Ardeshir Mahdavi

Simulation-based control of building systems operation

Abstract Building performance simulation research has traditionally concentrated on the building design phase. However, computational modeling can also apply to the building operation phase. To explore this potential, we (a) describe the model-based building systems control idea, (b) illustrate this idea using a simple computational scenario pertaining to the control of the thermal environment in buildings, (c) report on a prototypical implementation of a model-based lighting control strategy.

Implications of indoor climate control for comfort, energy and environment

Abstract This paper critically examines the underlying premises of indoor climate control technologies and the HVAC industry (heating, ventilating, air-conditioning). It questions whether ‘total environmental control’ is possible, effective and desirable. The paper also reviews the methods and terminology of thermal comfort science focusing on the question of predictability of peoples environmental preferences. The paper concludes with a review of recent critical observations and ideas that transcend conventional control technologies and corresponding comfort standards toward new vistas in environmental design.

An integrated approach to design and engineering of intelligent buildings-The Intelligent Workplace at Carnegie Mellon University

Abstract In the past few years, there have been significant advances made in the design and engineering of “intelligent” workplaces, buildings that not only accommodate major advances in office technology but provide better physical and environmental settings for the occupants. This paper will briefly present recent approaches to the creation of innovative environments for the advanced workplace. The architectural and engineering advances demonstrated in Japan, Germany, North America, the United Kingdom, and France can be summarized in four major system categories: (1) enclosure innovations including approaches to load balancing, natural ventilation and daylighting; (2) heating, ventilation and air-conditioning (HVAC) system innovations including approaches to local control and improved environmental contact; (3) data/voice/power “connectivity” innovations; and (4) interior system innovations, including approaches to workstation and workgroup design for improved spatial, thermal, acoustic, visual and air quality. In-depth international field studies of over 20 intelligent office buildings have been carried out by a multidisciplinary expert team of the Advanced Building Systems Integration Consortium (ABSIC) based at Carnegie Mellon University. ABSIC is a university-industry-government partnership focused on the definition and development of the advanced workplace. The ABSIC field team evaluated the component and integrated system innovations for their multidimensional performance qualities, through expert analysis, occupancy assessments and field diagnostics. Based on the results of the case studies and building on the most recent technological advances, the ABSIC team developed the concepts for the Intelligent Workplace, a 7000 square foot living laboratory of office environments and innovations. This project is now under construction at Carnegie Mellon University and its features are discussed in the second section of this paper.

Patterns and Implications of User Control Actions in Buildings

The control actions by the inhabitants of buildings can significantly affect the energy performance of buildings and their environmental impact. However, relatively few studies have investigated such actions in detail and on a long-term basis. In most buildings, occupants operate control devices such as windows, shades, luminaries, radiators, and fans to bring about desirable indoor environmental conditions. Knowledge of such user actions is crucial for accurate prediction of building performance (energy use, indoor climate) and effective operation of building service systems. The present contribution describes an effort to observe control-oriented occupant behavior in office buildings in Austria over a period of 1 year. Thereby, user control actions as related to one or more of the building systems for ambient lighting, shading, window ventilation, and heating were monitored together with indoor and outdoor environmental parameters. The collected data has been analyzed to explore relationships between the kinds and frequency of the control actions and the magnitude and dynamism of indoor and outdoor environmental changes. Moreover, implications of user actions for energy use are studied.

Integrated and distributed computational support for building performance evaluation

This paper reports on the progress of the SEMPER prototype 2 (S2) project. This is an ongoing effort toward an Internet-based environment for distributed collaborative performance-based building design and evaluation. A user can access the S2 system regardless of hardware, operating system or location on a network. Geographically distributed users can generate and edit building models via a platform-independent user interface. These building models can then be made subject to concurrent analysis by multiple simulation applications running on remote servers. Persistent storage is provided for project data and evaluation results. Designers using the system have access to multiple libraries with semantic building information.

A HYBRID SYSTEM FOR DAYLIGHT-RESPONSIVE LIGHTING CONTROL

Capability is provided to dynamically reallocate the multiplex data stream from one communication channel to a plurality of communication channels. This allows increased flexibility in responding to degradation of the main communication channel and in accommodating increased user demand exceeding the capacity of the main channel. A table is generated to control the DTE PORTs accessed during each slot of a multiplexer frame. A separate table is generated to control the allocation of multiplex data between communication channels. Both tables are generated based upon a common Hash table. A plurality of Hash tables correspond to different output data rates and permit the output rate of the multiplexer to coincide with the maximum output rate capacity of an associated transmission device such as a modem.

The sensitivity of building performance simulation results to the choice of occupants’ presence models: a case study

The considerable performance implications of occupants’ presence and behaviour in buildings render the inclusion of corresponding models in simulation applications both necessary and critical. In this context, an important question concerns the implications of different occupancy modelling approaches for simulation results. The present contribution addresses this issue by modelling an office building to obtain heating and cooling demands and peak loads. To represent occupants’ presence patterns in the model, standard-based and observed diversity profiles, stochastic realizations of these profiles, and the full-year observational occupancy data are deployed. Subsequently, a sequence of simulation runs – involving Monte-Carlo simulations of models with stochastic profiles – provides the distributions of results. The study suggests that the viability of simulation results regarding building-level annual heating and cooling demands and peak heating and cooling loads is primarily dependent on the availability of reliable estimations of actual occupancy, rather than stochastic or non-stochastic representation of presence patterns.

A preliminary study of representing the inter-occupant diversity in occupant modelling

Significant diversity between occupants and their presence and actions results in major uncertainty with regard to predicting building performance. However, many current occupant modelling approaches – even stochastic ones – suppress occupant diversity by focusing on developing representative occupants. Accordingly, existing approaches tend to limit the ability of stochastic occupant models to provide probabilistic building performance distributions. Using occupancy data from 16 private offices, this paper evaluated three hypotheses: (1) occupant parameters have a continuous distribution rather than discrete; (2) modelling occupants from aggregated data suppresses diversity; and (3) randomly selecting occupant traits exaggerates synthetic population diversity. The paper indicates that samples sizes for the studied occupants would have more appropriately been an order of magnitude higher: hundreds. This introductory paper shows that there are many future research needs with regard to modelling occupants.

Subjective Evaluation of Architectural Lighting via Computationally Rendered Images

The objective of the study described in the present paper is to empirically establish if and to what extent subjective lighting evaluation of architectural spaces can be reproduced using computationally rendered images ofsuch spaces.

Integrating thermal comfort field data analysis in a case-based building simulation environment

Abstract Despite the obvious importance of thermal comfort in the design of indoor environments, it has not been effectively integrated with design support tools. The reasons can be attributed in part to an absence of modular and flexible software architecture that facilitates dynamic data transfer between building performance simulation modules. Research has shown that the mathematical models of thermal comfort sometimes fail to accurately describe or predict thermal comfort in workplace settings even when the values of environmental and personal parameters are known. Thus, there is a critical need to provide a thermal comfort evaluation framework that, in addition to the algorithmic implementation of mathematical thermal comfort prediction models, would make use of the empirical knowledge base accumulated over the last 20 years from field experiments around the world. This paper first talks about an integrated simulation environment SEMPER that allows for multiple performance evaluation including thermal comfort analysis from a shared object model of building. Then, it discusses the results of a detailed thermal comfort analysis performed to find the reasons for the discrepancy between the predicted and observed values and the factors responsible for such discrepancy. Finally, the paper shows how the results of the empirical thermal comfort analysis can be used in designing better thermal environments.