Dossier Océan et énergie - Énergie Thermique des Mers
Sommaire IOA News Letters
DESIGN OF A 5MW OTEC PRE-COMMERCIAL PLANT
Luis Vega and Gerard Nihous
The technical and economic evaluation of OTEC plant and their potential environmental impact assessment indicate that their commercial future lies in floating plants of approximately 100 MWe capacity and that their commercial development is impaired by the lack of operational data. Unfortunately the data available from small experimental plants is not applicable to commercial size plants. A scaled version of a commercial size plant must be designed and operated to established the life cycles of major components and yearly production rates prior to commercialization. Considering a modular design a 1/5 scaled version of a 25 MWe module is proposed as an appropriate size.
The power block of the 5MWe pre-commercial OTEC plant is based on a closed cycle with its effluent water streams used in a second stage for the production of desalinated water with flash evaporators and surface condensers developed for the open cycle. The 26 cu m/s and 14 cu m/s flowrates of warm and cold seawater are supplied using validated technologies. The 1,000m long 2.74m i.d. fiber-reinforced-plastic cold water pipe is attached to a gimbal at midship. The plant is housed in a 33,000 tonne ship moored 10 km offshore with a counterweight-articulated-mooring (CAM) system developed by IMODCO, with the addition of four azimuthal thrusters for extreme environmental conditions and propulsion. The electricity is transmitted to shore via a submarine power cable and the desalinated water via a flexible pipe with their risers attached to the CAM.
Performance specifications for the power and water cycle components were developed to identify potential suppliers. It was determined that all major components are available. This information, along with the evaluation of potential sites throughout the world, indicates that several industrialized nations could benefit from the commercialization of OTEC and some of them along with numerous less developed nations are potential users of OTEC power and water plants.
It is postulated that a consortium, funded by the governments of the industrialized nations that would benefit from the commercialization of OTEC, be formed to design and operate the 5MWe pre-commercial plant.