Study projects thermoelectric power in Europe and US vulnerable to climate change due to lower summer river flows and higher river water temperatures
3 June 2012
|Projected changes in summer mean usable capacity of power plants in the US and Europe for the SRES A2 emissions scenario for the 2040s (2031–2060) relative to the control period (1971–2000). Source: van Vliet et al. Click to enlarge.|
A study published in Nature Climate Change suggests that thermoelectric power plants (i.e., nuclear and fossil-fueled generating units) in Europe and the United States are vulnerable to climate change due to the combined impacts of lower summer river flows and higher river water temperatures.
In the US and Europe, at present 91% and 78% of the total electricity is produced by thermoelectric power plants, which directly depend on the availability and temperature of water resources for cooling. An international team of researchers projected a summer average decrease in capacity of power plants of 6.3—19% in Europe and 4.4—16% in the United States depending on cooling system type and climate scenario for 2031—2060. In addition, probabilities of extreme (>90%) reductions in thermoelectric power production will on average increase by a factor of three.
Compared to other water use sectors (e.g. industry, agriculture, domestic use), the thermoelectric power sector is one of the largest water users in the US (at 40%) and in Europe (43% of total surface water withdrawals). While much of this water is recycled, the power plants rely on consistent volumes of water, at a particular temperature, to prevent overheating of power plants. Reduced water availability and higher water temperatures—caused by increasing ambient air temperatures—are therefore significant issues for electricity supply.
Higher water temperatures and reduced river flows in Europe and the United States in recent years have resulted in reduced production—or temporary shutdown—of several thermoelectric power plants.
The research was undertaken by an international team of scientists from the Earth System Science and Climate Change Group, Wageningen University and Research Centre; The Netherlands, The Department of Civil and Environmental Engineering, University of Washington, Seattle, USA; Forschungszentrum Jülich, Institute of Energy and Climate Research–System Analyses and Technology Evaluation, Jülich, Germany; and the International Institute for Applied Systems Analysis, Laxenburg, Austria.
Using a physically based hydrological and water temperature modeling framework, the team produced a multi-model ensemble of daily river flow and water temperature projections for Europe and the US over the 21st century. It then produced daily simulations of river flow and water temperature for the periods 1971–2000 (control), 2031–2060 (2040s) and 2071–2100 (2080s) by forcing the coupled hydrological–water temperature model with bias-corrected global climate model (GCM) outputs for both the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A2 and B1 global emissions scenarios.
The A2 scenario considers a world of fragmented and slow technological change, whereas the B1 scenario assumes environmental sustainability and a much more rapid introduction of renewables. Both SRES A2 and B1 were selected, because they represent contrasting storylines and indicate the largest range from the four IPCC SRES main emissions scenarios.
To quantify climate change impacts on usable capacity of existing thermoelectric power plants, the researchers used the resulting daily water temperature and river flow projections in combination with power-plant-specific data of cooling system, efficiency and environmental restrictions for 61 power plants in the US and 35 in Europe, including both nuclear and coal-fired power plants with different cooling systems.
Among their findings were:
For 76% of the power plants with once-through or combination cooling systems and 41% of the power plants with recirculation systems, electricity production potential will be reduced significantly as a result of the projected increases in daily water temperature and decreases in summer flows for the 2040s.
The summer average usable capacity of power plants with once-through or combination cooling systems is projected to decrease by 12–16% (US) and 13–19% (Europe) for the 2040s (for B1–A2 SRES emissions scenario).
The occurrence of periods with large reductions in usable capacity will increase in the 2040s.
For recirculation (tower) cooling systems, the decrease in usable capacity during summer is much lower, but non-negligible (on average 6.3–8.0% for power plants in Europe and 4.4–5.9% in the US).
An additional problem for the plants using once-through cooling is that by design, water pumped water from rivers, lakes, or the sea to cool the turbine condensers is then returned to its source, often at temperatures significantly higher than when the water entered the plant. This causes downstream thermal pollution affecting, for example, life cycles of aquatic organisms. Both the US and Europe have strict environmental standards with regard to the volume of water withdrawn and the temperature of the water discharged from power plants. Thus warm periods coupled with low river flows can lead to conflicts between environmental objectives and energy production.
Owing to the smaller adaptive capacity of the thermoelectric sector for the SRES A2 scenario, the vulnerability to climate change will be substantially higher for the SRES A2 when compared with the B1 scenario. Although replacement of once-through by recirculation systems reduces freshwater withdrawal, water consumption increases (owing to evaporative losses) and could therefore contribute to higher water scarcity. Dry cooling systems or non-freshwater sources for cooling are possible alternatives but may be limited by locally available resources and have costs and performance disadvantages.
A switch to new gas-fired power plants with higher efficiencies (∼58%) could also reduce the vulnerability because of smaller water demands when compared with coal- and nuclear-fueled stations (with mean efficiencies of ∼46% and ∼34%). Considering the projected decreases in cooling-water availability during summer in combination with the long design life of power plant infrastructure, adaptation options should be included in today’s planning and strategies to meet the growing electricity demand in the twenty-first century. In this respect, the electricity sector is on the receiving (impacts) as well as producing (emissions) side of the climate change equation.—van Vliet
The study was supported by the European Commission’s FP6 WATCH project and through the FP7 ECLISE project.
Michelle T. H. van Vliet, John R. Yearsley, Fulco Ludwig, Stefan Vögele, Dennis P. Lettenmaier and Pavel Kabat (2012) Vulnerability of US and European electricity supply to climate change. Nature Climate Change doi: 10.1038/NCLIMATE1546
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