OTEC Advanced Composite Cold Water Pipe: Final Technical Report

Abstract

and 1-page Executive SummaryOcean Thermal Energy Conversion can exploit natural temperature gradients in the oceans to generate usable forms of energy (for example, cost-competitive baseload electricity in tropical regions such as Hawaii) free from fossil fuel consumption and global warming emissions.The #1 acknowledged challenge of constructing an OTEC plant is the Cold Water Pipe (CWP), which draws cold water from 1000m depths up to the surface, to serve as the coolant for the OTEC Rankine cycle. For a commercial-scale plant, the CWP is on the order of 10m in diameter. This report describes work done by LMSSC developing the CWP for LM MS2 New Ventures' emerging OTEC business. The work started in early 2008 deciding on the minimum-cost CWP architecture, materials, and fabrication process. In order to eliminate what in previous OTEC work had been a very large assembly/deployment risk, we took the innovative approach of building an integral CWP directly from the OTEC platform and down into the water. During the latter half of 2008, we proceeded to a successful small-scale Proof-of-Principles validation of the new fabrication process, at the Engineering Development Lab in Sunnyvale.During 2009-10, under the Cooperative Agreement with the US Dept. of Energy, we have now successfully validated key elements of the process and apparatus at a 4m diameter scale suitable for a future OTEC Pilot Plant. The validations include:•Assembly of sandwich core rings from pre-pultruded hollow "planks," holding final dimensions accurately •Machine-based dispensing of overlapping strips of thick fiberglass fabric to form the lengthwise-continuous face sheets, holding accurate overlap dimensions •Initial testing of the fabric architecture, showing that the overlap splices develop adequate mechanical strength (work done under a parallel US Naval Facilities Command program) •Successful resin infusion/cure of 4m diameter workpieces, obtaining full wet-out and a non-discernable knitline between successive stepwise infusions.After an introductory section describing the background and initial work, the major sections of this report describe (mostly by graphical means) the results of these validations at 4m scale. Within each section, the key results, evidence, and future improvements are summarized concisely in tables.The last section of this report describes future plans to complete the CWP risk retirement and implementation.An extended Executive Summary at the end provides the key results from this work at the level of one photo montage and one • Can we use an off-the-shelf composite fabrication process?• Various possible liquid resin infusion processes as applied to vertical stepwise molding of a CWP • VARTM -A quick summary tutorial • VARTM of a large wind turbine blade shell • Recent applications of large-scale VARTM technology • CWP processing steps using stepwise VARTM • Tooling strategy • Elements of VARTM that are "tweaked" for our application • Holding, lowering, and supporting the CWP during on-the-water fabrication 20...

Ocean Thermal Energy Conversion: Technological Readiness and Indonesia Progress

“…The failure occurred because the geography of the proposed site, which consists of a gentle underwater slope, would not allow the pipe to be laid all the way as planned. Problems with the CWP also led to the abandonment of the OTEC project in the port of Bengal, India (Avery & Wu, 1994;Miller & Ascari,, 2011).…”

Hydrodynamic Load Effect on Composite Polymer Cold-Water Pipe Joint in Ocean Thermal Energy Conversion

“…The challenge in building an OTEC power plant is the construction of cold-water pipes or the term Cold Water Pipe (CWP), which functions to drain cold water to the surface from sea depths ranging from 500-1000 m [5][6][7][8][9][10][11][12], with a pipe diameter of about > 4 m [13,14]. Pipe materials suitable for cold water pipes based on the above requirements are pipes made of thermoplastic polymer materials and polymer matrix composites because polymer materials are light and insulating.…”

“…Pipe materials suitable for cold water pipes based on the above requirements are pipes made of thermoplastic polymer materials and polymer matrix composites because polymer materials are light and insulating. Of the various types of polymer materials, HDPE is the most appropriate to use [15,16], because HDPE is more flexible, lighter, and has lower electrical conductivity than heavier PVC and polyester materials with high conductivity even though it is flexible [17,18].…”

“…OTEC requires expensive capital investment and operating costs compared to other energy resources, large diameter pipelines are submerged about one mile below sea level [9]. Lockheed Martin Corporation is researching the development of CWP with a diameter of 4 m with long fibre composite HDPE materials, manufacturing is carried out by an adhesive process for joining HDPE sheets and a resin infusion moulding process for bonding HDPE sheets with long fibres [15,28].…”

“…HDPE polymer is highly recommended for application as a CWP material in OTEC installations [13,16]. The use of short-fibre HDPE composites makes it easier for the FSW process to combine joint bonds compared to long fibres.…”