UPDATE 2-SSE Marchwood to start by Dec,Glendoe out to 2010

* Marchwood CCGT raises SSE capacity to 11.5 GW

* Glendoe hydro power not to resume until 2010

* Greater Gabbard offshore wind farm to start in 2010

* Griffin wind farm to be completed in 2012

(Adds details on Marchwood start)

LONDON, Sept 28 (Reuters) - Scottish and Southern (SSE.L) said on Monday the 840 megawatt (MG) Marchwood combined cycle gas turbine (CCGT) plant in Southampton should start operation by Nov 11 after final test runs.

"Ensuring Marchwood becomes fully operational in the next few weeks is the most immediate priority in our programme of projects and investments," Ian Marchant, chief executive, said in a company statement.

"We have a portfolio of gas-fired power stations that should be able to make a much more significant contribution than last year to meeting the country's energy needs this winter."

Marchwood Power Ltd is a 50:50 joint venture between SSE and ESB Inernational. It will to raise SSE's installed capacity to 11.5 gigawatts. (GW)

SSE said its total investment in the plant in southern England will be around 200 million pounds ($319.7 million). With a net thermal efficeincy in excess of 58 percent, it will be one of the most efficient gas-fired power stations in the country.

Please click for FACTBOX on UK power stations expected to start operation this year [ID:nLS240059]

SSE said its 100 MW Glendoe hydro power plant was unlikely to resume until well into 2010 at the earliest after falling rocks caused a partial blockage last month.

"The fall of rock in the tunnel carrying water from the reservoir to the power station is very substantial," it said.

"SSE is now working...(to) achieve a resumption of electricity generation at the site, but this will not take place until well into 2010 at the earliest," it said. Referring to the 500-MW Greater Gabbard offshore wind farm, a joint venture with RWE npower (RWEG.DE), SSE said it will generate first power in 2010 as scheduled, despite defects in the first three turbine foundations being currently repaired.

"SSE's contractors remain confident that there will be sufficient progress during the coming months to ensure the project remains on course to produce electricity for the first time in 2010 and to be completed on schedule by 2012," it said. Last year, SSE sold 50 percent stake in the project in the outer Thames Estuary to RWE. [ID:nL3327719]

Greater Gabbard was expected to have a load factor of over 40 per cent and produce around 1,900 GWh of electricity in a typical year, of which SSE will take 50 percent, it said.

The project will require a total investment by SSE of around 650 million pounds, excluding connection to the electricity grid, SSE said.

Clyde wind farm in southern Scotland, one of Europe's largest onshore wind farms, will have a load factor of around 35 percent to generatoe more than 1,000 GWh a year, it said.

In July, SSE said it was scaling down Clyde's capacity from 456 MW as it would save investment without reducing the annual output. [ID:nL1157648] The 136 MW Griffin wind farm in Perthshire in Scotland, in which SSE has 90 percent, should be completed in 2012, SSE said. Its construction was expected to cost around 200 million pounds.

(Reporting by Nao Nakanishi)