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Selected Papers from the 11th Asia-Pacific Forum on Renewable Energy (AFORE 2022)

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "A: Sustainable Energy".

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 31423

Special Issue Editors

Prof. Dr. Hwachang Song

E-Mail Website
Guest Editor
Department of Electrical Engineering, Seoul National University of Science and Technology, Seoul 139-743, Korea
Interests: energy storage application; renewable energy integration; renewable energy forecasting; smart grids
Special Issues, Collections and Topics in MDPI journals
Dr. Hyun-Goo Kim

E-Mail Website
Guest Editor
New and Renewable Energy Map Laboratory, Korea Institute of Energy Research, Daejeon 34129, Korea
Interests: renewable energy resource assessment; remote sensing; solar and wind forecasting
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The international climate action initiatives on the sustainable environment goals basically aim to increase the share of renewable energy (RE) in the world energy use. However, since RE resources have intermittent and variable nature in nature and require more efficient energy extraction for the goal achievement, there are many obstacles to be solved from technical and economical point of views. In this Special Issue, those experts from academia and industry attending AFORE 2022 are to discuss practical measures and advanced technologies on technical and economic perspectives to renewable energy and the pathway to carbon neutrality. This Special Issue covers all the topics related to RE technologies, including solar energy, wind energy, hydrogen and fuel cells, bioenergy, geothermal energy, hydro power, marine energy, energy storage and grid integration, resource assessment, policy and strategy, and low carbon technology.

Prof. Dr. Hwachang Song
Dr. Hyun-Goo Kim
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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Keywords

  • solar energy
  • wind energy
  • hydrogen and fuel cells
  • bioenergy
  • geothermal energy
  • hydro power
  • marine energy
  • energy storage and grid integration
  • resource assessment
  • policy and strategy
  • low carbon technology

Published Papers (19 papers)

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Research

11 pages, 2364 KiB  
Article
Consideration on Proper Management and Final Disposal of Residues from SRF Manufacturing Facilities in South Korea
by Suyoung Lee, Kyuyeon Kim, Dongyoon Kim, Jungu Kang and Taewan Jeon
Energies 2023, 16(2), 701; https://doi.org/10.3390/en16020701 - 06 Jan 2023
Viewed by 1094
Abstract
Solid Refuse Fuel (SRF) manufacturing facilities process 4.72 million tons of waste annually. The residues generated after manufacturing SRF products account for 35–40% of the input waste, and most of them are finally disposed of in landfills. The process flow and management status [...] Read more.
Solid Refuse Fuel (SRF) manufacturing facilities process 4.72 million tons of waste annually. The residues generated after manufacturing SRF products account for 35–40% of the input waste, and most of them are finally disposed of in landfills. The process flow and management status of SRF manufacturing facilities were investigated, and the residues generated from SRF manufacturing facilities using municipaland industrial waste, respectively, were separated by particle size. The appropriate separation conditions for the residues according to the characteristics of the input raw materials were presented through the analysis of loss on ignition (LOI), organic foreign substance content, heating value, and carbon content. Based on this, the appropriate management criteria (draft) for the subsequent treatment of final residues were derived to improve recyclability. Residues generated in the SRF manufacturing process need to be additionally separated into combustibles and incombustibles through cylindrical rotary separating devices before subsequent the final disposal process. Full article
(This article belongs to the Special Issue Selected Papers from the 11th Asia-Pacific Forum on Renewable Energy (AFORE 2022))
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26 pages, 2362 KiB  
Article
Comparative Economic Analysis of Solar PV and Reused EV Batteries in the Residential Sector of Three Emerging Countries—The Philippines, Indonesia, and Vietnam
by Hong Eun Moon, Yoon Hee Ha and Kyung Nam Kim
Energies 2023, 16(1), 311; https://doi.org/10.3390/en16010311 - 27 Dec 2022
Cited by 9 | Viewed by 3031
Abstract
An emerging problem associated with the increased global demand for electric vehicles (EVs) is the post-use of lithium-ion batteries installed in them. Discarded batteries maintain 70–80% of their performance; thus, they are highly valuable recycling resources. Accordingly, technologies that complement the intermittency of [...] Read more.
An emerging problem associated with the increased global demand for electric vehicles (EVs) is the post-use of lithium-ion batteries installed in them. Discarded batteries maintain 70–80% of their performance; thus, they are highly valuable recycling resources. Accordingly, technologies that complement the intermittency of renewable energy by integrating discarded EV batteries into battery energy storage systems (BESSs) are receiving attention. Here, the economic feasibility of a residential solar photovoltaic (PV) + reused BESS (RBESS) integrated system in three emerging countries (Philippines, Indonesia, and Vietnam) was analyzed by comparing its performance with that of diesel power generation and central grid-supplied power. The proposed system had a higher economic feasibility than diesel power generation (55.9% lower LCOE) but a lower economic feasibility than the central grid-supplied power (282.7% higher LCOE) in all three countries. Additionally, we conducted a sensitivity analysis by incorporating the investment cost, government subsidy, and social cost of greenhouse gas emissions. In conclusion, the Philippines is the best country for grid parity with the integrated system, following Indonesia and Vietnam. This study examined both the economic and social benefits of the proposed system as a countermeasure to climate change and the virtuous resource cycle. Full article
(This article belongs to the Special Issue Selected Papers from the 11th Asia-Pacific Forum on Renewable Energy (AFORE 2022))
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16 pages, 7594 KiB  
Article
Numerical Investigation of the Initial Charging Process of the Liquid Hydrogen Tank for Vehicles
by Daehoon Kang, Sungho Yun, Bo-kyong Kim, Jaewon Kim, Gildong Kim, Hyunbae Lee and Sangyeol Choi
Energies 2023, 16(1), 38; https://doi.org/10.3390/en16010038 - 21 Dec 2022
Cited by 1 | Viewed by 2024
Abstract
Liquid hydrogen has been studied for use in vehicles. However, during the charging process, liquid hydrogen is lost as gas. Therefore, it is necessary to estimate and reduce this loss and simulate the charging process. In this study, the initial charging process of [...] Read more.
Liquid hydrogen has been studied for use in vehicles. However, during the charging process, liquid hydrogen is lost as gas. Therefore, it is necessary to estimate and reduce this loss and simulate the charging process. In this study, the initial charging process of a vehicle liquid hydrogen tank under room temperature and atmospheric pressure conditions was numerically investigated. A transient thermal-fluid simulation with a phase-change model was performed to analyze variations in the volume, pressure, mass flow rate, and temperature. The results showed that the process could be divided into three stages. In the first stage, liquid hydrogen was actively vaporized at the inner wall surface of the storage tank. The pressure increased rapidly, and liquid droplets were discharged into the vent pipe during the second stage. In the third stage, the mass flow rates of liquid and hydrogen gas at the outlet showed significant fluctuations, owing to complex momentum generated by the evaporation and charging flow. The temperatures of the inner and outer walls, and insulation layer, decreased significantly slower than that of the gas region because of its high heat capacity and insulation effect. The optimal structure should be further studied because the vortex, stagnation, and non-uniform cooling of the wall occurred near the inlet and outlet pipes. Full article
(This article belongs to the Special Issue Selected Papers from the 11th Asia-Pacific Forum on Renewable Energy (AFORE 2022))
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17 pages, 4840 KiB  
Article
Information Analysis on Foreign Institution for International R&D Collaboration Using Natural Language Processing
by Jihoo Jung, Jehyun Lee, Sangjin Choi and Woonho Baek
Energies 2023, 16(1), 33; https://doi.org/10.3390/en16010033 - 21 Dec 2022
Viewed by 1178
Abstract
The number of international collaborations in research and development (R&D) has been increasing in the energy sector to solve global environmental problems—such as climate change and the energy crisis—and to reduce the time, cost, and risk of failure. Successful international project planning requires [...] Read more.
The number of international collaborations in research and development (R&D) has been increasing in the energy sector to solve global environmental problems—such as climate change and the energy crisis—and to reduce the time, cost, and risk of failure. Successful international project planning requires the analysis of research fields and the technology expertise of cooperative partner institutions or countries, but this takes time and resources. In this study, we developed a method to analyze the information on research organizations and topics, taking advantage of data analysis as well as deep learning natural language processing (NLP) models. A method to evaluate the relative superiority of efficient international collaboration was suggested, assuming international collaboration of the National Renewable Energy Laboratory (NREL) and the Korea Institute of Energy Research (KIER). Additionally, a workflow of an automated executive summary and a translation of tens of web-posted articles is also suggested for a quick glance. The valuation of the suggested methodology is estimated as much as the annual salary of an experienced employee. Full article
(This article belongs to the Special Issue Selected Papers from the 11th Asia-Pacific Forum on Renewable Energy (AFORE 2022))
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17 pages, 5958 KiB  
Article
Power Performance Analysis Based on Savonius Wind Turbine Blade Design and Layout Optimization through Rotor Wake Flow Analysis
by Heejeon Im and Bumsuk Kim
Energies 2022, 15(24), 9500; https://doi.org/10.3390/en15249500 - 14 Dec 2022
Cited by 5 | Viewed by 2395
Abstract
Savonius vertical axis wind turbines have simple structures, can self-start in environments with low wind speed and strong turbulence intensity, and can be installed at low costs. Therefore, installation is possible in urban centers with low wind speeds, which may contribute to the [...] Read more.
Savonius vertical axis wind turbines have simple structures, can self-start in environments with low wind speed and strong turbulence intensity, and can be installed at low costs. Therefore, installation is possible in urban centers with low wind speeds, which may contribute to the construction of a decentralized power system. Savonius wind turbines are operated by drag force, with the blades moving in the same direction as the flow current providing the thrust force and those moving in the opposite direction of the wind being rotated by the drag force. In this study, the Savonius wind turbine design was examined to develop a stable wind turbine for use in urban centers at low wind speeds. The Savonius rotor design variables (aspect and overlap ratios) and blade forms (semi-circular, Bach, and elliptical type) were examined using computational fluid dynamics analysis. Moreover, a rotor capable of providing the target output was designed and maximum rotor efficiency of 18% was realized. Further, changes to the flow corresponding with various turbine layouts were analyzed to determine the arrangement that would maximize turbine performance. The results showed that the maximum efficiency of the turbines was in the 17–19% range and without significant variation. Full article
(This article belongs to the Special Issue Selected Papers from the 11th Asia-Pacific Forum on Renewable Energy (AFORE 2022))
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15 pages, 3879 KiB  
Article
Verification of Prediction Method Based on Machine Learning under Wake Effect Using Real-Time Digital Simulator
by Rae-Jin Park, Jeong-Hwan Kim, Byungchan Yoo, Minhan Yoon and Seungmin Jung
Energies 2022, 15(24), 9475; https://doi.org/10.3390/en15249475 - 14 Dec 2022
Viewed by 1139
Abstract
With the increase in the penetration rate of renewable energy sources, a machine-learning-based forecasting system has been introduced to the grid sector to improve the participation rate in the electricity market and reduce energy losses. In these studies, correlation analysis of mechanical and [...] Read more.
With the increase in the penetration rate of renewable energy sources, a machine-learning-based forecasting system has been introduced to the grid sector to improve the participation rate in the electricity market and reduce energy losses. In these studies, correlation analysis of mechanical and environmental variables, including geographical figures, is considered a crucial point to increase the prediction’s accuracy. Various models have been applied in terms of accuracy, speed calculation, and amount of data based on a mathematical model that can calculate the wake; however, it can be difficult to derive variables such as air density, roughness length, and the effect of turbulence on the structural characteristics of wind turbines. Furthermore, wake accuracy could decrease due to the excessive variables that come from the wake effect parameters. In this paper, we intend to conduct research to improve prediction accuracy by considering the wake effect of wind turbines using supervisory control and data acquisition (SCADA) data from the Dongbok wind farm. The wake divides the wind direction into four parts and then recognizes and predicts the affected wind turbine. The predicted result is the wake wind speed and its conversion to power generation by applying a power curve. We try to show the efficiency of machine learning by comparing the wake wind speed and the power generation in the wake model. This result shows the error rate using evaluation metrics of regression, such as mean squared error (MSE), root mean squared error (RMSE), and weighted absolute percentage error (WAPE), and attempts to verify power system impact and efficiency through a real-time digital simulator (RTDS). Full article
(This article belongs to the Special Issue Selected Papers from the 11th Asia-Pacific Forum on Renewable Energy (AFORE 2022))
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15 pages, 2033 KiB  
Article
Applicability of Dynamic Inflow Models of HAWT in Yawed Flow Conditions
by Chihoon Hur, Carlos Ferreira and Gerard Schepers
Energies 2022, 15(24), 9368; https://doi.org/10.3390/en15249368 - 10 Dec 2022
Viewed by 922
Abstract
Horizontal axis wind turbines (HAWTs) experience yaw misalignments due to the physical limitations of yaw controllers and various novel active yaw controls. Moreover, the motion of floating offshore wind turbines (FOWTs) accelerates yaw misalignment. The blade element momentum (BEM) method is widely used [...] Read more.
Horizontal axis wind turbines (HAWTs) experience yaw misalignments due to the physical limitations of yaw controllers and various novel active yaw controls. Moreover, the motion of floating offshore wind turbines (FOWTs) accelerates yaw misalignment. The blade element momentum (BEM) method is widely used due to its computational efficiency for the design of HAWTs. Momentum theory, the basis of BEM, assumes steady flow and uniform induction field at the disc. Those assumptions are relaxed by engineering models to capture yaw and unsteady effects. Current yaw engineering models, however, are inaccurate since they do not capture the asymmetric wake expansion effect. Dynamic inflow models have been developed for non-yawed flow. Furthermore, the AVATAR project shows that BEM using fully coupled engineering models, the current yaw, dynamic inflow and various engineering models, suffers from significant deficiencies. This purpose of this paper, therefore, is to investigate dynamic effects for yawed flow, and determine if current dynamic inflow models are applicable in yawed conditions. The Glauert’s modified momentum theory is applied to dynamic inflow models to couple the two models. Among all coupled models, Øye, Yu PWVM and Yu FWVM DIM can capture asymmetric trends. However, the results show the significant deficiencies in phase delay on the actuator disc. Full article
(This article belongs to the Special Issue Selected Papers from the 11th Asia-Pacific Forum on Renewable Energy (AFORE 2022))
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44 pages, 2271 KiB  
Article
Economic Analysis of P2G Green Hydrogen Generated by Existing Wind Turbines on Jeju Island
by Youngmin Cho, Sanglae Lee, Jinseok Lim and Jaewoo Lee
Energies 2022, 15(24), 9317; https://doi.org/10.3390/en15249317 - 08 Dec 2022
Cited by 1 | Viewed by 1977
Abstract
Every wind turbine is subject to fluctuations in power generation, depending on climatic conditions. When electricity supply exceeds demand, wind turbines are forced to implement curtailment, causing a reduction in generation efficiency and commercial loss to turbine owners. Since the frequency and amount [...] Read more.
Every wind turbine is subject to fluctuations in power generation, depending on climatic conditions. When electricity supply exceeds demand, wind turbines are forced to implement curtailment, causing a reduction in generation efficiency and commercial loss to turbine owners. Since the frequency and amount of curtailment of wind turbines increases as the amount of renewable energy become higher on Jeju Island in South Korea, Jeju is configuring a Power to Gas (P2G) water-electrolysis system that will be connected to an existing wind farm to use the “wasted energy”. In this study, economic analysis was performed by calculating the production cost of green hydrogen, and sensitivity analysis evaluated the variance in hydrogen cost, depending on several influential factors. Approaches to lower hydrogen costs are necessary for the following reasons. The operating company needs a periodical update of hydrogen sale prices by reflecting a change in the system margin price (SMP) with the highest sensitivity to hydrogen cost. Technical development to reduce hydrogen costs in order to reduce power consumption for producing hydrogen and a decrease in annual reduction rate for the efficiency of water electrolysis is recommended. Discussions and research regarding government policy can be followed to lower the hydrogen cost. Full article
(This article belongs to the Special Issue Selected Papers from the 11th Asia-Pacific Forum on Renewable Energy (AFORE 2022))
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16 pages, 1466 KiB  
Article
Urban Hydrogen Production Model Using Environmental Infrastructures to Achieve the Net Zero Goal
by Hyodong Moon, Hyoeun Lee, Boram Kim and Yunsung Kim
Energies 2022, 15(24), 9293; https://doi.org/10.3390/en15249293 - 07 Dec 2022
Viewed by 1073
Abstract
Land available for energy production is limited in cities owing to high population density. To reach the net zero goal, cities contributing 70% of overall greenhouse gas emissions need to dramatically reduce emissions and increase self-sufficiency in energy production. Environmental infrastructures such as [...] Read more.
Land available for energy production is limited in cities owing to high population density. To reach the net zero goal, cities contributing 70% of overall greenhouse gas emissions need to dramatically reduce emissions and increase self-sufficiency in energy production. Environmental infrastructures such as sewage treatment and incineration plants can be used as energy production facilities in cities. This study attempted to examine the effect of using environmental infrastructure such as energy production facilities to contribute toward the carbon neutrality goal through urban energy systems. In particular, since the facilities are suitable for hydrogen supply in cities, the analysis was conducted focusing on the possibility of hydrogen production. First, the current status of energy supply and demand, and additional energy production potential in sewage treatment and incineration plants in Seoul, were analyzed. Then, the role of these environmental infrastructures toward energy self-sufficiency in the urban system was examined. This study confirmed that the facilities can contribute to the city’s energy self-sufficiency and the achievement of its net-zero goal. Full article
(This article belongs to the Special Issue Selected Papers from the 11th Asia-Pacific Forum on Renewable Energy (AFORE 2022))
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19 pages, 3893 KiB  
Article
Study on the Performance of a Newly Designed Cooling System Utilizing Dam Water for Internet Data Centers
by Selorm Kwaku Anka, Nicholas Lamptey Boafo, Kwesi Mensah, Samuel Boahen, Kwang Ho Lee and Jong Min Choi
Energies 2022, 15(24), 9274; https://doi.org/10.3390/en15249274 - 07 Dec 2022
Viewed by 1752
Abstract
A novel energy-saving hybrid cooling system that combines a forced-cooling cycle and a free-cooling cycle was developed to increase the energy efficiency of cooling systems in year-round operation of an internet data center with high heat loads. This system effectively utilizes a dam [...] Read more.
A novel energy-saving hybrid cooling system that combines a forced-cooling cycle and a free-cooling cycle was developed to increase the energy efficiency of cooling systems in year-round operation of an internet data center with high heat loads. This system effectively utilizes a dam deep water source to reduce energy consumption in internet data centers. The hybrid cooling system operates in forced-cooling mode when the entering water temperature exceeds the mode change temperature of 9 °C, but switches to free-cooling mode when the ambient temperature falls below the mode change temperature. In this paper, the cooling performance of the hybrid system was assessed under various operating conditions based on entering water temperature fluctuation. Because the cooling effectiveness of this type of system is highly dependent on the outside climate, its usefulness and suitability for different periods and zones must be investigated. The annual energy saving performance of the new system was estimated and compared to a conventional cooling system in terms of the integrated coefficient of performance, based on the hourly weather air temperature and water temperature bin data collected from 16 cities of different climate zones in South Korea. The experimental findings revealed that the novel hybrid internet data center cooling system showed a 67% annual operating performance over a conventional air source internet data center cooling system due to the adoption of a dam deep water source. Full article
(This article belongs to the Special Issue Selected Papers from the 11th Asia-Pacific Forum on Renewable Energy (AFORE 2022))
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17 pages, 4110 KiB  
Article
Energy Balance Data-Based Optimization of Louver Installation Angles for Different Regions in Korea
by Seung-Ju Choe and Seung-Hoon Han
Energies 2022, 15(23), 9214; https://doi.org/10.3390/en15239214 - 05 Dec 2022
Cited by 1 | Viewed by 1131
Abstract
A louver is a traditional environmental control device and passive architectural element based on an ecofriendly concept. Louvers are architectural elements that can be used to regulate natural lighting, thermal environment, and building energy use. To realize these integrated functionalities of louvers, they [...] Read more.
A louver is a traditional environmental control device and passive architectural element based on an ecofriendly concept. Louvers are architectural elements that can be used to regulate natural lighting, thermal environment, and building energy use. To realize these integrated functionalities of louvers, they must be designed considering the climate and geographical characteristics of the target region. However, these aspects are typically not considered during building design in Korea, resulting in lovers being used as design elements with simple natural lighting control functions. Therefore, the objective of this study was to promote the integrated use of louvers by optimizing the louver angle according to the microclimate in Korea from the viewpoint of thermal energy use. We performed load and energy simulation planning and calculation and conducted optimization studies for the louver angle and range of motion for each region. The energy consumption in central and southern Korean regions was minimized when the angles of the fixed louvers were 45°–75° and 60°–90°, respectively. Kinetic louvers could enhance thermal energy management when installed at 30°–75° in spring, 135°–165° in summer, 75°–165° in autumn, and 45°–75° in winter. These findings can promote the realization of integrated functionalities of louvers from the perspective of indoor environment comfort based on the microclimates of the Korean regions. Full article
(This article belongs to the Special Issue Selected Papers from the 11th Asia-Pacific Forum on Renewable Energy (AFORE 2022))
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13 pages, 3887 KiB  
Article
Spatiotemporal Analysis of Hydrogen Requirement to Minimize Seasonal Variability in Future Solar and Wind Energy in South Korea
by Myeongchan Oh, Boyoung Kim, Changyeol Yun, Chang Ki Kim, Jin-Young Kim, Su-Jin Hwang, Yong-Heack Kang and Hyun-Goo Kim
Energies 2022, 15(23), 9097; https://doi.org/10.3390/en15239097 - 30 Nov 2022
Cited by 2 | Viewed by 1028
Abstract
Renewable energy supply is essential for carbon neutrality; however, technologies aiming to optimally utilize renewable energy sources remain insufficient. Seasonal variability in renewable energy is a key issue, which many studies have attempted to overcome through operating systems and energy storage. Currently, hydrogen [...] Read more.
Renewable energy supply is essential for carbon neutrality; however, technologies aiming to optimally utilize renewable energy sources remain insufficient. Seasonal variability in renewable energy is a key issue, which many studies have attempted to overcome through operating systems and energy storage. Currently, hydrogen is the only technology that can solve this seasonal storage problem. In this study, the amount of hydrogen required to circumvent the seasonal variability in renewable energy supply in Korea was quantified. Spatiotemporal analysis was conducted using renewable energy resource maps and power loads. It was predicted that 50% of the total power demand in the future will be met using solar and wind power, and a scenario was established based on the solar-to-wind ratio. It was found that the required hydrogen production differed by approximately four-times, depending on the scenarios, highlighting the importance of supplying renewable energy at an appropriate ratio. Spatially, wind power was observed to be unsuitable for the physical transport of hydrogen because it has a high potential at mountain peaks and islands. The results of this study are expected to aid future hydrogen research and solve renewable energy variability problems. Full article
(This article belongs to the Special Issue Selected Papers from the 11th Asia-Pacific Forum on Renewable Energy (AFORE 2022))
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11 pages, 5481 KiB  
Article
Co-Firing Combustion Characteristics of Woodchips and Spent Mushroom Substrates in a 400 kWth Stoker-Type Boiler
by Hyun-Hee Lee, Sae-Byul Kang, Jae-Joon Choi, Young-Jik Youn, Kyu-Won Kim, Man-Soo Jeong and Jae-Kyung Byeon
Energies 2022, 15(23), 9096; https://doi.org/10.3390/en15239096 - 30 Nov 2022
Viewed by 975
Abstract
The simultaneous firing characteristics of woodchips and spent mushroom substrates (SMS) were studied in a stoker-type industrial boiler. The type of spent substrate intended for combustion consisted of oyster mushrooms. SMS from mushroom farms generally have a high water content. Dryers are therefore [...] Read more.
The simultaneous firing characteristics of woodchips and spent mushroom substrates (SMS) were studied in a stoker-type industrial boiler. The type of spent substrate intended for combustion consisted of oyster mushrooms. SMS from mushroom farms generally have a high water content. Dryers are therefore used for combustion. The moisture content of SMS was reduced to achieve low moisture to combust sufficiently at about 20%. First, the basic characteristics of the boiler were confirmed by conducting a woodchip combustion test under various operating loads of 30, 50, 70, and 100%. Thereafter, a simultaneous combustion test of woodchips and SMS was performed. During the experiment, exhaust gas concentrations in the boiler combustion chamber were measured, such as the temperature of oxygen (O2), carbon monoxide (CO), and nitrogen oxides (NOx). In addition, industrial and basic analyses were performed on woodchips and SMS. The main differences in the fuel analysis results between woodchips and SMS were ash, nitrogen, sulfur content and net calorific value. According to the analysis, the nitrogen content of SMS was 2.6%, which was 8.7 times higher than that of woodchips, and the ash content was also 14.8%, which was 18.5 times that of woodchips. As a result of the combustion experiment, the woodchip experiment revealed that the values of O2 and CO decreased and the combustion chamber temperature increased as the amount of fuel increased. Due to higher combustion temperature, thermal NOx also increased. When comparing this combustion test with the co-firing test, there was no significant difference in O2, CO, and combustion chamber temperature. However, with regard to the NOx value, the results showed a sharp increase from 64 ppm to 135 ppm. Although the NOx value increased, SMS had enough heat to be burned as fuel. Therefore, the utility of various agricultural byproducts as fuel has prospects for achieving an effective approach to energy cost reduction. Full article
(This article belongs to the Special Issue Selected Papers from the 11th Asia-Pacific Forum on Renewable Energy (AFORE 2022))
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21 pages, 6077 KiB  
Article
Experimental and Finite Element-Based Investigation on Lateral Behaviors of a Novel Hybrid Monopile
by Jeongsoo Kim, Yeon-Ju Jeong, Joonsang Park, Ju-Hyung Lee, Taeyoung Kwak and Jae-Hyun Kim
Energies 2022, 15(23), 9095; https://doi.org/10.3390/en15239095 - 30 Nov 2022
Cited by 1 | Viewed by 1387
Abstract
A monopile is the most conventional structure foundation for offshore wind turbines (OWTs) in the world. However, the Korean offshore wind industry has mostly been using the jacket type of foundation. The main reason for the current situation in Korea is that most [...] Read more.
A monopile is the most conventional structure foundation for offshore wind turbines (OWTs) in the world. However, the Korean offshore wind industry has mostly been using the jacket type of foundation. The main reason for the current situation in Korea is that most of the marine soil consists of weak layers of sand and clay. Thus, the monopile foundation depth has to be deep enough to satisfy the intended serviceability design requirement of the monopile and the rotation limit at the seabed; a conventional monopile design concept alone might be insufficient in Korean offshore conditions, or otherwise could be very expensive, e.g., resulting in a rock socket installation at the tip of the monopile. The main objective of this paper is to introduce a novel hybrid monopile that is composed of a monopile and a supplemental support with three buckets, followed by assessing the lateral resistance of the hybrid system through physical experiments and finite element (FE) simulations. Namely, 1/64.5 small-scaled monopile and hybrid physical models with a monopile diameter of 7 m for a 5.5 MW OWT were loaded monotonically. The results show that the hybrid monopile improves the lateral bearing capacity regarding the initial lateral stiffness and ultimate load. The FE analyses of the corresponding physical models were also implemented to support the results from the physical model test. The numerical results, such as the structural member forces and soil deformation, were analyzed in detail. Additionally, a case study using FE analysis was conducted for the 5.5 MW OWT hybrid monopile support installed in a representative Korean weak soil area. The results show that the hybrid monopile foundation has a larger lateral resistance and stiffness than the monopile. Full article
(This article belongs to the Special Issue Selected Papers from the 11th Asia-Pacific Forum on Renewable Energy (AFORE 2022))
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20 pages, 6098 KiB  
Article
Site-Adaptation for Correcting Satellite-Derived Solar Irradiance: Performance Comparison between Various Regressive and Distribution Mapping Techniques for Application in Daejeon, South Korea
by Elvina Faustina Dhata, Chang Ki Kim, Hyun-Goo Kim, Boyoung Kim and Myeongchan Oh
Energies 2022, 15(23), 9010; https://doi.org/10.3390/en15239010 - 28 Nov 2022
Cited by 2 | Viewed by 1381
Abstract
Satellite-derived solar irradiance is advantageous in solar resource assessment due to its high spatiotemporal availability, but its discrepancies to ground-observed values remain an issue for reliability. Site adaptation can be employed to correct these errors by using short-term high-quality ground-observed values. Recent studies [...] Read more.
Satellite-derived solar irradiance is advantageous in solar resource assessment due to its high spatiotemporal availability, but its discrepancies to ground-observed values remain an issue for reliability. Site adaptation can be employed to correct these errors by using short-term high-quality ground-observed values. Recent studies have highlighted the benefits of the sequential procedure of a regressive and a distribution-mapping technique in comparison to their individual counterparts. In this paper, we attempted to improve the sequential procedure by using various distribution mapping techniques in addition to the previously proposed quantile mapping. We applied these site-adaptation techniques on the global horizontal irradiance (GHI) and direct normal irradiance (DNI) obtained from the UASIBS-KIER model in Daejeon, South Korea. The best technique, determined by a ranking methodology, can reduce the mean bias from −5.04% and 13.51% to −0.45% and −2.02% for GHI and DNI, respectively, and improve distribution similarity by 2.5 times and 4 times for GHI and DNI, respectively. Partial regression and residual plot analysis were attempted to examine our finding that the sequential procedure is better than individual techniques for GHI, whereas the opposite is true for DNI. This is an initial study to achieve generalized site-adaptation techniques for the UASIBS-KIER model output. Full article
(This article belongs to the Special Issue Selected Papers from the 11th Asia-Pacific Forum on Renewable Energy (AFORE 2022))
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20 pages, 3556 KiB  
Article
Assessment of Greenhouse Gas Emissions from Hydrogen Production Processes: Turquoise Hydrogen vs. Steam Methane Reforming
by Gayatri Udaysinh Ingale, Hyun-Min Kwon, Soohwa Jeong, Dongho Park, Whidong Kim, Byeingryeol Bang, Young-Il Lim, Sung Won Kim, Youn-Bae Kang, Jungsoo Mun, Sunwoo Jun and Uendo Lee
Energies 2022, 15(22), 8679; https://doi.org/10.3390/en15228679 - 18 Nov 2022
Cited by 11 | Viewed by 3217
Abstract
Hydrogen has received substantial attention because of its diverse application in the energy sector. Steam methane reforming (SMR) dominates the current hydrogen production and is the least expensive endothermic reaction to produce grey hydrogen. This technology provides the advantages of low cost and [...] Read more.
Hydrogen has received substantial attention because of its diverse application in the energy sector. Steam methane reforming (SMR) dominates the current hydrogen production and is the least expensive endothermic reaction to produce grey hydrogen. This technology provides the advantages of low cost and high energy efficiency; however, it emits an enormous amount of CO2. Carbon capture storage (CCS) technology helps reduce these emissions by 47% to 53%, producing blue hydrogen. Methane pyrolysis is an alternative to SMR that produces (ideally) CO2-free turquoise hydrogen. In practice, methane pyrolysis reduces CO2 emissions by 71% compared to grey hydrogen and 46% compared to blue hydrogen. While carbon dioxide emissions decrease with CCS, fugitive methane emissions (FMEs) for blue and turquoise hydrogen are higher than those for grey hydrogen because of the increased use of natural gas to power carbon capture. We undertake FMEs of 3.6% of natural gas consumption for individual processes. In this study, we also explore the utilization of biogas as a feedstock and additional Boudouard reactions for efficient utilization of solid carbon from methane pyrolysis and carbon dioxide from biogas. The present study focuses on possible ways to reduce overall emissions from turquoise hydrogen to provide solutions for a sustainable low-CO2 energy source. Full article
(This article belongs to the Special Issue Selected Papers from the 11th Asia-Pacific Forum on Renewable Energy (AFORE 2022))
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13 pages, 4205 KiB  
Article
Boosting the Transesterification Reaction by Adding a Single Na Atom into g-C3N4 Catalyst for Biodiesel Production: A First-Principles Study
by Elim Kim, Ayuk Corlbert Ayuk, Deog-Keun Kim, Hak Joo Kim and Hyung Chul Ham
Energies 2022, 15(22), 8432; https://doi.org/10.3390/en15228432 - 11 Nov 2022
Cited by 2 | Viewed by 1290
Abstract
Increasing environmental problems and the energy crisis have led to interest in the development of alternative energy. One of the most promising sustainable alternatives to fossil fuel is biodiesel which is typically produced from the transesterification of refined vegetable oils using a homogeneous [...] Read more.
Increasing environmental problems and the energy crisis have led to interest in the development of alternative energy. One of the most promising sustainable alternatives to fossil fuel is biodiesel which is typically produced from the transesterification of refined vegetable oils using a homogeneous base catalyst. However, the current process limitations and steep production costs associated with the use of homogeneous catalysts have limited the global-wide acceptance of biodiesel. Heterogeneous catalysts have been considered suitable alternatives, but they still suffer from low catalytic activity. In this study, by using density functional theory (DFT) calculations, we examined the electronic and catalytic activity of the single Na-doped graphitic carbon nitrides (indicated by Na-doped g-C3N4) toward the efficient biodiesel (acetic acid methyl ester) production via the transesterification of triglyceride (triacetin). Our DFT calculation on reaction energetics and barriers revealed the enhancement of biodiesel productivity in the Na-doped catalyst compared to the pristine g-C3N4 catalyst. This was related to the large reduction of the barrier in the rate-limiting step. In addition, we investigated the acidity/basicity and electron distribution and density of state for the Na-doped and pristine g-C3N4 catalysts to better understand the role of the Na atom in determining the transesterification reaction. This study highlights the importance of the dopant in a g-C3N4 catalyst in determining the transesterification reaction, which may open new routes to improve biodiesel production. Full article
(This article belongs to the Special Issue Selected Papers from the 11th Asia-Pacific Forum on Renewable Energy (AFORE 2022))
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24 pages, 9471 KiB  
Article
Comparative Study on Shading Database Construction for Urban Roads Using 3D Models and Fisheye Images for Efficient Operation of Solar-Powered Electric Vehicles
by Jieun Baek and Yosoon Choi
Energies 2022, 15(21), 8228; https://doi.org/10.3390/en15218228 - 04 Nov 2022
Cited by 5 | Viewed by 1646
Abstract
Accounting for shadows on urban roads is a complex task in the operation of solar-powered electric vehicles. There have been few opportunities to compare the methods and tools for the construction of an effective shading database for urban roads. This study quantitatively investigated [...] Read more.
Accounting for shadows on urban roads is a complex task in the operation of solar-powered electric vehicles. There have been few opportunities to compare the methods and tools for the construction of an effective shading database for urban roads. This study quantitatively investigated and compared shading matrices generated from 3D models or fisheye images. Skymaps were formed considering the geometry of nearby shading obstructions. Sun-path diagrams tracking the position of the sun by time and season were overlaid on the skymaps, and month-by-hour shading matrices were calculated. Mean squared error (MSE) was used to clarify the quantitative differences between the shading matrices. The cases were divided into A, B, and C according to the presence of buildings and trees around the survey points. Under case A (trees), case B (buildings and trees), and case C (buildings), the average MSEs between the matrices were 24.5%, 23.9%, and 2.1%, respectively. The shading matrices using either 3D models or fisheye images provided accurate shading effects caused by buildings. In contrast, the shading effects of trees were more accurately analyzed when using fisheye images. The findings of this study provide a background for constructing shading databases of urban road environments for the optimal operation of solar-powered electric vehicles. Full article
(This article belongs to the Special Issue Selected Papers from the 11th Asia-Pacific Forum on Renewable Energy (AFORE 2022))
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13 pages, 3163 KiB  
Article
Regional Photovoltaic Power Forecasting Using Vector Autoregression Model in South Korea
by A-Hyun Jung, Dong-Hyun Lee, Jin-Young Kim, Chang Ki Kim, Hyun-Goo Kim and Yung-Seop Lee
Energies 2022, 15(21), 7853; https://doi.org/10.3390/en15217853 - 23 Oct 2022
Cited by 6 | Viewed by 1367
Abstract
Renewable energy forecasting is a key for efficient resource use in terms of power generation and safe grid control. In this study, we investigated a short-term statistical forecasting model with 1 to 3 h horizons using photovoltaic operation data from 215 power plants [...] Read more.
Renewable energy forecasting is a key for efficient resource use in terms of power generation and safe grid control. In this study, we investigated a short-term statistical forecasting model with 1 to 3 h horizons using photovoltaic operation data from 215 power plants throughout South Korea. A vector autoregression (VAR) model-based regional photovoltaic power forecasting system is proposed for seven clusters of power plants in South Korea. This method showed better predictability than the autoregressive integrated moving average (ARIMA) model. The normalized root-mean-square errors of hourly photovoltaic generation predictions obtained from VAR (ARIMA) were 8.5–10.9% (9.8–13.0%) and 18.5–22.8% (21.3–26.3%) for 1 h and 3 h horizon, respectively, at 215 power plants. The coefficient of determination, R2 was higher for VAR, at 4–5%, than ARIMA. The VAR model had greater accuracy than ARIMA. This will be useful for economical and efficient grid management. Full article
(This article belongs to the Special Issue Selected Papers from the 11th Asia-Pacific Forum on Renewable Energy (AFORE 2022))
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