Energy and water consumption are closely connected. The Energy-Water nexus defines the relationship between energy and water to ensure the availability of both resources: Energy production consumes significant amounts of water; and equally, providing water demands energy. Moreover, power generation can impact water resources and increased electricity demand is projected in the coming years. In this scenario, the installation of carbon capture technologies in locations where the availability of water is limited must be studied, particularly in regions already suffering from water stress.
Previous IEAGHG studies (IEAGHG 2010/05, IEAGHG 2012/12, and IEAGHG 2018/04) have identified key factors that affect the Energy-Water-CCS nexus: location; the dependency of the costs and water consumption on the cooling system; and the post-combustion CO2 capture (PCC) system.Additionally, extracting water from a CO2 storage site can significantly increase the available volumetric space for CO2 storage which could benefit PCC in the power sector.
The conclusions drawn from these studies identified the need to assess the technical and economic impact of water consumption in power plants with and without CO2 capture systems in different locations, considering local regulations, ambient conditions, specific region-based power plants configurations, and water availability.
This study was conducted in two phases.The first phase provides:a literature review of regulations; assessments on water consumption in power plants with CO2 capture systems; techniques to reduce the water requirements in power plants with and without CO2 capture systems; and current practice on water extraction in the storage sites to increase the CO2 injection capacity.
This first phase focused on an assessment in a hypothetical location in the Netherlands, to develop a base case for IEAGHG techno-economic studies.In this phase, a methodology was developed to set the key techno-economic parameters and metrics for the second phase.
The second phase, assessed the entire CCS chain in four countries: South Africa; Australia; China; and India.The objectives were to explore the impact of the location on the power station configuration and performance, including options to reduce the water withdrawal in power plants with CCS.The second phase also evaluated the economic impact of water treatment on electricity cost; and identified cases where the re-use of water extracted from a storage site could be used as a water supply for power plants.
Findings from this study show that adding a CO2 capture system to the power plant may increase the water consumption of the whole facility. However, this increase can be mitigated through the implementation of different fitted strategies. Tailored early design of the Energy-Water-CCS nexus, that incorporates the cooling system and the potential reuse of water extracted from the storage site, is key. If more restrictive regulations are imposed on power plants that currently use evaporative freshwater cooling, the use of extracted and treated formation water in an integrated CCS-water loop could be a cost competitive alternative to retrofitting a power plant with an air cooling system. Additionally, the treatment of extracted water may provide a value in water-stressed regions, especially when considering the associated cost of water shortages.
This technical study covers one gap identified in previous reports: the integration of the Energy-Water-CCS nexus in different regions. We will continue monitoring updates on this area.