Compressed air energy storage for clean offshore energy supply

The primary objective of this work is to evaluate feasible process configurations based on compressed air energy storage system (CAES) in order to reduce the emissions of offshore oil and gas extraction facilities. The main aim is to remove the need for the traditional shared-load gas turbine operation on the platform, which currently represents a significant source of CO2 and fuel consumption. Improving the energy management of offshore installations opens up significant opportunities concerning both cost savings and reduction of the environmental impact. A specific case study, represented by Edvard Grieg and Ivar Aasen installations, was used to model the components of the system. The model, while tailored for some specific parameters, can be easily adapted to a variety of different situations, and therefore aims to represent a starting point for further optimization work and for the analysis of different site conditions. The models of the various components were defined in MATLAB and EXCEL, and were given particular attention to their off-design operation, in accordance to energy requirements and constrains of the case study. The key investigated parameters were the size of the wind farm, the depth of the sea (which directly affects the sizing of the air storage) and the possibility to recover waste heat from the GT to preheat the air as it is extracted from the underwater storage. The results show that the integration of a wind farm alone will not allow to remove the need for the 2nd GT, but would provide the system with a significant reduction of CO2 emissions, ranging between 14% and 40%, depending on the size of the offshore wind park. The introduction of the CAES system removes the need for the 2nd GT and improves the achieved reduction even further, especially with the use of an air preheater (it is possible to achieve a 47% reduction with the best configuration). From an energy point of view, the system is always attractive. On the other hand, when considering the physical space required by the storage, it seems that the available sea depth might be a stringent limitation to an effective applicability, requiring up to 475 vessels in the case study depth of 110 meters. The study of higher depths (400 and more meters) resuls in a drastic reduction of required vessels, making these sites more attractive and promising for the CAES technology