Reduced Cost of Electrification - SP3

Research Manager
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This subproject develops new technology for electrifying offshore installations. We are investigating a novel approach using wet design of high-voltage offshore cables in combination with subsea compensation units to enable long distance AC power transmission. This gives lighter cables without the need for a metallic barrier to prevent water ingress, and reduced costs for production and installation of the cable.

Main objective:

The gas turbines used for offshore power production today emit large quantities of greenhouse gases (GHG). Electrification from shore may drastically reduce these emissions. While the technology for electrification is already available, it is not often used as the price of electrification is high. The emphasis of SP3 is on reducing costs without sacrificing system reliability for the energy system and key components.

  1. Identify/develop cost-efficient reliable power components for offshore/subsea power distribution
  2. Test components/insulation systems based on models of typical load patterns
  3. Develop models for estimation of global GHG emission reduction due to electrification

Results 2020

  • Improved and documented the offshore grid layout optimisation model ( PowerGIM) and completed preliminary analyses with the European power system expansion optimisation model EMPIRE.
  • A new methodology for water tree analysis was established based on Scanning electron Microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX). In addition, FIB-milling was used to exclude contaminations at the surface, detecting ions tens of microns into the sample. This will be an important tool in future research on water tree inception and growth, which is central in future development of wet-design cables.
  • Performed and reported a review of tools to simulate energy systems and of approaches to quantify the GHG emissions associated with the utilisation of power from shore. Carried out a preliminary identification of relevant scenarios to assess offshore electrification on the Norwegian Continental Shelf.

Impact and innovations

  • The main goal of the material characterisation of aged wet-design cables (ongoing in 2021) is to link chemical and mechanical properties of the XLPE cable insulation with inception and growth of water trees. A methodology including examinations of the surface of the spiralized slices soaked in de-ionized water by SEM combined with EDX has been established and is promising for the identification of impurities in the vicinity of vented water trees.
  • The analyses of tools and methods to quantify GHG emissions gives a sound basis to measure the actual environmental impact of electrification.
SEM picture (x1500) of a section located at the interface between the insulation and the semiconductorafter FIB-milling (ca 50 μm depth).

Results 2019

This SP develops new technology for electrifying offshore installations. Emphasis is on reducing costs without sacrificing system reliability for the energy system and key components. A novel approach using wet design of high-voltage offshore cables in combination with subsea compensation units to enable long distance AC power transmission will be investigated. This gives lighter cables without the need for a metallic barrier to prevent water ingress, and reduced costs for production and laying the cable.

Main objective

The gas turbines utilized for offshore power production today emit large quantities of greenhouse gases (GHG). Electrification from shore may drastically reduce these emissions. While the technology for electrification is already available, it is not often used as the price of electrification is high. The emphasis of SP3 is on reducing costs without sacrificing system reliability for the energy system and key components. The main objectives are to:

  1. Identify/develop cost-efficient reliable power components for offshore/subsea power distribution
  2. Test components/insulation systems based on models of typical load patterns
  3. Develop models for estimation of GHG emission reduction due to electrification

Main results

  • Completed preliminary study identifying optimal offshore grid layout with full electrification of the NCS
  • Dynamic Mechanical Analysis (DMA), Thermo-Mechanical Analysis (TMA), Differential Scanning Calorimetry (DSC) experiments have been performed on samples taken from three HV 145 kV XLPE land cables. Two of these cables were operated under wet conditions until they suffered breakdown due to water treeing. The third cable has never been in service and is used as a reference in this study.
  • Review of existing technology was performed, important knowledge gaps like wet mate connectors, cooling of subsea transformers, turrets for FPSOs, and voltage limitations on floating installations due to dynamical vibrations have been identified.
  • Initial overview of current tools and methods to quantify GHG emissions associated to power from shore and definition of gaps to address.

Impact and innovations

  • The main goal of the material characterization of aged wet-design cables (ongoing in 2020) is to link chemical and mechanical properties of the XLPE cable insulation with inception and growth of water trees. Preliminary results show differences in thermo mechanical properties between cables close to the insulation where the water trees grow.
  • The analyses of tools and methods to quantify GHG emissions gives a sound basis to measure the actual environmental impact of electrification.
Example of a water tree growing from the conductor screen in a 145 kV land cable without an outer water barrier that failed after 18 years in service. Such trees grow in all polymeric materials under the combined action of an electrical field, moisture and ions. On a microscopic level they are essentially a network of water filled sub-micro voids and channels growing along the electrical field direction (radial).