Selecting extreme weather file to assess overheating in residential building

Climate change is great challenge for current and newly built buildings. Nowadays, TMY weather file can be easily generated following the IPCC scenarios. Nevertheless, since these data are extrapolated with stochastic model from monthly mean values, they do not show a real pattern and do not include extreme events like heatwaves. In order to get more representative data, we propose in this work a methodology to select real measured files from a large database in light of heatwaves and climate change. This methodology is applied to the city of Lyon, for which 26 years of weather data are available. Three measured weather files projected for the time periods 2020, 2050 and 2080 are selected. These files are used in building thermal simulation of residential building with low or high thermal inertia. Summer overheating is analysed through two different comfort indicators: adaptative comfort and Givoni chart. Results indicates that summer overheating risk is obviously increased with future weather files. When compared to usual TMY files, this risk is also enhanced by using weather file including extreme events like heatwaves. Last, we note that discomfort is mainly encountered during this extreme events.

Thermal behavior of light earth used for building insulation: Insight on PCM introduction impact

To reduce building significant contribution to greenhouse gas emissions, architects and engineers are seeking eco-friendly construction solutions. Among investigated options, building’s thermal insulation and heat storage can be cited. In this regard, earth-based materials are attracting particular interest. These last years, there is a renewed interest in these eco-friendly building materials and techniques. This is due to many advantages that they present: excellent humidity regulation ability and high thermal inertia. Present study aims to improve light earth thermal properties. Specifically, this research work focuses on the development of an insulating and heat storing material. To achieve this, phase change materials (PCM) are incorporated in soil-natural fiber mixtures. In fact, different light earth samples are first prepared. Then, thermally characterized to highlight the impact of PCM on the light earth thermal insulating, heat storing properties and thermal response to changing boundary conditions. The incorporation of PCM showed an interesting improvement of the light earth thermal properties namely on thermal conductivity, specific heat capacity, and thermal comfort time.

Development of a Wireless System to Control a Trombe Wall for Poultry Brooding

The Internet of Things asserts that several applications, such as smart cities or intelligent agriculture, can be based on various embedded systems programmed to do different tasks, by transferring data over a network from sensors to a server, where the information is stored and treated, supporting the decision-making process. In this context, LoRaWAN is an accurate network topology based on a wireless technology called LoRa that is capable of transmitting small data rates at a long range, using low-powered devices, making it ideal for the acquisition of climate variables, such as temperature and relative humidity. Applying this architecture to agriculture buildings can be very useful to guarantee indoor thermal comfort conditions. In this study, this technology is applied to a passive solar system composed by a high thermal inertia wall, defined as Trombe wall, with air vents provided in the massive wall to improve heat transfer by air convection, and an external shading device to avoid overheating during summer and heat losses during winter. It is intended to analyze the possibility to control the interiortemperature of a poultry brooding house given that, in the early stages of life, chickens need accurate climate conditions in order to enhance their growth and reduce their mortality rate. In brief, temperature values acquired by different sensors placed on the Trombe wall travel through a LoRaWAN wireless network and are received by an application that controls the actuators, in this case, the opening and closing of the Trombe wall air vents, while the external shading device is controlled locally.

New Reactor Safety Measures for the European Sodium Fast Reactor - Part I: Conceptual Design

Following up the previous CP-ESFR project, the ESFR-SMART project considers the safety objectives envisaged for Generation-IV reactors, taking into account the lessons learned from the Fukushima accident, in order to increase the safety level of the European Sodium Fast Reactor (ESFR). In accordance with these objectives, guidelines have been defined to drive the ESFR-SMART developments, mainly simplifying the design and using all the positive features of Sodium Fast Reactors (SFR), such as low coolant pressure, efficiency of natural convection, possibility of decay heat removal (DHR) by atmospheric air, high thermal inertia and long grace period before a human intervention is needed. In this paper, a set of new ambitious safety measures is introduced for further evaluation within the project. The proposed set aims at consistency with the main lines of safety evolutions since the Fukushima accident, but it does not yet constitute the final comprehensive safety analysis. The paper gives a first review of the new propositions to enhance the ESFR safety, leading to a simplified reactor, forgiving and including a lot of passivity. This first version is supported by the various project tasks in order to assess the relevance of the whole design in comparison to the final safety objectives.

Modeling the Evolution of Construction Solutions in Residential Buildings’ Thermal Comfort

The evolution of the construction sector over the years has been marked by the replacement of high thermal inertia mass constructions by increasingly lighter solutions that are subject to greater thermal fluctuations and, consequently, thermal discomfort. To minimize these effects, energy demanding space conditioning technologies are implemented, contributing significantly to the sector’s share of global energy consumption. Enhanced constructive solutions involving phase-change materials have been developed to respond to the constructive thermal inertia loss, influencing buildings’ thermal and energy performance. This work aims to model the evolution of the construction over the last decades to understand to what extent constructive characteristics influence the occupants’ thermal comfort. For this purpose, typical and enhanced solutions representing distinct constructive periods were simulated using the EnergyPlus® software through its graphical interface DesignBuilder® and the thermal comfort of the different solutions was evaluated using the adaptive model for thermal comfort EN16798-1. The main results reveal that more restraining regulatory requirements are indeed mitigating thermal discomfort situations. However, overheating phenomena can rise, creating worrying consequences in the short-medium term. Thus, countries with mild climates such as Portugal, must pay special attention to these effects, which may be aggravated by climate change.

TEMPERATURE CONTROL FOR 3D ADDITIVE PROCESSES BASED ON THE VARIABLE ELECTRICAL PARAMETERS OF THE HEATED NOZZLE

Статья посвящена трёхмерной печати по технологии FFF/FDM. Большинство существующих на рынке FDM 3D-принтеров используют косвенный резистивный метод нагрева сопла и стандартные термоэлектрические методы контроля температуры, что обусловливает высокую тепловую инерционность системы нагрева и невозможность обеспечения достаточной скорости и точности контроля температуры. Невозможность управления температурой сопла в процессе печати приводит к непостоянному качеству межслоевого спекания и неоднородности внутреннего объёма напечатанных изделий. Для минимизации или устранения перечисленных недостатков используется индукционная система нагрева сопла минимальной тепловой массы. При этом для контроля температуры сопла предлагается резонансный (вихретоковый) метод. Для реализации данного метода контроля температуры требуется определить зависимость электрических параметров материала сопла от температуры. Для определения данной зависимости был разработан лабораторный стенд, состоящий из источника питания, генератора колебаний высокой частоты, катушки-индуктора, измерительной катушки, блока регистрации и обработки измерительного сигнала. Представлены методика получения измерительного сигнала и методика обработки измеренного сигнала для получения зависимости величины данного сигнала от температуры. Предложены стратегии управления температурой сопла на основе полученных зависимостей. Представлены результаты экспериментов, подтверждающие заявленные характеристики системы The article is devoted to FDM 3D manufacturing. Most of the FDM 3D printers on the market use an indirect resistive nozzle heating method and standard thermoelectric temperature control methods, which leads to a high thermal inertia of the heating system and the inability to provide sufficient speed and accuracy of temperature control. The inability to control the temperature of the nozzle during the printing process leads to inconsistent of layer-to-layer adhesion quality, and on the larger scale - to heterogeneity of material inside the whole printed object. To mitigate and/or resolve these problems, we proposed an induction heating system of the nozzle with a minimum thermal mass. At the same time, we proposed a resonant (eddy current) method to control the temperature of the nozzle. To implement this method of temperature control, we required to determine the dependence of the electrical parameters of the nozzle material on temperature. To determine this dependence, we created a testbed system, consisting of the ultra-low weight induction heated nozzle, a power source, a high-frequency oscillator, an inductor coil, a measuring coil, a unit for recording and processing a measuring signal. We present the means for detection and amplification of the measuring signal. We show the steps for processing of the acquired signal to obtain final temperature values. We propose approaches for controlling the nozzle temperature based on the obtained dependences. We provide the experimental data for all the stages of conducted research

On the Energy Performance of an Innovative Green Roof in the Mediterranean Climate

Green roofs have a thermal insulating effect known since ancient times. In the building sector, green roofs represent a sustainable passive solution to obtain energy savings, both during winter and summer. Moreover, they are a natural barrier against noise pollution, reducing sound reflections, and they contribute to clean air and biodiversity in urban areas. In this research, a roof-lawn system was studied through a long experimental campaign. Heat-flow meters, air and surface temperature sensors were used in two buildings characterized by different surrounding conditions, geometries and orientations. In both case studies, the thermal behaviors of the roof-lawn system were compared with the conventional roofs. In addition, a dynamic simulation model was created in order to quantify the effect of this green system on the heating and cooling energy demands. The roof-lawn showed a high thermal inertia, with no overheating during summer, and a high insulating capacity, involving energy savings during winter, and consequently better indoor thermal conditions.

Asteroid (101955) Bennu’s weak boulders and thermally anomalous equator

Thermal inertia and surface roughness are proxies for the physical characteristics of planetary surfaces. Global maps of these two properties distinguish the boulder population on near-Earth asteroid (NEA) (101955) Bennu into two types that differ in strength, and both have lower thermal inertia than expected for boulders and meteorites. Neither has strongly temperature-dependent thermal properties. The weaker boulder type probably would not survive atmospheric entry and thus may not be represented in the meteorite collection. The maps also show a high–thermal inertia band at Bennu’s equator, which might be explained by processes such as compaction or strength sorting during mass movement, but these explanations are not wholly consistent with other data. Our findings imply that other C-complex NEAs likely have boulders similar to those on Bennu rather than finer-particulate regoliths. A tentative correlation between albedo and thermal inertia of C-complex NEAs may be due to relative abundances of boulder types.