E.ON (United Kingdom)

A wave energy device operates in a wide range of sea states from low load to 4 to 8 times rated load over a wide speed range. Existing PTOs combine mechanical speed enhancers with conventional high speed electrical generator and power converter, with questions over reliability and cannot operate over wide operating ranges. The EU funded MEGA WAVE PTO project is addressing this challenge by developing an all-electric power take off incorporating three sub-systems: a contactless magnetic gear; the modular C-GEN generator; and modular power electronics. The rationale for the technology choice for the all electric power take off is summarised to provide context. An outline of the methodology is presented through six main themes ranging from engineering design, control and testing, to levelized cost, carbon footprint and supply chain analysis, all with the main aim to demonstrate a scalable, reliable and maintainable fully integrated all-electric modular PTO system customized for wave energy devices from kWs to MWs across the Blue Economy sector. Preliminary work from two deliverables completed in the first year are presented to show the design of a 1000 Nm magnetic gear prototype, and a framework for life-cycle assessment of wave devices to understand the potential impact of MEGA WAVE PTO on carbon footprint.

Abstract Performance testing of a 3-stage 9MW axial CO2 compressor has been successfully completed at the closed-loop CO2 compressor test facility at the University of Notre Dame. The design speed, inlet pressure, inlet temperature, and mass flowrate of the compressor was 19,800rpm, 2.77MPa, 98°C, and 125.9kg/s respectively. The compressor performance was evaluated from 60% to 100% of the design speed. Each speedline covered operating points from choke to near stall except for at 60% speed where the compressor was throttled into rotating stall. Blade tip clearance and blade vibrations were measured during the compressor operation to ensure the safety of the compressor. Calibrated capacitance probes were used to establish average running tip clearances of 0.38mm (1.2% of span), 0.5mm (1.9% of span), and 0.5mm (2.4% of span) for stage 1, stage 2, and stage 3 respectively. Blade vibrations were measured using tip timing probes. A six engine-order synchronous blade vibration of the first bending mode was observed at the 1st stage rotor around 73%–82% speed. Stall testing at 60% speed revealed a single stall cell which extends from the 1st stage rotor to the 3rd stage rotor, and is rotating at 60.4% of the shaft speed. The compressor stall at 60% caused significant shaft vibration. Hence, the stall line at 70% and higher speeds was extrapolated from stall testing at 60% and lower speed to avoid potential damage of the test rig from stall or surge. The measured peak isentropic efficiency of the compressor was 91.5%, 91.1%, 90.6%, 90.0%, 85.3% at 60%, 70%, 83%, 90%, and 100% speeds respectively. Considering increases in efficiency with decreases in mass flowrate and that the performance test above 70% was stopped with some safety distance away from the stall point to avoid damage, the peak isentropic efficiency is expected to be above or close to 90% at 100% speed as well. The measured performance successfully demonstrated the performance benefit and usefulness of the axial compressor for grid-scale energy systems such as pumped thermal energy storage (PTES).

Enormous natural gas reserves in the Eastern Mediterranean have attracted the attention of the international energy majors. The region, however, remains one of the most under-explored and -exploited regions in the world. Numerous technical, commercial, legal and political challenges need to be overcome for these resources to be exploited and exported. This article examines the key commercial and legal challenges the region faces, and proposes possible ways to overcome these challenges by discussing the international law on the delimitation of maritime boundaries and the customary international law obligations of states in the region to resolve delimitation disputes peacefully, to make every effort to enter into provisional arrangements of a practical nature pending agreement on final delimitation and to refrain from unilaterally exploiting natural resources in disputed maritime zones.

A systematic design of adaptive waveform for Wireless Power Transfer (WPT) has recently been proposed and shown through simulations to lead to significant performance benefits compared to traditional non-adaptive and heuristic waveforms. In this study, we design the first prototype of a closed-loop wireless power transfer system with adaptive waveform optimization based on Channel State Information acquisition. The prototype consists of three important blocks, namely the channel estimator, the waveform optimizer, and the energy harvester. Software Defined Radio (SDR) prototyping tools are used to implement a wireless power transmitter and a channel estimator, and a voltage doubler rectenna is designed to work as an energy harvester. A channel adaptive waveform with 8 sinewaves is shown through experiments to improve the average harvested DC power at the rectenna output by 9.8% to 36.8% over a non-adaptive design with the same number of sinewaves.

Embedding tidal turbines within simulations of realistic large-scale tidal flows is a highly multi-scale problem that poses significant computational challenges. Here this problem is tackled using actuator disc momentum (ADM) theory and Reynolds-averaged Navier–Stokes (RANS) with, for the first time, dynamically adaptive mesh optimisation techniques. Both k−ω and k−ω SST RANS models have been developed within the Fluidity framework, an adaptive mesh CFD solver, and the model is validated against two sets of experimental flume test results. A brief comparison against a similar OpenFOAM model is presented to portray the benefits of the finite element discretisation scheme employed in the Fluidity ADM model. This model has been developed with the aim that it will be seamlessly combined with larger numerical models simulating tidal flows in realistic domains. This is where the mesh optimisation capability is a major advantage as it enables the mesh to be refined dynamically in time and only in the locations required, thus making optimal use of limited computational resources.

Ultrasonic inspection of highly scattering materials presents challenges for industry. This article describes a Finite Element modelling methodology to simulate wave propagation within polycrystalline materials. Concerns are answered regarding its required mesh sampling and ability to capture the complex scattering physics. It is shown that grain scattering phenomena are closely reproduced across a range of scattering regimes. The procedure is subsequently applied to investigate the optimal configuration of an array inspecting such a material. It is found that in certain situations, separating emitter and receiver can be advantageous as this reduces the received backscatter.

An evaluation has been made of a number of contrasting atmospheric chemical transport models, of varying complexity, applied to estimate sulphur and nitrogen deposition in the UK. The models were evaluated by comparison with annually averaged measurements of gas, aerosol and precipitation concentrations from the national monitoring networks. The models were evaluated in relation to performance criteria. They were generally able to satisfy a criterion of ‘fitness for purpose’ that at least 50% of modelled concentrations should be within a factor of two of measured values. The second criterion, that the magnitude of the normalised mean bias should be less than 20%, was not always satisfied. Considering known uncertainties in measurement techniques, this criterion may be too strict. Overall, simpler models were able to give a good representation of measured gas concentrations whilst the use of dynamic meteorology, and complex photo-chemical reactions resulted in a generally better representation of measured aerosol and precipitation concentrations by more complex models.The models were compared graphically by plotting maps and cross-country transects of wet and dry deposition as well as calculating budgets of total wet and dry deposition to the UK for sulphur, oxidised nitrogen and reduced nitrogen. The total deposition to the UK varied by ±22–36% amongst the different models depending on the deposition component. At a local scale estimates of both dry and wet deposition for individual 5 km × 5 km model grid squares were found to vary between the different models by up to a factor of 4.

Many proposed clean coal technologies for power generation couple a gasification process with a gas turbine combined cycle unit. In the gasifier, the coal is converted into a syngas which is then cleaned and fired before entering the turbine. A problem is that coal-derived syngases may contain alkali metal impurities that combine with the sulfur and chlorine from the coal to form salts that deposit on the turbine blades, causing corrosion. This paper describes a new model, applicable to most types of coal, for predicting the dewpoint temperatures and deposition rates of these sodium and potassium salts. When chlorine is present the main alkali species in the mainstream gas flow are the chlorides; but when chlorine is absent, the superoxides dominate. However, because the high-pressure turbine blades are film-cooled, they are at much lower temperatures than the mainstream gas flow and analysis then shows that the deposit is composed almost entirely of the sulfates in either liquid or solid form. This is true whether or not chlorine is present. Detailed calculations using the new model to predict the alkali salt deposition rates on three stages of an example utility turbine are presented. The calculations show how the dewpoint temperatures and deposition rates vary with the gas-phase chlorine and sulfur levels as well as with the concentrations of sodium and potassium. It is shown that the locations where corrosion is to be expected vary considerably with the type of coal and the levels of impurities present.