Hydrogen gas turbine offers promise of clean electricity

In two years, Lingen in northern Germany will become home to a pilot power station that runs on 100% green hydrogen, offering a carbon-free solution to electricity generation. As a core part of the project, Japan’s Kawasaki Heavy Industries (KHI), based in Kobe and Tokyo, is supplying RWE, a major German electric power company, with its latest hydrogen gas turbine technology.

The pilot is part of RWE’s ambitions to shift its power generation away from natural gas, coal and nuclear power, and dramatically expand its green electricity production to 50 GW of global capacity by 2030, with the goal of becoming climate neutral by 2040.

The jointly operated demonstration project, named ‘H2GT-Lingen’, is important because it shows that hydrogen-based electricity generation is feasible on an industrial scale, and can play a critical role in decarbonized energy production. It also gives an energy provider valuable experience and confidence in running a hydrogen-fired, rather than a natural gas-fired turbine.

The main attraction of using hydrogen to power generation with gas turbines, is that unlike natural gas, it can be burned to generate electricity without the production of CO₂, the major greenhouse gas responsible for climate change.

Hydrogen gas turbine challenges

KHI has developed technology that enables the conversion of existing natural gas turbines to those that can burn hydrogen instead. By simply exchanging the combustor, without modification to its main body, the whole turbine system can be adapted to hydrogen's unique combustion properties.

However, there are several challenges when it comes to operating hydrogen gas turbines compared to running them on natural gas. Firstly, careful design is needed to make hydrogen combustion stable, as hydrogen flame propagation velocity is very high — up to seven times faster than natural gas, which may lead to flame instability, undesirable pressure fluctuations, and mechanical stress on the parts of the combustor.

Hydrogen burns at a higher temperature, which leads the production of up to three times as much nitrogen oxides (NOx) than the burning of natural gas. NOx emissions are air pollutants which are associated with health issues. Finding ways to reduce or eliminate them is an important goal for hydrogen gas turbines.

In essence, two strategies are being applied by KHI to tackle this issue. The first approach is based on the diffusion flame combustion, where water or steam are sprayed into the combustor. This also offers flexibility for using mixed fuels and can be used with 100% hydrogen, 100% natural gas or any mixture of the two. The blended fuel ratio from 0 to 100% can be changed in just five minutes. Water injection, however, introduces additional equipment and thus extra cost and inconvenience.

The second — developed in response to the limitations of the diffusion flame approach — is KHI’s ‘micro-mix burner’ dry low emission technology. This is a new combustor design that has a series of concentric rings of tiny hydrogen injection holes less than a millimeter in diameter, and it results in smaller hydrogen flames that are more stable and cleaner when they burn, with reduced NOx emissions.

The H2GT-project will use KHI’s NOx-emission-reduction technology. The technology has already been tested in 2018 at the 1 MW hydrogen gas turbine co-generation system built by KHI in Kobe, Japan. This was the world’s first examples of co-generation using pure hydrogen-fueled gas turbine in a city area, supplying neighboring public facilities with heat and power simultaneously. The project was funded by a grant from Japan’s New Energy and Industrial Technology Development Organization (NEDO).

The German project is aiming to scale-up this technology with KHI’s ‘L30A turbine’, which is capable of generating 34.38 MW of electricity with a efficiency (in hydrogen-fueled operation) of 40.3%.

“We are commercializing 30MW class gas turbines, but in the future, power generation plants operating with hydrogen at hundreds of megawatts will be used by electric utility companies, and this is a technology that is just around the corner,” says Motohiko Nishimura, executive officer and deputy general manager of KHI’s Hydrogen Strategy Division.

Pursuing an entire hydrogen chain

The technology development and demonstration of the hydrogen gas turbine is a part of KHI’s long term commitment for establishing a hydrogen supply chain from production to transportation, storage and utilization. KHI has also been working on the establishment of an international hydrogen supply chain, transporting liquefied hydrogen to Japan from overseas.

In February 2022, KHI and its project partners accomplished a pilot demonstration project, transporting hydrogen produced and liquefied in Australia to Japan by sea (a project also funded by NEDO).

The world’s first liquefied hydrogen carrier, Suiso Frontier, and the receiving terminal Hy touch Kobe, built by KHI, were key to making the 9,000 km journey possible.

Suiso Frontier marks a pinnacle in ship-building activities for Kawasaki, which started making ships almost 150 years ago. KHI’s origins date back to 1878, when Shozo Kawasaki founded Kawasaki Tsukiji Shipyards, which evolved to become a major builder of ships, submarines, locomotives and aircraft in Japan.

Today, KHI is active in the aerospace, marine and motor vehicle sectors, and has also grown to encompass 100 companies around the world, making everything from robots and satellites to power stations and factories.

Nishimura says that cost reduction and scaling up all parts of the hydrogen chain are the most important issues for the future. The early 2020s have been about the demonstration of technological feasibility, and the mid-2020s will focus on dramatically expanding storage and transportation capabilities, followed by commercial offerings from 2030 onwards.

“The Japanese government is thinking seriously about establishing large-scale hydrogen infrastructure. The Suiso Frontier has a transportation capacity of 1,250 cubic metres of liquefied hydrogen, but our next ship will have a capacity of 160,000 cubic metres,” commented Nishimura. “This is part of our strategy to reduce hydrogen transportation costs from ¥89 per cubic metre (US$0.61), to just ¥2.5 per cubic metre.”

KHI’s vision is to continue to work on all aspects of hydrogen supply chain to becoming the world’s top manufacturer.