Structural analysis of a fibre-reinforced composite blade for a 1 MW tidal turbine rotor under degradation of seawater.

This paper presents a structural performance study of a fibre-reinforced composite blade for a 1 MW tidal turbine rotor blade that was designed for a floating tidal turbine device. The 8-m long blade was manufactured by ÉireComposites Teo and its structural performance was experimentally evaluated under mechanical loading in the Large Structures Research Laboratory at the University of Galway. Composite coupons, applied with an accelerated ageing process, were tested to evaluate the influence of seawater ageing effects on the performance of the materials. The material strength of the composites was found to have a considerable degradation under the seawater ingress. As part of the design stage, a digital twin of the rotor blade was developed, which was a finite-element model based on layered shell elements. The finite-element model was verified to have good accuracy, with a difference of 4% found in the blade tip deflection between the physically measured test results in the laboratory and numerical prediction from the model. By updating the numerical results with the material properties under seawater ageing effects, the structural performance of the tidal turbine blade under the working environment was studied. A negative impact from seawater ingress was found on the blade stiffness, strength and fatigue life. However, the results show that the blade can withstand the maximum design load and guarantee the safe operation of the tidal turbine within its design life under the seawater ingress.

Tidal stream to mainstream: mechanical testing of composite tidal stream blades to de-risk operational design life.

Tidal energy has seen a surge of interest in recent years with several companies developing technology to harness the power of the world's oceans where the operational capacity in Europe was over 11 MW in 2020. One such developer is the partnership of SCHOTTEL Hydro (Germany) and Sustainable Marine (UK) who have developed a scalable multi-turbine device equipped with 70 kW turbines and capable of operating in arrays at sites around the world. The technology to harness tidal energy is still at a relatively early stage of development; hence, de-risking of component parts plays a vital role on the road to commercialisation. Despite this, the number of tidal energy blades undergoing test programmes remains small. Two different rotor diameters have been developed for the aforementioned device such that it can be optimised for sites of varying potential. In this paper, a blade from each of the 4.0 m and 6.3 m diameter devices was tested for their responses in natural frequency, static loading and fatigue loading under test standards IEC 62600-3:2020 and DNVGL-ST-0164. Testing saw the survival of a blade in fatigue at a lifetime-equivalent load and the generation of natural frequency, strain and displacement results for both blades. Data generated from the testing as a whole will contribute to the modelling and validation of future tidal blades.

RESEARCH ON PASSIVE SOIL DEPRESSURIZATION SYSTEMS: STATE OF THE ART AND LAB TEST ON-GOING.

There is strong evidence both internationally and in Ireland that the correct installation of passive prevention systems in new buildings is the most cost-effective way of protecting the population against radon. Previous work considering membranes, granular fill material in the aggregate layer beneath the slab and sump system has been conducted in Ireland to improve the protection of buildings from radon. The implications of research on passive sumps potential to reduce radon concentrations are significant, as if it can be shown that the installation of passive sumps in Irish building is effective; this could constitute a low-cost, passive, sustainable method for minimizing radon levels in buildings. On-going experimental tests investigating the performance of different common cowls used for passive soil depressurization systems are presented, in addition to the impact of different vertical heights and horizontal lengths of pipe with a number of bends investigated.

An investigation of a passive opened top-end pipe as an alternative solution for passive soil depressurisation systems for indoor radon mitigation.

This study carried out a series of large-scale experimental tests and numerical simulations to investigate the performance of a passive opened top-end pipe as an alternative solution for passive soil depressurisation systems for indoor radon mitigation. Measurements were conducted in terms of wind velocity, extracted air velocity and negative pressure at the sump-end inside the pipe. Investigations were performed with controlled and natural wind conditions. Test results confirmed that the passive opened top-end pipe can be used as an alternative solution for indoor radon concentration mitigation at low additional construction cost. However, the extracted air velocity and negative pressure were found to fluctuate when tested under natural wind conditions. This fluctuation would reduce the effectiveness of the performance of the passive pipe. To reduce this fluctuation, a novel static ventilator has been developed and can be added on the top-end of the pipe.

Review of recent radon research in Ireland, OPTI-SDS project and its impact on the National Radon Control Strategy.

Radon is a radioactive gas originating from uranium, present in all rocks and soils in the Earth's Crust; emanating from the ground, radon can be released into the atmosphere. It is the greatest source of natural radioactivity exposure for the population and, as declared by the World Health Organization (WHO), the leading cause of lung cancer only after smoking. Although radon is a natural gas, its accumulation provoking elevated indoor radon levels is a result from building practices and thus, not natural. In Ireland, exposure to radon is estimated to be responsible for approximately 14% of all lung cancers, which is equivalent to around 300 lung cancers annually. In 2011, an interagency group was established in Ireland to develop a strategy to address indoor radon exposure, considered a significant public health concern. In 2014 a National Radon Control Strategy (NRCS) for Ireland was first published, giving a list of recommendations to be accomplished in a 4-year period Phase 1. A series of research actions to achieve the effective implementation of the strategy were conducted, including the development of a research project (OPTI-SDS) on the optimum specifications for radon mitigation by soil depressurisation systems. An overview of Phase 1 of the NRCS is presented, including outcomes from the research work carried out.

Radon mitigation by soil depressurisation case study: Radon concentration and pressure field extension monitoring in a pilot house in Spain.

A one-year monitoring study was conducted in a pilot house with extremely high radon levels to investigate the ability and efficiency of radon mitigation by soil depressurisation (SD) both active and passive. The study included monitoring of radon concentration, pressure field extension (PFE) under the slab and some atmospheric parameters for different testing phases. Periods in which the house remained closed to foster radon accumulation were alternated with phases of active and passive soil depressurisation under different conditions. The behaviour of the radon concentration in the pilot house was analysed along with the influence of atmospheric variables, significant correlations were found for the radon concentration with atmospheric pressure, outdoor temperature and wind. From the PFE analysis it was proven that the pressure drop with distance from the suction point of the SD system is proportional to the depressurisation generated. A behaviour law was found for the permeability characterisation of the house based on the active SD performance and also, the relationship between wind velocity and extraction airflow during passive SD operation by means of a rotating cowl was obtained. Radon reductions in excess of 85% were achieved for the different testing phases in all cases. Finally, from the results it was postulated that a fan power of 20 W is sufficient to ensure radon reductions over 85% for dwellings with similar aggregate layer and soil permeability.

Large-scale experimental investigations of specified granular fill materials for radon mitigation by active and passive soil depressurisations.

A series of large-scale experimental tests were performed to examine the flow behaviour of the T1 Struc and T2 Perm specified granular fill materials with active and passive depressurisations. Granular materials were compacted and tested at various compacted thicknesses. Compaction works were performed using a field compactor and compaction degrees of the materials were found to be higher than those induced by a standardised small-scale compactor. The air permeability (kah) values of the materials were obtained with active depressurisation. It was found that the overall trend of kah tended to decrease with the increase in the compacted thickness of the materials and were found to be compatible with those determined by the small-scale test apparatus. Results from passive depressurisation tests indicated that the rotating cowls performed the best, followed by a static open pipe and a pipe with a cap.

Investigation of gas flow through soils and granular fill materials for the optimisation of radon soil depressurisation systems.

The purpose of this study is to investigate gas flow through different types of granular fill materials and soil by means of a series of experimental laboratory tests, in relation to soil depressurisation systems for radon reduction under buildings and the soil surrounding the foundation. Gas permeability characterisation of materials used as granular fill material beneath the slab in buildings is a key parameter for the optimum performance of soil depressurisation systems to mitigate radon. A test apparatus was developed, adapted from previous studies, to measure the gas permeability of the samples and Finite Element Method numerical simulations were validated to simulate the flow behaviour through them. Theoretical expressions for permeability were discussed based on the analysis of experimental results and numerical simulations, finding that Darcy-Forchheimer equation provides the best match to the experimental results. Darcy's law also proved to be suitable for low gas velocities, whereas Ergun's equation resulted in a poor fit of the experimental data. Benchmark analysis of the granular fill materials under study and other European standards (Spanish, Irish and British) is also presented.

Assessing the environmental impact of the dairy processing industry in the Republic of Ireland.

This Research Communication describes the methodology used and the subsequent results obtained for an assessment of the environmental impact associated with the manufacture of dairy products in the Republic of Ireland. As the Irish dairy industry changes and grows, it is necessary to have a benchmark of the environmental performance of the sector if it is to remain sustainable in the future. In order to estimate the environmental impact, life cycle assessment has been implemented, which has been structured in accordance with the International Organisation for Standardisation guidelines. In this study, the environmental impact categories assessed are terrestrial acidification potential, cumulative energy demand, freshwater eutrophication potential, global warming potential, marine eutrophication potential and water depletion. The main Irish dairy products have been compared across these environmental impact categories in order to derive meaningful results. It is identified that packaging materials, particularly for infant formula, and energy usage, across each of the life cycle stages, should be targeted as these are the most significant contributors to the overall environmental impact.

DairyWater: striving for sustainability within the dairy processing industry in the Republic of Ireland.

This Review describes the objectives and methodology of the DairyWater project as it aims to aid the Irish dairy processing industry in achieving sustainability as it expands. With the abolition of European milk quotas in March 2015, the Republic of Ireland saw a surge in milk production. The DairyWater project was established in anticipation of this expansion of the Irish dairy sector in order to develop innovative solutions for the efficient management of water consumption, wastewater treatment and the resulting energy use within the country's dairy processing industry. Therefore, the project can be divided into three main thematic areas: dairy wastewater treatment technologies and microbial analysis, water re-use and rainwater harvesting and environmental assessment. In order to ensure the project remains as relevant as possible to the industry, a project advisory board containing key industry stakeholders has been established. To date, a number of large scale studies, using data obtained directly from the Irish dairy industry, have been performed. Additionally, pilot-scale wastewater treatment (intermittently aerated sequencing batch reactor) and tertiary treatment (flow-through pulsed ultraviolet system) technologies have been demonstrated within the project. Further details on selected aspects of the project are discussed in greater detail in the subsequent cluster of research communications.

Investigation of sub-slab pressure field extension in specified granular fill materials incorporating a sump-based soil depressurisation system for radon mitigation.

Design of bearing layers (granular fill material layers) is important for a house with a soil depressurisation (SD) system for indoor radon mitigation. These layers should not only satisfy the bearing capacity and serviceability criteria but should also provide a sufficient degree of the air permeability for the system. Previous studies have shown that a critical parameter for a SD system is the sub-slab pressure field extension in the bearing layers, but this issue has not been systematically investigated. A series of two-dimensional computational fluid dynamic simulations that investigate the behaviour of the sub-slab pressure field extension developed in a SD system is presented in this paper. The SD system considered in this paper consists of a granular fill material layer and a radon sump. The granular fill materials are 'T1 Struc' and 'T2 Perm', which are standard materials for building in the Republic of Ireland. Different conditions, which might be encountered in a practical situation, were examined. The results show that the air permeability and thickness of the granular fill materials are the two key factors which affect the sub slab pressure field extension (SPFE) significantly. Furthermore, the air permeability of native soil is found to be a fundamental factor for the SPFE so that it should be well understood when designing a SD system. Therefore, these factors should be considered sufficiently in each practical situation. Finally, a significant improvement of the pressure field extension can be achieved by ensuring air tightness of the SD system.

Investigation of Thermal Behaviour of a Hybrid Precasted Concrete Floor using Embedded Sensors.

Concrete structures expand and contract in response to temperature changes which can result in structural strain and cracking. However, there is a limited amount of robust field data on hybrid concrete floor structures. Shortage of such data impacts on our understanding of how concrete structures respond to thermal effects and ultimately the overall design of concrete structures. Thus, a comprehensive structural and environmental monitoring strategy was implemented by the authors during the construction of an educational building. Sensors were embedded in the precast and in situ components of a hybrid concrete lattice girder flat slab so that the thermal response of the floor during the manufacture, construction and operational stages could be investigated. Many aspects of the thermal behaviour of the floor during the construction phase were monitored using the embedded sensors. The early-age thermal effects during curing and the impact of the variation of ambient temperature (daily and seasonal) and solar radiation on the behaviour of concrete floor is explored in the paper. Values for restraint factors and the in situ restrained coefficient of thermal expansion of concrete are calculated using the data from the embedded sensors. Numerical modelling of the thermal behaviour of the hybrid concrete floor was undertaken and validated using the real-time field measurements. The data presented and analysed in this paper can be used to improve the understanding and modelling of the thermal behaviour of a hybrid concrete floor. This will assist with improved design of sustainable buildings as it allows the environmental performance of the floor to be optimised with respect to controlling the internal environment, thermal mass and energy efficiency.

Environmental impacts of milk powder and butter manufactured in the Republic of Ireland.

The abolition of the milk quota system that was in place in Europe was abolished in 2015, which instigated an immediate increase in milk production in many European countries. This increase will aid in addressing the world's ever growing demand for food, but will incur increased stresses on the environmental impact and sustainability of the dairy industry. In this study, an environmental life cycle assessment was performed in order to estimate the environmental impacts associated with the manufacture of milk powder and butter in the Republic of Ireland. A farm gate to processing factory gate analysis, which includes raw milk transportation, processing into each product and packaging, is assessed in this study. Operational data was obtained from 5 dairy processing factories that produce milk powder (4 of which also produce butter). Results for each environmental impact category are presented per kilogram of product. Energy consumption (raw milk transportation and on-site electrical and thermal energy usage) contributes, on average, 89% and 78% of the total global warming potential, for milk powder and butter respectively, for the life cycle stages assessed. Similarly, energy consumption contributes, on average, 86% and 96% of the total terrestrial acidification potential for milk powder and butter respectively, for these life cycle stages. Emissions associated with wastewater treatment contribute approximately 10% and 40% to the total freshwater eutrophication potential and marine eutrophication potential, respectively, for both milk powder and butter production. In addition, packaging materials also has a significant contribution to these environmental impact categories for butter production. Results were also presented for three milk powder products being manufactured by the factories surveyed: skim milk powder, whole milk powder and full fat milk powder. The analysis presented in this paper helps to identify opportunities to reduce the environmental impacts associated with post-farm processing of milk powder and butter.