Ian Beausoleil-Morrison

Synthetically derived profiles for representing occupant-driven electric loads in Canadian housing

As one objective of the International Energy Agencys Energy Conservation in Buildings and Community Systems Programme Annex 42, detailed Canadian household electrical demand profiles were created using a bottom-up approach from available inputs, including a detailed appliance set, annual consumption targets and occupancy patterns. These profiles were created for use in the simulation of residential cogeneration devices to examine the issues of system performance, efficiency and emission reduction potential. This article describes the steps taken to generate these 5-min electrical consumption profiles for three target single-family detached households – low, medium and high consumers, a comparison of the generated output with measured data from Hydro Québec, and a demonstration of the use of the new profiles in building performance simulations of residential cogeneration devices.

Integrating CFD and building simulation

Abstract To provide practitioners with the means to tackle problems related to poor indoor environments, building simulation and computational fluid dynamics can usefully be integrated within a single computational framework. This paper describes the outcomes from a research project sponsored by the European Commission, which furthered the CFD modelling aspects of the ESP-r system. The paper summarises the form of the CFD model, describes the method used to integrate the thermal and flow domains and reports the outcome from an empirical validation exercise.

The adaptive conflation of computational fluid dynamics with whole-building thermal simulation

Abstract An adaptive controller was devised and implemented within the ESP-r simulation program to support the conflation of CFD with dynamic whole-building thermal simulation. This controller manages all interactions between the thermal and CFD modelling domains. It incorporates the latest turbulence modelling advancements applicable for room air flow simulation and possesses a suite of handshaking and thermal boundary condition treatments. The controller is based upon a double-pass modelling approach. Each time-step that the thermal domain handshakes with CFD, an investigative simulation is performed to approximate the room’s flow and temperature field. Using these estimates the controller determines the nature of the flow (forced, buoyant, mixed, fully turbulent, weakly turbulent) adjacent to each surface. This information is used to select suitable boundary condition treatments for each surface. A second CFD simulation is then performed using the refined modelling approach to more accurately resolve the room’s air flow and temperature distribution, and to predict surface convection.

The adaptive simulation of convective heat transfer at internal building surfaces

A flow responsive algorithm was devised and implemented within the ESP-r simulation program to advance the modelling of convective heat transfer at internal building surfaces. Empirical methods were extracted from the literature and a new method for characterizing mixed flow was created to provide the algorithm with a basis of 28 convection coefficient correlations. Collectively these methods can calculate convection coefficients for most flows of practical interest in building modelling. Working with this suite of correlations, the algorithm dynamically controls the modelling of convection by assigning appropriate equations to each internal surface each time-step of the simulation.

An algorithm for calculating convection coefficients for internal building surfaces for the case of mixed flow in rooms

Abstract The treatment of convective heat transfer at internal building surfaces has a significant impact on the simulation of heat and air flow. Accurate approaches for the range of flow regimes experienced within buildings (buoyant flow adjacent to walls, buoyant plumes rising from radiators, fan-driven flows, etc.) are required, as is the ability to select an appropriate method for the case at hand and to adapt modelling to changes in the flow. A new approach — drawing upon previously published methods — has been developed for modelling mixed convection within mechanically ventilated rooms. It is applicable for rooms ventilated with ceiling mounted diffusers and is appropriate for both heating and cooling. ESP-r simulations performed with the mixed flow model indicate that the prediction of heating and cooling loads is highly sensitive to the treatment of surface convection and that significant errors can result if an inappropriate model is employed. The results also reveal that the choice of convection algorithm can influence design decisions drawn from a simulation-based analysis.

Coupling stochastic occupant models to building performance simulation using the discrete event system specification formalism

When applying occupant models to building performance simulation (BPS), it is common practice to use a discrete-time approach requiring fixed time steps. Consequently, a simulated occupants decisions do not increase in frequency in response to rapid changes in environmental conditions. Furthermore, as illustrated in this study through the analysis of a discrete-time EnergyPlus simulation, changing the time step between simulation runs may have a dramatic effect on BPS predictions. It is therefore necessary to adhere to a prescribed time step, which may complicate the synchronization of events when models of different domains are coupled. The main contribution of this study is an investigation of the viability of employing the discrete event system specification (DEVS) formalism to represent occupant behaviour without fixed and prescribed time steps. Results indicate that using an adaptive time advancement scheme, the DEVS formalism permits realistic patterns of decision-making while facilitating the coupling of stochastic occupant models with thermal and heating, ventilation and air-conditioning models.

Implementation and comparison of existing occupant behaviour models in EnergyPlus

To incorporate occupant behaviour in building performance simulation (BPS), researchers have developed a number of occupant behaviour and presence models based on long-term field observations. This paper describes the implementation of models from the literature for predicting occupancy and use of operable windows, blinds, lighting, and clothing for offices in the BPS tool EnergyPlus. In order to make the occupant models from the literature more widely available to researchers and practitioners, the EnergyPlus energy management system scripts are made publicly available. The paper then presents a comparison of the model predictions based on a typical office and demonstrates how differences in these models influence BPS results. In general, the window, blinds, and lighting use model predictions vary significantly from model to another. Despite these significant variations, the BPS models with different occupant behaviour model combinations provided consistent load reduction predictions in response to design changes.

Hybrid residential end-use energy and greenhouse gas emissions model - development and verification for Canada

This article presents the Canadian Hybrid Residential End-Use Energy and GHG Emissions Model (CHREM), a model based upon building performance simulation, and compares its estimates with residential sector energy consumption surveys and the estimates of other models. The CHREM advances the state of the art of residential sector energy consumption and green house gas (GHG) emissions modelling by three new contributions: (i) the use of a database of 16,952 unique house descriptions of thermal envelope and energy conversion system information that statistically represent the Canadian housing stock; (ii) a ‘hybrid’ modelling approach that integrates the neural network and engineering modelling methods to estimate the energy consumption of the major end-uses, providing the capacity to model alternative and renewable energy technologies, such as solar energy and energy storage systems; and (iii) a method for the accumulation and treatment of energy consumption and GHG emissions results as a function of end-use and energy source.

On adaptive occupant-learning window blind and lighting controls

Occupants have a significant impact upon building energy use, e.g. through the actuation of window blinds and switching off lights. Automation systems with fixed set points for controlling blinds and lights have been used in some applications as an attempt to mitigate the impact of occupant behaviour upon energy consumption. A conceptual framework of an alternative control method is presented, one in which the control system adapts control set points in real time to each occupants preferences. The potential of this hypothesis is demonstrated through a simulation-based study focused on a hypothetical south-facing office with existing empirical models that predict occupant behaviour regarding the control of window blinds and lights. The performance of a proposed adaptive automation system is simulated, one in which window-blind and lighting control set points are adapted in real time to learn the modelled occupant preferences using a Kalman filter. The performance of this alternative occupant-learning method of control is contrasted to that of two conventional control methods, one in which occupants have manual control over window blinds and lights, and the other that employs an automation system with fixed set points. The simulation results indicate that such an adaptive occupant-learning control method could lead to substantial energy savings.

A Model for Simulating the Thermal and Electrical Production of Small-Scale Solid-Oxide Fuel Cell Cogeneration Systems within Building Simulation Programs

A new model for predicting the thermal and electrical performance of solid-oxide fuel cell (SOFC) cogeneration devices for residential buildings has been developed and demonstrated. This is a system-level model that considers the thermodynamic performance of all components that consume energy and produce the thermal and electrical output of the SOFC-cogeneration device. The model relies heavily upon empirical information that can be acquired from the testing of coherent systems or components and is designed for operation at a time resolution that is in the order of minutes. Hence, it is appropriate for use in whole-building simulation programs, where it can be applied to assess the energy and greenhouse gas emission benefits of this nascent technology.