By Hilary Smith, Sustainability Resource Center
Imagine you’re a city planner. Dozens of questions have been laid out in front of you. How should the buildings be arranged? How should they be powered? Where should that power be generated?
Or, imagine you’re a site manager, seeking to maximize the energy efficiency of a single building. Based on the building’s current energy use and the amount of sunlight that reaches the building, would it make sense to install a solar PV system on the roof?
Decisions like these require an understanding of how factors both inside and outside of a building affect that building’s energy needs. Outdoor factors include things like air flow, solar radiation, reflected solar radiation (i.e. sunshine bouncing off of snow, or other buildings) and shading from vegetation and nearby buildings. Indoor factors include heating, cooling, and ventilation systems, as well as water and electricity flows.
Modelling software already exists to provide details about these indoor and outdoor factors separately. But U of U researchers in the Environmental Fluid Dynamics (EFD) and Site-Specific Energy Systems (SSES) Labs have been collaborating recently to meld these existing models together, in order to provide hyper-localized information that is more accurate and actionable than the data that was available to planners, architects, and facilities managers in the past.
Specifically, the new, joint simulation provides a framework for making decisions about the placement of distributed energy systems in built environments, explains Amanda Smith, research director of the SSES Lab and an assistant professor in mechanical engineering at the U. Distributed energy systems are decentralized, modular power generators that are located close to the places and structures they serve—and they often employ renewable energy sources, like wind or solar.
The project integrates a computer model called QUIC-EnvSim (QES), short for Quick Urban Industrial Complex-Environmental Simulation, with a publicly available building energy model called EnergyPlus, which can be downloaded for free, along with its source code, from the U.S. Department of Energy.
EnergyPlus allows users to model all of a building’s energy flows, including heating, cooling, lighting, ventilation, and water usage. It can also model a building’s greenhouse gas emissions, as well as the building’s projected energy costs. It can be used for both existing and future/planned buildings.
QES has been around for about 15 years and was originally developed at Los Alamos National Lab in Los Alamos, New Mexico, by a trio of researchers including U of U mechanical engineering professor Eric Pardyjak. It was first designed to simulate the flow and dispersion of pollutants in and around buildings, but over the years it has expanded its scope—it now models many more elements of urban microclimates, including shading and cooling, water evaporation from trees and ground surfaces, and radiation transport, explains Pardyjak.
Smith hopes that the joining of these two systems will better allow stakeholders to understand the impacts of small-scale power generation on the surrounding environment and society. Understanding local factors at this level of detail, she explains, can allow planners to choose what to maximize or minimize: targets for local emissions, overall emissions, or economic cost. Smith explains this process of optimization in the following way:
Optimizations might be simple: i.e., choosing which energy-producing option—gas-fired generation or a new solar PV system—would generate the greatest savings in building operating costs for the next few years. Optimizations might also be more constrained: for example, if a building manager wants to limit on-site emissions to a certain amount and also to cap overall (on-site and indirect) emissions, the joint modelling system can suggest the optimal maximum size for a solar PV system. The joint modelling system can answer even more challenging and multifaceted optimizations as well, says Smith.
She says that the project team’s ultimate goal is to make the joint modelling software available to the public. Another future step will be to place monitors developed by the U’s Environmental Fluids Dynamics Lab around the U’s engineering buildings in order to validate the results coming out of the joint modelling system.
This pilot study could provide a “new picture of energy potential on campus,” says Smith—and campus is just the beginning.
“More than 50 percent of the world’s population now lives in urban areas,” says Pardyjak. “Urban air quality, water scarcity and energy are major issues in many regions around the world. We need to develop strategies that allow us to modify existing urban forms as well as plan future cities so that they are more sustainable and provide for improved quality of life,” he says, adding that solutions need to be adaptable to local needs, like climate and governance.
“As an engineer, it’s exciting to be part of the solution to these challenges,” he says.
Hilary Smith is a graduate student in Environmental Humanities and a graduate assistant in the Sustainability Resource Center. Research spotlight is an occasional feature on Sustainable Utah. E-mail future story ideas to Hilary.firstname.lastname@example.org.