The Troll A gas platform began operations in 1996. It now meets 10% of Europe's total natural gas demands and produced 26.39 billion standard cubic meters of gas in 2004.
But the field is being depleted and reservior presure is falling. Statoil recently decided to bring two 40 megawatt (MW) compressors online to maintain the platform's gas-delivery pressure.
Normally gas turbines or diesel engines on the offshore platform would generate the power for the compressors. But in this case, ABB has deployed its HVDC Light (high voltage direct current) and the VHV Motor (very high voltage) technologies in combination with other generation and transmission solutions to bring power from the Norwegian mainland via a subsea cable to power the compressors.
In May 2005, the Swiss-Swedish engineering company made a presentation at the Offshore Technology Conference in Houston, during which it outlined its plans to explore the use of its HVDC technologies for powering offshore platforms.
ABB said supplying offshore platforms with ‘clean’ energy generated onshore would reduce the overall environmental impact of the oil and gas industries’ offshore operations. Power supplied to the Troll A platform is generated using hydropower, further minimising its environmental impact.
The core components of the ABB HVDC Light system are valves which consist of millions of high power semiconductors. The valves are shielded and suspended from the ceiling in an very compact converter module.
ABB said the semiconductor design allowed less than one failure per 10 million operating hours. HVDC Light is a unique and proven power transmission system, designed to transmit power underground and underwater.
In 2004, ABB was awarded a contract by the Trans-European Network of Energy (TEN-E) to supply its HVDC Light technology for the EstLink project. The technology could deliver up to 350MW efficiently and economically over long distances and in sensitive environments, according to ABB.
Power transmitted via the HVDC Light system powers two 40MW high-voltage ABB VHV Motors to drive the compressor units and associated utilities. ABB said the VHV Motor was also designed with the environment in mind, both through its energy-efficient operations and the use of easily recyclable materials in its construction.
Statoil said it expected the new compressors to increase Troll A’s production from 85 million cubic meters of gas per day to 100 million cmpd.
ABB said that the trial phase had demonstrated several benefits, including ‘zero pollution’ (all electricity used on Troll A is generated by hydropower on the mainland), increased transmission efficiency, longer equipment lifecycles, reductions in maintenance stops and in the number of offshore workers, and a perfect health and safety record on the platform.
“It is a tremendous technological achievement, and one that may well be copied at other platforms in the future as the cost and environmental savings become more widely known,” said ABB Power Technologies Systems head Samir Brikho.
ABB estimated the use of HVDC Light technology to power the platform would eliminate annual emissions of some 230,000 tons of carbon dioxide and 230 tons of nitrogen oxides.
