A study on the potential of cryogenic cooling and cutting technique in reducing the decommissioning cost of offshore monopiles

Abstract

This paper presents a feasibility study of the Cryogenic Cooling and Cutting System (CCCS), an embrittlement-based technique for offshore wind monopile foundations. The CCCS employs cryogenic treatment of the monopile wall surface to significantly reduce its impact energy absorption capability significantly, aiming to achieve shorter overall cutting time than conventional cutting techniques. Through numerical analysis, the performance of CCCS is assessed and compared with the Abrasive Water Jet (AWJ) technique, revealing that CCCS offers up to 46.8 times faster cutting speeds and reduces cutting times by 87.1 % – 97.9 % across various monopile diameters and wall thicknesses. These improvements indicate the potential for substantial reductions in the cost and emissions associated with Offshore Wind Farm (OWF) decommissioning. Specifically, the application of CCCS could reduce the total foundation removal operation time by 28 %, resulting in 23 % savings in vessel leasing costs for a real-world OWF decommissioning project. Our findings suggest that the proposed CCCS technique enhances cutting efficiency and contributes significantly to the economic and environmental sustainability of OWF decommissioning. This study aims to demonstrate the CCCS technique’s unique advantages over conventional methods, such as AWJ, by significantly reducing both cutting times and environmental impact, thereby enhancing the sustainability and cost-effectiveness of offshore wind farm decommissioning.