Offshore Renewable Energy & Offshore Renewable Energy

Limited availability of maritime space 

The limited availability of maritime space in some sea basins combined with the increased necessity to produce green energy calls for solutions to organize MRE production coherently and efficiently within the available space. 

Additionally, in some sea basins such as the North Sea, available maritime space is becoming scarce, and the predicted upscaling of offshore wind may generate environmental effects putting additional pressure on the chemical, biological, and physical balance of the marine ecosystem. (See page dedicated to Offshore Renewable Energy & Marine protection and restoration on this matter). 

This limited availability and fragility of maritime space is a clear challenge that calls for an improved hybridization of different ORE technologies, ideally sharing the same infrastructure and therefore not competing for space nor increasing pressure on ecosystems.

High installation costs of OREI

Initial investments in OREI such as offshore wind projects are significantly higher than costs of onshore projects, due to the additional costs associated with foundations (in case of fixed-bottom infrastructure) and connection to land. As an example, it is estimated that the cost of an offshore wind project is around €1 to €2 billion for 500 MW and around €1.5 to €3 billion for 1 GW [3]. A common estimate is that the cost of 1 kilometer of cable is around 1 million euros. 

In terms of the price per kW, the average cost of offshore wind installed in 2015 was $4,650 per kW, almost three times the equivalent cost of an onshore wind turbine [4].

Therefore, sharing platforms or energy transfer cables for different ORE technologies remains a good solution to ensure that the costs are shared, for mutually beneficial economic efficiencies.

Limited reliability of renewable energy systems in terms of grid stability and balancing

Grid balancing can be defined as the process of “Ensuring that at every moment electricity consumption is equal to electricity production” [5].

Most MRE technologies (and more globally renewable technologies) are intermittent: wind, wave or solar resources for example aren’t constantly available and predictable as their availability and output can fluctuate significantly based on external environmental factors. This can pose a challenge when demand exceeds supply as only so much electricity is available to be distributed at any given time. This also links to the fact that energy storage options that could mitigate intermittency are still being developed (via power-to-gas projects for example). 

Consequently, in the absence of economically viable large-scale storage systems, a renewable energy system focused only on one intermittent source does not provide a reliable energy supply.

Hybridizing different MRE technologies could therefore be a solution to ensure stability of electricity production and availability. As explained by a 2023 paper exploring “The energy park of the future: Modelling the combination of wave-, wind- and solar energy in offshore multi-source parks” [6], integrating different supplementary offshore renewable energy sources into multi-source parks allows one to smoothen the energy output, while increasing the energy yield per area.

Now that we have identified the main challenges related to general ORE implementation and development, we will detail the challenges related specifically to the combination of different types of ORE.

Usage restrictions within a multi-ORE park

One of the main challenges in combining different ORE technologies within a single energy park is linked to the possible restrictions of use within the park. Some activities can be allowed within a single-ORE park but forbidden in the case of a multi-ORE park. An example of this  is the possibility for fishing activity or maritime transport to take place in some OWF under the right conditions (for more information on this, please visit the page dedicated to Offshore Renewable Energy & Fisheries as well as Offshore Renewable Energy & Maritime transport). However, in the case that a complementary technology is installed, such as floating solar panels, this would render it impossible for fishing boats to sail through the park and therefore a loss of fishing grounds. 

Upgrading a single-ORE park to a multi-ORE park

The process of upgrading from a single-ORE park to a multi-ORE park raises several difficulties. The first one is financial: the park operator must ensure that the benefits of installing supplementary ORE technology will be high enough to cover the cost of installation in the short to medium term and to create profits in the long term.

From a technical point of view, the possibility of upgrading from a single-ORE park to a multi-ORE park is conditioned to an integrated design from the outset, with adaptability built in right from the start. 

From a legal perspective, upgrading from a single-ORE park to a multi-ORE park must comply with the operating license and therefore must have been considered beforehand when obtaining the necessary permits. 

Technological compatibility 

Technological compatibility can raise several issues. The main challenge is to avoid any effect which could reduce energy generation, such as the wake effect [7] for wind technologies.

To avoid such issues, during the design of the ORE development, the technical constraints of the different technologies must be considered to maximize the potential energy generation of each technology but also to ensure the most efficient maintenance of each. 

Integrating plans for multi-ORE farms into MSP to reduce pressure on maritime space

One objective of MSP is to identify areas with high potential for ORE development. This requires consideration of all the other activities taking place at sea (fishing, coastal tourism, cruising, environmental protection, etc.) to ensure the best possible location while harmoniously organizing sea space, not putting pressure on threatened or protected ecosystems, and ensuring the best possible energy yields.

Based on this approach, MSP should play a key role in fostering the implementation and development of multi-ORE farms, notably by considering the usage restrictions (as mentioned above in the challenge section) or technology restrictions on specific areas. 

MSP should ultimately play a role in exploring the combination and exploitation potential of multi-ORE platforms and facilitating their implementation and development as multi-ORE farms aligned with MSP objectives by allowing a reduction of the pressure on maritime spaces. The MSP process should be flexible enough to identify suitable areas for strictly mono-ORE farms, suitable areas for multi-ORE farms (integrated design from the outset), as well as suitable areas for mono-ORE parks which provide for the possibility of upgrading to multi-ORE once technological maturity or technical compatibility has been demonstrated.

The ultimate objective of integrating plans for multi-ORE farms into MSP is to reduce pressure on maritime space. A 2023 research on “The energy park of the future: Modelling the combination of wave-, wind- and solar energy in offshore multi-source parks” [8] analyzes the combination of wave, offshore PV and wind energy in the case of Ten Noorden van de Waddeneilanden, a future wind farm in the North Sea. Results showed that the yearly electricity output increased, “by utilizing the same amount of marine space and a majority of the existing infrastructure, ultimately, reducing the pressure on the overall marine ecosystem and other stakeholders”.

Implementing multi-ORE farms in the most high-yield areas possible through zoning

The research for the most efficient energy outputs in multi-ORE farms calls for precise studies to ensure the most suitable location for such infrastructure. Therefore, analysis must be conducted on the environmental factors of different areas considered that could influence positively or negatively the energy yields of a multi-ORE farm.

A case study was conducted in the western Iberian Peninsula in 2021, showcased in a study titled “Combining offshore wind and solar photovoltaic energy to stabilize energy supply under climate change scenarios: A case study on the western Iberian Peninsula” [9]. The study examined the spatiotemporal energy variability in the Region to ensure the best combination possible between the selected ORE technologies and the area of implementation. The results were clear: “Offshore wind energy resource is greater than the PV solar one in the western Iberian Peninsula. Both renewable sources showed high spatial and temporal variability throughout the year.” [...] “Offshore wind energy resource is rated as excellent in most of the region, except in the coastal areas closest to shore where it is rated as good or fair. When the stability of the resource is improved by combining PV solar and wind energy, the total index classification increases, especially along the coastal fringe closest to land where the lowest rating is “good”. Additionally, in this context, it was demonstrated that some areas located north of the region improved their classification by one level after considering the hybrid offshore wind-PV solar energy production system concept, thus proving the potential of combining different ORE technologies in carefully selected locations to ensure high-yields. 

Moreover, combining different ORE technologies in the right areas allows for an increase in energy outputs and grid stability (although it may create usage restrictions as mentioned before).

The pre-cited study on “The energy park of the future” [10] states that the addition of wave, solar and wind accounts for a strong improvement in grid reliability and security. The energy output of the park is smoother: its coefficient variation decreases by a yearly average of 13%, and the periods in which production is low (less than 140 MW per hour) decreases by 86.5%.  In a nutshell, the park output is less volatile and the grid better balanced.

In the case of the previously mentioned study on the Western Iberian Peninsula [11], the conclusion on the energy efficiency when combining several ORE technologies was also clear : ”The combination of solar photovoltaic and wind energy resources in a hybrid offshore wind-PV solar farm, significantly improves the total renewable energy resource and reduces the spatial and temporal variability of both individual energy resources, which is of crucial importance for a more efficient and optimized use of energy derived from renewable sources”.