Buildings In Zones Research Articles

Simulation of variable refrigerant flow air conditioning system in heating mode combined with outdoor air processing unit

Variable refrigerant flow (VRF) air conditioning system has become attractive due to better energy performances than traditional air conditioning systems. However, the shortcoming of no outdoor air (OA) intake has not been solved thoroughly. A new VRF and outdoor air processing unit combined air conditioning system is proposed and simulated. The first obstacle is that there is no well-known simulation tool for VRF unit in heating mode. A VRF model of condenser-number independence is developed and validated first. The combined system is modeled by integrating the individual sub-system or component models into a complete system. The average error of the developed model to predict heating capacity, input power and COP are 7.87%, 12.45% and 6.19% respectively. Finally the combined system is simulated under conditions of the same and different set-points of the air conditioning zones. The combined system could maintain all the zones at their specific set-points within small errors no matter the set-points are the same or different. Moreover, indoor air quality can be ensured. The demand of one air conditioning system possessing independent units serving separate zones in the same building could be met by the combined system.

Стаціальний розподіл самок кровосисних комарів у Солом’янському районі Києва

From the epidemiological viewpoint the greatest threat to human health is represented by female mosquitoes in the hematophagous stage. Contact with these bloodsucking insects occurs most frequently in their places of diurnal concentration. The main daytime habitats of mosquitoes in urban areas are recreational areas, especially near water – forests, parks, botanical gardens, cemeteries, green zones in residential areas, residential buildings and buildings with livestock, basements and cellars. In the context of global warming and extreme high summer temperatures a tendency has been observed for mosquitoes to make increasing use of residential premises and outbuildings as a daytime habitat. In the Solomianskyi district of Kiev a six-year monitoring programme of mosquitoes’ diurnal habitat distribution was conducted. It showed that the majority of female mosquitoes which attacked humans (60%) were concentrated in areas of recreation and outdoors in residential areas. Simultaneously a significant number of mosquitoes was found to use as their daytime habitat places where they were in close proximity to humans – in domestic outbuildings (sheds under various uses), basements and cellars. The lion’s share of these mosquitoes was represented by Anopheles maculipennis (25%) and Culex pipiens (7,6%). At the same time a significant number of representatives of the genera Ochlerotatus (O. cantans, O. sticticus, O. cataphylla) and Aedes (Ae. v. vexans) were also recorded using residential premises as their daytime habitat on a scale which had not been previously observed for these species of mosquito. It is possible that female mosquitoes fly into livestock buildings at twilight because they are attracted by electric light and ammonia vapors. However, these factors are almost absent in basements and cellars. It remains to be noted that mosquitoes use basements and cellars as a daytime habitat at periods of hightemperatures and low humidity in the city. To test this assumption the distribution of mosquitoes was analysed during the warm season in 2010 in Solomyanskyi district with measurement of temperature at the locations of collection. It turned out that the air temperature in the sheds was 2–4 °C lower than outside in the shade, in the basements lower by 4–11 °C, and in the cellars lower by 4–12 °C. Comparison of the temperature in the daytime habitats and number of mosquitoes found there showed a direct relation between the outdoor temperature and the number of mosquitoes in the daytime habitat on the premises. The data indicate that there is a tendency for the number of synanthropic blood-sucking mosquito species to increase owing to the occupation of domestic premises as a daytime habitat by those species of mosquitoes for which this phenomenon was not typical earlier. If global warming and the current trend to increase in summer temperatures persist, this can cause a deterioration of the epidemiological situation in the megalopolis.

Analysis of Electric Energy Consumption Patterns: A Case Study of a Real Life Office Building

Electric energy consumption shares a great portion of commercial building energy. Electric energy saving is essential to reduce total energy consumption in commercial buildings. To draw energy saving methods, it is necessary to monitor real energy consumption patterns and analyze the results. We monitor the lighting and non-lighting energy consumption of eleven zones in a real working office building every fifteen minutes during eleven months. We observe and analyze the monthly and daily energy consumption patterns of all zones and draw several feasible energy saving methods. Moreover, the lighting and occupancy are monitored simultaneously in detail to investigate the unnecessary energy consumption. It shows the possibility of a great amount of energy saving. Because we analyze the energy consumption patterns in all zones, the drawn energy saving methods are applicable to the current building with some added infrastructure and expandable to other similar office buildings. Our result is expected to contribute to reducing the energy consumption in buildings.

Inverse modeling of simplified hygrothermal building models to predict and characterize indoor climates

Computational research on monumental buildings yields three problems regarding currently used detailed building models: tedious modeling, relatively long simulation run times, difficulties to characterize a building by its model parameters. A new simplified hygrothermal building model in state space form is presented with an inverse modeling technique to identify its parameters. Based on a literature review, 10 thermal models and 5 hygric models were developed. An optimization routine was used to fit the output of the models to long term hourly measurements of a typical monumental building zone and to a fictive indoor climate that was simulated by a validated simulation tool. The model performance was assessed by three criteria and the best models were selected. The validation of the selected thermal and hygric models consisted of fitting the models' output to indoor climate measurements of four monumental building zones, a residual analysis and parameter analysis. The results show that the simplified hygrothermal model is capable of reproducing most indoor climates accurately. Moreover, the state space model results in fast simulations: 100 years with hourly samples was simulated in 0.45 s on an ordinary computer (i5-processor). Characterization and validation of the parameter values are challenging and requires additional measurements and research.

Flow and mixed convection heat transfer in buoyant jets from floor registers

As models of energy movement in buildings and tools for load calculation become more refined, more accurate descriptions of fluid mechanics and heat transfer in perimeter zones are needed. New construction which includes glass curtain walls around perimeter zones presents a unique challenge. A mixed convection regime may be present which precludes the use of existing models developed for purely forced convection. In order to study flow and heat transfer in these situations, environmental conditions are precisely controlled in a test room to simulate situations that may occur in perimeter zones of buildings with glass curtain walls. Diffuser jets issuing from floor registers were shown to exhibit behavior not accounted for in existing heat transfer models. Results show that the movement of the jet issuing from floor registers is highly dependent on the mixed convection parameter Gr/Re2 or Richardson number. Models are put forth to predict the movement of these jets, and the resulting heat transfer at walls or windows. When the effect of buoyancy forces is accounted for, models conform to a form used previously for turbulent forced convection. Three distinct flow regimes are identified and prescriptions are put forth for ensuring proper thermal control and accurate energy models.

Intermediate complexity model for Model Predictive Control of Integrated Room Automation

Integrated Room Automation (IRA) for office buildings deals with the automated control of blinds, electric lighting, heating, cooling, and ventilation of a room or building zone. Model Predictive Control (MPC) presents a promising method to achieve energy savings thanks to improved control. This paper presents the development and validation of an intermediate complexity, integrated building and building equipment model suitable for application within MPC. A resistance-capacitance (RC) modeling approach was chosen. The result is a 12th order multiple-input-multiple-output bilinear model for the coupled simulation of the thermal, light and air quality dynamics of a single room. It includes the subsystems mechanical and natural ventilation, radiator and floor heating, cooling ceiling and thermally activated building system. For computational efficiency and compatibility with MPC, several approximations and a reduction of complexity were necessary. The resulting behaviors were validated against detailed building and system simulations. The model was found to deliver accurate and reliable results. It can be flexibly configured to represent typical building types and variants of technical systems. Furthermore, it is sufficiently efficient to support large-scale sensitivity studies. Finally, the model is ready for adaptation and integration into commercial algorithms for the control of real buildings.

Multizone airflow models for calculating infiltration rates in commercial reference buildings

Sixteen reference building models were created in the multizone airflow and contaminant transport program CONTAM in order to support physically based airflow calculations, as well as indoor air quality analyses, that are not possible using the existing EnergyPlus input files of these buildings. The EnergyPlus models were created for assessing new technologies and supporting the development of energy codes in pursuing building energy efficiency improvements. These models employed an oversimplified approach to infiltration in which infiltration rates were input as constant values. A number of additional inputs had to be defined for the CONTAM models to realistically account for airflow, including the addition of several building zones. Annual airflow simulations were performed in CONTAM for six of the sixteen reference buildings. There are clear relationships between the infiltration rates calculated by CONTAM and weather, which are not exhibited in the EnergyPlus results. In addition, the building envelope airtightness values assumed in either approach have a major impact on calculated infiltration rates. The results of this study provide a baseline for subsequent use of these models to investigate design approaches and technologies that are intended to reduce building energy consumption, improve indoor air quality, or both.

Effects and Side Effects of Measures to Attract Firms – A Micro-Simulation Study of Firm Location Choice

This paper investigates the effects of different possible options for cantonal and municipal authorities' intent on attracting firms: improvements in transport infrastructure, designation of new building zones, and tax reductions. These options have been tested by simulating the location decisions of existing firms. The parameters for these simulations have been estimated with a discrete choice model using data from the commercial registers of the Canton of St. Gallen and the two Appenzell cantons (Innerrhoden and Ausserrhoden) covering the years 1991 to 2006. The aim of this paper is not only to show the effects, but also to detect potential negative side effects. The simulation results show that tax reductions have an unparalleled large effect, meaning positive effects in the municipalities concerned as well as negative side effects in adjacent municipalities. Generally, effects are more intense in regions with a large number of firms already present. Interestingly, due to large positive effects in a specific region, negative side effects can also be identified over long distances in other regions. Cities and towns are especially affected by these long-distance effects.

A Study on Objects Information Compatibility between BIM Softwares for Building Thermal Load Analysis

The objective of this study is to investigate the file exchange compatibility of BIM based building energy simulation tools, especially focusing on various irregular building geometry shapes. As a base building modeling software, AUTOCAD Revit was selected and various building geometry shapes were created using Revit, such as curved and pitched walls, roofs, slabs with various air-conditioning zones. And these various shaped building zones were imported to ECOTECT, IES/VE and Openstudio for EnergyPlus, which are professional building energy simulation tools. Through this create-import process, the deformation of building shapes, change of zone volume, and compatibility to each simulation engine were investigated and analyzed.

Islands in a European mountain river: Linkages with large wood deposition, flood flows and plant diversity

Vegetated islands are characteristic landforms of braided mountain rivers. Long-term observations and recent morphological and botanical surveys conducted in the gravel-bed Czarny Dunajec, Polish Carpathians, were used to determine the processes and patterns governing initiation and development of islands and their floristic complexity. Moreover, dendrochronologically estimated years of island inception were compared with the timing and magnitude of flood flows in the period 1970–2011 to infer about controls on the formation and persistence of islands in the river. In the high-energy, braided river, islands originate as a result of deposition of large vegetative particles, mostly large wood, on gravel bars and the associated vegetative regeneration of living wood or the growth of seedlings and saplings in the shelter of wood accumulations. Tree-ring dating of the largest trees growing in particular zones of building and established islands indicated a predominant upstream island growth in the river. It results from repeated accumulation of living wood on the head of islands and its subsequent regeneration and contrasts with the progressive downstream growth of islands in the rivers supplied with large, stable logs of the tree species without the capability to re-sprout. The lack of islands from the years 1982–1996 most likely reflects the removal of relatively young islands by two major floods in the 1990s which were, however, unable to destroy older and larger islands. After 1997 the occurrence of low to moderate floods facilitated the formation and persistence of islands. The plant inventory demonstrated that species richness increased non-linearly with the increasing age, area and shoreline length of islands. Islands supported more plant species than the riparian forest and attained comparable species richness at an early stage of development. Fast developing, dynamic and supporting rich plant communities, islands contribute highly to the overall floristic complexity of the river corridor and their re-establishment should be viewed as an important factor in the restoration of hydromorphologically degraded mountain rivers.

Simulation of annual electric lighting demand using various occupancy profiles

This paper describes an investigation of the effect on electric lighting demand of applying occupancy models of various resolution to climate-based daylight modelling. The lighting demand was evaluated for a building zone with the occupant always present, with occupancy corresponding to absence factors, based on an estimated annual mean occupancy, based on estimated 1-hour mean occupancy, and based on 2-min occupancy intervals. The results showed little difference in the annual electric lighting demand when the same occupancy profile was used every day, as opposed to when profiles were used where occupancy varied every day. Furthermore, the results showed that annual electric lighting demand was evaluated slightly conservatively when a mean absence factor was applied as opposed to using dynamic occupancy profiles.

Importance of occupancy information for building climate control

This paper investigates the potential of using occupancy information to realize a more energy efficient building climate control. The study focuses on Swiss office buildings equipped with Integrated Room Automation (IRA), i.e. the integrated control of Heating, Ventilation, Air Conditioning (HVAC) as well as lighting and blind positioning of a building zone or room. To evaluate the energy savings potential, different types of occupancy information are used in a Model Predictive Control (MPC) framework, which is well-suited for this study due to its ability to readily include occupancy information in the control.An MPC controller, which controls the building based on a standard fixed occupancy schedule, is used as a benchmark. The energy use of this benchmark is compared with three other control strategies: first, the same MPC controller which uses the same schedule for control as the benchmark, but turns off the lighting in case of (an instantaneous measurement of) vacancy; second, the same MPC controller which uses the same schedule as the benchmark for control, but turns off lighting and ventilation in case of (an instantaneous measurement of) vacancy; and third, the same MPC controller as the benchmark but using a perfect prediction about the upcoming occupancy.This comparison is carried out for different buildings, HVAC systems, seasons and occupancy patterns in order to determine their influence on the energy savings potential.

The hydraulics of exchange flow between adjacent confined building zones

Buoyancy driven flow between two finite zones containing fluid of slightly different density is investigated. The two zones are connected through a common rectangular doorway spanning the channel width so that a two-layer exchange flow develops once the barrier is removed. In the zone that initially contained dense fluid, a buoyant plume of light fluid mixes with the dense fluid leading, over time, to the development of non-trivial ambient density stratification. Meanwhile, dense fluid flows as a gravity current into the zone that initially contained light fluid. This gravity current reflects from the end wall and propagates back toward the opening in the form of an internal bore. When the bore reaches the opening the dynamics of the exchange flow (and consequently the source conditions of the buoyant plume) are substantially altered. Such dynamics are modeled using elements of gravity current, internal bore and plume theory. The flow dynamics of the two zones are linked using two-layer exchange flow theory whereby a maximal exchange flow rate is prescribed only before the bore reaches the opening. The velocity and density jump across the first front decrease substantially once the exchange flow becomes sub-maximal. Depending on the geometrical parameters, the terminal elevation of the first front may lie above, at or below the top of the opening; here, we focus on the former scenario. Experiments have been carried out to validate the model. The comparison between theory and experiment plus the application of the research to architectural fluid mechanics is discussed.

Experimental Analysis of the Infrared Thermography for the Thermal Characterization of a Building Envelope

nfrared thermography is being used to identify defects maps of the building envelope, based on the most suitable local thermal parameter. In spite of the fact that the TOBUS method [1] and the multivariate design method [2] consider several complicated building renovations, their applications on energy performance improvement are mainly inadequate [3]. In this research, the developed experimental and theoretical studies show, on the one hand, the thermal characterization (temperature distribution, heat losses and efficiency) of a full-scale building envelope. On the other hand, the applicability and accuracy of this optic technique for the thermal characterization of the building zone with complex geometry is discussed in order to validate results obtained for the thermal characterization.

Numerical analysis of the performance of a venturi-shaped roof for natural ventilation: Influence of building width

A numerical analysis with Computational Fluid Dynamics (CFD) is performed to investigate the influence of building width on the performance of a venturi-shaped roof (called Ventec roof) for natural ventilation. The specific roof configuration is intended to create an underpressure in the narrowest roof section (contraction) which can be used to partly or completely drive the natural ventilation of the building zones. In previous studies, the influence of the roof configuration on its performance was analysed in detail, however these studies were all performed for a fixed building geometry, i.e. a tower building with floor plan 20×20m² and a height of 50m. It is important to analyse the performance of the Ventec roof for different building widths. Therefore, the present paper presents CFD simulations for building (and roof) widths of 20, 40, 80, 120 and 160m. The 3D steady Reynolds-averaged Navier–Stokes (RANS) approach with the Renormalization Group (RNG) k–ε model is used. The simulations are based on grid-sensitivity analysis and on validation by comparison with wind tunnel experiments. The simulations show that the aerodynamic performance of the roof in terms of the underpressure in the contraction improves with 31% when the building width is increased from 20m to 40m, while further increasing the building width only provides relatively small additional improvements. The increased performance with increasing building width is attributed to the larger overpressure upstream of the building and to the larger underpressure and larger size (height) of the wake behind the building.

Design of the drop-off-pick-up zones in buildings: the case of private transportation at the female university of Riyadh

The design of the building that is going to hold the operations to pick-up the female students by private vehicles when classes are finished is presented for an Arabian university. The premises have been designed to maximize the capacity of the parking arrangement and maintain a constant and quick flow of vehicles within complex sociological constraints. Architects, traffic engineers and simulation specialists have concurrently designed a building that has to give service to 4500 vehicles within 1 h. The solution is based on three pillars: just-in-time, to simplify the tasks and laminate the demand so the flow rates are evenly distributed; information technologies, to maximize the probability of the students being ready when the corresponding vehicle arrives; and discrete-event simulation to abstract the complex procedures in a realistic, dynamic way and to visualize the movement so as to transmit credibility on the selected design to all the parties involved.

Sensor Calibration and Diagnostics Under Parameter Uncertainty: A Smart Building Application

One key problem with control systems in general, and control systems for buildings in particular, is that mis-calibration of sensors/actuators is commonplace and causes significant problems, such as suboptimal performance and diagnostics false alarms. This paper describes a methodology for calibrating sensors that can reduce these problems. We show how we can take sensor outputs and continuously calibrate them by applying expectation-maximization (EM) learning and recent gossip-based algorithms. We apply our approach to the domain of sustainable buildings, in particular temperature sensors in shared zones in a large commercial building. We empirically show that our approach can correctly either diagnose faults that render sensors impossible to calibrate, or can perform appropriate calibration.

Dynamic thermal circuit modelling with distribution of internal solar radiation on varying façade orientations

This paper aims at introducing an improved methodology for the dynamic modelling of buildings by the thermal networks method. This methodology employs, as a tool, the commonly used ASHRAE clear sky model to allow for the calculation of the external façade radiation and the distribution of the penetrating solar flux on the internal surface-nodes of the zone. The zone considered has an entirely glazed façade with a varying type of glazing and its enclosure is a rectangle parallelipipedic. The incident solar radiation is determined for building surface azimuths ranging from east to west in 45° step increments. The mathematical formulation of this solar-angle dependent lumped capacitance thermal model is based on the nodal approach and is updated in 15min time increments. The proposed methodology provides more insight to help understand the impact of opaque and glazed façade orientations and layer-formation on energy consumption. Results from annual energy performance calculations vs glazed-façade orientation, for various glazing systems, are given for a building zone location in the Mediterranean region. Depending on the building façade orientation and climatic conditions, proper selection of the type of glazing can reduce the annual building energy consumption.

Evaluation of Sub-Zonal Airflow Models for the Prediction of Local Interior Boundary Conditions – Natural and Forced Convection Cases

Currently, researchers are striving to advance the possibilities to calculate the integrated phenomena of heat, air and moisture flows in buildings, with specific focus on the interactions between the building zones and building components. This paper presents an investigation of the capability and applicability of the sub-zonal airflow model to predict the local indoor environmental conditions, as well as the local surface transfer coefficients near building components. Two test cases were analyzed for, respectively, natural and forced convection in a room. The simulation results predicted from the sub-zonal airflow models are compared to experimental data and numerical computational fluid dynamics (CFD) results. The study shows that sub-zonal models combined with an appropriate surface transfer coefficient model are able to give reliable predictions of the local indoor environmental conditions and surface transfer coefficients near the building component for the analyzed cases. The relatively short computation time and flexibility of the sub-zonal model makes the application attractive for transient simulation of heat, air and moisture transport in buildings. However, the availability of appropriate reference conditions, for example experimental or numerical results, is a prerequisite for the development of a reliable sub-zonal model.

Use of model predictive control and weather forecasts for energy efficient building climate control

This paper presents an investigation of how Model Predictive Control (MPC) and weather predictions can increase the energy efficiency in Integrated Room Automation (IRA) while respecting occupant comfort. IRA deals with the simultaneous control of heating, ventilation and air conditioning (HVAC) as well as blind positioning and electric lighting of a building zone such that the room temperature as well as CO 2 and luminance levels stay within given comfort ranges. MPC is an advanced control technique which, when applied to buildings, employs a model of the building dynamics and solves an optimization problem to determine the optimal control inputs. In this paper it is reported on the development and analysis of a Stochastic Model Predictive Control (SMPC) strategy for building climate control that takes into account the uncertainty due to the use of weather predictions. As first step the potential of MPC was assessed by means of a large-scale factorial simulation study that considered different types of buildings and HVAC systems at four representative European sites. Then for selected representative cases the control performance of SMPC, the impact of the accuracy of weather predictions, as well as the tunability of SMPC were investigated. The findings suggest that SMPC outperforms current control practice.