Climate change may reduce water available to cool power plants

Climate change and over-exploited river basins may leave developing countries in Asia, such as India and China, without enough water to cool power plants in the near future, according to a study. Thermal power plants (e.g. natural gas, nuclear, and coal) use water for cooling. Water scarcity may reduce the availability of thermal power capacity and impede the ability to reliably provide the energy services that motivate addition of coal capacity.

Changes in streamflow and water temperature due to climate change could exacerbate these constraints, as per the study published in the journal Energy and Environment Science. It found that existing and planned power plants that burn coal for energy could be vulnerable.

Cooling is critical to a plant's ability to operate - without it, machinery can overheat, causing a shutdown that could disrupt the flow of electricity to homes and businesses, and potentially also creating additional pollution. Electricity output will be constrained because of low water availability or high intake water temperatures – sometimes both.

Power plants are part of the problem

About 490 gigawatts of new coal-fired power generation is under planning or construction in the rapidly developing countries of Asia for operation before 2030, of which 110 gigawatts is in India. This planned capacity adds 30% more to the existing coal-fired generation capacity, and will engender substantial water requirements and amounts of pollutants that can worsen global climate change and regional air pollution. 

Past studies on the thermal electricity-water nexus have not accounted for this new capacity, and use coarse spatial and temporal resolutions in the assessment of long-term power system reliability. This study analyses databases of existing and planned coal-fired power plants, and combines it withhigh-resolution hydro-climatic simulations to evaluate the possible strain on water supplies throughout the region.

A model is developed to quantify water constraints on coal-fired power plants Asia’s developing countries, which uses different scenarios of future climate change, cooling system choice, and capacity expansion.

Diverse climate scenarios are used -- for increases in global temperature of 1.5, 2 and 3 degrees Celsius above pre-industrial levels. Different cooling systems and potential use of post-combustion CO₂ capture equipment, and the water that might be needed to run them were considered.

Future climate change and capacity expansion decrease the annual usable capacity factor (UF) of coal power generation in Mongolia, Southeast Asia, and parts of India and China. Under near-term mitigation scenarios with high penetrations of CO₂ capture technology, the regional average water withdrawal intensity of coal power generation is 50–80% higher than current conditions.

The way forward

Some existing regional regulations seek to address the environmental impacts of current and future coal-fired power plants by banning the use of groundwater for cooling, limiting the construction of new power plants, and mandating the use of wet cooling towers.

With careful siting, the increased water withdrawal intensity does not necessarily constrain future electricity production on annual or monthly time scales. The system will still be more unreliable as it increases the probability of low usable capacity factor at daily time scale.

Growing populations and economies create more demand for electricity and stress on water resources. Planning for future thermal generation capacity requires reliable water resources. The study investigated the impacts of climate change, the addition and retirement of coal-fired power plants under different age-based and climate change mitigation scenarios, and different cooling system choices on the usable capacity and usable capacity factor of coal power production in developing countries in Asia.

The main findings are:

• If the use of dry cooling remains at present-day levels, the planned expansion of coal-fired power plants in developing countries in Asia will increase the regional usable capacity, which increases the amount of electricity that can be supplied. But this capacity expansion also decreases the usable capacity factor, which implies more severe water constraints on electricity generation. Wide deployment of carbon capture and storage for achieving the 1.5°C and 2°C climate goals have small impacts on regional annual or monthly mean usable capacity factor, but leads to higher probability of low regional average usable capacity on the daily time scale.
• Climate change will lead to slight increases and decreases in streamflow that also affect usable capacity and usable capacity factor, but the impacts are smaller than capacity expansion.
• Location choices of individual coal-fired power plants can affect the usable capacity factor at aggregated spatial levels, because of the uneven distribution of local streamflow and the competition between the power plants for local water.
• At the administrative-unit level (provinces for China, states for India, and countries elsewhere), regions that expect the most negative impact from climate change and capacity expansion are Mongolia (20–74% decreases in usable capacity factor), central China (up to 74%), Southeast Asia (up to 65% decreases), central India (up to 40% decreases), southeastern China (up to 20% decreases), and southern India (11–14% decreases).
• At the power-grid level (covering 1–7 administrative units), the changes in usable capacity factor tend to be less negative than the changes at individual administrative units within the grid-region, because local positive and negative changes cancel out each other.
• Wider deployment of dry cooling can considerably increase the usable capacity and usable capacity factor within the study region. But dry cooling has a high energy penalty in South Asia, which can challenge its economic feasibility and counteract future efforts to reduce CO₂ emissions.

The full report can be accessed here.