Good morning everyone! This week I want to use the blog to continue speaking about structural applications that may be competitive with UHPC. Particularly, I want to mention the possibility of using UHPC precast elements for the development of the offshore floating photovoltaic farms, a field that is still unexplored at commercial level.
You may be aware that the most mature renewable energy technologies (biomass, solar, hydro-power, etc…) require relatively large areas for a GW scale electricity generation, so they must compete for land with other uses like nature conservation areas or food production. Considering that about 71% of the Earth’s surface is covered by water, it is logic that we try to promote using part of this area to produce green energy. In this sense, the “EU Strategy to harness the potential of offshore renewable energy for a climate neutral future” (COM(2020) 741), states the crucial role of offshore energy technologies to achieve the carbon emission reduction targets.
Wind farms became long ago common in shallow waters (mainly in the North Sea) and are now conquering deeper waters. However, up to now photovoltaic facilities have only colonised lakes, and their expansion towards the sea is still in an embryonic stage. The reason are the challenging meteo-oceanic conditions of the near-shore and offshore regions, which threaten the lifespan of the structures that may be installed in these environments. This keeps potential investors away from this sector, which are the main requirement to boost the progress of the technology: The private investment.
To our view, there are two very relevant requirements to be able to install with reasonable guarantees a competitive floating PV structure in offshore environment:
- The durability of the materials used to produce the components, which is a necessary but not sufficient condition. They should guarantee the lifespan indicated in the project considering the demanding exposure class of the offshore environment (XS2, XS3, XF, etc).
- Reach an optimized and efficient design of the substructure, including the mooring system. The response of the system under the conditions of the ocean is critical, but also the size and weight of the components that form the substructure, as the transport and commissioning costs depend on this and have a strong influence on the competitiveness of the installation.
These two conditions can be faced using Ultra-High Performance Concrete (UHPC), which has an excellent durability and allows to design lighter components. In fact, this has been achieved with Formex® (the UHPC brand registered by RDC) in the last years for three very different applications in contact with water. In all the cases the solution was selected for its durability and efficiency in costs:
1. The floating pontoons that have been used as a stiffening frame for floating photovoltaic systems in the largest EU dam (Alqueva, Portugal) (photo 1).
Photo 1. Solution with Formex®. Purchased by Isigenere and installed for EDP
2. The UHPC preslabs used recently (2022) in Spanish ports for fast construction of docks (photo 2).
Photo 2: UHPC as high durability formwork installed in Alicante port. Contractor: Vias y Construcciones S.A. Client: Autoridad Portuaria de Alicante.
3. The 540 m2 floating farms to harvest mussels, installed in four different EU sea basins since 2016, and with more than 20.000 m2 installed up to date (photo 3).
Photo 3: 540 m2 floating mussel farm (Formex®) installed in Ria de Vigo
In these applications, all of them novel at world-scale, RDC (designer) and PREFFOR (precaster) are taking all the advantage that UHPC provides in terms of extra durability in aggressive environment, and minimum weight to reduce the transportation and commissioning costs. The first makes the structure resilient, while the second makes it economically efficient from day 1 (construction stage).
As done in these three examples, RDC and PREFFOR believe that the same approach can be achieved with floating photovoltaic farms for offshore environments, and to do so we became beneficiaries of the Horizon Europe project NaturSea-PV (NOVEL ECO-CEMENTITIOUS MATERIALS AND COMPONENTS FOR DURABLE, COMPETITIVE, AND BIO-INSPIRED OFFSHORE FLOATING PV SUBSTRUCTURES, nº 101084348). Leaded by Tecnalia, this research project counts with eight beneficiaries and two third-parties. It started last November 1st and it has a total budget of 3.230.444 €. During 4 years it will explore the possibilities to increase the competitiveness and sustainability of UHPC, while developing competitive designs that may support the development and scalability of the sector.
We invite all of you to attend the public kick-off meeting that this project will organize at the beginning of 2023. See you there!