Aerodynamic and aeroacoustic investigation of vertical axis wind turbines with different number of blades using mid-fidelity and high-fidelity methods

The aerodynamics and aeroacoustics of small-scale Darrieus vertical axis wind turbine (VAWT) are investigated at chord-based Reynolds number below 4e5. A statistical temporal and grid convergence study is conducted to analyse the thrust and torque coefficients. Four different VAWTs with different numbers of blades (1, 2, 3, and 4) are investigated using both the high-fidelity Lattice Boltzmann Method (LBM) and mid-fidelity Lifting Line Free Vortex Wake (LLFVW) method. The statistical temporal convergence is achieved much earlier for the 1-bladed rotor than for the 3-bladed rotor, using both methods. Power performance analysis reveals that VAWTs with more blades generate more power at lower Tip Speed Ratios (TSRs), while VAWTs with fewer blades generate more power at higher TSRs. The aerodynamic efficiency of each blade decreases as the number of blades increases, leading to a decreased amplitude of rotor loading variation in a single rotation. Both the mid-fidelity LLFVW and high-fidelity LBM capture these physical trends well. However, LLFVW predicts lower peak thrust and torque values in a single rotation and higher streamwise velocities in the wake, as compared to LBM. Moreover, the former predicts higher average power output than the latter, and the discrepancy increases as the number of blades increases. In terms of noise, at constant TSR, low-frequency BPF noise is found to be higher in VAWTs with fewer blades, while high-frequency noise is found to be higher in VAWTs with more blades. Overall Sound Pressure Level values revealed that overall noise increased with an increase in the number of blades except for the 4-bladed VAWT for which the noise decreased

To examine appropriate deep-retrofit practice using simulation results in an EU-funded urban regeneration project

This paper is based on a recently completed feasibility research - report of the Passivhaus standard retrofitting innovation activities - for the EU Horizon 2020 project REMOURBAN (REgeneration MOdel for accelerating the smart URBAN transformation). REMOURBAN is a major Future Cities demonstrator project supported by an investment of EU Lighthouse project scheme [1]. A block of terraced houses, which is one of the eight archetypes to be retrofitted at Nottingham demo site, will be cost-effectively retrofitted to a high energy-efficiency standard. Both static and dynamic simulation results play important roles in identifying appropriate retrofit standards and practice to achieve expected energy savings for such a major investment project. This paper aims to explore the building simulation effect on predicting the improvement potential in terms of energy savings under various refurbishment scenarios in the early project stage. The current feasibility study ushers the next project phases of implementation and real-time field monitoring, when detailed simulations are also expected to play important roles

Expert survey and classification of tools for modeling and simulating hybrid energy networks

Sector coupling is expected to play a key role in the decarbonization of the energy system by enabling the integration of decentralized renewable energy sources and unlocking hitherto unused synergies between generation, storage and consumption. Within this context, a transition towards hybrid energy networks (HENs), which couple power, heating/cooling and gas grids, is a necessary requirement to implement sector coupling on a large scale. However, this transition poses practical challenges, because the traditional domain-specific approaches struggle to cover all aspects of HENs. Methods and tools for conceptualization, system planning and design as well as system operation support exist for all involved domains, but their adaption or extension beyond the domain they were originally intended for is still a matter of research and development. Therefore, this work presents innovative tools for modeling and simulating HENs. A categorization of these tools is performed based on a clustering of their most relevant features. It is shown that this categorization has a strong correlation with the results of an independently carried out expert review of potential application areas. This good agreement is a strong indicator that the proposed classification categories can successfully capture and characterize the most important features of tools for HENs. Furthermore, it allows to provide a guideline for early adopters to understand which tools and methods best fit the requirements of their specific applications

A multi-energy system optimisation software for advance process control using hypernetworks and a micro-service architecture

This paper describes a multi-energy system optimisation software, “Sustainable Energy Management System” (SEMS), developed as part of a Siemens, Greater London Authority and Royal Borough of Greenwich partnership in collaboration with the University of Nottingham, Nottingham Trent University and Imperial College London. The software was developed for application at a social housing estate in Greenwich, London, as part of the Borough’s efforts to retrofit the energy systems and building fabric of its housing stock. Its purpose is to balance energy across vectors and networks through day-ahead forecasting and optimisations that can be interpreted as control outputs for energy plant such as a water source heat pump, district heating pumps and values, power switchgear, gas boilers, a thermal store, electric vehicle chargers and a photovoltaic array. The optimisation objectives are to minimise greenhouse gas emissions and operational cost. The tool uses Hypernetwork Theory based orchestration coupled with a microservice architecture. The distributed nature of the design ensures flexibility and scalability. Currently, microservices have been programmed to forecast domestic heating demand, domestic electricity demand, electric vehicle demand, solar photovoltaic generation, ground temperature, and to run a day-ahead energy balance optimisation. This paper presents the results from both domestic heat and electricity demand forecasting, as well as the overall design and integration of the software with a physical system. The works build on that of O’Dwyer, et al. (2020) who developed a preliminary energy management software and digital twin. Their work acts as a foundation for this real-world commercialisation-ready program that integrates with physical assets

Improving thermal performance of an existing UK district heat network: a case for temperature optimization

This paper presents results of a research study into improving energy performance of small-scale district heat network through water supply and return temperature optimization technique. The case study involves establishing the baseline heat demand of the estate’s buildings, benchmarking the existing heat network operating parameters, and defining the optimum supply and return temperature. A stepwise temperature optimization technique of plate radiators heat emitters was applied to control the buildings indoor thermal comfort using night set back temperature strategy of 21/18 °C. It was established that the heat network return temperature could be lowered from the current measured average of 55 °C to 35.6 °C, resulting in overall reduction of heat distribution losses and fuel consumption of 10% and 9% respectively. Hence, the study demonstrates the potential of operating existing heat networks at optimum performance and achieving lower return temperature. It was also pointed out that optimal operation of future low temperature district heat networks will require close engagement between the operator and the end user through incentives of mutual benefit

Application of Richardson extrapolation method to aerodynamic and aeroacoustic characteristics of low Reynolds number vertical axis wind turbines

The aerodynamics and aeroacoustics of small scale Darrieus vertical axis wind turbines (VAWT) is investigated at chord-based Reynolds number below 1.5 × 105 . A grid convergence study is carried out for thrust, cross-streamwise force and torque coefficient, and for overall sound pressure level (OSPL). Four levels of grid refinement are used for that purpose. Richardson Extrapolation is used to estimate the continuum value of each parameter by using the three finest grids and calculate the grid convergence level. Four operational points for the Darrieus VAWT are investigated-tip speed ratios (TSR) of 0.37, 1.12, 2.23 and 2.79, keeping a constant freestream velocity of 5.07 m/sec. These values resemble an experimental campaign to validate the numerical results. Commercial software 3DS Simulia PowerFLOW 6-2020 is used, which uses the Lattice Boltzmann/Very Large Eddy Simulation (LB-VLES) method to perform high-fidelity CFD simulations, and the Ffowcs-Williams and Hawkings (FW-H) acoustic analogy to calculate the far-field noise. Results show that thrust, cross-streamwise force and OSPL have better grid convergence than torque. Furthermore, grid convergence is better at TSR = 2.23 than at other TSRs. Blades in the downwind half of rotation are found to always produce less thrust and torque than in the upwind half, due to the effect of VAWT wake on the former. The difference in values between the two halves increased with increasing TSR, in general, due to the wake getting stronger at higher TSR; the ratio of contribution between upwind and downwind halves went as high as 17.6 in case of thrust for TSR = 2.79. In terms of noise, higher TSR produced more noise than the lower TSR configuration due to an increase in unsteady blade loading with increasing TSR. About OSPL directivity on a circular array of points, noise is highest at the most upstream azimuth location corresponding to the location where blade loading is highest in a single rotation.</p

EXTERNAL FRP REINFORCEMENT OF DOUGLAS FIR BEAMS IN BENDING

The use of bonded Fiber Reinforced Polymer laminates for strengthening solid wood structural members is receiving increasing attention in recent years, especially for structural rehabilitation purposes, where existing solid members may present natural defects, significant inclination of the grain direction and initial cracking. The paper experimentally investigates the bending strengthening of solid Douglas Fir beams, with axis parallel or inclined to the grain direction, through the application of a Carbon Fiber Reinforced Polymer glued by an epoxy resin on the tension side of the beams only. Reinforcement thickness, presence and position of steel reinforcement in compression are also accounted as additional parameters. Finally, some beams were loaded till cracking, successively reinforced and re-loaded till failure to assess the effects of the reinforcement on a significantly damaged element. The increment in bending performances due to the application of CFRP is discussed, as well as the effectiveness of the addition of the metal reinforcement, also depending on the initial damage level of the beam. To the structural rehabilitation purposes, it is shown how large variations in mechanical performances of timber elements, due to natural defects of woods or to inclination of the grain direction, may be reduced by the introduction of the CFRP reinforcement

Uncertainty propagation and management of mixed uncertainties for multi-fidelity multi-disciplinary analysis of propeller with different blade sweep

A study on the uncertainty quantification and propagation in a multi-fidelity, multi-disciplinary framework, focusing on aerodynamics, aeroacoustics, and aeroelasticity in propeller blade design is presented. Employing the Lattice Boltzmann Method (LBM) for high-fidelity simulations and the Lifting Line Free Vortex Wake (LLFVW) and Finite Element Analyses (FEA) for mid-fidelity simulations, the study analyzes a 2-bladed, 0.3m diameter propeller using NACA4412 airfoil cross-section, across nine blade sweep configurations. It investigates the effects of two uncertain parameters: freestream velocity, using Interval analysis, and blade tip offset, using Monte Carlo Simulation. The differential analysis between mid and high-fidelity methods shows an uncertainty range of 13.83% to 30.32% for freestream velocity and 2% to 32.48% for blade tip offset, due to the inclusion of the mid-fidelity method. Using the Halton sampling method, it is demonstrated that the uncertainty in the sweep parameter is propagated differently across various performance metrics of the propeller. A backward sweep tends to increase both the mean (by 5-6 %) and uncertainty (by 2-4 %) in all performance parameters, suggesting a potential enhancement in performance but with increased risk. In contrast, a forward sweep reduces mean performance (by 2-3 %) and uncertainty (by 4-6 %) of all parameters except structural deflection, which shows an increasing trend (by 0.5-2 %). This indicates a more reliable aerodynamic and aeroacoustic performance but potentially less efficient operation and increased risk in structural integrity.This project has received funding from Innovate UK under Grant Agreement No 1000338

Effect of blade shape on aerodynamic and aeroacoustic characteristics of vertical axis wind turbines using mid-fidelity and high-fidelity methods

This research paper investigates the effect of different blade shapes on the aerodynamic and aeroacoustic characteristics of Darrieus Vertical Axis Wind Turbines (VAWTs). Three different VAWT blade shapes are investigated: Straight, Troposkein, and Helical, considering a chord-based Reynolds number of 1.73e+5 and at a constant tip speed ratio for all. The mid-fidelity Lifting Line Free Vortex Wake (LLFVW) method and the high-fidelity Lattice Boltzmann/Very Large Eddy Simulation (LB-VLES) method are employed. Power performance analysis reveals that the straight-bladed VAWT generates the highest power output (about 11% higher), followed by the helical and troposkein blade configurations. The helical-bladed rotor exhibits smoother thrust and torque distribution over a wider azimuthal angle range, as predicted by both methods. While both methods capture the same trends in thrust and torque values, the mid-fidelity LLFVW method predicts approximately 22% higher thrust and torque values and lower near-wake streamwise velocities as compared to the high-fidelity LBM. The LLFVW is unable to accurately capture the inherent 3D vortices in the VAWT flow-field and the effect of blade-vortex interaction (BVI) on the VAWT force-field, as compared to LBM. In terms of aeroacoustics, the troposkein VAWT produces the highest noise at lower frequencies (20-30 Hz), followed by the straight and helical VAWTs. However, the troposkein and helical VAWTs emit more noise at higher frequencies (500-2000 Hz) than the straight VAWT due to the higher intensity of BVI observed for the former.For the part of high-fidelity simulations, this project has received funding from the European Union’s Horizon 2020 Marie Curie zEPHYR research and innovation programme under grant agreement No EC grant 860101