Power beyond Coal

Turning coal or oil-fired power plants into building blocks for a new energy future.

The coal exit is happening. Now.

75% of global CO₂ emissions in the power generation sector are caused by coal power plants. No surprise, they are one of the largest emitters of greenhouse gases. No question, we need to step away.

Moving forward with brownfield transformation

Why we need to convert to gas as bridging fuel 

Why we need to convert to gas as bridging fuel

We all know we´re heading towards a carbon-free future. Likewise, it’s clear that we cannot built a new energy system from scratch. Therefore, we need to repurpose as much of our existing infrastructure as possible to enable a fast transition towards a new energy system – while reducing CO₂ emissions at the same time. Building these bridges towards the future is called ‘Brownfield Transformation’, compared to new construction – ‘greenfield´ – projects.


One important part of this effort is converting coal or oil-fired power plants. For example, repowering an existent coal plant into a highly efficient combined cycle plant allows reducing CO₂ emissions by up to 70%. It also increases operational flexibility, which in turn allows it to address the increasing share of renewable power. Converted to a gas fired plant your turbines can co-fire hydrogen – and we´re striving for 100% in the future. This way, your old power plant that’s critical for energy supply today, can still fulfill this function tomorrow – just with gas instead of coal or oil.

Brownfield Transformation: Building a bridge to a new energy future

Here’s a power plant. There’s the decarbonized future we aim for. Check our new white paper to explore the options to repurpose existing plants to achieve our goals.


What you gain from repowering

Capex saved by up to 30%

Compared to greenfield projects, brownfield transformation reduced Capex by up to 30%.

Fast track implementation

Reusing existing infrastructure enables shorter implementation times, less paperwork.

H₂ ready solution

H₂ capability depending on configuration and frame type up to 100% possible.

Siemens Energy turbines offer an even wider fuel flexibility. Other hydrocarbon fuel mixtures can be discussed, too, also from biomass.

Hydrogen Decarbonization Calculator
CO₂ Savings by up to 70%

Reduce ~ 200 Mio €/a CO₂ cost (for 1.100MW, 8000hrs/a, @40€/t)

Variable plant size

Configuration of a power plants conversion is adjusted to a client’s needs.

Our gas turbines portfolio
Operational flexibility, 20%-100%

Conversions enable operational flexibility from 20% to 100% of plant capacity with short startup times.




Making the most of Coal2Gas

A full repowering entails not just changing the fuel from coal or oil to gas but converting the steam power plant to a highly efficient combined cycle power plant (CCPP) by reusing infrastructure, site permits and local personnel.

Not only is this approach faster and more sustainable; it also saves up to 30% of Capex compared to a greenfield solution.  Depending on site and project specific demands on execution time, availability, sustainable reuse of assets, space or simply Capex both is possible: The so called indoor or outdoor approach for a full repowering.

Indoors you can reuse most of the existing infrastructure such as foundations, connections, housing and piping which saves time and money where outdoors you can start building in parallel when the existing plant is still running to secure critical supply. We find the most suitable way for your needs.

Full repowering

Boiler conversion

A boiler conversion involves a modification of the burner technology and a change of coal or oil to gas. While switching to gas as a fuel does not increase the efficiency of the steam plant, it does reduce CO₂ emissions by up to 50%.


‘Topping’ requires the installation of a small gas turbine, regardless of whether the fuel is switched from coal to gas or not. The thermal energy contained in the flue gas of the ‘topping’ gas turbine is fed directly to the steam generator of the existing plant. This results in a slight improvement in overall plant efficiency.


Boosting requires the installation of an additional – usually medium – gas turbine and a waste heat boiler. In contrast to topping, the heat energy contained in the flue gas of the gas turbine is used with the aid of a heat exchanger to generate high-pressure steam and to preheat the feed water of the existing process. Boosting makes the steam power plant more flexible, while also increasing efficiency and reducing CO₂ emissions.

Parallel Repowering

Parallel repowering utilizes the steam contained in the flue gas of a newly installed large gas turbine with the aid of a heat recovery steam generator for additional feedwater preheating and steam generation in the existing steam power plant process. This conversion also serves to increase the flexibility and efficiency of steam power plants, but to a greater degree than boosting.

Four steps: From here to a CCPP

Understanding customer’s market environment, the regional energy system and regulatory framework in order to create a customized cost-optimized, efficient, or flexible solution, while aiming at the same time at integrating as many existing assets as possible.

Analyzing how to integrate the new equipment – such as gas turbines or generators – fit into the existing plant layout and infrastructure. Especially for indoor solutions, it’s important to analyze how existing foundations, piping and connections can be reused, while ensuring the new setup will work smoothly and safely.


Identifying the best configuration with the best thermodynamic fit in order to match the future operating regime with the intended business model. This can involve various, far-reaching measures, as, e.g., the steam cycle of a conventional steam power plant differs fundamentally from that of a CCPP.

Adapting the existing steam turbine and generator to operating parameters of a combined cycle plant. This may concern especially higher temperatures – up to 600°C and more for a steam turbine – that modern CCPPs use today.


Is Coal-to-Gas repowering the right choice for you?

Please answer the questions to see if your plant might be a candidate for a Coal-to-Gas repowering

Examplary value impact with Coal to Gas Repowering

  • Marginal costs decrease as savings in costs for CO₂ certificates overcompensate higher fuel cost of natural gas compared to coal
  • Lower marginal costs may lead to increased dispatch

Assumptions (2021): Increase of annual production up to 2.500 operating hours /year due to higher merit order caused by lower generation cost of gas plant; Electricity price: 68 €/MWh; gas price: 21 €/MWh;

coal price: 9 €/Mwhcoal equivalen ; ø load: 1.100 MW; efficiency coal plant 38%; efficiency gas plant >60%; CO₂ certificate cost: 50€/t

  • Alberta has a carbon tax of currently 40C$/t that is increasing annually (2022: 50C$/t; 2023: 65 C$/t; 2024: 80 C$/t up to 170 C$/t in 2030)
  • All power plants with higher emissions than benchmark of a combined cycle plant need to pay tax for surplus emissions

Assumptions (2021): Increase of annual production up to 2.500 operating hours /year due to higher merit order caused by lower generation cost of gas plant; Electricity price: 60 C$/MWh; gas price: 16 C$/MWh; coal price: 10,5C$/MWhcoal equivalent; ø load: 1.100 MW; efficiency coal plant 38%; efficiency gas plant >60%; CO₂ tax (2021): 50 C$/t (increases annually)​

Sample project schedule

Project Specific Concept

Thermodynamic Fit

Geometrical Fit

Customer decision

Decision for preferred concept and GT technology

Indicative Estimate

Submission of price indication based on clarified scope of supply

Study and detailed technical dialog

(6 – 8months)
Feasibility Assessment:
 Detailed evaluation of all project significant terminal points
Front End Engineering Design (FEED): Detailed technical, legal and financial  design . Evaluation and planning of complete project  which results in a fixed-bid quote or final report.

Tender process / Exclusive bid process

Tender process:

based on FEED study report


Exclusive bid process:

based on firm bid

Provisional Acceptance

24-36 months after contract award and notice to proceed  (NTP)


1st technical dialog and clarification of boundary conditions


NDA as basis for data exchange mandatory

Data Provision

Basic plant and operation data to be provided for optimal concept proposal


Contact us

Need additional information? Contact a Siemens Energy representative to help you.