Saving Energy Means Saving Water Too

Jessica Kennedy | Jun 05, 2013

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The connection between energy and water, often referred to as the "energy water nexus" is collecting attention from business leaders, policy makers, and citizens alike. In short, this term refers to the close link between water and energy.

Water is used in nearly every aspect of energy production. So, saving energy will save water, and saving water will save energy. When we consider that demand for electricity is supposed to increase significantly in coming decades, it is clear that water consumption will also increase.

This links adequate water supply directly to the energy security of our country. Clean energy technology such as biofuels and carbon sequestration actually require large amounts of water to produce, so while they cut down on greenhouse gas emissions, they may actually contribute to water pollution and waste. Wind and solar power are the cleanest energy sources in terms of both water and carbon emissions.
 
Electricity, in particular, has a significant impact on our water supply. Fossil fuel generation, nuclear power, and hydroelectricity all consume large amounts of freshwater. It is estimated that fossil fuel generation alone comprises about 39% of all freshwater withdrawals in the US, which equals about 136 billion gallons of water per day. When you do the math, it turns out that every single kWh of electricity uses about 40 gallons of fresh water.

Water is also used intensively for extracting the fuels that generate our electricity. Coal, oil and natural gas all require a significant water supply to acquire, and, in most cases, contribute to fresh water pollution.

Hydraulic fracturing or "fracking" is one of the most controversial topics currently circulating in the energy sector. It is a hot topic because chemicals are mixed with water and injected into rock to release gas or oil. There is still debate over whether or not this practice seriously contributes to pollution of the water table.
 
On the other hand, clean water has a sizeable footprint when it comes to electricity. Electric power is used to treat and pump water supply to homes and businesses. In fact, the water industry consumes about 100 million MWH of electricity per year. This is equal to about 4% of all generated power and most of that energy is used by water pumps. The interconnection between water and energy means that conserving one will help conserve the other. By becoming more energy efficient we become more water efficient, and vice versa.
 
As energy efficiency and smart grid initiatives are more commonly adopted across the world, similar solutions to the problem of water efficiency may follow suit. The fact is that electricity demand in the US is rising, especially in regions typically strained for water supplies, such as the Midwest, which experienced serious draught last year. This means water supplies will need to be conserved as much as possible going forward and one way to help this happen is to become more energy efficient.
 
The energy water nexus reminds us that our resources are not isolated. We often don't remember how reliant we are on a good water supply. Water and energy also both contribute to operating expenses of business and industry. Enacting energy conservation methods in these sectors not only conserves resources, but can save money as well.
 
Jessica Kennedy, energy consultant, Energy Curtailment Specialists, Inc.

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Comments

water-energy issues

Important issues which are finally getting needed visibility.  It is an area in which I have worked for more than a decade and is the subject of the second 'Post' on my new blog www.lapsedphysicist.org. 

Water & Energy

The 39% of freshwater withdrawals cited in the article is a compelling number. We are in the midst of an historic drought in the southwest. It is fascinating that the "water conservation" discussion always turns to "lawns and golf courses", without taking into account that "peoples" use of water represents 3% of usage. Tackling the issue of reducing water usage in power generation is nuclear for politicians, I have never heard one bring up the issue.

I am interested in hearing more from Bill Card regarding the issue of "withdrawals" vs. "consumption". In particular, what are the "consumption" percentages for power, agriculture, and people in the Southwest?

Also, while a "once through" cooling system may be more efficient, raising the temperature of the river or lake will increase evaporation so the usage cannot be zero.

Saving Water and Energy

Saving water and saving energy are both strategic, but they are not always saved in parallel as the author suggests.

A powerplant with a once-through cooling system "withdraws" a lot of water, but returns it all to the lake or river it came from.  it can then be reused for drinking, irrigation, fishing, or boating.

By contrast, a plant with a cooling tower withdraws less water, but the water is consumed by evaporation and lost to the river. The plant with a cooling tower is less efficient, due to higher temperature for heat rejection, so it actually "saves" less energy than the once -through plant.

Bill Card

Cooling System Specialist