Interactive Graphical Representation for Collaborative 3D Virtual Worlds

Abstract:  Three-dimensional (3D) virtual worlds have the potential to make a major impact on global design teams by providing an online place that supports distant design activities without designers being physically present. To accommodate designing in 3D virtual worlds for the architecture, engineering, and construction (AEC) domain, there is an urgent need for the development of a representation system applicable in conceptual design and multi-disciplinary design. Extended from Qualitative Archi Bond Graphs (QABGs) that are developed as qualitative unified representations for buildings, this article presents and demonstrates an interactive graphical representation for collaborative design in 3D virtual worlds. The representation supports multiple design representation subsystems and their interactions that enable designers to better facilitate design collaboration in 3D virtual worlds .     

A methodology for modelling energy-related human behaviour: Application to window opening behaviour in residential buildings

An energy simulation of a building is a mathematical representation of its physical behaviour considering all the thermal, lighting, acoustics aspects. However, a simulation cannot precisely replicate a real construction because all the simulations are based on a number of key assumptions that affect the results accuracy. Above all, the real energy performance can be affected by the actual behaviour of the building occupants. Thus, there are great benefits to be derived from improving models that simulate the behaviour of human beings within the context of engineered complex systems. The occupant behaviour related to the building control potentialities is a very complex process that has been studied only in the last years with some focuses related to natural ventilation (window opening behaviour), space heating energy demand (in particular the adjustments in the temperature set-point) and natural light (focusing on window blinds adjustments). In this paper, a methodology is presented to model the user behaviour in the context of real energy use and applied to a case study. The methodology, based on a medium/long-term monitoring, is aimed at shifting towards a probabilistic approach for modelling the human behaviour related to the control of indoor environment. The procedure is applied at models of occupants’ interactions with windows (opening and closing behaviour). Models of occupants’ window opening behaviour were inferred based on measurements and implemented in a simulation program. Simulation results were given as probability distributions of energy consumption and indoor environmental quality depending on user behaviour.     

Occupant behaviour in energy efficient dwellings: evidence of a rebound effect

The energy required for space heating has been significantly reduced in recent decades by making use of insulation and more efficient heating and ventilation systems. Even so, wide variations in energy consumption are still observed between similar dwellings and between actual and predicted levels. It is thought that these variations stem from differences in occupant behaviour, the structural quality of the building, and a rebound effect. This paper statistically examines differences in occupant behaviour in relation to the building characteristics of the housing stock in the Netherlands and explores the possible existence of a rebound effect on the consumption of energy for space heating. Rebound effect can be defined as the increase on energy consumption in services for which improvements in energy efficiency reduce the costs. We found that although energy consumption is lower in energy efficient dwellings, analysis of the behaviour variables indicates their occupants tend to prefer higher indoor temperatures and to ventilate less. This finding might be related to a rebound effect on occupant behaviour. However, the improvement of thermal properties and systems efficiency still lead to a reduction on energy consumption for heating.     

Measuring residential duct efficiency with the short-term coheat test methodology

Assessing the thermal efficiency of a forced-air distribution system is difficult, in large part because of interactions between energy loss mechanisms and other building characteristics. This paper describes short-term coheating, a method of measuring the thermal efficiency of residential heating and cooling distribution systems in situ, and presents the results of a series of studies that utilized the short-term coheat methodology. Short-term coheat tests were conducted in 53 residential buildings including both site-built and manufactured housing. The magnitude of the distribution efficiency, defined as the ratio of the energy required to heat the building if there were no duct losses to the actual heating energy required, ranged from less than 50% for homes with disconnected ducts to more than 90% for well sealed and insulated systems. Duct retrofits were also performed at 20 of the test sites and, following the retrofits, on average, the homes required 16–17% less heating energy. These results show that residential distribution system losses can be responsible for substantial energy loss and that duct retrofits are a viable energy conservation strategy for homes with distribution systems located outside of the conditioned space.     

Simulation and visualization of energy-related occupant behavior in office buildings

In current building performance simulation programs, occupant presence and interactions with building systems are over-simplified and less indicative of real world scenarios, contributing to the discrepancies between simulated and actual energy use in buildings. Simulation results are normally presented using various types of charts. However, using those charts, it is difficult to visualize and communicate the importance of occupants’ behavior to building energy performance. This study introduced a new approach to simulating and visualizing energy-related occupant behavior in office buildings. First, the Occupancy Simulator was used to simulate the occupant presence and movement and generate occupant schedules for each space as well as for each occupant. Then an occupant behavior functional mockup unit (obFMU) was used to model occupant behavior and analyze their impact on building energy use through co-simulation with EnergyPlus. Finally, an agent-based model built upon AnyLogic was applied to visualize the simulation results of the occupant movement and interactions with building systems, as well as the related energy performance. A case study using a small office building in Miami, FL was presented to demonstrate the process and application of the Occupancy Simulator, the obFMU and EnergyPlus, and the AnyLogic module in simulation and visualization of energy-related occupant behaviors in office buildings. The presented approach provides a new detailed and visual way for policy makers, architects, engineers and building operators to better understand occupant energy behavior and their impact on energy use in buildings, which can improve the design and operation of low energy buildings.     

Investigation and modelling of the centralized solar domestic hot water system in residential buildings

The solar domestic hot water (DHW) system is applied as a building energy saving technique. The centralized system, which is considered to provide both energy efficiency by exploiting solar energy and high-level services to the customers as the occupants could have access to the hot water at any time during the day, is widely used among the various forms of solar DHW systems. The real performance of a centralized solar DHW system is measured, based on which a model describing the solar energy collection, water supply, and terminal water use is built. The simulation reveals that the actual energy performance of the centralized DHW system is closely related with the occupant behaviour, i.e., the water use patterns of the occupants residing in a building. This study concluded that whether the DHW system is energy efficient or not could not be evaluated without considering the water use patterns of the occupants.     

Energy savings in a building using regenerative evaporative cooling

This paper explores the potential of reducing the annual energy consumption of a central air-conditioned building through advanced evaporative cooling systems. The building considered is a typical three floor library building of a University. The regenerative evaporative cooling technology is coupled with the liquid cooled water chiller system to accomplish the energy conservation objective. Comparisons of the regenerative evaporative cooling are made with simple evaporative cooling to bring out the importance such a system. The well-known building simulation software, TRNSYS is used to carry out the heat load calculations and the dynamic simulations of the building. Annual energy consumptions of different components of the air-conditioning system are estimated for the existing water chiller system as well as for both coupled evaporative cooling systems (simple and regenerative). The annual energy consumptions, the indoor temperature, the relative humidity and the thermal comfort index ‘PMV’ are compared for all the three different air-conditioning systems. The coupling of direct and regenerative evaporative cooling technologies with water chiller system has shown, respectively, 12.09% and 15.69% savings in annual energy consumption of the building, while maintaining PMV between ?1 and +1 for most of the hours in the year.     

Primary energy implications of ventilation heat recovery in residential buildings

In this study, we analyze the impact of ventilation heat recovery (VHR) on the operation primary energy use in residential buildings. We calculate the operation primary energy use of a case-study apartment building built to conventional and passive house standard, both with and without VHR, and using different end-use heating systems including electric resistance heating, bedrock heat pump and district heating based on combined heat and power (CHP) production. VHR increases the electrical energy used for ventilation and reduces the heat energy used for space heating. Significantly greater primary energy savings is achieved when VHR is used in resistance heated buildings than in district heated buildings. For district heated buildings the primary energy savings are small. VHR systems can give substantial final energy reduction, but the primary energy benefit depends strongly on the type of heat supply system, and also on the amount of electricity used for VHR and the airtightness of buildings. This study shows the importance of considering the interactions between heat supply systems and VHR systems to reduce primary energy use in buildings.     

Influence of building parameters and HVAC systems coupling on building energy performance

The performance of different HVAC systems varies when coupled with different buildings. This paper examines the relationship between building heating and cooling load and subsequent energy consumption with different HVAC systems. Two common HVAC systems in use throughout the UK office building stock, variable air volume (VAV) system and fan coil (FC) with dedicated outside air system, have been coupled with a typical narrow plan office building with and without daylight control and for both cellular and open plan.The results presented in this paper clearly indicate that it is not possible to form a reliable judgment about building energy performance based only on building heating and cooling loads. For the two investigated systems, variable air volume system and fan coil with dedicated outside air system, the difference between system demand and building demand varied from over −40% to almost +30% for cooling and between −20% and +15% for heating. If a heat recovery unit is used, the difference in heating performance is even greater, rising to −70%.     

Trade-off between environmental and economic objectives in the optimization of multi-energy systems

An increase in the energy and environmental performance of building system can be found in a design that allows the operators to choose between multiple energy sources. Such a system can be referred to as multi-energy system and recently a strong interest was put in this topic at both district and building levels. Since multi-energy systems use non conventional aggregation of energy sources, new energy converters, and unusual system layouts, it is of the foremost importance to provide modelling and optimization procedures for those systems. In this paper, some objective functions based on a set of economic and environmental criteria are defined and used to perform the system optimization. The relations between the outcomes of the optimizations are then analyzed on a case study as a function of the customer, the energy costs, and the pollutants emissions showing that there is generally a trade-off between environmental and economic objectives.     

日本的建筑节能概念与政策

介绍了日本面对能源消耗持续增长的形势所制定的节能目标、建筑节能判定标准和节能措施，认为我国应积极引入先进的节能观念和方法，制定科学有效的建筑能效评价体系。     

Comparison of energy efficiency between variable refrigerant flow systems and ground source heat pump systems

With the current movement towards net zero energy buildings, many technologies are promoted with emphasis on their superior energy efficiency. The variable refrigerant flow (VRF) and ground source heat pump (GSHP) systems are probably the most competitive technologies among these. However, there are few studies reporting the energy efficiency of VRF systems compared with GSHP systems. In this article, a preliminary comparison of energy efficiency between the air-source VRF and GSHP systems is presented. The computer simulation results show that GSHP system is more energy efficient than the air-source VRF system for conditioning a small office building in two selected US climates. In general, GSHP system is more energy efficient than the air-source VRV system, especially when the building has significant heating loads. For buildings with less heating loads, the GSHP system could still perform better than the air-source VRF system in terms of energy efficiency, but the resulting energy savings may be marginal.     

Estimating static heat flows in buildings for energy allocation systems

An energy cost allocation system records the energy consumption of a building and divides the overall energy costs between the flats. Because the indoor temperatures of rooms are usually not equal, static heat flows between flats cannot be avoided. Hence, in order to ensure fair energy costs per flat the system should be able to determine the static heat flows, preferably without utilising in situ measurements. This paper presents a new method for estimating static heat flows between neighbouring rooms. The approach is theoretical, focusing only on heat transfer issues. Energy cost allocation is not considered.The approach is based on the parametric model describing thermal behaviour of an occupied space. The model is created for each room of a building. Parameter values are identified using real-time measurements collected by a building automation system from each room and its environment. The tuning of parameters takes a few days using a 15-min sampling time. A prerequisite for successful system identification is the overall control of the room temperatures. All test runs are performed in a simulated office hotel using the TRNSYS simulation program. The results are encouraging, but further research is needed, especially in a real building environment.     

The effect of occupancy and building characteristics on energy use for space and water heating in Dutch residential stock

As a consequence of the improved quality of thermal properties of buildings due to energy regulations, overall energy use associated with building characteristics is decreasing, making the role of the occupant more important. Studies have shown that occupant behaviour might play a prominent role in the variation in energy consumption in different households but the extent of such influence is unknown. The impact of the building's thermal characteristics on space heating demand has been well studied. There is however, little work done that incorporates the impact of consumer behaviour. This study aims to gain greater insight into the effect of occupant behaviour on energy consumption for space heating by determining its effect on the variation of energy consumption in dwellings while controlling for building characteristics. The KWR database from the Ministry of Housing in the Netherlands was used. This study showed that occupant characteristics and behaviour significantly affect energy use (4.2%), but building characteristics still determine a large part of the energy use in a dwelling (42%). Further analysis showed that some occupant behaviour is determined by the type of dwelling or HVAC systems and, therefore, the effect of occupant characteristics might be larger than expected, since these determine the type of dwelling.     

An exergy application for analysis of buildings and HVAC systems

The paper presents an extended method for exergy analysis of buildings and Heating Ventilation Air Conditioning (HVAC) systems, according to an energy demand build-up model from the building side to the energy supply side. The HVAC systems comprise a thermal energy emission and control system, a thermal distribution system, an electricity distribution system and an energy conversion system. Energy and exergy that are required by a building and a HVAC system are posed into the external part and classified by different forms of energy carriers. The external part is out of the boundary of the study. The method is illustrated with an office building equipped with low-temperature heating and high-temperature cooling systems situated in the Netherlands. Thermal exergy and thermal energy demands of the building and thermal energy and thermal exergy losses occurring in the HVAC systems are discussed. The building and the HVAC systems to be considered meet standard Dutch energy performance regulations. Nevertheless their overall exergy efficiencies are low in both cases (17.15% and 6.81% subsequently). The exergy analysis also pinpoints that the thermal energy emission and control system and the energy conversion system are the main causes of the exergy inefficiencies in the heating and cooling cases, respectively.     

中国建筑节能市场投融资环境分析

作为中国建筑节能市场的重要组成部分,投融资环境直接影响到建筑节能市场整体的效率和资金流动。目前相关研究较少且多集中在理论的定性分析。因此,本项研究采用定性分析与定量分析相结合的研究方法,运用动态参与者网络分析(DANA)概念建模工具,建立建筑节能市场投融资环境概念模型,剖析投融资环境的现状,结合调查研究识别建筑节能市场投融资环境的主要影响因素,进一步完善投融资环境的分析模型,探讨投融资环境改善和优化的有效途径。研究结果表明,推动中国建筑节能市场投融资环境演变和发展的关键在于:政府相关激励政策的制定、建筑节能运行管理体制的健全、建筑节能服务体系的完善和社会公众对建筑节能认知的提升。     

An optimal control strategy for complex building central chilled water systems for practical and real-time applications

This paper presents an optimal control strategy for online control of central chilled water systems in complex building air-conditioning systems to enhance their energy efficiency. The optimal control strategy is formulated using a systematic approach by considering the system level and subsystem level characteristics and interactions among the overall system. The requirements and constraints of practical applications are also carefully considered during the development of this strategy. This optimal control strategy consists of the model-based performance predictor (i.e., simplified models), cost estimator (i.e., cost function), optimization technique, supervisory strategy and a number of local control strategies. The local control strategies are used to ensure the robust operation and keep track of control settings considering the dynamic characteristics of the local process environment. The performance of this strategy is tested and evaluated in a simulated virtual environment representing the complex central chilling system in a super high-rise building by comparing it with that of other control strategies. The results showed that this strategy is more energy efficient and cost effective than the other strategies for online applications. This strategy is being implemented in the super high-rise building under study for field application and validation.     

Coupling simulation system of annual building energy and microclimate

We have developed a simulation system for a year-round assessment of environmental comfort, energy conservation, and CO₂ emissions in buildings and street blocks where active utilization of sunshine, vegetation and solar energy resources is fully considered. An analysis model has been constructed for handling interactions between highly complex street-block wide solar radiation patterns and building air-conditioning load. As a demonstration case of the present system, coupled solar radiation-thermal load analysis for an eleven-story office building has been performed. By comparing the result of a building located in a city block with a reference case of a self-standing building, the proper arrangement of buildings and spaces such as solar reflectance of building surface may be proposed.