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Anthropogenic activities and their influences on aquatic systems is an important topic, especially considering the growing interest in using the earth's resources in a sustainable way. One of those anthropogenic activities is the introduction of renewable technologies into the aquatic environment such as instream turbines. Environmental studies around those technologies are often still ongoing due to their novelty. During the spring of 2018, juvenile individuals of two salmonid species, Atlantic salmon and brown trout were released upstream a vertical axis instream turbine in the river Dal (Dalälven) in eastern Sweden. The aim of this study was to investigate the swimming behavior of the salmonids around a small-scale prototype vertical axis instream turbine. The swimming pattern and the possible response of avoiding the vertical axis instream turbine were documented with a multi beam sonar. A control area, next to the turbine, was used as reference. No consistent results were shown for trout as they were passing the control area with a statistically high variation, and specimens were rarely observed in proximity of the turbine, neither if the turbine was operating nor at stand still. Salmon clearly avoided the operating turbine, but did not avoid the turbine when it was at stand still, and was often observed swimming straight through the turbine area. These findings indicate that operating this type of instream turbine in a river affects the swimming behavior of Atlantic salmon but is unlikely to affect its migration paths. For brown trout, the statistical results are inconclusive, although data indicate a response of avoiding the turbine. The species are in little risk to suffer physical harm as no fish entered the rotating turbine, despite very turbid water conditions.

Decarbonization of ports is a major goal to reduce their global carbon footprint. The port of Hvide Sande is located on the coast of the North Sea in Denmark and it has the potential to utilize various renewable energy sources. Wind and solar thermal parks are already installed there. Wave energy is an alternative to solar and wind energies and its advantage is the spatial concentration, predictability, and persistence. Heat to the town is provided by Hvide Sande Fjernvarme. In this work, it is investigated if the heat demand could be fully covered by renewable energies. Power profiles for each renewable energy resource were calculated using 30 years of re-analysis environmental data. Long, mid, and short term time series of power supply has been statistically and quantitatively examined. Considering the heat demand of Hvide Sande, the lowest frequency of zero occurrence in power generation can be ensured by the combination of wind, solar energy and wave. The article also estimated the capacity for Lithium-ion batteries. The optimal size of the battery is found by the bisection method. Finally, different combinations of renewable energy and demand as well as batteries are evaluated. The lowest zero occurrences in power production is met by the mix of three renewable energies. Also, the mix of three renewable energies significantly reduces the value of energy, required from the battery.

Environmental data is crucial for planning, permitting, execution and post construction monitoring of marine renewable energy projects. In harsh conditions in which marine renewable energy is harvested, integrated monitoring platforms comprising multibeam imaging sonar systems coupled with other sensors can provide multi-dimensional data of the marine environment surrounding marine renewable energy installations. The aim of this study was to test the possibilities of observing the occurrence of fish and marine mammals using a multibeam imaging sonar system deployed at a wave power test site. The results obtained from a ten-day data set proved the platform as suitable for long time underwater monitoring and also revealed that the occurrence of fish and marine mammals was distributed across characteristic time and space domains. Large fish [>0.4 m] frequently occurred at night-time and near the benthic zone. Small fish [<0.2 m] frequently occurred during daylight and within the pelagic zone. The occurrence of seals was periodically distributed along a daily cycle, with intervals of 1 – 2 hours between maxima and minima. In conclusion, the use of multibeam imaging sonar can be a reliable technique for the qualitative and quantitative observations of fish and marine mammals in general and at marine renewable energy sites specifically, including protected and economically important species.

Techniques for marine monitoring have evolved greatly over the past decades, making the acquisition of environment data safer, reliable and more efficient. On the other hand, the exploration of marine renewable energy introduced dissimilar ways of exploring the oceans and with that arises the need for new techniques for environmental data acquisition, processing and analysis. Marine energy is mostly harvested in murky and high energetic places where conventional data acquisition techniques are impractical. Modern sonar systems, operating at high frequencies, can acquire detailed images of the underwater environment. Variables such as occurrence, size, class and behaviour of a variety of aquatic species of fish, birds, mammals, coexisting within marine energy sites can be gathered using imaging sonar systems. Although sonar images can provide high level of details, still in most of the cases they are difficult to decipher. Therefore, to facilitate the classification of targets through sonar images, this study introduces a framework of extracting visual features of marine targets that would serve as unique signatures. The acoustic measure of visibility (AVM) is here introduced as an indirect technique of identification and classification of targets by comparing the observed size with a standard value. This information can be used to instruct manual and automatic algorithms for identification and classification of underwater targets using imaging sonar systems. Using image processing algorithms embedded in Proviwer4 and FIJI software, this study found that acoustic images can be effectively used to classify cod, harbour and grey seals, and orcas through their size, shape and swimming behaviour. Data showed that cod occurred as bright, 0.9 m long, ellipsoidal targets shoaling in groups of up to 50 individuals. Harbour seals occurred as bright torpedo-like fast moving target, whereas grey seals occurred as bulky-ellipsoidal targets with serpentine movement. Orca or larger marine mammals occurred with relatively low visibility on the acoustic images compared to their body size which measured between 4 m and 7 m. This framework provide a new window of performing qualitative and quantitative observations of underwater targets, and with further improvements, this method can be useful for environmental studies within marine renewable energy farms and for other purposes.

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.

Freshwater scarcity is one of humanity's reoccurring problems that hamper socio-economic development in many regions across the globe. In coastal areas, seawater can be desalinated through reverse osmosis (RO) and transformed into freshwater for human use. Desalination requires large amounts of energy, mostly in the form of a reliable electricity supply, which in many cases is supplied by diesel generators. The objective of this work is to analyze the wave power resource availability in Kilifi-Kenya and evaluate the possible use of wave power converter (WEC) to power desalination plants. A particular focus is given use of WECs developed by Uppsala University (UU-WEC). The results here presented were achieved using reanalysis-wave data revealed that the local wave climate has an approximate annual mean of 7 kW/m and mode of 5 kW/m. Significant wave height and wave mean period are within 0.8-2 m and 7-8 s respectively, with a predominant wave mean direction from southeast. The seasonal cycle appeared to be the most relevant for energy conversion, having the highest difference of 6 kW/m, in which April is the lowest (3.8 kW/m) and August is the peak (10.5 kW/m). In such mild wave climates, the UU-WEC and similar devices can be suitable for ocean energy harvesting for water desalination systems. Technically, with a capacity factor of 30% and energy consumption of 3 kWh/m(3), a coastal community of about five thousand inhabitants can be provided of freshwater by only ten WECs with installed capacity of 20 kW.

A continued expansion of the marine renewable energy sector will result in an increased demand in monitoring the natural marine environment. This may be due to a basic scientific interest but is foremost linked to the requirement of pre- and post-construction studies in relation to environmental impact assessments and consenting processes for marine renewable energy projects. With focus on wave and tidal power, but without attempting to provide a comprehensive list, we review methods, technologies and other scientific tools used for monitoring and predicting possible impacts from marine energy installations, on both population and behavioural levels. This includes traditional methods such as fishing gear, like nets and cages, modern technologies such as platforms with multi parameter equipment and the use of deterministic models. This paper is intended to serve as an overview for technology developers as well as authorities, regulators and decision makers with interests in general techniques, and naturally for scientists and consultants commonly being executors of studies and monitoring programs. By giving relevant and up to date references this paper may also be useful for finding more detailed information on study methods and variants. Finally, we give recommendations on where development of technologies is needed in order to face future requirements.

With the prospect to deploy hydrokinetic energy converters in areas with heavy boat traffic, a study was conducted to observe and assess the depth range of cavitating flow produced by ferryboats in narrow channels. This study was conducted in the vicinity of Finnhamn Island in Stockholm Archipelago. The objectives of the survey were to assess whether the sonar systems were able to observe and measure the depth of what can be cavitating flow (in a form of convected cloud cavitation) produced by one specific type of ferryboats frequently operating in that route, as well as investigate if the cavitating flow within the wake would propagate deep enough to disturb the water column underneath the surface. A multibeam and a dual-beam sonar systems were used as measurement instruments. The hypothesis was that strong and deep wake can disturb the optimal operation of a hydrokinetic energy converter, therefore causing damages to its rotors and hydrofoils. The results showed that both sonar system could detect cavitating flows including its strength, part of the geometrical shape and propagation depth. Moreover, the boat with a propeller thruster produced cavitating flow with an intense core reaching 4 m of depth while lasting approximately 90 s. The ferry with waterjet thruster produced a less intense cavitating flow; the core reached depths of approximately 6 m, and lasted about 90 s. From this study, it was concluded that multibeam and dual-beam sonar systems with operating frequencies higher than 200 kHz were able to detect cavitating flows in real conditions, as long as they are properly deployed and the data properly analyzed.

Human exploration of the hydrosphere is ever increasing as conventional industries grow and new industries emerge. A new emerging and fast-growing industry is the marine renewable energy. The last decades have been characterized by an accentuated development rate of technologies that can convert the energy contained in stream flows, waves, wind and tides. This growth benefits from the fact that human society has become notably aware of the well-being of the environment that we all live in. This brings a human desire to implement technologies which cope better with the natural environment. Yet, this environmental awareness poses difficulties in approving new renewable energy projects such as offshore wind, wave and tidal energy farms. Lessons have been learned that lack of consistent environmental data can become an impasse when consenting permits for testing and deployments marine renewable energy technologies. An example is the European Union in which a majority of the member states requires rigorous environmental monitoring programs to be in place when marine renewable energy technologies are commissioned and decommissioned. To satisfy such high demands and to simultaneously boost the marine renewable sector, long-term environmental monitoring framework that gathers multi-variable data are needed to keep providing data to technology developers, operators as well as to the general public. Technologies based on active acoustics might be the most advanced tools to monitor the subsea environment around marine manmade structures especially in murky and deep waters where divining and conventional technologies are cost.

The main objective of this PhD project has develop and test an active acoustic monitoring system for offshore renewable energy farms, by integrating a multitude of appropriate monitoring sonar, hydrophones and cameras systems to be developed with standards suitable for subsea environmental monitoring. In this project, a first task was to identify, secondly acquire and test sonar systems, then a platform was designed and built, a data acquisition device control systems were developed, finally additional instruments such as video cameras and sonars were added. This systems integration followed by calibration of devices was conducted. The sonar systems were used for quantitative measurements of the occurrence of e.g. large marine animals and schools of fish near marine renewable energy converters. The sonar systems were also used for seabed inspections, depth measurements and capitating flow observations.

So far, the combination of multibeam and dual-beam sonar systems produced good results of target detection, bottom inspection, depth measurements and biomass estimation. The multibeam sonar system was capable of resolving isolated targets located near high acoustic retroreflective objects. Panoramic acoustic images of wave and instream energy converters were acquired using a multibeam sonar operating at frequencies near 1 GHz. The Dual-beam and split-beam sonar systems produced data referent to acoustic background intensity of targets that helps to classify targets according to its size, composition and 3-Dimensional location within the water column. The next phase of this project will deploy the platform for longer periods in order to gather consistent acoustic and optical backscattering data of marine animal behaviour within marine renewable energy farms.