H2 generation on floating offshore wind power plants
How to ramp up the production of green hydrogen in just a few years and distribute it quickly across the country independently of the development of the H2 core network explained Jens Cruse, shipbuilding engineer, at the end of January this year before an expert audience in Hamburg.
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Self-sufficient, floating wind power plants, placed in European waters, are to produce the molecule required primarily in industry for defossilization, directly on the platform by electrolysis from desalinated seawater, and to bind it to the LOHC (liquid organic hydrogen carrier – see also p. 23). Shuttle tankers, which have long been common in the oil industry, could then transport the valuable cargo to land or to the nearest port on a monthly basis, for example.
Jens Cruse, who after years of research set up his own company, lists the advantages of direct H2 production on the high seas: “Such a model can save up to 50 percent of investment costs because neither electricity nor gas pipes have to be laid.” The expensive grid connection is also eliminated, which speeds up the entire process because you don’t have to wait for lengthy approval procedures. Operating costs are also reduced if you are not tied to a pipe system. The so-termed offshore H2 generators are intended to be used where there is a lot of wind, almost around the clock.
“You don’t have to travel to Patagonia, Namibia or Australia,” says the founder and managing director of Cruse Offshore GmbH. “We have this right on our doorstep in Europe, particularly off the coasts of Norway, Ireland and Scotland,” he says. The electrolysis systems that are still relatively expensive today could run the whole year there, with a maximum of free to harvest wind energy.
Definitely more cost-effective
Producing hydrogen at sea by integrating the electrolyzer into the wind power station would cost even less than producing hydrogen in an offshore wind farm that is connected to the water splitting system via a power cable. Another advantage of the integrated solution is that the low-voltage direct current from the wind power station can be used directly by the electrolyzer. This saves on the conversion of electricity and the associated losses. Transporting hydrogen via pipeline is known to be more cost-effective than transmitting the electricity via lines. By connecting the electrolyzer directly to the wind power station, the basic costs are also eliminated that would otherwise have to be taken into account for a platform at sea or a land area for parking the container with the electrolysis plant.
In the model, the floating system withstood the heaviest loads, states Professor Moustafa Abdel-Maksoud, director of the Institute of Fluid Dynamics and Ship Theory at the Technical University of Hamburg (TUHH), who, together with his team, carried out simulations to optimize the system for extreme weather conditions at sea and tests in the TUHH’s wind and wave tunnel. Not even a simulated wave more than 16 meters high impaired the functioning of the system. “The system works perfectly, and it’ll pay off,” says Abdel-Maksoud. “We are technically and scientifically capable of realizing this,” he says. The innovative technology also avoids competition for space with conventional offshore wind farms and is not dependent on surplus electricity for H2 production.
Technically and economically feasible
After years of preparatory work and scientific tests, Cruse with a consortium is now planning to build a 5?MW plant that combines wind power, seawater desalination, electrolysis and H2 storage in LOHCs. This is being done as part of the three-year research project ProHyGen, which is receiving support from the German economy ministry (BMWK) [1]. This is a joint project with, besides Cruse Offshore GmbH and the TUHH, also the university Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), the machine and gearbox manufacturer Renk and the company specializing in the processing of crude oil derivatives H&R.
That the production of green hydrogen on floating plants is economically and technically feasible is also demonstrated by another BMWK-funded project, by research institute Fraunhofer ISE [2]. Its concept also envisions the climate-neutral gas being transported by ship, but not bound to LOHCs, instead stored in pressurized tanks in which the hydrogen is compressed to 500 bar.
The 5?MW prototype from ProHyGen is to be deployed in the German exclusive economic zone (EEZ). The foundation of the planned H2 offshore generator will consist of four “floaters” that are connected under water and filled with ballast water. The material used is the sheet steel in shipbuilding. One of the floaters carries the wind power station; another houses a plant for desalinating seawater as well as an electrolyzer and a component for storing the hydrogen in an LOHC. Below this is a rotating buoy and the anchor cables used to attach the H2 offshore generator to the seabed. Two further floaters consist of double-walled tanks in which the LOHC carrier fluid is stored. These are normal oil tanks. The existing oil infrastructure can also be used in other ways with this process, stresses Cruse, indicating the railways and waterways that already connect industrial ports with industrial sites today. Hamburg, for example, offers the best conditions for this, because heavy metal production companies located in the port are already potential customers for hydrogen. In addition, the tanks with the hydrogen bound to the carrier oil can be distributed deep into the country by train or barge, as is currently still the case with fossil fuels. This long-established transport network extends to neighboring European countries. A functioning infrastructure is also an important criterion for a rapid market ramp-up of the hydrogen economy.
This sketch shows where the necessary systems are located
Investors wanted
“After testing of the prototype, the system will be scaled up to 15 MW and in the course of 2025 produced in series,” explains Jens Cruse, who has registered a patent for the process and is responsible for the industrial utilization of the concept. A further goal of the joint project ProHyGen is the planning of offshore H2 parks in the gigawatt range. If all goes well, installation of the first 3?GW park producing green hydrogen could begin in the second half of 2027, according to Cruse. “To do this, however, we need financially strong partners who want to support these future-oriented innovations,” he says.
The green hydrogen bound in an LOHC can be transported to land by ship
References:
[1] https://www.tuhh.de/fds/research/current/modular-ship-assist-1