Installation Limits of Large Diameter Cold Water Pipes in Deep Water for Land-Based OTEC Plants

Master thesis (2015)

Authors

Contributors

R.H.M. Huijsmans (mentor)
Programme
Offshore and Dredging Engineering (Mechanical, Maritime and Materials Engineering) (TU Delft)
Copyright: © 2015 Keesmaat, K.
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Published Date

21-08-2015

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Programme

Offshore and Dredging Engineering

Abstract

The growing worldwide demand for clean, sustainable electricity generation and improved energy efficiency offers a valuable opportunity for the large scale implementation of OTEC (Ocean Thermal Energy Conversion) and SWAC (Sea Water Air Conditioning). One of the remaining technological challenges for large scale land-based OTEC and SWAC is the installation of the very large diameter (>2.5 m) cold water pipelines (CWPs) in water depths close to 1000 m, which provide the required cold deep seawater supply. Therefore, the aim of this thesis is to find and expand the limits of the installation of very large diameter deep water CWPs. Currently, the largest diameter CWP installed in deep water is a HDPE pipe with a diameter of 1.4 m. The first part of this thesis analyses the limits of the conventional installation method for marine large diameter HDPE pipes. This is done with both an analytical natural catenary model as well as with a FEM Orcaflex model. From this analysis, it can be concluded that the largest diameter HDPE pipe which can be installed using this conventional installation method is not big enough for large scale OTEC. To expand this limit, some minor adjustments are proposed for the conventional installation method, which might slightly increase the installation capabilities. For a significant increase, alternative pipe materials for use with the conventional installation method and completely different installation methods are proposed. Two alternative pipe materials show promising results to expand the limit of the maximum pipe diameter which can be installed. Four very different alternative installation methods are proposed to increase pipeline installation capabilities. Although these methods are all very promising, further detailed analysis is required to assess the true feasibility.