New research reveals carbon-water trade-offs for cooling technologies in the global thermal power industry

Climate change and water scarcity are two of the world’s major challenges. As the world’s largest anthropogenic source of carbon dioxide emissions, the thermal power industry is an important cause of climate change (human activities affect the natural environment); On the other hand, changes in the hydrological cycle under climate change (such as scarcity of water resources and rising water temperature) will seriously restrict thermal power generation and threaten energy security (natural environment feedback to human society).

Schematic diagram of the water-carbon trade-off relationship between the power sector from the perspective of human-ground coupling (Photo courtesy of the research group)

Recently, the journal Nature Water published the latest results of the paper by Qin Li, a researcher at the School of Environmental Science and Engineering of Peking University, as the first author and co-corresponding author of the paper.

Qin Li told China Science News that this study focuses on the deployment of plant-level cooling technology and the temporal and spatial dynamic evolution of its carbon-water trade-off law under climate change, reveals the two-way coupling mechanism and spatial distribution characteristics of the trade-off between water resources and carbon emissions on a global scale, explores the flexible application potential of unconventional water sources and carbon sequestration technologies at the global power plant scale, and provides scientific basis for power system planning and energy security under the goal of carbon neutrality.

The transformation of cooling technology in the energy industry (such as the use of dry cooling technology) can alleviate the water pressure faced by the thermal power industry, but at the same time, there are disadvantages such as low heat exchange efficiency and high energy consumption of fans, and its power generation efficiency and carbon emissions will further increase non-linearly with climate change.

At the same time, unconventional water use and CO2 capture technologies may effectively mitigate the carbon-water trade-offs such as dry cooling.

Therefore, from the perspective of human-ground coupling, the integration of cooling technology transformation, unconventional water utilization, and carbon sequestration technologies to identify the carbon-water two-way coupling mechanism of the power sector is one of the important scientific bottlenecks and practical problems faced by the power sector under the dual challenges of climate change and water shortage.

Based on global power plant datasets, meteorological and hydrological simulations, unconventional water sources and carbon sequestration potential estimation, the research team built a comprehensive evaluation framework for the carbon-water trade-off mechanism of the power sector with global high-precision cooling technology-unconventional water resources-carbon sequestration technology, which provides a scientific basis for the power industry to cope with the dual challenges of climate change and water scarcity from the perspective of human-land coupling.

It is found that there is a clear carbon-water trade-off between dry cooling technologies for major fuel types in the world. In terms of spatial distribution, the power plants with large reductions in water withdrawals are concentrated in northern China, western United States and southern Africa, while units with large increases in CO2 emissions are concentrated in India and northern China. An increase in ambient temperature will result in higher back pressure, and the efficiency loss of dry cooling units will increase nonlinearly. Under the RCP6.0 and RCP8.5 scenarios, the ambient temperature and efficiency loss will continue to increase, and the efficiency loss will increase faster than the ambient temperature.

Through the coupling assessment of cooling technology, unconventional water resources and carbon sequestration potential, it is found that increasing the proportion of wastewater reuse can increase the thermal power generation capacity of unconventional water to meet cooling water demand from 25% to 85%, and increase the unconventional water collection distance from 10km to 50km, and increase the cooling water satisfaction rate from 15% to 42%. Therefore, actively developing unconventional water recycling and carbon sequestration technologies will provide an opportunity to address the carbon-water trade-off in the power sector.

At the same time, the study also finds that for regions in eastern China, India and Thailand, where the coupling of dry cooling technology-unconventional water resources-carbon sequestration technology is difficult to cope with the carbon-water trade-off of their power sector, strategies such as renewable energy transformation are urgently needed to solve the carbon-water trade-off dilemma, and the priority layout of low-carbon transformation of the power sector under the carbon neutrality goal is proposed from the perspective of water resources.

The co-corresponding author of the paper is Assistant Professor Hong Chaopeng of Shenzhen International Graduate School of Tsinghua University. Other collaborators include well-known experts in related fields from multiple research institutions.

The research work was supported by the National Natural Science Foundation of China and other projects. (Source: Cui Xueqin, China Science News)

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