Gas storage
Natural gas is much more difficult to store in quantity than other fuels.
In the days of coal gas we stored gas in gasholders which rose or fell depending on the gas volume being stored. Some designs have a diaphragm inside a fixed outer casing. Many of these have been demolished in recent years, but some remain, notably close to the M6 just north of Birmingham, and close to the Oval cricket ground. After decades of gas storage in this way, HSE have concluded that they are more dangerous than we had ever realised. Nevertheless, their advice about redevelopment at the Oval was not accepted at the planning inquiry.
Later, it seemed like a good idea to store gas in high pressure ‘bullets’ , but the quantities that could reasonably be stored this way are limited.
When the UK first moved to natural gas from coal gas, it came in from N Africa in liquid form, and concerns over the safety set in train a special review of the safety of people at Canvey island, which led to the first UK legislation specifically for major hazard sites. Recently some new LNG storage has been built to accomodate gas brought in from the middle east, but other storage modes are preferred for gas which has not been liquefied.
Simply using the high pressure gas mains themselves provides some element of a buffer store, and the typical line pressure of 75 bar holds around 24t per km of 750mm pipeline of which around one third is available as ‘storage’, The storage available in this way is increased by a trend towards uprating the maximum operating pressure of existing pipelines to 85 barg. There are few other examples of pressure equipment getting stronger as it ages.
Storage in depleted gas fields, notably offshore in the North Sea in the Rough field and onshore at Hatfield Moor, has attractions, but the rate of flow in and out of these porous rock formations is limited.
Most recently gas storage in salt caverns has become the favoured method of storage. Three sites in Cheshire are either being developed or expanded for this purpose.