Sui unary 



Antifouling concrete offers a possible, though largely unproven, 

 option for antifouling protection of OTEC concrete structures. Impregnated 

 porous shale antifouling concrete has the proven advantage of small-scale 

 application techniques and documented antifouling performance, but high 

 initial material costs. On the other hand, polymer concrete materials have 

 the advantage of lower initial material costs and promising antifouling 

 performance, but have not as yet been proven in specific concrete applica- 

 tions. In addition, all of these techniques for imparting antifouling 

 properties to concrete have never been attempted on such a large scale and 

 may require the development of costly specialized application procedures 

 for OTEC. This is especially true in the case of the polymeric materials. 

 However, savings resulting from a low- maintenance, antifouling concrete 

 structure could conceivably render this technique cost effective in the 

 long run. 



MECHANICAL CLEANING 



In-situ mechanical cleaning techniques have been used to remove dense 

 accumulations of fouling from ships when operational ship requirements 

 precluded the use of dry docking and repainting. Due to increasing fuel 

 costs, mechanical hull cleaning has been viewed as a cost-effective means 

 of fouling control. Rapid expansion in the technology of underwater foul- 

 ing removal has given the maritime community several competitive methods 

 from which to choose. The following paragraphs will relate ship underwater 

 cleaning technology to the conceptualized OTEC designs. 



Impact of Plant Design 



The Lockheed Design has certain features which make the system amen- 

 able to in-situ mechanical defouling. The system is not weight critical 

 because the fouling accumulation on exterior surfaces is partially compen- 

 sated by sufficient reserve buoyancy. An examination of the general con- 

 figuration of warm and cold water inlets and outlets leads to the following 

 analysis. Mechanical cleaning of the cold water inlet (this also applies to 

 TRW concept)^ is not being considered; it poses no serious fouling problems. 

 However, the ingestion of large volumes of water may entrap swimming marine 



52 



