Innovative Energy Storage Concept for Saipem Offshore Wind2Sub™ Application

Abstract

Reducing CO2 emissions is becoming one of the core targets for countries after the Paris agreement, which sets out a global framework to avoid dangerous climate change by limiting global warming to below 2°C and pursuing efforts to limit it to 1.5°C. To meet this objective also oil and gas operators have started to engage in an important effort to reduce the CO2 emissions in their plants and facilities. From this perspective Saipem developed its Wind2Sub, a Wind Power for Long Subsea Tie-Back (LSSTB) concept, where its own pendular floating foundation solution, namely Hexafloat, can host a wind turbine generator (WTG), all the utilities needed for subsea field development and operation (power distribution, chemical storage and injection, control system) and a back-up energy system to compensate the intermittent production due to wind persistence, currently a diesel generator (DG). The present paper will explore new solutions to ensure the continuity of the energy supply from Saipem Wins2Sub, based on green technologies. This may be done by collecting the generated surplus energy from a renewable energy system, in this case from WTG to a topside or subsea power storage. By adopting an Energy Storage System (ESS), it will be possible to use this energy when production from wind is low or null. This concept will replace the diesel generators, or any carbon fuel, so that the whole system will become green self-sustaining, as an energy island, without CO2 emissions. The activities performed during the concept development are articulated through the following steps: a selection of two typical oil field scenarios where Wind2Sub solution can be applicable; screening of the current technologies to store energy and a selection of those viable to the two selected scenarios; wind conditions and WTG power analysis with estimation of the amount of the energy to be stored; preliminary design of the ESS; preliminary cost estimation. The study was carried out by using a digital tool developed by Moss Maritime in the context of a Proof of Concept based on Floating energy storage. The tool allows to evaluate the feasibility of a solution through modellization of different renewable energy scenarios, demand profiles, simulation of operation, pre-sizing of the systems and cost estimation (LCOE, LCOS, LCOH). The ESS combined with Saipem Wind2Sub will be described more thoroughly in the present paper through the explanation of the results achieved within the case studies.