Frequency and Stochastic Domain Models for Two Geometries of the IPS Wave Power Buoy

Frequency-domain analysis is applied to a geometry of the original IPS buoy device concept. The analysis is particularly useful in the early development stages to establish the response of power take-off mechanism characteristic parameters to different frequencies of the wave spectrum. Optimal mechanical damping and spring coefficients are computed for some parameters restrictions. Absorbed power, capture width and other variables, such as relative displacement,are computed for regular waves and these optimal mechanical coefficients. A stochastic model is developed in order to evaluate the IPS buoy behaviour for irregular waves’ conditions. This allows defining probability density functions for parameters that characterize the device’s behaviour. Assuming that the overall system behaviour is linear and that the surface elevation for irregular waves may be regarded as a stochastic process with a Gaussian probability density function, the variables that define the system behaviour, such as bodies’ displacements and velocities, will also hold a Gaussian probability density function. The average power extraction is computed for different sea state conditions.Aiming to enhance the device’s hydrodynamic performance, a new non-axisymmetric IPS geometry is conceived. Using the stochastic modelling approach, the device’s behaviour is studied for several wave directions and compared to the axisymmetric configuration’s behaviour

A new urban wind turbine blade design using a pressure-load inverse method

This paper presents the design methodology of a new wind turbine blade section that achieves high performance in urban environment by increasing the maximum lift. For this purpose, a turbomachine blade rows inverse design method was applied to obtain a new wind turbine blade section with constant pressure-load along the chord, at the design inlet angle. In comparison with conventional blade designs, the new blade section has increased maximum lift, reduced leading edge suction peak and controlled soft-stall behaviour,due to the strength reduction of the adverse pressure gradient on the blade suction surface.Wind tunnel experimental results confirmed the computational results

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Impact of different internal convection control strategies in a non-evacuated CPC collector performance

Over the last decade the technological advances observed in solar collector materials, namely better spectrally selective absorber coatings and ultra clear glass covers, contribute to performance improvements and translate into higher operational temperature ranges with higher efficiency values. While the use of Evacuated Tube Collectors (ETCs) is becoming widespread in the thermal conversion of solar energy, non-evacuated solar collectors still hold advantages at manufacturing, reliability and/or cost levels, making them interesting and competitive for a large range of applications, in particularly, in temperature ranges up to 80 C. However, these advantages have not prevented the major drawback of these collectors when compared to ETCs: thermal losses due to internal convection which prevent their general use in the range of operating temperatures up to 150 C. Insulation, double glazing or selective coatings can be used in non-evacuated collectors to reduce heat losses. To prevent internal convection losses in these solar collectors, different control strategies have been studied, such as the adoption of different inert gases within the collector cavity, physical barriers reducing air flow velocities over the absorber or cover surfaces or the use of concentration. In the present article, an assessment of adopting such internal convection control strategies in a CPC collector is presented. Each of the presented strategies is assessed in terms of the resulting collector optical and thermal characterization parameters and yearly collector yield. For this purpose, an integrated tool allowing the design, optical and thermal characterization of CPC collectors was developed

Estimation of generator electrical power output and turbine torque in modelling and field testing of OWC wave energy converters

The oscillating water column is one of the most tested and used wave energy converter types. It requires the use of an air turbine connected to an electrical generator. The deep understanding of all physical quantities of the energy chain components is based on transducers. The electrical generator efficiency is a key input to wave-to-wire numerical models for wave energy conversion to enable the industry to embark on projects with reliable data. Assembly of a standard torque meter is not feasible in prototypes following an industrial design. Therefore, the turbine shaft power must be calculated from the electrical generator dry-testing results at various rotational speeds and loads. This paper presents normalised data for estimating generator power output and turbine torque based on generator efficiency measurements. Experimental results show the electrical generator efficiency dependency on the rotational speed and load. A new kind of filter to post-process the raw data was used. The results will be used as a reference for wave-to-wire numerical models of oscillating water columns and post-processing the data from prototypes operating in real sea state conditions

Design of a new urban wind turbine airfoil using a pressure-load inverse method

This paper presents the design methodology of a new wind turbine airfoil that achieves high performance in urban environment by increasing the maximum lift. For this purpose, an inverse method was applied to obtain a new wind turbine blade section with constant pressure-load along the chord, at the design inlet angle. In comparison with conventional blade section designs, the new airfoil has increased maximum lift, reduced leading edge suction peak and controlled soft-stall behaviour, due to a reduction of the adverse pressure gradient on the suction side. Wind tunnel experimental results confirmed the computational results

Latching control of a floating oscillating-water-column wave energy converter

The OWC spar-buoy is an axisymmetric floating version of an oscillating-water-column (OWC) based device whose power take-off (PTO) system is an air turbine/generator set. Latching has been regarded as one of the most promising techniques to improve the efficiency of wave energy converters. In the case of the OWC spar-buoy, latching control is performed by opening/closing a high-speed stop valve installed in series with the turbine. The present paper has three main objectives. Firstly, to assess the performance improvements that can be achieved with a latching control strategy within a receding horizon framework. Secondly, to establish the practical requirements of this type of control by evaluating the sensitivity of the turbine power output to several receding horizon time intervals. Finally, to test and validate experimentally the proposed algorithms in a small-scale PTO test rig. All the experimental tests were performed considering irregular wave conditions.The research was partially funded by the European Community's Seventh Framework Programme under MARINET (Marine Renewables Infrastructure Network) initiative. This work was also funded by the Portuguese Foundation for Science and Technology (FCT) through IDMEC, under LAETA Pest-OE/EME/LA0022 and contract PTDC/EME-MFE/111763/2009. The first author was supported by FCT researcher grant No. IF/01457/2014. The fifth author was supported by the OceaNET project, which has received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement No. 607656