Energy’s Water Dependence
Posted August 3, 2011 at 1:15 pm 
Filed in: By the time August arrived, the thick of summer had ensnarled the nation in a record-breaking drought. Nearly 12 percent of the United States experienced “exceptional” drought conditions in July – the National Drought Mitigation Center’s most severe classification. Now 18 percent of the nation is experiencing “extreme” or “exceptional” drought conditions, with the south-central tip – Texas, Oklahoma, Louisiana and New Mexico – facing the blunt of the heat.
A recent post discussed the strain that severe weather can have on the electrical grid. The complications droughts can have on energy production are an equally pressing concern.
Nearly every stage of energy production requires water: from oil drilling, to coal mining, to power plant generation. And in general, many potential liquid fuel replacements require more water during production than conventional gasoline. For example, liquid fuel production from coal uses more water than conventional gasoline production on an energy-equivalent basis. Gasoline produced from enhanced oil recovery uses 55X more water than gasoline produced from standard drilling methods. At the far end of the water-intensity spectrum, corn ethanol production uses more than 39,000X more water than gasoline produced from standard drilling methods. And soy ethanol production requires 3.8X more water than corn ethanol production, 149,000X more water than gasoline produced from standard drilling methods.
What about the current “it” fuel of energy companies? Shale natural gas requires significant quantities of water – typically on the order of 100,000 barrels for a high-volume hydraulic fracturing. However, while shale production is water intensive, at 1 gallon of water per million BTU produced, it is relatively low in comparison to other energy production mechanisms.
It is important to note that in hydraulic fracturing, where steam is blasted underground, water is “withdrawn” before it is recycled back to its source. In contrast, water “consumption” means that the water is unavailable for further use (as in the case regarding agriculture feedstocks for biofuels, or water vapor emitted from power plants). Of course, water withdrawal does not mean that the water has not been altered; for example, the temperature of the returned water may not be suitable for human consumption.
Lastly, electric generation is hardly exempt from water use. Power plants need water for two reasons: 1) to create steam to drive the generator and 2) to cool the power plant. This is particularly relevant due to the rising demand of electric and hybrid vehicles. Since their fuel source comes from the grid, it is estimated that on average, plug-in electric hybrids use 3X more water consumption, and 17X more water withdrawals than gasoline-powered vehicles.
Ultimately, energy’s unavoidable need for water is largely dependent on local conditions, such as available water resources, timing and extent of withdrawals, and regional climate. Yet extreme droughts that cause widespread shortages can heighten the competition for water resources between irrigation and energy production. Exceptional droughts that create water emergencies directly conflict with power plants’ needs for an ample and certain water supply. Lack of water conditions could force power plants to reduce operations, requiring additional electricity to be purchased elsewhere on the gird, and rise electricity costs.
Current technologies such as closed-loop systems and dry cooling can lessen power plants’ water intensity. In the future, heavy water portions used in enhanced oil and gas recovery can be displaced with CO2.
Nevertheless, water is, and will continue to be, a vital input of future energy supply. With the possibility of more frequent and extreme summer droughts, this additional factor will further strain an already stressed energy system. Solutions will require water resource management to play a more prevalent issue in the energy security discourse.
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