• Energy Research
• 2016-2025close
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Various systems and technologies have been developed in recent years to fulfil the growing needs of high-performance HVAC systems with better performance of energy efficiency, thermal comfort, and occupancy health. Intensified conditioning of human occupied areas and less intensified conditioning of surrounding areas are able to effectively improve the overall satisfaction by individual control of personalized micro-environments and also, achieve maximum energy efficiency. Four main concepts have been identified chronologically through the development of personal environmental conditioning, changing the intensified conditioning area closer to the human body and enhancing conditioning efforts, namely the task ambient conditioning (TAC) system, personal environmental control system (PECS), personal comfort system (PCS), and the personal thermal management (PTM) system. This review follows a clue of the concept progress and system evaluation, summarizes important findings and feasible applications, current gaps as well as future research needs.

The performance of a solar lighting and heating system (SLHS) based on the spectral splitting effect of nanofluids is presented in this paper. SLHS through nanofluids would split the sunlight spectrum into different wavelength, and then introduce the visible light into the offices for lighting and absorb infrared energy to generate hot water. The Energy Plus software was used to analyze the energy consumption of typical office building located in the city of Harbin in China coupled with SLHS. Based on the simulation results two lighting zones were identified in the offices and the optimal lighting control strategy was developed for a full year. The performance models of SLHS with different light-receiving areas of 10 m2 and 40 m2 were simulated and validated using the existing experimental data. The overall energy-saving of the offices over a full year were analyzed using the validated model. Results demonstrated that for SLHS with the area of 40 m2, the rate of the energy saving in the offices due to lighting and hot water systems were 58.9%, and 19.3%, respectively. The system also had the additional benefit of reducing the cooling load of the air conditioning system during summer period together with improving the quality of the indoor environment resulting in better health and productivity of the occupants.

Harvesting and storing energy is a key problem in some applications. Elastic energy storage technology has the advantages of wide-sources, simple structural principle, renewability, high effectiveness and environmental-friendliness. This paper elaborates the operational principles and technical properties and summarizes the applicability of elastic energy storage technology with spiral springs. Elastic energy storage using spiral spring can realize the balance between energy supply and demand in some applications. Continuous input–spontaneous output working style can provide simple energy sources for short-time energy supply, and provide strong moment impact and rapid start, or realize the energy conservation for reciprocating movement. Uniform output working style can realize energy output with uniform speed for timekeeping and load-driving. Random input working style can harvest and store random mechanical energy or convert small torque into a large moment to drive external loads. Finally, this paper proposes new researches and developments of elastic energy storage technology on new materials and structures, mechanical properties and structural dynamics analyses, design and control for new functions.

The nZEB objectives have raised the standard of building performance and changed the way in which buildings are designed and used. Although energy dynamic simulation tools are potentially the most suitable way for accurately evaluating and forecasting the thermal performance, they need several data inputs and user's knowledge that can affect the reliability of the results. It is precisely these two aspects that proved to be particularly critical, since the reliability of the ICT calculation tools has been widely proven in recent time.However, in order to foster credibility in sustainable architecture, bridging the gap between predicted and measured performance is pivotal to boost the building market towards energy efficiency and provide reliable data to inhabitant, investors and policy maker.The present research aims to identify and quantify the main factors that affect the energy performance gap through a detailed energy analysis carried out on a case study, which can be considered one of the first nearly zero energy residential complex built in Italy. Based on the analysis, the study identifies the main causes of the deviation between the calculated and measured data and demonstrates how it is possible to achieve very reliable models and, therefore, real buildings.Although the procedure traces a classic model calibration scheme, actually it consists of a verification of possible downstream errors mainly due to human factors, such as the provision of incorrect technical data or inappropriate operation.Some observations on the technical, management and regulatory gaps that may generate these errors are reported at the end of the study, together with practical suggestions that can provide effective solutions.

An appropriate microenvironment for preserving cultural relics is essential, and the air-water direct contact technology is utilized to create the microenvironment recently. The influence of a deflector in a tank was numerically investigated based on uniform design method to improve the heat and mass transfer and pressure drop performance of the air-water direct tank. In this study, a simplified CFD-based model was established and validated between airstream and water surface within the tank, to analyze the heat and mass transfer and pressure drop processes. Meanwhile, regression models of the heat transfers rate, mass transfer rate and pressure drop were developed by uniform design method based on three parameters: installation position, tilt angle, and height of the deflector, in order to analyze the influences of these three parameters on the heat and mass transfer and pressure drop of the tank. Finally, all three optimal structural parameters of the deflector were obtained based on the proposed comprehensive evaluation index using a genetic algorithm. The results showed that the model established for air-water direct contact adopted well to predict the heat and mass transfer and pressure drop performance between airstream and still water surface. Furthermore, the results found that the flow field inside the water tank was affected by the deflector's structure, which affected the heat and mass transfer performance. The simulation results suggested that the deflector's optimal structural parameters are 8 mm of installation position, 88 ° of tilt angle and 19 mm of height, respectively, within a given extent in this study.

Frosting is a common phenomenon of the ASHP under the heating mode in winter, and the outdoor air flow rate flowing through the evaporator of the ASHP was always thought to be a major contributor. In order to validate its contribution, effects of outdoor fan airflow rate on the performance of air source heat pumps (ASHPs) were investigated under the winter heating condition. The experiment was conducted in a laboratory at the standard 2 °C air dry bulb temperature (DB)/ 1 °C air wet bulb temperature (WB) frosting condition, which enabled the analysis of the operating performance, frosting performance, and heating performance of the ASHP unit by changing the airflow rate of the outdoor fan. Results showed that as the airflow rate of the outdoor fan reduced from 100% to 36%, the operating performance decline and the elevated frosting-defrosting loss were observed. Meanwhile, both the frosting rate and the operating efficiency during frosting-defrosting cycles showed an increasing trend then followed by decreasing tendency. The maximum frosting rate and operating efficiency were 0.92 g/m2.min and 2.92, respectively, which were observed at 74% airflow rate of the outdoor fan of the ASHP unit. The observation implied the existence of the “minimum frosting suppression airflow rate”. At 36% airflow rate of the outdoor fan of the ASHP unit, however, the performance of the ASHP unit was attenuated greatly, with the frosting-defrosting efficiency loss coefficient of 0.47, the heating capacity and COP reduction by 51.5 and 38.8%, respectively. These findings provided significant references to the optimization of ASHPs performance with variable airflow rate of the outdoor fan under frosting conditions.

The coupling and complexity of railway train / tunnel system are further aggravated by increasing train speed, which produces a series of aerodynamics problems, such as aerodynamic drag, slipstream, pressure wave and micro pressure wave. Aerodynamic effects of tunnels will result in a significant increase in train energy consumption, shorten life of railway train / tunnel system, and increase maintenance cost. This paper provides a review of aerodynamics of railway train / tunnel system. Challenges in railway train / tunnel system aerodynamics and their related factors are discussed firstly. Aerodynamic performance and flow field characteristics of trains in tunnels are presented. Relationship of aerodynamic effects and parameters of railway train / tunnel system, and the control methods for reducing aerodynamic effects in tunnels are explained. A traffic safety evaluation of the train in tunnels, such as vehicle body structure, passengers’ ear comfort, etc., is introduced and analysed. Finally, future outlooks and research topics are proposed.