| Floating solar To undertake what they call is a unique analysis of


technical engineering challenges and environmental considerations, the authors say they scanned over 900 existing floating solar related publications comprehensively, selectively leading to the inclusion of approximately 400 papers. They claim the ‘key innovation’ of their review lies in its comprehensive, inter disciplinary approach to examining FPV systems and is one of the first to synthesise knowledge across multiple domains, including hydrodynamics, structural analysis, power prediction, and environmental impacts. Some of the key findings from this study suggest: The potential for enhancing energy efficiency through water-based cooling techniques. Innovative modularised designs to support upscaling. Positive environmental impacts including artificial habitats.


Although the design, modelling and environmental effects of existing FPV research are discussed in detail, research gaps remain. This review highlights an urgent need to simulate the dynamics of numerous floating bodies in waves, i.e. modular FPV systems. There is also a significant gap to designing and optimising the mooring system and although FPV systems have somewhat shown positive impacts on the environment, the environment can also induce biofouling and corrosion on FPV which, the authors claim, is barely studied nor mitigated.


Swiss studies To help address the question of how hybridisation


of existing hydropower plants could affect water resources management, new research has focused on a project in Switzerland. And although the joint operation of solar and hydropower can certainly improve the performance of a power system, on the other hand, Miocci et al say in Renewable Energy, complementing an existing reservoir-based hydropower plant with a PV plant may affect the way the reservoir was previously operated, with possible consequences on storage conditions and water availability. ‘To our knowledge, these effects have been rarely investigated in the literature, despite their relevance,’ the authors claim. In their work they proposed a modelling framework


for an existing pumped storage hydropower plant located in the Swiss pre-alpine region, complemented by a fictional floating solar photovoltaic plant with a nominal capacity equal to about 50 % of the hydropower plant. Lake Sihl is an important artificial reservoir, located in the foothills of the Swiss Alps and was created in the 1930s to regulate the streamflow regime of the torrential river Sihl. The lake drains a 155.5km2


large


catchment, spanning from 889 to 2282m asl. Water collected in Lake Sihl is mostly used by the Swiss Federal Railways for hydropower production in the Etzelwerk plant, which is an open-loop pumped storage plant that exploits a difference in elevation of about 480m between Lake Sihl (upper reservoir) and Lake Zurich (lower reservoir). Seven Pelton turbines are installed in the powerhouse providing a nominal installed capacity of 120MW. Although Lake Sihl mainly has a hydropower purpose, its management is still dictated by a set of


Left: Map of the study area covering Lake Sihl in Switzerland. Geodata were derived from swisstopo and from the Hydrological Atlas of Switzerland. The red line between Lake Sihl and Lake Zurich represents the pressurised system feeding the Etzelwerk hydropower plant Source: https:// doi.org/10.1016/j. renene.2025.123530


Below: Lake Sihl in the Swiss alps


flood protection rules and environmental mitigation measures. Indeed, the Sihl river poses the largest flood threat for the city of Zurich, while from 1 June to 31 October, Lake Sihl must undergo a strict constraint to prevent mosquito proliferation which means active storage capacity is reduced to about 20x106


m3 . The modelling framework for this study considers


reservoir management constraints and environmental flow requirements. Long-term simulations covering 38 years were carried out at a relatively high temporal resolution (one-hour). The authors explain that such long-term simulation allows for better characterisation of hydro-climatic conditions, which drive both hydro and solar power generation. The hourly simulations over 38 years show: A 20% increase in overall annual energy production. An improvement in the system reliability through mutual complementarity. A potential for enhancing downstream environmental flow up to 50% during the hot summer season, thereby enabling more streamflow for ecological purposes.


The results confirmed some benefits of hybridisation already pointed out in previous studies, such as an increase in the overall annual energy production and an improvement of system reliability. In addition, the authors noted a potential for enhancing downstream environmental flow conditions, without strongly invalidating the benefits of energy production and reliability of supply.


Micocci et al say this hybridisation real-word case study is particularly significant due to: The presence of a pumped storage facility, which also allows for storage of PV energy exceeding the demand. Detailed representation of the mechanical and hydraulic components of the plant. Reproduction of strict management rules which guide reservoir operations, particularly during summer.


As a further development of this work, the authors say they are planning to repeat the numerical experiment under future climate scenarios, to analyse possible vulnerabilities and opportunities of solar-hydro hybridisation in a changing climate.


References


https://parliamentnews.co.uk/ floating-solar-can-help-the-uk- achieve-energy-security


https://www.bbc.co.uk/news/ articles/c39zjzw72e0o


An interdisciplinary literature review of floating solar power plants Yujia Wei, Danial Khojasteh, Christian Windt, Luofeng Huang. Renewable and Sustainable Energy Reviews 209 (2025) 115094. https://doi.org/10.1016/j. rser.2024.115094


Hybridization of an alpine pumped-storage hydropower plant with floating solar photovoltaics: a study from the water resource perspective Domenico Micocci, Christiana Bragalli, Elena Toth, Tobias Wechsler, Massimiliano Zappa. Renewable Energy 253 (2025) 123530. https:// doi.org/10.1016/j. renene.2025.123530


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