Background:
The sector floating solar energy is experiencing a yearly growth that exceeds the 200% of CAGR. At this moment, the challenge is to face harsher environments, where wind, currents and waves are too high to use the typical solutions with polyethylene floaters. One of these environments is the Alqueva dam, the largest artificial lake of the European Union, where a floating farm of 5 MW was approved and will be operational in 2022. The solution designed by the successful bidder was with a perimetral pontoon that protects the area with the floaters and solar panels. This pontoon acts also as a stiffener to reduce the number and cost of the mooring lines. Obviously, assuring the durability and the cost efficiency of these pontoons is a key for the success of the project. In close cooperation with the contractor, RDC designed a UHPC pontoon that was later produced at PREFFOR factory.
Why to use UHPC?
Generally, UHPC is competitive in applications where durability can provide a significant competitive advantage, and there where lightness provides a significant competitive advantage. In this case, both are very relevant. Durability is important due to the humid environment and the abrasion and fatigue caused by the waves. The lightness of the solution is key for several aspects: 1) A pontoon has an average density lower than 1. If the walls are thinner the weight is lower, so the depth of the pontoon can be reduced maintaining the density below 1 and reducing even more the weight and the costs. This makes the UHPC pontoon very competitive compared to concrete solutions. 2) A lighter element requires less draft to float, so the hydrodynamic forces are lower, saving costs in mooring lines and connections. 3) Transport and manipulation costs can be significantly reduced. In this example, transportation costs were divided by two compared with a traditional concrete solution.
Besides, the microcracking and autogenous self-healing capacity of UHPC are particularly interesting in this application, as large strains imply cracks that never exceed the 100 μm and they heal in few weeks under the water.
Advantages:
- Reduced costs compared to other solutions due to the savings in material.
- High durability and minimum maintenance costs.
Achievements:
- First world use of UHPC in commercial floating solar farms (2021)
- Utility model of UHPC stiffener for floating solar farms launched
