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Heejin Cho
Institute for Clean Energy Technology, Mississippi State University, 205 Research Blvd, Starkville, MS, 39759, USA

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Review
Published: 28 July 2021 in Environmental Research
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COVID-19 forced the human population to rethink its way of living. The threat posed by the potential spread of the virus via an airborne transmission mode through ventilation systems in buildings and enclosed spaces has been recognized as a major concern. To mitigate this threat, researchers have explored different technologies and methods that can remove or decrease the concentration of the virus in ventilation systems and enclosed spaces. Although many technologies and methods have already been researched, some are currently available on the market, but their effectiveness and safety concerns have not been fully investigated. To acquire a broader view and collective perspective of the current research and development status, this paper discusses a comprehensive review of various workable technologies and methods to combat airborne viruses, e.g., COVID-19, in ventilation systems and enclosed spaces. These technologies and methods include an increase in ventilation, high-efficiency air filtration, ionization of the air, environmental condition control, ultraviolet germicidal irradiation, non-thermal plasma and reactive oxygen species, filter coatings, chemical disinfectants, and heat inactivation. Research gaps have been identified and discussed, and recommendations for applying such technologies and methods have also been provided in this article.

ACS Style

Gentry Berry; Adam Parsons; Matthew Morgan; Jaime Rickert; Heejin Cho. A review of methods to reduce the probability of the airborne spread of COVID-19 in ventilation systems and enclosed spaces. Environmental Research 2021, 203, 111765 -111765.

AMA Style

Gentry Berry, Adam Parsons, Matthew Morgan, Jaime Rickert, Heejin Cho. A review of methods to reduce the probability of the airborne spread of COVID-19 in ventilation systems and enclosed spaces. Environmental Research. 2021; 203 ():111765-111765.

Chicago/Turabian Style

Gentry Berry; Adam Parsons; Matthew Morgan; Jaime Rickert; Heejin Cho. 2021. "A review of methods to reduce the probability of the airborne spread of COVID-19 in ventilation systems and enclosed spaces." Environmental Research 203, no. : 111765-111765.

Preprint content
Published: 16 July 2021
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ACS Style

Hadis Hemmati; Jian Zhang; Emily Spayde; Pedro Mago; Heejin Cho. Performance Analysis of a Solar Powered Organic Rankine Cycle With Energy Storage in Different Climate Zones in the United States. 2021, 1 .

AMA Style

Hadis Hemmati, Jian Zhang, Emily Spayde, Pedro Mago, Heejin Cho. Performance Analysis of a Solar Powered Organic Rankine Cycle With Energy Storage in Different Climate Zones in the United States. . 2021; ():1.

Chicago/Turabian Style

Hadis Hemmati; Jian Zhang; Emily Spayde; Pedro Mago; Heejin Cho. 2021. "Performance Analysis of a Solar Powered Organic Rankine Cycle With Energy Storage in Different Climate Zones in the United States." , no. : 1.

Journal article
Published: 05 February 2021 in Journal of Energy Resources Technology
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Solar-powered organic Rankine cycle (ORC) is considered a promising technology and has the potential to provide clean electric energy. Extensive studies on the design of ORC systems have been conducted and reported in the literature. However, few studies have presented the influence of climate zones on the performance of a solar-powered ORC, especially for an integrated ORC and energy storage system. This paper presents an analysis to determine the performance of solar-powered ORCs with electric energy storage (EES) systems to supply electricity to buildings in different climate zones in the United States. The building type evaluated in this paper is a large office, and the energy consumption of the facility in each climate location was determined using EnergyPlus. The ORC-EES operational strategy used in this investigation is described as follows: when solar irradiation is adequate to produce power, the ORC charges the EES. Then, when there is no solar energy available, the EES provides power to the building. The ORC-EES is evaluated based on the potential to reduce the operational cost, the primary energy consumption, and the carbon dioxide emission. Furthermore, the influence of the number of solar collectors and the EES size on the performance of the ORC-EES system is investigated.

ACS Style

Hadis Hemmati; Jian Zhang; Emily Spayde; Pedro J. Mago; Heejin Cho. Performance Analysis of Solar-Powered Organic Rankine Cycle With Energy Storage in Different Climate Zones in the United States. Journal of Energy Resources Technology 2021, 143, 1 -24.

AMA Style

Hadis Hemmati, Jian Zhang, Emily Spayde, Pedro J. Mago, Heejin Cho. Performance Analysis of Solar-Powered Organic Rankine Cycle With Energy Storage in Different Climate Zones in the United States. Journal of Energy Resources Technology. 2021; 143 (9):1-24.

Chicago/Turabian Style

Hadis Hemmati; Jian Zhang; Emily Spayde; Pedro J. Mago; Heejin Cho. 2021. "Performance Analysis of Solar-Powered Organic Rankine Cycle With Energy Storage in Different Climate Zones in the United States." Journal of Energy Resources Technology 143, no. 9: 1-24.

Journal article
Published: 29 January 2021 in Renewable and Sustainable Energy Reviews
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Homeowners across the globe are continually seeking methods of improving energy efficiency for financial benefit and personal satisfaction. From small contributions such as swapping light bulbs to large capital investment initiatives like upgraded heating and cooling systems, homeowner decisions require accurate data and confidence in potential outcomes. This study models the path to net-zero energy for two separate heating, ventilation and air conditioning (HVAC) plus solar photovoltaic (PV) systems in residential buildings across 12 Unites States climate zones, and determines the optimal combination for each climate zone. An existing, traditional air-conditioning system with natural gas furnace is paired with a PV array. The net-zero results are compared to the same residence upgraded to a climate-customized geothermal heat pump HVAC system paired with a PV array. Results confidently favor the geothermal HVAC system + PV for climates with a significant heating demand in winter, and the baseline + PV system for cooling-dominant climates, exceeding $3,900 and $3,500 annual household savings, respectively. A major contribution is the introduction of a template that predicts the net-zero system option for climate zones outside the 12 studied. Patterns in local soil properties, sun intensity and financial incentives allow for net-zero system predictions nationwide. For example, all locations resulting in a baseline + PV net-zero system have strong sun intensity ratings. This research delivers climate-specific recommendations for the preferred net-zero HVAC + PV system through analysis of accurate energy performance and financial forecasting. Recommendations provide homeowners with valuable expectations on two HVAC + PV options along the path to a net-zero energy home.

ACS Style

Rebecca Neves; Heejin Cho; Jian Zhang. Pairing geothermal technology and solar photovoltaics for net-zero energy homes. Renewable and Sustainable Energy Reviews 2021, 140, 110749 .

AMA Style

Rebecca Neves, Heejin Cho, Jian Zhang. Pairing geothermal technology and solar photovoltaics for net-zero energy homes. Renewable and Sustainable Energy Reviews. 2021; 140 ():110749.

Chicago/Turabian Style

Rebecca Neves; Heejin Cho; Jian Zhang. 2021. "Pairing geothermal technology and solar photovoltaics for net-zero energy homes." Renewable and Sustainable Energy Reviews 140, no. : 110749.

Journal article
Published: 19 January 2021 in Climate
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This paper presents an analysis to foresee renewable design requirement changes of net- zero carbon buildings (NZCBs) under different scenarios of potential future climate scenarios in the U.S. Northeast and Midwest regions. A climate change model is developed in this study using the Gaussian random distribution method with monthly temperature changes over the whole Northeast and Midwest regions, which are predicted based on a high greenhouse gas (GHG) emission scenario (i.e., the representative concentration pathways (RCP) 8.5). To reflect the adoption of NZCBs potential in future, this study also considers two representative future climate scenarios in the 2050s and 2080s of climate change years in the U.S. Northeast and Midwest regions. An office prototype building model integrates with an on-site photovoltaics (PV) power generation system to evaluate NZCB performance under the climate change scenarios with an assumption of a net-metering electricity purchase agreement. Appropriate capacities of the on-site PV system needed to reach NZCB balances are determined based on the building energy consumption impacted by the simulated climate scenarios. Results from this study demonstrated the emission by electricity consumption increases as moving toward the future scenarios of up to about 25 tons of CO2-eq (i.e., about 14% of the total CO2-eq produced by the electricity energy source) and the PV installation capacity to offset the emission account for the electricity consumption increases significantly up to about 40 kWp (i.e., up to more than 10% of total PV installation capacities) as the different climate scenarios are applied. It is concluded that the cooling energy consumption of office building models would significantly impact GHG emission as future climate scenarios are considered. Consequently, designers of NZCBs should consider high performance cooling energy systems in their designs to reduce the renewable energy generation system capacity to achieve net-zero carbon emission goals.

ACS Style

Dongsu Kim; Heejin Cho; Pedro J. Mago; Jongho Yoon; HyoMun Lee. Impact on Renewable Design Requirements of Net-Zero Carbon Buildings under Potential Future Climate Scenarios. Climate 2021, 9, 17 .

AMA Style

Dongsu Kim, Heejin Cho, Pedro J. Mago, Jongho Yoon, HyoMun Lee. Impact on Renewable Design Requirements of Net-Zero Carbon Buildings under Potential Future Climate Scenarios. Climate. 2021; 9 (1):17.

Chicago/Turabian Style

Dongsu Kim; Heejin Cho; Pedro J. Mago; Jongho Yoon; HyoMun Lee. 2021. "Impact on Renewable Design Requirements of Net-Zero Carbon Buildings under Potential Future Climate Scenarios." Climate 9, no. 1: 17.

Journal article
Published: 17 January 2021 in Sustainability
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Advancements in computer and mobile technologies have driven transformations of classroom activities in engineering education. This evolution provides instructors more opportunities to introduce computational tools that can be effectively used and promoted in engineering education to advance students’ learning process when the tools are appropriately utilized in the classroom activities. This paper presents a methodology to improve student learning of energy systems through a class assignment implementing a self-developed computational tool using Microsoft Excel and utilizing the tool to enhance their learning experience. The proposed method, a student-centered learning approach, was applied in a technical elective course called “Power Generation Systems” within a mechanical engineering curriculum. In the course, students were guided to develop a computational tool by themselves based on their learning of the fundamental principles and governing equations of a thermodynamics cycle. The self-developed computational tool allows the students to focus on more design-oriented problems, instead of the calculation process. Using the self-developed tool, students can have an enhanced understanding of the energy system performance in varying design and operational conditions and can perform the parametric analysis and visualization of essential parameters. Feedback from the students and class instructors proves that the self-development and use of the tool can significantly improve the students’ learning experience in the implemented course, make the course more dynamic, and motivate the students to learn the material more iteratively. In addition, students feel confident using computational tools to perform analysis, and are willing to develop more tools for other energy-related engineering applications.

ACS Style

Jian Zhang; Heejin Cho; Pedro Mago. Improving Student Learning of Energy Systems through Computational Tool Development Process in Engineering Courses. Sustainability 2021, 13, 884 .

AMA Style

Jian Zhang, Heejin Cho, Pedro Mago. Improving Student Learning of Energy Systems through Computational Tool Development Process in Engineering Courses. Sustainability. 2021; 13 (2):884.

Chicago/Turabian Style

Jian Zhang; Heejin Cho; Pedro Mago. 2021. "Improving Student Learning of Energy Systems through Computational Tool Development Process in Engineering Courses." Sustainability 13, no. 2: 884.

Journal article
Published: 24 October 2020 in Renewable and Sustainable Energy Reviews
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Geothermal residential heating and cooling systems have undeniable potential savings. The possibilities of the energy savings with a geothermal heat pump system is well-established in the commercial and residential sectors. Building location has a critical impact on the performance of geothermal heat pump systems and magnitude of savings. An important contribution of this paper takes the step past technological optimization to investigate 12 climate zones across the contiguous United States. Residential homes within common neighborhoods are thoroughly analyzed by considering soil characteristics and home construction features. Within these climate zones, federal and all local incentive programs are quantified to determine an accurate expectation for capital investment payback period, a critical factor for system attractability. Ultimately, a climate zone is classified as either a promising or poor candidate for residential geothermal technology based on data from previously conducted human interest polls regarding payback period on energy savings investments. With such lasting potential delivered to the hands of consumers, geothermal energy use still experiences slow implementation. This paper conducts a study integrating data on technology, finances, and human nature to identify the prevailing barrier to widespread geothermal execution. Solid evidence on energy and monetary savings reveals the dominant barriers are initial capital investment and long payback period. This paper highlights the immense positive impact that local incentives have on affecting these two prevailing deterrents.

ACS Style

Rebecca Neves; Heejin Cho; Jian Zhang. State of the nation: Customizing energy and finances for geothermal technology in the United States residential sector. Renewable and Sustainable Energy Reviews 2020, 137, 110463 .

AMA Style

Rebecca Neves, Heejin Cho, Jian Zhang. State of the nation: Customizing energy and finances for geothermal technology in the United States residential sector. Renewable and Sustainable Energy Reviews. 2020; 137 ():110463.

Chicago/Turabian Style

Rebecca Neves; Heejin Cho; Jian Zhang. 2020. "State of the nation: Customizing energy and finances for geothermal technology in the United States residential sector." Renewable and Sustainable Energy Reviews 137, no. : 110463.

Article
Published: 17 December 2019 in Journal of Thermal Science
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Oscillating heat pipes (OHP) which are constructed from a serpentine-arranged capillary tube possess a desirable aerodynamic form factor and provide for relatively high heat transfer rates via cyclic evaporation and condensation of an encapsulated working fluid with no internal wicking structure required. In last two decades, OHP has been extensively investigated for its potential application in thermal management of various applications. This study presents an experimental investigation on the heat transfer performance of an atypically long finned OHP. The heat transfer performance of the proposed OHP was analyzed and compared with a bare tube OHP with similar overall dimensions. Results show that a unit row of finned OHP filled with n-pentane with fill ratio of 70% can recover up to (400±40) W of heat from a typical waste exhaust air stream. The additional pressure drop due to fins was estimated to be (6.8±2) Pa resulting in an increase of 1–2 W of fan power consumption. The average heat recovery rate via finned OHP was found to be almost 80% more than bare tube OHP filled with same working fluid with same fill ratio.

ACS Style

Govinda Mahajan; Heejin Cho; Aaron Smith; Scott M. Thompson. Experimental Analysis of Atypically Long Finned Oscillating Heat Pipe for Ventilation Waste Heat Recovery Application. Journal of Thermal Science 2019, 29, 667 -675.

AMA Style

Govinda Mahajan, Heejin Cho, Aaron Smith, Scott M. Thompson. Experimental Analysis of Atypically Long Finned Oscillating Heat Pipe for Ventilation Waste Heat Recovery Application. Journal of Thermal Science. 2019; 29 (3):667-675.

Chicago/Turabian Style

Govinda Mahajan; Heejin Cho; Aaron Smith; Scott M. Thompson. 2019. "Experimental Analysis of Atypically Long Finned Oscillating Heat Pipe for Ventilation Waste Heat Recovery Application." Journal of Thermal Science 29, no. 3: 667-675.

Journal article
Published: 14 October 2019 in Journal of Building Engineering
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The residential building sector in the United States relies prolifically on electric cooling and natural gas heating, ventilating, and air conditioning systems. Technology advancement for more energy efficient and cost-effective energy systems is continuous, and a geothermal energy system is an attractive alternative to electricity and natural gas. This study investigates a simulated residential building in Memphis, Tennessee (TN) to assess the energy savings by replacing the existing electric/gas system with a geothermal heat pump system. Further, economics are considered to examine the payoff period and ultimate viability for geothermal technology in this region. EnergyPlus™, the U.S. Department of Energy (DOE) whole building simulation engine, analyzed a prototype home in Memphis, TN with this common utility system. City-specific ground characteristics are used to customize the ground heat exchanger and optimize result accuracy. Simulations reveal that replacing the existing system with a geothermal system accomplishes a 26% reduction in energy use. Our results prove an exciting alternative for homes in Memphis, TN to achieve abundant energy savings. Despite lower meter readings, a homeowner must consider initial capital investment and payoff period. This study provides city-customized payoff data by using local ground characteristics for design, location-specific home features, and regional plus federal incentive programs. Methods used within create a unique and accurate template procedure for identifying promising regions for residential geothermal systems throughout the broader United States.

ACS Style

Rebecca Neves; Heejin Cho; Jian Zhang. Techno-economic analysis of geothermal system in residential building in Memphis, Tennessee. Journal of Building Engineering 2019, 27, 100993 .

AMA Style

Rebecca Neves, Heejin Cho, Jian Zhang. Techno-economic analysis of geothermal system in residential building in Memphis, Tennessee. Journal of Building Engineering. 2019; 27 ():100993.

Chicago/Turabian Style

Rebecca Neves; Heejin Cho; Jian Zhang. 2019. "Techno-economic analysis of geothermal system in residential building in Memphis, Tennessee." Journal of Building Engineering 27, no. : 100993.

Journal article
Published: 27 August 2019 in Sustainable Energy Technologies and Assessments
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This research explores the design and operation of an increased thermal capacitance (ITC) and thermal storage management (TSM) system for reducing building energy consumption associated with heating, cooling, and domestic hot water (DHW) usage. Thermal capacitance is a controlling factor for phase shift and amplitude reductions of cyclical heat transfer due to weather, and control of the ITC through TSM improves upon the benefits offered by additional capacitance. Using the transient energy modeling software TRNSYS, ITC is achieved by water circulating in copper pipes embedded in the walls of a three-story residential building. Temperature and season-controlled valves divert circulation to either the building shell, ground heat exchanger, solar panel, cold storage tank or hot storage tank. A phase change material is thoroughly mixed into the water storage tanks to allow a tank volume reduction without loss of thermal storage. Proper design and operation of the ITC/TSM system are investigated through a parametric study of the water tank size, water mass flowrate, and solar panel size. These analyses are focused on reducing the overall building energy requirement associated with the heat pump and DHW usage. Results range from 24% to 35% energy savings for the evaluated parameter ranges.

ACS Style

Mary Wilson; Heejin Cho; Pedro J. Mago. Design and operation of increased thermal capacitance and dual thermal storage and its effects on building energy dependence. Sustainable Energy Technologies and Assessments 2019, 35, 354 -364.

AMA Style

Mary Wilson, Heejin Cho, Pedro J. Mago. Design and operation of increased thermal capacitance and dual thermal storage and its effects on building energy dependence. Sustainable Energy Technologies and Assessments. 2019; 35 ():354-364.

Chicago/Turabian Style

Mary Wilson; Heejin Cho; Pedro J. Mago. 2019. "Design and operation of increased thermal capacitance and dual thermal storage and its effects on building energy dependence." Sustainable Energy Technologies and Assessments 35, no. : 354-364.

Article
Published: 24 August 2019 in Journal of Thermal Science
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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 buildings located in Texas and California. First, simulation models for all subsystems, which are developed individually, are integrated together according to a control strategy designed to satisfy both the electric and thermal energy requirements of a building. Subsequently, a multi-objective particle swarm optimization (MOPSO) is employed to obtain an optimal design of each subsystem. The objectives of the optimization are to minimize the simple payback period (PBP) and maximize the reduction of carbon dioxide emissions (RCDE). Finally, the energy performance for the selected building types and locations are analyzed after the optimization. Results indicate that the proposed optimization method could be applied to determine an optimal design of distributed energy systems, which reaches a trade-off between the economic and environmental performance for different buildings. With the presented distributed energy system, a peak shaving in electricity of about 300 kW and a reduction in boiler fuel consumption of 610 kW could be attained for the hospital building located in California for a winter day. For the summer and transition seasons, electricity peak shaving of 800 kW and 600 kW could be achieved, respectively.

ACS Style

Jian Zhang; Heejin Cho; Pedro J. Mago; Hongguang Zhang; Fubin Yang. Multi-Objective Particle Swarm Optimization (MOPSO) for a Distributed Energy System Integrated with Energy Storage. Journal of Thermal Science 2019, 28, 1221 -1235.

AMA Style

Jian Zhang, Heejin Cho, Pedro J. Mago, Hongguang Zhang, Fubin Yang. Multi-Objective Particle Swarm Optimization (MOPSO) for a Distributed Energy System Integrated with Energy Storage. Journal of Thermal Science. 2019; 28 (6):1221-1235.

Chicago/Turabian Style

Jian Zhang; Heejin Cho; Pedro J. Mago; Hongguang Zhang; Fubin Yang. 2019. "Multi-Objective Particle Swarm Optimization (MOPSO) for a Distributed Energy System Integrated with Energy Storage." Journal of Thermal Science 28, no. 6: 1221-1235.

Journal article
Published: 29 March 2019 in Journal of Energy Resources Technology
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This special issue of the ASME Journal of Energy Resources Technology is devoted to the ASME 12th International Conference on Energy Sustainability held in Lake Buena Vista, FL, June 24-28, 2018. For more than 10 years, the conference has been a place for researchers all over the world and from various sectors to share their innovative ideas and research progress. The conference in 2018 was sponsored by the Advanced Energy System Division and the Solar Energy Division, and co-located with the ASME Power Conference as well as the ASME Nuclear Forum. The conference included 14 parallel tracks on the broad topic of renewable/sustainable energy, including Nexus: Energy/Water/Climate/Food (new); Smart & Cyber-Physical Systems (new); Geothermal Technologies; Conversion and Processing of Biofuel and Alternative Fuel; Distributed Energy Systems; Sustainability & Society (new); Thermal and Mechanical Energy Storage; Sustainable Building Energy Systems; Photovoltaics; and Wind Energy Systems & Technologies. We are particularly excited to introduce the three new tracks, which have not received enough attention or did not have a proper place for presentation in the research community. In order to highlight innovative research outcomes and enhance public visibility, we have invited high quality papers out of 187 presentations to be included in this special issue.

ACS Style

Hohyun Lee; Reza Baghaei Lakeh; Guangdong Zhu; Heejin Cho; Omid Askari. Special Issue for the 12th International Conference on Energy Sustainability (ES2018). Journal of Energy Resources Technology 2019, 141, 1 .

AMA Style

Hohyun Lee, Reza Baghaei Lakeh, Guangdong Zhu, Heejin Cho, Omid Askari. Special Issue for the 12th International Conference on Energy Sustainability (ES2018). Journal of Energy Resources Technology. 2019; 141 (6):1.

Chicago/Turabian Style

Hohyun Lee; Reza Baghaei Lakeh; Guangdong Zhu; Heejin Cho; Omid Askari. 2019. "Special Issue for the 12th International Conference on Energy Sustainability (ES2018)." Journal of Energy Resources Technology 141, no. 6: 1.

Journal article
Published: 23 January 2019 in Applied Energy
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Thermal energy storage can be utilized as an effective component in energy systems to maximize cost savings when time-of-use (TOU) pricing or real-time pricing (RTP) is in place. This study proposes a novel approach that can effectively predict performance and determine control strategy of thermal energy storage (i.e., ice storage) in a district cooling system. The proposed approach utilizes Neural Network (NN) based model predictive control (MPC) strategy coupled with a genetic algorithm (GA) optimizer and examines the effectiveness of using a NN model for a district cooling system with ice storage. The NN offers a relatively fast performance estimation of a district cooling system with given external inputs. To simulate the proposed MPC controller, a physics-based model of the district cooling system is first developed and validated to act as a virtual plant for the controller to communicate system states in real times. Next, the NN modeling the plant is developed and trained during a cooling period so that the control strategy is tested under the RTP and TOU pricing. This model is optimized using the GA due to the on/off controls for the district cooling network. Finally, a thermal load prediction algorithm is integrated to test under perfect weather inputs and weather forecasts by considering 1-hour discretization in the MPC scheme. Results indicate that for the month of August, the optimal control scheme can effectively adapt to varying loads and varying prices to effectively reduce operating costs of the district cooling network by approximately 16% and 13% under the TOU pricing and the RTP, respectively.

ACS Style

Sam J. Cox; Dongsu Kim; Heejin Cho; Pedro Mago. Real time optimal control of district cooling system with thermal energy storage using neural networks. Applied Energy 2019, 238, 466 -480.

AMA Style

Sam J. Cox, Dongsu Kim, Heejin Cho, Pedro Mago. Real time optimal control of district cooling system with thermal energy storage using neural networks. Applied Energy. 2019; 238 ():466-480.

Chicago/Turabian Style

Sam J. Cox; Dongsu Kim; Heejin Cho; Pedro Mago. 2019. "Real time optimal control of district cooling system with thermal energy storage using neural networks." Applied Energy 238, no. : 466-480.

Journal article
Published: 18 January 2019 in Journal of Energy Resources Technology
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This study evaluates the potential aggregate effects of net-zero energy building (NZEB) implementations on the electrical grid in a simulation-based analysis. To estimate the impact of NZEBs on the electrical grid, a simulation-based study of an office building with a grid-tied photovoltaic (PV) power generation system is conducted. This study assumes that net-metering is available for NZEBs such that the excess on-site PV generation can be fed to the electrical grid. The impact of electrical energy storage (EES) within NZEBs on the electrical grid is also considered in this study. Different levels of NZEB adoption are examined: 20%, 50%, and 100% of the U.S. office building stock. Results indicate that significant penetration of NZEBs could potentially affect the current U.S. electricity demand profiles by reducing purchased electricity from the electrical grid and by increasing exported electricity to the electrical grid during peak hours. Annual electricity consumption of simulated office NZEBs in the U.S. climate locations is in the range of around 94–132 kWh/m2 yr. Comparison of hourly electricity demand profiles for the actual U.S. demand versus the calculated net-demand on a national scales indicates that the peak percentage difference of the U.S. net-electricity demand includes about 10.7%, 15.2%, and 9.3% for 100% of the U.S. NZEB stock on representative summer, transition, and winter days, respectively. Using EES within NZEBs, the peak percentage differences are reduced and shifted to the afternoon, including 8.6%, 13.3%, and 6.3% for 100% of the U.S. NZEB stock on each representative day.

ACS Style

Dongsu Kim; Heejin Cho; Rogelio Luck. Potential Impacts of Net-Zero Energy Buildings With Distributed Photovoltaic Power Generation on the U.S. Electrical Grid. Journal of Energy Resources Technology 2019, 141, 062005 .

AMA Style

Dongsu Kim, Heejin Cho, Rogelio Luck. Potential Impacts of Net-Zero Energy Buildings With Distributed Photovoltaic Power Generation on the U.S. Electrical Grid. Journal of Energy Resources Technology. 2019; 141 (6):062005.

Chicago/Turabian Style

Dongsu Kim; Heejin Cho; Rogelio Luck. 2019. "Potential Impacts of Net-Zero Energy Buildings With Distributed Photovoltaic Power Generation on the U.S. Electrical Grid." Journal of Energy Resources Technology 141, no. 6: 062005.

Journal article
Published: 18 January 2019 in Journal of Energy Resources Technology
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This paper presents a methodology to predict and optimize performance of an organic Rankine cycle (ORC) using a back propagation neural network (BPNN) for diesel engine waste heat recovery. A test bench of an ORC with a diesel engine is established to collect experimental data. The collected data are used to train and test a BPNN model for performance prediction and optimization. After evaluating different hidden layers, a BPNN model of the ORC system is determined with the consideration of mean squared error (MSE) and correlation coefficient. The effects of key operating parameters on the power output of the ORC system and exhaust temperature at the outlet of the evaporator are evaluated using the proposed model and further discussed. Finally, a multi-objective optimization of the ORC system is conducted for maximizing power output and minimizing exhaust temperature at the outlet of the evaporator based on the proposed BPNN model. The results show that the proposed BPNN model has a high prediction accuracy and the maximum relative error of the power output is less than 5%. It also shows that when the operations are optimized based on the proposed model, the power output of the ORC system can be higher than the experimental results.

ACS Style

Fubin Yang; Heejin Cho; Hongguang Zhang. Performance Prediction and Optimization of an Organic Rankine Cycle Using Back Propagation Neural Network for Diesel Engine Waste Heat Recovery. Journal of Energy Resources Technology 2019, 141, 1 .

AMA Style

Fubin Yang, Heejin Cho, Hongguang Zhang. Performance Prediction and Optimization of an Organic Rankine Cycle Using Back Propagation Neural Network for Diesel Engine Waste Heat Recovery. Journal of Energy Resources Technology. 2019; 141 (6):1.

Chicago/Turabian Style

Fubin Yang; Heejin Cho; Hongguang Zhang. 2019. "Performance Prediction and Optimization of an Organic Rankine Cycle Using Back Propagation Neural Network for Diesel Engine Waste Heat Recovery." Journal of Energy Resources Technology 141, no. 6: 1.

Book chapter
Published: 01 January 2019 in Handbook of Energy Efficiency in Buildings
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ACS Style

Daniel Aelenei; Laura Aelenei; Rafaela A. Agathokleous; Francesco Asdrubali; Constantinos A. Balaras; Giorgio Baldinelli; Ilaria Ballarini; Umberto Berardi; Paolo Bertoldi; Francesco Bianchi; Fabio Bisegna; Chiara Burattini; Luisa F. Cabeza; Beatrice Castellani; Carlo Cecere; Maurizio Cellura; Heejin Cho; Helena Coch; Paolo Conti; Vincenzo Corrado; Edoardo Currà; Francesco D’Alessandro; Elena G. Dascalaki; Livio De Santoli; Umberto Desideri; Chuanshuai Dong; Luca Evangelisti; Enrico Fabrizio; Prudence Ferreira; Faidra Filippidou; Chiara Foglietta; David Gattie; Paola Gori; Walter Grassi; Claudia Guattari; Franco Gugliermetti; Patxi Hernandez; Pei Huang; Gongsheng Huang; Soteris A. Kalogirou; Katrin Klingenberg; Thomas M. Lawrence; Eleanor S. Lee; Peike Li; Sonia Longo; Roel Loonen; Lin Lu; Pedro J. Mago; Dario Masucci; Benedetta Mattoni; Michele Morganti; Elena Morini; Mojtaba Navvab; Xabat Oregi; Cosimo Palazzo; Stefano Panzieri; Marco Perino; Anna L. Pisello; Andrea Presciutti; Bale V. Reddy; Marc A. Rosen; Federico Rossi; Federica Rosso; Antonella Rotili; Agnese Salvati; Mattheos Santamouris; Samuele Schiavoni; Eva Schito; Valentina Serra; Ashlynn S. Stillwell; Daniele Testi; RuZhu Wang; Graham S. Wright; Hongxing Yang; Xiaoqiang Zhai; Tiantian Zhang. Contributors. Handbook of Energy Efficiency in Buildings 2019, 1 .

AMA Style

Daniel Aelenei, Laura Aelenei, Rafaela A. Agathokleous, Francesco Asdrubali, Constantinos A. Balaras, Giorgio Baldinelli, Ilaria Ballarini, Umberto Berardi, Paolo Bertoldi, Francesco Bianchi, Fabio Bisegna, Chiara Burattini, Luisa F. Cabeza, Beatrice Castellani, Carlo Cecere, Maurizio Cellura, Heejin Cho, Helena Coch, Paolo Conti, Vincenzo Corrado, Edoardo Currà, Francesco D’Alessandro, Elena G. Dascalaki, Livio De Santoli, Umberto Desideri, Chuanshuai Dong, Luca Evangelisti, Enrico Fabrizio, Prudence Ferreira, Faidra Filippidou, Chiara Foglietta, David Gattie, Paola Gori, Walter Grassi, Claudia Guattari, Franco Gugliermetti, Patxi Hernandez, Pei Huang, Gongsheng Huang, Soteris A. Kalogirou, Katrin Klingenberg, Thomas M. Lawrence, Eleanor S. Lee, Peike Li, Sonia Longo, Roel Loonen, Lin Lu, Pedro J. Mago, Dario Masucci, Benedetta Mattoni, Michele Morganti, Elena Morini, Mojtaba Navvab, Xabat Oregi, Cosimo Palazzo, Stefano Panzieri, Marco Perino, Anna L. Pisello, Andrea Presciutti, Bale V. Reddy, Marc A. Rosen, Federico Rossi, Federica Rosso, Antonella Rotili, Agnese Salvati, Mattheos Santamouris, Samuele Schiavoni, Eva Schito, Valentina Serra, Ashlynn S. Stillwell, Daniele Testi, RuZhu Wang, Graham S. Wright, Hongxing Yang, Xiaoqiang Zhai, Tiantian Zhang. Contributors. Handbook of Energy Efficiency in Buildings. 2019; ():1.

Chicago/Turabian Style

Daniel Aelenei; Laura Aelenei; Rafaela A. Agathokleous; Francesco Asdrubali; Constantinos A. Balaras; Giorgio Baldinelli; Ilaria Ballarini; Umberto Berardi; Paolo Bertoldi; Francesco Bianchi; Fabio Bisegna; Chiara Burattini; Luisa F. Cabeza; Beatrice Castellani; Carlo Cecere; Maurizio Cellura; Heejin Cho; Helena Coch; Paolo Conti; Vincenzo Corrado; Edoardo Currà; Francesco D’Alessandro; Elena G. Dascalaki; Livio De Santoli; Umberto Desideri; Chuanshuai Dong; Luca Evangelisti; Enrico Fabrizio; Prudence Ferreira; Faidra Filippidou; Chiara Foglietta; David Gattie; Paola Gori; Walter Grassi; Claudia Guattari; Franco Gugliermetti; Patxi Hernandez; Pei Huang; Gongsheng Huang; Soteris A. Kalogirou; Katrin Klingenberg; Thomas M. Lawrence; Eleanor S. Lee; Peike Li; Sonia Longo; Roel Loonen; Lin Lu; Pedro J. Mago; Dario Masucci; Benedetta Mattoni; Michele Morganti; Elena Morini; Mojtaba Navvab; Xabat Oregi; Cosimo Palazzo; Stefano Panzieri; Marco Perino; Anna L. Pisello; Andrea Presciutti; Bale V. Reddy; Marc A. Rosen; Federico Rossi; Federica Rosso; Antonella Rotili; Agnese Salvati; Mattheos Santamouris; Samuele Schiavoni; Eva Schito; Valentina Serra; Ashlynn S. Stillwell; Daniele Testi; RuZhu Wang; Graham S. Wright; Hongxing Yang; Xiaoqiang Zhai; Tiantian Zhang. 2019. "Contributors." Handbook of Energy Efficiency in Buildings , no. : 1.

Journal article
Published: 19 November 2018 in Heliyon
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A tubular oscillating heat pipe (OHP), with long form factor and 1 × 0.5 m2 footprint, was experimentally characterized for passive waste heat recovery via air-to-air heat exchange in a typical Heating Ventilation & Air Conditioning (HVAC) ducting system. Experiments were designed to demonstrate the OHP's ability to utilize otherwise wasted thermal energy to pre-heat or pre-cool air for reducing building energy consumption. Results indicate that the OHP is fully-capable of operating while possessing a relatively long form factor (>1 m) and as a forced convection, air-to-air heat exchanger for waste heat recovery in HVAC systems.

ACS Style

Govinda Mahajan; Scott M. Thompson; Heejin Cho. Experimental characterization of an n-pentane oscillating heat pipe for waste heat recovery in ventilation systems. Heliyon 2018, 4, e00922 .

AMA Style

Govinda Mahajan, Scott M. Thompson, Heejin Cho. Experimental characterization of an n-pentane oscillating heat pipe for waste heat recovery in ventilation systems. Heliyon. 2018; 4 (11):e00922.

Chicago/Turabian Style

Govinda Mahajan; Scott M. Thompson; Heejin Cho. 2018. "Experimental characterization of an n-pentane oscillating heat pipe for waste heat recovery in ventilation systems." Heliyon 4, no. 11: e00922.

Proceedings article
Published: 09 November 2018 in Volume 6A: Energy
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This study evaluates potential aggregate effects of net-zero energy home (NZEH) implementations on the U.S. electrical grid in a simulation-based analysis. The aggregate impact of large-scale NZEH implementations on the U.S. electrical grid is evaluated through a simulation-based study of prototype residential building models with distributed photovoltaic (PV) generation systems. An EnergyPlus residential prototype building model (i.e., a multi-family low-rise apartment building) is used to determine the detailed electricity consumption of each residential building model using U.S. climate weather files. This study assumes that net-metering is available on the electrical grid so that the surplus on-site electricity generation can be fed to the electrical grid. This study also considers the impact of electrical energy storage (EES) within NZEHs to effectively use on-site generated electricity on the electrical grid. Finally, surveyed residential building permits in 2017 are used to estimate net-electricity demand profiles of NZEHs on a national scale. Results indicate that adding distributed PV systems to enable annual multi-family NZEH performance can significantly increase changes in imported and exported electricity demand from and to the electrical grid during the daytime. However, using the EES within NZEHs helps reduce the peak electricity demand during the daytime. The stored electricity in the EES can also be used during the evening time. The peak net-electricity differences on the U.S. electrical grid-level could potentially be reduced during the daytime and shifted to the evening. Comparison of hourly electricity demand profiles for the actual U.S. demand versus the calculated net-demand on a national scale indicates that the percentage differences of U.S. net-electricity demand include about 4.5% and 4.8% for the multi-family NZEH without the EES on representative winter and summer days, respectively, at a maximum point. In addition, when the EES is added within the multi-family NZEH, the peak percentage differences could be reduced to about 3.4% and 4.3% on representative winter and summer days, respectively, at a maximum point.

ACS Style

Dongsu Kim; Heejin Cho; Rogelio Luck; Pedro Mago. Potential Aggregate Effects of Net-Zero Energy Homes (NZEHs) With Distributed Energy Generation on the U.S. Electrical Grid. Volume 6A: Energy 2018, 1 .

AMA Style

Dongsu Kim, Heejin Cho, Rogelio Luck, Pedro Mago. Potential Aggregate Effects of Net-Zero Energy Homes (NZEHs) With Distributed Energy Generation on the U.S. Electrical Grid. Volume 6A: Energy. 2018; ():1.

Chicago/Turabian Style

Dongsu Kim; Heejin Cho; Rogelio Luck; Pedro Mago. 2018. "Potential Aggregate Effects of Net-Zero Energy Homes (NZEHs) With Distributed Energy Generation on the U.S. Electrical Grid." Volume 6A: Energy , no. : 1.

Journal article
Published: 17 August 2018 in Journal of Building Engineering
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Advanced passive control technologies attract a great deal of attention by architects and engineers as a way of achieving both high indoor environmental quality and energy efficient buildings. This study investigates the thermal and daylighting effects of a double skin façade (DSF) system with interior and exterior blinds. A buffer type DSF and slat type blinds are used for this comparative study. To investigate thermal and daylighting effects of three passive control models, evaluation of annual heating, cooling, and lighting loads is conducted using a widely-accepted whole building energy modeling program, EnergyPlus. A simulated DSF model is developed using the air-flow network (AFN) model in EnergyPlus and calibrated against measured data from an experimental DSF facility installed to an office building in Daejeon, South Korea. After a proper calibration of the simulated DSF model, the impact of blinds in the cavity of the DSF is also evaluated by adopting a slat blind model in EnergyPlus. For exterior and interior blind models, the simulated DSF model is modified by removing a DSF box and adding slat blinds at inner and outer surfaces of the windows. A Radiance-based daylighting simulation program, Daysim, is used to evaluate daylighting aspects of blinds and lighting controls within an office building with simulated DSF, interior blind, and exterior blind models. Generated lighting and blind raise/lower control schedules from Daysim are used as input values in EnergyPlus for annual thermal and lighting load calculations. In addition, the impact of natural ventilation to reduce trapped hot air within the cavity of the DSF box is considered in this study during a cooling period only for the DSF model. Results indicate that the simulated DSF model can save up to 40%, 2%, and 5% for heating, cooling, and total loads, respectively, when compared to the baseline (i.e., No passive technologies) without any blinds or controls. With the combination of the daylight-based dimming control based on the indoor illuminance levels and the blind raise/lower control, the simulated DSF and the exterior blind models could potentially reduce the building thermal loads and lighting energy consumption, ranging around 27% to 52%.

ACS Style

Dongsu Kim; Sam J. Cox; Heejin Cho; Jongho Yoon. Comparative investigation on building energy performance of double skin façade (DSF) with interior or exterior slat blinds. Journal of Building Engineering 2018, 20, 411 -423.

AMA Style

Dongsu Kim, Sam J. Cox, Heejin Cho, Jongho Yoon. Comparative investigation on building energy performance of double skin façade (DSF) with interior or exterior slat blinds. Journal of Building Engineering. 2018; 20 ():411-423.

Chicago/Turabian Style

Dongsu Kim; Sam J. Cox; Heejin Cho; Jongho Yoon. 2018. "Comparative investigation on building energy performance of double skin façade (DSF) with interior or exterior slat blinds." Journal of Building Engineering 20, no. : 411-423.

Journal article
Published: 27 June 2018 in Buildings
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This study simulates an increased thermal capacitance (ITC) and thermal storage management (TSM) system to reduce the energy consumed by air conditioning and heating systems. The ITC/TSM is coupled with phase change materials (PCM), which enable tank volume reduction. The transient energy modeling software, the Transient System Simulation Tool (TRNSYS), is used to simulate the buildings’ thermal response and energy consumption, as well as the ITC/TSM system and controls. Four temperature-controlled operating regimes are used for the tank: building shell circulation, heat exchanger circulation, solar panel circulation, and storage. This study also explores possible energy-saving benefits from tank volume reduction such as losses associated with the environment temperature due to tank location. Three different tank locations are considered in this paper: outdoor, buried, and indoor. The smallest tank size (five gallons) is used for indoor placement, while the large tank (50 gallons) is used either for outdoor placement or buried at a depth of 1 m. Results for Atlanta, Georgia show an average 48% required energy decrease for cold months (October–April) and a 3% decrease for warm months (May–September) for the ITC/TSM system with PCM when compared with the reference case. A system with PCM reduces the tank size by 90% while maintaining similar energy savings.

ACS Style

Mary Wilson; Rogelio Luck; Pedro J. Mago; Heejin Cho. Building Energy Management Using Increased Thermal Capacitance and Thermal Storage Management. Buildings 2018, 8, 86 .

AMA Style

Mary Wilson, Rogelio Luck, Pedro J. Mago, Heejin Cho. Building Energy Management Using Increased Thermal Capacitance and Thermal Storage Management. Buildings. 2018; 8 (7):86.

Chicago/Turabian Style

Mary Wilson; Rogelio Luck; Pedro J. Mago; Heejin Cho. 2018. "Building Energy Management Using Increased Thermal Capacitance and Thermal Storage Management." Buildings 8, no. 7: 86.