Large-eddy simulatoin of flow field and pollutant dispession in urban street canyons under unstable atmospheric

Thermal stratification plays an important role in the air flow and pollutant dispersion processes. This study employed a large-eddy simulation (LES) code based on a one-equation subgrid-scale (SGS) model to investigate the flow field and pollutant dispersion characteristics inside urban street canyons. The unstable thermal stratification was simulated by heating the ground level of the street canyons. The thermal buoyancy forces were, using the Boussinesq assumption, taken into account in both the Navier-Stokes equations and the transport equation for SGS turbulent kinetic energy (TKE). The LES had been validated against experimental data obtained in wind tunnel studies before it was applied to study the detailed turbulence and pollutant dispersion characteristics in urban street canyons. The effects of different bulk Richardson number (Rb) were investigated. Several typical temperature differences between the street bottom and ambient air were configured to simulate the scenarios occurring at different times during the day.postprintThe 7th International Conference of Urban Climate (ICUC-7), Yokohama, Japan, 29 June-3 July 2009

Reply to Comment by Velasco on “High-Resolution, Multilayer Modeling of Singapore’s Urban Climate Incorporating Local Climate Zones”

In response to the comment on our paper “High‐resolution, multilayer modeling of Singapore's urban climate incorporating local climate zones,” we provide detailed response to each of the incorrect accusations with scientifically based evidence. We have evaluated our model using all the available observational data, and the results showed good agreement. Our modeling study includes assumptions, as all modeling work does, and we have discussed their rationales and possible implications

Correction: An intrinsically stretchable humidity sensor based on anti-drying, self-healing and transparent organohydrogels

Correction for ‘An intrinsically stretchable humidity sensor based on anti-drying, self-healing and transparent organohydrogels’ by Jin Wu et al., Mater. Horiz., 2019, 6, 595–603, DOI: 10.1039/C8MH01160E

Modeling and Analysis of a Variable Speed Heat Pump for Frequency Regulation Through Direct Load Control

This paper presents a dynamic model of a variable speed heat pump (VSHP) in a commercial building that responds to direct load control (DLC) signals, updated every 4 s, for the improvement of grid frequency regulation (GFR). The model is simplified for real-time simulation studies with the time horizon ranging from seconds to hours, but still sufficiently comprehensive to analyze the operational characteristics such as the heat rate and coefficient of performance. A variable speed drive-controlled induction motor model is also established for the adjustment of the VSHP input power. A dynamic model of an experimental room is then developed to estimate the effect of the DLC application to the VSHP on its indoor air temperature for two different cooling systems. Furthermore, small signal analysis is performed to evaluate both the transient response of the DLC-enabled VSHP and its contribution to GFR. Finally, with an isolated microgrid implemented with MATLAB/SIMULINK, simulation studies demonstrate that the VSHP can be effectively exploited as the DLC-enabled load while still ensuring building occupant comfort and long-term device performance.113126sciescopu

Experimental Study of Grid Frequency Regulation Ancillary Service of a Variable Speed Heat Pump

This paper describes an analysis of a variable speed heat pump (VSHP), which responds to direct load control (DLC) signals to provide grid frequency regulation (GFR) ancillary service, while ensuring the comfort of building occupants. A data-driven dynamic model of the VSHP is developed through real-time experimental studies with a time horizon ranging from seconds to hours. The model is simple, yet still sufficiently comprehensive to analyze the operational characteristics of the VSHP. The DLC scheme is then experimentally applied to the VSHP to evaluate its demand response (DR) capability. Two control methods are considered for a practical implementation of the DLC-enabled VSHP and a further improvement of the DR capability, respectively. Additionally, a small-signal analysis is carried out using the aggregated dynamic response of a number of DLC-enabled VSHPs to analyze their contribution to GFR in an isolated power grid. For experimental case studies, a laboratory-scale microgrid is then implemented with generator and load emulators. We show that the DLC-enabled VSHP can effectively reduce grid frequency deviations and required reserve capacities of generators.112012sciescopu

Technologies and Magnitude of Ancillary Services Provided by Commercial Buildings

Commercial buildings increasingly include technologies capable of providing ancillary services to electric power grids. Features include thermal energy storage inherent in building structures that can be coupled to electric grids through heating, ventilating, and air-conditioning (HVAC) systems controlled by variable-speed drives (VSDs). In parking garages, plug-in electric vehicles (PEVs) are connected to the building power lines through charging stations and can be utilized as grid storage. System power electronics can control equipment power demand at frequencies associated with ancillary services procured in electricity markets, where services dispatch over time scales ranging from hours to seconds. Limitations in provision of services by buildings include building-scale thermal and electrical energy storage capacities: thermal comfort of occupants, state of charge of PEV batteries, and the power rating of VSDs and PEV chargers. This paper reviews available technologies and necessary control strategies for HVAC systems in commercial buildings to provide ancillary services. We then develop physically-based scaling metrics for building thermal storage technologies accessible through HVAC systems. In addition, the effect of ancillary services provided by HVAC systems on grid network and electricity market operations is analyzed using simulation case studies, incorporating magnitude scaling of services. We finally evaluate a possibility that the HVAC systems and PEVs provide three-phase voltage and power balance regulation services, respectively.1164sciescopu

Acoustic and device feature fusion for load recognition

Appliance-specific Load Monitoring (LM) provides a possible solution to the problem of energy conservation which is becoming increasingly challenging, due to growing energy demands within offices and residential spaces. It is essential to perform automatic appliance recognition and monitoring for optimal resource utilization. In this paper, we study the use of non-intrusive LM methods that rely on steady-state appliance signatures for classifying most commonly used office appliances, while demonstrating their limitation in terms of accurately discerning the low-power devices due to overlapping load signatures. We propose a multi-layer decision architecture that makes use of audio features derived from device sounds and fuse it with load signatures acquired from energy meter. For the recognition of device sounds, we perform feature set selection by evaluating the combination of time-domain and FFT-based audio features on the state of the art machine learning algorithms. Further, we demonstrate that our proposed feature set which is a concatenation of device audio feature and load signature significantly improves the device recognition accuracy in comparison to the use of steady-state load signatures only

Integrated Assessment of Urban Overheating Impacts on Human Life

10.1029/2022EF002682EARTHS FUTURE10