The need to decrease emissions and shift to clean power makes the use of renewable sources a matter of utmost importance. Offshore parks of wind and photovoltaic systems form a significant part of this undertaking since sea areas have huge wind and considerable solar potential. The costs of developing offshore wind farms and photovoltaic systems are nevertheless high because of the complicated infrastructure in the form of submarine cables, substations, and specialized structures. In spite of the high costs, the use of these two sources together holds promising benefits. The concept of the hybrid offshore parks — integrating wind and solar systems in the same offshore installation — serves to utilize the resources more efficiently and decrease the cost per unit of power produced. In this article, the technological, design, and economic features of these parks are examined to explain how the joint application of wind turbines and photovoltaics improves the generation of electricity and reduces the cost of the installation. A detailed focus is placed on international trends and practice as well as the potential for application for countries having considerable wind and sun potential.
Offshore Wind and Solar Energy Technologies
Offshore wind technologies have developed very fast in the last decades. Wind turbines of 10-15 MW capacity and rotor diameters larger than 200 meters are today installed. In shallow water (<50 m), fixed structures such as monopiles, jackets, or tripods support the towers and the generator systems. For deeper waters, the wind farms have to be anchored using floating bases in the form of semi-submersible platforms, spar buoys, or tension-leg platforms. Floating turbines enable the use of deep-sea locations and use lighter structures that are designed to withstand high wind speeds and waves.
Likewise, offshore solar power technology consists primarily of floating photovoltaic arrays. These consist of solar cell arrangements on specialized carriers (rafts or platforms) that are anchored to the seafloor. Floating photovoltaics build on the fact that ocean space is not utilized for much besides. In addition to reduced land-use competition, cooling of the panels through seawater enhances their heat response and efficiency when compared to land-based photovoltaics. However, floating solar remains a developing technology and still in the pilot phase. Performance by pilot plants on reservoirs and lakes has proved to be reliable, but commercialization on the open sea will need to see more innovations in designs. There's also work in the sector to install solar panels on existing wind turbine platforms to maximize the use of existing infrastructure. The complementarity of the resources is exploited using the two technologies together. Wind power production will generally be high in the nighttime and in windy months, whereas photovoltaics have higher production in the daytime and in the summer. Hybrid parks therefore have a balanced overall production: sunny periods are substituted by photovoltaic production, and windy periods support wind production. The result will be more efficient use of the resources as well as lower storage system requirement (e.g., batteries or production of green hydrogen) to balance variability.
Design of Hybrid Parks
Implementing hybrid offshore parks requires integrated design of layout and infrastructure. Hybrid parks are either planned from the outset as combined spaces with multiple technologies or formed by expanding existing wind farms. In any case, the core principle is that wind turbines and photovoltaic systems share common infrastructure. This means a single substation and one or more shared submarine power cables, instead of independent connections. As a result, total construction and maintenance costs are significantly reduced, simplifying infrastructure creation and consolidating installation expenses.
Artistic representation of floating photovoltaic arrays surrounding offshore wind turbines. The combined use of wind and solar technologies allows optimal utilization of marine space. Hybrid parks maximize production capacity per unit of area and reduce the variability of generated power. Studies show that combining floating wind turbines and photovoltaics can increase installed capacity and annual energy output per surface area by multiples (up to 10 times the capacity and 7 times the production compared to a purely wind park), making marine space use much more efficient.
Shared infrastructure and cost savings: Using common substations and cable networks results in significant savings. Instead of separate substations and submarine cables for each technology, shared infrastructure reduces equipment costs by ~10–15% approximately. At the same time, development costs (works, technical studies, permits) are distributed across a single project, reducing administrative and financial burdens.
Reduction of operating expenses: In the long term, hybrid installations save resources. Start-up, maintenance, and operation of offshore facilities allow the use of common vessels and technical crews. A combined park requires less scheduled maintenance overall, leading to lower operating costs.
Improved space utilization: Floating wind turbines occupy limited surface area relative to their capacity. Adding floating solar arrays nearby utilizes the remaining sea surface (e.g., under the rotor and between turbine placements). Thus, the overall energy production density per sea acre increases, avoiding the need for new sites.
More stable energy supply: By combining different sources, the park’s overall energy output is smoother. Photovoltaics supply energy during the day, while wind turbines operate 24/7. This reduces the variability of power fed into the grid, enabling more stable grid operation and less reliance on additional storage.
Integration with storage and hydrogen production: Hybrid parks can be combined with storage systems (batteries) or electrolysis stations. Excess production during low-demand hours or surplus solar energy can be stored as electricity or converted into green hydrogen onsite. This results in a complete production and storage system, improving reliability and system efficiency.
Application Examples
There are several pilot and commercial hybrid offshore projects announced worldwide:
China (SPIC – Ocean Sun): In Haiyang (Shandong Province) the State Power Investment Corp (SPIC) installed in year 2022 the first floating photovoltaics integrated into a wind turbine. Using "Ocean Sun technology", two floating panel rings of 0.5 MW each, were mounted on an existing wind turbine, for a total of 1 MW. This pilot project demonstrated increased park production and lower levelized energy costs, paving the way for larger projects (e.g., a planned 20 MW system).
Netherlands/Belgium (SolarDuck – RWE): SolarDuck, in collaboration with RWE, developed the first full pilot project "Merganser" with a capacity of 0.5 MW, installed in spring 2024, south of Scheveningen in the North Sea. It’s a hexagonal floating structure, with photovoltaic panels, designed to withstand strong winds and waves. Additionally, in the Hollandse Kust West VII offshore project, an expansion with a 5 MW floating solar park with integrated storage solutions is underway to fully test hybrid benefits.
Italy (Saipem – AGNES): The Italian group Saipem, in cooperation with AGNES, is advancing large hybrid projects in the Adriatic and Ionian Seas. For example, the "Romagna 1" floating wind project (near Ravenna) is planned with a 450 MW capacity, next to which a 100 MW floating solar plant is proposed. Part of the solar energy is expected to supply power to an onsite hydrogen electrolyzer unit. Moreover, AGNES has submitted also proposals for some other large projects combining 2.6 GW of floating and 800 MW of conventional wind, along with an additional 210 MW of floating photovoltaics, showing Italy's dynamic role in this sector.
Greece: Although pilot offshore projects (~1 GW total) have been designed, their implementation is delayed due to bureaucracy. A fully developed hybrid park in Greek sea waters, could leverage the strong "Meltemi" winds and intense solar radiation, significantly boosting the energy autonomy of island regions.
Challenges and Future Prospects
The implementation of hybrid offshore parks faces several challenges. Technically, floating photovoltaic platforms in open seas require durable materials and special anchoring structures. Turbine blades and solar panels must withstand extreme conditions: saltwater, strong winds, and high waves. Extensive durability and safety testing for each new design is necessary. Additionally, all sea constructions must harmonize with marine ecosystems to minimize impacts on biodiversity.
Shipping and marine space usage: Installing floating systems affects marine shipping routes and fishing grounds. Designating special corridors and safety zones and collaborating with port authorities is necessary to ensure projects don't disrupt navigation.
Economically, the initial investment capital is high. Floating bases and solar platforms are emerging technologies on a limited scale and have high construction costs. Despite the scale gains from technology combination, broad adoption needs substantial cost reductions (learning curve). Furthermore, upgrading offshore transmission networks and interconnection regulations is required to support multimodal feeding (e.g., switching between AC/DC, different operational conditions). Finally, component standardization, staff training, and insurance coverage must evolve alongside the technology.
However, the future of offshore hybrid parks is bright. New studies and large European developments (e.g., EU-SCORES for offshore wind-solar-wave parks) facilitate improved designs and new platforms. New materials and management systems (IoT, intelligent sensors) are under development to secure more reliable floating installations. Smart grids enable intelligent management of the system for efficiency. Furthermore, policy commitments to net-zero emissions and clean power investments are likely to enhance financing for these types of developments. In the medium to longer-term run, economies of scale and technological maturity will reduce costs and enable even more competitive hybrid parks.