Not only tanning, you can replenish your energy by the sea (by D. Di Stefano)

(by Daniel Di Stefano)

A 60 MW photovoltaic farm was inaugurated in Singapore last July. Panels of forty-five hectares floating in a reservoir in the western part of the city: one of the largest floating plants ever created. And four other similar projects are currently underway in Singapore. For the small Asian city-state, which seeks to quadruple the amount of solar power produced by 2025, water is the most abundant surface available for panel installation.

The new generation of floating plants, both solar and wind (floating wind has the world leadership in Europe, of which about 70% is installed), will fuel the energy transition (as we can also read in the deeper analysis) of RES Magazine), especially where, as in Singapore, water conditions are more favorable than on land. Is this Italy? Italy is certainly not as poor as Singapore, but it has eight thousand kilometers of coastline and an infinite number of inland valleys.

Let’s start with photovoltaics. Girolamo di Francia from Enea tells us that a solar panel in water works better because, thanks to the lower temperature, “it can even achieve 10% efficiency compared to those on land” (solar energy into electricity) Ability to change, ed.). There are other benefits that are not related to energy. As if they were a shadow, the panels keep the water temperature low: “They also reduce evaporation by up to 80%, which is a serious problem in some contexts. Just think about the parts of the Po”. And they reduce the presence of algae, “which means clean water and, near dams for hydropower generation, means lower maintenance costs”.

These advantages go along with the main limitation of floating plants: cost. “On an average they account for 30% for building infrastructure and over 50% for maintenance. These are not dramatic numbers, but we should take them into account”, explains Di Francia. Balancing the pros and cons, the researcher concludes that this type of installation “should be considered when there is no availability of other surfaces for the system”. except at sea, where corrosion and the forces to which they would be subjected would cause damage such as would not justify the investment (even if promising new technologiesIgnore the view of potentially usable areas in Italy including lakes, irrigation water basins, old mines), “we have to install 200 gigawatts (GW), 3 times that required by the Integrated National Energy and Climate Plan “.

But we’re talking about a theoretical probability from which 60% must be deducted (“You can’t cover the entire lake with panels, and specific studies indicate that you don’t need more than 40% of the surface should be known”) and valleys which are not suitable from the point of view of landscape. “There remains – calculates Di Francia – 20 potential GW. But I’m more realistic and I think free float becomes an interesting option, especially in contexts where energy-intensive commitments are nearby. , such as irrigation systems in agriculture”. “Setting up some kind of on-site exchange with nearby reservoirs could be a really interesting option. This technology can be profitably used to cover a good portion of the 6 Terawatt of the agricultural sector’s energy needs”, compared to the provisions of the NRP”. If today we have only small “almost experimental” installations in the country An interesting aspect, say the experts, is certainly the contingent of SMEs who mainly produce plants abroad.

If floating photovoltaics can play an important role but are certainly not the hero in the supply of green energy, then the case of wind power is different. Floating wind is clearly onshore and more expensive than traditional offshore (“but the cost is coming down rapidly”, explains Simone Togni, president of Enev, a consortium of wind energy companies). However, since it does not require a foundation, it can also be placed where sea level is deeper than 60 m, where winds are generally stronger and more regular.

Estimates suggest that about 80% of the world’s offshore wind potential is contained in waters deeper than 60 metres. For this reason, according tointernational energy agencyOcean air will increase rapidly over the next two decades due to the impetus of floating solutions. A floating turbine is fixed on a giant floating buoy attached to the seashore with steel cables: for example the buoy of the Highwind Scotland plant, built in Scotland by Equinor by the technical hand of the Italian Saipam, hollow steel cylinder with a diameter of 15 There are 8,000 ton meters filled with sea water and 5,000 tons with a ballast of rocks or metals to hold them upright.

“The float is the perfect solution for the Mediterranean Sea, a sea where the seafloor is already very deep, a few meters from the coast,” says Togni. And where, therefore, the traditional solution, the shovel hinged on the foundation, is less feasible. “This is why”, continued the chairman of Anew, “it is very important that these technologies have matured from an economic point of view, and that is why many authorization proposals are being launched in this regard”.

Of the approximately 3.5 GW projects for which requests for environmental impact assessments have been submitted to MiTe, more than half concern free float: the Canale di Sicilia, eastern Sardinia, the Adriatic opposite Rimini, and Civitavecchia, a smaller project in the Tyrrhenian in front. In this area, our country has industrial and research prowess: we noted the contribution of SIPEM in the installation of Highwind Scotland turbines, and recently the first scale prototype of the Hexaflot floating turbine (SAPAM patent published pending verification) by CNR and SIPEM. Thanks for the cooperation. on one’s own.

What the contribution of floating wind power could be, we are told from estimates sent by Enev to the Ministry of Ecological Transition: “Three years ago we predicted 900 MW by 2030 with conventional installations. Recently updated estimates 5.5 Potential GW represents all viable and economically sustainable projects, which have also been verified from an industrial point of view. Two-thirds of this growth of more than 4 GW comes from free float. Too bad, according to the authorities. Given the five-and-a-half years required for this project, we will not see the first floating wind turbines in action until close to 2030.