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© 2020 Elsevier Ltd Free cooling of buildings uses the nocturnal outdoor air as a heat sink via a ventilation process. This could be performed by storing the night coolness for use during the daytime as appropriate. Due to the latent heat capacity, phase change material (PCM) could play anessential role in the effective operation of the free cooling systems by shifting the daytime peak load to the night. However, there is a scarceness on the technology application in hot climates. This paper presents results of a parametric investigation into the application of PCMs as thermal energy storage (TES) to provide sustainable cooling to buildings in hot arid climate by making use of the night-time free cooling. The proposed TES medium comprises an arrangement of metallic modules filled with RT28HC PCM. Numerous geometrical configurations and operational parameters have been assessed. A transient CFD simulation has been employed using ANSYS Fluent software. Validation of the numerical results with experimental data has shown a good agreement. The results have demonstrated that the temperature difference between the PCM and the air, at appropriate air flow rate would have a significant impact on the performance of the system. A free cooling system based on the proposed arrangement has the potential to meet around 42% of a typical building cooling load and has the ability to save up to 67% of building cooling energy load in summer season compared to conventional air-conditioning systems in hot arid climates.

Due to the single-phase loads and their stochastic behavior, the current in the distribution feeders is not balanced. In addition, the single-phase loads are located in different positions along the LV feeders. So the amount of the unbalanced load and its location affect the feeder losses. An unbalanced load causes the feeder losses and the voltage drop. Because of time-varying behavior of the single-phase loads, phase balancing is a dynamic and combinatorial problem. In this research, a heuristic and dynamic solution for the phase balancing of the LV feeders is proposed. In this method, it is supposed that the loads’ tie could be connected to all phases through a three-phase switch. The aim of the proposed method is to make the feeder conditions as balanced as possible. The amount and the location of single-phase loads are considered in the proposed phase balancing method. Since the proposed method needs no communication interface or no remote controller, it is inexpensive, simple, practical, and robust. Applying this method provides a distributed and dynamic phase balancing control. In addition, the feasibility of reducing the used switches is investigated. The ability of the proposed method in the phase balancing of the LV feeders is approved by carrying out some simulations.

AbstractAn arc‐furnace model consisting of non‐linear, time‐varying resistance, realized by the Alternative Transients Program (ATP), is presented in this paper. It is shown that the model is appropriate for flicker investigation in electrical networks supplying arc furnaces, constituting a valid alternative to the linear arc modelling realized by amplitude modulation of voltage generators. Block diagram of the procedure for ATP modelling of the nonlinear, time‐varying arc resistance, dynamic voltage‐current characteristic of the furnace electric arc, voltage and current arc waveforms and characteristic curves of an arc furnace, obtained by ATP simulation, are presented, referring to circuit parameters taken from an actual plant and to a sinusoidal law for arc‐length time variation. Aflickermeter ATP simulation is realized to derive equivalent voltage‐variation values in agreement with the actual flicker measurements.

Abstract The central role of occupants for achieving energy savings in residential buildings is increasingly recognised. Simulation programmes able to take into account occupant behaviour are considered to be powerful tools for bridging the gap between the predicted and the actual energy consumption for new buildings. Nevertheless, the majority of residential buildings that will constitute the housing stock in 2050 have already been built today, therefore occupant behaviour and building simulation tools need to be fully exploited for supporting the renovation of existing housing stock. The aim of this paper is to explore the role of occupant behaviour modelling in supporting decision-makers dealing with the design of renovation strategies for residential buildings. An Italian multi-family public housing building is assumed as case study to estimate the influence of three dimensions linked with occupant behaviour – management of the thermostat, management of the heating system, variation of building characteristics – on energy heating consumption. The results show that, while the occupant behaviour influences the heating loads up to 1/3 in case of high level of building retrofit, the less the building is renovated, the higher is the behavioural impact in absolute terms of energy reduction. Therefore, in order to be effective, renovation strategies are required to design appropriate informative instruments at an early stage to support behaviour changes towards responsible energy consumption.

The main objective of this paper is to illustrate the current state of the art of the newborn smart gas grid concept. We provide a detailed discussion of the envisaged features of the smart gas grid, giving attention to both the related academic literature and to the ongoing world-wide projects. In doing so, we also discuss the potentialities of rethinking the smart grid paradigm from the perspective of a whole energy system, that both encompasses the electrical and the gas grid, and identify some critical key aspects that must be handled while developing the new smart energy paradigm.

Abstract A CFD modelling study has been undertaken to examine the co-firing of pulverised coal and biomass with particular regard to the burnout of the larger diameter biomass particles. Computations were based on a research combustion facility that replicates an industrial coal-fired power station. Three percent, by mass, of pinewood was blended with a bituminous UK coal, and the effects of the wood particle size and shape on the burnout of the combined wood and coal char were investigated. The effect of varying the devolatilisation and char combustion rate constants for the biomass component in the blend was also investigated. It was concluded that the combustion of small (200 μm) wood particles was rapid but the rate of combustion of larger particles was dependent on their composition, size, and shape.

The Severn Estuary has the world's second largest tide range and a barrage across the estuary, located just seawards of Cardiff in Wales and Weston in the South West England, has been proposed for over half a century, with the objective of extracting large amounts of tidal energy. A Severn Barrage, as previously proposed by the Severn Tidal Power Group (STPG), would be the largest renewable energy project for tidal power generation in the world, if built as proposed, and would generate approximately 5% of the UK's electricity needs. However, concerns have been raised over the environmental impacts of such a barrage, including potential increase in flood risk, loss of intertidal habitats etc. In addressing the challenges of maximizing the energy output and minimizing the environmental impacts of such a barrage, this research study has focused on using a Continental Shelf model, based on the modified Environmental Fluid Dynamics Code (EFDC) with a barrage operation module (EFDC_B), to investigate both the far and near field hydrodynamic impacts of a barrage for different operating scenarios. Three scenarios have been considered to simulate the Severn Barrage, operating via two-way generation and using different combinations of turbines and sluices. The first scenario consisted of 216 turbines and 166 sluices installed along the barrage; the second consisted of 382 turbines with no sluices; and the third consisted of 764 turbines and no sluices. The specification of the sluice gates and turbines are the same for all scenarios. The model results indicate that the third scenario has the best mitigating effects for the far-field and near-field flood risks caused by a barrage and produces the most similar results of minimum water depth and maximum velocity distributions to those obtained from simulating the natural conditions of the estuary, i.e. the current conditions. The results also show that the flow patterns around the barrage are closest to those for the existing natural conditions with minimal slight changes in the estuary. Thus, the results clearly indicate that the environmental impacts of a Severn Barrage can be minimized if the barrage is operated for two-way generation and under the third scenario. Although it appears that the energy output for the third scenario is less than that obtained for the other two scenarios, if very low head (VLH) turbines are used, then the third scenario could generate more energy as more turbines could be cited along the barrage structure. Therefore, the study shows that a Severn Barrage, operating in two-way generation and with 764 turbines (ideally VLH turbines), would be the best option to meet the needs of maximizing the energy output, but having a minimal impact on environmental changes in the estuary and far-field.

Biomass plays an important role in the world primary energy supplies, currently providing ∼14% of the world's primary energy needs and being the fourth largest contributor following coal, oil and natural gas. Over the past decade, domestic biomass heating has received more governmental and public supports than ever before in many developed countries, such as the UK. Although biomass combustion releases some combustion pollutants, biomass is renewable and produces little net CO 2 emissions to the atmosphere. Owing to the low sulphur and low nitrogen contents of many biomass materials, substituting biomass for fossil fuels, particularly coal, can reduce SO x and NO x emissions. This study investigated flue gas emissions, particularly carbon monoxide and nitrogen oxides, of a domestic biomass boiler under various operating conditions. The biomass boiler used in this study satisfies the current EU regulation (EN 303-05) on emissions of domestic biomass boilers. Emissions of the boiler had been measured not only under normal combustion conditions, but also under 'idle' combustion conditions when the boiler was not in but was ready for full operation. The experimental results are analysed and presented in this paper. Copyright The Author 2010. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org, Oxford University Press.