Uncertainties in energy and economic performance of HVAC systems and energy recovery ventilators due to uncertainties in building and HVAC parameters

Energy recovery ventilators (ERVs) are exhaust air energy recovery devices for outdoor ventilation air preconditioning in building HVAC systems. The energy and economic performance of an ERV depends on its effectiveness, cost, maintenance as well as other parameters such as climate, building design and HVAC system parameters. In this study, a sensitivity analysis is used to evaluate the impact of uncertainty of building and HVAC system parameters on the energy savings potential and economics of ERVs. Firstly, the impact of building parameters on HVAC system peak loads, capital cost, annual energy use and operating cost are investigated for an office building located in Chicago using TRNSYS simulations. The results show that the ventilation rate has the most significant impact on total HVAC system energy performance. Secondly, energy and economic analysis on the ERV’s payback period is conducted with a specified variation of each input parameter. The results illustrate that an ERV with 75% sensible and 60% latent effectiveness can reduce the peak heating load by 30%, the peak cooling load by 18%, the annual heating energy usage by 40% and the annual cooling energy usage by 8%, with a payback period of 2 years. The uncertainty of ERV’s payback period to its initial cost, recovery effectiveness, energy rate, HVAC equipment initial cost and efficiency as well as ventilation rate are also presented. A ±25% uncertainty in the 7 building and HVAC system input parameters studied results in a maximum 17% and 225% uncertainty in the payback period of the ERV respectively.     

Simulation of HVAC systems

Very powerful simulation softwares are available today. They should allow rational choices from early design stages, among many different alternatives. When using such tools, the bottle neck is no more on computer side but in the modelling. Better and better compromises have always to be found in order to guarantee at the same time easy understanding, easy use and easy improvement of the models. Some examples of such compromises are very briefly presented hereafter.     

Review of possibilities and necessities for building lifetime commissioning

The article presents review of possibilities and necessities for a practical application of lifetime commissioning in building facilities. The implementation of life-long commissioning of buildings implies energy efficiency, ensures a rational use of energy and thereby decreases CO₂ emissions. Therefore, first the term “commissioning” is explained in the article. Commissioning necessities, which are induced by different operational faults, the new laws driven by idea for decreasing CO₂ emission, and benefits, are explained, too. Besides USA's and European laws for the energy performance of buildings, the Norwegian state of the art in this area is also presented. The difference in terms and methods for fault detection and diagnosis are elaborated in the article. Finally, examples of different commissioning tools are briefly introduced and compared. In order to make building sustainable and encourage energy savings, potential commissioning users are suggested.     

Feasibility study of an ice slurry-cooling coil for HVAC and R systems in a tropical building

The study applies the software Transient Systems Simulation Program (TRNSYS) to estimate the air conditions as well as the energy consumption of a typical library located in a tropical climate country. The simulation uses Typical Meteorological Year (TMY) weather data for Kuala Lumpur as the research site, which is the Dentistry library in University of Malaya is located in Kuala Lumpur. The current HVAC and R systems of the library are found to be inherently energy-inefficient and potentially improvable with an ice slurry-cooling coil. The impact on energy consumption and space thermal comfort of a custom-built AHU with an ice slurry-cooling coil incorporated in the HVAC and R systems is simulated in comparison to the baseline system.     

Review of building energy-use performance benchmarking methodologies

This paper is to review what kinds of mathematical methods used in developing benchmarking systems, to discuss the properties of the methods, and to classify two kinds of benchmarking systems based on their properties. We find that while benchmarking systems are developed by using the energy-use performance of a significant number of reference buildings, benchmarking results can be used to encourage poor reference performers (in energy-efficiency) to improve their performance. On the other hand, because benchmarking systems also function as a public yardstick of energy-use performance in buildings, some regulators release benchmarking information to the media. This proves advantageous because it brings public pressure on owners/developers of poorly performing non-reference buildings. However, not all benchmarking systems can be used by public users (i.e., other non-reference building owners). Depending on whether the resulting benchmarking system can be used in public, we note that there are two kinds of benchmarking system: public benchmarking and internal benchmarking. These two types of benchmarking system are developed by different methods.     

室温传感器偏差故障对武汉地区暖通空调系统的影响研究

暖通空调系统的高效节能运行高度依赖于传感器测量的准确性。在传感器全寿命运行周期中,不可避免发生各种故障,影响其准确性。为探究传感器故障对不同暖通空调系统的影响,文章以室温传感器偏差故障为例,针对武汉地区某办公建筑,同时开展地源热泵和冷水机组+锅炉两种暖通空调系统形式的能耗建模,对比分析-5℃~+5℃偏差故障对两种系统运行能耗、工作性能及室内热舒适性的影响差异。结果表明:室温传感器故障的偏差幅值方向对两种系统运行能耗、工作性能及室内热舒适性的影响规律不同。其中,地源热泵系统能耗受室温传感器偏差故障影响相对更小。     

Retro and on-going commissioning tool applied to an existing building: Operability and results of IPMVP

The new building thermal regulations, mainly published to reduce greenhouse gases emissions, leads to a continuous improvement of building envelopes. On the other hand, the technical performance of the air-conditioning plants, ensured by commissioning procedures, becomes a key point for the control of energy needs in buildings. The essential work of Annex 40 of the International Agency of the Energy reports on “Commissioning of Building HVAC systems for Improved Energy Performance”. In this annex, the test of the IPMVP, International Performance Measurement and Verification Protocol, which is a significant and commonly used tool, is carried out among many others. This paper aims to present and detail the methodology of the IPMVP application and the results of four different calculation options applied to an existing building equipped with an innovative HVAC device, where outdoor airflow rate is controlled by indoor CO₂ rate. This work provides a helpful advice to the energy service company to determine the most adequate option in terms of accuracy, cost and speed of execution according to the available parameters (measurements, software) and the energy saving measure.     

相变储能在建筑供暖空调领域的应用前景

介绍储能相变材料及其分类,讨论相变材料在建筑供暖空调领域的应用研究。详细介绍作为相变墙体材料和系统相变材料的研究进展,同时对相变材料在建筑供暖空调系统中的应用前景进行展望。     

Energy systems engineering: methodologies and applications

Energy systems are the major contributor to ever-increasing primary energy consumption and consequent greenhouse gas emissions. To tackle these critical problems, planning and design of energy systems needs to be improved towards a more efficient, cost-effective, and environmentally benign direction. However, although there are many technical choices available, they are often developed separately by their own technical communities and driven by their specific interest, thus methods and experience obtained in planning and design of a certain type of energy systems are usually not applicable to other types of energy systems. Energy systems engineering provides a generic methodological framework to facilitate the planning and design of energy systems and to produce integrated solutions to real-life complex energy problems via a systematic approach.In this paper, we present an overview of key methodologies of energy systems engineering, covering superstructure based modelling, mixed-integer programming, multi-objective optimization, optimization under uncertainty, and life-cycle assessment. Applications of these methodologies in polygeneration energy systems design, hydrogen infrastructure planning, and design of energy systems in commercial buildings are provided to demonstrate the capability of these methodologies.     

Energy systems engineering: methodologies and applications

Energy systems are the major contributor to ever-increasing primary energy consumption and consequent greenhouse gas emissions. To tackle these critical problems, planning and design of energy systems needs to be improved towards a more efficient, cost-effective, and environmentally benign direction. However, although there are many technical choices available, they are often developed separately by their own technical communities and driven by their specific interest, thus methods and experience obtained in planning and design of a certain type of energy systems are usually not applicable to other types of energy systems. Energy systems engineering provides a generic methodological framework to facilitate the planning and design of energy systems and to produce integrated solutions to real-life complex energy problems via a systematic approach.     

An approach to optimised control of HVAC systems in indoor swimming pools

Indoor swimming pools are recognised as having a high level of energy consumption and present a great potential for energy saving. The energy is spent in several ways such as evaporation heat loss from the pool, high rates of ventilation required to guarantee the indoor air quality, and ambient temperatures with expressive values (typically 28?30°C) required to maintain conditions of comfort. This paper presents an approach to optimising control of heat ventilation and air conditioning systems that could be implemented in a building energy management system. It is easily adapted to any kind of pool and results in significant energy consumption reduction. The development and validation of the control model were carried out with a building thermal simulation software. The use of this control model in the case study building could reduce the energy efficiency index by 7.14 points (7.4% of total) which adds up to an energy cost saving of 15,609€ (7.5% of total).     

The map of energy flow in HVAC systems

Heating, ventilation and air conditioning (HVAC) systems are the most energy consuming building services representing approximately half of the final energy use in the building sector and between one tenth and one fifth of the energy consumption in developed countries. Despite their significant energy use, there is a lack of a consistent and homogeneous framework to efficiently guide research and energy policies, mainly due to the complexity and variety of HVAC systems but also to insufficient rigour in their energy analysis. This paper reviews energy related aspects of HVAC systems with the aim of establishing a common ground for the analysis of their energy efficiency. The paper focuses on the map of energy flow to deliver thermal comfort: the HVAC energy chain. Our approach deals first with thermal comfort as the final service delivered to building occupants. Secondly, conditioned spaces are examined as the systems where useful heat (or coolth) is degraded to provide comfort. This is followed by the analysis of HVAC systems as complex energy conversion devices where energy carriers are transformed into useful heat and coolth, and finally, the impact of HVAC energy consumption on energy resources is discussed.     

Analysis of agricultural sustainability: A review of exergy methodologies and their application in OECD countries

This article proposed the combination of cumulative exergy extraction from the natural environment and extended exergy analysis to analyse international environmental performance in agricultural production. The unified approach allowed the cumulative analysis of total extraction of all types of resources and services from the ecosystem in agriculture. The analysis, therefore, enabled a more accurate comparison of the environmental performance of different countries or systems based on different indicators of sustainability. The application was conducted for 29 OECD countries for the years from 1990 to 2003 with some important findings. First, the organic contents in topsoil, feed and total water withdrawal were the three types of resources that agricultural production extracted most from the environment. Second, during the 14 years surveyed, the efficiency of using exergy in the livestock sector was much lower than the efficiency in the crop sector. Third, the environmental loading of economic investment had increased slightly, implying a minor increase in the pressure on the environment overtime. In addition, the empirical study on OECD countries confirmed that rankings varied widely based on different indicators. The empirical results gave some evidence to support the use of non‐renewability yield ratio, firstly defined in this paper, because the rankings based on this indicator was more consistent with many other indicators. Copyright © 2010 John Wiley & Sons, Ltd.     

The sustainability indicators of power production systems

One of the most important elements of economical and social development is to provide uninterrupted electric energy to consumers. The increasing world population and technological developments rapidly increase the demand on electric energy. In order to meet the increasing demand for sustainable development, it is necessary to use the consumable resources of the world in the most productive manner and minimum level and to keep its negative effects on human health and environment in the lowest level as much as possible. In this study, alignment of hydrogen fuel cells, hydroelectric, wind, solar and geothermal sourced electric energy systems, in addition to fossil fueled coal, natural gas and nuclear power plants, in respect to sustainability parameters such as CO₂ emission, land use, energy output, fresh water consumption and environmental and social effects is researched. Consequently, it has been determined that the wind and nuclear energy power plants have the highest sustainability indicators. The fuel cells that use hydrogen obtained by using coal and natural gas are determined as the most disadvantageous transformation technologies in respect to sustainability. This study contains an alignment related to today's technologies. Using of renewable energy resources especially in production of hydrogen, output increases to be ensured with nanotechnology applications in photovoltaic systems may change this alignment.     

机场航站楼暖通空调系统的节能运行

以北京首都机场2号航站楼为例,详细介绍了航站楼内暖通空调系统运行概况,并从暖通空调设备的运行管理和系统节能改造等方面详细阐述了大型公建中如何有效降低供冷、供暖季能耗的一些节能做法和措施。其中包括制定空调设备的节能运行控制策略,分时分阶段按需供能,采用末端空调设备的运行与航班联动,分层分系统开启空调设备和优化气流组织;通过更换节能照明灯具,有效降低区域冷负荷;改造优化原有风系统、水系统路由满足局部供能需求。这些节能措施弥补了设计方案的不足,取得了很好的节能效果。     

中央空调系统循环水腐蚀分析与水处理对策

阐述了中央空调水循环系统中污垢,腐蚀等造成的影响与影响机理,介绍了循环水处理的具体对策。     

Transient pattern analysis for fault detection and diagnosis of HVAC systems

Modern building HVAC systems are complex and consist of a large number of interconnected sub-systems and components. In the event of a fault, it becomes very difficult for the operator to locate and isolate the faulty component in such large systems using conventional fault detection methods. In this study, transient pattern analysis is explored as a tool for fault detection and diagnosis of an HVAC system. Several tests involving different fault replications were conducted in an environmental chamber test facility. The results show that the evolution of fault residuals forms clear and distinct patterns that can be used to isolate faults. It was found that the time needed to reach steady state for a typical building HVAC system is at least 50–60 min. This means incorrect diagnosis of faults can happen during online monitoring if the transient pattern responses are not considered in the fault detection and diagnosis analysis.     

Environmental and sustainability aspects of hydrogen and fuel cell systems

Discussed in this paper are current environmental problems, potential solutions to these problems, possible future hydrogen energy‐utilization patterns for better environment and sustainable development through life cycle assessment (LCA), and how the principles of thermodynamics via exergy can be beneficially used to evaluate hydrogen and fuel cell systems and their role in sustainable development. Throughout the paper current and future perspectives of hydrogen and fuel cell systems based on exergetic, LCA and sustainability aspects development are considered. The results will likely be useful to scientists, researchers and engineers as well as policy and decision makers. Two case studies on the LCA aspects of hydrogen and fuel cell systems are presented to highlight the importance of the hydrogen and fuel cell systems and show that these can help achieve better environment and sustainability. Copyright © 2006 John Wiley & Sons, Ltd.     

An experimental tool for research and educational applications on HVAC systems

This paper describes an experimental tool elaborated at the building sciences laboratory (LASH/DGCB). The objective of this tool is to develop control strategies for heating, cooling and ventilation, and test them on heating, ventilating and air conditioning equipment. The tests are conducted in a large room of the laboratory equipped with a double-flow ventilation system and a global control/data acquisition system. The tool is used for research and some experiments are led by engineering students. It enables the identification of optimal parameters for each developed control strategy, in order to reach good thermal comfort, acceptable indoor air quality and good stability of actuators at the least energy cost. In this paper we present an example of global control strategy for heating and cooling periods based on interior temperature control (fuzzy regulator). This strategy includes an indoor air quality controller (proportional integral or fuzzy regulator) based on indoor CO₂ level control. A measurements campaign during an occupied period is shown with an overview of the actuators’ behaviour. This tool also highlights the key role of advanced control techniques to manage heating, cooling and ventilation systems.     

Key strategies of hydrogen energy systems for sustainability

Here we conduct a parametric study to investigate the effects of hydrogen energy utilization on the global stability and sustainability. In this regard, in order to derive the hydrogen energy based sustainability ratio, the green energy based sustainability ratio, as developed earlier, is modified to come up with a new parameter, namely “hydrogen energy utilization ratio through non-fossil fuels”. We take actual historical data from key sources to determine the role of hydrogen energy for sustainability and make some future projections as the road map for hydrogen economy. In addition, an illustrative example on the hydrogen energy based sustainability ratio is presented by considering green energy sources such as solar, wind, hydro and nuclear to make hydrogen economy more environmentally benign and sustainable. It is found that hydrogen energy based global stability and sustainability ratios increase with the rise of hydrogen energy utilization ratio. The best results for hydrogen energy based sustainability ratio are obtained for the highest hydrogen energy impact ratios between 73.33% and 100%. In case of 10% of hydrogen energy utilization ratio, hydrogen based sustainability ratios for year 2010 are, respectively, determined to be 0.21%, 0.23%, 0.25%, 0.27% and 0.29% in 2.92% of hydrogen based global stability ratio by depending on the hydrogen energy impact ratios (=73.33%$=73.33\%$, 80%, 86.67%, 93.33% and 100%). In case of 20% of hydrogen energy utilization ratio, the hydrogen energy based sustainability ratios are found to be 1.09%, 1.19%, 1.28%, 1.38% and 1.48% in 7.41%, respectively. The results are really encouraging in a way that hydrogen economy appears to be one of the most significant players for better sustainability.