The team carried out a comprehensive review of hybrid offshore renewable energy harvest systems that integrate multiple technologies on a single foundation. They report that these systems could help countries meet ambitious climate targets while limiting the footprint of energy infrastructure on marine ecosystems.
Lead author Dr Liang Cui from the School of Engineering at the University of Surrey noted that current offshore wind farms already span thousands of square kilometres, yet each turbine actually occupies less than 1 percent of that area. "Offshore wind farms currently occupy thousands of square kilometres of ocean, but the turbines themselves use less than 1 per cent of that area. By adding wave energy converters, tidal turbines or solar panels to existing wind turbine platforms, we can generate far more power from the same ocean footprint."
The review assessed data from demonstration projects including Norway's W2Power wind wave system and the NoviOcean platform, which combines wind, wave and solar technologies. Studies showed that hybrid configurations can reduce the cost of electricity by 10 to 15 percent compared with standalone offshore wind farms. In some cases, power generation increased by up to 70 percent when tidal turbines were added to existing wind installations.
The researchers also found that adding wave energy devices to floating wind turbines can improve structural behaviour. The additional equipment reduced unwanted platform motions by about 15 percent and lowered stress on tower foundations, suggesting that carefully designed hybrid systems can enhance, rather than compromise, mechanical stability.
Co author and PhD student Yukun Ma from the University of Surrey highlighted the potential benefits for consumers as offshore wind expands. "These cost reductions could translate directly to lower consumer energy bills as offshore wind expands. The European Union aims for renewable energy to account for at least 42.5 per cent of final energy consumption by 2030. Hybrid offshore systems that generate steady power around the clock could be crucial for meeting these targets."
Within the range of concepts surveyed, wind wave integration emerged as the most technologically mature hybrid option, with several systems already at the demonstration stage. Wind solar and wind tidal combinations also show strong promise, but they remain at earlier phases of development. Multi source systems that combine three or more energy streams are beginning to appear, with NoviOcean's platform reported to achieve a capacity factor of around 40 percent.
However, the authors stress that several critical gaps still need to be closed before large scale commercial deployment can proceed. Most existing studies focus on normal operating conditions and do not fully address how hybrid platforms will perform under extreme events such as hurricanes, earthquakes or tsunamis. Long term behaviour of foundations after decades of cyclic environmental loading is also not well understood.
Co supervisor Professor Suby Bhattacharya from the University of Surrey pointed out that better use of ocean space can reduce ecological disruption if designs are robust and long lived. "More efficient use of ocean space means less disruption to marine organisms that inhabit or migrate through these areas. But we need demonstration projects with long-term monitoring to prove these systems can withstand extreme weather and deliver reliable power over 20 to 30-year lifespans."
The paper calls for systematic research frameworks that couple engineering performance with economic assessments, environmental impact studies and policy analysis. The authors argue that successful rollout of hybrid offshore energy systems will depend not only on advances in design and modelling, but also on supportive regulations, appropriate financial incentives and the development of specialised infrastructure including installation vessels and skilled workforces.
Research Report:Hybrid offshore renewable energy harvest system: a review
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