Search

Lead-free Sr0.6Ca0.4TiO3 ceramic was prepared by solid-state reaction route. X-ray diffraction technique showed the phase purity and identified the orthorhombic perovskite structure. Scanning Electronic Microscopy observation evidenced homogeneous morphology and dense microstructure. Electrical conduction and dielectric relaxation mechanisms at high temperature have been studied by complex impedance measurement techniques over a wide range of frequencies and temperatures, from 100 Hz to 1 MHz and from 573 K to 783 K. Fitting of impedance measurements allowed us to study grains and grain boundaries electrical characteristics and their contribution to the conduction and dielectric relaxation processes in the ceramic. Electrical conduction in grains is due to oxygen vacancy jumps for temperatures below 733 K and to polarons above 763 K. Electrical DC conductivity in grains and grain boundaries is mainly due to oxygen vacancies. Impedance measurements and relaxation time distribution function calculations show non-Debye-type relaxation effects for both grains and grain boundaries. [ABSTRACT FROM AUTHOR]

Public management can play an important role in improving the energy optimization of Moroccan universities. By adopting efficient management practices and implementing appropriate energy policies, universities can reduce their energy consumption, decrease their carbon footprint and realize financial savings., while taking into consideration the examples or the cases of the universities having shared their experiences. Among the elements that we have noticed present in the majority of university establishments is the presence of a long-term energy strategy for universities, setting clear objectives in terms of reducing energy consumption and greenhouse gas emissions. This strategy should include specific measures such as installing energy efficient lighting systems, using renewable energy sources, improving the efficiency of heating, ventilation and air conditioning systems. In this article we will try to emphasize the key elements of the success of public management with reference to energy optimization by taking into consideration the case of Moroccan universities.

Researchers in the building industry are becoming increasingly interested in phase change materials (PCM). As these PCMs might provide passive temperature adjustment, this will aid in lowering the energy consumption of Heating, Ventilation, and Air-Conditioning (HVAC) devices. To prevent leakage during phase change, an enclosure is needed when installing PCMs in buildings. The need to assess the passive thermal regulation of the PCMs at different melting temperature is necessary, so that we can get a sense of how much energy will be saved for this passive thermal regulation method. Hence, this paper will evaluate and identify the optimum phase change transition temperatures during the whole year for wall composition with tunable PCM in a semi-arid climate. Thus, the main objective of this study is to assess the indoor air temperature fluctuation reduction and the PCM activation while suggesting an appropriate phase change transition temperature that can be beneficial in the whole year and very practical. The results reveal a good passive temperature regulation during the summer period.

The variable refrigerant flow system is one of the best heating, ventilation, and air conditioning systems (HVAC) thanks to its ability to provide thermal comfort inside buildings. But, at the same time, these systems are considered one of the most energy-consuming systems in the building sector. Thus, it is crucial to well size the system according to the building’s cooling and heating needs and the indoor temperature fluctuations. Although many researchers have studied the optimization of the building energy performance considering heating or cooling needs, using air handling units, radiant floor heating, and direct expansion valves, few studies have considered the use of multi-objective optimization using only the thermostat setpoints of VRF systems for both cooling and heating needs. Thus, the main aim of this study is to conduct a sensitivity analysis and a multi-objective optimization strategy for a residential building containing a variable refrigerant flow system, to evaluate the effect of the building performance on energy consumption and improve the building energy efficiency. The numerical model was based on the EnergyPlus, jEPlus, and jEPlus+EA simulation engines. The approach used in this paper has allowed us to reach significant quantitative energy saving by varying the cooling and heating setpoints and scheduling scenarios. It should be stressed that this approach could be applied to several HVAC systems to reduce energy-building consumption.