Public-private partnerships (PPPs) for the delivery of transportation infrastructure are said to offer increased efficiency resulting from the private sector’s life-cycle approach to design and construction. While the literature on PPPs endorses such efficiencies, studies don’t provide empirical support for that claim. The goal of this thesis was to assess that notion. Four tasks were carried out to explore that issue. First, a literature review searched for evidence of such efficiencies and methodologies to evaluate them. Second, a simple methodology to evaluate the life-cycle cost-efficiencies of the public and private sectors was proposed. Third, since most PPP projects in the U.S. are recent and currently subject to routine operations and maintenance (O&M), indicators to compare those costs were proposed as well. Fourth, a case study compared the routine O&M costs of a PPP and of those of a system of publicly developed and managed tollroads. The literature review found no empirical evidence of superior O&M cost-efficiency of PPPs, and also, that most studies focused on design and construction cost and schedule overruns. While some studies assessing performance and/or efficiency were at times theoretical and not likely employed in practice, one methodology is proposed to evaluate life-cycle cost-efficiency. The case study results showed that the concessionaire was more cost-efficient in terms of operating expenditures (OPEX) per mile (-60%) and per lane-mile (-53%) than the system. The public system was more cost-efficient in OPEX per vehicle-miles travelled (97%), number of toll transactions (332%), and toll revenue (20%). However, those three indicators depend on traffic volume which during the study period was overwhelmingly greater on the public system. While the case study showed cost-efficiency differences between the public and private sectors, additional research is needed to empirically test the hypothesis of greater efficiency of the private sector. The proposed framework can be used, but adequate data and further assumptions about O&M costs are needed; for that, it is recommended that more comprehensive case studies be performed to obtain detailed empirical data. A better understanding of the differences in cost-efficiency between publicly and privately managed roads will help decision-makers minimize the life-cycle cost of their investments. / text

This research was designed to investigate the fundamental nature in which blind people utilize audible cues to attend to their surroundings. Knowledge on how blind people respond to external spatial stimuli is expected to assist in development of better tools for helping people with visual disabilities navigate their environment. There was also interest in determining how blind people compare to sighted people in auditory localization tasks. The ability of sighted individuals, blindfolded individuals, and blind individuals in localizing spatial auditory targets was assessed. An acoustic display board allowed the researcher to provide multiple sound presentations to the subjects. The subjects’ responses in localization tasks were measured using a combination of kinematic head tracking and eye tracking hardware. Data was collected and analyzed to determine the ability of the groups in localizing spatial auditory targets. Significant differences were found among the three groups in spatial localization error and temporal patterns.

Operations and maintenance (O&M) activities represent a significant share of the expenses during the lifetime of offshore wind farms. When compared to onshore wind farms, O&M costs are increased for the offshore case, as specialized vessels, weather windows and rough conditions mean more failures, downtime (decreasing availability), spare parts, and man-hours.This study comprises an analysis of the available O&M data from a selected offshore wind farm. The results and conclusions from this investigation could then be used to evaluate possible reliability improvements and compare options for the maintenance strategies, as well as to ponder the convenience of warranty periods and O&M agreements between wind farm operators and wind turbine manufacturers or O&M service providers.The life-cycle cost (LCC) concept is utilized in the analysis of the wind farm survey for this thesis. LCC analysis could be the starting point to make decisions regarding specific wind turbine models, as selecting the turbines with the lowest initial cost may not be necessarily the scenario which also costs the least amount of money when taking into consideration the whole life cycle. It may also be a great tool to forecast future operational incomes and expenses of offshore wind farms.

The wind industry is growing rapidly and especially in Europe, offshore wind power has become a serious business with approximately 22 GW installed in 2019. However, for the industry to become even more competitive, costs must be reduced. Especially the Operation and Maintenance (O&M) costs present a challenge to developers and operators. In order to achieve cost savings during the operational phase, the factors influencing the maintenance operations should be identified. This Thesis focuses on the factors influencing the offshore wind turbine foundation maintenance operations. The aim of the Thesis is to identify these factors and their attributes, as well as rank them according to their importance. First, a literature review was conducted to establish the theoretical background for this study. In order to do so, maintenance strategies, offshore wind turbine foundations and the scope of foundation maintenance were described in detail. After that, the factors influencing the maintenance for offshore wind turbine foundations were collected from literature, personal experience, and input from industry experts. Following that, a two-step study with seven industry experts was conducted to validate these factors and their attributes as a first step before then ranking all the attributes by their importance. The experts were asked to rank each attribute by assigning a number from 1-5 where: very high influence (5), high influence (4), medium influence (3), low influence (2) and no influence (1). Since the maintenance differs for the subsea and the above water part of the foundation, the participants had to rank each attribute twice, once for the subsea part and once for the part above water. After the results were analyzed, it can be concluded that the Quality Health Safety Environment (QHSE) was ranked as the most important, followed by technology and standards & guidelines. The environment factor was ranked as the least important before the geographical location and cost factors.

Renewable energy sources are in strong demand as the need for clean energy is increasing, driven by the need to reach the environmental targets. Offshore wind power is becoming an attractive source as the technology matures and cost decreases. With time all wind farms age and when the time comes one needs to consider end of life alternatives. The objective with this Thesis is to assess lifetime extension of offshore wind farms, with a focus on reliability, availability and maintenance. As of today there are few offshore wind farms reaching their end of life but one needs to be prepared. From the literature review it is clear that there is somewhat limited documentation around lifetime extensions. The reason for lifetime extension is to increase the return on investment (ROI) of the original project, with a limited additional investment. With capital expenditure (CAPEX) being a large part of the overall project cost it is beneficial to achieve more operational years to divide the cost over, one also need to consider increased operations and maintenance (O&M) cost with aging assets. In this Thesis, a Reliability block diagram (RBD) model was developed in ReliaSoft BlockSim to calculate wind turbine failures, their associated downtime and O&M costs to create an overview of the future behaviour and cost. To assess the wind farm economics a financial model was built, based on output from the RBD model, to evaluate the levelized cost of energy (LCOE) and internal rate of return (IRR) for several cases of lifetime extension. A case study was done for a generic wind farm of 30 wind turbines, assumed to be built around 2010 using 3.6MW rated turbines, to illustrate a relevant case. Focus was on O&M cost, and it was assumed the structural integrity of the wind turbines would be maintained for the lifetime extension for up to 10 years.

<p>The wind power industry is maturing and the amount of electricity produced by wind turbines in the world is rapidly increasing every year. Service and maintenance of wind turbines has proven to be difficult and expensive, especially offshore. A well coordinated support organisation and optimized maintenance strategies are required to effectively reduce the costs associated with WT support, where cost-efficient supply and storage of spare parts are important. The aim of this thesis is to model spare part logistics for wind turbines to analyse different strategies and compare the profitability. Optimal stock levels and reorder sizes have been calculated with the software tool OPUS10. Wind turbine and spare part data have been provided by Vattenfall Vindkraft AB and field studies were made to the wind farms Lillgrund and Horns Rev to gather information.</p><p>Our analyses show that different spare part strategies only affect a minor part of the total support costs generated for a wind farm. Still there are many improvements possible and money to be saved if using an optimal spare part strategy instead of one based on personal experiences and intuition. For a large wind power system, including a number of wind farms with the same wind turbine types, we also show convincing results that pooling of spare parts are a much more cost-efficient spare part strategy compared to local storage and handling only. Using a central depot for spare part reordering and storage of critical spare parts, such as gearboxes, generators and blades, are more profitable</p>

The wind power industry is maturing and the amount of electricity produced by wind turbines in the world is rapidly increasing every year. Service and maintenance of wind turbines has proven to be difficult and expensive, especially offshore. A well coordinated support organisation and optimized maintenance strategies are required to effectively reduce the costs associated with WT support, where cost-efficient supply and storage of spare parts are important. The aim of this thesis is to model spare part logistics for wind turbines to analyse different strategies and compare the profitability. Optimal stock levels and reorder sizes have been calculated with the software tool OPUS10. Wind turbine and spare part data have been provided by Vattenfall Vindkraft AB and field studies were made to the wind farms Lillgrund and Horns Rev to gather information. Our analyses show that different spare part strategies only affect a minor part of the total support costs generated for a wind farm. Still there are many improvements possible and money to be saved if using an optimal spare part strategy instead of one based on personal experiences and intuition. For a large wind power system, including a number of wind farms with the same wind turbine types, we also show convincing results that pooling of spare parts are a much more cost-efficient spare part strategy compared to local storage and handling only. Using a central depot for spare part reordering and storage of critical spare parts, such as gearboxes, generators and blades, are more profitable

Yes / Wind Energy published by John Wiley & Sons Ltd. Maintenance is essential in keeping wind energy assets operating efficiently. With the development of advanced condition monitoring, diagnostics and prognostics, condition-based maintenance has attracted much attention in the offshore wind industry in recent years. This paper models various maintenance activities and their impacts on the degradation and performance of offshore wind turbine components. An integrated maintenance strategy of corrective maintenance, imperfect time-based preventive maintenance and condition-based maintenance is proposed and compared with other traditional maintenance strategies. A maintenance simulation programme is developed to simulate the degradation and maintenance of offshore wind turbines and estimate their performance. A case study on a 10-MW offshore wind turbine (OWT) is presented to analyse the performance of different maintenance strategies. The simulation results reveal that the proposed strategy not only reduces the total maintenance cost but also improves the energy generation by reducing the total downtime and expected energy not supplied. Furthermore, the proposed maintenance strategy is optimised to find the best degradation threshold and balance the trade-off between the use of condition-based maintenance and other maintenance activities. / UK Engineering and Physical Sciences Research Council (EPSRC). Grant Number: EP/P009743/1

abstract: In the current photovoltaic (PV) industry, the O&M (operations and maintenance) personnel in the field primarily utilize three approaches to identify the underperforming or defective modules in a string: i) EL (electroluminescence) imaging of all the modules in the string; ii) IR (infrared) thermal imaging of all the modules in the string; and, iii) current-voltage (I-V) curve tracing of all the modules in the string. In the first and second approaches, the EL images are used to detect the modules with broken cells, and the IR images are used to detect the modules with hotspot cells, respectively. These two methods may identify the modules with defective cells only semi-qualitatively, but not accurately and quantitatively. The third method, I-V curve tracing, is a quantitative method to identify the underperforming modules in a string, but it is an extremely time consuming, labor-intensive, and highly ambient conditions dependent method. Since the I-V curves of individual modules in a string are obtained by disconnecting them individually at different irradiance levels, module operating temperatures, angle of incidences (AOI) and air-masses/spectra, all these measured curves are required to be translated to a single reporting condition (SRC) of a single irradiance, single temperature, single AOI and single spectrum. These translations are not only time consuming but are also prone to inaccuracy due to inherent issues in the translation models. Therefore, the current challenges in using the traditional I-V tracers are related to: i) obtaining I-V curves simultaneously of all the modules and substrings in a string at a single irradiance, operating temperature, irradiance spectrum and angle of incidence due to changing weather parameters and sun positions during the measurements, ii) safety of field personnel when disconnecting and reconnecting of cables in high voltage systems (especially field aged connectors), and iii) enormous time and hardship for the test personnel in harsh outdoor climatic conditions. In this thesis work, a non-contact I-V (NCIV) curve tracing tool has been integrated and implemented to address the above mentioned three challenges of the traditional I-V tracers. This work compares I-V curves obtained using a traditional I-V curve tracer with the I-V curves obtained using a NCIV curve tracer for the string, substring and individual modules of crystalline silicon (c-Si) and cadmium telluride (CdTe) technologies. The NCIV curve tracer equipment used in this study was integrated using three commercially available components: non-contact voltmeters (NCV) with voltage probes to measure the voltages of substrings/modules in a string, a hall sensor to measure the string current and a DAS (data acquisition system) for simultaneous collection of the voltage data obtained from the NCVs and the current data obtained from the hall sensor. This study demonstrates the concept and accuracy of the NCIV curve tracer by comparing the I-V curves obtained using a traditional capacitor-based tracer and the NCIV curve tracer in a three-module string of c-Si modules and of CdTe modules under natural sunlight with uniform light conditions on all the modules in the string and with partially shading one or more of the modules in the string to simulate and quantitatively detect the underperforming module(s) in a string. / Dissertation/Thesis / Masters Thesis Engineering 2020

This thesis validates SIMLOX as a simulation tool for wind energy operation and maintenance (O&amp;M). SIMLOX have been used for modeling O&amp;M in other sectors since 2002 but have recently begun to be used for simulating wind energy. This study validates SIMLOX for the newly introduced sector by creating a model of an existing offshore wind farm. The model used real historical data as input and the output was compared to real system response quantities (SRQs). Example of SRQs which were compared was time based availability, energy based availability, energy production, weather days, and item replacements. The study showed that SIMLOX is very well suited for this type of studies. It also showed that the major difficulty lies in obtaining proper input data. All models simulated the exact right number of major item replacements. The time based availability was considered to be the most important SRQ. The time based availability turned out to be between 0.11 - 0.66 percentage points too high compared to reference data. This most certainly depended on an overestimated work schedule for the technicians. Validation is the process of determining the degree to which a model is an accurate representation of the real world from the perspective of the intended uses of the model. This report presents all necessary knowledge to validate SIMLOX as a tool for wind energy simulations but it is thus up to the user to decide whether or not the output is accurate enough for their intended use.