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System architecture of Subsea Energy Storage for offshore renewables

Alternative title: Systemarkitektur for en energilagrings-enhet under vann

Awarded: NOK 1.8 mill.

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Project Period:

2021 - 2024

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An industrial PhD project is proposed to see how we can utilize the experience from subsea oil & gas towards the renewables energy market and solve some of the challenges with introducing renewable energy sources at a large scale. The objective is to study the requirements for energy storage when switching from non-renewables, such as fossil fuels, towards renewable energy sources. In addition the project will analyze a proposed solution for subsea energy storage and make sure that it fulfills the requirements for the energy sector. The shift towards renewables introduces a lot of opportunities as well as challenges that needs to be solved. Wind power plants are depending on wind to generate electricity and solar power plants are depending on the sun and the outputs from these energy sources will vary. Today the variability is not a major problem because the portion of renewable energy sources is relatively small and there are other non-variable energy plants such as coal and gas that can fill the gap. However when we increase the amount of renewables and decrease the amount of non-renewables it also means that there is not enough energy to fill the gaps from the variable renewables. To mitigate this it is possible to introduce energy storage so that when there is an abundance of energy such as on a windy day excess energy can be stored and used during periods with no wind. Energy storage in itself is not new. Perhaps the best example of energy storage in Norway is the water reservoirs in the mountains. But there are many different storage methods including batteries similar to those existing in electric cars. Every storage method has its advantages and disadvantages. It is the aim of this project to define a system architecture that best fits the need for energy storage in the future.


Many commitments and policies have been defined in order to cut CO2 emissions. For example, the European commission has stated that the EU will be carbon neutral by 2050. In order to achieve this, the renewables share of the energy portfolio needs to be increased substantially. However, one of the main drawbacks with renewables such as wind and solar power is its intermittency. In order to balance this intermittency the demand for both long term and short term energy storage solutions will increase significantly. Subsea 7 has through its technology development program developed and patented a concept for subsea energy storage. The work is based on the long experience within subsea engineering at Subsea 7 and aims to increase the utilization of the ocean resources locally and globally. Further research is needed to understand the requirements for energy storage in the energy market from 2030 and onward. First of all, an understanding of what the capacity need for power balancing and energy storage is in the period 2030-2050 is needed. Second, can the proposed energy storage system balance the variability in power output from renewables in the period 2030-2050 enough to meet the demands from the grid suppliers? These questions will be answered by a literature study and development of a model to predict the performance of an novel subsea energy storage solution. The model can be tested with various energy sources and used for hypothesis testing defined during the initial stages of the PhD study.

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