Saturday, July 19, 2014

The Water-Energy Nexus Is a Problem in a Warming World

Global water use for energy production in the New Policies Scenario by fuel and power generation type. (Credit: WEO-2012) Click to enlarge.
Energy production depends on water.  It is used in power generation, primarily for cooling thermal power plants; in the extraction, transport and processing of fuels; and, increasingly, in irrigation to grow biomass feedstock crops.  Energy is also vital to providing freshwater, needed to power systems that collect, transport, distribute and treat it.  Each resource faces rising demands and constraints in many regions as a consequence of economic and population growth and climate change, which will amplify their vulnerability to one another.

For the energy sector, constraints on water can challenge the reliability of existing operations as well as the physical, economic and environmental viability of future projects. Water constraints can occur naturally, as in the case of droughts and heat waves, or be human-induced, as a result of growing competition among users or regulations that limit access to water.  In the summer of 2012, for example, a delayed monsoon in India reduced hydropower output at the same time electricity demand was running high, contributing to two days of blackouts that affected an estimated 660 million people. Equally important to water-related risks confronted by the energy sector, the use of water for energy production can impact freshwater resources, affecting both their availability (the amount downstream) and quality (their physical and chemical properties).

The IEA, for the first time in the World Energy Outlook 2012, examines the water for energy relationship, reviewing water requirements for different energy sources and estimating total freshwater needs by scenario, energy source, and region.

The findings show that the scale of water use for energy production is tremendous.  Some 580 billion cubic metres of freshwater are withdrawn for energy production every year.  At about 15% of the world’s total water withdrawal, the figure is second only to agriculture. To put it another way, the energy sector withdraws water at approximately the same rate that water flows down the Ganges (in India) or Mississippi (in the United States) Rivers – some of the very largest in the world.

The vast majority of water used in the energy sector is for cooling at thermal power plants, as water is the most effective medium for carrying away its huge quantities of waste heat. Though the amount used for biofuels and fossil fuels may appear minor on a global level, this must be viewed in the context of local water resources and potential risks posed to water quality.  Water withdrawal by the energy sector is expected to rise by one-fifth through 2035, while the amount consumed (not returned directly to the environment) increases by a more dramatic 85%.

What does this mean for future energy supply?  Given the location-specific nature of water resources, this question must be considered at the water basin level, or even at particular sites.  Power generation in parts of China, India and the United States will likely have to deploy more and more technologies fit for water-constrained conditions.  And the development of unconventional oil and gas resources, which raises notable water-quality risks, will be challenged to follow high standards that commit industry to continually improving environmental performance.

The Water-Energy Nexus Is a Problem in a Warming World

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