Gas turbines and decarbonisation

“Does the gas turbine market have a future?” asks Karim Amin, Siemens Energy executive board member and executive VP of the gas services business area. He was addressing a group of journalists gathered, appropriately enough, in Finspang, Sweden. This is a key Siemens Energy site, with a distinguished history, focused on the development and manufacture of industrial (aka medium size) gas turbines, with over 1000 produced, 70% of them with long term service agreements.

His answer is that, although there are currently headwinds, of course, not least gas price volatility, security of supply concerns and the push towards renewables, medium term projections suggest significant additions of gas turbine based generating capacity in a number of countries, with substantial new build combined cycle projects underway in, for example, Germany, Belgium, Italy, to name but a few.

Why is this? Because “Getting to net zero is not as easy as just plugging in renewables and stopping the gas. It’s not like that. And it’s not because we are a gas turbine company that we want this to be the answer. This is also what the market is telling us.”

Among key drivers behind the projected increased demand for gas turbine based capacity is the accelerating shift away from coal (in Asia, notably China, eastern Europe and USA) and the need to provide dispatchable and plannable “back-up for intermittent renewables”, exploiting the high ramp rates and operational flexibility afforded by gas turbines.

The rotating masses of gas turbine based plants can also provide inertia and help maintain grid stability.

Another positive for the gas turbine business cited by Karim Amin is significant projected growth in distributed generation (“not the large, capex-intensive projects that cost you a billion plus, but projects more in the 400-500 MW range with investments below 400-500 million euro”). The increasingly urgent imperative to decarbonise heat is also seen as improving the outlook for gas turbine based power generation, eg because of the need to provide power for heat pumps (a technology that Siemens Energy also offers) and by enabling the switch from coal (and sometimes even low-efficiency gas-fired boilers) to high-efficiency CHP (“eastern Europe is a very good example, we have a number of projects right now in Poland”, where they are “really moving away from coal firing”).

“So, we actually do believe that gas turbines remain part of the answer,” a bridge technology to enable expansion of renewables, says Karim Amin, who sees this as one of the “five uncomfortable truths” about the energy transition that they “work with” at Siemens Energy (see text box opposite).

Co-firing hydrogen

The challenge becomes minimising the environmental impact of gas turbines and preventing them from becoming stranded assets in the future, with hydrogen firing capability being an increasingly important consideration.

Even though hydrogen is currently not widely available, “what we hear from customers”, says Hans Holmstrom, MD of Siemens Energy Sweden, and VP, industrial gas turbines, is that “they want to be future proof. They say, okay, I don’t have the hydrogen now, but I need to show to my investors that I’m not going to be a dead duck, a stranded asset.”

They want to know that “if they make a big investment now, in a gas fired power plant, they don’t get stuck with something that can’t be transformed over time.” Rather, the hope is that hydrogen will be mixed with natural gas in progressively higher proportions, eventually achieving 100%. “For me, it’s not something that happens quickly and in one go. It’s step by step.”

He notes that, as well as hydrogen, there are a number of other “green fuels” receiving increasing attention for use in Siemens Energy industrial gas turbines, including biodiesel and ammonia (see diagram opposite).

Why ammonia? “We all know that hydrogen is extremely hard to transport and also hard to store, but mixing it with nitrogen and making ammonia out of it makes it much simpler to transport. You can transport it as a fluid, almost. And we know ammonia. Historically we know about handling ammonia. So, we’re looking at being able to crack ammonia into nitrogen and hydrogen and then firing it. Today we promise 50% cofiring with fully cracked ammonia. We want to go to 100% of course as soon as we possibly can.”

He notes that thinking about alternative fuels for industrial gas turbines is not a new thing for Siemens Energy. Around 15 years ago we started “testing different kinds of fossil free fuels and other types of fuel.”

But “it was in 2016 that it really took off and this is when we started to be able to 3D print the combustion systems. Because, for instance, if you burn hydrogen, it burns so quickly that it heats up the metallic parts that are close to the flame. But with 3D printing, we can make cooling patterns and cooling holes inside the metal that actually allows us to manage the process of burning 100% hydrogen. So 3D printed parts are a very important enabler for being able to go with hydrogen. It’s very hard otherwise to manufacture combustion parts that can manage the hydrogen.”

With additive manufacturing, “we download the new combustor design into the 3D printer, which makes the parts” and these parts “can then be tested quickly either in our clean energy centre in Berlin or in our test rigs at Finspang. And then we do full scale testing. It collapses the time from a concept to a fully functional component. In the old days, it would take maybe half a year from drawings to completed burner. Now we can do that turn around in two to three weeks. This means we can do fast prototyping, which is super important for us when we deal with all these new fossil free fuels. They have different properties that we need to manage and it gives the designers an opportunity to play around a little bit. You don’t play around with something that takes half a year to get delivered. But if you can play around at low cost very quickly, you can really develop everything that you dreamt of without losing a lot of money and time.”

Although currently there’s “a lot of hype” surrounding hydrogen, “with a lot of discussion in every magazine every time you open it” (MPS being no exception), “very little is actually happening”, says Hans Holmstrom, not least because there is “very little hydrogen existing on the open market.”

Nevertheless, there are a few projects worldwide where hydrogen and other alternative fuels are being used in Siemens Energy industrial gas turbines.

One example is Braskem’s 2 x SGT-600 combined heat and power plant in Brazil, supplied, built, owned and operated by Siemens Energy. Equipped with a 3rd generation DLE system, this will cofire up to 60% vol hydrogen (albeit grey), with NOx emissions not exceeding 25 ppm. “It’s up and running... it’s happening now”, says Hans.

In France, at Saillat-sur-Vienne, an EU funded Power-to-X-to-Power project, HYFLEXPOWER, is underway at a CHP plant that will demonstrate 100% hydrogen cofiring in an SGT-400 gas turbine, with first firing planned for 2023.

An example of a green-biodiesel-fuelled gas turbine project is an SGT-800 based simple cycle back up power plant being provided to Stockholm Exergi, with commercial operation in 2023.

Stockholm Exergi set themselves a target a few years ago of being fossil free by 2025, and to do that, “they need to have some backup power in case things really go wrong, there is no wind, there is no solar power and they’ve run out of stored electricity”, notes Hans. “So they came to us and said can you sell us a gas turbine that can run on fossil-free fuels?” In fact, “this one will run only maybe 50 to 100 or maybe 200 hours per year. That’s all. It’s mainly going to stand still, but it’s going to be there in case it is needed. 

And they need this security for the population of the city of Stockholm. It’s a very expensive investment, I can tell you. It’s a brownfield facility. So, they have to rip out a lot of equipment in an existing plant. It’s going to run on bio diesel, most likely HVO 100, which has very good properties, by the way, but they have to have new fuel infrastructure. It’s a major investment and illustrates what power producers have to do to comply with the requirement to be fossil free.”

It also illustrates another key role for gas turbines: “purely as a backup in case things happen. There needs to be something that is possible to start and stop on command. We’re starting to see more and more of these kinds of installations, a gas turbine that will run very little, only in emergencies, on fossil free fuel.”

A further point that Hans Holmstrom emphasises is the “super-importance” of converting the existing fleet from fossil burning to hydrogen and other non-fossil fuels. “There are tens of thousands of gas turbines out there. Not all of these will just die and disappear. A lot of them will be transformed step-by-step, burning more and more non-fossil fuels.”

One example is an SGT-800 located in Jingmen, China. The plan there is to upgrade first to 15% hydrogen capability and then to 30% and then progressively increase the proportion as “they lay their hands on more and more hydrogen.”

This is “probably going to be one of the most important ways of decarbonising the energy system... sneaking in more and more and more hydrogen over time and using to the largest extent possible existing assets. The more we can use something that exists already today, the faster the transition will go... the hurdles will be lower.”

Meanwhile, in Germany, as an illustration of the coal-to-gas switch, with eventual potential transition to hydrogen, two new Finspang-supplied 62 MWe SGT-800s (with waste heat recovery) are to be installed at EnBW’s Stuttgart-Munster district heating cogen plant, replacing coal-fired boilers at the site.

Initially, the new gas turbines will run on natural gas. “The fuel switch from coal to gas in Munster... will allow us to continue to have sufficient power generating capacity in the coming years,” said EnBW managing board member Georg  Stamatelopoulos. “This is the only way we can support the expansion of renewable energy.”

But EnBW is already thinking about hydrogen, with a time frame of about 10-12 years. Siemens Energy provides assurances that the new gas turbines will in fact be able to run on 75% hydrogen from the time they’re shipped in 2025, and they are described as “ready for up to 100% hydrogen”, with “all systems constructed from the very beginning in such a way that the natural gas can be replaced with hydrogen as quickly and completely as possible.”

“We can’t yet reliably predict when green hydrogen will be available in sufficient quantity and at affordable prices,” Georg Stamatelopoulos explains, “but the technology should be in place by that time. We’re not going to put the cart before the horse.”

Looking towards net zero

Looking ahead to how gas turbines might be deployed in a net zero power grid of the future, the Finspang site is the location of a demonstration project called the Zero Emission Hydrogen Turbine Center (ZEHTC), a collaboration between Siemens Energy and five partners (including Linde, Chalmers University of Technology and University of Bologna). The ZEHTC has received funding for 2019-2023 from the EU via ERA-Net Smart Energy Systems and from the Swedish Energy Agency.

It consists of a microgrid connected to gas turbines undergoing testing, along with PV, electrolyser, hydrogen storage and batteries.

Hydrogen is produced using excess electricity generated during turbine tests and by PV. It is stored and can then be used in turbine hydrogen co-firing trials.

The ZEHTC is intended as a real-life demonstration of what the future net zero energy system might look like, with “gas turbines working hand in hand with renewables, hydrogen and batteries”, says Asa Lyckstrom, sustainability strategist and executive board member of Siemens Energy AB (Sweden).

“The five uncomfortable truths about the energy transition that we work with” (Karim Amin, Siemens Energy):

1. Fossil fuels, eg natural gas co-fired with hydrogen, are part of the answer. Expansion of renewables is not possible without using bridge technologies. Power grids are designed for a steady supply of electricity to avoid blackouts. Every step towards being “greener” is better than not taking any steps, and better than waiting for perfect solutions.

2. Renewables don’t come for free. Massive investments are needed, and we are only just beginning to come to terms with the costs. The raw materials requirements for sustainable energy systems will also have a profound impact on the geopolitical landscape.

3. Technology is not the issue. Fair distribution of climate change’s costs and benefits as well as new arrangements for social and economic growth must be addressed.

4. Infrastructure is an issue, for example to enable sector coupling, which is essential to achieve climate goals, and accommodate an influx of distributed generation. Bringing new transmission lines into service currently takes over ten years, and requires a dramatic increase in capital spending.

5. We can’t do this alone. Addressing climate change requires co-operation: between governments, businesses and consumers.