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Water and Electricity: Why You Can’t Have One Without the Other

by Lee DeBaillie, program director

Two of the wonders of modern civilization are also unappreciated: clean water from a tap and electric power with the flip of a switch.

We avoid untold drudgery and illness using present-day drinking water systems that gather, clean and distribute water right where we need it. Our “used” water is then collected by wastewater systems, whisked away, cleaned, and discharged safely to the environment. Furthermore, with the flip of an electric switch, our fingertips can direct the power equivalent of a team of horses to washing clothes and dishes, lighting the night and connecting our information devices to the globe. Similar to water, our modern electric systems gather raw energy, refine and transform it, and distribute it right where we need it. We all benefit enormously from these water and electric systems. What is less known is that that these two wonders are inseparably linked. There can be no water from your tap without electricity, and there is no electricity from your switch without water.

Electricity in the water

Much of the electricity used to supply water is consumed in pumping. To collect water, it is pumped from below ground or from surface water such as lakes and rivers. It then needs to be pushed through pipes to the water treatment plant, pushed through treatment systems (such as filters) and pushed through more pipes up to a water tower (typically). From there, gravity does the work to push the water to your home. This pumping consumption, along with some miscellaneous treatment plant consumption, on average adds up to about 1.5 kilowatt-hour of electricity consumed per thousand gallons [kWh/kgal] of water [1,2]. This does not include energy that may be applied to the water in your home, such as heat for hot water.

When the water goes down the drain, it requires more electricity. The wastewater is collected, pumped, treated and discharged. An additional 1.7 kWh/kgal of electricity is expended on wastewater pumping and treatment [3].

So, in total, and the amount varies depending on where you live, about 3.2kWh of electricity is consumed for each thousand gallons of water delivered to your home. For a kitchen faucet delivering five gallons per minute of water, the water-embodied electricity is pouring out at about 1,000 watts. That’s like running a virtual hairdryer every time you turn on the faucet. 

Water in the electricity

Most of the power plants in the U.S. generate heat to produce steam, which then spins a steam turbine coupled to an electric generator. To get maximum efficiency from the power plant, the steam must be condensed using cooling water. Sometimes the warmed cooling water is then discharged to a river, lake or ocean, slightly increasing the evaporation rate of the body of water. More often, cooling towers use the cooling effect of evaporating water to remove the heat from the cooling water. Nationwide, these power plants evaporate about 0.5 gallons of water for every kWh of electricity generated [4].

Hydroelectric power plants avoid the use of steam by using the energy of falling water behind dams to spin water turbines coupled to electric generators. This type of power plant avoids the water losses associated with cooling towers, however, the water reservoirs behind the dams increase evaporative water losses. Nation-wide these power plants evaporate 18 gallons of water for every kWh of electricity generated [4].

Hydropower provides about 9% of the U.S. electric needs, so the weighted water consumption nation-wide is about 2.0 gallons/kWh [4]. Put another way, if you turn on a 1,000-watt toaster, you’ve also turned on a virtual stream of water running at 0.03 gallons/minute–about the water flow from a drippy faucet. It may not seem impressive, but over the span of a year it’s around 20,000 gallons for the average home.

Conclusion

While easy to take for granted, our modern water and electricity systems are pillars of civilization. Like much of our civilization’s underlying infrastructure, these systems are intertwined in complex ways. This underscores the importance of an informed and systems-based perspective when applying, modifying and improving critical infrastructure within our society.

 

Sources

[1] Elliott, T., Zeier, B., Xagoraraki, I., and Harrington, G. W. 2003. Energy Use at Wisconsin’s Drinking Water Facilities, Energy Center of Wisconsin, Madison, WI.

[2] EPRI (Electric Power Research Institute). 1996. Water and Wastewater Industries: Characteristics and Energy Management Opportunities, Report CR-106941.

[3] Cohen, R., Nelson, B., and Wolff, G. 2004. Energy Down the Drain. The Hidden Costs of California’s Water Supply. Natural Resources Defense Council. Oakland, California.

[4] Torcellini, P. Long, N., and Judkoff, R. 2003, Consumptive Water Use for U.S. Power Production, Report NREL/TP-550-33905, National Renewable Energy Laboratory, Golden, Colorado.

 

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