Search results for: Heejin Cho

Items from 1 to 19 out of 19 results

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What is necessary for high employee engagement and satisfaction? A look at the best places to work in the Federal Government Index

Gordon Abner, Arfa Alam, Heejin Cho

Public Administration Review > 83 > 4 > 974 - 981

Governments around the world, including the US federal government, are seeking ways to improve employee engagement, given that it has a positive impact on job performance and organizational performance. Unfortunately, scholars and practitioners have struggled to provide specific and actionable insights for fostering high employee engagement. We describe how data from the Best Places to Work in the...

article

Multi-Objective Particle Swarm Optimization (MOPSO) for a Distributed Energy System Integrated with Energy Storage

Jian Zhang, Heejin Cho, Pedro J. Mago, Hongguang Zhang, more

Journal of Thermal Science > 2019 > 28 > 6 > 1221-1235

Distributed energy systems are considered as a promising technology for sustainable development and have become a popular research topic in the areas of building energy systems. This work presents a case study of optimizing an integrated distributed energy system consisting of combined heat and power (CHP), photovoltaics (PV), and electric and/or thermal energy storage for a hospital and large hotel...

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Integrated photovoltaic and battery energy storage (PV-BES) systems: An analysis of existing financial incentive policies in the US

Jian Zhang, Heejin Cho, Rogelio Luck, Pedro J. Mago

Applied Energy > 2018 > 212 > C > 895-908

This paper presents an analysis of existing financial incentive policies in the U.S. for integrated photovoltaic and battery energy storage (PV-BES) systems. A mathematical model of PV-BES system to evaluate annual energy performance is developed in this paper. Four types of buildings (i.e., hospital, large office, large hotel, and secondary school) located in four different states, which each has...

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Model calibration of a variable refrigerant flow system with a dedicated outdoor air system: A case study

Dongsu Kim, Sam J. Cox, Heejin Cho, Piljae Im

Energy and Buildings > 2018 > 158 > C > 884-896

With increased use of variable refrigerant flow (VRF) systems in the U.S. building sector, interests in capability and rationality of various building energy modeling tools to simulate VRF systems are rising. This paper presents the detailed procedures for model calibration of a VRF system with a dedicated outdoor air system (DOAS) by comparing to detailed measured data from an occupancy emulated...

article

Thermoeconomic multi-objective optimization of a dual loop organic Rankine cycle (ORC) for CNG engine waste heat recovery

Fubin Yang, Heejin Cho, Hongguang Zhang, Jian Zhang

Applied Energy > 2017 > 205 > C > 1100-1118

In this paper, a thermoeconomic model of a dual loop organic Rankine cycle (ORC) system has been developed to analyze both the thermodynamic and economic performance of several working fluid groups for the purpose of compressed natural gas (CNG) engine waste heat recovery. The effects of six key parameters on the thermoeconomic indicators of the dual loop ORC system are investigated. Furthermore,...

article

Optimal design of high temperature metalized thin-film polymer capacitors: A combined numerical and experimental method

Zhuo Wang, Qi Li, Wei Trinh, Qianli Lu, more

Journal of Power Sources > 2017 > 357 > C > 149-157

The objective of this paper is to design and optimize the high temperature metalized thin-film polymer capacitor by a combined computational and experimental method. A finite-element based thermal model is developed to incorporate Joule heating and anisotropic heat conduction arising from anisotropic geometric structures of the capacitor. The anisotropic thermal conductivity and temperature dependent...

article

Transient Uncertainty Analysis in Solar Thermal System Modeling

Heejin Cho, Aaron Smith, Rogelio Luck, Pedro J. Mago

Journal of Uncertainty Analysis and Applications > 2017 > 5 > 1 > 1-15

Complex, dynamic, computational models are routinely used to evaluate and optimize the design and performance of solar thermal systems. As models become more complex, performing uncertainty analysis on such models can be quite challenging and computationally expensive. This paper presents an effective approach to quantify uncertainties associated with transient simulation results from a dynamic solar...

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Field validation study of a time and temperature indexed autoregressive with exogenous (ARX) model for building thermal load prediction

Riasat Sarwar, Heejin Cho, Sam J. Cox, Pedro J. Mago, more

Energy > 2017 > 119 > C > 483-496

Building load prediction algorithms are becoming an essential component of building energy technologies as intelligent building technologies are rapidly evolving and require accurate load predictions to make real-time operational decisions. This paper presents a field validation study of an autoregressive with exogenous (ARX) model, indexed with respect to time and temperature, and used for hourly...

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Evaluation of financial incentives for combined heat and power (CHP) systems in U.S. regions

Jian Zhang, Heejin Cho, Alta Knizley

Renewable and Sustainable Energy Reviews > 2016 > 59 > C > 738-762

In recent years, combined heat and power (CHP) systems have gained more attention from the U.S. government. Both the federal government and the state government have proposed many incentive policies to promote CHP systems. This paper focuses on analyzing and evaluating the effectiveness of existing incentive policies for CHP systems in various U.S. states. In this paper, the existing incentive policies...

article

Design and feasibility study of combined heat and power systems integrated with heat pump

Heejin Cho, Riasat Sarwar, Pedro J. Mago, Rogelio Luck

Applied Thermal Engineering > 2016 > 93 > C > 155-165

This paper presents the design and feasibility analysis of a combined heat and power system integrated with a residential heat pump (CHP-HP). The proposed CHP-HP model consists of a power generation unit (PGU) driving a heat pump and a heat recovery system for the PGU used to offset the heat pump heating load and the domestic water heating requirements. The proposed system is evaluated for a single...

article

Comprehensive modeling of airflow rate through automatic doors for low-rise buildings

Govinda Mahajan, Heejin Cho, Kevin Shanley, Daeho Kang

Building and Environment > 2015 > 87 > C > 72-81

Airflow through doors, depending on function, can have a large impact on building energy consumption and occupant comfort, thus reliable and trustworthy estimation of airflow rate is considered to be an important aspect of building energy modeling and simulation. This paper proposes a comprehensive model that can estimate reliable airflow rate through the different types of automatic doors for low-rise...

article

An Improvement on the Standard Linear Uncertainty Quantification Using a Least-Squares Method

Heejin Cho, Rogelio Luck, James W. Stevens

Journal of Uncertainty Analysis and Applications > 2015 > 3 > 1 > 1-13

Linear uncertainty analysis based on a first order Taylor series expansion, described in ASME PTC (Performance Test Code) 19.1 “Test Uncertainty” and the ISO Guide for the “Expression of Uncertainty in Measurement,” has been the most widely technique used both in industry and academia. A common approach in linear uncertainty analysis is to use local derivative information as a measure of the sensitivity...

article

Combined cooling, heating and power: A review of performance improvement and optimization

Heejin Cho, Amanda D. Smith, Pedro Mago

Applied Energy > 2014 > 136 > C > 168-185

This paper presents a review on combined cooling, heating, and power (CCHP) systems. This work summarizes the methods used to perform energetic and exergetic analyses, system optimization, performance improvement studies, and development and analysis of CCHP systems, as reported in existing literature. In addition, this work highlights the most current research and emerging trends in CCHP technologies...

article

Passive energy management through increased thermal capacitance

Joseph Carpenter, Pedro J. Mago, Rogelio Luck, Heejin Cho

Energy & Buildings > 2014 > 75 > Complete > 465-471

This paper investigates the potential of using passive energy management through increased thermal capacitance (ITC) on the building cooling load by circulating water through a piping system located in the building walls or ceiling and then through a water storage tank. The cooling load obtained from the application of the ITC on the building walls and the ceiling is compared with the cooling load...

article

A probability constrained multi-objective optimization model for CCHP system operation decision support

Mengqi Hu, Heejin Cho

Applied Energy > 2014 > 116 > Complete > 230-242

Due to its capability to reduce carbon dioxide emission and to increase energy efficiency, the combined cooling, heating, and power (CCHP) system has attracted great attention during the last decade. A large number of deterministic and stochastic optimization models have been proposed to study the CCHP operation strategy. However, fewer studies have been conducted to optimize CCHP operation simultaneously...

article

Modeling of reciprocating internal combustion engines for power generation and heat recovery

Kyung Tae Yun, Heejin Cho, Rogelio Luck, Pedro J. Mago

Applied Energy > 2013 > 102 > Complete > 327-335

This paper presents a power generation and heat recovery model for reciprocating internal combustion engines (ICEs). The purpose of the proposed model is to provide realistic estimates of performance/efficiency maps for both electrical power output and useful thermal output for various capacities of engines for use in a preliminary CHP design/simulation process. The proposed model will serve as an...

article

Building hourly thermal load prediction using an indexed ARX model

Kyungtae Yun, Rogelio Luck, Pedro J. Mago, Heejin Cho

Energy & Buildings > 2012 > 54 > Complete > 225-233

This paper introduces an easily implementable and computationally efficient, ARX (autoregressive with exogenous, i.e., external, inputs) time and temperature indexed model for 1h ahead building thermal load prediction. Time and temperature indexing implies that different sets of coefficients are used in the predictive equation depending on the time of the day or the ambient temperature. The indexing...

article

Evaluation of CCHP systems performance based on operational cost, primary energy consumption, and carbon dioxide emission by utilizing an optimal operation scheme

Heejin Cho, Pedro J. Mago, Rogelio Luck, Louay M. Chamra

Applied Energy > 2009 > 86 > 12 > 2540-2549

Optimization of combined cooling, heating, and power (CCHP) systems operation commonly focuses only on energy cost. Different algorithms have been developed to attain optimal utilization of CCHP units by minimizing the energy cost in CCHP systems operation. However, other outcomes resulting from CCHP operation such as primary energy consumption and emission of pollutants should also be considered...

article

Cost-optimized real-time operation of CHP systems

Heejin Cho, Rogelio Luck, Sandra D. Eksioglu, Louay M. Chamra

Energy & Buildings > 2009 > 41 > 4 > 445-451

The Cooling, Heating, and Power (CHP) systems have been widely recognized as a key alternative for thermal and electric energy generation because of the outstanding energy efficiency, reduced environmental emissions, and relative independence from centralized power grids. Nevertheless, the total energy cost of CHP systems can be highly dependent on the operation of individual components. This paper...

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