The next-generation of offshore wind turbines may not be connected to the grid and transmit electrons ashore, but use the electricity they generate to power electrolyers producing green hydrogen
Siemens Gamesa and Siemens Energy are developing an entirely new type of offshore wind turbine that will produce green hydrogen rather than electricity.
Together they hope to demonstrate a ‘hydrogen wind turbine’ with two 5-MW containerised electrolysis modules integrated into it, in a representative offshore environment, in 2025/26.
There are numerous challenges to be overcome in the development process, but as Siemens Energy senior product manager Alexander Habeder tells Offshore Wind Journal, the advantages of an offshore wind turbine that produces green hydrogen rather than electricity are significant.
One of these advantages is that an island mode turbine would enable windfarm developers to get around the well-known problem of curtailment. Another is that the electrical losses usually experienced in a turbine and when electricity is transmitted ashore would be eliminated, making the hydrogen-producing turbine more efficient than its electricity-producing counterpart.
Interest in green hydrogen from offshore wind is evident in a fast-growing number of projects in which industry leaders such as Siemens Energy, Siemens Gamesa, and developer Ørsted have embarked on. If the hydrogen wind turbine project is a success, it could enable developers such as Ørsted to continue to dispatch power ashore – in the form of green hydrogen – whatever the operating conditions might be.
Curtailment of wind generation – which occurs when there is excess generation available to meet system demand, taking account of system operation restrictions due to there not being sufficient system services necessary to run a safe and secure electricity system – would be obviated and the green hydrogen produced could be used to decarbonise hard-to-abate sectors such as transport and heavy industry.
To put this in perspective, Mr Habeder says it has been estimated that, every year, approximately 5.5 terrawatt hours of production from offshore wind is curtailed. That translates into hundreds of millions of Euros of lost production and revenue.
“The solution we are working on could ensure that all of that power is harvested and used instead of being blocked,” Mr Habeder says. “But it’s not a competition between electrons and hydrogen – it’s a way to enlarge the supply of green energy.”
Siemens Gamesa and Siemens Energy first unveiled the plan to develop offshore green hydrogen production in January. They are planning to invest approximately €120M (US$145M) over five years integrating electrolysis equipment that would produce green hydrogen into Siemens Gamesa’s SG 14-222 DD offshore wind turbine.
The concept that Siemens Energy and Siemens Gamesa are working on would see the platform on the transition piece that is used to provide access to an offshore wind turbine extensively redesigned to accommodate three 5-MW modular, containerised electrolysis systems.
In addition to the twin 40-ft containers containing the electrolysis equipment, a third container would house ancillary equipment and desalination equipment for the water used in the electrolysis process. That container would also house a power source, such as a battery or a fuel cell, that would provide power to the turbine when required.
“We want to develop a plug-and-play system that is modular, that can be easily adapted to the growth in the size of offshore wind turbines,” Mr Habeder explains. “Turbines have grown in size terrifically in recent years. Siemen Gamesa’s latest turbine is a 14-MW unit but who knows how large turbines may be in future. If the system is modular, then it can easily be scaled-up.”
Hydrogen produced by the electrolysers in the containers would leave the turbine under the pressure of the electrolysis process, without the need for compression, and be transmitted via a pipeline to a larger-diameter pipeline which would bring it to shore.
Mr Habeder says that, except in the case of an offshore windfarm that was very far from shore, the pressure inherent in the process would also be sufficient to transmit the green hydrogen to end users. Siemens Energy believes green hydrogen produced in this way can be transmitted 60-70 km without compression or the need for an additional source of energy.
There are well-known and understood issues associated with transmitting and storing hydrogen, such as embrittlement of the steel and weld used in pipelines, the need to control hydrogen permeation and leaks. Mr Habeder says specialised pipelines will be required to transmit the hydrogen, which are already available and could be adapted for use offshore.
Onshore, gaseous hydrogen is already transported over long distances through pipelines much in the way natural gas is today, and approximately 2,600 km of hydrogen pipelines are currently operating in the US alone. Owned by merchant hydrogen producers, these pipelines are located where large hydrogen users, such as petroleum refineries and chemical plants, are concentrated. The green hydrogen supply chain into which the hydrogen turbine would fit would operate in much the same way, producing and transmitting green hydrogen to users ashore, such as heavy industry, the chemicals industry and other users.
Siemens Energy has selected a polymer electrolyte membrane (PEM) electrolysis technology as the basis of the concept. As Mr Habeder explains, the company is familiar with PEM electrolysers and believes the technology also has more long-term growth potential than conventional alkaline fuel cells. The PEM electrolysers may also be better-suited to working with the intermittent levels of power generated by a wind turbine.
“The heart of what we are trying to do is leverage technology and expertise from Siemens Energy and Siemens Gamesa in a way that successfully combines the characteristics of a wind turbine with the electrical limitations of the electrolyser,” Mr Habeder says. “That’s the key to the process.
“Together, with our joint expertise and experience, we are uniquely placed to do this. Using the PEM we have an electrolyser that can adapt more quickly to variations in the load from the turbine. The PEM’s reaction time is faster, and we believe that future evolution of PEM electrolyser technology and cost-out measures will mean that it will be more economically viable too.”
“We know there are risks involved in the concept, but are confident they can be overcome,” Mr Habeder concludes. “We believe we have all of the offshore and marine experience required, and the know-how to adapt electrolyers to the offshore environment and adapt turbines to work in a decentralised way, in island mode.
“Siemens Gamesa has more than 30 years of experience in the offshore wind industry, which we are coupling to Siemens Energy’s expertise in electrolysers. Wind turbines already play a huge role in the decarbonisation of the global energy system, and the potential of wind-to-hydrogen means that in the future we will be able do this for hard-to-abate industries too.”
Siemens Energy and Siemens Gamesa hope the work they are doing will also help to reduce the cost of green hydrogen. At the same time, because the hydrogen-producing turbines will be able to run off grid, new, better wind sites will be opened up for exploitation by windfarm developers.
The company estimates that, currently, 80M tonnes of hydrogen are produced every year. Production is expected to increase significantly, but only around 1% of that hydrogen is generated from green energy sources, the bulk being obtained from natural gas and coal, emitting 830M tonnes of CO2 per year, more than Germany does in total and more than the CO2 emissions from the global shipping industry.
Replacing this polluting consumption would require 820 GW of wind generating capacity, which is 26% more than the current global installed wind capacity. Studies suggest that by 2050, hydrogen production will have grown to about 500M tonnes with a significant shift to green hydrogen.
The expected growth in green hydrogen will require between 1,000 GW and 4,000 GW of renewable capacity by 2050 to meet demand, which highlights the vast potential for growth in wind power.