Big environmental gains are promised from the use of innovative technology to supply electricity generated on land to compressors being installed on Troll A in the North Sea. This solution eliminates emissions of carbon dioxide and nitrogen oxides from the Statoil platform and its associated gas treatment plant at Kollsnes near Bergen. Turbines would otherwise have been needed offshore to drive the compressors, releasing some 230,000 tons of carbon dioxide and 230 tons of nitrogen oxides annually.
High voltage direct current (HVDC) transmission technology means that electricity can be supplied to Troll A from Kollsnes, where a transformer and DC rectifier are to be installed. Sent to the platform along specially developed DC cables, this power will pass to an alternating current rectifier and special motors. The solution has been used before, explains compression project manager Atle Grung Eide. But this represents its first application to an electrical drive system for compressors. ABB has developed the system in cooperation with Statoil, he adds. "The underlying technology development is a good example of the way industrial collaboration yields results."
A contract to supply and install the submarine power cables and to build the electrical compressor drives has been awarded to ABB by the Troll licensees. Worth roughly NOK 600 million in all, this delivery also covers construction of the transformer and rectifier station at Kollsnes. The new compressors, estimated at approximately NOK 3 billion, are required to offset declining reservoir pressure in Troll as gas production proceeds and to help drive output through the pipelines to land.