I read an article last week in the Austin-American Statesman about water use and the potential shortages Texas may face in the all-too-near future, with conditions being exacerbated by the current drought . The article brought to my attention the vulnerability of not only the availability of clean drinking water but of power as well. According to the article, water may become a new limiting factor for power production.
Electricity generation requires water for a variety of reasons, steam production, cooling, equipment cleaning, and other purposes; requirements for each technology or fuel source vary . “Approximately 89% of the energy produced in power plants is generated by thermoelectric systems” . Although a great majority of this water is reused or put back into the original water source, a portion of that water is evaporated or consumed; a 2003 study from NREL determined that in Texas, approximately 0.44 gallons of water are consumed per kWh produced .
With energy consumption rising exponentially, water consumption will continue to rise as well, and in semi-arid, highly populous regions like we see in Texas, this can potentially create a huge problem. So, putting the water consumption used during extraction or production of the fuel aside (i.e. hydraulic fracturing for natural gas, corn for ethanol), how can we make these power plants more efficient by using less water?
One option is a dry cooling system. These systems reduce water consumption by more than 90%, however, there is a loss in efficiency, as heat transfer by air is not as effective as with water; an estimated 1.5% of power generated through a dry cooling system goes to powering additional fans needed to facilitate the air-cooling process alone . Furthermore, a study done by the DOE found that dry cooling systems can be three to four times as expensive as the traditional wet cooling system as well . Because of these current limitations, this technology is rarely seen in the US. The system is not a complete bust though; one opportunity that has been mentioned is retrofitting older wet cooling systems, adding a dry cooling component; this would allow the plant to switch over to the dry cooling system during colder months, when the system is most efficient (less additional power is needed to cool) . I think this option sounds very promising. At least it could be a step forward toward more water-conscious power plants, while in the mean time more R&D can go into developing technologies that can help to further mitigate this problem.
- Mashood, Farzad. “Texas in Drought: Rethinking How We Get, Use Water.” Austin-American Statesman. 29 January 2012.