Power beyond Coal
Turning coal or oil-fired power plants into building blocks for a new energy future.Transitioning from coal to natural gas and hydrogen through Brownfield Transformation
75% of global CO₂ emissions in the power generation sector are caused by coal power plants. Converting coal-fired power plants into highly efficient combined cycle plants can reduce CO2 emissions by up to 70%. It also gives you the option to co-fire clean hydrogen in your gas turbine, enabling you to decarbonize your plant operation even further.
Based on the Brownfield Transformation concept, our approach includes repurposing as much of your existing infrastructure as possible to enable a fast transition towards a new energy system while reducing CO₂ emissions at the same time.
Benefits of repowering existing power plants
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 but it also saves up to 30% of Capex compared to building a new power plant.
Reusing existing infrastructure for repowering
There are two options to repower your plant: the indoor and the outdoor approach.
With the indoor approach, you can reuse most of the existing infrastructure such as foundations, connections, housing and piping. This saves time and costs. With the outdoor approach, you can start building in parallel when the existing plant is still running to secure critical supplies.
- Indoor approach
- Outdoor approach
What does it entail?
In principle, a "full repowering" means that one or more gas turbines with downstream heat recovery steam generators replace the old steam generator previously fired with coal or oil. In order to achieve this, various modifications of the steam cycle are necessary, as well as the exchange and retrofit of various components.
What are the prerequisites?
For a full repowering, one needs to make sure that the appropriate gas capacities are available. For the final plan, other factors to be considered are the plant capacity, the heat quantities, and levels to be supplied for district heating and/or process steam applications. Also, one needs to consider the space available, and the condition of the power plant. The overall aim is to keep as much of the existing infrastructure as possible.
What is the effect?
While it is impressive that by converting a conventional coal power plant to a CCPP CO₂ emissions get reduced by up to 70%, it’s worth mentioning that this is a result not just from the fuel switch, but also from an increase in the power plant’s efficiency from an average of 38% to up to 63%.
- Boiler Conversion
- Topping
- Boosting
- Parallel 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
‘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
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?
Is your plant a good candidate for coal-to-gas repowering? Answer the following questions to find out.
Examplary value impact with coal-to-cas 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)
References
Kirishskaya Gres, Russia
- Capacity boost: 300 to 800 MW
- Efficiency boost: 38% to 55%
- Infused technology: 2x SGT-4000F incl. HRSGs, Generators and Control System
Hiep Phuoc, Vietnam
- Capacity boost: 375 to 1200 MW
- CO₂ emission: ca. 50% per kWh reduction
- Infused technology: 3 x SGT-4000F incl. HRSGs, Generators, and Control System
Simmering, Austria
- Capacity boost: 430 to 820 MW
- Efficiency boost: 42% to 57%
- Infused technology: 2x SGT-4000F incl. HRSGs, Generators and Control System
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