The Water-Energy Nexus: Utilities

on November 16, 2012 at 12:00 PM

Water is an essential to human existence and yet our power generation-infrastructure levies huge demands on this increasingly scarce resource. Power plants use considerable amounts of water for cooling, while discharging higher temperature wastewater that can contain contaminants that pollute our water systems and damage local ecosystems in the process.

For instance, according to the Energy Information Agency in 2011 coal-fired generation provided about 42 percent of the electricity in the United Stated and use either closed-loop or open-loop cooling systems to condense the water after it has been used to create steam to power turbines to provide electricity to our homes and businesses.

According to estimates from the U.S. Department of Energy’s National Energy Technology Laboratory, 43 percent of current thermoelectric power plants use open-loop cooling, 56 percent use closed-loop, and only 1 percent use dry cooling.

Coal-fired power plants generally rely on closed-loop cooling systems or cooling towers that withdraw on average between 500 and 600 gallons of water per MWh and yet lose most to evaporation. Open-loop systems have much higher withdrawals between 20,000 and 50,000 gallons per MWh, or about the amount of water it takes to fill your local swimming pool, and dispel the now warmer water into the local source, which can cause damage to local ecosystems.

The math gets even more staggering when you consider that this is per MWh. For instance, in the case of a 500MW coal-fired plant, you would multiple the 500 MW at 50,000 per MWh – that is 500 multiplied by 50,000 gallons or roughly the equivalent of filling 500 swimming pools each hour. It is easy to see that neither of these systems provides great solutions to reduce their heavy dependence on water usage.

For some water advocates, dry cooling systems are the answer. A system where air is used instead of water to cool steam as it exits the turbine can decrease water usage at power plants by nearly 90 percent. However, higher costs and lower efficiencies have been huge hurdles to market adoption. Power plants using air-cooling consumes about 4% of the electricity they generate to run the air-cooling fans. Yes, air-cooling lessens water consumption but increases fossil fuel burning.

With water being such a vital part of our lives, it is surprising that thermal power plants haven’t found ways to reduce water consumption at a scale to make power production more sustainable. There are efforts to revolutionize water usage for power plants including coal-fired ones, alleviating the need for cooling towers altogether.

Currently, innovative processes are being developed that utilize the heat of the steam discharged from turbines to desalinate/de-mineralize source water while simultaneously condensing the steam itself, eliminating heavy water consuming wet cooling towers and electric consuming dry cooling towers. This would provide a huge boost to making power plants more sustainable, protecting local ecosystems, and would reduce a heavy siting, installation and ongoing cost for power-plant owners. An extra benefit to this method is that as a byproduct of this process, plants will have extra distilled water left over that the plant could sell back to local farms and communities, for instance. If new methods handling water for thermal power plants can be brought to industry at a reasonable cost, a huge burden on a dwindling resource could be alleviated. Let’s all hope that technology can save us from trading our water for our energy.

R. Oğuz Çapan is the Chairman and Chief Technology Officer of Hittite Solar Energy and has over 30 years of international experience in design, construction and operation of oil and gas production facilities. Several years ago, Oğuz decided to switch to the renewable energy sector. He sold his oil company active in Algeria, Libya, Azerbaijan, Peru and spent over a year evaluating existing renewable energy technologies.

As a result of his research, he decided to start a renewable energy design company focused on improving the parabolic solar trough design to allow for Direct Steam Generation (DSG). Oğuz also innovated a low-temperature Desalinization Water Treatment System that won the “DM 2006” competition organized by the World Bank and Bill Gates Foundation.