The effect of viscosity on the maximisation of electrical power from a wave energy converter under predictive control

In this paper, the non-linear effects of viscosity on the performance of a Wave Energy Converter (WEC) system are analysed. A standard linear Model Predictive Control (MPC) is used to show the negative effects that the unaccounted non-linear viscosity force in the hydrodynamic system has on the power absorption. A non-linear MPC (NLMPC) is then implemented, where the non-linear viscosity effects are included in the optimisation. A linear drag coefficient estimate of the non-linear viscosity is then included in the linear MPC; creating a Linear Viscous Model Predictive Control. When constraints are incorporated, it is shown that a single choice of the linear viscous drag coefficient for use within the linear MPC can provide comparable results to the non-linear MPC approach, over a wide range of sea states

The effect of model inaccuracy and move-blocking on the performance of a wave-to-wire wave energy converter , under economic predictive control

In this paper, an economic Model Predictive Control (MPC) is used to investigate the effects that arise from the model mismatch between the control and the system. It is shown that the average electrical power is affected by the modelling discrepancies, but that the performance is still acceptable. A move-blocking technique is incorporated into the structure of the control horizon of the MPC, where the move-blocking decreases the computational burden whilst maintaining system performance, hence drastically reducing the optimisation solving time. The MPC with the move-blocking incorporated is then tested on the most significant mismatch, where it is shown that the control horizon of the MPC can be drastically reduced while maintaining system performance

Wave to wire power maximisation from a wave energy converter

In this paper a back-to-back voltage source converter controlled linear permanent magnet generator (LPMG) is utilised as the power take off (PTO) for a point absorber wave energy converter system (WEC). It is shown that reactive control which seems promising when an ideal PTO is assumed, is actually infeasible with a real PTO as the electrical losses of the LPMG are excessive when the wave frequency is lower than the natural frequency. A Zero Order Hold (ZOH) and First Order Hold (FOH) Model Predictive Control (MPC) which maximises the mechanical power is first utilised. The two MPC systems show that more electrical power is extracted for a lower horizon when the MPC is optimised for mechanical power. The electrical losses from the LPMG and voltage source converter (VSC) are then incorporated in the cost function of the MPC systems and demonstrates significant improvements in the electrical power extracted when compared to the electrical power extracted via mechanical power optimisation. PTO force and heave displacement constraints are then incorporated into the optimisation, to further demonstrate the limitations of performance when a realistic PTO is utilised. It is shown here that the electrical power can be maximised, whilst the PTO force and heave displacement are shown to be within limits. The power quality from the ZOH MPC is then compared to the power quality from the FOH MPC

Electrical power optimisation of grid-connected wave energy converters using economic predictive control

This thesis investigates the advanced control algorithms used for optimally extracting energy from a wave-to-wire wave energy converter system. The research focuses on the wave-to-wire system model as a whole, instead of its separate subsystems. This allows maximum exportation of average electrical power onto the grid from a wave energy array, with minimum mechanical and electrical constraint infringement and acceptable power quality. An economic model predictive control algorithm is first described for a wave-to-DClink system with a single wave energy converter connected to a simulated linear generator. This work investigates the importance of including the linear generator’s resistive losses in the cost function. Linear mechanical and non-linear electrical constraints are introduced into the model predictive control algorithm, where the effects on the average electrical power harvest are presented. A model predictive control algorithm with a field weakening enabled cost function is introduced, where the feasible region is extended for low DC-link voltages. By including a uni-directional power flow constraint into the algorithm, the power exported onto the DC-link bus is guaranteed to be positive. A detailed analysis of the effect of uncertainty on performance was carried out, where the controller’s internal model is mismatched from the simulation model. The results indicate that the high fidelity of the controller’s internal model is not required and that a sufficient amount of average electrical power is extractable. A non-linear model predictive control algorithm is described, where the non-linear viscosity forces are incorporated into the control algorithm - extracting maximum energy from a viscous system. It was shown that given the constraints on the system that the non-linear action of the control algorithm could be approximated, a linear model predictive control algorithm with an estimated viscous term. This produces a computationally inexpensive control algorithm, while maintaining good performance. A move-blocking was also introduced to further reduce the computation expense. Finally the thesis considers multiple point absorbers in an array and analyses the potential benefits of using either decentralised or centralised model predictive control algorithms. This demonstrated that the performance of a decentralised controller becomes comparable to the centralised controller when linear mechanical constraints are introduced into the viscous hydrodynamic array. However, when an upper power limit is introduced into the control algorithm the advantages of the centralised controller become apparent

An analysis of the potential benefits of centralised predictive control for optimal electrical power generation from wave energy arrays

This work focuses on an array of point absorbers, with linear permanent magnet generators (LPMG) connected to the grid via back to back voltage source converters, controlled using economic model predictive control (MPC) that produces optimal electrical power generation. The main contribution of this paper is the comparison of the performance provided by using either a centralised or decentralised MPC scheme. In this study, it is shown how the inclusion of viscosity and system constraints limits the benefits to be obtained by the use of a centralised control scheme. Indeed, it was shown that a decentralised MPC scheme was sufficient for the provision of close to optimum electrical power extraction from the array when there was a reasonable separation between WEC devices. It was shown that the introduction of power constraints, either locally at each device or globally for the entire array, improved the quality of the power exported to the grid. Importantly, it was shown that from the viewpoint of power quality, that global predictive control of the wave energy array offered significant benefits over local decentralised control in increasing the average to peak power ratio of power exported to the grid

Abiraterone acetate plus prednisolone for metastatic patients starting hormone therapy: 5-year follow-up results from the STAMPEDE randomised trial (NCT00268476)

Abiraterone acetate plus prednisolone (AAP) previously demonstrated improved survival in STAMPEDE, a multiarm, multistage platform trial in men starting long-term hormone therapy for prostate cancer. This long-term analysis in metastatic patients was planned for 3 years after the first results. Standard-of-care (SOC) was androgen deprivation therapy. The comparison randomised patients 1:1 to SOC-alone with or without daily abiraterone acetate 1000 mg + prednisolone 5 mg (SOC + AAP), continued until disease progression. The primary outcome measure was overall survival. Metastatic disease risk group was classified retrospectively using baseline CT and bone scans by central radiological review and pathology reports. Analyses used Cox proportional hazards and flexible parametric models, accounting for baseline stratification factors. One thousand and three patients were contemporaneously randomised (November 2011 to January 2014): median age 67 years; 94% newly-diagnosed; metastatic disease risk group: 48% high, 44% low, 8% unassessable; median PSA 97 ng/mL. At 6.1 years median follow-up, 329 SOC-alone deaths (118 low-risk, 178 high-risk) and 244 SOC + AAP deaths (75 low-risk, 145 high-risk) were reported. Adjusted HR = 0.60 (95% CI: 0.50-0.71; P = 0.31 × 10−9) favoured SOC + AAP, with 5-years survival improved from 41% SOC-alone to 60% SOC + AAP. This was similar in low-risk (HR = 0.55; 95% CI: 0.41-0.76) and high-risk (HR = 0.54; 95% CI: 0.43-0.69) patients. Median and current maximum time on SOC + AAP was 2.4 and 8.1 years. Toxicity at 4 years postrandomisation was similar, with 16% patients in each group reporting grade 3 or higher toxicity. A sustained and substantial improvement in overall survival of all metastatic prostate cancer patients was achieved with SOC + abiraterone acetate + prednisolone, irrespective of metastatic disease risk group

Diving into the vertical dimension of elasmobranch movement ecology

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species. Elasmobranchs displayed high intra- and interspecific variability in vertical movement patterns. Substantial vertical overlap was observed for many epipelagic elasmobranchs, indicating an increased likelihood to display spatial overlap, biologically interact, and share similar risk to anthropogenic threats that vary on a vertical gradient. We highlight the critical next steps toward incorporating vertical movement into global management and monitoring strategies for elasmobranchs, emphasizing the need to address geographic and taxonomic biases in deployments and to concurrently consider both horizontal and vertical movements

Diving into the vertical dimension of elasmobranch movement ecology

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species. Elasmobranchs displayed high intra- and interspecific variability in vertical movement patterns. Substantial vertical overlap was observed for many epipelagic elasmobranchs, indicating an increased likelihood to display spatial overlap, biologically interact, and share similar risk to anthropogenic threats that vary on a vertical gradient. We highlight the critical next steps toward incorporating vertical movement into global management and monitoring strategies for elasmobranchs, emphasizing the need to address geographic and taxonomic biases in deployments and to concurrently consider both horizontal and vertical movements

Plant-symbiotic fungi as chemical engineers: multi-genome analysis of the Clavicipitaceae reveals dynamics of alkaloid Loci

The fungal family Clavicipitaceae includes plant symbionts and parasites that produce several psychoactive and bioprotective alkaloids. The family includes grass symbionts in the epichloae clade (Epichloë and Neotyphodium species), which are extraordinarily diverse both in their host interactions and in their alkaloid profiles. Epichloae produce alkaloids of four distinct classes, all of which deter insects, and some—including the infamous ergot alkaloids—have potent effects on mammals. The exceptional chemotypic diversity of the epichloae may relate to their broad range of host interactions, whereby some are pathogenic and contagious, others are mutualistic and vertically transmitted (seed-borne), and still others vary in pathogenic or mutualistic behavior. We profiled the alkaloids and sequenced the genomes of 10 epichloae, three ergot fungi (Claviceps species), a morning-glory symbiont (Periglandula ipomoeae), and a bamboo pathogen (Aciculosporium take), and compared the gene clusters for four classes of alkaloids. Results indicated a strong tendency for alkaloid loci to have conserved cores that specify the skeleton structures and peripheral genes that determine chemical variations that are known to affect their pharmacological specificities. Generally, gene locations in cluster peripheries positioned them near to transposon-derived, AT-rich repeat blocks, which were probably involved in gene losses, duplications, and neofunctionalizations. The alkaloid loci in the epichloae had unusual structures riddled with large, complex, and dynamic repeat blocks. This feature was not reflective of overall differences in repeat contents in the genomes, nor was it characteristic of most other specialized metabolism loci. The organization and dynamics of alkaloid loci and abundant repeat blocks in the epichloae suggested that these fungi are under selection for alkaloid diversification. We suggest that such selection is related to the variable life histories of the epichloae, their protective roles as symbionts, and their associations with the highly speciose and ecologically diverse cool-season grasses

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure