Multi-zone Building Research Articles

Modelling and Characterization of Transparent Building Integrated PV/T Collector

This paper is intended to develop a detailed thermal and electrical model of a transparent backing Building Integrated Photovoltaic/Thermal (TBIPV/T) collector integrated to the roof. This model was used to assess the energy performance of a typical transparent PVT air collector. The energy balance equations were derived for glazing glass, the PV cells, glass back surface of the PV module, air flowing in the duct of TBIPV/T collector and back insulation surface. The energy equations were solved using FORTRAN. A new TRNSYS type was created for the transparent backing PVT system. This type is intended to function with multi-zone building model in TRNSYS, that means thermal interaction between the PV/T collector and the building was taken into account. The effect of different PVT system parameters such as PV cell packing factor, panel cover optical properties on thermal energy production and electricity generation were examined and discussed.

Influence of WWR, WG and Glazing Properties on the Annual Heating and Cooling Energy Demand in Buildings

This investigation presents a detailed analysis in an effort of building energy performance improvement from the aspect of building envelope influence on the annual heating and cooling demand. The aim is to indicate methods of performative intervention for envelope improvement and to offer architects and practitioners useful information for decission-making in the rehabilitation and improvement process of existing office buildings. Building envelope was investigated in order to determine preferable window to wall ratio's (WWR) and window geometry (WG) in the function of indoor daylight quality in offices via numerical simulations in Radiance engine, followed by the assessment of glazing influence on the annual energy demand. A comparative analysis was performed among gathered annual building expenses and simulated heating and cooling demands from the multi-zone thermal model constructed in EnergyPlus engine. Findings from the dynamic simulations indicated the influence of glazing parameters on the annual heating and cooling demand of the multi-zone building model.

Collaborative Energy and Thermal Comfort Management Through Distributed Consensus Algorithms

Buildings with shared spaces such as corporate office buildings, university dorms, etc., are occupied by multiple occupants who typically have different temperature preferences. Attaining a common temperature set-point that is agreeable to all users (occupants) in such a multi-occupant space is a challenging problem. Furthermore, the ideal temperature set-point should optimally trade off the building energy cost with the aggregate discomfort of all the occupants. However, the information on the comfort range (function) is held privately by each occupant. Using occupant-differentiated dynamically-adjusted penalty factor as feedback signals, we propose a distributed solution which ensures that a consensus is attained among all occupants upon convergence, irrespective of their ideal temperature preferences being in coherence or conflicting. Occupants are only assumed to be rational, in that they choose their own temperature set-points so as to minimize their individual energy cost plus discomfort. We establish the convergence of the proposed algorithm to the optimal temperature set-point vector that minimizes the sum of the energy cost and the aggregate discomfort of all occupants in a multizone building. Simulations with realistic parameter settings illustrate validation of our theoretical claims and provide insights on the dynamics of the system with a mobile user population.

Experimental investigation on a complex roof incorporating phase-change material

This article deals with a new configuration of a complex roof using a phase change material (PCM) installed on a dedicated test cell. For the first time and in field conditions, an experimental device using phase change material was set up at Reunion Island, location having a tropical and humid climate. Results show that in the tested configurations and for a non-ventilated air layer, the measured temperatures were on either side of the PCM's melting point. It means that the PCM is able to store thermal energy in the daytime and release it at night. Furthermore, this study allowed to determine the thermal resistance of the roof via a mean method meeting international standards (ISO 9869) using dynamic data. The method was implemented in a multi-zone building software, named ISOLAB, in order to automatically determine the thermal indicator.

Simulation and experimental demonstration of model predictive control in a building HVAC system

This article presents the framework and results of implementing optimization-based control algorithm for building HVAC systems and demonstrates its benefits through reduced building energy consumption as well as improved thermal comfort along with lessons learned. In particular, a practically effective and computationally efficient model predictive control algorithm is proposed to optimize building energy usage while maintaining thermal comfort in a multi-zone medium-sized commercial building. This article has two themes. Driven by the challenge of fully evaluating the benefit of the proposed model predictive controller against baseline control, a model predictive control design framework is first presented with its performance benchmarked based on a high-fidelity building HVAC simulation environment to verify its effectiveness and feasibility. Following the same model predictive control design framework, the experimental results from the same building located at the Philadelphia Navy Yard are then presented. For the simulation study, the performance of the model predictive control algorithm was estimated relative to baseline days with exactly the same internal loads and outdoor conditions, and it was estimated that model predictive control reduced the total electrical energy consumption by around 17.5%. For the subsequent experimental demonstration, the performance of the model predictive control algorithm was estimated relative to baseline days with similar outdoor air temperature patterns during the cooling and shoulder seasons, and it was concluded that model predictive control reduced the total electrical energy consumption by more than 20% on average while improving thermal comfort in terms of zone air temperature.

Study of the thermal insulation properties of the glass fiber board used for interior building envelope

Thermal insulation plays an important role in building energy savings. Previous researchers mainly focused on the exterior building envelope insulation. However, interior building envelope insulation can also reduce the building energy consumptions by minimizing the heat transfers between adjacent zones at different temperatures, especially for the multi-zone buildings. In this research, we studied the thermal insulation performance of the glass fiber board used for interior building envelope. Firstly, a mathematical model was developed to predict the effective thermal conductivity of the glass fiber boards. Then the mathematical model was validated by the measured thermal conductivities of four sample glass fiber boards with different thicknesses. Finally, we used eQuest to simulate the heating energy consumptions of a typical residential building using central heating system and the glass fiber boards as the interior building envelope insulation. The simulations were conducted in two different climatic zones in the northern China. The simulated results indicated that there was considerable heating energy saving potential by using the glass fiber boards as the interior building envelope insulation. Nevertheless, the glass fiber boards were not suggested to be too thick, for the energy saving percentages increased slowly when the insulation thickness was above 20mm.

Virtual partition surface temperature sensor based on linear parametric model

Multi-zone structure is common in commercial office buildings, retail stores and supermarkets. Because there is no physical partition between zones, there could exist significant thermal impact among the adjacent zones than in other commercial buildings. It is critical to accurately analyze the energy interaction and reduce the modeling uncertainty for supporting advanced control. We propose a virtual partition surface temperature sensor for quantifying the variables and solve this challenge by using linear parametric models. The derived models based on physical law can be used as a guideline on selecting appropriate orders in mainly ARMAX (autoregressive moving average with exogenous variables) and/or ARX for improving the sensor’s performance. Validation of the virtual temperature models is conducted by three validation criteria: goodness of fit (G), mean squared error (MSE) and coefficient of determination (R2) under off-control conditions. The validation results show that the physical model based linear parametric model, ARX 211, performs well and similar to other system identification models, such as ARMAX 2111 and ARX 221, for estimating surface temperatures. The sensitivity analysis using three on-control conditions (under-sizing, proper-sizing and over-sizing condition) is conducted for analyzing and evaluating the performance and barriers of this virtual sensor. The proposed easy-to-implement model can be applied to support supervisory control of equipment in multi-zone buildings and other applications to supplement the measurements, like estimating the temperature of a structure integrated cooling or heating application in renewable energy areas.

A neural network-based multi-zone modelling approach for predictive control system design in commercial buildings

Predictive control techniques for heating, ventilation and air conditioning (HVAC) systems have been paid an increasing attention in recent years. Such methods rely on building models to accurately predict indoor temperature and make optimal control decisions. Obtaining building models is challenging, as buildings’ thermal dynamics are nonlinear, have long time delays, and contain uncertainties. Previous studies on building modelling work mostly focused on small-scale buildings and single-zone cases. They do not accommodate some important features of real-world commercial buildings, such as the effects of thermal coupling between adjacent zones. This paper presents an artificial neural network (ANN) model-based system identification method to model multi-zone buildings. The proposed model considers the energy input from mechanical cooling, ventilation, weathher change, and in particular, the convective heat transfer between the adjacent zones. The testing of the temperature history shows that the proposed ANN model captures the thermal interactions between the zones reasonably well, therefore achieves more accurate prediction results than a single-zone model. Based on the model, a simple yet effective model-based predictive control method is developed, with the results showing that comfortable temperature can be maintained with reduced energy consumption.

Thermal performance of a nearly zero energy passive house integrated with the air–air heat exchanger and the earth–water heat exchanger

This paper presents an investigation carried out for evaluating the dynamic thermal performance of a residential house using a multi-zone building model simulated with the help of TRNSYS 17. The building model integrates systems such as an air–air heat exchanger (AAHE), a water–air heat exchanger (WAHE) coupled with an earth–water heat exchanger (EWHE). The temperature based control strategies for these systems are recommended based on the simulation results. The AAHE and the EWHE have impact of 66% and 7% respectively on reduction of the annual heating consumption of the house. All the integrated systems together contribute significantly (72%) in reducing the annual heating consumption of the house. The annual heating consumption of the house per unit floor area is estimated as 6.9kWh/(m2 year) which is within the passive house standard. There is significant reduction of the overheating time above 25°C due to the EWHE installed in the present house with annual ventilation air cooling contribution of 602.6kWh/year.

Judicious choice of the building compactness to improve thermo-aeraulic comfort in hot climate

The geometric shape and arrangement of the buildings have a great influence on the indoor climate. Compactness is one of the most important factors, which reduces heating and cooling requirements. These parameters result from geometrical concepts, used to maximize the internal volume of the structure according to its shape. The present study aims at developing a new approach for transient thermal behavior simulation of multizone buildings in Saharan climate. Thermal nodal method was used to apprehend thermo-aeraulic behavior of air subjected to varied solicitations.As result, this work proves that the compactness is better when the compactness index is lower. For this reason, we must privilege some urban typologies such as the rows of terraced houses, collective buildings and high-dimensional buildings.

Autozoner: an algorithm for automatic thermal zoning of buildings with unknown interior space definitions

In this paper, we present a general algorithm to automatically convert arbitrary building massing models into multi-zone building energy models (BEM). The algorithm follows current guidelines for thermal zone discretization of BEMs when actual interior space boundaries are yet undefined. Envisioned applications are for rapid model generation during schematic building design as well as for urban massing studies. We present an argument that current recommendations for separating core from perimeter zones effectively follow a straight-skeleton subdivision. Following a step-by-step explanation of the procedure, a number of example building shapes of varying complexity are shown to demonstrate the algorithm's robustness and suitability for automated multi-zone BEM generation. Going forward, it is recommended that the algorithm is adopted by software developers to ensure more consistent thermal model production within the building simulation community.

Integration of eaves and shading devices for improving the thermal comfort in a multi-zone building

This paper introduces a new approach to the description and modelling of multi-zone buildings in Saharan climate. Therefore, nodal method was used to apprehend thermo-aeraulic behavior of air subjected to varied solicitations. A coupling was made between equations proposed by P. Rumianowski and some equations of a building thermal energy model found in the TRNSYS user manual. Runge-Kutta fourth order numerical method was used to solve the obtained system of differential equations. Theses results show that proper design of passive houses in an arid region is based on the control of direct solar gains, temperatures and specific humidities. According to the compactness index, the insersion of solar shading and eaves can provide improved thermo-aeraulic comfort.

A new modelling approach of a multizone building to assess the influence of building orientation in Saharan climate

Orientation of building is a very important factor which is directly connected to the standards of thermal comfort within building. It is guided by natural elements like sunlight and its intensity, direction of the wind, seasons of the year and temperature variations. The orientation effect of a non-air-conditioned building on its thermal performance has been analyzed in terms of direct solar gain and temperature index for hot-dry climates. This paper aims at introducing an improved methodology for the dynamic modeling of buildings by the thermal nodal method. The evaluation is derived from a series of computer simulations. As a result, the influence of orientation changing depends on the floors and exterior walls constructing materials, the insulation levels and application of the inseparable rules of the bioclimatic design.

A general approach for generating reduced-order models for large multi-zone buildings

Many approaches for reducing model complexities have been suggested for characterizing the dynamic behaviour of buildings. However, previous work has focused on buildings that have a relatively small number of zones and there have been very limited comparisons with experimental data or with the predictions and computational requirements of validated simulation models that are widely used. In particular, the applicability to large multi-zone buildings has not been addressed. This is an important application, where the cost to generate a reduced-order model (ROM) can be significant, but the benefits of ROM for analysis and design for building system can be tremendous. This paper presents a general and computationally efficient approach for generating a ROM from a detailed representation of the dynamics of commercial sized multi-zone buildings and provides comparisons of predictions and computational requirements with a commercial building simulation tool.

Analysis of thermal effects of vegetated envelopes: Integration of a validated model in a building energy simulation program

In this paper, a newly developed heat and moisture transfer model for green envelopes is integrated in a transient building simulation program (TRNSYS) in order to investigate its dynamic performances coupled with a multizone building code. On the one hand we focus on the understanding of the coupled heat and mass transfers between green envelopes and the building; and on the other hand we study the model accuracy to assess the vegetation impacts together with building design. At first, the model reliability is verified through experimental comparisons during a summer period. Then, the developed simulation tool is used to assess the impacts of green walls on building energy performance. Since this model involves different hygrothermal transfer phenomena, the detailed numerical model results are analyzed to determine the weight of each phenomenon: evapotranspiration, shading effect and additional thermal resistance of green roof or wall. The results highlight the thermal benefits in summer and winter, especially for the west walls. The analysis of the different transfer mechanisms show that the foliage shading reduces the surface temperature variation whereas the evapotranspiration ensures the passive cooling when the water availability is sufficient.

Development and application of an updated whole-building coupled thermal, airflow and contaminant transport simulation program (TRNSYS/CONTAM)

The TRNSYS energy analysis tool has been capable of simulating whole-building coupled heat transfer and building airflow for about 10 years. The most recent implementation was based on two TRNSYS modules, Type 56 and Type 97. Type 97 is based on a subset of the airflow calculation capabilities of the CONTAM multizone airflow and contaminant transport program developed by the National Institute of Standards and Technology. This paper describes the development of new CONTAM capabilities in support of an updated combined, multizone building heat transfer, airflow and contaminant transport simulation approach using TRNSYS. It presents an illustrative case that highlights the new coupling capability and also presents the application of this coupled simulation approach to a practical design problem of the energy use related to airflow through entry doors in non-residential buildings.

Energy saving technique for cooling dominated academic building: Techno-economic analysis of its application

Adaptive cooling technique has been proposed previously, as an energy efficient strategy for a centralized HVAC system in a tropical environment. It served single or multi zone buildings by considering both the occupancy pattern (occupied and unoccupied periods) and the local weather conditions. This technique demonstrated considerable annual energy saving potential, however, the technical consequence and economic evaluation for its application have not been provided. This paper aims to analyze the technical and economical feasibility of the proposed technique for an academic building in Universiti Teknologi PETRONAS. It showed that a dual-duct dual-fan system was required to maximize technical feasibility of the proposed technique due to huge cooling load gap, during occupied and unoccupied periods. At the end, an economic evaluation by using net present worth (NPW) method and 3 financing scenarios were performed by considering the dual-duct dual-fan system. With an assumption of 10years service time, NPW value of the proposed technique was RM176,404 and hence, it became evident that the proposed adaptive comfort technique was economically feasible.

Simulation and Analysis of Annual Dynamic Air Conditioning Load for Multi-Zone Building

Applying TRNSYS, this paper introduced a numerical simulation of annual dynamic air conditioning load for the standard floor, the refuge floor and the top floor of a high-rise building in Tianjin. Results suggest that even though the refuge floor and the top floor share similar load characteristics of heating & cooling air-conditioning, they have different load sizes, and the load characteristic of the standard floor is different from them.

A state-space modeling approach and multi-level optimization algorithm for predictive control of multi-zone buildings with mixed-mode cooling

The paper presents a control-oriented modeling approach for multi-zone buildings with mixed-mode cooling, based on the linear state-space representation with varying coefficient matrices. Key features are the time-variant thermal resistances, associated with the heat extraction due to airflow, calculated using an airflow network model. This approach was validated with experimental data collected in a two-zone test-building under four operation modes. A forward linear time-variant state-space (LTV-SS) model, developed based on first principles, was then used as a true representation of the building, to identify the parameters of a low-order LTV-SS gray-box model. The low-order model can predict the building thermal dynamics with sufficient accuracy with a root mean square error (RMSE) of 0.58 °C for the air and 1.08 °C for the area-weighted mean surface temperature in the south direct gain zone. Furthermore, the study develops a progressive refinement (ProRe) optimization method, following the multi-level optimization topology and branch and bound decision trimming strategy, to find sequences of binary (open/close) decisions for the motorized windows. Due to the significant improvement in computing time, the models and algorithms presented in this paper enable long-term simulation for MPC performance evaluation and implementation of predictive strategies in real controllers.

Decentralized predictive thermal control for buildings

This paper studies the problem of decentralized control design for thermal control in buildings, to achieve a satisfactory trade-off between underlying performance and robustness objectives. An output-feedback, model predictive framework is used for decentralized control which is based on a reduced order system representation. It entails the use of decentralized extended state observers to address the issue of unavailability of all states and disturbances. The decision on control architecture selection is based on an agglomerative clustering methodology developed previously [22]. The potential use of the proposed control design methodology is demonstrated in simulation on a multi-zone building, which quantifies the tradeoffs in performance and robustness with respect to the degree of decentralization.