|June 18: Sockets at sea
The Orkney islands, situated between the Atlantic Ocean and the North Sea, are known for their strong tidal currents and the large waves coming in from the Atlantic. That makes it the perfect spot for developing wave and tidal energy. EMEC offers the needed facilities.
The ten meter long Ocean Explorer is waiting for us in the Kirkwall harbour. It sails under charter of the European Maritime Energy Centre or EMEC for short. Another reporter is aboard, a team from the South-West Regional Development Agency and EMEC's director Neil Kermode. It's about an hour to the tidal energy test site just off the coast of Eday, he tells us. Skipper Steve adds it might be choppy out there because of the breeze and the current between the islands. After the boat has quietly left the harbour, the roaring diesel blasts it over the clear blue water.
“Scotland is shaped by the ocean”, says Kermode, “and people have realised its energy can be harvested.” Tidal currents at the Orkney islands reach speeds up to 15 km/hour and the waves at the western rocky shore can build up to 13 meters high before they crash into the cliffs, bombarding the granite.
“Scotland can supply six times it's own energy from wind and water”, says Kermode. “The amount of tide and waves will probably be smaller than wind. But it is estimated that marine energy can potentially provide a quarter of the electricity in the UK. That's about half of the UK's gas plants and about the same size we're getting from nuclear at the moment.” Most of that marine energy would come from Scotland with its coast stretching from the Shetland islands in the north to the western Scottish islands in the south.
The Scottish government has invested in the maritime energy centre EMEC in the hope to get an industry off the ground for wave and tidal generators. A wave site has been installed near Stromness and a tidal test site off the coast of Eday island.
“Developers can concentrate on their devices, while EMEC takes care of the connection to the grid”, says Kermode. Essentially, EMEC takes care of anchoring the devices to be tested and connects them to sockets provided offshore. “We can measure the effectiveness and the efficiency of the devices comparing the mechanical energy that goes in and electricity that is delivered to the grid.”
After about half an hour on the boat, the tidal energy system becomes visible in front of the island. It looks like a ring in between two vertical pipes. Closer up, we see the two steel pipes towering ten meters above the water. A yellow construction has been build between the pipes to house the necessary electronics and cranes. The space in between the pipes holds a six meter diameter ring with an open tidal turbine that will spin when lowered in the current. It generates about 200 kilowatt. The design is called OpenHydro and it has been in operation for a year.
In total five berths are provided here, each connected to the island with a 1 megawatt cable.
At the wave site near Stromness, four devices can be tested simultaneously. It has been built for the future. In 2004, the Pelamis system was the first to be tested here and also the world's first wave energy system feeding power into the grid. At the moment, a drilling rig is preparing mooring for another wave energy generator to be tested.
As skipper Steve manoeuvres the Ocean Explorer near the tidal generator, he must constantly compensate for the current that is clearly visible around the steel pillars. “The watersurface here is mainly flat”, Kermode points out. “But over there you see the 'white horses' on the waves. The water here is going over underwater cliff. Choosing the right location is critical. We have still to learn what the best is: shallow and fast current or deeper and less waves.”
Compared to wind energy, tidal and wave energy are still in their early stages. Devices are generally small, while windturbines under one megawatt are hard to come by. As to the potential of marine energy devices, Kermode is cautious. ”The prediction is hard to make, but there is a huge amount of energy in the sea and if we can tap a percentage of that, we'll be doing very well.”
Back in the harbour, the Ocean Explorer takes a little detour. We end up near a towering crane and some working vessels. These are the necessary tools to provide the anchoring for the devices to be tested. Anchors are concrete blocks a couple of meters long and wide, and they have to be precisely positioned on the sea floor. You apparently really need some serious and expensive tools to get that done. “The difficult thing about tidal energy is to get the device out there”, Kermode concludes.