Events

Energy water nexus

Q: I understand how pumps use energy to distribute water but is there more energy needed to provide water for consumers? A: Yes. There are many aspects within what is referred to as the “Energy-Water Nexus” which correlate energy and water to one another. Water is needed to produce the energy needed to distribute the water. But what does that mean? According to the EPA, every kWh of energy delivered demands the participation of 25 gallons of water. A pump that sends treated water to your home is run on electricity provided by your utility. Let’s assume these kWh are created by a coal fired power plant, nuclear plant or a natural gas plant. All of these are combustion processes expelling heat to turn a turbine. This turbine then needs to be cooled, by water which is pumped in using electricity already produced. Power plants water use is shown in the table below in gallons per Megawatt-hour. Furthermore, water is used in both coal and natural gas mining and extraction. Producing natural gas from shale requires about 0.6 to 1.8 gallons of water for every million Btu (MMBtu), less than 15 percent of the water needed to produce the equivalent amount of energy from coal (Chesapeake Energy, Media Resources: Hydraulic Fracturing Fact Sheet, 2009.). What about transport of the coal or natural gas to the power plant? This uses diesel and gas, of which water is used in both the extraction and refinement processes! And for natural gas, booster pumps would be needed to transport the gas through the pipeline. And what do you think those booster pumps will be powered buy? You guessed it, more kWh created by the same process it is working to feed. As you can see there is a significant correlation between water usage and energy usage. Even a small scale efficiency improvement will have a large ripple effect all the way down the line impacting the total water resource allocation for that gallon of water or kWh of energy you are using!

Source: ew3-freshwater-use-by-us-power-plants.pdf