Systems Engineering-Based Model Development: Application to Predictive Simulation of a Net-zero Home

Abstract

Building design has grown increasingly sophisticated throughout the decades. In recent years, assessments of building performance and sustainability has grown in popularity as the U.S. Green Building Council published LEED certifications for new and existing constructs. The LEED rating system utilizes standards made by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) for areas in thermal comfort, air quality, energy building performance, and heat, ventilation, and air conditioning (HVAC) operation. Energy building performance has a more overarching role in this rating as the other three standards play into the overall loads associated with any building. Submittal of energy performance building reports for construction design and green building rating systems is becoming more common as building performance assessment software becomes more widely available. The University of Maryland currently is a participant in the Solar Decathlon intercollegiate competition sponsored by the Department of Energy. The University of Maryland's reACT team is working to construct a net-zero solar powered house for judging in Denver, CO in October 2017. Concurrently with the housing design, a substantial effort was put into assessing the projected building performance to aid in the design process and to set the stage for model-based home automation. While software such as OpenStudio and BEOPT are available and were used for year-averaged performance reports, a physically based model of the house was built from scratch to serve as a real-time simulation of virtual versions of reACT located in College Park, MD and Denver, CO and is described in detail as the Virtual House. The overall system design of the Virtual House can be described as a general set of inputs, dynamic simulation, and output of overall profiles. Inputs for the system include geometric design of the house, specified materials, schedules, daily weather data, and solar irradiance. Dynamic simulation refers to a simultaneous integration of both independent and dependent fluctuating loads upon the time of day regarding both heat and power balances. Finally, outputs showcase heat and power profiles throughout a day. The bulk of analysis of inputs and simulation has been rooted in fundamental calculations. In terms of future work, outputs coming from the Virtual House are currently being stored and are now looking towards validation with measured sensor data. As of now reACT is not in construction phase and measured data is unavailable. In order to validate the Virtual House, there are current plans to outfit the previous Solar Decathlon 2007 entry LEAFhouse with sensors. With this, measured and simulated data can be assessed after modifying the current Virtual House model for LEAFhouse specific inputs. Ultimately, work will be transitioned back to reACT as it is built with Solar Decathlon 2017 in mind.