Using the sea to boost our energy

Taking the waters at Marseille
Is a green wave heading for Marseille? Nicknamed Smartseille, the Allar eco-district project that will be home to 4000 residents and is set to rise from the earth by 2018 has plans to be truly innovative in terms of sustainable development. Firstly, it will use a system that is connected to the neighbouring buildings: based on the needs of the day, energy will be supplied both to office air conditioning units and radiators in homes. As a result, loss is avoided. Secondly, the soil will undergo gentle remediation using mushrooms! More environmentally friendly than burying contaminated soil, using mycelium can absorb and transform contaminants, heavy hydrocarbons, cadmium and lead within the mushroom body.
But the flagship project at the first national pilot site recognised by the French Institut pour la Ville Durable (Institute for Sustainable Cities) is the installation of an air conditioning system that uses sea water.How does sea water heating work? By collecting heat from sea water to provide the future district and its 500,000 square metres of offices, facilities and homes with energy. To do this, sea water is pumped from the depths to the shore, where it is circulated in a three-kilometre underground network that runs alongside the internal water circuits of each connected building. Via this loop, a heat exchange takes place, and the system provides heat in the winter and cooling in the summer. It’s a first for a development project under the EDF Optimal Solutions brand.
Using marine currents instead of air currents at Paimpol-BréhatSea winds have long been full of promise – just take a look at the increasing number of off-shore wind farm projects around the world. But what if, instead of dipping their toes in the water, wind turbines dived head first into the sea? At Paimpol-Bréhat (Côtes-d’Armor), a tidal turbine plant is showing promise by using energy from marine currents rather than air currents. And there are benefits over their wind-powered cousins: they are quieter and make use of a more constant and more powerful source of energy, as water is 800 times more dense than air, removing the need to build huge blades.
In Brittany, located 35 m under the sea – without drilling to cause the minimum disturbance to the ecosystem – and connected to an offshore converter, four turbines of 16 metres in diameter – the first of which, named Arcouest, was installed in 2011 – are set to demonstrate the administrative, technical, economical and environmental feasibility of a sector in which France accounts for 20% of Europe’s potential. Once generated under the ocean, the current is then sent back onshore via a 16-km cable. The pilot site, which has received €40 million of investment, will soon be able to serve as a model for two new tidal turbine parks at Raz Blanchard (Basse-Normandie) and Fromveur (Finistère).
La Rance tidal power plant – a new lease of life for the oldest plant of its kind
Since 1966, the La Rance tidal power plant has been making use of the tides. The key strength of the oldest sea-powered plant? Being able to generate electricity both during filling and emptying of the basin, when the tide is rising and falling, thanks to its 24 bulb turbines and its alternators that can run in both directions. To do this, the valves are shut off at low tide to isolate the almost-empty basin, before opening them once again once there is sufficient flow to generate energy. The reverse happens at high tide: the waterways are opened wide before being closed when the basin is full.
The key asset of this system is that it is highly predictable, with tidal coefficients known years in advance, thus avoiding the problem of intermittency that plagues renewable energy sources. As proof of its success, a huge ten-year renovation programme was begun in 2014. Despite the fact that it’s nearly 50, the old plant is going strong!

To go further
Seatower sets out to conquer the deep
Nemo prepares to plunge into ocean thermal energy conversion

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