The waves are always in motion and for this reason they are an excellent opportunity to produce renewable energy

Sometimes we have things under our eyes but we don't see them, just as we always have the sea seen in a somewhat restricted key, used for navigation, fishing, holidays, but we have hardly ever seen it as a source of energy.

If the renewable energy produced by the wind or the sun can have production losses, due to periods of absence of wind currents , or because of the sky cover, which reduces solar radiation, that of wave motion is, among those mentioned, the most constant and continuous.

For some years now, experiments have been carried out on how to be able to create renewable electricity from the sea, minimizing the environmental impact and giving energy autonomy even to small islands, far from the electricity grid that is produced on the mainland.

The energy crisis that arose, first from the Covid pandemic and subsequently from the Russian-Ukrainian war, has given a powerful acceleration to the exploitation and study of new sustainable systems for producing renewable energy.

In fact, the sea represents one of the main unexploited sources of renewable energy on the planet: ENEA and RSE have calculated that if exploiting the energy supplied by the oceans (wave motion, tides, salinity and thermal gradient) we would obtain a good 80,000 TWh, i.e. about five times the annual electricity requirement of the entire world.

Other estimates place this value as high as 130,000 TWh. The wave component alone, in the most conservative estimates, is around 2 TW globally, corresponding to around 18,000 TWh per year, almost equal to the planet's annual electricity demand.

Our ISWEC (Inertial Sea Wave Energy Converter) system does exactly that: it converts sea wave energy into electrical energy, making it immediately available for offshore plants or feeding it into the electricity grid to power coastal communities and small islands.

ISWEC was developed together with Wave for Energy S.r.l., a spin-off of the Turin Polytechnic. The system consists of a sealed floating hull with a pair of gyroscopic systems inside it connected to as many generators.

Gyroscopes, large continuously rotating flywheels, tend to keep their axis of rotation fixed by generating a force perpendicular to the axis to oppose external forces that tend to modify it.

This phenomenon is known as gyroscopic precession. The waves cause the unit to pitch, anchored to the seabed, but free to move and oscillate.

The pitch of the hull is intercepted by the two gyroscopic systems: these are connected to as many generators that produce electricity. A simple solution, with a high-tech heart.

From the pilot plant to the application of ISWEC for the island of Pantelleria

ISWEC is perfect for supplying electricity to smaller islands not connected to the main grid, coastal communities and offshore infrastructure, such as Oil & Gas platforms. 

The first pilot plant was installed in Ravenna in March 2019, connected to our PC80 platform and integrated with a photovoltaic system.

At the end of the experimental campaign, the plant was then decommissioned in September 2022. This type of application increases the energy self-sufficiency of structures located in an offshore environment, and perhaps in geographical contexts in which the electricity supply is not taken for granted.

In February 2023, Eni completed the installation of the first ISWEC device in the Mediterranean Sea, 800 meters off the coast of Pantelleria.

ISWEC numbers in Pantelleria

The ISWEC model installed off Pantelleria consists of an 8x15m steel hull which houses the energy conversion system, consisting of two gyroscopic units of more than 2 m in diameter each.

The device is kept in position, at a depth of 35 m, by a special self-aligning mooring according to the weather and sea conditions, composed of three mooring lines and a swivel (rotating joint), while the electricity produced is brought ashore via an underwater electric cable.

The device will be able to reach 260 kW peak of wave energy production and will also have the purpose of acquiring data to optimize the design of new devices.

Aside from waves, the sea can provide clean energy in many other ways

To study and make the best use of the energy potential of the seas and oceans, in collaboration with the Turin Polytechnic, we have created MORE – Marine Offshore Renewable Energy Lab: a laboratory entirely dedicated to the development of technologies to exploit wave motion, but also ocean currents, tides and salt gradients, as well as to improve wind and solar offshore.

Our commitment to the development of the marine renewable energy sector has been strengthened by our entry, as lead partner, into Ocean Energy Europe (OEE) , the largest European organization for the development of ocean energy.

An assignment that allows us to contribute to the definition of strategic lines for the development and marketing of technological solutions for the production of renewable energy in an offshore environment.

The technical challenge

The energy of the waves is the most constant of the renewable ones: unlike the sun and the wind, the sea acts continuously.

This energy is also the most “dense” because it concentrates that produced by the wind and that deriving from the heating of the atmosphere due to Sun.

The main aspects to resolve associated with ISWEC were two: corrosion due to salt and the optimization of the operation of the device as the intensity of the waves varies.

Both have been overcome as the moving and delicate parts are inside the sealed hull, completely isolated from salt water, while the operation of gyroscopic systems that power the two generators is optimized by a system that responds to different weather and sea conditions.

ISWEC has an active component in the energy capture process, which is regulated by the rotational speed of the flywheel and the torque of the generator and allows to adapt the inertia of the hull to the wavelength of the sea that hits it.

This feature, implemented for the first time in the world by Eni on a large-scale prototype, is the real point of discontinuity with respect in fact, with other capture systems, it is possible to vary the inertia of the device as if we were modifying its dimensions, effectively obtaining a virtual variable geometry system.

Large-scale integration

ISWEC is an example of the teamwork that generates each of our proprietary technologies. In this case, one of the most delicate technological challenges to solve was the sizing of the gyroscopic system to optimize its response to the local conditions of the sea, a fundamental step to exploit that constant availability which constitutes the most interesting feature of the motion wavy.

It involved analyzing and cross-referencing large quantities of data from different sources, meteorological data and those relating to the functioning of the machine.

Help has come from HPC4 and HPC5, our supercomputers: thanks to their computing power we use advanced mathematical models to elaborate answer formulas suitable for every weather and sea situation.

A further technological addition to ISWEC was the installation of photovoltaic panels on the hull deck which offer a large capture of solar resources.

Moreover, the integration between our people and structures and the MORE Lab is particularly deep and diversified. The laboratory, in fact, is based at the Polytechnic and employs research infrastructures of the Department of Mechanical and Aerospace Engineering and interfaces with the Marine Virtual Lab in the Green Data Center of Ferrera Erbognone, which uses the HPC5 supercomputer.

MORE Lab also networks with the Pantelleria site, where ISWEC is connected to the island's electricity grid.

The ISWEC of Pantelleria contributes to the island's objective of energy independence and to the elimination of the landscape impact potentially caused by any industrial facilities on the island.

At full capacity, the MORE Lab employs around 50 researchers who collaborate with our people, for a rapid growth of specific know-how and for the industrial finalization of technologies .

The center also has a naval test tank and state-of-the-art laboratories. At the same time, the Polytechnic of Turin has activated a specific chair on "Energy from the Sea" to train engineers specialized in the design, implementation and use of new technologies that will be developed right in the laboratory.

The impact on the environment

Although different, all maritime settlements look alike because they have similar needs. A small inhabited island is not that different from a platform.

For this reason it is possible to supply electricity from renewable sources to communities living on small islands.

Furthermore, ISWEC can be perfectly integrated with other renewable energy production solutions in the offshore sector, such as wind power, for example, in terms of both of connection systems to the electricity grid and integration within a sea area, maximizing the conversion of available energy.

A further advantage of this technology is the considerable reduction of the landscape impact as the device only emerges for about 1 meter above the water level.

Machine translation. We apologize for any inaccuracies. Original article in Italian

Source Eni