Publication Overview
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. Further investigation also needs to encompass the impact of local regulations, ambient conditions, specific region-based power plants configurations, and water availability.
This current study was conducted in two phases. Phase 1 developed a hypothetical base case scenario of power plants with and without a PCC system in The Netherlands, assuming both on and offshore storage, and with and without treatment of the water extracted from the storage site for its reuse in the power plant. Phase 2 was based on four hypothetical PCC systems in South Africa, Australia, China and India.
Publication Summary
- 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.
- The results from this study confirm 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, such as using alternative water supply, recycling of water, or using alternative cooling techniques
- The outcomes from this study confirm that the selection of the cooling system has a strong impact on the water consumption. For example, evaporative natural draught cooling has a noticeably higher percentage increase in water withdrawal and consumption compared with the once-through seawater cooling systems.
- 16 Water-Energy-CCS nexus cases were modelled for a hypothetical location in the Netherlands. LCOE increases by 2-3 €/MWh and 3-6 €/MWh for onshore and offshore storage scenarios respectively. That includes CO₂ storage, water extraction, treatment, transport and disposal.
- Results show that, if water extraction is necessary for storage purposes, its treatment and beneficial reuse may present the most economic option, compared to the direct disposal in the onshore storage scenario
- In the second phase of this study, power plants in South Africa, Australia, China, and India were modelled. The results of this work show that the location of the power plant (with and without CO₂ capture system) influences the water availability, consumption and costs, due to the regulations, feedstock, ambient conditions, and cooling system.
- The lowest water withdrawal and consumption rates are evident from the case in China due to the ambient conditions, such as a lower temperature. In this scenario, building an air-cooled USCPC (Ultra Super-Critical Power Coal plant) is 30% cheaper, while this option is 20% more expensive in Australia and South Africa, compared to the USCPC base case in The Netherlands.
- Adding a CO₂ capture system at the power station, as well as ZLD (Zero Liquid Discharge) at the power stations in China, India and South Africa, increases the specific capital requirement by 52% – 60%. The LCOE increases by 44% – 55%, which equates to a LCOE of 62-91 €/MWh, depending on the location.
- CO₂ avoidance cost for the USCPC with capture is 36 – 51 €/t CO₂ in the CCS Base Case Scenario and increases to 41 – 58 €/t CO₂ in the Energy-Water-CCS nexus Scenario, with the Chinese power station having the lowest avoidance cost and the South African power station having the highest.
- Water extraction and treatment add a comparatively small capital cost to the examined CCS cases (5% increase), but the LCOE can increase by 11 – 12%.
- The treatment of extracted water may provide a value in water-stressed regions, especially when considering the associated cost of water shortages. In this study, the cost of product water, accounting for brine treatment and disposal costs, was found to be comparable to local water tariffs in the four countries, ranging from 1.12 €/m3 to 2.43 €/m3. When water extraction and transport costs are also included, product water cost exceed local water supply charges.
