Marine energy: How It Works and Why It Is Important

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It is one of the most available renewables on the planet, yet marine energy is rarely spoken when clean sources are mentioned. The reason is simple: the technologies are still being developed and not commercialised. Investment is slowed down by a number of factors, not least the absence of major public intervention in creating widespread support mechanisms.

The growth of solar and wind power in recent years has shown that the commitment of institutions in defining policy and funding frameworks can generate adequate incentives for their development.

But before exploring the sector’s growth potential in Europe and Italy, let’s see what exactly is meant by marine energy and how its latest innovations work.

MARINE ENERGY TECHNOLOGIES

Research into most renewables has long defined the best way to harness different types of energy source. Solar energy is captured with panels. Wind is converted into electricity through wind turbines. For marine and ocean energy, this is not yet the case. Scientists around the world are still trying to find out which technology is best suited to converting energy from the seas and oceans.

The answer may change depending on the marine environment where the plant is built. In Canada’s Bay of Fundy, where 160 billion tonnes of water are moved twice a day by the tide, a tidal power plant should be the answer. 

The high power of the waves hitting Portugal’s ocean coast has encouraged local governments to fund wave research since the late 1970s, while in Italy, the University of Rome is developing more suitable systems to capture the energy produced by the small waves of the Mediterranean Sea. In the Netherlands, where more than 3,300 cubic metres of freshwater flow into the sea every second, it is salinity gradient energy that has the greatest potential.

There are many sources of marine energy and the most promising are listed below. Energy from offshore wind farms is also occasionally referred to as marine, but we have decided to exclude it from this list.

WAVE ENERGY

Wave energy is the most promising in terms of capacity (the earth’s surface is over 70% water) and the second most promising in terms of technology development. Installations can be placed both along the coast and in the open sea. Estimates of the potential for wave energy indicate a minimum of 4000 TWh/y, when Europe consumes about 3000 TWh/y.

TIDAL STREAM ENERGY

Tidal currents are caused by the gravitational forces of the sun and moon, and therefore the energy harvested this way is not affected by weather conditions. This is why the technologies for generating energy from tidal currents are incredibly reliable and predictable. These operate through turbines very similar to wind turbines.  Since water is 832 times thicker than air, underwater turbines capture more energy than their wind-powered counterparts and have smaller blades.

The analogy with wind turbines has made it possible to make very rapid progress in terms of technological development. In Europe, there are already several projects that are laying the foundations for the start of commercial production.

TEMPERATURE DIFFERENCE (OTEC)

OTEC (Ocean Thermal Energy Conversion) plants use temperature differences to produce a constant flow of energy. These technologies are particularly suitable for the decarbonisation of tropical islands that currently depend on expensive (and polluting) fossil fuels. Through desalination, OTEC can also produce drinking water, the scarcity of which on remote islands causes severe hardship to those populations.

SALT GRADIENT ENERGY GENERATION

Near deltas and fjords, a type of power generation can be implemented that exploits the difference in salinity gradient between fresh and sea water. It can be used 24 hours a day and is therefore an ideal complementary source of energy to other renewables. 

The most advanced technology of its kind is Reverse ElectroDialysis (RED), in which a saline solution and fresh water are passed through exchange membranes that alternate anions and cations to generate electricity. The potential is very high, because, in addition to being widely predictable, the energy produced by one cubic metre of fresh water is comparable to that generated by the same cubic metre falling from a height of 260 metres.

THE POTENTIAL OF MARINE ENERGY IN EUROPE

The European Union sees a great opportunity in marine energy: at the end of 2020 the Commission published the European strategy for development of offshore renewable energy sources aimed at increasing the capacity of offshore installations fivefold by 2030 and 25fold by 2050 in order to meet the Green Deal targets.

According to estimates published in the “EU Blue Economy 2020 Report”, by 2050 European production will reach a capacity of 100 GW, equivalent to 10% of the Union’s consumption or 75 million households. With almost 45% of Europeans living in coastal territories, ocean energy can therefore be readily supplied to millions of people. 

For Europe, the highest potential for developing marine energy is off the Atlantic coastline, but there are also many opportunities for use in various parts of the Mediterranean Sea and the Baltic Sea. The ultra-peripheral regions of the EU, as there is a large temperature difference between deep and surface waters in the tropics, are an excellent site for OTEC technology.

Exploiting domestic resources could help to:

This last point is especially true for islands, where electricity generated through diesel is expensive and marine energy can contribute to energy self-sufficiency.

European investment in blue energy can also generate an economic boost for coastal regions, with the creation of around 400,000 jobs by 2050. The marine energy production sector can become a very important part of the blue economy, triggering growth on the coast and inland.

The need to develop new technologies for the production chain may involve innovative SMEs and large companies for the construction of ships and the design of new mechanical, maritime and electrical engineering solutions. The development of the sector also involves the inclusion of expertise on environmental impact, safety and health management.

Unlike other renewable sources, marine energy is highly predictable and can provide a stable output of electricity. Another advantage is that most plants are underwater and therefore may face less public resistance due to their low visual impact.

At present, the plants installed in Europe are mainly non-commercial and are only intended to measure their reliability.

MARINE ENERGY IN ITALY

Italy, with its 8,000 km of coastline, is a particularly suitable country for the use of marine energy converters, provided they are developed in relation to the specific characteristics of the territory. Neither the height of the waves nor the depth of the sea are comparable to those of the ocean, but the particular conditions of the Italian coastline offer interesting opportunities for the development of such technologies.

There are currently only two wave energy plants in Italy, both in Tuscany. The first one has been active since 2013 in Punta Righini, near Castiglioncello, while the second was built in 2015 in Marina di Pisa by the start-up 40South Energy. The latter is very small: it works 24 hours a day to cover the needs of 40 households.

Although the installation of the systems is still rather limited, for years research bodies such as ENEA, CNR and RSE Spa and several universities have been working on prototypes suited to the opportunities of the Italian sea. The most suitable sites are the Sardinian sea and the Strait of Messina. It is estimated that the strong currents that flow through the strait could power a city of 200,000 inhabitants such as Messina itself.

According to the first OceanSET report, a three-year European project for the implementation of ocean energy in Europe, Italy proudly ranks first among Mediterranean countries and second in the EU for public funding of marine energy development.

MARINE ENERGY: ADVANTAGES AND DISADVANTAGES

By 2040, estimates indicate that electricity generated using fossil fuels will still account for more than 35% of the total. This makes it increasingly important to invest in renewable energy sources such as marine energy, a very young technology that still needs to prove its worth.

Although the oceans and seas play a key role in global socio-economic activities, their share in energy production is still too small. Humans learned centuries ago how to harness the fluid-dynamic energy harvested from tidal mills. Since then, however, little progress has been made.

To summarise, this is caused by three main factors: the high cost of constructing and maintaining the plants; doubts about the best way to harness marine energy; and an inadequately calculated environmental impact. So, although the benefits of marine energy are clear, some issues still need to be explored.

For this reason, it is essential to develop not only the conversion devices, but also management softwares capable of adapting their operation to weather conditions and measuring their performance. IPPO Engineering is the software house specialised in environmental technologies which, thanks to its credibility, has attracted European funding over the years, such as that of the IEE – Intelligent Energy Europe Programme and the European Regional Development Fund. This is why it is an ideal partner in sustainable development projects under the Green Deal and Structural Funds.

Looking for a partner for a sustainability project? Get in touch with IPPO-Engineering! Our team get back to you in a short time.

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