Nianping Li

Statistical analyses on summer energy consumption characteristics of residential buildings in some cities of China

The purposes of this paper are to analyse energy consumption characteristics and to find out influence factors of residential energy consumption in summer in typical cities of China. The investigated residences were located in seven cities of five architecture thermotechnical design zones. Questionnaire surveys revealed housing unit characteristics, household characteristics, the possession and utilization of domestic energy consuming appliances and indoor thermal environment in summer. Energy consumption analyses show that summer energy consumption amounts in different cities bear distinct regional characteristics: the household amounts of electricity use are largest in Hongkong, and the values are smaller but still at a high level in Beijing, Shanghai and Changsha, and at the smallest level in Kunming, Harbin and Urumqi, while the difference in gas use is small among these cities. Influence factor analyses show that city locations, housing unit characteristics, the utilization of space coolers and water heaters, household characteristics, and subjective evaluation of indoor thermal environment all contribute to the residential energy consumption in summer when taking all the families in the seven cities as the sample collectivity, while detail analyses for separate cities shows each city has its own characteristics. In Shanghai, the satisfaction rate of thermal environment, the possession and operation of air conditioners and housing unit characteristics greatly affect the summer energy consumption, but the electrical fan is judged as the non-influence factor, while in Urumqi, the possession and operation of electrical fans and the categories of water heaters have remarkable effect, and the influence of housing unit characteristics is also distinct, but the number of air conditioners and their usage contribute little to energy use due to the cool climate.

An efficient solution method for predicting indoor environment of buildings with complex geometric configuration

Abstract An efficient solution method has been developed to solve two-dimensional steady flow in complex domain. The study is based on a control-volume formulation with Cartesian physical velocity components as the dependent variables in momentum equations. The strategies for implementing the hybrid convection schemes, maintaining the diagonal dominance and decoupling the pressure–velocity in irregular grid system have been presented. Comparing the results with other numerical results available in the literature has assessed the accuracy of the proposed algorithm. The ability of the method to handle complex geometry is illustrated through an example of airflow distribution in a large and complex geometric cinema hall.

Grey preference analysis of indoor environmental factors using sub-indexes based on Weber/Fechner's law and predicted mean vote

The purpose of this study was to determine the influences of environmental parameters on common health symptoms in office buildings. A grey preference analysis based on a new indoor environment quality (IEQ) index and a controlled field survey of 91 office occupants were conducted in an office building in Guangzhou, China. The new IEQ index based on Weber/Fechner’s law and predicted mean vote (PMV) was developed and validated by our survey. In the survey, the six environmental parameters (air temperature, illumination intensity, noise level, carbon dioxide, formaldehyde and PM10) were measured. The subjects’ satisfaction levels and the nine health symptoms (eye dryness, lethargy, dry throat, headache, nausea, skin dryness, blocked nose, influenza-like symptom and chest tightness) were determined using questionnaires. The results show that the proposed IEQ index can preferentially predict the subjective sensations of occupants. PM10 was identified as the most significant environmental parameter, followed by formaldehyde, air temperature, carbon dioxide, noise level and illumination intensity. Eye dryness and lethargy were the most significant symptoms, followed by dry throat, headache, nausea, skin dryness and chest tightness. Blocked nose and influenza-like symptom were hardly reported by subjects. The findings of this study could provide a practical guidance for IEQ management to reduce unhealthy diseases for occupants.

Research on the Energy Utilization Structure of Rural Residence in Hunan Province, China

Abstract The purposes of this study are to look into the actuality of rural residential energy consumption in Hunan province, China, to improve energy utilization structure, and to protect the environment. An investigation on rural residential energy consumption was carried out in the villages of Xintian and Jiangwan from March to May 2005. Common energy is used in Xintian while marsh gas is popularized in Jiangwan. A questionnaire survey covered basic information of residences in the two villages, and energy consumption of each family was also tracked continuously. In this paper, the energy utilization structures of the two villages are contrasted. Sequentially, the economic and environmental benefits are assessed when marsh gas substitutes biomass energy. The conclusions are summarized as follows: a complicated energy structure is still dominant, where biomass energy accounts for a significant proportion and manifold energies exist simultaneously; and consumption of the energy is high. Nevertheless the usage of marsh gas makes a great contribution in optimizing energy consumption structure, which could reduce energy consumption and domestic costs, discharge less harmful gases and keep the ecosystem in balance. The comparison between common energy and ecotype energy provides instructions for the future development of rural residential energy consumption.

Discussion Regarding the Principles of Exergy Analysis Applied to HVAC Systems

Abstract Exergy is another name for available energy that measures the ability of the energy source to produce useful work. This article provides an analytical review of some pertinent works in HVAC application. Some general conclusions can be obtained. Exergy efficiency is more rational than energy efficiency; exergy analysis is more helpful than energy analysis for locating and evaluating available energy saving potentials, identifying opportunities for improvements in system design and establishing cost effective system mainte-nance programs. In addition, an unusual selection of dead–states novel to HVAC applications is suggested, which simplifies the exergy analysis by eliminating the necessity of calculating the exergy of water at ambient temperature (T0). Such a selection will also make it easier to evaluate the precooling capacity of moist air. In this paper, the authors also suggest a functional classification to break down the HVAC project in a hierarchical structure for exergy analysis. The HVAC system is considered as an exergy service system that provides exergy for pure consumption in exergy consumer systems such as conditioning space. The exergy service system can be further broken down into different components. The exergy flows are also classified according to their functions as source exergy flow and service exergy flow to assist the evaluation of the performance of the systems or components. Relevant principles of exergy analysis are discussed. Finally, examples are calculated to demonstrate the application and the reasonability of the above propositions.

Study on the Optimizing Operation of Exhaust Air Heat Recovery and Solar Energy Combined Thermal Compensation System for Ground-Coupled Heat Pump

This study proposed an exhaust air heat recovery and solar energy combined thermal compensation system (ESTC) for ground-coupled heat pumps. Based on the prediction of the next day’s exhaust air temperature and solar irradiance, an optimized thermal compensation (OTC) method was developed in this study as well, in which the exhaust air heat recovery compensator and solar energy compensator in the ESTC system run at high efficiency throughout various times of day. Moreover, a modified solar term similar days group (STSDG) method was proposed to improve the accuracy of solar irradiance prediction in hazy weather. This modified STSDG method was based on air quality forecast and AQI (air quality index) correction factors. Through analyzing the operating parameters and the simulation results of a case study, the ESTC system proved to have good performance and high efficiency in eliminating the heat imbalance by using the OTC method. The thermal compensation quantity per unit energy consumption (TEC) of ESTC under the proposed method was 1.25 times as high as that under the traditional operation method. The modified STSDG method also exhibited high accuracy. For the accumulated solar irradiance of the four highest daily radiation hours, the monthly mean absolute percentage error (MAPE) between the predicted values and the measured values was 6.35%.

Investigation on Indoor Air Pollution and Childhood Allergies in Households in Six Chinese Cities by Subjective Survey and Field Measurements

Greater attention is currently being paid to the relationship between indoor environment and childhood allergies, however, the lack of reliable data and the disparity among different areas hinders reliable assessment of the relationship. This study focuses on the effect of indoor pollution on Chinese schoolchildren and the relationship between specific household and health problems suffered. The epidemiological questionnaire survey and the field measurement of the indoor thermal environment and primary air pollutants including CO2, fine particulate matter (PM2.5), chemical pollutants and fungi were performed in six Chinese cities. A total of 912 questionnaires were eligible for statistical analyses and sixty houses with schoolchildren aged 9–12 were selected for field investigation. Compared with Chinese national standards, inappropriate indoor relative humidity (<30% or >70%), CO2 concentration exceeding 1000 ppm and high PM2.5 levels were found in some monitored houses. Di(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) were the most frequently detected semi-volatile organic compounds (SVOCs) in house dust. Cladosporium, Aspergillus and Penicillium were detected in both indoor air and house dust. This study indicates that a thermal environment with CO2 exceeding 1000 ppm, DEHP and DBP exceeding 1000 μg/g, and high level of PM2.5, Cladosporium, Aspergillus and Penicillium increases the risk of children’s allergies.

Using Upper Extremity Skin Temperatures to Assess Thermal Comfort in Office Buildings in Changsha, China

Existing thermal comfort field studies are mainly focused on the relationship between the indoor physical environment and the thermal comfort. In numerous chamber experiments, physiological parameters were adopted to assess thermal comfort, but the experiments’ conclusions may not represent a realistic thermal environment due to the highly controlled thermal environment and few occupants. This paper focuses on determining the relationships between upper extremity skin temperatures (i.e., finger, wrist, hand and forearm) and the indoor thermal comfort. Also, the applicability of predicting thermal comfort by using upper extremity skin temperatures was explored. Field studies were performed in office buildings equipped with split air-conditioning (SAC) located in the hot summer and cold winter (HSCW) climate zone of China during the summer of 2016. Psychological responses of occupants were recorded and physical and physiological factors were measured simultaneously. Standard effective temperature (SET*) was used to incorporate the effect of humidity and air velocity on thermal comfort. The results indicate that upper extremity skin temperatures are good indicators for predicting thermal sensation, and could be used to assess the thermal comfort in terms of physiological mechanism. In addition, the neutral temperature was 24.7 °C and the upper limit for 80% acceptability was 28.2 °C in SET*.

Experimental Study on Unsteady State Properties of Ceiling Radiant Cooling Panels System

Ceiling radiant cooling panels (CRCP) system is more comfortable and energy-saving than the traditional convection air-conditioning system according to the research of pioneers. The former research was concentrated in the feasibility, thermal comfort, and energy saving of the CRCP system. Changes of the system parameters are not described systematically under unsteady state. There are hardly any complete and credible reference materials for engineers to design CRCP system of buildings. In this paper, the radiant thermal performance was studied in the experimental platform, and the operating data of the CRCP system was collected in the startup phase and regulating phase of the platform. The results shows that the thermal inertia of the metal radiant panel is small and the response of thermal parameters is very fast under unsteady state in the experiment. The distribution of the surface temperature is uniform on the cool ceiling, and the heat transfer resistances are basically the same among different cooling panels. Learning the changing rules of the CRCP system would provide the engineers reference materials for running control, design, and assessment of the system in the future.

Development of Thermoelectric Heat Pump Water Heaters

Abstract Experiments verified that a thermoelectric heat pump system is more efficient than an electrical heating device, for its heating coefficient reached more than 1.6 with suitable operating conditions. Two novel instantaneous water heaters were developed and tested successively. The prototype with circulating water pump can save power consumption more than 40% in comparison with conventional electric water heaters, while the prototype integrating with thermosiphon can save more than 38%. Comparing two prototypes, the latter prototype becomes more compact, more technologically advanced and practical, because it eliminated the working life choke-point of the former, while holding the advantages, such as high efficiency, reliability, safety, environmental friendly.