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Open Access Publications from the University of California

Building Efficiency and Sustainability in the Tropics (SinBerBEST)

The Center for Research in Energy Systems Transformation aims to address climate change and the sustainable resource supply crises by transforming the global energy system. CREST is investigating renewable energy solutions, supply and demand economics for load balancing, and innovative energy efficiency technologies. In addition to reducing greenhouse gas emissions, CREST technologies aim to limit the consumption of finite resources, such as water and rare earth metals.

Cover page of An Octet-Truss Engineered Concrete (OTEC) for lightweight structures

An Octet-Truss Engineered Concrete (OTEC) for lightweight structures

(2019)

Recent advances in the development of Ultra-High Performance Fiber-Reinforced Concrete (UHP-FRC) with very high compressive strength has inspired the development of a lightweight structure by engineering the void spaces in the material, thus taking advantage of porous concrete’s thermal insulating properties while maintaining strength and stiffness. This paper refers to this engineered material as Octet-Truss Engineered Concrete (OTEC). To make OTEC structures, UHP-FRC and “green” UHP-FRC (G-UHP-FRC) mixtures were developed. 50.8-mm side-length OTEC unit cell specimens with various element diameters as well as 5×1×1-cell OTEC flexural specimens with 8 mm-diameter elements were cast and tested under uniaxial compression and four-point bending, respectively. The compressive strength of the OTEC unit cell specimens with various element diameters is mainly stretching-dominated, and hence considerably surpasses that of the control foam Green Ultra-High Performance Concrete specimens with random pore orientations. These results indicate a promising application of UHP-FRC and G-UHP-FRC OTECs for lightweight structures.

Cover page of Identifying Unseen Faults for Smart Buildings by Incorporating Expert Knowledge with Data

Identifying Unseen Faults for Smart Buildings by Incorporating Expert Knowledge with Data

(2018)

Thanks to the development of sensor networks and information technology, data-driven fault detection and diagnosis (FDD) is getting more and more popular with rich data. In the building FDD field, mature supervised learning algorithms and strategies have been applied to detect and diagnose known faults. However, it is out of the question to collect labeled training data for every possible fault. Thus, there is a necessity to study FDD when the training data for some faults are unavailable. To the authors' best knowledge, few works have reported how to identify "unseen faults." In this paper, authors propose a novel expert knowledge-based unseen fault identification (EK-UFI) method to identify unseen faults by employing the similarities between known faults and unknown faults. The similarity is captured by incorporating essential expert knowledge that is encoded in the fault gene matrix. The fault gene is integrated with a latent incorporation matrix that transfers knowledge from known faults to unseen faults. With application to a real system, the proposed method is proven to be effective in identifying various building unknown faults with a high accuracy.

Cover page of A Bayesian method of evaluating discomfort due to glare: The effect of order bias from a large glare source

A Bayesian method of evaluating discomfort due to glare: The effect of order bias from a large glare source

(2018)

Replicating scientific findings is a fundamental aspect of research. However, in studies of discomfort due to glare, it is difficult to make comparisons between the results of different experiments since the statistical tests usually reported do not allow independent findings to be directly compared to each other. Here we present an alternative Bayesian approach that can address this problem. To show how this approach works, we performed a laboratory test with 55 participants to validate the effect of order bias previously detected in a similar study evaluating discomfort due to glare but, this time, under a large luminous source. Using the luminanceadjustment procedure, the glare source was varied to meet four sensations of discomfort due to glare. Adjustments were performed under three different order sequences: ascending, descending, and randomised. Test participants provided glare settings using a newly proposed evaluation scale. The effect of order bias detected in the original study was compared to the data obtained with the same methodological procedure in the new experiment using Bayesian inferential tests. The results showed a close replication, highlighting that the order bias effect found in the original study was also present in the new experiment. The wide application of Bayesian methods in the design and analysis of experimental studies may improve the accuracy and validity of glare models.

Cover page of Performance Analysis and Evaluation of Reactive Power Compensating Electric Spring with Linear Loads

Performance Analysis and Evaluation of Reactive Power Compensating Electric Spring with Linear Loads

(2018)

Reliance on renewable energy sources (RESs) such as solar and wind has increased to build a sustainable environment, however, their substantial implementation is hindered by their intermittency. Electric Spring (ES) is one of the technologies to mitigate the intermittent nature of the RESs. In an isolated RES powered microgrid, the ES in conjunction with the non-critical loads in a system like water heaters, refrigerators, and air-conditioners can regulate voltage of critical loads like security system, servers etc. This paper establishes the operating principles of the ES (with reactive power compensation only) and its interaction with RESs based on the understanding of AC power transfer between two sources. The accurate phasors in a system under two scenarios, with and without ES, are drawn. Also, performance of the ES is analyzed and evaluated with respect to variations in the loads (linear) and their types. It is augmented with analytical justifications and validated through simulations and experimental studies. Also, through analytical expressions, simulations, and experiments the importance of the non-critical load on the performance of the ES is illustrated. It is also highlighted that the compensation capabilities of the ES remain the same irrespective of the types of non-critical load.

Cover page of Experimental investigation of sunlight permeability of translucent concrete panels as a building envelope

Experimental investigation of sunlight permeability of translucent concrete panels as a building envelope

(2018)

An innovative building envelope was introduced for daylight permeability in an anidolic manner through the opaque parts of exterior façades and roofs. A prefabricated translucent concrete panel (TCP) with embedded optical fibers (OFs) was coupled with a layer outfitted with compound parabolic concentrators (CPCs). Such TCPs have been predominantly used for aesthetic purposes. Moreover, OFs and CPCs have been used in many industries, particularly for telecommunications and the concentration of solar energy, respectively. The goal of this study was to introduce a novel building-envelope construction solution that can transmit sunlight to the interior of a building. Because of the nature of the traditional building materials blocking the passage of natural light, artificial lighting was constantly required, even during daytime, which consumed a great deal of energy in the form of artificial electrical light. This proposed building envelope is a viable solution to alleviate this inefficiency. Experimental results show the effectiveness and limitations of the proposed solution discussed in this paper.

Cover page of Design Automation for Smart Building Systems

Design Automation for Smart Building Systems

(2018)

Smart buildings today are aimed at providing safe, healthy, comfortable, affordable, and beautiful spaces in a carbon and energy-efficient way. They are emerging as complex cyber-physical systems with humans in the loop. Cost, the need to cope with increasing functional complexity, flexibility, fragmentation of the supply chain, and time-to-market pressure are rendering the traditional heuristic and ad hoc design paradigms inefficient and insufficient for the future. In this paper, we present a platform-based methodology for smart building design. Platform-based design (PBD) promotes the reuse of hardware and software on shared infrastructures, enables rapid prototyping of applications, and involves extensive exploration of the design space to optimize design performance. In this paper, we identify, abstract, and formalize components of smart buildings, and present a design flow that maps high-level specifications of desired building applications to their physical implementations under the PBD framework. A case study on the design of on-demand heating, ventilation, and air conditioning (HVAC) systems is presented to demonstrate the use of PBD.

Cover page of Synchrotron X-ray nanotomographic and spectromicroscopic study of the tricalcium aluminate hydration in the presence of gypsum

Synchrotron X-ray nanotomographic and spectromicroscopic study of the tricalcium aluminate hydration in the presence of gypsum

(2018)

The rheology of modern Portland cement (PC) concrete critically depends on the correct dosage of gypsum (calcium sulfate hydrate) to control the hydration of the most reactive phase - tricalcium aluminate (C3A). The underlying physio-chemical mechanism, however, remains unsolved mainly due to the lack of high-spatial-resolved and chemistry-sensitive characterization of the C3A dissolution frontier. Here, we fill this gap by integrating synchrotron-radiation based crystallographic, photon-energy-dependent spectroscopic and high-resolution morphological studies of the C3A hydration product layer. We propose that ettringite (6CaO·Al2O3·SO3·32H2O) is the only hydration product after the initial reaction period and before complete gypsum dissolution. We quantify the 2D and 3D morphology of the ettringite network, e.g. the packing density of ettringite at various surface locations and the surface dissolution heterogeneity. Our results show no trace of a rate-controlling diffusion barrier. We expect our work to have significant impact on modeling the kinetics and morphological evolution of PC hydration.

Cover page of Hybrid Simulation for Daylighting of Complex Fenestration Systems for Building Envelopes

Hybrid Simulation for Daylighting of Complex Fenestration Systems for Building Envelopes

(2018)

This paper reports the status of new hybrid simulation for daylight analysis method under development. The method combines both full-scale physical measurements and computational techniques, providing analysis results of complex fenestration system (CFS) with increased realism while keeping costs in check and, for the first time, the repeatability of excitation conditions at fullscale. The simulation method divides the physics of daylighting into the two primary components: direct and diffuse light. Preliminary results of the diffuse component of the system and the current state of the heliodon is presented in the paper for a novel CFS known as translucent concrete panels for energy-efficient building envelopes.

Cover page of Performance Based Engineering and Multi Criteria Decision Analysis for Sustainable and Resilient Building Design

Performance Based Engineering and Multi Criteria Decision Analysis for Sustainable and Resilient Building Design

(2018)

In this paper, an integrated approach for a holistic (involving notions of resiliency and sustainability) building design is presented to select the optimal design alternative based on multiple conflicting criteria using the multi-attribute utility theory (MAUT). A probabilistic formulation of MAUT is proposed, where the distributions of the uncertain parameters are determined by a performance-based engineering (PBE) approach. Here PBE is used to evaluate the building energy efficiency and sustainability in addition to structural safety. In the proposed framework, different design alternatives of a building are ranked based on the generalized expected utility, which is able to include the most adopted probabilistic decision models, like the expected utility and the cumulative prospect theory. The distributions of the utilities are obtained from the first-order reliability method to provide (i) good tradeoff between accuracy and efficiency, and (ii) rational decision making by evaluating the most critical realizations of the consequences of each alternative through the design point. The application of the proposed approach to a building shows that design for resilience may imply design for sustainability and that green buildings (alone) may be not resilient in the face of extreme events.

Cover page of Smart lighting system using ANN-IMC for personalized lighting control and daylight harvesting

Smart lighting system using ANN-IMC for personalized lighting control and daylight harvesting

(2018)

Lighting contributes a significant portion to the overall energy consumption in an office building. It is thus important to reduce the energy consumption of lighting systems especially for Net Zero Energy Buildings (NZEB). Maximizing daylight harvesting can significantly increase the energy savings. With increase in demand for satisfying occupant preferences in visual comfort, the need for personalized lighting in the office space is also rising. In this paper, a novel lighting control system for Net Zero Energy Buildings (NZEB) is proposed which models the lighting system using Artificial Neural Network (ANN) and utilizes this model with the Internal Model Control (IMC) principle for controller design. Modeling the lighting system using ANN reduces the challenge of modeling a large and complex system with inherent process variability without the need to analyze extensive data-sets. The proposed ANN-IMC controller uses feedback from sensors on the task table to maintain desired illuminance, is easy to tune with just one parameter and is robust to process variability. The proposed control design is applicable to square systems where the number of lights and number of sensors are equal. However, the proposed architecture can also be extended for controlling other lighting accessories such as roller blinds. The performance of the proposed lighting control system to harvest the daylight effectively is demonstrated using both simulation results and an experimental setup in test-bed environment. The versatility of the proposed system will allow an operator to deploy personalized lighting in an office space.