A new study by researchers at The University of Texas at Austin has estimated the energy embedded in the U.S. water system. Kelly Sanders, a PhD candidate in Mechanical Engineering at UT Austin, compiled and allocated energy consumption for various water-related activities in the residential, commercial, and industrial sectors. The study, “Evaluating the energy consumed for water use in the United States”, appears in the September issue of Environmental Research Letters.
Based on Sanders’ analysis, a little over 46 quads of energy (one quad is a quadrillion BTUs) are related to water. This means energy is used in one way or another to create steam for power generation (or other processes like sterilization) or for heating, cooling, or pumping water directly. Of the 46 quads, a majority (34 quads) of water-related energy is consumed for power generation (burning fuel to create steam to turn turbines), while just over 12 quads is used directly to heat, chill, pump, treat water, or in direct steam processes. For perspective, the total primary energy consumption of the United States in 2010 was 98 quads.
The studies results can be summarized in the following diagram:
“Although we've been saying for years that there is a lot of energy embedded in water, we really didn't have a number to back that up. We wanted to know whether "a lot" was 5% of annual energy use? 10%? 15%? As it turns out ~13% is a lot,” Kelly Sanders explained in an email.
The study also identifies an interesting policy issue: roughly 25% more energy is used to heat, cool, or pump water than is used for lighting (in the residential and commercial sectors) in the United States – about 5 quads. So why are more efficiency policies and technologies targeted towards lighting and not water conservation? Walk in to any Home Depot or Lowe's and you’ll see displays advertising the benefits of more efficient lighting. IKEA is taking this a step farther; the Swedish retailer will only be selling LED light bulbs come 2016.
Looking for low flow showerheads, faucet aerators, and water heater timers? These exist, yet they are a harder to find, even though these have the benefit of reducing water consumption and energy consumption (less water to heat).
Part of the issue, I think, is water pricing. Water is insanely cheap (at least in the United States), and conservation efforts like low flow showerheads only reduce revenue for those who make money by selling water. Saving water might be a good thing practically, but a utility generally sees its job as selling more, not less, or its product (like water). At least for some electric utilities, energy efficiency measures can be rationalized in terms of avoided kilowatts – eventually summing up to an avoided (and costly) power plant. What is the corollary for a water utility? As long as there is water in the reservoir, why not sell as much as possible? And if water is cheap for the end user, why spend money on conservation efforts?
As nearly every indicator suggests, water resources are becoming more strained. NASA’s Earth Observatory (big fan!) points out decreasing groundwater storage and dryer than normal conditions across most the country. Half the state of Texas was on fire last year. Idaho is on fire this year. There are countless more examples.
Water efficiency policy (which is also energy efficiency policy) needs to catch up with the reality that water resources are limited and becoming harder to come by, and that a significant amount of energy is used for water.
You can read the full paper here.