Energy from the Sea: Italian Innovations Between Dream and Reality

The Transition to Renewable Sources: A Challenge We Cannot Ignore

Energy from the sea represents the largest untapped renewable source on the planet, with 80,000 billion kWh available. Italy is among the six EU countries with specific policies for wave energy exploitation, with projects like ISWEC and Rewec 3 already operational.

One of the most important challenges humanity will face in the near future is finding alternative energy sources to fossil fuels that are clean and easily exploitable. These sources should allow us to stay within the limits established by Agenda 2030, a set of European targets to be achieved in order to mitigate the effects of climate change during the 2021-2030 period.

Among the proposed targets, many refer to the energy sector. In particular, they require that at least 32% of the national energy demand come from renewable sources and that greenhouse gas emissions be reduced by at least 40% compared to 1990 levels.

In Italy, the most widely used renewable energy sources (often indicated by the acronym RES) are hydroelectric, photovoltaic, and wind. Italy is a country where land must be considered a precious resource, given the large percentage of hills and territory already used for agriculture and grazing. We have nearly reached the maximum capacity for wind and photovoltaic installations on the national territory.

Where can we get new energy? Eyes have turned to the sea. Since the Peninsula is immersed in the Mediterranean, it possesses at least two forms of energy that humanity has not yet fully managed to harness.

Discovering a New Energy Source: What Advantages Does It Offer?

In 2021, ENEA -- the National Agency for New Technologies, Energy and Sustainable Economic Development -- established that by 2030, systems for capturing energy from the sea would be installed in Italy. But how convenient is it to exploit this form of energy, and where does it come from?

The energy carried by ocean waves is primarily produced by the Sun. Through pressure differences and friction, the Sun produces wind that ruffles the water, providing it with kinetic energy that can travel great distances. Waves can also be produced, to a lesser extent, by tides, earthquakes, or Coriolis forces. Compared to better-known renewable sources, marine energy can be less affected by weather conditions and more consistently available. Studies on capturing this enormous energy source began many years ago, but only recently have some technologies proven promising in this regard.

According to ENI, wave energy is the largest untapped renewable source on the planet, with an energy quantity equal to 80,000 billion kWh that would cover more than 5 times the global energy demand. The planet's waters, especially oceanic ones, carry considerable amounts of untapped kinetic energy, greater on western coasts and less in enclosed seas. As highlighted by Eni in its ISWEC project, the lower energy carried by Mediterranean waves is not a limiting factor for the use of this source in the Mare Nostrum. In fact, Mediterranean waves are lower and less powerful, but much more frequent and more easily converted by floating systems like ISWEC.

A very important aspect to consider when discussing RES is the capacity factor (or load factor), defined as the ratio between the actual energy production of a plant and the theoretical energy it would have produced if the plant had operated for the entire time period under examination. It is an indicator of the intermittency and availability of renewable energies. The capacity factor also accounts for possible plant failures, and according to recent studies, that of the new wave energy capture technology is higher than that of wind and other renewables.

Another factor that can favour the research, development, and implementation of wave energy exploitation is energy density, which is far greater than that of wind and photovoltaic. The average energy density of waves is approximately 3 kW/m2, 20 times greater than the Sun and five times greater than wind.

Italy is one of the most active nations on the marine energy front: it is among the six EU countries to have adopted specific policies for exploiting this resource. Italian prototypes with a Technology Readiness Level of 7 or higher (TRL7+) on a scale from 1 to 9 number five, four for waves and one for tides.

ISWEC: A Revolutionary Project for Energy from the Sea

Eni collaborated closely with the Politecnico di Torino to develop the **ISWEC** system, an acronym for Inertial Sea Wave Energy Converter. This device is an energy converter that transforms the kinetic energy of ocean waves into electrical energy. It consists of a floating hull equipped with two gyroscopes. The gyroscopes, seeking to maintain their axis of rotation fixed, generate a force perpendicular to the axis to resist the force of waves that tend to make them rotate. This approach exploits the phenomenon of gyroscopic precession.

The waves cause the floating unit, which is anchored to the seabed, to pitch. The gyroscopic motion is converted into electrical energy by an electromechanical motor. The generated power can range between 50 and 360 kW. Thanks to the use of predictive mathematical models for wave frequency, the device can be optimised by synchronizing the gyroscope's rotation with the frequency of the waves.

In addition to its contribution as a new renewable resource, ISWEC proves aesthetically inoffensive. In Italy, we have often encountered "NIMBY" (Not in My Back Yard) protests, especially against wind farms, accused of ruining the landscape. The ISWEC system, positioned 800 metres from the coast and emerging from the sea by only one metre, is nearly invisible and non-invasive to the beauty of our sea.

The first prototype of this project dates back to 2006, but the final full-scale version was completed only in 2012. In August of that year, Eni and the University of Turin installed an ISWEC measuring 8x15x4.5 metres near the coast of Pantelleria. The device, with a peak power of 260 kW, was connected to the national electrical grid in March 2023.

The island of Pantelleria is located about 110 km from Sicily and has a population of 7,000 inhabitants, which doubles during the tourist season. The island faces significant energy challenges, as it is far from the rest of Italy and energy is primarily produced by a diesel power plant. This approach is costly, as fuel must be purchased and transported in tanks on ferries from Sicily. This not only increases the price of energy by incorporating transportation costs but also represents a significant source of emissions. According to the University of Turin, small devices like ISWEC that generate electricity from the sea can be the perfect solution for making remote and isolated territories like Pantelleria energy-independent, territories that cannot be easily reached by the national electrical grid.

Rewec 3 in Civitavecchia: How Can a Breakwater Generate Energy?

**Rewec 3** is an entirely Italian project, born from the collaboration of the University of Reggio Calabria and funded by the European Union. This technology harnesses wave energy in a significantly different way from the floating ISWEC, resembling more of a breakwater. It consists of an upper opening facing the sea, connected to a chamber containing half water and half air, which is in turn connected to a turbine. When a wave hits the coastline, the water level in the second chamber rises, increasing the air pressure which, passing through the turbine, generates electrical energy. The same effect occurs when the wave recedes, allowing the turbine to spin continuously. This system has been under experimentation since 2005, and a 1:1 scale prototype was built in 2012 at the port of Civitavecchia.

The sea, however, offers not only kinetic energy carried by waves but also allows the exploitation of tidal forces. Tidal energy is not yet widely used worldwide, due to costs and the environmental impact it can produce. Tides, the periodic rising and falling of sea level primarily caused by the gravitational attraction of the Moon and Sun, represent a very attractive energy opportunity because they are constant and predictable phenomena.

Capture systems for this form of energy, still in the experimental phase, can be of two main types. The "older" technology can be thought of as a hybrid between wind and hydroelectric power. It consists of a system of dams that separate the sea from smaller basins through barrier systems. During high tide, the basin fills and empties during low tide. The continuous back-and-forth movement of water from the basin is captured by turbines that, by rotating, power electrical generators, thus producing renewable and clean energy.

This technology has not yet been implemented at a global level and is still under study. Among the most important installations are the Mey Gen plant in Scotland, with a nominal capacity of approximately 400 MW; the Sihwa Lake barrage in South Korea, with a nominal capacity of 254 MW; and the La Rance barrage in France, with a nominal capacity of 240 MW.

Despite the benefits, this technology has a significant environmental impact. It is particularly harmful to the flora and fauna of the coasts where it is implemented and alters water quality. For example, in France, the three years of construction of the power plant had devastating effects on the estuary ecosystem, causing the death of several fish species and altering tidal cycles.

An alternative technology under examination consists of so-called tidal turbines or hydrogenerators, small blades anchored to the seabed that are moved by the marine current produced by tides, in a manner analogous to onshore wind turbines. When currents activate the rotary motion of the blades, the turbine produces electricity.

In Italy, tidal energy has been tested in some prototype installations. One of these is the Kobold turbine, implemented in Messina in 1999 and decommissioned in 2016. The Kobold system is very similar to the ISWEC of Pantelleria, as it is a floating system anchored to the seabed that generates energy through the movement of three turbines.

Another entirely Italian project worth noting is the GEMSTAR system, consisting of two marine turbines connected to a float, anchored to the seabed by a cable. This system, because of how it operates, is also called a "sea kite." The kite operates at 15 metres below sea level and follows the current. Operating below the water level, it allows the passage of ships and other vessels, thus avoiding the disfigurement of the maritime landscape.

In conclusion, extracting energy from the sea is no longer a dream but an increasingly concrete reality. Although further research and development are still needed, the effort invested in projects like those mentioned above demonstrates how innovation can play a key role in our journey towards a more sustainable and ecological energy future. To understand the physical principles behind these technologies, from electromagnetic waves to fluid mechanics, physics tutoring provides the necessary scientific foundations.

FAQ

What is wave energy?

Wave energy is a form of renewable energy that harnesses the movement of ocean waves to produce electricity. According to ENI, it represents the largest untapped renewable source on the planet, with 80,000 billion kWh potentially available.

How does the ISWEC system work?

ISWEC (Inertial Sea Wave Energy Converter) is a floating device with two gyroscopes that exploits the pitching caused by waves. The gyroscopic motion is converted into electrical energy by an electromechanical motor, with power between 50 and 360 kW.

What are the advantages of marine energy compared to wind and solar?

Marine energy has an energy density 20 times greater than solar and 5 times greater than wind (approximately 3 kW/m2). Additionally, it is less affected by weather conditions and has a higher capacity factor than other renewables.

Is Italy active in the marine energy sector?

Yes, Italy is among the six EU countries with specific policies for marine energy. There are five Italian prototypes with TRL7+ technological maturity, including ISWEC in Pantelleria and Rewec 3 in Civitavecchia.