The concept of the water-energy nexus is a broad, over-arching term for the relationship between water and energy production systems, including both electricity generation and fuel extraction. Water plays an important role in all phases of fuel extraction and electricity generation. In turn, energy is required to extract, convey, and deliver water of appropriate quality for its diverse uses. In 2014, the U.S. Department of Energy (DOE) released their report on the water-energy nexus, citing the need for joint water-energy policies and better understanding of the interconnection and its susceptibility to climate change as a matter of national security.
Figure 1: The complex dependence of water and energy systems. Source: US DOE
Power Generation and Water Consumption
As shown in the Sankey Diagram above, thermoelectric power generation is the single largest user of water, which is used mainly for cooling. Agriculture competes directly with the energy sector for water resources, putting the nation’s food security in competition with its energy sufficiency. The impact of changes in climate, shifting precipitation patterns, and greater frequency of extreme weather events has the potential to alter the availability of water resources. These effects, combined with population growth, could intensify existing competition for water resources and impact energy production and distribution. Furthermore, it is important to note that water and energy systems are also dependent on weather systems. Loosely speaking, warmer and drier weather conditions tend to increase demand for electricity while generally reducing the availability of water resource for hydropower and cooling purposes. Acknowledging the interactions between water and energy could help us understand how scarce conditions tend to occur together and cause compounding issues.
Citing the EIA Form 860 (EIA 2013a), the DOE report on water-energy nexus notes that over 90 percent of plants that are planned to retire require a water-intensive cooling process. Looking forward, only 45 percent of planned additions would not need cooling, meaning that the majority of new plants will still require water-intensive cooling. This complex interdependence of water and energy systems will have an impact on which energy technologies remain viable in the future. Obviously, changes in water resource availability would have the biggest influence on hydropower plants. The EIA states that, “In 2015, hydropower accounted for about 6% of total U.S. electricity generation and 46% of electricity generation from all renewables.” Beyond hydropower, the water-energy nexus may also affect the future of emerging technologies. The U.S. DOE report notes that while cost is the biggest hurdle today for Carbon Capture and Sequestration (CCS) technology, water usage may prove to be an equally large hurdle to overcome. Water consumption, measured in gallons per kWh of electricity generated, is estimated to double if CCS technology is adopted in its current form. The water-energy nexus is also expected to have an impact on oil and gas exploration. It is possible that technologies such as solar power that require low water usage may prove to be crucial in the near future.
The Importance of Strategic Planning
Situations like the recent drought in California will bring more and more scrutiny and prioritization of water usage. Proper strategic planning is going to be paramount in dealing with water shortages and competing priorities. A holistic modeling framework will be vital for such planning.
EPIS, LLC has been actively engaged in understanding the key challenges posed by the water-energy nexus. Recently, EPIS participated in the “Understanding the water-energy nexus: integrated water and power system modelling” workshop that was organized by the U.S. DOE and European Union’s Joint Research Centre (JRC). The workshop, which brought together academics, industry experts, regulators and model developers, focused on developing a framework for an integrated water-energy model that captures the critical factors in a tractable manner. AURORAxmp’s ability to explicitly model energy conversion capabilities was seen as a possible approach for easily representing the complexities of the water-energy nexus. While the event provided us with insights into various subtleties of this problem, one thing became clear: As water demand and prioritization becomes a larger issue, further research and development are needed.