Power electronic converters have become popular in the field of power transformation for renewable energy. Power electronics converters achieve high efficiency, and the price of their components is falling, thus making them even more beneficial for renewable energy applications. Those systems coupled to the grid need to withstand certain utility-defined circumstances which may occur during operation. Additionally the new net regulations for large generation plants specify that during specified severe grid disturbances the relatively delicate converters should stay connected supporting the system. For PV inverters the forthcoming standards may optionally add the possibility of reactive power compensation where for wind-power those standards are already in use. This thesis focuses on reliable, sensor-less control of the PWM converters coping with varying grid conditions and existing problems. The thesis presents a variety of digital control solutions for interfacing PWM converter with the grid, synchronization, sensorless operation and grid impedance detection. The introductory chapter gives the fundamental theory about three-phase converters and control.The following chapters deal with unbalanced condition and symmetric component decomposition, which is the tool to cope with unbalanced grid voltages or currents. A sensor-less operation method using dual frame virtual flux model is presented with good results. In addition sensor-less synchronization to the grid is shown. Moreover an algorithm based on virtual flux for grid inductance estimation is also successfully demonstrated. Knowing the grid inductance is important during weak grid operation, since it is needed in order to provide unity power factor to the point of common connection. At the end of the thesis, a control algorithm for voltage harmonic compensation during stand alone operation is presented. The presented algorithm gives the possibility to supply high quality power in isolated islands, where the load is unknown. Furthermore, this algorithm can be successfully used for UPS applications. The last chapter applies the voltage harmonic control to the Z-source converter having the possibility of achieving higher ac voltage than in conventional VSI, results are promising.

Climate change will result in variable – but undeniably severe – changes to our natural world. These changes will lead to extreme human and ecosystem consequences if climate change is not mitigated effectively, efficiently, and rapidly. Increasing the use of renewable energies around the world is seen as one of the most effective and promising mitigation strategies. Several communities around the United States have recently denounced publicly their electrical utilities for their failure to offer the choice to increase the percentage of energy that comes from renewable sources. A growing number are taking action to work with – or sometimes against – their energy providers to increase the percentage of renewable energies available. Boulder, Colorado is one of these communities. Since 2005, Boulder has been exploring the possibility of municipalizing its investor-owned electric utility, thereby bringing the utility under city control. In doing so, it would control the sources of electricity that would be used by its residents, and potentially provide these customers with 100 percent renewable energy. Boulder is in the final phases of studying the possibility of full municipalization and aims to begin this process in the near future. While it remains to be seen if the city will successfully create a municipally owned utility (MOU), an examination of Boulder’s thought processes, studies, and decision making to date provides an opportunity for a discussion of the benefits and possible downsides of municipalization and allows a glimpse into the future of MOUs in the United States.

Tidal currents and rivers are promising sources of renewable energy given that suitable turbines for kinetic energy conversion are developed. To be economically and technically feasible, a velocity distribution that can give a high degree of utilization (or capacity factor), while the ratio of maximum to rated velocity is low would be preferable. The rated velocity is defined as the velocity at which rated power is achieved. Despite many attempts to estimate the resource, however, reports on the possible degree of utilisation from tidal currents and rivers are scarce. In this paper the velocity distribution from a number of regulated rivers, unregulated rivers and tidal currents have been analysed regarding the degree of utilisation, the fraction of converted energy and the ratio of maximum to rated velocity. Two methods have been used for choosing the rated velocity; one aiming at a high fraction of converted energy and one aiming at a high degree of utilisation. Using the first method, with a rated velocity close to the maximum velocity, it is unlikely that the turbine will reach the cut-out velocity. This results in, on average, a degree of utilisation of 23% for regulated rivers, 19% for unregulated rivers and 17% for tidal currents while converting roughly 30-40% of the kinetic energy. Choosing a rated velocity closer to the mean velocity resulted in, on average, a degree of utilisation of 57% for regulated rivers, 52% for unregulated rivers and 45% for tidal currents. The ratio of maximum to rated velocity would still be no higher than 2.0 for regulated rivers, 1.2 for unregulated rivers and 1.6 for tidal currents. This implies that the velocity distribution of both rivers and tidal currents is promising for kinetic energy conversion. These results, however, do not include weather related effects or extreme velocities such as the 50-year velocity. A velocity factor is introduced to describe what degree of utilisation can be expected at a site. The velocity factor is defined as the ratio U-max/U-rate at the desired degree of utilisation, and serves as an early indicator of the suitability of a site.

Among sources of renewable energy, development of tidal energy has traditionally been plagued by relatively high costs and limited availability of sites with sufficiently high tidal amplitudes or flow velocities. However, many recent technology developments and improvements, both in design (e.g. dynamic tidal power, tidal lagoons) and turbine technology (e.g. new axial turbines, crossflow turbines), showed that the economic and environmental costs may be brought down to competitive levels comparing to other conventional energy sources. It has long been identified that the Bay of Fundy is one of the world’s premier locations for the development of tidal power generating systems, since it has some of the world’s largest tidal ranges. Consequently, several proposals have been made in the recent years to find economical ways to harness the power of tides. Presently, there is considerable interest in installing tidal lagoons in the Bay of Fundy. The lagoon concept involves temporarily storing seawater behind an impoundment dike and generating power by gradually releasing the impounded seawater through conventional low-head hydroelectric turbines. A tidal lagoon will inherently modify the tides and tidal currents regime in the vicinity of the lagoon, and possibly induce effects that may be felt throughout the entire Bay of Fundy. The nature of these hydrodynamic impacts will likely depend on the size of the tidal lagoon, its location, and its method of operation. Any changes in the tidal hydrodynamics caused by a tidal lagoon may also impact on the transport of sediments throughout the region and upset ecosystems that are well adapted to existing conditions. The scale and character of the potential hydrodynamic impacts due to tidal lagoons operating in the Bay of Fundy have not been previously investigated. The present study endeavours to investigate these potential impacts to help the development of sustainable, science-based policies for the management and development of clean energy for future generations. After outlining fundamental aspects of tidal power projects taken in consideration in the Bay of Fundy, an analysis of present knowledge on tidal lagoons was conducted in order to provide a focus for subsequent investigations. Hydrodynamic modeling was used to quantify any of the potential hydrodynamic changes induced in the Bay of Fundy due to the presence of tidal lagoons. In the last part of the thesis, new relationships were derived in order to describe the amount of energy removed from tidal lagoons associated with its hydrodynamic impacts.

In 2003, the town of Craik initiated a unique renewable energy project with the dual goals of addressing both the environmental and the rural economic crisis. This Masters thesis provides an exploration of the factors that both facilitate and constrain the advancement of this project. The research focuses on the question: What are the cultural and social factors that inhibit the Craik project from meeting its environmental and economic goals? New social movement theory provides a theoretical framework for explaining contradictions within social movements, while a critical ethnographic methodology is used to uncover specific underlying contradictions that exist at Craik. This thesis analyzes the dynamics of facilitating and non-facilitating factors to make visible the deeper sources of conflict, to contribute to theoretical models of social change and understandings of community development. Furthermore, the thesis provides direction for the Craik eco-project that can further the implementation of practices that will facilitate both its economic and environmental goals. Finally, the study provides valuable insights to other communities working to facilitate similar eco-projects and influence public policy in response to global warming

Various levels of governments in Canada have introduced different types of tax instruments in order to encourage the development of renewable energy. This paper will look at the challenges that render those tax instruments inefficient and/or ineffective. For the ease of discussion, I will divide the said challenges by a hypothetical timeline of “before” and “during” the implementation of renewable energy. “Before” the implementation, some of the current tax incentives are criticized to be ineffective because there are better policy substitutes. It is also found that the inherent characteristics of renewable energy sources themselves render policy instruments inefficient. “During” the implementation, the currently existing “unlevel playing field” with the conventional oil and gas industry is found to be the strongest factor that causes tax incentives on renewable energy ineffective; the introduction of a carbon tax is recommended here. Lastly, even the most comprehensive tax measures are found unable to completely address the “exogenous” factors.

The limitations of renewable energy technologies require that pathways are carefully chosen such that renewable resources are used most effectively in addressing modern energy challenges. Optimized decision-making is particularly challenging for the forest bioenergy sector because of the multitude of potential pathways and because profit is highly sensitive to biomass procurement costs. I assessed energy wood recovery and procurement costs during semi-mechanized selection operations in the tolerant hardwood forests of Ontario. Logging contractors were able to recover unmerchantable sections of branches normally discarded during conventional operations, amounting to 1.3 to 2.7 dry tonnes of additional biomass per hectare. Supply chain scenarios are used to show that the biomass can be brought to market at a cost similar to mechanized operations. The need for prioritization of decentralization, efficiency, and integration with the value-added forest sector is discussed with reference to the relative scarcity and high cost of the forest resource.

Various levels of governments in Canada have introduced different types of tax instruments in order to encourage the development of renewable energy. This paper will look at the challenges that render those tax instruments inefficient and/or ineffective. For the ease of discussion, I will divide the said challenges by a hypothetical timeline of “before” and “during” the implementation of renewable energy. “Before” the implementation, some of the current tax incentives are criticized to be ineffective because there are better policy substitutes. It is also found that the inherent characteristics of renewable energy sources themselves render policy instruments inefficient. “During” the implementation, the currently existing “unlevel playing field” with the conventional oil and gas industry is found to be the strongest factor that causes tax incentives on renewable energy ineffective; the introduction of a carbon tax is recommended here. Lastly, even the most comprehensive tax measures are found unable to completely address the “exogenous” factors.

The limitations of renewable energy technologies require that pathways are carefully chosen such that renewable resources are used most effectively in addressing modern energy challenges. Optimized decision-making is particularly challenging for the forest bioenergy sector because of the multitude of potential pathways and because profit is highly sensitive to biomass procurement costs. I assessed energy wood recovery and procurement costs during semi-mechanized selection operations in the tolerant hardwood forests of Ontario. Logging contractors were able to recover unmerchantable sections of branches normally discarded during conventional operations, amounting to 1.3 to 2.7 dry tonnes of additional biomass per hectare. Supply chain scenarios are used to show that the biomass can be brought to market at a cost similar to mechanized operations. The need for prioritization of decentralization, efficiency, and integration with the value-added forest sector is discussed with reference to the relative scarcity and high cost of the forest resource.

The energy transition has started. The key is to find an alternative to uneconomical and unsustainable energy production. In this sense it is a challenge to develop renewable energy technologies suitable for the present and proper for the future. Uppsala University is driving the Lysekil project at its Division of Electricity. The aim is to design an environmentally friendly energy system with wave energy converters (WECs) that are simple and strong in design. However, little has been done to know more about its economically feasibility and the social impact of its benefits. Therefore, this research focuses on a positional analysis of a 3 MW Wave Power Park to understand the relevant aspects of implementing this kind of technology. The target area will be at Rosarito, Baja California at the Pacific Ocean in the Northeast of Mexico, a region experiencing increasing energy demand. This thesis combines technical, economical and social aspects. The technical part describes how the device works. The analysis is complemented by describing the current energy situation in Mexico and the social benefits of sustainable energy. Finally, the economical analysis is presented, it is focused on the perspective of the Merchant Power Plant. The review shows that wave power could be economically viable due to its high degree of utilisation. Energy diversification and security, economic and sustainable development, and clean energy are some of the advantages of wave power. Therefore, wave power is an interesting alternative for generating electricity in Mexico. However, the energy sector is highly subsidised, making it difficult for new technologies to enter the market without government participation. Another finding is that in the long run if the equipment cost decreases or subsidies are applied, the technology might be successfully implemented. Environmental consequences are described briefly, concluding that little is known and more research is needed. The environmental constraints, economic implications and uncertainties of a high energy future are disturbing. In that sense, renewable energy appears to be unequivocally better than rely to a greater extent on fossil fuels, in the sense that they offer a sustainable development and less environmental damage.