Tribological challenges of scaling up tidal turbine blades

Generating electricity from renewable resources (wind, wave and tidal) is of increasing interest. Of all marine renewables, tidal energy, by comparison, possesses the higher persistency and predictability over long time scales and the higher density of water than air results in greater power output from a tidal turbine than a wind turbine with similar dimensions. However, due to the nature of the tides, developing a reliable device for such environments, especially with an increased rotor diameter, raises more challenges to be addressed including the tribological challenges such as sediment erosion, cavitation erosion and their possible synergistic effects on the tidal turbine blades. This research focuses on testing and developing materials for improved tribological performance in tidal environments. This includes producing a variety of composite materials with different fibres and layouts reinforcement to evaluate two main tribological issues of composite materials in tidal environments: matrix cutting and reinforcement fracture using a loped test rig, which measures the effects of impact angle, particle size and concentrations at different tip speeds. The test samples are analysed using scanning electron microscopy (SEM) to conduct a surface topography and characterisation

Tribology of tidal turbine blades : impact angle effects on erosion of polymeric coatings in sea water conditions

Tidal energy, of all marine renewables energies, possesses higher persistency and predictability over long time scales. Due to the aggressive marine environment, there are barriers in the development of tidal power generation technology. In particular, with regard to increased rotor diameter, the selection of material presents significant challenges to be addressed including the tribological environment, such as solid particle erosion, cavitation erosion, the effect of high thrust loading on the turbine blade tips, and the synergy between sea water conditions and such tribological phenomena. This research focuses on producing and testing a variety of advanced materials and surface coatings to investigate two main tribological issues in tidal environments: matrix cutting and reinforcement fracture. In our previous work, a G10 epoxy glass laminate was tested in this environment and the results revealed tribological issues. In this present work, G10 epoxy glass laminate base erosion resistant polymeric coatings have been tested for the range of sand particles size in our our previous work and in NaCl solution. The test results reveal that the coating has enhanced the quality of performance of the composite with respect to tribological behaviour, and has diminished the synergy between sea water and tribological phenomena. This indicates progress toward the selection of advanced materials to manufacture tidal turbine blades

Mapping synergy of erosion mechanisms of tidal turbine composite materials in sea water conditions

Tidal energy, of all marine renewables energy, possesses higher persistency and predictability over long time scales. Moreover, the higher density of water than air also results in greater power output from a tidal turbine than a wind turbine with similar dimensions. Due to the aggressive marine environment, there are barriers in the development of tidal power generation technology. In particular, with regard to increased rotor diameter, the selection of material presents significant challenges to be addressed including the tribological environment, such as solid particle erosion, cavitation erosion, the effect of high thrust loading on the turbine blade tips, and the synergy between sea water conditions and such tribological phenomena. This research focuses on producing and testing a variety of composite materials with different fibres and reinforcement layouts to evaluate two main tribological issues in tidal environments: matrix cutting and reinforcement fracture. A slurry pot test rig was used to measures the effects of different impact angles and particles sizes at constant tip speeds

Impact angle effects on erosion maps of GFRP : applications to tidal turbines

Tribology in marine renewable technologies has become of increasing interest due to the implications for developing improved materials for tidal and wave energy conversion devices. This on-going research mainly focuses on tidal devices; the materials of interest are primarily polymer based composite materials that are used to provide structural integrity while reducing weight. These are specifically applied to turbine blades to withstand the high impact loadings in sea water conditions. At present, current materials in test trials have demonstrated some limitations in service. In this paper, some advanced experimental research has been carried out to investigate the tribological mechanisms of potential candidate composite materials to be used in tidal turbines by firstly considering the effects of various erosion parameters on the degradation modes, with and without particles in still and sea water conditions. The erosion mechanisms of composite materials used in tidal turbine blades have been evaluated using Scanning Electron Microscopy techniques to analyse the surface morphologies following testing in water representative of the constituents of coastal sea water. Generic erosion maps and the mechanistic maps have been constructed as a key to identify regions of minimum erosion for the operating conditions and to identify the significant effect of the sea water environment on the degradation of the composite. This research outcome will further help us to deeply understand and identify the erosion rates at different impact velocities and angles

Variations in community perceptions of ecosystem services within the Tana River estuary, Kenya: Implications for ocean governance

Coastal communities in the Tana estuary, Kenya, rely on a variety of economic sectors linked to ecosystem services, including small-scale fisheries (SSF), commercial prawn fisheries, and tourism. Despite its environmental and social importance, the estuary has been negatively impacted by overexploitation, pollution, and climate change. As a result, developing integrated management approaches for this area is a priority. The integrated approach to ecosystem services (ES) evaluation has widespread support because it emphasizes people’s views of ecological value to human well-being and aims to provide a solution to the rapid depletion of our planet’s natural resources. This study applied mixed methods to understand the perspectives of the communities on ES. It was hypothesized that perceptions of ES differ across communities with different socioeconomic characteristics, and this hypothesis was tested in two communities (Ozi and Kipini) that share the same ecosystem but have different socioeconomic characteristics. Kipini is an area near the ocean, whereas Ozi is a rural area further upstream. Differences were noted in the valuation of cultural services, while there were similarities in provisioning and regulating services. Mangroves, other trees, and river systems were considered to have higher ES provision than the ocean, floodplains, and settlement areas. The Ozi community ranked the ocean higher than the Kipini community, even though Ozi was located further upstream from the ocean; consequently, the perception that communities benefit more from resources that they are close to could be false. The relevance of using social ES identification to determine the distribution of benefits from coastal ES is highlighted in this study and will be beneficial for informing decision-making and developing all-inclusive governance structures

Neural correlates of enhanced visual short-term memory for angry faces: An fMRI study

Copyright: © 2008 Jackson et al.Background: Fluid and effective social communication requires that both face identity and emotional expression information are encoded and maintained in visual short-term memory (VSTM) to enable a coherent, ongoing picture of the world and its players. This appears to be of particular evolutionary importance when confronted with potentially threatening displays of emotion - previous research has shown better VSTM for angry versus happy or neutral face identities.Methodology/Principal Findings: Using functional magnetic resonance imaging, here we investigated the neural correlates of this angry face benefit in VSTM. Participants were shown between one and four to-be-remembered angry, happy, or neutral faces, and after a short retention delay they stated whether a single probe face had been present or not in the previous display. All faces in any one display expressed the same emotion, and the task required memory for face identity. We find enhanced VSTM for angry face identities and describe the right hemisphere brain network underpinning this effect, which involves the globus pallidus, superior temporal sulcus, and frontal lobe. Increased activity in the globus pallidus was significantly correlated with the angry benefit in VSTM. Areas modulated by emotion were distinct from those modulated by memory load.Conclusions/Significance: Our results provide evidence for a key role of the basal ganglia as an interface between emotion and cognition, supported by a frontal, temporal, and occipital network.The authors were supported by a Wellcome Trust grant (grant number 077185/Z/05/Z) and by BBSRC (UK) grant BBS/B/16178

Posthuman literacies: young children moving in time, place and more-than-human worlds.

This paper examines the potential of posthumanism to enable a reconceptualization of young children’s literacies from the starting point of movement and sound in the more-than-human world. We propose movement as communicative practice that always occurs as a more complex entanglement of relations within more-than-human worlds. Through our analysis, an understanding of sound emerged as a more-than-human practice that encompasses children’s linguistic and non-linguistic utterances, and which occurs through, with, alongside movement. This paper draws on data from two different research studies; in the first two year old children in the UK banged on drums and marched in a museum. In the second study, two young children in Australia chose sites for their own research and produce a range of emergent literacies from vocalisation and ongoing stories to installations. We present examples of ways in which speaking, gesturing and sounding, as emergent literacy practices, were not so much about transmitting information or intentionally designed signs, but about embodied and sensory experiences in which communication about and in place occurred through the body being and moving in place. This paper contributes to the field of posthuman early childhood literacies by foregrounding movement as central to in-the-moment becoming. Movement and sound exist beyond parameters of human perception, within a flat ontology (MacLure, 2013) in which humans are decentred and everything exists on the same plane, in constant motion. Starting from movement in order to conceptualise literacy offers, therefore, an expanded field of inquiry into early childhood literacy. In the multimodal literacy practices analysed in this paper, meaning and world emerge simultaneously, offering new forms of literacy and representation and suggesting possibilities for defining or conceptualising literacy in ways that resist anthropocentric or logocentric framings

FE65 Binds Teashirt, Inhibiting Expression of the Primate-Specific Caspase-4

The Alzheimer disease (AD) amyloid protein precursor (APP) can bind the FE65 adaptor protein and this complex can regulate gene expression. We carried out yeast two-hybrid studies with a PTB domain of FE65, focusing on those genes that might be involved in nuclear signaling, and identified and validated Teashirt proteins as FE65 interacting proteins in neurons. Using reporter systems, we observed that FE65 could simultaneously recruit SET, a component of the inhibitor of acetyl transferase, and Teashirt, which in turn recruited histone deacetylases, to produce a powerful gene-silencing complex. We screened stable cell lines with a macroarray focusing on AD-related genes and identified CASP4, encoding caspase-4, as a target of this silencing complex. Chromatin immunoprecipitation showed a direct interaction of FE65 and Teashirt3 with the promoter region of CASP4. Expression studies in postmortem samples demonstrated decreasing expression of Teashirt and increasing expression of caspase-4 with progressive cognitive decline. Importantly, there were significant increases in caspase-4 expression associated with even the earliest neuritic plaque changes in AD. We evaluated a case-control cohort and observed evidence for a genetic association between the Teashirt genes TSHZ1 and TSHZ3 and AD, with the TSHZ3 SNP genotype correlating with expression of Teashirt3. The results were consistent with a model in which reduced expression of Teashirt3, mediated by genetic or other causes, increases caspase-4 expression, leading to progression of AD. Thus the cell biological, gene expression and genetic data support a role for Teashirt/caspase-4 in AD biology. As caspase-4 shows evidence of being a primate-specific gene, current models of AD and other neurodegenerative conditions may be incomplete because of the absence of this gene in the murine genome