FlexH2: How offshore wind will be directed more intelligently to the right place in the future
The perfect integration of offshore wind in a nation’s energy system is more than just connecting supply and demand. Especially if you want to choose whether electricity goes directly to a renewable hydrogen plant or into the electricity grid. A solution is FlexH2: a unique idea developed into the world’s first pilot installation. It was commissioned on 7 May on the campus of Eindhoven University of Technology.
The perfect integration of offshore wind in a nation’s energy system is more than just connecting supply and demand. Especially if you want to be able to choose whether electricity goes straight to a renewable hydrogen plant or into the electricity grid. A solution is FlexH2: a unique idea developed into the world’s first pilot installation. It was commissioned on 7 May on the campus of Eindhoven University of Technology.
To the untrained eye, the FlexH2 test unit looks like a jumble of cabinets, cables and meters – at first glance not very different from a generic computer room. But this is a possible future for delivering offshore wind energy. Designing and building the test unit took four years. First, an explanation of how offshore wind works without — and with — FlexH2.
Offshore wind today Just like at home, offshore wind farms also have a kind of power strip to which individual wind turbines are connected. This substation — a substantial platform on piles fitted with equipment and electronics — collects the power at alternating current (AC), converts it to high-voltage AC, and sends it via a cable to an onshore substation.
That onshore substation feeds the electricity into the power grid. Electronics ensure that the wind turbines remain synchronised with the power grid onshore. If a wind farm is located more than 80 kilometres (50 miles) offshore, the electricity must also be converted en route from alternating current (AC) to direct current (DC) and back again to alternating current (AC), to connect to the high-voltage grid. These conversions are needed to ensure a stable power transmission, and it requires a larger and more expensive offshore substation.
Dutch wind farms and hydrogen The ten existing Dutch offshore wind farms are located between 18 and 60 kilometres (11 and 37 miles) from the coast. These include four wind farms developed by Shell and partners: NoordzeeWind, Borssele III & IV (Blauwwind), Hollandse Kust Noord V (CrossWind) and — still under construction — Hollandse Kust West VI (Ecowende)
Can the Dutch grid work differently? The FlexH2 solution is an innovation that can be deployed worldwide. In the Netherlands, however, things currently work slightly differently, as there are no direct power cables between wind farms and end users. As a result, electricity from the Hollandse Kust Noord wind farm (CrossWind) is first fed into the public electricity grid before reaching Shell Holland Hydrogen 1. By law, TenneT is responsible for the grid on behalf of the Dutch state. Only for the final connection between the national grid and Holland Hydrogen 1 has Shell installed a dedicated cable, in cooperation with TenneT.
"If the FlexH2 test unit demonstrates that this can be done differently, it would give the Dutch government more flexibility for future power generation locations," says Yin Sun, a Shell engineer closely involved with the FlexH2 project. "This could be particularly useful in cases of extreme grid congestion, where a complete freeze on new or heavier grid connections must be imposed". As is the case in much of the province of Utrecht from 1 July this year.
Robust pilot installation Work on the FlexH2 pilot installation took four years and involved partners from industry and the Dutch academic research community. “We started on an idea within Shell New Energy Research and Technology, formerly known as NERT back in 2019. As the coordinator of the FlexH2 project, we need to share the vision with all the project partners and further proof the feasibility of the FlexH2 concept with solid engineering design and electrical calculations,” Sun explains.
“The discussions with experts from the OEMs — the manufacturers of the original components of the concept — were therefore essential. Together, we had to develop an idea into a working down-scaled laboratory set-up in which all the individual elements could operate together.”
Chicken and egg problem Defining what individual sub-system should perform under the FlexH2 concept is also proven to be a challenge, often referred to as the “chicken and egg” problem. For example, wind turbine behaviour under various conditions needed to be designed and engineered parallel with co-creations of other parts of the system. In short: things had to be produced without any existing specifications, apart from an idea that was still in the making. Normally, manufacturers work with specifications and requirements already set by the energy developer.
“The result is a co-created technical solution, and we show the outstanding technical performance with the help of a robust pilot demo system”, Sun says. This system is now operational at Differ /Eindhoven University of Technology and intended for researchers only, due to medium voltage safety regulation. The final test results of this FlexH2 Demo unit are expected towards the end of the year, and will serve as a source of innovation for the entire energy sector.
All of them supply electricity to the grid, but CrossWind will partly produce power for Western Europe’s first large-scale renewable hydrogen plant. This facility, Shell Holland Hydrogen 1 (HH1), is still under construction near Rotterdam and is expected to becommissioned step by step towards the end of 2026, and into 2027.
HH1 also has a small substation that converts the alternating current (AC) from the grid into direct current (DC) for the 20 electrolysers in the plant. These electrolysers — units roughly the size of a small shipping container — use electricity to split the oxygen molecule (O) in water (H2O) from the two hydrogen molecules (H2). In simple terms, water is turned into hydrogen, with oxygen left over as a by-product. The renewable hydrogen produced by Holland Hydrogen 1 is then transported by pipeline to Shell Pernis, where it is used as an energy source to help decarbonise fuel production at the refinery.
The FlexH2 concept: smarter turbines, smarter offtake The FlexH2 concept aims to create a more intelligent energy system integration, including wind farms, the power grid and a hydrogen factory. With FlexH2 the wind turbines are “grid forming” — equipped with power electronics and controls that mean they do not even need to be connected to the main AC grid. They can run their own AC grid (offshore or remotely) and then connect to a simpler (and therefore smaller and lighter) DC substation connection.
That is especially valuable for offshore substations, where every square meter and kilogram count. Once the electricity generated using the FlexH2 concept reaches land, an intelligent “energy router” calculates whether the power should go directly to a hydrogen plant, to the electricity grid, or to both. A smart algorithm makes this decision based on electricity market prices and/or grid capacity. In short: if the grid is congested, electricity can be routed directly to a hydrogen plant — or to another large consumer.
Windpark Borssele III/IV van Blauwwind (joint venture inclusief Shell) voor de kust van Zeeland (Foto: Shell International)
Text: Marcel Burger. Photography: Shell International, Stuart Conway, Joep van Drunen Photography (FlexH2-GROW-to-GO Webmagazine).
