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Is maintaining pumped storage assets enough?


Given the critical role pumped hydro storage plays in being a clean, low-cost and renewable energy storage system, is simply maintaining key hydropower equipment enough? Or, should a more rigorous approach be undertaken to intrinsically ‘improve’ the efficiency at pumped storage hydropower plants for the long term, asks Chloe Hirst of Belzona


THE DEMAND FOR RENEWABLE energy storage systems has never been greater. While technologies, such as flywheel energy storage and compressed air energy storage, are growing in popularity, pumped storage hydro, first established in the 1890s, is the largest type of grid scale energy storage system in the world. The 2021 US Hydropower Market Report identifies how in the US, pumped storage hydropower currently contributes 93% of grid storage. With COP26, the UN Climate Change Conference, set to be hosted later this year, the discussion of pumped hydropower storage is high on the agenda; and for good reason. According to the International Energy Agency (IEA) Renewables 2020 Report, hydropower will account for 16% of the world’s electricity generation by 2025. For many countries, a large proportion of this will include pumped hydro storage plants. For Europe, the IEA’s Report outlines how by 2025, more than half of new hydropower capacity additions will be pumped storage power plants. The outlook is looking similar for China, with pumped storage accounting for more than half of new hydropower plants between 2023 and 2025. The evidence is clear: investment into pumped hydro storage is on the rise, globally.


Advantages of pumped storage In its 2020 Energy White Paper, the UK Government outlined how long-duration energy storage technologies, such as pumped hydro storage, play a crucial role in decarbonising the UK’s electricity supply. This will, crucially, help countries such as the UK and many others meet their net zero carbon emissions target by 2050, in line with the Paris Agreement. In terms of reliability, pumped storage helps to


From top to bottom: Chloe Hirst


Francis turbine runner subjected to double the erosion


Turbine cover damaged by erosion and corrosion


Right: Roughness comparison between polished stainless steel and Belzona 1341. Surface Inspection: Leeds University


10 | August 2021 | www.waterpowermagazine.com


improve grid stability. Given the nature of ‘stored’ electricity, pumped storage hydro provides power whenever it is needed. In this way, it is a proven solution for meeting the reliability, capacity and timing demands of electricity consumers. For example, according to the Environmental and


Energy Study Institute’s 2019 White Paper, pumped storage hydropower is more than 80% energy efficient through a full cycle. The research also highlights how facilities can typically provide 10 hours of electricity, compared to around 6 hours for lithium-ion batteries. Pumped storage is also an economically beneficial solution. A 2021 Report by Imperial College London (ICL) stated that new pumped storage hydro projects could save the UK energy system between £44 million and £690 million a year by 2050. This is because, according to ICL, pumped storage is less expensive than other electricity storage technologies.


Don’t just maintain – improve With such a rapid growth in renewable energy storage


technology, the IEA says that: ‘To sustain this level, output from existing hydropower plants needs to be maintained; however, substantial amounts of generation will come from fleets that are ageing.’ The report identifies that by 2025, 40% of the world’s


hydropower output will be from countries with fleets that are more than 40 years old. It highlights how this is ‘…the age at which the first major refurbishments are undertaken to either maintain or increase performance.’ As there is such a high dependency on this type


of energy storage technology, asset owners should deploy appropriate repair solutions to ensure that hydropower plant integrity isn’t simply ‘maintained’, but also significantly ‘improved’ for the long term.


Key challenge areas One of the key application areas that is subjected to


large amounts of wear is the turbine runner. As the turbine runner is used in reverse as a pump during the storage phase as well, all these pieces of equipment are subjected to twice the amount of erosion compared to a standard hydropower turbine. Similarly, bearings, blades, shafts, valves, end covers and penstocks are also subjected to twice the amount of wear per Gigawatt of energy produced during the


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