Engineering companies and utilities are vying to get a head start in the European ocean energy business now that wave and tidal projects are moving from prototypes to larger-scale installations.

Even so, Europe's wave and tidal power technology is likely to disappoint Europen Union expectations for 2020 and take over a decade to contribute to energy supply in a significant way.

Following are key facts about ocean energy in Europe:

Potential

Ocean energy is constantly available unlike intermittent wind or solar. The energy density of waves is eight times more than air, increasing the amount of energy available, and waves can be predicted five days in advance.

The UK government's Marine Foresight Panel has said, "If less than 0.1% of the renewable energy available within the oceans could be converted into electricity, it would satisfy the present world demand for energy more than five times over."

The EU estimates ocean energy has the potential to generate 0.3% of Europe's energy by 2020 and 15% by 2050.

An EU road map predicts enough ocean energy plants will be installed by 2020 to generate 3.6 gigawatts, or enough to power 1.8 million three-bedroom houses.

It expects countries facing the Atlantic Ocean to take the lead, namely Britain, France, Ireland, Spain, Denmark and Portugal.

The EU 2050 target is 188 GW, or 15% of forecast demand in the 27-country bloc. This is equivalent to more than 100 next-generation nuclear power stations or around 470 combined-cycle gas plants.

Around a quarter of the 140 marine developers worldwide are located in Britain, which targets 200-300 megawatts of marine capacity by 2020 at a cost of 1.5 billion pounds.

Designs

There are over 200 concept designs in the sector. By the end of last year, 10 devices had been deployed in the UK at full scale and with grid connections.

UK-based European Marine Energy Centre identifies six main types of wave devices and four of tidal. Among them are:

- Oscillating water column (OWC)

Mutriku generators use the OWC design, in which a rising wave compresses air inside a chamber to drive a generator. As the wave falls, it creates a vacuum, which also drives the generator.

- Point absorber

As opposed to the OWC in a fixed installation, a point absorber is a floating structure that absorbs energy in all directions through movements at or near the water surface.

- Attenuator

Floating device that works parallel to the wave direction and rides the waves. Movements along the length of the wave can be constrained to produce electricity.

- Horizontal axis turbine

A tidal device that extracts energy from moving water in the same way that wind turbines do from air.

"It will be decided by evolution, survival of the fittest," said Anton Schaap, a senior consultant at Ecofys consultancy in the Netherlands. He believes tidal energy will take the lead over wave technology.

"Places where you can harvest wave energy are places you would like to stay away from, with 30-metre waves. Tidal energy you can harvest mostly in bay areas or estuaries."

Ocean energy shares some technical challenges with the offshore oil and wind industries - how to install and run reliable plants and equipment when they are battered by storms and corrosive sea water - and have drawn on their experience.

Studies are investigating concerns that some ocean devices disturb the sea floor and the marine ecosystem. Hydraulic spills or leaks could also cause an environmental hazard.

Projects

There has been an uptick in investment activity in the sector over the past year.

Big industrial players including Siemens, Alstom , Voith, Vattenfall, SSE and Rolls-Royce are investing in marine developers.

Alstom acquired a 40% stake in AWS Ocean Energy, and Andritz raised its share in Hammerfest Strom in the past year.

Utilities have also been active. SSE Renewables has formed a wave joint venture with Alstom, and Vattenfall announced a second UK wave test project this week.

Several prototypes are undergoing sea trials at or near full scale, but not all of them will be proved commercially viable.

Britain has about 25% of the world's wave energy and tidal stream device developers. UK companies such as Pelamis Wave Power, Aquamarine Power and Marine Current Turbines are leading the way in deploying their technologies in UK waters.

Mutriku, in Spain's northern Basque region is home to a 300 kilowatt wave power plant. Basque authorities expect it to increased installed capacity to 50 MW by 2020.

Operational since November, the plant was installed inside a newly built breakwater at a total cost of €6.7 million ($8.9 million), of which the electrical components cost 2.3 million.

The plant uses oscillating water columns - technology developed by a Siemens and Voith joint venture.

Costs

According to the European Ocean Energy Association, the cost of current prototypes are around €6,450 to €13,500 euros per KW, while initial capital investment costs of first production units are estimated at around €2,500 to €7,000 /KW.

The UK's Carbon Trust sees the levelised cost of offshore wave energy (with a 15%discount rate) at 0.38-0.48 pounds/KWh for wave energy and 0.29-0.33 pounds/KWh for tidal, compared with 0.09-0.10 pounds/KWh for nuclear and offshore wind.