Parametric study on the performance of green residential buildings in China

The parametric study of the indoor environment of green buildings focuses on the quantitative and qualitative improvement of residential building construction in China and the achievement of indoor thermal comfort at a low level of energy use. This study examines the effect of the adaptive thermal comfort of indoor environment control in hot summer and cold winter (HSCW) zones. This work is based on a field study of the regional thermal assessment of two typical cases, the results of which are compared with simulated results of various scenarios of “energy efficiency” strategy and “healthy housing” environmental control. First, the simulated results show that the adaptive thermal comfort of indoor environment control is actually balanced in terms of occupancy, comfort, and energy efficiency. Second, adaptive thermal comfort control can save more energy for heating or cooling than other current healthy housing environmental controls in China's HSCW zone. Moreover, a large proportion of energy use is based on the subjective thermal comfort demand of occupants in any building type. Third, the building shape coefficient cannot dominate energy savings. The ratio of the superficial area of a building to the actual indoor floor area has a significant positive correlation with and affects the efficiency of building thermal performance.     

独立别墅热水供暖系统动态模型、控制策略及能耗分析

建立了独立别墅供暖系统的非线性动态模型并分析了其动态特性,介绍了模型降阶方法及PI控制器参数的设计和整定。针对可能的供暖系统控制策略进行了动态仿真和能耗分析。仿真结果表明,单纯采用室外气候补偿控制模式并不能获得理想的控制效果;采用分室控制模式能满足室内舒适性要求并有一定的节能效果,节能率约为25%。     

电加热相变蓄热地板供暖房间热特性数值模拟与分析

介绍了电加热相变蓄热地板供暖的优点，综合考虑室外气象因素、室内辐射特性和相变材料自身的热物性建立了电加热相变蓄热地板供暖系统的计算模型。比较了相变蓄热地板与传统散热器供暖的热舒适性和能耗，结果表明相变蓄热地板能够改善室内热舒适性和降低能耗。     

覆土建筑冬季室内热舒适性研究

通过对西安地区某覆土建筑冬季室内热环境的测试,分析了测试房与对比房的温度测试数据。结果表明测试房内各测点逐时温度均高于对比房,室内温度变化幅度也明显小于对比房,且覆土建筑的室内温度略高于当地室内设计采暖温度。在测试的基础上采用主观温度法对室内热舒适性进行参考性评价,结果显示测试房室内热环境较好地满足了使用者对热舒适的需求。因此,覆土建筑在冬季能够有效维持室内温度,提高热舒适性,同时能够降低建筑采暖能耗。     

Indoor thermal environment and energy saving for urban residential buildings in China

The purpose of this survey is to investigate the actual conditions of the residential indoor thermal environment in urban areas in China for evaluating thermal comfort and predicting the energy conservation feasibility for space heating and cooling.The apartment homes under investigation were located in the urban areas of nine major cities. The questionnaire survey revealed building characteristics, the types of space heating and cooling system in use, aspects of life style, during winter and summer seasons, and so on. The measurement showed that winter indoor temperatures in Harbin, Urumqi, Beijing and Xi’an remain at a relatively stable level near 20 °C due to the central heating system installed. However in the other cities lacking central heating systems, indoor temperatures fluctuated as a function of the change of outdoor temperature. On the other hand, summer indoor evening temperatures in Shanghai, Changsha, Chongqing and Hong Kong were higher than the comfort zone of ASHRAE. Therefore it is expected that energy use for space heating and cooling in the southern China will increase in the near future because of occupants’ requirement for comfortable indoor environment. Based on the results yielded by this study, in Beijing the calculation of space heating and cooling loads indicated that the energy used to heat indoor spaces can be halved by installing thermal insulation and properly sealing the building.     

基于Zonal Model信息的单体建筑热水供暖系统控制策略仿真

本文通过创建房间Zonal Model和热水供暖系统数学模型,模拟分析了室内空气温度场和速度场的分布及控制系统动态响应.而后利用测试室温作为反馈信号,对3种控制策略的控制效果和能耗进行了模拟.结果显示,基于Zonal Model信息的控制系统能够反映供暖系统的动态变化过程;仅采用室外气候补偿器时的室温波动较大;应用供水温度和散热器循环流量两级控制策略既可提高室内热舒适性和控制精度,又可获得10.5％～15.9％的节能效益.     

Improved indoor thermal comfort during defrost with a novel reverse-cycle defrosting method for air source heat pumps

When an air-source heat pump (ASHP) unit is used for space heating at a low ambient temperature in winter, frost may be formed on its outdoor coil surface. Frosting affects its operational performance and energy efficiency, and therefore periodic defrosting is necessary. Currently, the most widely used standard defrosting method for ASHP units is reverse-cycle defrost. During a standard reverse-cycle defrosting process, the indoor coil in an ASHP unit actually acts as an evaporator, therefore, no heating is provided and hence indoor air temperature in a heated space can drop. Furthermore, a longer period of time is needed before space heating can become available immediately after the completion of defrosting. Consequently, occupants’ thermal comfort may be adversely affected. To improve the indoor thermal comfort for occupants during reverse-cycle defrosting, a novel thermal energy storage (TES) based reverse-cycle defrosting method has been developed and the improvement to occupants’ thermal comfort experimentally evaluated and is reported in this paper. Comparative experiments using both the novel TES based reverse-cycle defrosting method and the standard reverse-cycle defrosting method were carried out. Experimental results and the evaluated indoor thermal comfort indexes clearly suggested that when compared to the use of standard reverse-cycle defrost, the use of the novel reverse-cycle defrosting method can help achieve improved indoor thermal comfort, with a shorter defrosting period and a higher indoor supply air temperature during defrosting.     

Optimization of a liquid desiccant based dedicated outdoor air-chilled ceiling system serving multi-zone spaces

A liquid desiccant based dedicated outdoor air-chilled ceiling (DOAS-CC) system is proposed to serve a multi-zone space. The outdoor airflow rate and the supply air humidity ratio are two crucial variables in such a system, which significantly influence indoor thermal comfort, indoor air quality and energy consumption. Two strategies are presented to optimize these two variables in the study. They are the demand-controlled ventilation (DCV) strategy and the supply air humidity ratio set-point reset strategy. To evaluate the performances of these two strategies, a basic control strategy, i.e., the strategy adopting constant ventilation flow rate and constant supply air humidity ratio, is selected as the benchmark. Performances of the two strategies in terms of indoor air temperature, relative humidity and CO₂ concentration as well as energy consumption are analyzed using simulation tests. The results show that the supply air humidity ratio set-point reset strategy is effective for the indoor air humidity control. It can save about 19.4% of total energy consumption during the whole year. The DCV-based ventilation strategy can further reduce about 10.0% of energy consumption.     

Improvement of intermittent central heating system of university building

Most universities in Korea use intermittent central heating system which operates according to a preset intermittent schedule that is determined based on outdoor air temperature. This system is popular for university buildings due to its low initial cost and simple operation. But since it is not based on feedback control, the indoor thermal comfort is unsatisfactory. In this research, problem with the current control system is studied by experiment and dynamic simulation. The measurement shows that the indoor temperature rises to an uncomfortable range during heating and falls below comfortable range when heating is off. To solve this situation, an on-off control is implemented and simulated using a dynamic simulation program. Since there is a good agreement between experiment and dynamic simulation results, dynamic simulation is used to predict other results with different conditions of interest. The simulation shows that by implementing on-off control, the indoor space can be maintained within comfortable range, moreover using less energy. By reinforcing insulation to the walls that are exposed to the outdoor environment, heating energy can be saved further.     

A new method of determination of indoor temperature and relative humidity with consideration of human thermal comfort

A new method is described in this article for selecting indoor temperature and indoor relative humidity to achieve minimum energy consumption for a required indoor thermal comfort level which is evaluated with indoor effective temperature. This method is derived from a central air-conditioning system and is based on our investigation that under a same indoor effective temperature, the system cooling load and the system energy consumption increase with an increase of indoor temperature. As such, energy consumption cannot be reduced with increasing indoor temperature for a given human thermal comfort level. In order to reduce energy consumption while keeping a same indoor thermal comfort level, indoor temperature and relative humidity may be determined with the proposed method described in this article. With the proposed method, a parameter variation study has also been conducted, which suggests that for a given indoor effective temperature, a combination of high indoor relative humidity and low indoor temperature be generally taken. The proposed method is based on the central air-conditioning system; yet it can be easily extended to other systems.     

Modeling of the heating system in small building for control

Model identifications for the heating system of small building are presented. Basic problems of data acquisition and preprocessing are detailed. Specially designed wire-less data collection and control system to conduct real-world experiments are described. The model structure choice based on analysis of weather condition influences on the system performance are presented. Finally, the general structure of two-layered heating control strategy for the heating system is proposed. Instead of heating, ventilating and air conditioning (HVAC) standard, the proposed strategy controls only indoor temperature and changes the set point according to additional measurements of indoor humidity to keep thermal comfort. Non-linear compensation of outdoor temperature and wind speed is also introduced.     

Energy conservative building air conditioning system controlled and optimized using fuzzy-genetic algorithm

In this work, the combined effect of the energy conservative variable refrigerant volume (VRV) system and the variable air volume (VAV) system was experimentally investigated using genetic fuzzy optimization method that yielded better thermal comfort, indoor air quality (IAQ) requirements without compromising on the energy savings potential. The proposed system was tested using the demand controlled ventilation (DCV) combined with the economizer cycle ventilation (ECV) techniques and examined for a year-round building air conditioning (A/C) application. The supply air temperature (SAT) set points were varied under three distinct strategies and the optimal solutions obtained for the fuzzy systems designed resulted in an enhanced energy conservative potential. The test results of the proposed system were compared with the conventional fan coil A/C system. Based on the three strategies of the supply air temperature, the proposed system yielded an improved per day energy savings potential of 54% in summer and 61% in winter design conditions. Furthermore, for the strategies considered the proposed system achieved an annual energy conservative potential of 36% and exhibited more possible ways to achieve thermal comfort, IAQ and energy conservation.     

Optimization of air-conditioning system operating strategies for hot and humid climates

This paper describes research into the optimal operation of building heating, ventilation, and air-conditioning (HVAC) systems focusing on both temperature and humidity control. While most previous work on HVAC optimization has been limited to evaluation of conventional temperature-based control systems, this study emphasizes the humidity control issue in meeting both sensible and latent building loads. The analysis is based on a combination of a realistic simulation of a direct expansion (DX) air-conditioning system and a direct-search numerical optimization technique. The simulation models have been validated through comparisons with field data. Optimization was performed on five different system control variables to minimize system power consumption while meeting building loads and maintaining comfort. Indoor temperature and humidity are also optimized within standard comfort constraints. Building loads were modeled using an extended bin method that allows consideration of the interactions between loads and indoor conditions. Results indicate that minimum energy use typically occurs at low airflow rates, with indoor humidity levels below the upper comfort limit. Results also show that coil air bypass and evaporator circuiting control are typically not necessary unless operation would otherwise result in overcooling. The optimization results also translate to relatively simple strategies for system control. Significant savings are demonstrated over conventional control strategies used in packaged DX equipment.     

Indoor thermal environment of urban residential buildings in China: winter investigation in five major cities

The purposes of this investigation are to look into the actual conditions of urban residential indoor environment in China during the winter season, and to discuss the thermal comfort as well as to understand the possibility of space heating energy conservation. Investigations of indoor thermal environment were carried out in Harbin, Beijing, Xi’an, Shanghai and Hong Kong of China. The results showed that the indoor thermal condition in heating usage zone is good, such as Harbin, Beijing and Xi’an. The indoor thermal comfort is strongly affected by the outdoor climate in non-heating usage zone, such as Shanghai and Hong Kong.     

The impact of indoor thermal conditions,system controls and building types on the building energy demand

It is possible to evaluate the energy demand as well as the parameters related to indoor thermal comfort through building energy simulation tools. Since energy demand for heating and cooling is directly affected by the required level of thermal comfort, the investigation of the mutual relationship between thermal comfort and energy demand (and therefore operating costs) is of the foremost importance both to define the benchmarks for energy service contracts and to calibrate the energy labelling according to European Directive 2002/92/CE. The connection between indoor thermal comfort conditions and energy demand for both heating and cooling has been analyzed in this work with reference to a set of validation tests (office buildings) derived from a European draft standard. Once a range of required acceptable indoor operative temperatures had been fixed in accordance with Fanger's theory (e.g. −0.5 < PMV < −0.5), the effective hourly comfort conditions and the energy consumptions were estimated through dynamic simulations. The same approach was then used to quantify the energy demand when the range of acceptable indoor operative temperatures was fixed in accordance with de Dear's adaptive comfort theory.     

兼顾节能效益的建筑室内热舒适温度调整研究

各气候区居民对室内热舒适的要求随其穿着习惯、对热环境的适应能力等而异,采暖或制冷温度应有所差别,然而现有建筑节能设计标准按统一标准提供室温控制建议。采用ISO7730的PMV热舒适模型分析各气候区的合理参数,计算得到室内热舒适温度,并通过与实测值比较验证理论计算的合理性;在此基础上,分别计算按既有统一室温建议与热舒适温度控温的热舒适性和能耗,提出冬季适当提高采暖温度以提升热舒适度、夏季适当提高制冷温度以实现热舒适度和节能双赢的调整建议。     

A combined system of chilled ceiling,displacement ventilation and desiccant dehumidification

Different types of heating, ventilation, and air-conditioning (HVAC) systems consume different amounts of energy yet they deliver similar levels of acceptable indoor air quality (IAQ) and thermal comfort. It is desirable to provide buildings with an optimal HVAC system to create the best IAQ and thermal comfort with minimum energy consumption. In this paper, a combined system of chilled ceiling, displacement ventilation and desiccant dehumidification is designed and applied for space conditioning in a hot and humid climate. IAQ, thermal comfort, and energy saving potential of the combined system are estimated using a mathematical model of the system described in this paper. To confirm the feasibility of the combined system in a hot and humid climate, like China, and to evaluate the system performance, the mathematical model simulates an office building in Beijing and estimates IAQ, thermal comfort and energy consumption. We conclude that in comparison with a conventional all-air system the combined system saves 8.2% of total primary energy consumption in addition to achieving better IAQ and thermal comfort. Chilled ceiling, displacement ventilation and desiccant dehumidification respond consistently to cooling source demand and complement each other on indoor comfort and air quality. It is feasible to combine the three technologies for space conditioning of office building in a hot and humid climate.     

Controlling building indoor temperature and reducing heating cost through night heating electric stove

This paper investigates the use of massive electric stove as a thermal storage in order to reduce the heating cost associated with maintaining indoor comfort condition in building. The control of electric stove takes advantage of low night-time electrical rate by shifting heating loads from day-time to night-time. A general numerical modelling of thermal behaviour of building envelope, electric stove and indoor air under the condition of outdoor variation is presented in detail. The resultant non-linear system of the heat balance equations, partial differential equations, is solved numerically. Besides the modelling work, attention is put on the control of electric stove’s night heating in such way that the stove-stored energy is released during day-time without sacrifice of indoor comfort. A simple control algorithm is given. Model applications show that the night heating with a proper size massive electric stove as a building thermal storage is cost-effective for buildings with night electrical rate benefit, while maintaining a comfortable indoor temperature in the building. Simulation also illustrates that up to 28% heating cost saving can be obtained compared with conventional direct heating.     

Research on seasonal indoor thermal environment and residents' control behavior of cooling and heating systems in Korea

Indoor thermal environments and residents' control behavior of cooling and heating systems were investigated in Seoul, Korea and compared with the results of previous studies. Twenty-four houses in summer, six houses in autumn and 36 houses in winter were used in this study. The measurement of temperature, humidity and air conditioner usage behavior was carried out. The clo-value, thermal comfort, sensation and basic data of the houses were also investigated. The indoor thermal environment in the summer had a high temperature and a high humidity ratio compare to standard comfort zone. Most of the indoor thermal environments at the time of starting the air conditioner in the summer were out of the comfort zone. Some of the data recorded while the air conditioner was stopped were in the comfort zone, but in many cases the temperature was relatively higher than comfort zone. Most indoor climate distributions in the winter were in the comfort zone and the indoor climate in autumn coincided well with the criteria of the comfort zone. Compared with results of previous studies in these 25 years, indoor ambient average temperature in winter has increased and the comfort temperature has increased in the heating period and decreased in the cooling period. This result indicates that the development of an HVAC system has created an expectation of comfort for residents and has shifted their thermal comfort zone warmer in winter and cooler in summer.     

太阳能热泵相变储能复合地板辐射采暖系统

太阳能地板辐射采暖系统与相变储能技术结合使用是新能源利用的一种重要方法。介绍了一种太阳能、热泵、低谷电辅热与相变储能地板联合运行的复合地板辐射采暖系统;讨论了系统组成、运行原理以及运行流程;分析了该采暖系统在节能环保、室内热舒适性等方面的优点;展望了其良好的发展前景。