Media playback is unsupported on your device Media caption The BBC's David Shukman says installing the giant turbine beneath the stromy waters was an "extraordinary" operation

A subsea turbine which uses tidal power to generate electricity has successfully completed initial tests off Orkney.

The turbine was lowered into position during winter storms and Scottish Power Renewables said it was performing well.

The 100ft-high 1MW (megawatt) Hammerfest Strom HS1000 device is already powering homes and businesses on the island of Eday.

There are plans to create a 10MW tidal power array in the Sound of Islay.

This gives us confidence ahead of implementing larger scale projects Keith Anderson, SPR chief executive

Testing began in December and has been designed to finalise the timetable for the Islay project, with machines being installed "as early as feasible" between 2013 and 2015.

Keith Anderson, SPR chief executive, said: "The performance of the first HS1000 device has given us great confidence so far. Engineers were able install the device during atrocious weather conditions, and it has been operating to a very high standard ever since.

"We have already greatly developed our understanding of tidal power generation, and this gives us confidence ahead of implementing larger scale projects in Islay and the Pentland Firth.

"Scotland has the best tidal power resources in Europe, and that's why we are seeing world leading technologies tested here."

The turbine can be monitored from the European Marine Energy Centre (EMEC) base in Eday, but engineers can also operate and inspect the device from Glasgow using mobile connections and an on-board camera.