Ocean currents are an attractive source of clean energy due to their inherent reliability, persistence and sustainability. The Gulf Stream system is of particular interest as a potential energy resource to the United States with significant currents and proximity to the large population on the U.S. east coast. To assess the energy potential from ocean currents for the United States, the characterization of ocean currents along the U.S. coastline is performed in this dissertation. A GIS database that maps the ocean current energy resource distribution for the entire U.S. coastline and also provides joint velocity magnitude and direction probability histograms is developed. Having a geographical constraint by Florida and the Bahamas, the Florida Current has the largest ocean current resource which is fairly stable with prevalent seasonal variability in the upper layer of the water column (~200m). The core of the Florida Current features higher stability than the edges as a result of the meandering and seasonal broadening of the current flow. The variability of the Gulf Stream significantly increases as it flows past the Cape Hatteras. The theoretical energy balance in the Gulf Stream system is examined using the two-dimensional ocean circulation equations based on the assumptions of the Stommel model for quasi-geostrophic subtropical gyres. Additional turbine drag is formulated and incorporated in the model to represent power extraction by turbines. Parameters in the model are calibrated against ocean observational data such that the model can reproduce the volume and kinetic energy fluxes in the Gulf Stream. The results show that considering extraction over a region comprised of the entire Florida Current portion of the Gulf Stream system, the theoretical upper bound of averaged power dissipation is around 5.1 GW, or 45 TWh/yr. If the extraction area comprises the entire portion of the Gulf Stream within 200 miles of the U.S. coastline, the theoretical upper bound of averaged power dissipation becomes approximately 18.6 GW or 163 TWh/yr. The impact of the power extraction is primarily constrained in the vicinity of the turbine region, and includes a significant reduction of flow strength and water level drop in the power extraction site. The turbines also significantly reduce residual energy fluxes in the flow, and cause redirection of the Gulf Stream. A full numerical simulation of the ocean circulation in the Atlantic Ocean is performed using Hybrid Coordinate Ocean Model (HYCOM) and power extraction from the Florida Current is modeled as additional momentum sink. Effects of power extraction are shown to include flow rerouting from the Florida Strait channel to the east side of the Bahamas. Flow redirection is stronger during peak summer flow resulting in less seasonal variability in both power extraction and residual fluxes in the Florida Current. A significant water level drop is shown at the power extraction site, and so is a slight water level rise along the coasts of Florida and the Gulf. The sum of extracted power and the residual energy flux in the Florida Current is lower than the original energy flux in the baseline case, indicating a net loss of energy reserve in the Florida Current channel due to flow redirection. The impact from power extraction on the mean flow field is concentrated in the near field of the power extraction site, while shifts in the far flow field in time and space have little impact on the overall flow statistics.

This thesis examines methods for designing and analyzing kinetic turbines based on blade element momentum (BEM) theory and computational fluid dynamics (CFD). The underlying goal of the work was to assess the potential augmentation of power production associated with enclosing the turbine in an expanding duct. Thus, a comparison of the potential performance of ducted and non-ducted turbines was carried out. This required de ning optimal turbine performance for both concepts. BEM is the typical tool used for turbine optimization and is very well established in the context of wind turbine design. BEM was suitable for conventional turbines, but could not account for the influence of ducts, and no established methodology for designing ducted turbines could be found in the literature. Thus, methods were established to design and analyze ducted turbines based on an extended version of BEM (with CFD-derived coe cients), and based on CFD simulation. Additional complications arise in designing tidal turbines because traditional techniques for kinetic turbine design have been established for wind turbines, which are similar in their principle of operation but are driven by flows with inherently different boundary conditions than tidal currents. The major difference is that tidal flows are bounded by the ocean floor, the water surface and channel walls. Thus, analytical and CFD-based methods were established to account for the effects of these boundaries (called blockage effects) on the optimal design and performance of turbines. Additionally, tidal flows are driven by changes in the water surface height in the ocean and their velocity is limited by viscous effects. Turbines introduced into a tidal flow increase the total drag in the system and reduce the total flow in a region (e.g. a tidal channel). An analytical method to account for this was taken from the eld of tidal resource assessment, and along with the methods to account for ducts and blockage effects, was incorporated into a rotor optimization framework. It was found that the non-ducted turbine can produce more power per installed device frontal area and can be operated to induce a lesser reduction to the flow through a given tidal channel for a given level of power production. It was also found that by optimizing turbines for array con gurations that occupy a large portion of the cross sectional area of a given tidal channel (i.e. tidal fences), the per-device power can be improved signi cantly compared to a sparse-array scenario. For turbines occupying 50% of a channel cross section, the predicted power improves is by a factor of three. Thus, it has been recommended that future work focus on analyzing such a strategy in more detail. / Graduate

Wave resource assessment is the collection of site-specific meteorological data to estimate the wave potential in a region and is carried out to mitigate the risks involved in the setup of wave energy converters. Wave resource assessment has been typically done using wave buoys. But wave buoys are expensive and require constant maintenance for smooth operation. An alternative to wave buoys is numerical wave modelling. Numerical wave modelling uses mathematical models to generate computer simulations that describe wave parameters in a region. This project is carried out in the region of Hvide Sande, a western port city of Denmark situated in the North Sea. Wave resource assessment is conducted for this region using the SWAN numerical wave model. The data from a wave buoy in the region is used to perform comparative analysis, in order to study the SWAN wave model and to compare the accuracy of the wave data between the measured buoy and the calculated model. The accuracy of the numerical predictions is further quantified by using a correlation coefficient and the relative square root error. This is followed by a scatter diagram for the region to find the most frequent sea states. The corresponding energy flux of the most frequent sea states was found to be in the range of 1-5 kW/m and the highest energy flux for the area is about 40 kW/m for the region.

The New European Wind Atlas (NEWA) was developed with an aim to provide high accuracy wind climate data for the region of EU and Turkey. Wind industry always seek for solid performance in wind resource assessment, and it is highly affected by the quality of modelled data. The aim of this study is to validate the newly developed wind atlas for two onshore sites in Sweden. Wind resource assessment is conducted using NEWA mesoscale data as wind condition of the sites. AEP estimation is performed using two different simulation tools, and the results of estimation are compared to the actual SCADA data for the validation of NEWA. During the process of simulation, downscaling is executed for the mesoscale data to reflect micro terrain effects. The result of the current study showed that NEWA mesoscale data represents wind climate very well for the onshore site with simple terrain. On the other hand, NEWA provided overestimated wind speeds for the relatively complex onshore site with forested areas. The overestimation of wind speed led to predict AEP significantly higher than the measurements. The result of downscaling showed only little difference to the original data, which can be explained by the sites’ low orographic complexity. This study contributes to a deeper understanding of NEWA and provides insights into its validity for onshore sites. It is beyond the scope of this study to investigate whole region covered by NEWA. A further study focusing on sites with higher orographic complexity or with cold climate is recommended to achieve further understanding of NEWA.

Many parameters used for Wind Resource Assessment (WRA) have uncertainty and variability, yet are input into the process as single values. The extent of the uncertainty or variance may not be known, and may or may not be significant enough to affect output. This Thesis focused on the energy calculation element of WRA, to assess the affect that errors (uncertainty) in three key user inputs had on the energy results. A parameter was chosen from each of the main groups influencing the energy calculation: wind speed (atmosphere), surface roughness (site conditions), and power curve (turbine technology). Reasonable variation due to uncertainty for wind speed and power curve were taken from other studies and their application simplified. Roughness change was assessed over the 5 classes (Class 0 (water) to 4 (dense forest/city)). WindPRO software was used to calculate the Annual Energy Production (AEP) and applied to three different wind turbine generators at the same coordinate. A sensitivity analysis was done on the AEP results using a hybrid One-At-a-Time Local Sensitivity Analysis by determining percentage changes from baselines and an overall rate of change for those key input parameters. The results showed that roughness class change effect was not linear. Changing from Class 0 to 1, AEP was on average -8±1%. Class 1 to 2 change was on average ‑12±1%. Class 2 to 3 change was on average -20±2%. Class 3 to 4 change was on average -29±2%. The wind speed change effect was found to be roughly linear. If mean wind speed has an error of ±10%, the AEP could be expected to be out by approximately +18/‑17% with a standard deviation of +4/-3%. The power curve change effect was also roughly linear. A PC±9% error leads to an approximate +6/-7% AEP error with a standard deviation of ±1%. Roughness class change was the most sensitive parameter to AEP with a 14.5 average rate of change, followed by wind speed at 1.8, then power curve with a 0.8 rate. Results compared reasonably well with other relevant studies.

Wind farms are costly projects and prior to the construction, comprehensive wind resource assessment processes are carried out in order to predict the future energy yield with a reliable accuracy. These estimations are made to constitute a basis for the financial assessment of the project. However, predicting the future always accommodates some uncertainties and sometimes these assessments might overestimate the production. Many different factors might account for a discrepancy between the pre-construction wind resource assessment and the operational production data. This thesis investigates an underperforming wind farm in order to ascertain the reasons of a discrepancy case. To investigate the case, the relevant data and information along with the actual production data of three years are shared with the author. Prior to the construction, a wind resource assessment was carried out by an independent wind consultancy company and the work overestimated the annual energy production (AEP) by 19.1% based on the average production value of available three years. An extensive literature review is performed to identify the possible contributing causes of the discrepancy. The data provided is investigated and a new wind resource assessment is carried out. The underestimation of the wind farm losses are studied extensively as a potential reason of the underperformance. For the AEP estimations, WAsP in WindPro interface and WindSim are employed. The use of WindSim led to about 2-2.5% less AEP estimations compared to the results of WAsP. In order to evaluate the influence of long term correlations on the AEP estimations, the climatology datasets are created using the two different reanalysis datasets (MERRA and CFSR-E) as long term references. WindSim results based on the climatology data obtained using the MERRA and CFSR-E datasets as long term references overestimated the results by 10.9% and 8.2% respectively.

Wind power is seen as one of the most effective means available to combat the twin crises of global climate change and energy security. The annual market growth has established wind power as the leading renewable energy technology. Due to the availability of sparsely populated and flat open terrain, the Yucatán Peninsula located in eastern México is a promising region from the perspective of wind energy development but no comprehensive assessment of wind resource has been previously published. A basic requirement when developing wind power projects is to study the main characteristic parameters of wind in relation to its geographical and temporal distribution. The analysis of diurnal and seasonal wind patterns are an important stage in the move towards commercial exploitation of wind power. The research developed during the PhD has comprehensively assessed the wind behaviour over the Yucatán Peninsula region covering long term patterns at three sites, a spatial study using short term data for nine sites, a vertical profile study on one inland site and an offshore study made on a pier at 6.65km from the North shore. Monthly trends, directional behaviours and frequency distributions were identified and discussed. The characteristics of the wind speed variation reflected their proximity to the coast and whether they were influenced by wind coming predominantly from over the land or predominantly from over the sea. The atmospheric stability over the eastern seas was also analysed to assess thermal effects for different wind directions. Diurnal wind speed variations are shown to be affected in particular by the differing wind conditions associated with fetches over two distinct offshore regions. Seasonal behaviour suggests some departure from the oscillations expected from temperature variation. The offshore wind is thermally driven suggesting largely unstable conditions and the potential development of a shallow Stable Internal Boundary Layer.

<p>Frivilliga avsättningar av skog med höga naturvärden är en viktig del för att nå Miljömålet ”Levande skogar”. Det finns dock tveksamheter om de naturvårdsbiologiska kvalitéerna i dessa avsättningar. Syftet med denna studie var därför att undersöka om den skog som avsätts frivilligt av privata skogsägare är den skogsmark som har de högsta naturvärdena på fastigheten. Vidare studerades också markägarens naturvårdskunnande, utbildningsnivå och attityd till naturvård. Detta kan påverka viljan att avsätta skog frivilligt, hur långsiktig avsättningen blir samt kvalitén på avsättningarna. Studien består av inventeringar på sex skogsfastigheter i Östergötland med frivilliga avsättningar, samt en enkätstudie till skogsägare. Det visade sig att skogsägarna i huvudsak avsatte de bestånd med högst naturvärde på fastigheten. Tre bestånd (en lövskog, en tallskog samt en källmiljö) av totalt 59 hyste högre naturvärde än de frivilligt avsatta. De avsatta skogarnas hade lägre virkestäthet än produktionsbestånden och bestod i större utsträckning av lövskog. Majoriteten av skogsägarna avsatte skogen långsiktigt för kommande generationer. När skogsägarna fick rangordna syftet med sin skogsfastighet prioriterades virke i första hand, naturvård värderades betydligt lägre. En mätning av kunskaper i tillämpad ekologi och artkännedom visade att skogsägarnas kunskaper i regel var bristfälliga när det gällde igenkänning av indikatorarter samt viktiga trädslag för artbevarande. Majoriteten av de som var negativa till att göra frivilliga avsättningar kunde tänka sig att ändra åsikt vid ”skälig ersättning”. Mer omfattande studier behövs för att avgöra om mina resultat var representativa och om de frivilliga avsättningarna verkligen hyser fastighetens högsta naturvärden och lever upp till miljömålet levande skogar.</p> / <p>Voluntarily protected forests with high nature conservation value are an important part of fulfilling the environmental objective "Sustainableforests". The aim of this study was to evaluate if the voluntarily protected forests are those with the highest conservation value for threatened species¹ on the estate. Another purpose was to investigate the knowledge in applied ecology among small-scale foresters, their educational level and attitudes towards conservation. The study contains inventories at six different estates in the county of Östergötland and a query targeted to small-scale forest owners. The foresters in my study set aside the areas with the highest conservation values on the estate with few exceptions. Three areas (one deciduous forest, one pine forest and a well) out of 59 had a higher conservation value than the areas set aside voluntarily. The voluntarily protected forests had less timber density than the productive areas and contained more deciduous forest. A majority of the foresters voluntarily protected forests where intended to remain for future generations. As part of my study the foresters also got to rank the purpose of the forest estate. Timber got the highest rank while nature conservation got a considerable lower rank. A measurement of the small-scale forester's knowledge in applied ecology and indicator species showed that their knowledge often was inadequate regarding indicator species. A majority of those negative to voluntary forest conservation areas on their own estate were willing to change view if they were given adequate economic compensation.</p><p>1 according to the Swedish Red list</p>

Frivilliga avsättningar av skog med höga naturvärden är en viktig del för att nå Miljömålet ”Levande skogar”. Det finns dock tveksamheter om de naturvårdsbiologiska kvalitéerna i dessa avsättningar. Syftet med denna studie var därför att undersöka om den skog som avsätts frivilligt av privata skogsägare är den skogsmark som har de högsta naturvärdena på fastigheten. Vidare studerades också markägarens naturvårdskunnande, utbildningsnivå och attityd till naturvård. Detta kan påverka viljan att avsätta skog frivilligt, hur långsiktig avsättningen blir samt kvalitén på avsättningarna. Studien består av inventeringar på sex skogsfastigheter i Östergötland med frivilliga avsättningar, samt en enkätstudie till skogsägare. Det visade sig att skogsägarna i huvudsak avsatte de bestånd med högst naturvärde på fastigheten. Tre bestånd (en lövskog, en tallskog samt en källmiljö) av totalt 59 hyste högre naturvärde än de frivilligt avsatta. De avsatta skogarnas hade lägre virkestäthet än produktionsbestånden och bestod i större utsträckning av lövskog. Majoriteten av skogsägarna avsatte skogen långsiktigt för kommande generationer. När skogsägarna fick rangordna syftet med sin skogsfastighet prioriterades virke i första hand, naturvård värderades betydligt lägre. En mätning av kunskaper i tillämpad ekologi och artkännedom visade att skogsägarnas kunskaper i regel var bristfälliga när det gällde igenkänning av indikatorarter samt viktiga trädslag för artbevarande. Majoriteten av de som var negativa till att göra frivilliga avsättningar kunde tänka sig att ändra åsikt vid ”skälig ersättning”. Mer omfattande studier behövs för att avgöra om mina resultat var representativa och om de frivilliga avsättningarna verkligen hyser fastighetens högsta naturvärden och lever upp till miljömålet levande skogar. / Voluntarily protected forests with high nature conservation value are an important part of fulfilling the environmental objective "Sustainableforests". The aim of this study was to evaluate if the voluntarily protected forests are those with the highest conservation value for threatened species1 on the estate. Another purpose was to investigate the knowledge in applied ecology among small-scale foresters, their educational level and attitudes towards conservation. The study contains inventories at six different estates in the county of Östergötland and a query targeted to small-scale forest owners. The foresters in my study set aside the areas with the highest conservation values on the estate with few exceptions. Three areas (one deciduous forest, one pine forest and a well) out of 59 had a higher conservation value than the areas set aside voluntarily. The voluntarily protected forests had less timber density than the productive areas and contained more deciduous forest. A majority of the foresters voluntarily protected forests where intended to remain for future generations. As part of my study the foresters also got to rank the purpose of the forest estate. Timber got the highest rank while nature conservation got a considerable lower rank. A measurement of the small-scale forester's knowledge in applied ecology and indicator species showed that their knowledge often was inadequate regarding indicator species. A majority of those negative to voluntary forest conservation areas on their own estate were willing to change view if they were given adequate economic compensation. 1 according to the Swedish Red list

Wind resource assessment studies have been conducted in the Israeli side and the Palestinian side before; however, the previous studies were restricted with the political border either Palestinian or Israeli except one of them that was based on measurements dated to 1940-1983 (R. Shabbaneh &amp; A. Hasan, 1997). Moreover, the studies were performed years ago, with simple techniques and based on old data (R. Shabbaneh &amp; A. Hasan, 1997). Hence, the needs for a new study that is based on updated data, and using updated model is highly demanded. This study is intended to perform wind resource assessment in Palestine/Israel; the study has used two stages of assessment, primary one based on reference station data on both sides, Israeli and Palestinian. The second stage of wind resource assessment is based on WindPRO software. The wind resource assessment ends up with identifying sites with higher potential that are situated in four selected sites, North of Palestine/Israel, North of West-bank, Jerusalem, and Eilat, the higher potential was in Eilat area bearing mean wind speed of 9.88m/s at 100 m hub height.Moreover, the study recognized the importance of political situation assessment due to the Israeli-Palestinian conflict. Based on conducted survey, the political situation assessment concluded that international non-governmental organizations seem to be most capable of starting up wind power project in Palestine/Israel. Furthermore, the study concluded that supportive policies from both the Israeli and Palestinian governments are crucial to promote wind power projects in the region.