| Refurbishment performance gains Hydropower


Chloe Hirst of Belzona outlines how advanced polymeric coatings and composites are enabling hydropower operators to recover efficiency losses, extend asset life and unlock additional output


WITH A SIGNIFICANT PROPORTION of the global hydropower fleet now exceeding 40 years of service, the industry faces a structural challenge: how to extract additional performance from aging infrastructure without incurring the cost, downtime and carbon burden of wholesale replacement. Operators are under pressure to move beyond “sustain output” and instead deliver measurable gains in efficiency and capacity. In this context, polymeric repair composites and high- performance coatings are emerging as enabling technologies, addressing degradation mechanisms and improving hydraulic performance.


Targeting loss mechanisms Hydropower efficiency losses are typically cumulative,


arising from surface roughness, cavitation damage, erosion-corrosion, and geometric distortion across wetted components. Turbine runners, wicket gates, valves and penstocks are particularly susceptible due to high-velocity flow regimes and continuous immersion. Polymeric coatings engineered with low surface energy and hydrophobic characteristics offer a direct intervention at the fluid–solid interface. By reducing boundary layer drag and suppressing turbulence, these systems can improve flow characteristics without altering component geometry. Performance data indicates efficiency gains of up to 7% on new equipment and as much as 20% on refurbished assets when such coatings are applied. These improvements are not trivial; even marginal percentage gains can translate into substantial increases in annual energy yield at plant scale. Surface roughness plays a critical role. Comparative analysis has shown polymeric coatings achieving significantly smoother finishes than polished stainless steel – up to 15 times smoother in measured roughness terms – directly influencing hydraulic losses. Beyond surface optimisation, composite repair systems enable structural restoration of degraded components while preserving original design tolerances. This is particularly relevant for: ● Hydraulic valves: Subject to erosion, abrasion and chemical attack, where dimensional loss affects sealing and flow control.


● Pump bearing pedestals and flanges: Where misalignment and vibration arise from surface damage and deformation.


● Switchgear sealing systems: Where leakage of insulating gases such as SF6


compromises performance and environmental compliance. Paste-grade composite systems can rebuild worn areas,


restoring geometry and mechanical integrity, followed by protective coatings that mitigate further degradation. This dual approach extends service life while stabilising


performance. Notably, certain sealing solutions can be applied in situ and online, eliminating the need for shutdowns and reducing disruption.


Avoiding the replacement penalty Asset replacement in hydropower carries significant


embedded carbon, logistical complexity and extended outage periods. By contrast, polymer-based repair strategies allow operators to defer or avoid replacement while achieving performance improvements. This has two key implications:


1. Capital efficiency: Lower upfront expenditure compared to component replacement or full refurbishment.


2. Carbon mitigation: Reduced lifecycle emissions by extending the operational life of existing assets rather than manufacturing and installing new ones. Given increasing scrutiny on Scope 3 emissions and lifecycle impacts, these considerations are becoming integral to asset management strategies.


Engineering for harsh environments Hydropower environments present a unique combination


of stressors—cavitation, sediment erosion, chemical exposure and mechanical wear. Polymeric systems designed for these conditions must demonstrate: ● High adhesion under wet and dynamic conditions ● Resistance to cavitation-induced microjetting ● Long-term stability under continuous immersion ● Compatibility with complex geometries The latest generation of coatings and composites is formulated to meet these requirements, enabling deployment across a wide range of plant components without extensive redesign. By integrating advanced coatings and composites into refurbishment programmes, plants can: recover lost efficiency; enhance hydraulic performance; extend asset life; and educe operational and environmental costs In a system where incremental gains scale rapidly, these


interventions offer a practical pathway to meeting rising energy demand without new-build capacity.


Above: Damaged hydraulic ball valve repaired with Belzona 1000 Series systems.


Above: Original geometry of flange restored with Belzona 1000 Series solutions.


www.waterpowermagazine.com | May 2026 | 29


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