When social practices produce space and create passive cooling systems in hot arid region

Practice social of people is the key to produce space and give a possibility to maintain thermal comfort and energy efficiency. The main objective of this research is to adapt the traditional strategies in the architecture actual, to achieved a thermal comfort and improve on reducing cooling load through the using of vernacular gait. Today, it is necessary to practice these systems in the current or conventional architecture of household. The study is especially for arid cities namely the region of Saoura, in the hot and dry climatic zone in Algeria, considered for this study. Two main factors is considered such as design and urban where taken into account in order to select the appropriate and specific passive cooling strategy. The results show that the passive cooling strategy of courtyard would be appropriate for arid regions, however a high thermal mass would be suitable for construction. In conclusion, this work made it possible to choose a suitable passive cooling strategy for all types of construction in hot and dry climates. Finally, this paper puts forward a set of recommendations to improve the passive design of future buildings in hot and arid climates.

Development and Application of a Thermal Comfort Model in Buildings

Buildings are one of the systems that more energy consumed in the European Union. The study of the thermal envelope is interesting in order to reduce the energy losses. For that, a mathematical model able to predict the system response to external temperature variations is developed. With the mathematical model, different thermal envelope elements of a building based on the lag and the cushioning of the resultant wave can be characterized. In addition, it is important to analyse where the insulation is placed, because when the insulation is outside and the thermal mass is inside, the system produces a response with smooth temperature variations than when the insulation is inside. Therefore, placing the outside insulation generates more steady indoor temperatures, increasing the thermal comfort inside the building. To complete the mathematical model that allows predicting the temperature inside a building taking into account the solar inputs and the thermal inertia of the building. This study will help to establish the optimum design parameters in order to build sustainable and comfortable buildings. Furthermore, it will take one step forward in the construction of nearly Zero-Energy Buildings.

Computational Modeling of the Thermal Behavior of a Greenhouse

The need for production of all kinds of crops in high quantities and over the entire year makes the agricultural sector one of the major energy consumers. The optimization of this consumption is essential to guarantee its sustainability. The implementation of greenhouses is a strategy that allows assurance of production needs and possesses large optimization potential for the process. This article studies different greenhouse structures by computational simulation using EnergyPlus and DesignBuilder. First, a comparison was performed between the computational results and the measured values from a greenhouse prototype at different operating conditions. Overall, the comparison shows that the computational tool can provide a reasonable prediction of the greenhouse thermal behavior, depending on the differences between the weather data modeled and observed. An outdoor air temperature difference of 16 °C can cause a difference of about 10 °C between the air temperature predicted and measured inside the greenhouse. Subsequently, a selected set of case studies was developed in order to quantify their influence on the thermal performance of the greenhouse, namely: the greenhouse configuration and orientation; the variation of indoor air renewal; changes to the characteristics of the roof; the effect of the thermal mass of the walls; and location of the greenhouse. The results show that a correct greenhouse orientation, together with a polyethylene double cover with a 13 mm air layer, a granite wall of 40 cm thickness on the north wall, and variable airflow rate, may lead to a reduction of the greenhouse energy consumption by 57%, if the greenhouse is located in Lisbon, or by 43%, if it is located in Ostersund, during the hottest months of the heating season.

Evaluation of the Thermal Comfort and Energy Demand in a Building with Rammed Earth Walls in Spain: Influence of the Use of In Situ Measured Thermal Conductivity and Estimated Values

This paper describes the influence of thermal parameters—conductivity, transmittance, and thermal mass—in the estimation of comfort and energy demand of a building with rammed earth walls, and consequently, the compliance with standards. It is known that nominal design data does not match in situ measured values, especially in traditionally constructed buildings. We have therefore monitored a room in a building with rammed earth walls, designed a computerised model, and compared four different alternatives where we have changed the value for the thermal conductivity (in situ vs. estimated) and the consideration of thermal mass. When we then analyse the compliance with the Spanish energy saving code, using measured values would result in lower differences with the standards’ limits and even comply with the global thermal transmittance (K-value) requirement. This would mean a more realistic approach to the restoration of traditional buildings leading to the use of thinner and more suitable insulation and retrofitting systems, encouraging the use of rammed earth in new buildings, and therefore reducing the carbon footprint due to materials used in construction. Results show that the building model that uses in situ values and considers thermal mass (S1) is closer to reality when assessing thermal comfort. Finally, using nominal data would result in requiring 43% more energy in the selected winter period and 102% more energy in the selected summer period to keep the same comfort conditions as in the alternative where measured values are used.

Missing scalars at the cosmological collider

Light scalar fields typically develop spatially varying backgrounds during inflation. Very often they do not directly affect the density perturbations, but interact with other fields that do leave nontrivial signals in primordial perturbations. In this sense they become “missing scalars” at the cosmological collider. We study potentially observable signals of these missing scalars, focusing on a special example where a missing scalar distorts the usual oscillatory features in the squeezed bispectrum. The distortion is also a useful signal distinguishing the de Sitter background induced thermal mass from a constant intrinsic mass.

Production of Fresh Water by a Solar Still: An Experimental Case Study in Australia

There is a scarcity of fresh water in many rural communities where solar stills can be used to produce drinking water at a minimal cost. These stills use solar energy, which is a sustainable form of energy, and hence this can contribute towards achievement of United Nations (UN) Sustainable Development Goals (SDG). This study aims to develop empirical models of a solar stills based on experimental data obtained at Werrington South, New South Wales, Australia. Two solar stills were used in the experiment, a conventional design (Con-Still) and a con-still modified with adding extra thermal mass inside the still (mod-still). Regression analysis was adopted to develop prediction equations using Pi (productivity in L/m2/day) as the response variable and ambient temperature (Ta), sky temperature (Ts19), global radiation (Gh), and wind velocity (W) as the predictor variables. The mean and median productivity values of the mod-still were found to be 17%, and 22% higher than that those for the con-still. The proposed mod-still can be further improved and used in rural areas to produce fresh water from sea water and other forms of contaminated water.

A Rapid Method for Low Temperature Microencapsulation of Phase Change Materials (PCMs) Using a Coiled Tube Ultraviolet Reactor

Microencapsulation of phase change materials (PCMs) remain a suitable option within building materials, as they contribute to the thermal mass and provide an energy buffer, an added benefit. This paper presents a novel method for the rapid fabrication of microencapsulated phase change materials (PCMs) at ambient conditions in a perfluoroalkoxy (PFA) coiled tube ultraviolet (UV) reactor. The objective of this study was to optimize key parameters such as the product yield and quality of the as-prepared microcapsules. Rubitherm® RT-21™ PCM was microencapsulated within shells of poly-methyl-methacrylate (PMMA) through a suspension emulsion polymerization approach, where the crosslinking of polymers was driven by UV radiations with an appropriate photoinitiator. The characteristics of the resulting PCM microcapsules were found to be affected by the volumetric flow rate of the emulsion inside the coiled tube reactor. Higher volumetric flow rates led to higher PCM contents and higher microencapsulation efficiency, resulting in an average particle size of 6.5 µm. Furthermore, the effect of curing time on the PCM microcapsule properties was investigated. The optimum encapsulation yield, conversion, efficiency and PCM content were observed after 10 min of polymerization time. The thermal analysis indicated that the developed process had an efficiency of 85.8%, and the capsules were characterized with excellent thermal properties. Compared to the conventional thermal microencapsulation processes, the use of a coiled tube UV reactor with an appropriate photoinitiator enables the encapsulation of heat-sensitive PCMs at ambient conditions, and reduces the microencapsulation time dramatically. As a result, this novel microencapsulation approach can lead to a wider scope of PCM encapsulation and enable rapid, continuous and potentially large-scale industrial production of PCM microcapsules with low energy consumption.