Adapting sonar systems for monitoring ocean energy technologies

Sammanfattning: The global energy sector is under profound reforms aiming towards renewable energy sources, clean technologies and expansion of smart grids, all with the additional aim of providing affordable and dependable electricity for everyone. A reduction of carbon dioxide emissions is a priority on the global agenda, and to achieve that, cleaner energy technologies has to be more integrated into the energy mix. This thesis focus on a sustainable implementation of wave, tidal and offshore wind power, wherefore there is a need to investigate more about the prerequisites and consequences ocean energy can have on the marine environment. For that, reliable, cost effective and continuous environmental monitoring framework is necessary in order to support and safeguard ocean energy operations.The main objectives of the research presented in this thesis are to develop a multifunctional environmental monitoring platform based on sonar systems for ocean energy applications, by adapting high resolution multibeam, dual beam and split beam sonar systems and also underwater cameras; Propose data acquisition and processing protocols capable of decipher sonar data in order to provide continuous environmental monitoring and reporting; Conduct qualitative and quantitative observations of fish and marine mammals using the built monitoring platform; And investigate the feasibility of utilizing the Uppsala University wave energy converter technology to generate electricity worldwide. As a result, a multifunctional platform was designed, built and tested. This included the hardware, the data acquisition system, and a data analysis framework comprising new algorithms necessary to process the new acoustic data. The multibeam, dual beam, and split beam sonar systems and underwater cameras produced both qualitative and quantitative data of biomass, occurrence and behavior of fish and marine mammals in the vicinity of ocean energy devices. With this platform, it was also possible to conduct seabed and structural inspections within ocean energy devices, observe cavitating flows, etc. One of the most important results of this research was the possibility of extracting visual signatures of fish and marine mammals through acoustic images. This can be valuable for training algorithms for manual or automatic identification and classification of underwater targets through imaging sonar systems, a technique that can be widely used in the offshore activities. Regarding feasibility studies and wave power resource assessment, this study concluded that mild wave climates can provide enough energy to run reverse osmosis desalination systems as well as produce sufficient electricity to integrate into a national grid.In summary, this thesis concludes that the implementation of ocean energy can be facilitated by creating environmental monitoring, risk and resource assessment frameworks such as the presented research work that contribute to lowering the risks associated with subsea work and thereby costs of ocean energy projects.