STROMNESS, Scotland -- What looks like a 590-foot, orange caterpillar spends its days undulating on the frothy tips of waves here as they break several hundred yards off the rocky coast. Its name is Pelamis, a device designed by three energy visionaries to turn wave energy into electricity.
Its five segments move up and down with the waves, and universal joints linking them allow the machine to flex in two directions. When really big waves loom, Pelamis dives beneath them with the grace of a sea otter and resurfaces again to make more juice.
Here and at several other sites dotted around the Orkney Islands, the European Marine Energy Centre (EMEC) provides a test bed where it and numerous other wave and tidal energy devices are tested.
Founded in 2003 with £30 million ($48 million) of funding from the Scottish government and other governmental and nongovernmental entities, EMEC provides the only grid-connected wave and tidal technology test center for marine renewable energy in the world.
The idea of marine-based, low-impact and, perhaps most importantly, unobtrusive clean energy sources is appealing in the United Kingdom, where carbon-free energy is politically popular. But when it comes to building either on- or offshore wind turbines, detractors emerge in vociferous throngs.
There are 11 different full-scale prototypes of such ocean energy machines in operation at the several EMEC sites. Some of them use waves, while others capture tidal motion to generate power. Utility companies E.ON and ScottishPower Renewables both ordered Pelamis devices. By early May, ScottishPower's device had exported 160 megawatt-hours to the national grid.
"If it can work here, it can work anywhere," said Eileen Linklater, client relationship manager for EMEC. "Sea conditions here are challenging at the best of times. Our motto is: 'Get metal wet.'"
Tough engineering meets harsh conditions
Orkney, where EMEC is located, is the largest in a 70-island archipelago off the coast of northern Scotland. Wave and tide potential here are the greatest in Europe. During severe storms, waves can reach as high as 60 feet. Tidal flows can travel as fast as 8 knots.
The promise of ocean-based energy generation has attracted serious attention from investors. French energy giant Alstom became a hopeful speculator with its purchase of Tidal Generation Ltd. from Rolls-Royce early this year.
Alstom's Tidal Generation turbine is parked on a long dock outside Kirkwall, the largest town on the island, alongside the machine shops of several other tidal power developers. One of the key features of this tidal turbine is the ease with which it can be transported to its ocean location.
Jim Bishop, Tidal Generation's technical manager, explained: "The equipment itself weighs 149 tons, and it has 7 tons net buoyancy, which means it can be towed to sea using an ordinary lightweight tug. This reduces the expense enormously, because we don't have to have specialized transport equipment."
Once the turbine is situated at sea, mechanical winches haul it down to the seabed, where it is anchored to a stationary tripod. Tethered, the turbine can swivel freely to face the incoming or outgoing tide.
The turbine's three 59-foot blades can change pitch depending upon tidal conditions. The anchoring mechanism allows it to yaw in either direction, depending upon the motion of the tide. "The turbine can extract energy at flow rates up to 2.7 meters [9 feet] per second, either way the tide is moving, in or out," said Bishop.
Aquamarine Power, based in Edinburgh, is testing its device, the Oyster 800, at the Billia Croo site near Stromness. The Oyster is a wave-powered pump that generates pressure to drive an onshore hydroelectric turbine.
"Basically, the machine is a flap bolted to the seabed 500 meters offshore," said Adam Young, lead engineer for Aquamarine's testing operation. "And it gets a lot of battering." Weighing in at 1,323 tons, the Oyster is built to reliably produce electricity amid the chaos of a churning sea.
"Everything has to be technically perfect because of the physical conditions of a near-shore installation," said Young. "Yes, there is offshore technology know-how out there, but it's deep sea," where there are few waves, he said. "Near-shore technology hasn't been developed to the same degree. You can't apply deep-sea technology used for oil and gas to wave energy."
There are other challenges, too. The source voltage fluctuates, depending upon sea conditions. "What starts out as AC [alternating current] voltage has to be converted from AC to DC [direct current], then back to 50 hertz AC to be exported to the grid," said Young. "There are huge expenses involved in this technology. And there is the grid connectivity issue."
An 'outdated' transmission fee
As far as Orkney developers are concerned, the U.K. grid connectivity problem is as much of an obstacle as a stormy sea, thanks to the charge electricity producers must pay to the government to transmit the power they generate onto the national grid. The rate structure was developed in the last century, when all of the United Kingdom's energy came from coal-fired or nuclear sources.
"You have to look at power generation from the point of view of population, and of resources," said Martin McAdam, CEO of Aquamarine Power. "The fee structure reflects the existing node structure. Power stations were built as close as possible to centers of industry and large cities."
There was a time when this design made sense.
"You can bring coal by ship or train to the location of the power station, and you can bring nuclear fuel to the coast where the plant is located," said McAdam. "But you can't bring wind and tides and waves to the power station in London. You have to build a wind farm where the wind is, and a wave farm where the waves are."
At the time the U.K. national grid was built, the goal was to concentrate massive amounts of power-generating capacity close to industrial centers and urban ratepayers.
"Effectively, Ofgem [the U.K. energy regulatory agency] discriminates against wind power projects from the Highlands and wave power from Orkney. We pay 10 to 15 times the national average rate for connection to the grid," said McAdam, who said the charges make it more difficult to attract much-needed capital investment.
"The grid planners know how to deal with ever-greater quantities of renewable energy. The desire to develop a low-carbon economy is thwarted by an outdated grid charging system," he said.
Fortunately for McAdam, Scotland's politicians appear more interested in a wave-powered future.
Fergus Ewing, the Scottish energy minister, recently announced at the Scottish Renewables Marine Conference that Aquamarine and Pelamis would share a £13 million award, a first wave array support program, part of the Scottish government's Marine Renewables Commercialization Fund.
For the United Kingdom as a whole, however, judging from its recent track record, the prospects for a fossil-fuel-free future are looking less rosy.
In 2012, according to the most recent E.U. statistics, the United Kingdom generated only 3.93 percent of its energy from renewables (wind, solar and biofuels). The target for 2012 was 4.04 percent. These figures fall far short of the legally binding goal of 15 percent by 2020.
In contrast, Norway currently generates more than 60 percent of its power through renewables, mostly hydroelectric power.
The United Kingdom ranks 25th out of 27 E.U. countries in its use of renewable energy. Malta, at the far end of the scale, produces none of its power from renewable sources.