As the global offshore wind industry develops, novel eco-engineering techniques help reduce the risk of seabed habitat disruption and unlock new opportunities.
Offshore Wind Energy Below Sea Level
Development of renewable energy such as wind and solar in an ecologically sustainable fashion is vital for the future of our planet. Offshore wind turbine capacity has been growing exponentially for three decades since the first windfarm came online in the coastal waters of Denmark during 1991. By 2019, thousands of individual offshore installations provided over 29 Gigawatts of power around the globe.
Image Source: Global Wind Energy Council
Most of these turbines are directly attached to the seabed by concrete and metal structures at depths of up to 60 meters. Substrate degradation and changes to hydrodynamic flow regimes due to poorly designed foundations can lead to local ecosystem destruction and the proliferation of invasive and nuisance species. This has widespread impact, not only on general biodiversity but also on local fishing industries. If offshore wind energy is to be truly sustainable in the long run, the use of ecological materials and nature-inspired design should become the standard.
Sustainable development requires long-term thinking
The long-term ecological impact of offshore wind installations has been hard to assess since no wind turbines have ever been decommissioned. With an expected operational lifespan of 20 – 25 years and an estimated additional 60 years for foundations like monopiles and gravity bases, ecosystems are clearly worth considering. The base and tower constitute roughly 80% of total development costs and are also the main focus of environmental impact assessments. It is therefore reasonable to assume that base foundations will be refurbished and reutilized while turbine heads and blades are replaced. Subsea offshore wind-farm infrastructure could be in place for nearly two centuries.
This realization is leading forward thinking engineers and regulators to re-evaluate how concrete and steel are being used in marine environments, both at the structural and chemical levels. By seriously addressing the way marine flora and fauna interact with the foundations’ surfaces, they aim to cultivate the growth of strong ecosystems from day one. At the leading edge of ecological engineering are positive feedback solutions created between concrete that enhances biological processes, which in turn protect and strengthen the concrete itself.
The new standard for concrete
For every ton of ordinary Portland cement produced (the binding agent in concrete), one ton of CO2 is emitted into the atmosphere. Furthermore, the high alkalinity and leeching out of different components from the concrete make it unsuitable for growth of most algae and invertebrate species, the first settlers in a new ecosystem. Novel concrete additives, such as ECOncrete® Admix, encourage growth of organisms that create active carbon sinks through biocalcification and photosynthesis. Thus, a project’s carbon footprint is reduced while actually increasing concrete strength and ecosystem proliferation.
A recent study focusing on subsea Nature Inclusive Design (Hermans et al., 2020) found ECOncrete’s scour and cable protection units (ECO Armour Block and ECO Mats) to have higher settlement densities of oysters and other mollusks, compared to similar solutions. The report was commissioned by the Ministry of Agriculture, Nature and Food Quality of the Netherlands and specifically focused on commercial ecological solutions for wind offshore infrastructure. Oysters are so important in this context because their exoskeletons build up biogenic reef structures that attract numerous other species (Lengkeek et al., 2017) and support complex ecosystems.
Traditionally, concrete has been cast in unnatural geometrical shapes with extremely flat surfaces, making it very hard for organic life to grow and live on. ECOncrete® technologies have ‘broken the mold’ by scientifically designing concrete structural elements that emulate natural 3D shapes with intricate surface textures, without compromising on structural integrity and durability.
Thinking green leads to cross-industry success
The advantages of using eco-concrete during coastal development projects are not just limited to mitigating anthropogenic environmental impact. ECOncrete’s products have now opened the window of opportunity for vast cross-functional utilization of concrete offshore infrastructure in aquaculture and sea farming. A recent collaboration between marine engineering contractor Van Oord and ECOncrete Technologies in the Dutch North Sea will incorporate ecological scour protection mats that also support local sea farming by enhancing the growth of oyster beds. Not only do they expect to significantly reduce the base erosion maintenance, but also boost harvestable oyster produce. Other projects are focusing specifically on enhancing lobster and commercial algae growth.
Floating wind farms don’t necessarily mean less cement
Seeking to harness stronger and steadier winds, floating turbine farms are being installed in deeper waters farther offshore. This seems like good news for the environment, as most novel anchoring technologies utilize less cement than traditional gravity anchors and clump weights. However, remote deep-sea wind farms demand much more cable to be laid on the fragile seabed and more substations to be erected. Furthermore, the required tethering creates numerous artificial surfaces that may support invasive species and ecological disruption.
Types of foundations and moorings for offshore wind turbines. Source: aquaret.com
The concrete avoided by the lack of classic base structures is expected to be utilized many-fold by complex maintenance and protection requirements. For example, extensive scour protection for numerous cable current-abrasion prop-ups, as well as mounds and anchors will be required. Jacking up cable-intersections using grout bags, foundation grouting and repair clamp grouting will all require vast amounts of cement. By incorporating ecological concrete, instead of ordinary concrete, for all anchoring and maintenance procedures, the renewables industry can significantly reduce its overall environmental impact.
The future lies in Win-Win solutions
The global offshore windfarm industry is expanding. As long-lived concrete base structures continue to be placed on the seabed, nature-inclusive design must become the new paradigm. By using ecological concrete, carbon footprint penalties will be avoided, stable marine ecosystems can be established, and maintenance costs due to sea current erosion (scouring), reduced. Cross industry collaborations and the transfer of knowledge between the different offshore industries is crucial for the benefit of local communities and ecosystems.
Additional Sources:
Konstantinidis, E. & Botsaris, Pantelis. (2016). Wind turbines: current status, obstacles, trends and technologies. IOP Conference Series: Materials Science and Engineering. 161. 012079. 10.1088/1757-899X/161/1/012079.