Abstract
People spend almost 90% of their time indoors. Indoor air quality (IAQ) has a significant impact on human health, comfort, and productivity. The energy consumption of building sector accounts for about one-third of the total energy consumption all over the world. Therefore, more and more attentions should be paid to building energy efficiency and indoor environment. Heating, ventilation, and air-conditioning (HVAC) system plays an important role in built environment and the energy consumption of HVAC accounts for more than 50% of the total building energy consumption. Air distribution caused by air terminal devices (ATDs), air handling unit (AHU), and delivery systems of conditioned air and chilled/chilling water and chiller/boiler plants are the main contributors of indoor environment. Any progress in the three parts of HVAC system will benefit the healthy indoor environment and/or building energy efficiency.
The aim of this special issue is to collect the original research and review papers on the recent development in the field of building energy efficiency and healthy indoor environment. In this special issue, we received 18 related manuscripts from Italy, China, Algeria, India, Iran, Qatar, and Turkey. After peer review, 10 manuscripts have been accepted for publication. There are four main categories of manuscripts in the special issue. A brief overview of the manuscripts is as follows.
Passive technology is usually with priority to reduce the cooling/heating load. In the paper titled “Study on the application of cool paintings for the passive cooling of existing buildings in Mediterranean climates,” V. Costanzo et al. investigated the effectiveness of cool roofs (highly reflective cool materials) as a passive strategy for passive cooling in moderately hot climates. The phase change material (PCM) can reduce energy consumption, when it is combined with the building envelope. However, there is a lack of standard testing methods of the thermal physical properties of PCM. In the review paper titled “Comments on thermal physical properties testing methods of phase change materials,” J. Xie et al. summarized the different existing testing methods of PCM in terms of testing principle, advantages, and disadvantages. In the paper titled “Analytical method for heat conduction problem with internal heat source in irregular domains,” H. Fan et al. presented an analytical method to solve the heat conduction problem in irregular domains, which may benefit the performance of advanced building envelope.
The efficiency of cooling/heating plants is always the most important aspect for energy saving in HVAC. To improve the heating efficiency, the air source heat pump assisted by a low-temperature solar-heated water system was proposed and experimentally studied by J. Wu et al. in “Experimental study of the performance of air source heat pump systems assisted by low-temperature solar-heated water” and the ammonia-based air source absorption heat pump was proposed and studied on crystallization by W. Wu et al. in “Crystallization analysis and control of ammonia-based air source absorption heat pump in cold regions.” The latter can also solve the problems of lower energy efficiency and high air pollution with traditional boiler systems.
Control strategy of a HVAC system is closely related to energy saving and thermal comfort. In the paper titled “Predicting cooling loads for the next 24 hours based on general regression neural network: methods and results,” Y. Sun et al. investigated the modeling methods of applying the general regression neural network (GRNN) technology to predict the cooling load for the next 24 hours, which is essential for the optimal control of air-conditioning systems that use thermal cool storage. In the paper titled “Experimental study on intelligent control scheme for fan coil air-conditioning system,” Y. Li et al. investigated the effectiveness of different control schemes including the traditional PID control, fuzzy control, and fuzzy-PID control for fan coil air-conditioning system by experiments.
As one of the most important projects, HVAC systems in subway not only consume huge energy but also provide acceptable environment to passengers. Z. Li et al. investigated how to effectively use the subway piston effect and natural outdoor cold sources to save energy in “The effective use of the piston effect, natural cold sources, and energy saving in Beijing subways.” S. Pan et al. reviewed the piston effect in subway stations in terms of mechanism, influence, and utilizing approach in “A review of the piston effect in subway stations.” In the paper titled “Experimental research and modeling of particle deposition in ventilation ducts,” H. Fan and J. Hua analyzed the behavior of resuspension in air flow by a set of experiments and improved the particle deposition model by adding a resuspension item to the equation, which may benefit improving the air quality not only in subway but also in residential and commercial buildings.
In summary, this special issue reflects a variety of recent progresses in building energy efficiency and healthy indoor environment and is expected to promote further research activities in this field.
Footnotes
Acknowledgments
We thank the authors who prepared the papers seriously according to the requirements. Our special thanks are given to the anonymous reviewers who provided valuable questions and suggestions, which help to improve the quality of the special issue. It is the authors and reviewers’ efforts that make this special issue available. We hope that the readers can find some useful information for their research. We would be pleased to receive any comments from any reader.