EON UK Holford gas storage to partly open Q3 2011

* Three caverns to open for trading in Q3/Q4 2011

* Eight-cavern site expected to be fully open in Q1 2013

LONDON, July 23 (Reuters) - Britain's Holford gas storage is expected to be partially open in autumn 2011, with the facility fully operational a little more than a year later, operator E.ON UK (EONGn.DE) said on Friday.

"We expect to have three caverns ready for trading by the end of the third quarter, or start of the fourth quarter in 2011. Another three caverns ready in Q3, Q4 2012, and the final two in Q1 2013," a spokesman for the German energy provider told Reuters by telephone.

Compared with other working UK gas storage facilities, Holford will be the fourth largest and is expected to have 156 million cubic metres (mcm) storage capacity with delivery rate of 16 mcm a day when complete. The site is located in north-west England and consists of eight caverns, according to E.ON UK.

Scottish and Southern Energy (SSE.L) also expects to complete the expansion of its Aldbrough storage facility to 200 mcm by March 2011, up from 115 mcm, which would overtake Holford in terms of storage capacity. [ID:nLDE66K20K]

Centrica's (CNA.L) Rough is by far Britain's largest gas storage site at 3,300 mcm capacity, while SSE's Hornsea and Star Energy's Humbly Grove facilities are both 300 mcm. [ID:nLDE61O1WN]

Britain has a lower ratio of storage as a percentage of demand than France or Germany, prompting calls for more storage to be built to buffer against unexpected supply cuts like those caused by a Russia-Ukraine gas dispute two winters ago. [ID:nLDE62F2DP] (Reporting by Kwok W. Wan; editing by James Jukwey)