Big Data to support sustainable urban energy planning: the EvoEnergy project

Energy sustainability is a complex problem that needs to be tackled holistically by equally addressing other aspects such as socioeconomic to meet the strict CO2 emission targets. This paper builds upon our previous work on the effect of household transition on residential energy consumption where we developed a 3D urban energy prediction system (EvoEnergy) using the old UK panel data survey namely the British household panel data survey (BHPS). In particular, the aim of the present study is to examine the validity and reliability of EvoEnergy under the new UK household longitudinal study (UKHLS) launched in 2009. To achieve this aim, the household transition and energy prediction modules of EvoEnergy have been tested under both datasets using various statistical techniques such as Chow test. The analysis of the results advised that EvoEnergy remains a reliable prediction system and had a good prediction accuracy (MAPE ≃ 5%) when compared to actual EPC data. From this premise, we recommend researchers, who are working on data-driven energy consumption forecasting to consider merging the BHPS and UKHLS datasets. This will, in turn, enable them to capture the bigger picture of different energy phenomena such as fuel poverty; consequently, anticipate problems with policy prior to their occurrence. Finally, the paper concludes by discussing two scenarios of EvoEnergy development in relation to energy policy and decision-making

Scaling of AlN/GaN HEMT for millimeter-wave power applications

International audienceIn this paper, we report on AlN/GaN HEMTs for high frequency applications. Various gate lengths have been studied as a function of the gate-drain distance in order to analyze the impact on the DC, RF and power performances. Electrical characteristics of this structure for 110 nm gate length show a maximum drain current of 1.2 A/mm, an extrinsic transconductance Gm of 400 mS/mm and a FT/Fmax of 63/300 GHz at a drain bias voltage VDS = 20V. An excellent electron confinement with a low leakage current below 10 µA/mm is achieved. Furthermore, a breakdown voltage of 55 V for GD0.5 and up to 140 V for GD2.5 are observed when using a 110 nm short gate length. Large signal characteristics at 40 GHz reveal a state-of-the-art combination of power added efficiency (PAE) (50%) with an output power density (Pout) of 3.6 W/mm at VDS = 20 V in continuous wave mode (CW) and PAE of 50% associated with a Pout of 8.3 W/mm at 40V in pulsed mode. It can be noticed that the 110 nm gate length GD0.5 showed no degradation after semi-on robustness tests and large signal measurements up-to VDS = 20V

GaN-based transistors using buffer-free heterostructures for next generation RF devices

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Demonstration of GaN-on-silicon material system operating up to 3 kilovolts with reduced trapping effects

International audienceWe report on the first demonstration of low trapping effects up to 3000 V within GaN-on-silicon epitaxial layers using a local substrate removal (LSR) followed by a thick backside ultra-wide-bandgap AlN deposition. The fabricated AlGaN/GaN devices deliver low specific on-resistance below 10 mΩcm 2 together with unprecedented 3-terminal blocking voltage while substrate ramp measurements show reduced hysteresis up to 3000 V. These results pave the way for beyond 1200 V applications using large wafer diameter GaN-on-Si high electron mobility transistors

AlGaN/GaN High Electron Mobility Transistors with Ultra -Wide Bandgap AlN buffer

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Accuracy evaluation of the semi-automatic 3D modeling for historical building information models

It is stated that 3D recording and modelling of heritage buildings entails accurate building models (as-built). However, this paper presents an analysis of the 3D modelling accuracy for the creation of historical building information models (HBIM), considering the complexity and the deformations of historical buildings, using point cloud data and BIM tools. The 3D modelling processes analysed are based on a three-stage semi-automatic approach leading to the generation of HBIM, including manual and automatic processes. The three stages consist of: (a) optical and terrestrial laser scanning; (b) meshing processes; and finally (c) 3D solid modelling to be assembled into HBIM. Next, this approach analysed the mesh deformations generated automatically in comparison to the initial point cloud data. The deformations and the accuracy evaluation have been undertaken using different commercial software. Finally, our modelling approach shows that it can improve the accuracy of the 3D models achieved using existing BIM technologies

Managing construction site communication using the responsibility assignment matrix (RAM) system

The construction industry in the UK wastes £1 billion per year due to construction defects that are mainly caused by a communication failure between organisations operating on the construction site. Meanwhile, the introduction of the BIM strategy has become a mandatory requirement by the government in order to reduce costs by 33% and speed up project delivery by 50% without sacrificing quality. Since then, the industry has seen a global reaction to the BIM Level 2 programme and a significant cost-saving in the UK of £1.2 billion in 2014/15, rising from £840 million in 2013/14. However, communication remains a major issue to achieve the BIM Level 3 as it requires all organisations involved to use a single platform to facilitate communication. This paper, therefore, fits within the BIM implementation programme by addressing the communication issues and construction defects on-site toward formulating a communication framework for the construction industry in the UK. This will help optimise communication and manage construction defects efficiently. The study takes advantage of the Responsibility Assignment Matrix (RAM), the widely known management system and uses it to assign communication tools for each organisation in relation to the construction stages throughout two phases of data collection. Phase 1 involves two qualitative data collection methods of an in-depth review of the relevant literature (document analysis) and construction site observation. To facilitate site observation and data collection, the researcher collaborated with GF Tomlinson group, a Derby-based construction company, as the case study. Phase 2 involves an online survey, targeting a total number of 328 participants, including professionals and academics. Results of phase 1 are presented as the Communication Tools Assignment 1 (CTA1) and phase 2 results inform the Communication Tools Assignment 2 (CTA2). The study contribution is to develop a framework that recommends the appropriate communication tools for organisations at different construction stages, and which shows the possible types and causes of construction defects. Moreover, the study found three types of construction defects by applying 3D laser scanning for framework mentoring

From discovering to delivering: a critical reflection on eco-feedback, application design, and participatory research in the United Kingdom

The area of Eco-Feedback has received significant attention in recent years. Whilst there have been increasing calls to move ‘beyond feedback’ and consider the wider social, organisational and cultural context that feedback sits within, the involvement of community members in the design process of eco-feedback applications, known as co-design, has been limited. This study addresses that research gap through working collaboratively with community members to develop an accessible eco-feedback interface. First, we conducted an online survey questionnaire with 151 respondents with distinct socio-economic characteristics and environmental knowledge to get insights into their preferences about different aspects of the eco-feedback interface. Secondly, based on the survey findings, 20 community members living in Nottingham, UK, worked collaboratively to develop interface design proposals. Finally, the design of the eco-feedback interface was finalised based on the community interface prototypes and suggestions. The developed interface contains multiple information panels with options for expanding to gain deeper levels of information and a community space allowing for community interactions and sharing of information and actions. This research sheds new light on the challenges of utilising co-design principles to build eco-feedback interfaces. Specifically, we highlight the potential for interactions between community members during the design stages to allow for the generation of innovative ideas (e.g. Integration of third-party applications) moving the interface beyond feedback leading to greater adoption and energy savings

Visualisation in energy eco-feedback systems: a systematic review of good practice

While adopting eco-feedback systems can lead to significant energy savings, in the region of 5–20%, research has shown that the inappropriate use of visualisation patterns and techniques decreases their effectiveness. However, existing reviews on energy feedback visualisation provide little guidance on when to use them and how to enhance their effectiveness in various scenarios. The uncertainty and lack of clarity surrounding eco-feedback visualisation techniques and their impact on end-userengagement present challenges to the design of ecofeedback systems. This paper presents the first systematic review of a wide range of energy eco-feedback visualisation techniques, including, for the first time, Augmented-Reality (AR) and thermal imaging visualisation. We analysed 82 relevant studies published between 2000 and 2021 using the PRISMA protocol for systematic reviews. The visualisation techniques have been reported under five distinct categories, which we have identified: (a) statistical visualisation, (b) architectural and geospatial visualisation, (c) game-based visualisation, (d) artistic visualisation, (e) emerging visualisation. Furthermore, they have been analysed based on the following criteria: type of visualised information, the purpose of use, end-user perception, scholar suggestions, and potential impact. The findings show that statistical visualisation techniques are essential in any energy eco-feedback system. Furthermore, they suggested combining different visualisation techniques to accommodate different user profiles, but such combinations must be carefully planned based on usage scenarios. Following this analysis, a series of considerations and good practice guidelines are presented for each of the reviewed techniques to assist practitioners in this area (e.g., designers and researchers) while providing recommendations for future work

Buffer breakdown in GaN-on-Si HEMTs: A comprehensive study based on a sequential growth experiment

Abstract The aim of this work is to investigate the breakdown mechanisms of the layers constituting the vertical buffer of GaN-on-Si HEMTs; in addition, for the first time we demonstrate that the breakdown field of the AlN nucleation layer grown on a silicon substrate is equal to 3.2 MV/cm and evaluate its temperature dependence. To this aim, three samples, obtained by stopping the epitaxial growth of a GaN on Silicon stack at different steps, are studied and compared: Si/AlN, Si/AlN/AlGaN, full vertical stack up to the Carbon doped buffer layer. The current-voltage (IV) characterizations performed at both room temperature and high temperature show that: (i) the defectiveness of the AlN nucleation layer is the root cause of the leakage through an AlN/Silicon junction, and causes the vertical I-V characteristics to have a high device-to-device variability; (ii) the first AlGaN layer grown over the AlN, beside improving the breakdown voltage of the whole structure, causes the leakage current to be more stable and uniform across the sample area; (iii) a thick strain-relief stack and a carbon-doped GaN buffer enhance the breakdown voltage up to more than 750 V at 170 °C, and guarantee a remarkably low device-to-device variability. Furthermore, a set of constant voltage stress on the Si/AlN sample demonstrate that the aluminum nitride layer shows a time dependent breakdown, with Weibull-distributed failures and a shape factor greater than 1, in line with the percolation model