Technical and economic feasibility analysis of a horizontal axis tidal turbine when operating in low velocity conditions

Current global warming requires the de-carbonisation of electricity production with the use of renewable energy sources. This thesis assessed if the economically feasible tidal stream known locations could be expanded with the use of a modified Horizontal Axis Tidal Turbine (HATT) . Cardiff Marine Energy Research Group’s (CMERG) well characterised HATT, designed to operateinhighvelocities(6knots),wasadaptedtooperateinlowvelocityconditions(≤1.2m/second). Using the Gulf of Nicoya site’s conditions in Costa Rica for reference, the analysis was made with Computational Fluid Dynamics (CFD) using the ANSYS CFX, and ICEM packages. Initially, the 5m radius rotor’s geometry was changed using the rotor solidity parameters. Ten single rotor turbine (SRT) configurations were modelled, and the pitch angle at which they had the maximum power output was found for all geometries. From the results, a solidity based performance prediction tool was proposed for SRTs. Using the SRT results, a contra-rotating rotors turbine (CRT) matching and selection process was proposed. The procedure considered the SRT geometry characteristics, their torque and power output, rotational velocities, blade interference, and estimated cost. A CRT was modelled withCFDtovalidatethepredictionvalues,andresultsshowedthattheexpectednetperformance characteristics were not obtained but the technical restrictions were kept during operation. Finally, an economic study based on the levelised cost of energy (LCOE) was made to determine the CRT’s feasibility when operating in the set conditions. It was found that, though technically feasible, the proposed modifications would not make the SRT nor the CRT economically feasible to compete, currently, in the renewable energy market in the UK and Costa Rica. Based on the results, cost reduction opportunities were given for the device to be en par with commercially ready technologies