programs.
Wilson said a megawatt of electricity is generally what it takes to power a household for a month.
Browns Ferry has the capacity to generate 3,300 megawatts in the summer, according to TVA.
While the River Network and the Southern Alliance for Clean Energy both called for less water-intensive electricity production, such as wind and solar, the current system is stable, if somewhat challenged.