InfrastructureHow much water is needed to produce various types of energy?

Were you
aware of the fact that most of the energy we consume daily, such as electricity
or natural gas, is produced with the help of a dwindling resource — fresh
water? Virginia Tech professor Tamim Younos and
undergraduate student Rachelle Hill are
researching the water-efficiency of some of the most common energy sources
and power generating methods. Younos, associate director at the Virginia
tech-based Virginia Water
Resources Research Center and research professor of water resources in the
College of Natural Resources, and undergraduate researcher Hill, of Round Hill,
Virginia, who is majoring in environmental science and aquatic resource
concentration in the College of Agriculture and Life Sciences, have analyzed eleven
types of energy sources, including coal, fuel ethanol, natural gas, and oil;
and five power generating methods, including hydroelectric, fossil fuel
thermoelectric, and nuclear methods. Younos said they based their calculations
on available governmental reports by using a standard measurement unit, which
makes this study unique. “Our unit is gallons of water per British Thermal
Unit (BTU),” explained Younos. “We selected BTU as a standard unit
because it indicates pure energy as heat and is applicable to all energy
production and power generation methods.” According to the study, the most
water-efficient energy sources are natural gas and synthetic fuels produced by
coal gasification. The least water-efficient energy sources are fuel ethanol
and biodiesel. In terms of power generation, Younos and Hill have found that
geothermal and hydroelectric energy types use the least amount of water, while
nuclear plants use the most.

Hill took
the study one step further and calculated how many gallons of water are
required to burn one 60-watt incandescent light bulb for twelve hours a day,
over the course of one year. She found that the bulb would consume between
3,000 and 6,000 gallons of water, depending on how water-efficient the power
plant that supplies the electricity is. Hill added that the results are
estimates of the water consumption based on energy produced by fossil fuel
thermoelectric plants, which produce most of the U.S. power — about 53 percent.
“The numbers are even more staggering if you multiply the water consumed
by the same light bulb by the approximately 111 million U.S. homes,” said Hill. “The
water usage then gets as high as 655 billion gallons of water a year.” By contrast, burning a compact fluorescent
bulb for the same amount of time would save about 2,000 to 4,000 gallons of
water per year. Younos noted that the results of this analysis should be
interpreted with a grain of salt. “There are several variables such as
geography and climate, technology type and efficiency, and accuracy of
measurements that come into play. However, by standardizing the measurement
unit, we have been able to obtain a unique snapshot of the water used to
produce different kinds of energy.”

This study is part of a multi-college
partnership at Virginia Tech led by Younos that proposes a unique approach to
managing water and energy resources, called the Decentralized Energy and Water
Systems. Another research theme under the scrutiny by the Decentralized Energy
and Water Systems scientists is to study rainwater harvesting as an alternative
to using water from the public system for non-potable uses and the impact of
rainwater harvesting on water and energy conservation and stormwater
management. The partnership’s team members at Virginia Tech include professors
Younos, project leader; Darrell Bosch, Department of Agricultural and Applied
Economics; Richard Hirsch, Consortium on Energy
Restructuring; Vinod Lohani, Department of Engineering Education; Madeline
Schreiber, Department of Geosciences; and Monica Licher doctoral student in
environmental design and planning.