Start-up FLASC has developed a hydro-pneumatic energy storage system for offshore wind turbines. The system is safe, reliable and built on the combination of existing technologies. Thanks to an innovative pre-charging process, the system can also be deployed in shallow water. Co-founder and CEO Daniel Buhagiar is looking to connect with potential partners.

For which problem have you found a solution?

“Balancing electricity supply and demand is one of the greatest challenges in offshore wind. In the offshore segment, batteries are not very suitable for this task due to safety and reliability issues. There are other offshore energy storage systems under development, but these typically rely on the external hydrostatic pressure. Consequently, these storage systems tend to be more viable in deep waters, say below 500 m, but where there is limited offshore wind deployment. We address this challenge.”

What is the core of your innovation?

“We developed a Hydro-Pneumatic Energy Storage (HPES) technology that can be co-located with fixed-bottom and upcoming floating wind farms. The patented technology comprises a closed dual-chamber system containing a pre-charged gas, which can be compressed air or nitrogen. The technology can be integrated within a variety of embodiments: from completely subsea designs, to integration in a monopile, or even within a wind turbine floater. The system is charged by supplying the electricity to a hydraulic pump. This pushes external seawater into the closed chambers, compressing the internal gas. This principle is called a liquid piston. During discharging, energy is recovered by allowing the internal compressed gas to push the seawater out through a hydraulic turbine. The system operates at a pressure range of 100 to 200 bar.

What is so ground-breaking about the FLASC HPES technology?

“There are two key innovations. First, the closed pre-charged concept. This allows us to install this system in shallow waters, roughly from 30 up to 400 metres, while retaining a high energy density. Secondly, the use of the ocean as a natural heatsink. Systems using compressed gas to store energy suffer from a low thermal efficiency, due to the gas heating up during compression. We have addressed this challenge by immersing the system in water. The surrounding water works as an excellent passive heatsink. It quickly absorbs heat during compression and restores it during expansion, resulting in a highly efficient way in an almost constant temperature. It is a simple and elegant solution. In fact, the judges cited these reasons when we were awarded the Best Innovation Award at Offshore Energy 2020 last October.”

What are the benefits of your solution?

“The key benefit is to allow increased offshore renewable energy asset utilisation. Our system is best suited to address intermittency on the seconds up to the hourly timescales. It is most cost-effective when deployed in large installations having more than 10 MWh of storage. The technology is safe and reliable, resulting from the use of non-hazardous materials and processes, along with the use of proven off-the-shelf components extensively used in hydropower and offshore oil & gas. The system can be designed for lifetimes exceeding 25 years.”

How far are you now?

“The concept originated in 2015 at the University of Malta that is currently also working on a TRL 7 system to be deployed in the coming years. FLASC was established in 2019 as spin-off company in response to growing commercial interest. The Netherlands was selected as a strategic base because of the proximity to key markets, supply chains and knowledge centres, as well as the exciting start-up climate around offshore renewables.

What are your challenges?

“The high capital costs and infrastructure required to upscale the technology is our main challenge. However, we are well positioned to collaborate with established companies with a proven track record to deliver the full scope of large-scale FLASC HPES installations. In fact, we have seen growing interest from large companies.”

What are your next steps?

“Beyond short-term technology development milestones, we are actively working to secure a first commercial project to be deployed in the coming years. The next step will be industrialising the technology towards full-scale commercial deployment. Therefore, we signed a collaboration agreement with Subsea 7 in June. We are also looking at different applications for our technology, from decarbonisation initiatives in the offshore oil and gas sector to large scale deployment of offshore green hydrogen production. We are currently engaging in feasibility studies with key partners across the green hydrogen value chain. We are always on the look-out for potential partners towards pilot projects, new collaborations, or early-stage feasibility studies.”

What is the added value of TKI Wind op Zee?

“Coming to the Netherlands from Malta, we did not really have a well-established network. TKI Wind op Zee supported us with making new contacts, particularly through their match-making events. Within a few months of setting up in the Netherlands, we had already joined a consortium towards our first Dutch subsidy project. I don't think we could have done it without their help.”


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