Recent crest items

Polymer lattice-reinforcement for enhancing ductility of concrete

Mon, 5 Oct 2020 00:00:00 +0000

Concrete is the most widely used engineering material. While strong in compression, concrete is weak in tension and exhibits low ductility due to its low crack growth resistance. With increasingcompressive strength, concrete becomes even more brittle, hence requiring appropriate reinforcement to enhance its ductility. This paper presents a new method for increasing the ductility of ultra-high-performance concrete by reinforcing it with 3D printed polymeric lattices made of either polylactic acid (PLA) or acrylonitrile butadiene styrene (ABS). These latticereinforced concrete specimens were then tested in compression and four-point bending. The effect of polymeric reinforcement ratios on mechanical properties was investigated by testing two lattice configurations. The lattices were very successful in transforming the brittle ultrahigh-performance concrete (UHPC) into a ductile material with strain hardening behavior; all flexural specimens revealed multiple cracking and strain...

PMV-based event-triggered mechanism for building energy management under uncertainties

Tue, 19 Mar 2019 00:00:00 +0000

This paper provides a study of the optimal scheduling of building operation to minimize its energy cost under building operation uncertainties. Opposed to the usual way that describes thermal comfort using a static range of air temperature, the optimization of a tradeoff between energy cost and thermal comfort predicted mean vote (PMV) index is addressed in this paper. In order to integrate the calculation of the PMV index with the optimization procedure, we develop a sufficiently accurate approximation of the original PMV model which is computationally efficient. We develop a model-based periodic event-triggered mechanism (ETM) to handle the uncertainties in the building operation. Upon the triggering of predefined events, the ETM determines whether the optimal strategy should be recalculated. In this way, the communication and computational resources required can be significantly reduced. Numerical results show that the ETM method is robust with respect to the uncertainties...

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

Tue, 19 Mar 2019 00:00:00 +0000

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...

User Presence Estimation in Multi-Occupancy Rooms Using Plug-Load Meters and PIR Sensors

Tue, 19 Mar 2019 00:00:00 +0000

In the built environment, the paradigm is shifting from providing uniform environment for all occupants to accommodating individual preferences through decentralised comfort devices enabled by IoT (Internet of Things) and ubiquitous computing. The effective implementation of localised and personalised comfort-enhancing and energy-saving strategies depends critically on the ability to detect the occupant presence in the immediate local environment. In this paper, estimating individual user presence in a shared office-space room using plug-load meters monitoring the power consumption of users' desktop computers and PIR (passive infrared) sensors at every user's desk is investigated. By extracting informative features from the data obtained and simple k-means clustering analysis, best-case presence accuracies of 89-99% and absence accuracies of 87-96% are achieved as validated by comparing with the ground-truth data for 4 different users.

Solution chemistry of cubic and orthorhombic tricalcium aluminate hydration

Tue, 19 Mar 2019 00:00:00 +0000

This paper presents a solution chemistry-focused analysis of orthorhombic and cubic tricalcium aluminate (orth-C3A and cub-C3A, respectively) hydration. It is shown that the different solubilities of cub- and orth-C3A influence the bulk aqueous Ca to Al concentration ratio and the C3A/solution interface chemistry. The results are consistent with the bulk solution chemistry controlling orth-C3A dissolution, and with cub-C3A dissolution controlled by the formation of an Al-rich leached layer and adsorption of Ca‑sulfur ion pair complexes onto this layer. The polynaphthalene sulfonate-based admixture used here is identified to modify the solution chemistry and retard cub-C3A dissolution. Strategies to inhibit C3A dissolution in Portland cement are discussed.

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

Tue, 19 Mar 2019 00:00:00 +0000

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....

The Building Data Genome Project An Open, Public Data Set from Non-Residential Building Electrical Meters

Tue, 19 Mar 2019 00:00:00 +0000

As of 2015, there are over 60 million smart meters installed in the United States; these meters are at the forefront of big data analytics in the building industry. However, only a few public data sources of hourly non-residential meter data exist for the purpose of testing algorithms. This paper describes the collection, cleaning, and compilation of several such data sets found publicly on-line, in addition to several collected by the authors. There are 507 whole building electrical meters in this collection, and a majority are from buildings on university campuses. This group serves as a primary repository of open, non-residential data sources that can be built upon by other researchers. An overview of the data sources, subset selection criteria, and details of access to the repository are included. Future uses include the application of new, proposed prediction and classification models to compare performance to previously generated techniques.

Response Spectrum Code-Conforming PEER PBEE using Stochastic Dynamic Analysis and Information Theory

Tue, 19 Mar 2019 00:00:00 +0000

In this paper, the tools of the stochastic dynamic analysis are adopted for Performance-Based Earthquake Engineering (PBEE). The seismic excitation is defined through a evolutionary Power Spectral Density compatible with the response spectrum given by mandatory codes. In this way, the performance-based design is applied considering the excitation coherent with the codes. Inside the framework, the seismic fragility curves are determined through the Kernel Density Maximum Entropy Method (KDMEM), recently proposed by the authors. It is a novel statistical method capable to reconstruct the seismic fragility curves, including the tails, from a small number of code-conforming artificial ground motions. Moreover, KDMEM is based on the Maximum Entropy (ME) principle and it provides the least biased probability distribution given the available information. Comparison between stationary and nonstationary artificial accelerograms is analyzed, and the corresponding model uncertainty discussed....

Predicting success of energy savings interventions and industry type using smart meter and retrofit data from thousands of non-residential buildings

Tue, 19 Mar 2019 00:00:00 +0000

This paper discusses the creation of targeting and segmentation information about non-residential buildings that are equipped with advanced metering infrastructure (AMI) meters, or smart meters. Statistics, model, and pattern-based temporal features are extracted from over 36,000 smart meters. They are then merged with a database of past energy efficiency interventions such as lighting, HVAC, and controls retrof its from 1,600 buildings. The buildings are divided into Good, Average, and Poor performing classes according to consumption from before and after the retrofits. Classification models are developed that improve the ability to predict retrofit success and standard industry class by 18.3% and 27.6% respectively over baselines. This study serves as an example of better leveraging smart meter data from non-residential buildings for utility targeted incentive programs. The methodology outlined is preliminary and further models and temporal features are to be tested.

Unsupervised load shape clustering for urban building performance assessment

Tue, 19 Mar 2019 00:00:00 +0000

This paper presents a method to automatically cluster typical days of energy consumption in one or several buildings. The method is based on an optimized version of the Symbolic Aggregate approXimation (SAX) method. SAX is a data mining technique for clustering time series with recent applications in building fault detection and building performance assessment. The number of clusters and accuracy of SAX highly depends on two highly sensitive input variables, i.e., the word size and the alphabet size. We propose the use of the genetic algorithm NSGA-II to optimize the number of words and alphabet size of SAX subjected to three fitness objectives, i.e., maximize data accuracy and compression and minimize complexity. In addition, we propose the use of MAVT as selection method of the optimal solution. The methodology is applied to measured energy consumption data of three representative buildings on a university campus in Singapore. Potential future uses of the approach include advanced...

Thermal comfort and self-reported productivity in an office with ceiling fans in the tropics

Tue, 19 Mar 2019 00:00:00 +0000

Here we present a field study examining the impact of elevated room temperature and air movement on thermal comfort and self-reported productivity. This experiment was performed in three environmental conditions (one with a set-point of 23 °C—a typical set-point used in Singapore—and two elevated (up to 28 °C) room temperature conditions). Occupants had shared control of ceiling fans.

The results show that the most comfortable thermal condition, with thermal sensation closest to neutral, is achieved at a room temperature of 26 °C with operating fans. Increasing the temperature set-point from 23 °C to 26 °C resulted in a significant increase in thermal acceptability (from 59% to 91%), and a 44 kWh/m2yr savings in electrical energy used for comfort cooling. We found that a room's set-point temperature can be increased up to 27 °C without creating a negative impact when controllable air movement is provided compared to an environment with a set-point of 23 °C. Thermal satisfaction...

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

Mon, 18 Mar 2019 00:00:00 +0000

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...

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

Mon, 18 Mar 2019 00:00:00 +0000

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...

Indoor environmental quality monitoring by autonomous mobile sensing

Mon, 18 Mar 2019 00:00:00 +0000

Indoor environmental quality (IEQ) monitoring is a critical task in building operation, maintenance, and diagnosis. Current approach based on static sensor network is not scalable for IEQ assessment that relies on costly sensing instruments. The study proposes to leverage autonomous mobility to reduce sensing infrastructure cost and enable real-time high-granularity monitoring that can be otherwise inhibitively laborious. Unique to the autonomous mobile sensing methodology, the collected IEQ samples are highly sparse in both spatial and temporal domains. The study develops spatio-temporal (ST) interpolation methods based on ST binning, global trend extraction, and local variation estimation, which efficiently use the data to construct accurate depiction of the indoor environment evolution. The method is evaluated by a standard protocol for ventilation assessment, where the estimation is shown to be highly correlated with the ground truth, and reveals the true ventilation conditions.

Personal thermal comfort models based on physiological parameters measured by wearable sensors

Mon, 18 Mar 2019 00:00:00 +0000

Existing HVAC systems involve little feedback from indoor occupants, resulting in unnecessary cooling/heating waste and high percentage of discomfort. In addition, large thermal preference variance amongst people requires the development of personal thermal comfort models, rather than group-based methodologies such as predicted mean vote (PMV). This study focuses on assessing wearable solutions with the aim to predict personal thermal preference. We collected physiological signals (e.g., skin temperature, heart rate) of 14 subjects (6 female and 8 male adults) and environmental parameters (e.g., air temperature, wind speed, solar radiation, precipitation) for two weeks (at least 20 hr/d) to infer personal real-time thermal preference. The subjects reported their real-time thermal sensation and preference using cell-phones approximately every hour. We trained a Random Forest algorithm using data collected from individuals to develop a personal comfort model with the objective to...

Mining electrical meter data to predict principal building use, performance class, and operations strategy for hundreds of non-residential buildings

Mon, 18 Mar 2019 00:00:00 +0000

This study focuses on the inference of characteristic data from a data set of 507 non-residential buildings. A two-step framework is presented that extracts statistical, model-based, and pattern-based behavior. The goal of the framework is to reduce the expert intervention needed to utilize measured raw data in order to infer information such as building use type, performance class, and operational behavior. The first step is temporal feature extraction, which utilizes a library of data mining techniques to filter various phenomenon from the raw data. This step transforms quantitative raw data into qualitative categories that are presented in heat map visualizations for interpretation. In the second step, a random forest classification model is tested for accuracy in predicting primary space use, magnitude of energy consumption, and type of operational strategy using the generated features. The results show that predictions with these methods are 45.6% more accurate for primary...

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

Fri, 15 Mar 2019 00:00:00 +0000

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....

Hybrid Simulation for Daylighting of Complex Fenestration Systems for Building Envelopes

Fri, 15 Mar 2019 00:00:00 +0000

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.

Experimental and numerical investigations of indoor air movement distribution with an office ceiling fan

Fri, 15 Mar 2019 00:00:00 +0000

Ceiling fans provide cooling to indoor occupants and improve their thermal comfort in warm environments at very low energy consumption. Understanding indoor air distribution associated with ceiling fans helps designs when ceiling fans are used. In this study, we systematically investigate the air movement distribution in an unoccupied office room installed with a ceiling fan, as influenced by (1) fan rotational speed, (2) fan blade geometry, (3) ceiling-to-fan depth, and (4) ceiling height. We both measured and simulated air speeds at four heights in the occupied zone according to ANSI/ASHRAE/IES Standard 55 (2013) for seated and standing occupants. CFD predictions were validated by experimental results. In general, numerical results show that for an unoccupied space, the fan blade geometry, ceiling-to-fan depth, and ceiling height only influence air speed profiles within a cylindrical zone directly under a ceiling fan whose diameter is identical to that of the ceiling fan. However,...

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

Fri, 15 Mar 2019 00:00:00 +0000

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...

Development of Whole‐Building Energy Models for Detailed Energy Insights of a Large Office Building with Green Certification Rating in Singapore

Thu, 14 Mar 2019 00:00:00 +0000

Detailed insights on energy use are missing for the building stock in Singapore that may aid reduction of energy consumption through a targeted approach. Therefore, we created two whole‐building energy models for a large commercial office building in the tropics representing a fully glazed and a concrete façade. We used Singapore's current building codes, which include compliance with local green‐rating system, and collaboration between two entities with first‐hand experience with design, construction, and operation of buildings in the tropics to define the models. The models provide a first step towards a set of standardized inputs and assumptions for office buildings in the tropics. The results show an energy use intensity of 146 kWh m⁻² a⁻¹. The three highest energy consumers are air conditioning and mechanical ventilation (43 %), lighting (29 %), and plug loads (21 %) whereas the two main sources of cooling loads are ventilation (29 %) and conduction...

Effect of Gypsum on the Early Hydration of Cubic and Na-Doped Orthorhombic Tricalcium Aluminate

Thu, 14 Mar 2019 00:00:00 +0000

The tricalcium aluminate (C3A) and sulfate content in cement influence the hydration chemistry, setting time and rheology of cement paste, mortar and concrete. Here, in situ experiments are performed to better understand the effect of gypsum on the early hydration of cubic (cub-)C3A and Na-doped orthorhombic (orth-)C3A. The isothermal calorimetry data show that the solid-phase assemblage produced by the hydration of C3A is greatly modified as a function of its crystal structure type and gypsum content, the latter of which induces non-linear changes in the heat release rate. These data are consistent with the in situ X-ray diffraction results, which show that a higher gypsum content accelerates the consumption of orth-C3A and the subsequent precipitation of ettringite, which is contrary to the cub-C3A system where gypsum retarded the hydration rate. These in situ results provide new insight into the relationship between the chemistry and early-age properties of cub- and orth-C3A...

Detailed experimental investigation of air speed field induced by ceiling fans

Thu, 14 Mar 2019 00:00:00 +0000

Comfort cooling by ceiling fans is cost-effective and energy-efficient compared to compressor-based cooling and fans are commonly used in tropical and subtropical countries. There are however limited data and design tools supporting the design of fan systems, especially for situations where there are multiple fans. In this paper, we investigate airflow profiles induced by a single fan and multiple fans using high spatial resolution air speed measurements (5,760 and 20,160 measuring points for the two cases respectively) in a climatic chamber. To authors' knowledge, this is the first time that interaction between multiple fans has been reported. We developed typical airflow patterns from the measurements and further validated them via smoke visualization. The single-fan results are consistent with previous studies of this configuration, providing additional refinements. For the multiple-fan case, both the difference of fan speed levels and the distance between the fans affect the...

Developing Personal Thermal Comfort Models for the Control of HVAC in Cars Using Field Data

Thu, 14 Mar 2019 00:00:00 +0000

Personal comfort models predict an individual’s thermal comfort instead of the average response for a large population. We attempted to develop personal comfort models for car drivers using data collected from 10 cars while driving for approximately 2,000 hr. We measured conditions collected by the CAN-bus (Controller Area Network), a data acquisition system that is present in most of the modern cars. Data includes information about the in-vehicle thermal conditions, the surrounding environment, the status of the Heating, Ventilation, and Air Conditioning (HVAC) system, and the behavior of the occupant. The objective of the study is to assess the feasibility of inferring occupant’s thermal preference from the data available already available in most cars. By selecting and filtering all the available signals that are relevant for comfort, in this study we map the user actions of turning on/off their seat heating and correlate them to the vehicle indoor and outdoor conditions. The...

Effect of line impedance on electric spring control

Thu, 14 Mar 2019 00:00:00 +0000

Electric spring (ES), a new smart grid technology, has earlier been used for providing voltage and power stability in a weakly regulated/stand-alone renewable energy source powered grid. It has been proposed as a demand-side management technique to provide voltage and power regulation. In this paper, a new control scheme is presented for the implementation of the ES, in conjunction with noncritical building loads like electric heaters, refrigerators, and central air conditioning system. This control scheme would be able to provide power factor correction of the system, voltage support, and power balance for the critical loads, such as the building's security system, in addition to the existing characteristics of ES of voltage and power stability. The proposed control scheme is compared with original ES's control scheme where only reactive power is injected. The improvised control scheme opens new avenues for the utilization of the ES to a greater extent by providing voltage and...

Coordinate control of air movement for optimal thermal comfort

Thu, 14 Mar 2019 00:00:00 +0000

Personally controlled air movement can maintain or enhance thermal comfort in warm environments and reduce energy consumption. Unlike controlling a personal fan, using a system of fans for multiple occupants is difficult as it is hard to find an appropriate fan speed setting that maximizes occupants' satisfaction. Since limited work has been carried out on this issue, in this paper, a novel cooperative control approach for a system of fans is proposed to provide optimized air movement for multiple occupants. This is the first time that a system of fans is controlled cooperatively in the research of built environment. The proposed approach predicts airflow in a cost-effective manner by calibrating the fans in the real environment. The operation of the fans is optimized by minimizing the worst-case deviation between the actual air speed and the desired air speed, which can be determined based on either the PMV – SET model or the occupants' feedback. This minimax-error problem is...

Evaluating energy consumption saving from translucent concrete building envelope

Thu, 14 Mar 2019 00:00:00 +0000

The translucent concrete (TC) as a building envelope can offset some lighting energy that is consumed within a room in an office. It is constructed from concrete panels which are functionalized by embedding optical fibers during the manufacturing phase to transmit sunlight. From preliminary results, a volumetric fiber ratio of 6% used in the TC panel leads to savings in lighting energy by around 50%. The utility of panels is enhanced if it reduces the heating and cooling requirements of the office room. The sunlight channeled by optical fibers can contribute in heating of room during winter but in summer months, it leads to spike in cooling loads. Also, daylight reduces heat dissipation from lighting installations and positively impacts cooling loads. The conduction through walls allows heat to be removed from the room during morning but transmits heat from ambient environment into the room later in the afternoon and evening. The presented research combines thermal and lighting...

Effects of Cement Paste Enhanced with Iron-Based Magnetic Particles on an Embedded Small Resonator Antenna

Thu, 14 Mar 2019 00:00:00 +0000

Small resonator antennas, such as metaresonator antennas, have narrow bandwidths, which limits their effective range of frequencies. When they are used as embedded antennas in building materials, their performance is affected more than other types of antennas, as typical building materials have a shielding effectiveness (SE) of 80 dB to 100 dB. Adding magnetic and/or metallic particles to cement mixes changes the properties of the concrete, which can improve the performance of antennas. Specifically, enhancing a cement paste with iron-based magnetic particles improves the bandwidth and S₁₁ of embedded antennas. This report investigates the impact of two different iron-based magnetic particle sizes (micro- and nanosized particles) to determine the effects that they have on the S₁₁ and S₂₁ characteristics of the metaresonator antenna array embedded in enhanced cement pastes. Results show that compared to cement paste only sample, cement...

Design Automation for Smart Building Systems

Thu, 14 Mar 2019 00:00:00 +0000

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...

Densification of the interlayer spacing governs the nanomechanical properties of calcium-silicate-hydrate

Thu, 14 Mar 2019 00:00:00 +0000

Calciuam-silicate-hydrate (C-S-H) is the principal binding phase in modern concrete. Molecular simulations imply that its nanoscale stiffness is ‘defect-driven’, i.e., dominated by crystallographic defects such as bridging site vacancies in its silicate chains. However, experimental validation of this result is difficult due to the hierarchically porous nature of C-S-H down to nanometers. Here, we integrate high pressure X-ray diffraction and atomistic simulations to correlate the anisotropic deformation of nanocrystalline C-S-H to its atomic-scale structure, which is changed by varying the Ca-to-Si molar ratio. Contrary to the ‘defect-driven’ hypothesis, we clearly observe stiffening of C-S-H with increasing Ca/Si in the range 0.8 ≤ Ca/Si ≤ 1.3, despite increasing numbers of vacancies in its silicate chains. The deformation of these chains along the b-axis occurs mainly through tilting of the Si-O-Si dihedral angle rather than shortening of the Si-O bond, and consequently there...

Context-Aware Plug-Load Identification Towards Enhanced Energy Efficiency in the Built Environment

Wed, 13 Mar 2019 00:00:00 +0000

It is not uncommon to employ energy labeling schemes on appliances or plug-loads that provide information regarding their expected energy usages and efficiencies. But this often does not include a follow-up action of checking whether the expectations on energy consumption are achieved or not for a particular appliance item being used. Automation of this task requires a mechanism that is context-aware regarding meta-data of the appliances (electrical ratings, energy-label information, etc.), and also aware of their operational-data consisting of realtime electrical measurements. In this work, a novel socket hardware is proposed which can access the meta-data and operational-data of appliances in an automated fashion, such that a supervisory control system can contextually identify the plugloads for intelligent demand side management. The proposed smart cyber-physical system would enhance energy efficiency in future buildings, and would also reduce electronic waste.

Bending and Crack Characteristics of Polymer Lattice-Reinforced Mortar

Tue, 12 Mar 2019 00:00:00 +0000

As the construction industry moves toward precast structures, a more mechanically robust concrete is required. To provide joints with higher mechanical toughness, we propose reinforcing the mortar with a polymeric lattice. This study considers the mechanical effects of reinforcing concrete with a polymeric lattice and compares this new technique against the standard fiber-reinforced method. We investigate the octet lattice, which is notable for its high specific strength. Lattices with 23.4 mm unit cells were prototyped out of polylactic acid using a thermoplastic extrusion-based 3D printer. These lattices were placed in a rectangular mold, infiltrated with concrete, and vibrated. The resulting specimens were tested for flexural strength in four-point bending on a hydraulic testing machine. Bending test results show that the lattice-reinforced beams achieve a net deflection at peak load that is 2.5 times greater than that of the fiber-reinforced beams. Further, the lattice-reinforced...

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

Mon, 11 Mar 2019 00:00:00 +0000

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...

Automated mobile sensing: Towards high-granularity agile indoor environmental quality monitoring

Mon, 11 Mar 2019 00:00:00 +0000

Indoor environmental quality (IEQ) is a critical aspect of the built environment to ensure occupant health, comfort, well-being and productivity. Existing IEQ monitoring approaches rely on sensor networks deployed at selected locations to collect environmental measurements, and are limited in scale and adaptability due to infrastructure cost and maintenance requirement. To enable high-granularity IEQ monitoring with agile adaption to the dynamic indoor environment, we propose an “automated mobile sensing” system that dispatches a sensor-rich navigation-capable robot to actively survey the indoor space. Data...

A Luenberger Observer-Based Fault Detection and Identification Scheme for Photovoltaic DC-DC Converters

Mon, 11 Mar 2019 00:00:00 +0000

This paper presents the design, analysis, and experimental validation of a fault detection and identification (FDI) scheme for dc-dc power electronic converters. The FDI scheme includes two new classes of fault filters: (1) a linear-switched fault detection (FD) filter and (2) a bank of linear-switched fault identification (FI) filters. Both the FD filter and the bank of FI filters have a structure similar to that of Luenberger observer. The FD filter detects a fault event and the bank of FI filters identify a faulted converter component, for instance, failure in switching or passive components. We present simulation and experimental results for a prototype 2 kW solar photovoltaic (PV) boost dc-dc converter system to demonstrate the efficacy of the proposed FDI scheme. The experimental results demonstrate accurate fault detection and identification for a collection of catastrophic component faults in PV dc-dc power converters.

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

Tue, 2 Oct 2018 00:00:00 +0000

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...

Nonsolvent-induced phase separation synthesis of superhydrophobic coatings composed of polyvinylidene difluoride microspheres with tunable size and roughness

Tue, 10 Apr 2018 00:00:00 +0000

Polyvinylidene difluoride (PVDF) microspheres are synthesized using the non-solvent induced phase separation (NIPS) method. The diameters of the microspheres are varied from 0.3 μm to 2.8 μm by controlling the amount of water added to a solution of PVDF in dimethylformamide. Sphere aggregatesare created from spun-on films whose thickness is tuned in the range 6.5–16.5 μm by varying the spincasting rotational velocity. Spin-casting with optimized parameters results in high-surface-area films that are among the most superhydrophobic non-templated polymer coatings to date, with water contact anglesup to 171°, hysteresis less than 12°, and slide angle as low as 3°. We model the dependence of sessile water contact angle on the morphological properties of the films, including not only the sphere diameter,but also nanoscale roughness of the microsphere surfaces and the geometries of macroscopic fingers formed by the aggregated spheres.

A nanoporous, ultrahydrophobic aluminum-coating process with exceptional dropwise condensation and shedding properties

Thu, 13 Jul 2017 00:00:00 +0000

Many studies have shown that dropwise condensation can enhance air-side heat transfer coefficients by at least an order of magnitude relative to filmwise condensation. However, among the hundreds of superhydrophobic surface-modification processes previously reported, there remains a lack of coating methods that enable stable dropwise condensation and can be applied to aluminum—by far the most common material for the air side of heat exchangers, e.g. in air conditioning. Here we present a bottom-up synthesis technique to grow zinc oxide-based films on to aluminum with tunable nanoporosity and strongly re-entrant surface features. These surfaces exhibit exceptional static water contact angles of up to 178° with a hysteresis less than 3° and a slide angle of 1°. We have further characterized the surfaces in the presence of six different liquids, and show that our optimal surface can repel even dipropylene glycol with a contact angle of 124°, even though its surface tension is less...

A statistical model for the wettability of surfaces with heterogeneous pore geometries

Wed, 7 Dec 2016 00:00:00 +0000

We describe a new approach to modeling the wetting behavior of micro- and nano-textured surfaces with varying degrees of geometrical heterogeneity. Surfaces are modeled as pore arrays with a Gaussian distribution of sidewall reentrant angles and a characteristic wall roughness. Unlike conventional wettability models, our model considers the fraction of a surface’s pores that are filled at any time, allowing us to capture more subtle dependences of a liquid’s apparent contact angle on its surface tension. The model has four fitting parameters and is calibrated for a particular surface by measuring the apparent contact angles between the surface and at least four probe liquids. We have calibrated the model for three heterogeneous nanoporous surfaces that we have fabricated: a hydrothermally grown zinc oxide, a film of polyvinylidene fluoride (PVDF) microspheres formed by spinodal decomposition, and a polytetrafluoroethylene (PTFE) film with pores defined by sacrificial polystyrene...

WSN-based Intelligent Visual Performance Management in Tropical Buildings

Mon, 1 Aug 2016 00:00:00 +0000

WSN-based Intelligent Visual Performance Management in Tropical Buildings

Dermal Uptake of Organic Vapors Commonly Found in Indoor Air

Mon, 1 Aug 2016 00:00:00 +0000

Dermal Uptake of Organic Vapors Commonly Found in Indoor Air

Evaluation of Climate-Based Daylight Performance in Tropical Office Buildings - A Case Study

Mon, 1 Aug 2016 00:00:00 +0000

Evaluation of Climate-Based Daylight Performance in Tropical Office Buildings - A Case Study

Platform and Algorithm Development for a RFID-Based Indoor Positioning System

Tue, 15 Sep 2015 00:00:00 +0000

In recent years, developing Indoor Positioning System (IPS) has become an attractive research topic due to the increasing demands on Location-Based Service (LBS) in indoor environment. Several advantages of Radio Frequency Identification (RFID) Technology, such as anti-interference, small, light and portable size of RFID tags, and its unique identification of different objects, make it superior to other wireless communication technologies for indoor positioning. However, certain drawbacks of existing RFID-based IPSs, such as high cost of RFID readers and active tags, as well as heavy dependence on the density of reference tags to provide the LBS, largely limit the application of RFID-based IPS. In order to overcome these drawbacks, we develop a cost-efficient RFID-based IPS by using cheaper active RFID tags and sensors. Furthermore, we also proposed three localization algorithms: Weighted Path Loss (WPL), Extreme Learning Machine (ELM) and integrated WPL-ELM. WPL is a centralized...

Exposure to Particulate Matter and Ozone of Outdoor Origin in Singapore

Wed, 10 Jun 2015 00:00:00 +0000

Estimates of population exposure to ambient air pollution traditionally rely on concentrations measured at central-site monitors as a surrogate for concentrations to which people are exposed. In this study of Singapore, we estimate population-averaged exposure concentrations for PM2.5, PM10, and O3 by applying a model and data that account for age and gender demographics, intraurban regional variability, and microenvironmental effects with age- and gender-stratified time-activity budgets. The study addresses exposure only to air pollutants of outdoor origin. Spatially averaged midpoint estimates of lifetime ambient exposure concentrations are 59%, 52%, and 47% of outdoor concentrations for PM2.5, PM10, and O3, respectively. Utilizing ambient data for calendar year 2007, we estimate that intraurban variability in ambient concentration results in lifetime-integrated exposure concentrations in the respective ranges of 10e14 mg m_3 for PM2.5, 14e18 mg m_3 for PM10, and 7.5e15 mg m_3...

Modeling Ozone Removal to Indoor Materials, Including the Effects of Porosity, Pore Diameter, and Thickness

Wed, 10 Jun 2015 00:00:00 +0000

We develop an ozone transport and reaction model to determine reaction probabilities and assess the importance of physical properties such as porosity, porediameter, and material thickness on reactive uptake of ozone to five materials. The one-dimensional model accounts formolecular diffusion from bulk air to the air−material interface, reaction at the interface, and diffusive transport and reaction through material pore volumes. Material-ozone reaction probabilities that account for internal transport and internalpore area, γipa, are determined by a minimization of residuals between predicted and experimentally derived ozone concentrations. Values of γipa are generally less than effective reaction probabilities (γeff) determined previously, likely because of the inclusion of diffusion into substrates and reaction with internal surface area (rather than the use of the horizontally projected external material areas). Estimates of γipa average 1 × 10−7, 2 × 10−7, 4 × 10−5, 2 × 10−5,...

Risk Assessment Scheme of Infection Transmission Indoors Incorporating the Impact of Resuspension

Wed, 10 Jun 2015 00:00:00 +0000

A new risk assessment scheme was developed to quantify the impact of resuspension to infection transmission indoors. Airborne and surface pathogenic particle concentration modelsincluding the effect of two major resuspension scenarios (airflow-induced particle resuspension [AIPR] and walking-induced particle resuspension [WIPR]) were derived based on two-compartment mass balance models and validated against experimental data found in theliterature. The inhalation exposure to pathogenic particles was estimated using the derived airborne concentration model, and subsequently incorporated into a dose-response model to assess the infection risk. Using the proposed risk assessment scheme, the influences of resuspension towards indoor infection transmission were examined by two hypothetical case studies. In the case of AIPR, the infection risk increased from 0 to 0.54 during 0–0.5 hours and from 0.54 to 0.57 during 0.5–4 hours. In the case of WIPR, the infection risk increasedfrom 0...

Particle Exposure during the 2013 Haze in Singapore: Importance of the Built Environment

Wed, 10 Jun 2015 00:00:00 +0000

The 2013 haze was the most serious air pollution event in Singapore's history. Individual exposures to particulate matter differ (a) according to time patterns of behaviour and (b) with the varying degrees of protection provided by buildings against penetration and persistence of outdoor particles. Utilizing realtime personal monitoring, we evaluated exposures to size-segregated fine particulate matter (PM) of five office workers for six days during the latter portion of the 2013 haze event. The outdoor volume concentrations of particulate matter (0.3e2.5 mm diameter) during moderate and light haze days were in the ranges 15e21 mm3/cm3 and 7e10 mm3/cm3, respectively. More than 80% of total daily exposures occurred indoors in workplaces and residences. The daily-integrated personal exposures for the five subjects during the moderate and light haze days were 140e454 (mm3/cm3)-h and 66e239 (mm3/cm3)-h, respectively. Exposure factors for the five participants, quantifying the extent...

Particle Concentration Dynamics in the Ventilation Duct after an Artificial Release: for Countering Potential Bioterriorist Attack

Wed, 10 Jun 2015 00:00:00 +0000

Ventilation duct serves as a potential target for bioterrorist attack. Understanding the dynamics ofaerosolized harmful agents in the ventilation ducts provides the fundamentals for effective control andmanagement, e.g., risk assessment. In this work, new models for predicting the concentration dynam-ics in the ventilation duct after a particle resuspension (representing the case that harmful agents aredosed when the ventilation is off and subsequently being turned on) or puff injection (representing thecase that harmful agents are dosed when the ventilation is running) event were derived based on themass balance model. The models were validated by a series of wind tunnel experiments. Indoor airborneparticle concentration models were derived by incorporating the proposed ventilation duct models forresuspension and injection cases. The effects of resuspension and injection in the duct on indoor airborneparticle concentration were examined by two hypothetical cases of Bacillus anthracis...

Energy and Cost Associated with Ventilating Office Buildings in a Tropical Climate

Wed, 10 Jun 2015 00:00:00 +0000

Providing sufficient amounts of outdoor air to occupants is a critical building function for supporting occupant health, well-being and productivity. In tropical climates, high ventilation rates require substantial amounts of energy to cool and dehumidify supply air. This studyevaluates the energy consumption and associated cost for thermally conditioning outdoor air provided for building ventilation in tropical climates, considering Singapore as an example locale. We investigated the influence on energy consumption and cost of the followingfactors: outdoor air temperature and humidity, ventilation rate (L/s per person), indoor airtemperature and humidity, air conditioning system coefficient of performance (COP), andcost of electricity. Results show that dehumidification of outdoor air accounts for more than 80% of the energy needed for building ventilation in Singapore’s tropical climate. Improved system performance and/or a small increase in the...

New Directions: Potential Climate and Productivity Benefits from CO2 Capture in Commercial Buildings

Wed, 10 Jun 2015 00:00:00 +0000

New Directions: Potential Climate and Productivity Benefits from CO2 Capture in Commercial Buildings

Fusion of WiFi, Smartphone Sensors and Landmarks Using the Kalman Filter for Indoor Localization

Mon, 23 Feb 2015 00:00:00 +0000

Location-based services (LBS) have attracted a great deal of attention recently. Outdoor localization can be solved by the GPS technique, but how to accurately and efficiently localize pedestrians in indoor environments is still a challenging problem. Recent techniques based on WiFi or pedestrian dead reckoning (PDR) have several limiting problems, such as the variation of WiFi signals and the drift of PDR. An auxiliary tool for indoor localization is landmarks, which can be easily identified based on specific sensor patterns in the environment, and this will be exploited in our proposed approach. In this work, we propose a sensor fusion framework for combining WiFi, PDR and landmarks. Since the whole system is running on a smartphone, which is resource limited, we formulate the sensor fusion problem in a linear perspective, then a Kalman filter is applied instead of a particle filter, which is widely used in the literature. Furthermore, novel techniques to enhance the accuracy...

Improved Indoor Tracking Based on Generalized t-Distribution Noise Model

Mon, 23 Feb 2015 00:00:00 +0000

The use of wireless sensor networks for indoor localization application has emerged as a significant area of interest over the last decade, primarily motivated by its low cost and convenient deployment. The weighted centroid localization algorithm is a suitable positioning technique in a wireless sensor network due to its easy implementation. However, the performance of this method is easily affected by outliers and interference in the measurement of radio signal strength. In order to overcome this limitation, a more robust ARMA filter using generalized t-distribution noise model based on influence function approach is proposed. A hardware prototype was implemented to demonstrate that the ARMA filter could improve system performance, especially when dealing with the case of measurement outliers.

Over-Current Protection Scheme for SiC Power MOSFET DC Circuit Breaker

Mon, 23 Feb 2015 00:00:00 +0000

The electronic circuit breaker used in DC microgrids are required to work within their safe operating areas bounded by temperature, voltage and current limits. Traditional approach managed to protect these switches through rapid current cut-off operations at over-load or fault situations, but failing to avoid the disturbance induced by transient current surges or noises which are not harmful to the grid operations. Aiming to increase the quality of circuit breaker operations and furthermore improve its reliability, this paper proposed a SiC MOSFET based DC circuit breaker based on the variable time-delay protection scheme. The cutoff operations only take place after proper delay time, which are precisely catered according to the transient thermal properties of SiC devices and the properties of DC loads. The proposed scheme has been implemented with hardware prototype and experimentally verified under different fault situations.

A Fast and Precise Indoor Localization Algorithm Based on an Online Sequential Extreme Learning Machine

Mon, 23 Feb 2015 00:00:00 +0000

Nowadays, developing indoor positioning systems (IPSs) has become an attractive research topic due to the increasing demands on location-based service (LBS) in indoor environments. WiFi technology has been studied and explored to provide indoor positioning service for years in view of the wide deployment and availability of existing WiFi infrastructures in indoor environments. A large body of WiFi-based IPSs adopt fingerprinting approaches for localization. However, these IPSs suffer from two major problems: the intensive costs of manpower and time for offline site survey and the inflexibility to environmental dynamics. In this paper, we propose an indoor localization algorithm based on an online sequential extreme learning machine (OS-ELM) to address the above problems accordingly. The fast learning speed of OS-ELM can reduce the time and manpower costs for the offline site survey. Meanwhile, its online sequential learning ability enables the proposed localization algorithm to...

Environmental Sensing by Wearable Device for Indoor Activity and Location Estimation

Mon, 8 Dec 2014 00:00:00 +0000

We present results from a set of experiments in this pilot study to investigate the causal influence of user activity on various environmental parameters monitored by occupantcarried multi-purpose sensors. Hypotheses with respect to each type of measurements are verified, including temperature, humidity, and light level collected during eight typical activities: sitting in lab / cubicle, indoor walking / running, resting after physical activity, climbing stairs, taking elevators, and outdoor walking. Our main contribution is the development of features for activity and location recognition based on environmental measurements, which exploit location- and activity-specific characteristics and capture the trends resulted from the underlying physiological process. The features are statistically shown to have good separability and are also information-rich. Fusing environmental sensing together with acceleration is shown to achieve classification accuracy as high as 99.13%. For building applications,...

PresenceSense: Zero-training Algorithm for Individual Presence Detection based on Power Monitoring

Tue, 25 Nov 2014 00:00:00 +0000

Non-intrusive presence detection of individuals in commercial buildings is much easier to implement than intrusive methods such as passive infrared, acoustic sensors, and camera. Individual power consumption, while providing useful feedback and motivation for energy saving, can be used as a valuable source for presence detection. We conduct pilot experiments in an office setting to collect individual presence data by ultrasonic sensors, acceleration sensors, and WiFi access points, in addition to the individual power monitoring data. PresenceSense (PS), a semi-supervised learning algorithm based on power measurement that trains itself with only unlabeled data, is proposed, analyzed and evaluated in the study. Without any labeling efforts, which are usually tedious and time consuming, PresenceSense outperforms popular models whose parameters are optimized over a large training set. The results are interpreted and potential applications of PresenceSense on other data sources are discussed....

Virtual Power Sensing Based on a Multiple-Hypothesis Sequential Test

Tue, 18 Nov 2014 00:00:00 +0000

Virtual-Sensing, which is achieved through the disaggregation of composite power metering signals, is a solution towards achieving fine-grained smart power monitoring. In this work we discuss the challenging issues in Virtual-Sensing, introduce and ultimately combine the Hidden Markov Model and the Edge-based methods. T he resulting solution, based on a Multiple-hypothesis Sequential Probability Ratio Test, combines the advantages of the two methods and delivers significant improvement in disaggregation performance. A robust version of the test is also proposed to filter the impulse noise common in real-time monitoring of the plug-in loads power consumption.

Controlling Energy-Efficient Buildings in the Context of Smart Grid: A Cyber Physical System Approach

Tue, 18 Nov 2014 00:00:00 +0000

The building sector is responsible for about 40% of energy consumption, 40% of greenhouse gas emissions, and 70% of electricity use in the US. Over 50% of the energy consumed in buildings is directly related to space heating, cooling and ventilation. Optimal control of heating, ventilation and air conditioning (HVAC) systems is crucial for reducing energy consumption in buildings.

We present a physics-based mathematical model of thermal behavior of buildings, along with a novel Parameter Adaptive Building (PAB) model framework to update the model parameters, as new measurements arrive, to reduce the model uncertainties. We then present a Model Predictive Control (MPC), and a Robust Model Predictive Control (RMPC) algorithm and a methodology for selecting a controller type, i.e. RMPC or MPC, versus Rule Based Control (RBC) as a function of model uncertainty.

We then address the \Cyber-Physical" aspect of a building HVAC system in the design flow. We present a co-design...

Model Predictive Control with Signal Temporal Logic Specifications