Enlit Europe - The Guide: Season 3 June 2021 - A Just Transition - Page 29

scrap yard and replacing it with the latest hybrid or fully electric powered car . It sounds logical and is widely accepted . But it is also expensive .

Imagining the same approach of dumping an entire multi-unit coal fired power plant of the size a small city , built from thousands and thousands of tonnes of concrete and steel , being part of a fully developed infrastructure and connected to the local , regional and national grid .
The answer could still be to dump the asset and recycle as much of the useful material as economically feasible and replace the generation capacity with new installations of any kind .
But the answer could also be to transform the existing asset into a state-of-the-art power generation facility which is already pre-designed for the incorporation of future technologies like energy storage , energy conversion or carbon capture to achieve zero carbon emissions at the end of the transformation journey .
The very basis for allowing such full transformation is the shift from coal to gas firing through full repowering .
REPOWERING SOLUTIONS While the idea of repowering coal fired power plants is not entirely new and several large-scale projects during the past 20 + years around the globe have proven to be technically and commercially sound , repowering never grew out of a niche existence owing to the then valid economics .
As legislations and consequentially markets transition towards clear decarbonisation targets and concrete coal exit plans , repowering of legacy coal fired power plants is expected to experience a strong renaissance as it provides several beneficial characteristics compared to greenfield replacement solutions , such as :
• meeting the same CO2 reduction and nearly the same plant efficiency values ;
• significantly lower investment cost ;
• significantly shorter implementation time , including lower administrative efforts , e . g . for licenses and permits ;
• usage of existing grid connection ;
• high sustainability factor due to continued operation of major power plant equipment , continued employment of qualified personnel , ongoing utilization of existing infrastructure , buildings and local small businesses supporting the operation and maintenance of the plant .
As in most brownfield projects there is no onefits-all solution for repowering of coal fired power plants . However , the principle approach is always very much the same , combining highest plant efficiency and operational flexibility with the maximum reuse of the existing plant equipment and infrastructure as technically , economically , and ecologically reasonable .
Besides changing the fuel source and incorporating newest gas turbine technology , this also includes updating the remaining equipment to the best possible functional and performance level .
The main principle of a full repowering involves the replacement of the original coal fired boiler with a heat recovery steam generator ( HRSG ) and a simple cycle gas turbine installation .
This would be connected to the steam turbine of the original plant . In order to provide the best operational and highest thermal efficiency of the future combined cycle power plant a steam turbine retrofit comprising latest state-of-the-art steam turbine technology is usually part of the repowering approach .
Depending on the site specifics , such full repowering can be implemented as a supplemental solution , where the simple cycle gas turbine installation and the HRSG would be built outside the existing turbine / boiler building or as an integrative solution where all new equipment would be installed within the boundaries of the existing plant buildings .
Both approaches have their pros and cons . While the supplemental outdoor approach requires enough free space for the construction of the new equipment at the plant location , preferably close to the steam turbine hall , the connection between old and new equipment is less complex
Image credit : Supplied by Siemens Energy 29