Parametric sensitivity study of submarine power cable design for marine renewable energy applications

An increasing use of submarine power cables is found in dynamic applications such as floating wind, floating wave and tidal generation technologies. These applications substantially differ from common applications, such as floating oil and gas installations in that they are more dynamic. Power cables that cross the water column, so-called umbilicals will be exposed to considerable extreme and fatigue loads mainly induced by the motion of the device, incident waves and tidal current. The actual loading regimes of dynamic submarine power cables in operation are not well understood for marine renewable energy (MRE) applications due to a lack of field experience. The cable design has to consider a combination of cable geometry, hydrodynamic parameters, suitable layout configuration, suitable ancillary systems (e.g. bend stiffeners) in relation to the environmental site conditions. This paper evaluates the influence of the environmental conditions and the cable design parameters on the mechanical loads and potential failure modes of a dynamic submarine power cable attached to a dynamic floating body in form of a generic point absorber. One notable result is the large effect of the tidal direction, even in relatively moderate flow conditions. The full range of tidal flow conditions should be considered in the power cable design to ensure that the cable MBR is not exceeded in any conditions. The shown configurations also give some insight into the possible variations of the geometric cable configuration. A well balanced S-curve shape yields some of the best results and achieves a good load distribution along the cable and the transition points, whilst avoiding cable compression. The design challenge for the cable configuration is to maintain the S-shape for as many environmental and device response modes as possible in order to achieve high reliability. This paper will be useful for cable, device and site developers of floating MRE to inform the selection of the most suitable cable design.