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