Kicking out coal and greening gas on the road to net zero

Siemens Energy Future Energy Perspectives on replacing coal
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How do we deliver the baseload, dispatchable power and grid stability of coal-fired power plants while accelerating the rise of renewables? By ramping up H2 firing in future-proof, hydrogen-ready gas-fired power plants.

By Dr Norbert Henkel and Olaf Kreyenberg from Siemens Energy

Listen to the audio version of ‘Kicking out coal and greening gas on the road to net zero’, read by Philip Gordon.

It’s happening in France this year, the Netherlands by 2029, Canada by 2030, Germany by 2038 at the latest, and Indonesia by 2049.

What are they doing? Quitting coal – and many more countries are set to join them.

They all realise that one of the most crucial ways to effectively fight climate change is to stop using coal. And even after some controversy at COP26, 197 countries have committed themselves to at least ‘the phasedown of unabated coal power’.

According to the International Energy Agency (IEA), roughly 200GW of installed global capacity of coal power plants are exiting the market over the next years, mainly in Europe, North America and Asia.

However, doing away with coal plants also means losing baseload, dispatchable power and grid stability. These services support the rising share of renewables that solar or wind can’t provide. And coal plants also supply energy generation at relatively low fuel costs.

Moreover, shutting coal plants down has a social impact on regions and even entire countries. Suppliers go out of business and people lose their jobs. Yet it’s clear that phasing out coal is inevitable. So how do we go about achieving the benefits of coal power without relying on coal power itself?

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This article is part of the ‘Future Energy Perspectives’ series, in which experts from Siemens Energy share their insights into how we can move towards a decarbonised energy system.

Turning plans and pledges into reality

The need for more environmentally safe and cost-efficient solutions becomes even more obvious considering the growing energy demand.

In 2021, global demand, even during the pandemic, went up a stunning 6% – the highest since 2010, according to the IEA. And it’s expected to grow significantly thanks largely to e-mobility, electrical heating and the decarbonisation of industries and other sectors.

Unsurprisingly, renewables are anticipated to meet the bulk of this additional demand. In 2020, worldwide renewables were responsible for 30% of electricity generation and are projected to increase by about 45% in 2030 based on national pledges.

If we want to reach net zero by 2050, they need to increase another 15%, according to the IEA’s World Energy Outlook 2021. So how do we turn plans, pledges and what’s simply necessary into reality in a short period of time?

Most importantly, future-proofing gas plants means equipping them with turbines capable of co-firing clean fuels, mainly hydrogen or other e-fuels.

Gas-fired plants are key

There’s one key building block: gas-fired power plants. With renewables reaching a record share of energy generation, in most experts’ assessments, these power plants are anticipated to deliver an essential part of the supply in the coming years.

Currently, gas-fired plants are believed to supply around 24% of global energy generation. Through 2030, the added amount of gas power is expected to stay remarkably stable, adding around 40-60 GW per year in most market scenarios.

A state-of-the-art combined cycle power plant (CCPP) can reduce CO2 emissions by up to 70% compared to a coal-fired power plant of the same capacity.

For example, a CCPP with an installed electrical capacity of 877MW to be built with gas turbines by Siemens Energy in Komotini in the northeast of Greece will reduce CO2 emissions by up to 3.7 million tonnes per year.

For coal-fired plants facing shutdown, one can also consider brownfield conversion: in other words, changing them to highly efficient CCPPs.

This conversion is known as full repowering. It not only facilitates repurposing existing assets, but when compared to a greenfield project, it can also result in lower investment costs, as such a conversion involves shorter implementation times, less paperwork, and fewer permits.

Future-proofing gas plants

Existing gas-fired power plants can also be future-proofed by replacing older turbines with more efficient ones. It’s called Brownfield Engine Exchange (BEX). In most cases, these turbines lower emissions while providing better operational flexibility, resulting in part-load capability and fast ramp rates, thereby improving responsiveness to electricity demand, and fluctuating renewable energy supply.

Another option is using carbon capture technologies to mitigate the remaining CO2 emissions of gas-fired power plants. Today, carbon capture is considered highly viable in countries, such as China, the Netherlands, the UK and the US.

Most importantly, future-proofing gas plants means equipping them with turbines capable of co-firing clean fuels, mainly hydrogen or other e-fuels. Major gas turbine OEMs plan for all their new gas turbines to be capable of firing 100% hydrogen by 2030, with many already capable of co-firing 30-70% hydrogen today.

Unsurprisingly, most manufacturers want their gas-fired power plants to be hydrogen-ready. Accordingly, as of 2021, TÜV Süd in Germany has been offering ‘H2-readiness’ certification, and Siemens Energy is the first company to obtain such validation.

What about hydrogen?

Today, the state of hydrogen technology is comparable to the early years of solar and wind energy. And like those technologies, hydrogen has its own challenges.

For one, while it’s necessary to increase production amount, production costs must conversely decrease. Moreover, the infrastructure for distributing and storing hydrogen is largely missing. In short, major investments are crucial.

To encourage these, shortened approval processes and gradually increasing CO2 prices would be essential. Also, financial incentives should be implemented to make investments in hydrogen production and distribution a realistic option.

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Ensuring grid stability

Coal-fired plants also help ensure grid stability. They do so with the help of kinetic energy stored in the rotating mass of their turbo sets. But these plants are being shut down. And renewables without any spinning machinery keep being added to the grid. Ultimately, all this puts system stability at risk.

Hence, it’s no surprise that next to gas-fired power plants, so-called rotating grid stabilisers (RGSs) are being added to the grid as stand-alone solutions.

They usually comprise a generator and a flywheel. Together, they provide this all-important inertia by spinning continuously. Working in sync with the grid frequency, they contribute to the system’s stability, dampening fluctuations, just as car shock absorbers dampen a bump in the road.

Additionally, they provide voltage stability and enhance grid strength at its connection points. All this helps to integrate more renewables, leading to further decarbonisation.

To make good use of available assets, existing generators at phased-out coal plants can be converted to rotating grid stabilisers. There’s also the option of adding a flywheel to increase inertia contribution.

For example, at Uniper’s Killingholme site in the UK, Siemens Energy is converting two steam turbine trains into RGSs. This way, the old assets continue to operate and help generate more decentralised, renewable power in the UK.

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Different starting points for phasing out coal

As we push for decarbonisation and coal phase-out, it’s clear that different countries experience different pressures in the process.

Countries with plenty of renewables, such as Brazil, New Zealand, and Canada, are struggling less than those with a heterogeneous energy mix, such as the US, Germany, and Japan.

But others with a large share of coal-fired energy generation, such as India, China, and Poland, face the biggest challenges. Yet even they have committed themselves to the phasedown of unabated coal power at COP26.

And that means all countries have at least this goal in common regardless of where they start out. Replacing coal-fired power plants is an essential part of that goal. And while each country certainly requires solutions tailored to their respective energy systems, the necessity to do so remains the same.

Facing social impact

Finally, no matter where in the world, shutting down a coal-fired power plant is never easy for those involved. Thousands of jobs are lost, not only at power stations, but also at associated mines, and a network of suppliers disappears.

Understandably, work is a matter of personal identity for many people, and even for entire regions. Therefore, while pushing for decarbonisation, it’s important to know what re-places what’s being shut down.

Essentially, replacing or re-purposing a coal-fired power plant is so much more than just finding additional capacity and ensuring grid stability. It has a human value, having far-reaching consequences – it involves transforming entire regions and societies.

For example, in the Lusatian region of Germany, an area shaped by lignite mining and coal power plants, 18,000 coal-related jobs might be gone by 2038 when Germany officially quits coal.

That’s why today, efforts are underway to build a hydrogen industry while supporting other sectors there, giving this region new perspectives – not just for fighting climate change on a larger scale, but also for ensuring people’s well-being.


Dr Norbert Henkel is Director sales and business development at Siemens Energy GP. Henkel is responsible for the global business development of brownfield transformation/power plant modernisation projects.

He has 25 years of experience in the Siemens Energy power generation service business in different management positions in sales, marketing, business development, strategy and product management.

Olaf Kreyenberg from Siemens Energy

Olaf Kreyenberg is Vice President for Generation sales Europe, Russia and Central Asia. Kreyenberg holds a degree in mechanical engineering and has been working in the power generation sector at Siemens Energy in various management positions for 30 years.

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