Ocean thermal energy conversion (OTEC), is a renewable energy resource that uses the thermal gradient of the ocean to generate electricity. Warm surface water and cold deep sea water, which can be found at depths of approximately 1000 [m], are used to generate electricity in a thermodynamic Rankine cycle. Due to its dimensions, the installation of the cold water pipeline is one of the most challenging aspects of an OTEC plant. Allseas Engineering B.V. is planning to install a 3 [MW] onshore based OTEC plant on Bonaire. For this OTEC plant, a cold water pipeline with an outer diameter of 2.25 [m] is required that pumps up water from 950 [m] water depth. High density polyethylene (HDPE) is used as the material for the pipeline. HDPE is buoyant and therefore requires additional downwards force to be installed below the sea surface. Two installation methods are considered for this cold water pipeline: the ‘hold and sink installation method’ and the ‘pull down installation method’. A numerical non-linear Euler Bernoulli beam model is used to optimize both installation methods. The Von Mises stress criterion is used to assess whether the structural integrity is maintained during the installation.
The hold and sink pipeline is ballasted using concrete ballast weights to provide the necessary downwards force. The seabed stability criterion is used to determine the required amount of ballast. Hold points are attached along the length of the pipeline that provide a vertical upwards force to control the sinking velocity. A pull force is applied at the offshore end to reduce pipeline bending stress and to reduce the lateral deflection that results from the sea current. Using the hold and sink installation method, the pipeline can be successfully installed without exceeding the design stress.

The pull down installation pipeline is divided into two sections: a ballasted section of 450 [m] and the remainder of the pipeline that remains afloat. A concrete ballast weight is installed at the seabed, at the final position of the offshore end of the pipeline. The ballasted section is installed using an installation method that is frequently used for HDPE pipelines called the float and sink method. A chain is connected to the offshore end of the pipeline. The chain is connected to a pull cable that runs through the anchor box at the seabed to a crane vessel at the sea surface. The unballasted section is then pulled down to the anchorbox, where the chain is secured in the anchorbox and the pipeline remains in a reversed catenary shape during its operational life. In the transition zone where the transition between the ballasted section and the floating section of the pipeline occurs, the Von Mises stress exceeds the design stress. The Von Mises stress results primarily from pipeline bending, therefore additional bending stiffness is applied in the transition zone. The maximum pull force is limited to the weight of the anchorbox. The required pull force to install the pipeline exceeds the allowed pull force. Additional ballast weights are attached to the free span of the pipeline to reduce the required pull force. The pipeline can be installed without exceeding the design stress when the bending stiffness in the transition zone is increased and the required pull force is reduced.
A preliminary multi-criteria analysis is conducted as an initial comparison between the two installation methods. From this analysis no obvious preferred installation method can be selected. A recommendation is made to expand this preliminary multi-criteria analysis and include a detailed cost estimation of the installation methods. Furthermore, it is recommended to include a detailed operational lifetime analysis on the structural integrity of the pipeline for both installation methods.

The purpose of the research is to provide insight into the conversion of a second-hand vessel into an Ocean Thermal Energy Conversion (OTEC) plant. To this end, a 10 MW ship-shaped OTEC platform, located in the waters around Curaçao, has been designed.
At present, only a few of OTEC plants are in operation, primarily with the purpose of research and development. These projects consist of small scale onshore platforms, the biggest of which produces a maximum of 100 kW of continuous electricity. The lack of existing large oshore OTEC installations, together with the time frame of the project, limit the project to a concept design. Ultimately, the report will serve as a guideline for the implementation of ship-shaped OTEC platforms.
The use of Systems Engineering (SE) has been motivated by the need to establish a clear structure to address effectively the challenges posed by the complexity of the installation. This methodology facilitates the revision of the performance of the ship-shaped OTEC throughout the design process.
From the initially defined Top Level Requirements (TLRs) a plant architecture has been developed, covering the engineering of the power plant, selection of mooring system and dimensioning of the second-hand Panamax bulker to be converted. The research has brought forward the main drivers of the design: process ducting, water pipes and, particularly, heat exchangers. As a result, the integration of process equipment, mooring system and hull has rendered an optimized platform layout.
The proposed solution was, then, assessed with regards to the utilization of space on board and the stability of the hull. While the ratio of occupied versus empty space is deemed adequate, it is necessary to add ballast water to increase the draft and the use of alternative solutions, such as bilge keels or fixed ballast in the top side tanks, to dimish the excess of stability of the hull.
Overall, the findings of the research suggest that the construction and operation of a ship-shaped OTEC plant is feasible. Nevertheless, a holistic validation demands for the incorporation of all new components, followed by structural and hydromechanic analysis of the platform. Lastly, it is recommended to study the use of different heat exchanger types and power ouputs that could derive in more space-efficient
design.

In the present global scenario of a fossil fuel based economy, excessive use of non- renewable resources, such as petroleum, coal and natural gas has resulted in global warming, extreme weather events, and biodiversity loss. Therefore, the need for social, environmental and economic change is still dominant around the world and many places including the Netherlands, are proposing different alternatives to mitigate the increasing anthropogenic impact.
Our Oceans with thermal energy basins covering more than 70% of our planet’s surface are noticeably the largest solar collector. Ocean Thermal Energy Conversion (OTEC) technology provides the means of harvesting this vast potential to offer a steady baseline power generation for coastal cities and regions where most of the World’s population is currently living. Nonetheless, since the nature of OTEC resources depends significantly on location-based indicators, an explicit focus has been put on this study towards the collection and examination of spatial information.
Nevertheless, cold water availability in 1 km depth, constraints the total amount of electricity that could be extracted by OTEC operations. For this reason, an advanced analysis below is performed which redefines the magnitude of the resources for the development of a realistic OTEC deployment scenario which can still cover the entire electricity demand of the world.
In total, the Offshore and Onshore OTEC power produce can reach up to 4.4 TW with a deep seawater flow rate of wcw=175 m/yr without causing any thermal disruptions in the ocean. Therefore, countries such as Indonesia, Papua New Guinea, Dominica, Mozambique, U.S., Indonesia, etc that have a great abundance of OTEC resources, could even exchange this power produce through a symbiotic relationship to uplift their economy andmake a step closer towards the forthcoming renewable energy transition.