• Energy Research
• 2016-2025close
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In order to accelerate the transition from carbon fuels to renewable energy sources, it is essential to extend our knowledge of the resources’ availability to further improve or adjust the design of extraction devices. In the present paper, a first characterization of the tidal stream resource along the coast of The Netherlands is performed using a high-resolution unstructured grid implementation of the Thetis model. Extensive validation of the sea surface elevations was done by comparing with existing networks of tide gauges in the North Sea. The simulations from this study show that the highest tidal current intensities are generated mainly at Den Helder and Oost Vlieland, reaching values >1.5 m s−1 and power density estimates that are most frequently close to 300 W m−2 and that can reach values ≥ 900 W m−2. Given the relatively reduced depths where these ‘‘hot spots’’ are found, most existing stream turbines will require further development to operate. Nevertheless, the existence of higher current intensities zones, along a commonly considered ‘‘low energy’’ coast, opens the door to include the tidal stream resource in near future plans to diversify the energy supply in The Netherlands. Offshore Engineering

Unsteady loads are a major limiting factor for further upscaling of HAWTs considering the high costs associated to strict structural requirements. Alleviation of these unsteady loads on HAWT blades, e.g. using active flow control (AFC), is of high importance. In order to devise effective AFC methods, the unsteady loading sources need to be identified and their relative contribution to the load fluctuations experienced by blades needs to be quantified. The current study investigates the effects of various atmospheric and operational parameters on the fluctuations of α and CL for a large HAWT. The investigated parameters include turbulence, wind shear, yawed inflow, tower shadow, gravity and rotational imbalances. The study uses the DTU's aeroelastic software HAWC2. The study identifies the individual and the aggregate effect of each source on the aforementioned fluctuations in order to distinguish the major contributing factors to unsteady loading. The quantification of contribution of each source on the total fatigue loads reveals >65% of flapwise fatigue loads is a result of turbulence while gravity results in >80% of edgewise fatigue loads. The extensive parametric study shows that the standard deviation of CL is 0.25. The results support to design active load control systems by highlighting the magnitude of CL and α variations experienced by HAWTs, and thus the dCL that needs to be delivered by an AFC system.

This study follows a multi-disciplinary approach to implementing an Energy Community (ECs) in Vega de Valcarce, a rural community in Spain. ECs are entities that encompass collective actions of citizens and other actors towards the open, democratic governance of renewable energy sources; ECs can take various technical and organisational forms. This study developed and evaluated socially accepted, technically optimal and feasible options for the implementation of the EC at Vega de Valcarce. We conducted a participatory multi-criteria analysis incorporating the results of mixed-integer linear programming for energy system optimisation and regulatory analysis of ECs under Spanish law. Our study showed that the main objectives of local stakeholders are the reduction of the energy bill and emissions. The limited liability company fulfilled legal and regulatory restrictions the best by implementing a bigger-sized EC. We summarise the key challenges of implementing an EC in a rural context, mainly legal and financial, and conclude with recommendations on how to overcome these. While contributing to understanding the roll-out of ECs in Spain and Europe, our research aims to provide a structured approach for the uptake of renewable energy in rural areas.

Floating Offshore Wind Turbines (FOWT) can harness the abundant offshore wind resource at reduced installation requirements. However, a further decrease in the development risks through higher confidence in the design and analysis methods is needed. The dynamic behaviour of FOWT systems is complex due to the strong interactions between the large translational and rotational motions and the diverse loads, which poses a challenge. While the methods to study the FOWT's general responses are well established, there are no methods to describe the highly complex time-dependent rotational motion patterns of FOWT. For a rigid body in general plane motion, an Instantaneous Centre of Rotation (ICR) can be identified as a point at which, at a given moment, the velocity is zero. However, it is common to assume a centre of rotation fixed in space and time, arbitrarily set at the centre of floatation or gravity. Identification of the ICR is crucial as it may lead to better motion reduction methods and can be leveraged to improve the designs. This includes better-informed fairlead placement and the reduction of aerodynamic load variability. In this paper, we propose a two-fold approach for the identification of the ICR: an analytical solution in the initial static equilibrium position, and a time-domain numerical approach for dynamic analysis in regular and irregular waves to understand the motion patterns and ICR sensitivity to environmental conditions. Results show that the ICR of FOWT depends on wave frequency and, at low frequencies, on wave height, due to the nonlinear viscous drag and mooring loads. An unexpected but interesting result is that the surge-heave-pitch coupling introduced by the mooring system leads to a dynamic phenomenon of signal distortion known as ”clipping” in the nonlinear audio signal processing area, which, through the introduction of higher harmonics, is responsible for the ICR sensitivity to motion amplitude. Ship Design, Production and Operations

A realistic deep low-enthalpy geothermal reservoir based on real data with high detail and complicated sedimentary structure is utilized to perform sensitivity analyses of the geological features influencing reservoir properties. We perform simulations using the Delft Advanced Research Terra Simulator (DARTS). Compelling numerical performance of DARTS makes it suitable for handling a large ensemble of models including efficient sensitivity and uncertainty analyses. The major finding is that shale facies, generally ignored in hydrocarbon reservoir simulations, can significantly extend the predictive lifetime of geothermal reservoirs exploited by deep well doublets. It is important to accurately account for the shale facies in the simulation, though with an additional computational overhead. The overburden layers can improve doublet performance, but the impact depends on reservoir heterogeneity. In addition, heterogeneity will also divert the flow path with even a minor shift in the well placement. The discharge rate, an essential parameter of geothermal operation strategy, inversely corresponds to the doublet lifetime but positively correlates with the energy production for studied parameter ranges. Low sensitivity of doublet lifetime to vertical-horizontal permeability ratio and permeability-porosity correlation is observed. All these systematic findings for a realistic geothermal field with characterization at unprecedented level of detail can help to provide a general guideline for forward simulation and farther improve the profitability of geothermal energy production in realistic deep geothermal reservoirs through computer-assisted modeling and optimization.

Raytracing-based methods are widely used for quantifying irradiation on building surfaces. Urban 3D surface models are necessary input for raytracing simulations, which can be generated from open-source point cloud data with the help of surface reconstruction algorithms. In research and engineering practice, various algorithms are being used for this purpose; each leading to different mesh topologies and corresponding performance. This paper compares the impacts of four different reconstruction algorithms by investigating their performance using DAYSIM raytracing simulations. The analysis is carried out for five configurations with various urban morphologies. Results show that the reconstructed models consistently underestimate the shading influence due to geometrical shrinkages that emerge from the various model generation procedures. The explicit algorithms, with Generic Delaunay a notable example, have better performance with less embedded error than the implicit algorithms in both daily and annual simulations. Results also show that diffuse irradiance is responsible for larger contributions to the overall error than direct components. This effect becomes more prominent when modeling reflected irradiation in urban environments. Additionally, the work shows that solar elevation and shading geometry types also affect the error magnitude. The paper concludes by providing reconstruction algorithm selection criteria for photovoltaic practitioners and urban energy planners.

We report on the relative performances of two large-scale luminescent solar concentrator (LSC) noise barriers placed in an outdoor environment monitored for over a year. Comparisons are made for the performances of a number of attached photovoltaic cells with changing spectral illumination, cloud cover conditions and other seasonal variations, and the temperatures of the cells. Differences in performance are attributed to the positioning of the panels, whether facing North/South or East/West. In general, the panels facing East/West run cooler than those facing North/South. The LSCs in both orientations appear to perform more efficiently under lower light conditions: one factor contributing to this increased performance is better spectral matching of the solar spectrum under cloudy conditions to the absorption spectrum of the embedded fluorescent dye. This work is a step forward in the characterization of a largescale LSC device, and suggests predictions of performance of devices could be made for any location given sufficient knowledge of the illumination conditions, and provides an important step towards the commercialization of these alternative solar energy generators for the urban setting.