A £400 million natural gas storage site is to be built deep beneath a lough in Northern Ireland.
The island's first energy bank at Larne Lough, north-east of Belfast, will hold 60 days supply and guard against steep price rises caused by international market volatility.
Around 500 million cubic metres of gas will be contained in salt caverns a mile under the seabed and could allow Northern Ireland to export some of its stores if prices were favourable, said Stormont environment minister Alex Attwood. The minister gave planning approval for the development on Thursday.
Mr Attwood said: "This security of supply of energy will be a significant step forward in the way we manage our energy sector. North Sea gas supplies are declining steeply and this facility will make a significant contribution to the security of gas supplies for the whole island of Ireland and indeed for Britain."
Environmentalists expressed concern that the dumping of salt to build the caves into the sea could harm marine biodiversity. Many gas sources are found in unsettled parts of the world and can be affected by civil strife or market reactions to broader economic shocks.
Mr Attwood said gas could be purchased for storage when prices were low for use or sale when they were higher, helping Northern Ireland's future economic development. The nationalist SDLP MLA promised construction jobs for the area but said he was also conscious of environmental concerns.
Large parts of Northern Ireland are relatively dependant on fossil fuels like oil for home heating but the natural gas network has been rolling out steadily from Belfast, with more development planned. The region's two main suppliers are Phoenix and Firmus.
The storage site is on land south-west and north-east of Ballylumford pressure reduction station in Co Antrim, with extending underground pipelines. It will be developed by Islandmagee Storage Ltd. A planning application was submitted in March 2010 and includes the gas storage plant and other equipment to accommodate drilling.
Friends of the Earth director in Northern Ireland James Orr said Northern Ireland should be investing in renewable energy instead. He said the area affected had been underestimated. Alliance Party MLA Stewart Dickson said residents were also worried about heavy traffic during construction.
Chief executive of the Utility Regulator Shane Lynch said the announcement was a vote of confidence in the industry. Energy Minister Arlene Foster said the decision was an important milestone and the project will provide a significant benefit to the local economy by providing jobs.