Thermoelectric generator for underwater wellhead

DCN CHERBOURG, the French submarine builder, has a great deal of experience in underwater equipment. The company also has experience in thermoelectric technology which is used in submarines for cooling systems. In light of this experience, DCN CHERBOURG was contacted by an oil company in order to develop a thermoelectric generator for an offshore subsea application The requirements were: (i) a thermogenerator able to be inserted as a spool in a submarine pipeline; (ii) site: North Sea (sea water temperature=4/spl deg/C); and (iii) fluid: mix of oil and gas, temperature between 90/spl deg/C and 120/spl deg/C, pressure 450 bar. The design began with thermoelectric module tests (electrical, thermal and mechanical). The objective was to select the type of thermoelectric module and the assembly system. The ceramic technology from MELCOR was chosen. DCN CHERBOURG then made and tested a prototype. The performance results were not as good as expected, however, the prototype proved that a thermoelectric generator for an offshore subsea application was feasible. The next step was the assembling of two thermogenerators (THEGS) for an offshore application. The performance measurements obtained during on-shore testing were as expected: about 100 W at 70 V.