Research

Wil Srubar
To address growing environmental concerns over construction material production, innovative materials, such as recycled-aggregate concrete, bioplastics, and natural-fiber composites, are being engineered to exhibit lower ecological footprints compared to their conventional counterparts. However, research has shown that incorporating biobased and recycled materials may negatively impact mechanical properties and material durability. Often, green material substitutes are evaluated solely in terms of reduced environmental impact, as quantified through lifecycle assessments (LCAs) or as reported by manufacturers through environmental product declarations (EPDs). Frequently, such cradle-to-gate comparisons are made without regard for long-term performance, maintenance requirements, or expected service-life – all of which are well known to affect the environmental and economic impact of materials and structures. This research focuses on the development and implementation of probabilistic service-life prediction models for novel bio- and cement-based materials using a combination of experimental and numerical methods. Results suggest that initial environmental benefits of some green materials, such as recycled-aggregate concrete, may be compromised by reductions in long-term durability in certain applications.

John Zhai
With the goal of achieving net-zero-energy buildings, this NSF-EFRI project applies biomimetic design principles to develop intelligent and integrated building envelope systems based on smart materials and innovative structures, upon a series of advanced and multi-disciplinary studies on material science, structure engineering, heat transfer, fluid mechanics, system optimization, and architecture integration. The proposed living wall concept acquires its original idea from biomimicry of body’s thermo-regulation systems (i.e., respiratory and circulatory systems) that can efficiently adapt to changes in the surrounding environment via sophisticated heat transfer processes and metabolic adjustments. The novel living wall system embeds two sets of optimized micro-vascular fluid channel (MVFC) networks and distributed phase change medium (PCM) into an innovative polymer-based wall unit to allow autonomous movement of air and liquid and charge/discharge of PCM in response to real-time indoor and outdoor temperature variations so as to dynamically regulate the thermal behavior of building envelope and the entire dwelling. While natural convection drives air through a porous holding material, novel hydrogels with tailored temperature sensitivity are developed to move liquid in wall thickness direction. Mathematical models and computational design approaches are developed to optimize the layout of the holding material, the MVFCs and PCM components. A prototype of the living wall will be fabricated and studied under a series of thermal and structural loading scenarios. The performance of the entire living wall system under dynamic indoor and outdoor conditions will be systematically investigated through multi-physics simulations and novel design approaches to seamlessly integrate the living wall concept into current and future building constructions.

Moncef Krarti
Optimal and cost-effective energy efficiency design and operation options are evaluated for office buildings in several MENA countries. In the analysis, several design and operation features are considered including orientation, window location and size, high performance glazing types, wall and roof insulation levels, energy efficient lighting systems, daylighting controls, temperature settings, and energy efficient heating and cooling systems. First, the results of the optimization results from a sequential search technique are compared against those obtained by a more time consuming brute-force optimization approach. Then, the optimal design features for a prototypical office building are determined for selected locations throughout the world. The optimization results indicate that utilizing daylighting controls, energy efficient lighting fixtures, and low-e double glazing, and roof insulation are required energy efficiency measures to design high energy performance office buildings throughout climatic zones in MENA region. In particular, it is found that implementing these measures can cost-effectively reduce the annual energy use by 50% compared to the current design practices of office buildings in the MENA region.

Gregor Henze
The primary purpose of heating, ventilating, and air-conditioning systems is to provide acceptable indoor air quality and thermal comfort. Mixed-mode ventilation systems provide good indoor air quality and thermal climate using natural ventilation whenever the outdoor weather conditions are favorable, but revert to mechanical systems for ventilation and cooling whenever external conditions are too harsh. A mixed-mode building should switch between these two modes of operation according to seasonal and diurnal variations in the indoor thermal conditions and the outdoor environment. Such a building requires an intelligent control system that can switch automatically between natural and mechanical modes in a way that minimizes energy consumption without compromising indoor air quality or the thermal comfort of its occupants. This ASHRAE-funded project 1597 (RP-1597) has three primary goals. The first task is to examine and characterize occupant behavior patterns most likely to influence the mixed-mode control scheme, such as occupant use of windows, blinds, lights, and equipment in a building. The second task is to marry statistical models of those occupant behaviors to building energy simulation models, and to use stochastic optimization to optimize building control logic in simulation. The third task is to leverage the results of offline optimizations, and apply machine-learning techniques to develop simple, usable control rules that can be implemented in actual buildings, and to test them in a real building. The Research Support Facility (RSF) on the National Renewable Energy Laboratory (NREL) campus in Golden, CO, is one of the largest net zero energy buildings in the world, and currently employs natural ventilation control logic that was improved as part of this research.

Mike Brandemuehl & John Zhai
The study proposes and develops a novel building integrated photovoltaic-thermal (BIPV/T) collector system. An experimentally validated computational fluid dynamics (CFD) model is applied to determine the effect of active heat recovery on cell efficiency and to determine the effectiveness of the device as a solar hot water heater by integrating PV and solar water systems. Parametric analysis indicates that cell efficiency can be raised by 5.3% and that water temperatures suitable for domestic hot water use are possible. Thermal and combined (thermal plus electrical) efficiencies reach 19% and 34.9%, respectively. A new correlation is developed relating electrical efficiency to collector inlet water temperature, ambient air temperature and insolation that allows cell efficiency to be calculated directly.

Gregor Henze
Advances towards a more intelligent electric grid have created opportunities for commercial buildings to become active participants in daily grid operations. Actively managing electric load in response to real-time pricing allows buildings to reduce operating expense while decreasing grid congestion through shifting consumption to more favorable periods. Flexible demand resources can also provide necessary grid ancillary services, such as frequency regulation and spinning reserves, resulting in more efficient grid operation and revenue opportunities for demand resources. This project seeks to develop methods for determining optimal commercial building control strategies that consider opportunities to participate in both energy and ancillary service markets. A communal perspective is taken to also explore the potential for synergistic effect from optimizing an ensemble of commercial buildings around a common objective.

John Zhai
Effective ventilation is critical to the successful prevention of surgical site infections (SSI) in hospital operating rooms. ASHRAE Standard 170 provides specific requirements for the design of hospital operating room ventilation systems, including specifications for the air change rates, supply air face velocity, room pressurization, diffuser coverage area, return grille locations, and air filtration systems. The scope of this ASHRAE project includes the following tasks: (1) On-site clinical observations of typical wound size and temperature; (2) Field measurements of typical OR conditions; (3) Controlled full-scale laboratory experiments of air flow and particle transport; (4) Quantitative assessment and verification of CFD models and methods; (5) Revision and contribution to the current and new design guidelines and standards.

Wangda Zuo
Funded by the U.S. Department of Energy, we are developing an open-source, free software package which provides practical, end-to-end (from the IT equipment to heat rejection to the ambient) modeling and optimization for data center cooling. It can be used as a stand-alone tool by data center designers, service consultants and facility managers, or be integrated into existing data center management software for autonomous optimal operation. It will be the first practical tool that couples the modeling of airflow-management and cooling systems to enable a global data center cooling optimization. Its self-learning regression model enabled by an in situ adaptive tabulation algorithm and a fast fluid dynamics model can predict the critical airflow information under various operational conditions within a few milliseconds. The equation-based modeling language allows a fast and flexible modeling of various cooling system configurations. More information at here.

Wangda Zuo
The project goal is to develop a framework to support the design and operation of future grid-interactive resilient communities. Here “grid interactive” means that the community can provide frequency regulation service to power grid at normal operations. The “resilient” means that the community can provide continuous power supply for critical needs at island mode during natural or man-made disaster. We are identifying and prioritizing behind-the-meter end-use resources. We are also developing a prototype tool that offers assessment of end-use load-utilization patterns and provides real-time dynamic prioritization of the energy-consuming loads based on end-use functional utility to satisfy occupant activity requirements. More information is here.