Mohave Generating Station, a 1,580 MW thermal power station near Laughlin, Nevada fueled by coal (Credit: Kjkolb, Wikimedia Commons)
According to the U.S. Geological Survey, in the United States more fresh water is now used for thermoelectric power production (41%) than for agricultural irrigation (37%). Innovations in power plant cooling could therefore provide much needed aid in promoting water conservation efforts. The Energy & Environmental Research Center’s (EERC’s) novel dry cooling project, which has the potential to reduce the largest use of water in the United States, was recently awarded one of just 66 cutting-edge research project awards given by the U.S. Department of Energy (DOE) Advanced Research Projects Agency-Energy (ARPA-E) “Open 2012″ Program.
Most thermoelectric power is generated through the steam-driven heat engine process known as the Rankine cycle. Heat is generated from the combustion of conventional and renewable fuels, solar and geothermal energy, or nuclear fission and is used to boil water to make high-pressure steam that is expanded through a turbine to generate power. Water is then used to condense the exhausted steam and dissipate heat to the environment. Water-based cooling is cost-effective and efficient, but lack of water availability in many areas may limit opportunities for utilities to meet the needs of the industry.
The most prevalent cooling option for power generation is once-through (or open-loop) cooling because it requires the lowest capital costs. Large amounts of water are withdrawn from a body of water for cooling. Although most is returned to the water source, it is at a higher temperature, altering aquatic ecosystems. This has led to regulatory pressure from the U.S. Environmental Protection Agency to switch to technologies with less environmental impact. Closed-loop systems recycle the cooling water and, therefore, withdraw less, but virtually all of the water withdrawn is consumed because of evaporative losses. Conventional dry cooling systems don’t work as efficiently as a wet cooling system; they also don’t produce as much electricity during hot weather and cost three to four times as much.
Instead of using water for cooling, the EERC’s novel dry cooling technology uses a liquid drying agent, which is nonvolatile and does not evaporate. There is no net water consumption, and the original working fluid is expected to last for the life of the system. The novel dry cooling technology is intended to address the key shortcomings of conventional dry cooling technologies: high capital cost and degraded cooling performance during daytime temperature peaks. If the EERC’s novel dry cooling system proves to be cost-competitive, it could be a tremendous breakthrough in cooling, particularly for water-starved areas of the western United States.
“By eliminating the largest user of water at power plants, the EERC’s novel dry cooling technology has the potential to advance the nation’s long-term sustainable energy and economic development,” said EERC Director Gerry Groenewold.
ARPA-E awarded the EERC $472,586 to develop heat-exchange surfaces for use with the system. The objective of the ARPA-E project is to determine if the EERC’s novel dry cooling technology can be turned into a marketable technology. Although drying agents are widely used in air-conditioning systems and for humidity control applications, using drying agents for cooling appears to be a unique idea, according to Chris Martin, EERC Research Engineer and project manager for the EERC’s novel dry cooling project.
“Based on the testing performed under previous projects, the underlying concept for using a nonvolatile liquid drying agent to dissipate heat to the atmosphere appears valid,” said Martin.
“ARPA-E funds concepts that have a clear market application but pursue a fundamentally different technology path, one that holds the promise of significant benefits over conventional approaches,” said Martin. “As our proposal to ARPA-E stated, ‘the purpose of this project is to transform this dry cooling technology from a novel concept into a revolutionary technology with significant cost and performance benefits compared to existing dry cooling technology.’”
The ARPA-E Program, which began in 2009, now has a total portfolio of some 285 projects for an award total of $770 million. It has already resulted in funded projects that have made significant progress: the world’s first 400-Wh/kg lithium-ion battery, which is poised to revolutionize the electric vehicle industry; a wind turbine, inspired by the design of jet engines, that could deliver 300% more power than existing turbines of the same size and cost; and a high-power laser drilling system that can penetrate hard rock formations over long distances and is ten times more economical than conventional drilling technologies.
Competition for the ARPA-E awards is steep, and the EERC’s project is the program’s first award in North Dakota. The EERC’s application began as a concept paper that described the merits of the proposed technology and was developed further after the EERC was encouraged to submit a full proposal. Typically, only one-third to one-half of the concept papers submitted are encouraged to submit full applications, and few of these are funded. For example, in its first year, ARPA-E received 3700 concept papers and eventually elected to fund 37 merit-based projects worth a total of $151 million.
As an awardee, the EERC was recently invited to participate in the Technology Showcase at the 4th Annual Energy Innovation Summit in Washington, D.C.
“Our project was the only one there dealing directly with the issue of improved power plant cooling,” according to Martin. “A number of attendees stopped by to reinforce the need for what we are working on.”
