For remote islands with high energy prices in the tropics, Ocean Thermal Energy Conversion (OTEC) can be a reliable energy source to supply a renewable baseload for the energy grid. Also, due to the increasing cooling demand, there is a need for sustainable cooling around the equator. This can be supplied by seawater air-conditioning (SWAC). For the cold water supply of such projects, there is a cold water pipe required that could reach to a depth of up to 1000m. The cold water pipe material that is investi¬gated in this thesis is high-density polyethylene (HDPE). The installation of these large diameter cold water pipes is challenging and requires careful attention, as it is one of the most expensive components of an ocean thermal energy project. A dynamic 3D geometrically non-linear Euler-Bernoulli model is developed that allows for large deformations. In this way, the lowering procedure, including lateral current actions on the pipe can be modelled in order to check the structural integrity of the pipe during installation. The model is validated by comparing it to scale model tests in MARIN, which results in a good comparison between the numerical model and scale model tests. Additionally, the model is compared to a geometrically non-linear Timoshenko beam model to estimate whether shear deformation plays a role for large diameter HDPE pipes. Both models showed a good comparison and the for the bending radii that are of interest, shear deformation is negligible. Making use of the numerical Euler-Bernoulli model, a case study is performed for a seawater air-conditioning project in Curaçao. Different installation methods are compared, where the subsurface cur¬rent velocity is an important parameter. This velocity determines the required amount of ballast of the largest section of the pipeline. For high current velocities, the ballast is high, such that there are multiple holding points required along the pipe in order to make it sink in one piece without exceeding the design stress of HDPE. Ballast can be applied by means of concrete blocks along the pipeline. The pipe can be controlled during installation by either buoyancy modules or vessels with tug lines. Another option is to reduce the specific gravity of the pipe and to apply post ballasting by means of rock dumping. The best solution de¬pends on site specific conditions, where detailed current velocity profiles are desired to choose the most cost effective solution. During installation, the currents will have an impact on the lateral deflection of the pipe, which can lead up to a deflection of several hundreds of meters if no measures are taken. Several vessels are required along the pipeline during installation to make sure the pipe is installed on the planned trajectory.

The main goal of this project is to determine the optimal location for an OTEC installation with a minimum lifespan of 30 years off the coast of Barranquilla and to make an anchor mooring design for the floater on which this installation is located. Bluerise has identified an area near the coast of Barranquilla for which OTEC can be applied. This area is situated within Colombia’s territorial waters (within 12 nautical miles, or 22.2 kilometres), where two locations have been identified by Bluerise: Location 1: 11.2028 latitude, -75.0003 longitude, Location 2: 11.2772 latitude, -74.9208 longitude.

Environmental conditions -
The daily wind direction is NE-ENE. There is no clear extreme wind direction. The daily waves have a dominant Northeast direction while the extreme waves have a dominant Northern direction. The extreme waves are generated far north of Barranquilla by very high wind speeds which explains the relatively high extreme significant wave heights in the area and the relatively low extreme wind speeds. The yearly average (nautical) surface current direction at the two possible floater locations is predominantly south or southeast. The top 20 strongest current speeds in the past few decades have come from the west or southwest however and therefore these are the normative current directions. The environmental conditions are equal for both possible floater locations. A temperature difference of 20_C is reached at warm water intake and cold
water intake depths of 30 and 763 meters, respectively. The depths at which a temperature
difference of 22_C is reached are 36 and 1023 meters (with temperatures of 27 and 5 degrees, respectively). The influence of the Magdalena river and upwelling is concluded to be negligible.

Marine traffic - The two locations with safety zones are located in a traffic-dense area. The area is getting more traffic intense in the upcoming years. However, it will not pose an immediate threat to the operation. As location 2 has slightly less traffic, it would be preferable from a safety point of view.

Seawater intake- and return pipes - Assuming a cold seawater intake temperature of 5C and a warm seawater intake temperature of 27C, the intake pipe lengths become 1023 and 36 meters, respectively. Based on the equation
of state, the mixed water return flow pipe length becomes 130 m. At this depth, the effects of a difference in density between the surrounding seawater and the mixed returned water are minimized. Also, the depth is outside of the euphotic zone which minimizes algae growth. If the intake water is higher than 27 degrees, the discharge temperature will have a higher temperature. Calculations with the Equation of State reveal that the warmer the discharge temperature,
the lower the density of the discharge water is. Whenever the discharge temperature is higher than the output temperatures, less depth is needed in order for the discharge water to be naturally buoyant. As the intake temperature fluctuates throughout the year, it is therefore advised to design the length of the discharge pipe at 120 meters.

Anchor mooring design - The proposed anchor mooring design consists of a spread-moored 4x3 taut mooring system. The lines are composed of three parts: a 50 meter chain connected to the ship, a 1290 meter fibre line part and another 150 meter chain at the end that is connected to the anchor. The floater is positioned in a 58,05 angle with respect to the north in a northeast direction. This ensures comfortable operation during daily conditions and will reduce fatigue build up. The hurricane conditions were found to be governing. The design complies with the basis of design stated in section 5.3 and with the DNV-OS-E301 code and the API Recommended Practice 2SK.

To tackle the expected increase in fresh water shortage in the world, alternative water production methods are required. One such a possible method is Ocean Thermal Water Production (OTWP). This thesis continues on the innovative concept of the use of OTEC waste water as a cooling fluid for atmospheric water production introduced in previous work. In this thesis, an experimental study on a structured packed bed condenser column is presented. This work was carried out on an experimental OTWP set-up installed in the Process & Energy lab at the Delft University of Technology. Additionally, a numerical Python model was used to investigate the heat transfer and condensation characteristics of the packed bed column. The condenser function of the Python model was used to compare the prediction performances of different mass transfer coefficient and hydraulic correlations. The Python model simulations were compared both to the predictions of Aspen plus, an established chemical process software, and to the experimental results. The correlation by Olujic et al. (1999) was chosen as the most suitable for the transfer rate and hydraulic behavior predictions for the Python condenser model. A mean average error in the mass transfer predictions of 2.5 % and in the hydraulic predictions of 16.9% was reached in relation to the experiments. outperforms the Aspen plus model, that has respective mean average errors for the mass and pressure drop predictions of 9.5% and 13.0 % for the correlation proposed by Rocha et al. (1993). The Python model was extended with functions that calculate the pressure drop over the remaining necessary equipment for an OTWP plant. The aim of the developed model was to predict the processes in the OTWP condenser column and design a pilot-plant. The model was used to perform a sensitivity analysis on a large-scale column. A preliminary economic analysis identified that reducing the diameter of the condenser column reduces the cost of water production but increases the energy requirement. For an OTWP pilot-plant with a production of 25 m3/day, the chosen column diameter of 6.6 m leads to a system energy requirement of 3.5 kWh/m3 and a levelized cost of water production of 8.08 $/m3. Those production costs can be reduced by an optimization study of the full OTWP pilot-plant.

Many regions in the world depend heavily on expensive desalinated water for fresh water consumption, in particular tropical areas. Current mainstream desalination technologies (Reverse Osmosis and Multi-Stage Flash Evaporation) are quite energy intensive and thus costly. Today’s challenge is to design a desalination system that could run with local available renewable energy and provide affordable fresh water, even in the most arid environments. A potential fresh water production method that differs from mainstream technologies is Ocean Thermal Water Production (OTWP). This method makes use of high temperature and high relative humidity air in the tropics and condenses it against a cooled fresh water loop in a packed bed column. The system is expected to deliver fresh water at a competitive level once built at a larger scale. This master thesis project improves a previously researched OTWP model and validates the model by testing its output values against experiments done using an experimental setup at the TU Delft P&E laboratory. Taking into account the previous work done during the thesis of van der Drift [49] and Lopez [30], the theoretical background for building an OTWP model has been further described and expanded in this thesis. Three different direct contact condensation theories have been thoroughly examined. The first two theories suggest that heat and mass in the DCD are transferred through a constant laminar film on the packing [38] [1] [4]. The third theory is an add on to the laminar film model, and suggests that heat and mass is also transferred through the creation and dynamics of small droplets within packings [34]. The model and its 4 main submodels are fine-tuned to be able to reproduce the thermodynamics occurring in the experimental setup. The model is tested under different steady state conditions using experiments, to provide insight on the model’s robustness and reliability. The final improved simulation model is used to present conclusions on heat transfer, mass transfer and water production rates for the experimental setup. A brief economic analysis of the system is performed to arrive at an energy price of water for the OTWP experimental system. Although the final energy price for the OTWP setup is quite unfavorable, 14 kWh/m3 as opposed to 2-3.5 kWh/m3 for current desalination systems, tips to improve a possible future pilot facility are proposed. Here high yield and low cost are key requirements, and the design of a future pilot facility needs to be optimized using these two pillars.