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Feng, Fan

Publications and source records attributed to Feng, Fan.

6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Enhancement of phase change material hysteresis model: A case study of modeling building envelope in EnergyPlus

Nowadays, buildings are expected to offer demand side services to the power grid to enhance the electrical load flexibility, which leads to the concepts of grid-interactive efficient buildings (GEBs). Phase change material (PCM)-based thermal energy storage has seen increasing attention in recent years for peak load shifting of grid-interactive efficient buildings (GEBs). Numerical models are critical tools for design and evaluation of PCM-integrated systems. Most industrial-grade PCMs are reported to melt/freeze over a temperature range instead of at a unique temperature. Such thermal hysteresis effect significantly affects the reliability of simulation results because not only the heat transfer process depends on melting and freezing temperatures, the PCM thermal properties change significantly during the phase change process as well. This study is aimed to develop a model for the PCMs used in the building envelope with the capability to accurately simulate hysteretic behaviors. Further, this model is based on a two-phase assumption and is implemented in a whole building energy performance simulation program (i.e., EnergyPlus). A comparison between numerical results and experimental data shows that during a complete phase transition, the two-phase model could achieve a good agreement with the experimental data. During a partial phase transition, the two-phase model could lead to significant improvements compared to other alternative PCM models, including the existing PCM model in EnergyPlus. Last, whole building simulations were performed to study this model's performance regarding heating/cooling loads and zone mean air temperature of a given building. The results show that the difference in hourly heating/cooling loads introduced by the models was less than 1% in design conditions, while significant changes were observed in both hourly heating/cooling loads and zone mean air temperature when the PCM envelope underwent partial phase transition processes.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2019

Enhanced Electrochemical Performance of Sodium Manganese Ferrocyanide by Na 3 (VOPO 4 ) 2 F Coating for Sodium-Ion Batteries

Sodium manganese ferrocyanide Na x Mn[Fe(CN) 6 ] y is an attractive cathode material for sodium-ion batteries. However, NaxMn[Fe(CN) 6 ] y prepared by simple coprecipitation of Mn 2+ and [Fe(CN) 6 ] 4– usually shows poor cycling performance, which hinders its practical application. In this work, electrochemical performance of a Na 1.6 Mn[Fe(CN) 6 ] 0.9 (PBM) sample prepared by the simple precipitation method was greatly improved by coating with Na 3 (VOPO 4 ) 2 F (NVOPF) via a solution precipitation method. The as-prepared PBM@NVOPF with a coating quantity of 2.0% molar ratio showed enhanced rate capability and superior cyclic stability. The discharge capacities of PBM@NVOPF were 101.5 mA h g –1 (1 C) and 91.4 mA h g –1 (10 C), with a capacity retention of 84.3% after 500 cycles at 1 C, 20 °C. It also exhibited excellent cyclic stability at elevated temperature with an initial capacity of 109.5 mA h g –1 and a capacity retention of 78.8% after 200 cycles at 1 C, 55 °C. In comparison, uncoated PBM showed a discharge capacity of 105.7 mA h g–1 (1 C) and 76.7 mA h g –1 (10 C), with a capacity retention of only 42.0% after 500 cycles at 1 C, 20 °C. The high-temperature performance of bare PBM was very poor, and the capacity retention was only 35.7% after 40 cycles because of serious Mn/Fe dissolution which caused structural deterioration of PBM. NVOPF coating protected the PBM from suffering corrosion in the electrolyte, thus ensured the framework stability of PBM during long-term cycling and contributed to the excellent electrochemical performance.

25 ENERGY STORAGE↗
DOE OSTI2019

A review of smart building sensing system for better indoor environment control

Here this paper aims to provide a systemic review of how indoor sensors influence in managing optimal energy saving, thermal comfort, visual comfort, and indoor air quality in the built environment. The optimal management of energy saving and occupant comfort plays a vital role in the built environment because the occupant's productivity and health are highly influenced by indoor environmental quality. In order to do this, there must be a functional sensing system that connects the environment variables (e.g., temperature) with building environmental control systems such as the heating, ventilation, and air-conditioning system. This paper starts with an overview of the importance of energy saving and occupant comfort in the built environment. It then discusses sensors and their importance in the built environment and reviews the different types of sensors, which explains them in terms of how they influence the indoor built environment and occupant productivity. The paper further explores the application of sensors in the built environment and analyzes this in terms of energy saving, thermal comfort, visual comfort, and indoor air quality. Following this, the data analysis is discussed in terms of data, information, and knowledge accrued from the sensors. Lastly, the paper discusses the future challenges for the improvement of building indoor environmental quality and energy saving by the application of sensors.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2018

Electrochemical Performance of NaFeFe(CN) 6 Prepared by Solid Reaction for Sodium Ion Batteries

Commercially available Na 4 Fe(CN) 6 and Fe 4 [Fe(CN) 6 ] 3 are two cheap compounds that have ever been investigated as positive electrode materials for sodium-ion batteries. However, poor electronic conductivity of Na 4 Fe(CN) 6 and sodium deficiency of Fe 4 [Fe(CN) 6 ] 3 prevent these two materials from being used in practical rechargeable sodium-ion batteries. In this paper, a NaFeFe(CN) 6 cathode material was synthesized by ball milling the Fe 4 [Fe(CN) 6 ] 3 / Na 4 Fe(CN) 6 mixture. The obtained NaFeFe(CN) 6 demonstrated a single cubic phase indexed to Fm3m space group similar to Fe 4 [Fe(CN) 6 ] 3 but with larger lattice parameter due to the existence of Na + in the lattice framework. The NaFeFe(CN) 6 electrode delivered first desodiation capacity of 119.4 mAh g -1 and first sodiation capacity of 153.6 mAh g -1 at 0.05C rate. The NaFeFe(CN) 6 showed excellent cycling stability with reversible capacities of 118.2 mAh g -1 and 96.8 mAh g -1 at 0.1C and 1C rate, respectively. In-situ XRD analyses demonstrated a single cubic phase process during charge-discharge of NaFeFe(CN) 6 electrode. Low water content benefited from the solid reaction method and the homogenous single phase process during charge/discharge assured the stable long term cycling performance of the NaFeFe(CN) 6 product.

25 ENERGY STORAGE↗