Contemplating the Water-Energy Nexus

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.

Filed under: Water-Energy NexusTagged with: , , ,

Nuclear Retirements – The Unknown Future of Nuclear Power in the United States

Nuclear Plants Nearing Retirement

The U.S. currently has over 2 GW of nuclear capacity scheduled to be retired within the next four years.  The three planned closures are the 678 MW Pilgrim Nuclear Power Station, the 610 MW Oyster Creek Generating Station, and the 852 MW James A. Fitzpatrick Power Station.  The operators of these plants determined that while they had received extensions to their initial licenses, remaining operational was not economically viable.


Figure 1: U.S. Nuclear Capacity Source

As of August 2016, announced retirements looking even further into the future total above 7 GW with a few others being politically tenuous it further compounds the uncertainty within the nuclear fleet. Included in this 7 GW is the Fort Calhoun plant in Nebraska that was shut down by Omaha Public Power this year on October 24. However, this is just the tip of the iceberg when you consider the remaining plants and their need for future license extensions.

The Arduous Licensing Process

Nuclear plants are initially licensed for up to forty years by the U.S. Nuclear Regulatory Commission (NRC).  The operator may then apply for an additional twenty-year renewal; following that they can apply for a further extension of twenty more years.  All extensions are initiated by the operator and must be started sufficiently ahead of the expiration of their current license for the NRC to evaluate the safety and environmental impacts of an extension.  When operators apply more than five years prior to expiration, they can usually continue to operate while under this review.  If they don’t apply until within five years of the expiration, they may be forced to stop operating until they are approved.  The renewal process contains multiple cumbersome steps as shown in the diagram below.


Figure 2: License Renewal Process Source


Current Operating Nuclear Plants

The U.S. has 100 operating nuclear power plants; 45, or nearly half, have already operated through their forty-year operating license and are on their initial twenty-year extension.  Two of these are approaching the need to apply for their second extension: Peach Bottom in Pennsylvania and Surry in Virginia.


Figure 3: Active Nuclear Reactors  Source

To look at it another way, 81 plants have received their first renewal, an aging fleet in its own right.   But this means up to 30 GW of nuclear power has an unknown fate based on a not-yet-granted second license extension alone.  To date, no renewal applications have been permanently rejected but several plants have needed to make extensive improvements to gain approval.


Figure 4: Licensed Nuclear Plants Source

According to a recent Moody’s report, today’s low gas environment is making it difficult for some smaller nuclear units to survive competitively in the power market.  The future of gas will likely play a key role in the future of nuclear viability, as even without costly improvements some nuclear generators are struggling to stay afloat.

Nuclear Plants Coming Online

Interestingly, there are still a number of newly constructed plants currently in the process of becoming licensed that will bring over 5,000 MW online by 2020; these include plants in Tennessee, North Carolina and Georgia.  Additionally, there are up to six more applications for a combined 10 new reactors currently under review by the NRC.  A few companies are also looking into new designs that are smaller in scale, under 500 MW as opposed to +1,000 MW, that are more modular in design.  This new technology would give them the flexibility to be placed on more urban sites as needed to accommodate grid needs.

The Future Role of Nuclear Power

While a few sites are in the process of retiring their reactors, nuclear power is likely to be a part of the energy solution going forward for some time.  The minutiae of the policies may change, but one thing is certain: nuclear power will play a significant role in meeting U.S. electricity needs while curbing carbon pollution.  The U.S. Department of Energy reports the level of nuclear power generation for the country has been at 20 percent, the question is what hurdles will nuclear owners and operators have to overcome to maintain that level?

Filed under: Clean Power Plan, Nuclear Power, Renewable Portfolio StandardsTagged with: , , , ,