Optimization of reliable cyclic cable layouts in offshore wind farms

A novel approach for optimizing reliable cable layouts in offshore wind farms is presented. While optimization models traditionally are designed to suggest acyclic cable routes, those developed in this work recognize that cyclic layouts reduce the consequences of cable failures. The models under study take into account that cables cannot cross each other, which, particularly in instances with restrictive cable capacity, can make it attractive to let cables follow a joint trajectory, and visit turbines without connecting to them. A two-layered optimization process is developed. The outer layer is associated with an integer programming problem, which is subject to simultaneous generation of rows and columns representing cable paths. In the inner layer, a problem identifying feasible low cost paths is solved, guided by optimal dual variable values in the continuous relaxation of the former problem. Results from experimental applications to existing wind farms show good promise of the method.publishedVersio

On the optimization of offshore wind farm layouts

Layout optimization of offshore wind farms seeks to automate the design of the wind farm and the placement of wind turbines such that the proposed wind farm maximizes its potential. The optimization of an offshore wind farm layout therefore seeks to minimize the costs of the wind farm while maximizing the energy extraction while considering the effects of wakes on the resource; the electrical infrastructure required to collect the energy generated; the cost variation across the site; and all technical and consenting constraints that the wind farm developer must adhere to. As wakes, electrical losses, and costs are non-linear, this produces a complex optimization problem. This thesis describes the design, development, validation, and initial application of a new framework for the optimization of offshore wind farm layouts using either a genetic algorithm or a particle swarm optimizer. The developed methodology and analysis tool have been developed such that individual components can either be used to analyze a particular wind farm layout or used in conjunction with the optimization algorithms to design and optimize wind farm layouts. To accomplish this, separate modules have been developed and validated for the design and optimization of the necessary electrical infrastructure, the assessment of the energy production considering energy losses, and the estimation of the project costs. By including site-dependent parameters and project specific constraints, the framework is capable of exploring the influence the wind farm layout has on the levelized cost of energy of the project. Deploying the integrated framework using two common engineering metaheuristic algorithms to hypothetical, existing, and future wind farms highlights the advantages of this holistic layout optimization framework over the industry standard approaches commonly deployed in offshore wind farm design leading to a reduction in LCOE. Application of the tool to a UK Round 3 site recently under development has also highlighted how the use of this tool can aid in the development of future regulations by considering various constraints on the placement of wind turbines within the site and exploring how these impact the levelized cost of energy

The Yoga Analogy: Scaling-Up the U.S.’s Renewable Energy Sector Mindfully with New Technologies, Evolving Standards, Public Buy-In, Data Sharing, and Innovation Clusters

This paper focuses on innovative renewable energy devices, exploring how scientifically-based industry standards that continuously evolve with engineering design technology, the public’s buy-in and feeling of connectedness with groundbreaking devices, and innovation clusters that accelerate device development through data sharing and public-private partnerships can all help advance the U.S.’s domestic renewable energy industry. Part I analyzes challenges inherent to scaling- up novel renewable energy technologies while simultaneously developing the industry standards regulating them. Part II uses the Block Island Wind Farm, an offshore wind demonstration project, and Pavegen’s globally-deployed arrays of piezoelectric smart flooring tiles as examples illustrating the importance connectedness and engagement play in garnering public buy-in during a cutting-edge renewable energy device’s roll-out. Part III discusses private investors’ critical role in bearing financial risks associated with backing experimental technologies, promoting aesthetically unusual device designs, and integrating novel devices into the built environment. Part IV explores the advantages that data anonymization and data sharing within a data trust construct can produce for constituents in an innovation cluster, particularly those functioning together within a public-private partnership. Part V explores the benefits of introducing a renewable energy device prototype in an innovation cluster, where the government, academia, and industry collaborate and share data through public-private partnerships in an engaged, supportive, and technologically savvy community focused on accelerating the development of a particular industry. This paper concludes that by setting industry standards that continuously evolve in tandem with technologies they aim to regulate, having businesses’ investment-backed expectations remain a key driving force in renewable energy device development, and deploying government funding through innovation clusters that support data sharing and public-private partnerships in a particular industry, the U.S. can strike a desired balance and mindfully scale-up its nascent renewable energy industry

Balancing Spatial and Environmental Impacts of large scale Renewable Offshore Energy Generation in the North Sea

The growing EU energy ambitions in the North Sea region are urging for an accelerated deployment of large-scale renewable energy (RE) infrastructure, with offshore wind farms (OWF) playing an essential role. However, implementing the current EU targets can be limited by the multiple competing spatial claims between existing sea uses, ecological values and OWFs, causing key uncertainties related to potential risks of interaction that may result in barriers to a swift roll-out of RE infrastructure. Up to this date there is no clear understanding of the space availability for different renewable energy installations. Such space availability depends on the alternative space management options applied, relying e.g. on more sectoral management to separate activities or instead, more integrated management to pursue multiuse in time or space. Understanding these trade-offs is especially urgent in the current context of planning marine resources on the North Sea, characterized by lack of coordination, sectoral and fragmented planning, which exacerbates the uncertainties on the potential socio-economic and ecological risks of interaction. In response to these challenges, this thesis aimed to:Develop and demonstrate a set of integrated analytical tools for quantifying and qualifying the spatially explicit trade-offs between offshore spatial claims, in the context of the energy system transition in the North Sea basin.The analytical frameworks developed and used in this study relied and benefited from multiple interactions with multiple research disciplines and methodologies developed as part of the larger network of the ENSYSTRA project

Ocean current energy resource assessment for the United States

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.Ph.D