Authorship：Lead author,　Last author,　Corresponding author   Language：English   Publisher：The Japan Society of Mechanical Engineers  

<p>Over the past three decades, solar energy has gained a lot of attention because of its energy potential and environmental-friendly aspect. To estimate its energy potential, most researchers use satellite approximation solar radiation data or imagery as their only data source, which is not sufficient as the images are taken high above the ground which results in the loss of the part of the resolution, and besides that, they also lack the hourly or daily variations, which is a critical component for an accurate estimation. This paper aims to provide the renewable energy research community with a low-cost and portable remote sensor for ground-based solar radiation and related data measurement. The remote sensor comprises a series of low-cost and accurate sensors, a single board computer, two Arduino micro-controllers, two Real Time Clocks, two mini-solar panels, an internet modem, two onboard batteries and six (6) relays, all interfaced in the Python Programming Language. The operation of the remote sensor is discussed in this paper along with a survey of its energy consumption. Data validation was done by comparing our recorded data with the Japan Weather Station data, and the result showed an accuracy of about 90%.</p>

DOI： 10.1299/jsmeicope.2021.15.2021-0254

CiNii Research

Authorship：Lead author,　Last author,　Corresponding author   Language：English   Publisher：The Japan Society of Mechanical Engineers  

<p>In this work, we analyse the potential grid stabilizing effects of the advanced double-effect adsorption thermal energy storage in decentralized and on-site domestic use. As the adsorption and thermochemical heat storage systems can provide both hot and cold, relative to the environment, the usage can be projected as continuous through the whole year for both air conditioning as well as hot water preparation. We show that the adsorption systems have the capability to elevate part of the immediate electric demands used for “hot and cold” preparation in the domestic and commercial environment as independent systems or in combination with other interactive parts of the electric grid. The adsorption thermal energy storage system introduced in this work can operate with high COP of >0.7 depending on the conditions and shows good energy stability over time. Additionally, the adsorption systems use thermal energy or electricity mainly for charging and only a negligible amount during the discharge. Hence, they can mitigate the adverse effects on the grid during the high demand periods and still deliver the necessary work while providing the grid operators with another stabilizing tool that can substantially enhance the effective utilization of renewable sources of energy.</p>

DOI： 10.1299/jsmeicope.2021.15.2021-0132

CiNii Research

Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Producing activated carbon (AC) with favorable properties using conventional physical activation from local biomass and understanding its water vapor adsorption behavior is essential to find renewable and low-cost material for dehumidification application. In this study, AC was prepared from Japanese Acorn Nutshell (JAN) under different preparation conditions. The prepared activated carbons were used to adsorb water vapor under diverse humidity range. The experimental results showed that Japanese Acorn Nutshell is suitable to be used as a precursor of activated carbon. The activated carbons produced in this study have the surface area up to 864 m²/g. On the other hand, water vapor adsorption isotherms on all prepared materials are following type V with steep uptake between P/Po of 0.4 to 0.6. From the water sorption isotherm data, the prepared activated carbon shows a promising ability to be used as a desiccant material.

DOI： 10.1299/jsmeenv.2020.30.411

CiNii Research

Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

The study aims at producing activated carbons from low-cost materials, such as agricultural and botanical waste, without using expensive chemicals. The activated carbons produced by low-cost methods would enhance the possibility of installing desiccant dehumidification in developing countries in hot and humid regions. In this paper, we report dehumidification capacity of activated carbons prepared from Japanese Acorn Nutshell under different preparation conditions based on the water adsorption isotherms. Firstly, the adsorption isotherm equations were generated based on the measured data. Then, the dehumidification capacity was predicted under several ambient air conditions.

DOI： 10.1299/jsmeenv.2020.30.412

CiNii Research

Authorship：Lead author,　Last author,　Corresponding author   Language：English   Publisher：Interdisciplinary Graduate School of Engineering Sciences, Kyushu University  

The stability of water molecular bridges (WaMB) is investigated on the ombrotrophic organic peatland type soil. The samples of the soil collected in the north part of Scotland (UK) near the city of Stornoway. The temperature dependence of the WaMB breaking point was measured through differential scanning calorimetry and shows how much are the organic structures inside the peat type soil susceptible to drying. The deeper peatland soil in this work showsmuch lower temperature values of WaMB breaking of around T ^ * ~ 47 °C compared to the top layer where the middle temperature of WaMB breakage is T ^ * ~ 58 °C, comparable to regular soil types. This temperature dependence shows higher susceptibility of the studied peal soil for drying and therefore higher sensitivity to changes in the water table levels and disturbance of the top layers of the soil system.

DOI： 10.15017/2552901

CiNii Research

Authorship：Lead author,　Last author,　Corresponding author   Language：English   Publisher：Interdisciplinary Graduate School of Engineering Sciences, Kyushu University  

Several materials were tested for their suitability as an adsorption heat storage medium. The main objective of the research was to test their adsorption properties in combination with water. The main observed properties were adsorption uptake, relative pressure of the adsorption and adsorption energy. The examined materials were selected from the groups of mesoporous silica nanoparticles (MSNs) and zeolites. From the observed materials the MSNs materials are showing the highest adsorption uptake up to 0.8 g/g of water which is due to their higher pore volume. However, most of the adsorption is occurring through the capillary condensation and the adsorption energy is then roughly equal to the water latent condensation energy which is about 41 kJ/mol. The zeolites are showing much higher adsorption energies but are greatly limited by the adsorbed amounts.

DOI： 10.15017/1960661

CiNii Research

Authorship：Lead author,　Last author,　Corresponding author   Language：English   Publisher：Interdisciplinary Graduate School of Engineering Sciences, Kyushu University  

Short rotation coppice (SRC) plantations of hybrid poplars are attractive for some farmers or owners of agricultural land due to the potential for energy production. The establishing plantations and energy use of wood from SRC plantations could be environmentally effective. On the territory of Slovakia and the Czech Republic are monitored by some Italian and Japan poplar clones with broad ecological amplitude. The results of observations lead to the conclusion not too encouraging for some growers of fast growing trees. The influence of SRC on the environment is not entirely positive as it is commonly known from the literature

DOI： 10.15017/1906160

CiNii Research

Authorship：Lead author,　Last author,　Corresponding author   Language：English   Publisher：Interdisciplinary Graduate School of Engineering Sciences, Kyushu University  

The necessity of antifreeze additives connected to climate conditions in automotive is a non-changing fact. For decades two substances, ethane-1,2-diol and propane-1,2-diol, are dominating the market with all of their advantages and disadvantages. In this paper is presented new potential antifreeze additive from the same family of polyols with different structural formula of propane-1,3-diol. Though similar to propane-1,2-diol the position of hydroxyl groups at the ends of the carbon parent chain gives this substance some unique properties that are distinguishable from its predecessors. Important physical properties for use as an antifreeze additive in automotive and solar heat systems were measured in controlled conditions and compared to the current additives such as propane-1,2-diol. Propane-1,3-diol shows especially favourable values for viscosity in wide ranges of temperatures and dilutions which lowers the needs for pump power and subsequently energy demands on the systems, alongside the advantage of being completely produced from renewable sources.

DOI： 10.15017/1906397

CiNii Research

Publishing type：Research paper (scientific journal)  

Adsorption heat transformer (AHT) cycle is capable of upgrading the low-grade waste heat to a higher temperature. The maximum temperature lift of the AHT cycle can represent its theoretical performance limit. However, such a metric is currently absent from the literature due to the scarcity of fundamental studies on the heat upgrading sorption cycles. Therefore, in the present study, three models are proposed to derive the ‘maximum temperature lift’ of a typical AHT cycle: (i) heat engine heat pump representation, (ii) the 2nd law of thermodynamic formulation, and (iii) complete preheating. The first two models are developed based on the reversible cycle approach, whereas the 3rd model incorporates adsorbed phase properties. Thus, the first two models might be considered as the formulations for the thermodynamic temperature limit (lift) of an AHT cycle while the 3rd model is specific to the nature of a particular adsorbent + adsorbate pair which might be close to practical applications. The reversible models predict a maximum temperature lift of 22 ∘C to 58 ∘C for heat source temperatures between 50 ∘C to 80 ∘C. The 3rd model exhibits lower values of maximum temperature lift compared to the reversible models, owing to the inclusion of material properties in its formulation. The performance of the models is demonstrated by determining the maximum temperature lift of four water-based adsorption working pairs, each featuring distinct IUPAC (International Union of Pure and Applied Chemistry) isotherm types. This study will help propel the working pair selection and the thermodynamic modeling of sorption cycles to achieve its near maximum capability.

DOI： 10.1016/j.ijheatmasstransfer.2024.125384

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Scopus

Publishing type：Research paper (scientific journal)  

Carbon capture, storage, and utilization from post-combustion processes using adsorption phenomena has emerged as a promising solution to the greenhouse gas emission crisis. The capacity of solid porous adsorbents dictates the performance of such carbon capture processes. Developments of porous adsorbents with favourable structural and chemical characteristics of the pore have been a major research area. Computational tools, notably the Grand Canonical Monte Carlo (GCMC) simulation, are widely employed to characterize the adsorption process in crystalline adsorbents like metal-organic frameworks and zeolites. Activated carbons are becoming promising alternatives to conventionally-used zeolite adsorbents for CO2 adsorption, because of their abundant microporosity and cost performance. However, the amorphous nature of the activated carbon materials poses a challenge in accurately modelling their pore characteristics and their adsorption process. Therefore, this study systematically explores the effect of pore size distribution and type of functional groups on the adsorption of CO2 on activated carbons using a simplified slit-pore graphite structure representing the activated carbon adsorbent. Four different pore sizes (7 Å, 8.9 Å, 18.5 Å, and 27.9 Å) and three oxygen-containing functional groups (Carbonyl, Hydroxyl, and Carboxyl) were selected to model the graphite structures. Results from the GCMC simulation reveal a significant rise in the CO2 adsorption capacity (from 4 mmol/g to 21 mmol/g) as the pore size was increased from 7 Å to 27.9 Å. Likewise, the functional groups enhance the low-pressure adsorption process by reducing the onset pressure of the pore filling by a factor of 100, especially in ultra-micropores. Likewise, we demonstrate the increase in the isosteric heat of adsorption due to the reduction in the pore size and the presence of functional groups. Additionally, the study illustrates the adsorbed phase behaviour of CO2 concerning the pore characteristics, a facet often overlooked in the existing literature. The adsorbed phase local density and molecular orientation distribution are analysed to understand the variation in the adsorption uptake and isosteric heat of adsorption properties. The study further identifies the adsorbed phase monolayer to multilayer transition and the ‘T′-shaped orientation of the adsorbed CO2 molecules as the key contributors to the high isosteric heat of adsorption in 8.9 Å pore size. It is envisaged that this study will navigate the precision adsorbent development for an efficient carbon capture process.

DOI： 10.1016/j.colsurfa.2023.133113

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Scopus

Publishing type：Research paper (scientific journal)  

Solar energy is an important energy source for a sustainable future. The advancements of solar cells for electricity production require improvements in the cooling technology. Conventional air cooling is not able to cool the photovoltaic (PV) panels effectively. On the other hand, dew-point evaporative cooling (DPEC) can bring down the inlet air temperature below its wet bulb which makes itself an excellent candidate for PV cooling. In this work, a novel cooling configuration that consists of two wet channels: one in the cooler (conventional DPEC) to produce the pre-cooled supply air and the other at the back of the PV panel, was proposed. A physics-based mathematical model utilizing local weather conditions was developed for the system to investigate its transient performance. The cooling performance and subsequent improvement in the PV's energy efficiency of the proposed system were compared with a traditional DPEC-based cooling approach. It was observed that the proposed system can maintain an efficiency of more than 15% (with 16.7% maximum) under two environmental conditions in summer, which is an increase of 16.4% compared to air cooling. The proposed PV cooling method will help to improve the overall performance of the solar PV systems and increase renewable energy utilizations.

DOI： 10.1016/j.applthermaleng.2023.121695

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Scopus

Publishing type：Research paper (scientific journal)  

Activated carbon, due to its notable porosity and cost-effectiveness, emerges as a promising desiccant material. This research delves into the utilization of pinecones as a precursor for the production of activated carbon through steam activation. The resultant activated carbon samples presented a porous structure and exhibited a high water adsorption capacity, with the highest adsorption capacity reaching 0.35 kg/kg, placing it in competition with commercial silica gel. Various experimental parameters were systematically manipulated during the production process to optimize both the pore structure and water adsorption capacity of the activated carbon samples. Elevating the carbonization temperature from 700 °C to 900 °C proved effective in enhancing pore distribution and elevating water adsorption capacity. Furthermore, higher activation temperatures contributed to the formation of additional mesopores and macropores, possibly attributable to micropore enlargement through steam activation. Nevertheless, these elevated activation temperatures resulted in an undesired increment in mesopores concerning water adsorption. The extension of activation time led to increased micropore formation, albeit with concurrent disruption, culminating in heightened total pore volume and surface area. This extension shifted the water adsorption-desorption isotherm to higher relative pressure ranges, accompanied by a larger hysteresis loop. Moreover, an increased steam mass flow rate was found to enhance the pore structure and water adsorption capacity of the activated carbon. The activated carbons exhibited sigmoid-shaped isotherms, signifying their suitability for both open-cycle and closed-cycle adsorption systems.

DOI： 10.1016/j.powtec.2023.119084

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Scopus

Publishing type：Research paper (scientific journal)  

Hydrogen gas is among the sustainable energy forms that counteract the energy crisis. Polymer electrolyte membranes (PEMs) derived from biomass fillers and polyvinyl-based matrix blends have been fabricated and applied in H2 generation through electrolysis. Faradaic efficiencies ranging from 82.8 ± 1.9% to 88.9 ± 1.6% were exhibited when voltages of 6.5 V, 8 V and 10 V were applied; thus, proton conduction and hence H2 generation commenced at 2-2.5 V. The apparent morphology of the PEMs that verified the incorporation of pine bark (PB) and Chinese Tallow Seed Capsule (CT) fillers was visible as surface bumps and internal cavities within the PEMs. Although the proton conductivity of Nafion™ 115's (NF-M) was 23.94 mS cm-1, those of the fabricated PEMs (PB-M, CT-M and SSA-M) were 1.33, 0.46 and 0.48 mS cm-1, respectively. The PB-M exhibited good characteristics, including functional groups and water adsorption; thus, H2 production was achieved, but losses such as bubble production affected efficiency. This study presents a cost-effective alternative for H2 production that can be used in diverse applications.

DOI： 10.1039/d3ya00503h

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Scopus

Publishing type：Research paper (scientific journal)  

Adsorption heat transformer (AHT) cycles, unlike adsorption cooling cycles, upgrade the heat source to a higher temperature. Despite the renewed interest in the AHT cycles, its performance enhancement schemes along with their impacts are yet to be explored extensively. Heat and mass recovery schemes on the adsorption cooling/heating cycles have been extensively studied. However, AHT cycles are fundamentally different from those cycles since the AHT cycles employ isothermal-adiabtic processes. Thus, similar impacts of the heat and mass recovery scheme as in the cooling/heating cycles cannot be expected in AHT cycles. Therefore, the impacts and limitations of the internal heat recovery scheme on the AHT cycle are investigated in the current study. The heat recovery scheme aims to minimize the requisite uptake consumption for preheating the adsorber bed by recovering the sensible heat between two adsorber beds having different temperatures. This sensible heat exchange is modeled using modified energy-balance equations to capture the non-linearity of the adsorption process. The preheating uptake loss decreases from 0.014 kg/kg to 0.007 kg/kg at the heat source-heat supply temperature combination of 60 °C–80 °C due to the maximum possible heat recovery in the AHT cycle. As a result of the reduced preheating uptake loss, approximately 5% and 10% increase in the useful heat ratio and exergy efficiency of the AHT cycle, respectively are obtained. This modified AHT cycle further improves the performance ratio of the hybrid AHT-MED (multi-effect distillation) system from 4.6 to 4.9 at the heat source temperature of 58 °C. Furthermore, a parametric analysis of the cycle's performance metrics has been conducted for various degrees of heat recovery, representing the effect of realistic heat exchanger effectiveness during the recovery process. This study will help propel the theoretical development of the adsorption-based thermodynamic systems.

DOI： 10.1016/j.icheatmasstransfer.2023.106774

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Scopus

Publishing type：Research paper (scientific journal)  

The use of technology in everyday life is unavoidable, considering that technological advancement occurs very quickly. The current era is also known as industry 4.0. In the industry 4.0 era, there is a convergence between the industrial world and information technology. The use of modern machines in the industry makes it possible for business actors to digitize their production facilities and open up new business opportunities. One of the developments in information technology that is being widely used in its implementation is machine learning (ML) technology and its branches such as computer vision and image recognition. In this work, we propose a customized convolutional neural network-based ML model to perform image classification technique for Indonesian herb image dataset, along with the detailed review and discussion of the methods and results. In this work, we use the transfer learning method to adopt the opensource pre-trained model, namely, Xception, developed by Google.

DOI： 10.1515/eng-2022-0385

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Scopus

Publishing type：Research paper (international conference proceedings)  

Shear wall structures are a possible option as a suitable lateral load-bearing system for new structures or as a means of retrofitting existing buildings. One of which is Steel Plate Shear Walls (SPSW). In improving its function, thin SPSW can be added by stiffener, but as consequences, it increases construction costs due to the time-consuming factor and the high cost of welding thin plates. Therefore, modification of the infill shape was carried out to increase the energy dissipation capacity of the SPSW. This study simulates the experimental results of trapezoidal vertical corrugated steel shear wall specimens. The specimens were modelled and tested using Finite Element Analysis (FEA) in the ABAQUS application. To simulate earthquake loads and observe cyclic behavior, a quasi-static cyclic test is used that uses a horizontal in-plane load history. The gravity load is neglected, and a displacement load is applied to the top of the specimen. The load circuit applied is displacement control by increasing or decreasing the amplitude. The results compared are hysteresis behaviour. In addition, the contours that occur are also observed in this study.

DOI： 10.1016/j.prostr.2023.07.007

Scopus

Publishing type：Research paper (international conference proceedings)  

Particulate matter (PM) accumulation on the leaves of two trees and two shrubs were examined for 14 days to study the ability of broad leaves to capture particulate matter in Japan. Two healthy mature leaf samples of each specimen were carefully collected and analyzed through the gravimetric analysis method (four filtration steps). PM in different divisions can be captured and deposited inside the leaf foliage. Fine particles were the highest portion of the PM content captured by the analyzed trees. Leaf features such as hair and wax have been associated with high PM accumulation as presented in Toxicodendron succedaneum (waxy glossy leaves) which was the most effective species among the analyzed species for all PM fraction divisions (PM10, PM 2.5, and PM 0.2), and Prunus × yedoensis (hairy leaves) that captured the largest portion of ultra-fine PM. The surface area has no effect on the accumulation of particulate matter since the Ficus erecta shrub has the largest surface area, but the lowest portions of PM among of the investigated species.

DOI： 10.1007/978-981-99-4101-8_20

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

Thermally driven desiccant- and evaporative cooling-based technologies are promising greener and cheaper alternatives to compressor-based systems due to the separate handling of latent and sensible loads. Desiccant air-conditioning (DAC) systems comprise a desiccant dehumidifier, a sensible cooling unit, a heat source for regeneration, and a heat recovery unit. These components of a DAC system can be arranged in various ways to give different configurations with varying advantages and disadvantages. In this study, five configurations of thermally driven desiccant dehumidifier- and dew point evaporative cooling (DPEC)-based DAC systems were investigated. Seven evaluation criteria namely regeneration temperature, desiccant moisture removal capacity, COPt, DPEC L/H, heat exchanger UA, system size, and fan power requirement were employed. Results show that the standard cycle in ventilation mode offers the highest COPt despite having the highest regeneration temperature. Recirculation of the return room air can operate at a significantly lower regeneration temperature at the expense of larger equipment size and much lower COPt. DAC with an internally cooled dehumidification can operate at low regeneration temperature at the expense of higher fan power and slightly lower COPt. Dividing the dehumidification process into two stages can offer operation at moderately lower regeneration temperature without severely affecting the other criteria. This study can serve as a guide for the selection of an appropriate DAC configuration for space cooling depending on the objective criteria and the resources available.

DOI： 10.1007/s44189-022-00011-7

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Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Refrigerating and Air Conditioning Engineers  

<p>Nanotailored microporous silica represents one of the more recent artificially prepared advanced materials used in heat transformation and conservation field after silica gel and various zeolite and zeolite-like materials. In this work, we introduce experimental findings on the energy characteristics of water adsorption on nanotailored microporous silica with 1.5 % aluminium doping in the structure. The downscaled system in this work simulates actual working conditions in a controlled environment for both heating and cooling mode. The key properties of this material lie in the regeneration temperatures 60 to 80 ℃ and COP, which reaches values around 0.6 in case of cooling and 0.7 in case of heating. In absolute values at Δ<i>T</i> = 15 ℃, the system reaches storing capacities of about 90 Wh and 126 Wh per adsorbent kilogram in terms of cooling and heating potential energy, respectively. An important factor of kinetic influence on system performance is discussed on a basis of constant time experiment and time-dependent energy flow breakthrough analysis. Constraining factors are found to be in parallel through the driving force of the pressure swing as well as the heat transfer through the body of the adsorption bed.</p>

DOI： 10.11322/tjsrae.21-37DE_EM_OA

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)  

Humidification-dehumidification desalination (HDD) systems offer a feasible approach for the production of fresh water in inaccessible areas as they can be operational using renewable energy and require little maintenance. Various studies are being carried out to boost the system performance. In this paper, an open air open water HDD system is proposed that exploits the enhanced evaporation and condensation processes by implementing with the Maisotsenko cycle (M-cycle). The system utilizes solar energy as the energy input to heat the saline water. A thermodynamic model is formulated under steady-state conditions, considering the first and second law of thermodynamics. The energetic and exergetic performance of the system is studied. The model is first validated with the experimental data and a good agreement is found where the maximum discrepancy is about 6.0 %. Effects of different operating conditions on key performance parameters such as the Gain Output Ratio (GOR), specific energy consumption (SEC), exergy destruction, and exergy efficiency are analyzed. An improvement is observed in the GOR when the inlet air temperature is raised at constant humidity ratio. The system exhibits better performance in dry air environment when compared with humid air environment. The analysis shows a maximum mass flow rate of desalinated water of 22.3 kg/h, recovery ratio (RR) of 0.223, GOR of 3, SEC of 0.23 kWh/kg and an exergy efficiency of 43.21 %.

DOI： 10.1016/j.seta.2022.102141

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Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

This paper presents a comparative analysis of the potential working fluids for a promising thermodynamic cycle (Thermal Power Pump cycle) for the utilisation of low-grade heat. The cycle was analyzed along with nucleate boiling correlations and film condensation analysis for variable heat source temperatures (50–150°C) using nine potential working fluids. The working fluids showed varying degrees of cycle performance and system size requirements. Among the working fluids, cyclopentane seems to be an attractive choice of working fluid, due to its superior cycle performance over the wide range of heat source temperatures with moderate system size requirements. For temperatures above 146°C and below 60°C, water and n-pentane are selected, respectively. Working fluids with stronger molecular forces seem to approach the properties of an ideal working fluid for better performance of the system.

DOI： 10.1080/14786451.2021.1924717

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Scopus

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Refrigerating and Air Conditioning Engineers  

<p>Water vapor adsorption on activated carbon (AC) for dehumidification purposes has gained much attention due to the abundance of benefits provided by AC. The working region limited in high water vapor relative pressure (<i>P/P0</i>) makes this material suitable only for removing water vapor at a highly humid region. In this study, ozone oxidation was conducted to introduce more oxygen-based functional groups on AC to attract more water molecules. Based on surface characterization results, ozone oxidation increases oxygen functional groups such as carboxylic on AC but decreases their pores. The more AC exposed to ozone, the more different properties could be observed. The increment of functional groups enhances the water vapor adsorption uptake at <i>P/P0</i> ≤ 0.6, shifting the water sorption into lower <i>P/P0</i>.</p>

DOI： 10.11322/tjsrae.21-36DE_EM_OA

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers and The Heat Transfer Society of Japan  

Renewable energy-based microgrid systems are widely being studied as electrification methods for rural communities in developing countries. Waste heat generated by the components of the microgrid systems, such as the biogas driven generators (BDG), presents the potential of utilizing the low-grade heat in a way that can contribute to the sustainability of such energy systems. From the points of view of affordability, local manufacturability, and applicability for agriculture, thermally driven pumps (TDP) may be attractive for coupling with such microgrid systems. Therefore, the current study has focused on the development of a new type of thermally driven pumping system as a potential waste heat utilization component for microgrid applications in rural areas. A liquid piston-type TDP concept without moving parts, except few valves, was developed and parametric experimental investigations were carried out. The performance and characteristics of the system were studied, which revealed that the proposed system has a superior performance compared to the literature. It was also found that the system performance strongly depends on the heat addition rate and delivery capacity of the system, which are suitable characteristics for the intended application. Hence, the experimental data were used to estimate whether the proposed system can pump enough water that needs to be supplied for the biogas production to supply a 10 kW BDG unit of a microgrid. It was found that 87 – 93% of the total pumped water (13 – 27 m3) would be available for agricultural and other purposes while only 6 – 13% would need to be fed to the biogas digester. Generally, the results seem to be promising, and yet there are potentials for the optimization and improvement of the proposed system, hence they have been pointed out.

DOI： 10.1299/jtst.21-00323

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Scopus

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)  

The desiccant dehumidification system can separate the latent heat and sensible heat in the air-conditioning system and achieve energy savings by removing latent heat. Industrial waste heat and renewable energy could be utilized in desiccant dehumidification systems, where the desorption process can be performed below 70 °C. The vapor pressure and temperature of the regenerating air dictate the desorption process corresponding to the isotherm properties. This study has focused on the effects of various temperatures and humidity ratios of regeneration air on the performance of a desiccant dehumidifier using a polymer as an adsorbent. Experiments were performed using the regeneration air with the humidity ratios of 0.005 kg kg−1, 0.010 kg kg−1, 0.015 kg kg−1, and 0.020 kg kg−1, while the air temperatures were varied from 40 °C to 70 °C. The evaluation of this study employs the adsorption/desorption amount, average moisture removal capacity, and latent energy ratio (LER) of the regeneration process as key performance indexes. At the regeneration temperature of 68 °C, the peak desorption amount at the humidity ratio of 0.005 kg kg−1 and 0.010 kg kg−1 both reached 0.011 kg kg−1. The results indicated that the higher desorption temperature led to a higher desorption amount. Besides, with the increased desorption temperature, the average moisture removal capacity increases. In contrast, the high humidity ratio of regeneration air resulted in a weak dehumidification ability. Lower regeneration temperature was difficult to apply to regenerate the polymer-based desiccant under a high-humidity-ratio atmosphere. To attain a high LER, a lower humidity ratio of dry air and regeneration temperature was preferred. The regeneration air with a humidity ratio of 0.020 kg kg−1 is not suitable to apply in the dehumidification system in the temperature range of 40–70 °C.

DOI： 10.1007/s10973-022-11368-7

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Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Interdisciplinary Graduate School of Engineering Sciences, Kyushu University  

In order to utilize the adsorption chiller or heat pump as a next-generation air conditioning system, several issues still remain, such as performance improvement, miniaturization, and cost reduction. It is known that the activated carbon-freon refrigerant pair has a relatively lower coefficient of performance (COP) than the silica gel-water or freon refrigerant pair and zeolite-water pair. However, there is a possibility to contribute minimize the adsorption heat pump system utilizing Freon refrigerant since it works in high-pressure regions and has a high saturation vapor density. Therefore, evaluating and improving the performance of Freon refrigerant is an important future task.

DOI： 10.5109/5909083

Scopus

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Elsevier {BV}  

Desiccant dehumidification systems can be utilized for decoupling moisture removal duty from the conventional mechanical vapor compression systems. Dehumidification using desiccant dehumidifiers is expected to exhibit a better energy efficiency. However, the high energy needed in the regeneration process limits its applicability. To realize the full potential of this technology, it is necessary to develop materials that can be regenerated using heat sources under 70 °C. In this study, activated carbons (ACs) derived from waste biomass were developed as desiccant materials. The ability of activated carbon (AC) to remove the moisture was controlled by carefully preparing the material to achieve the right operation window for optimum moisture sorption processes. The porous and surface characteristics of the newly-prepared AC were analyzed and compared with those of silica gel. The adsorption isotherm measurements were conducted, and the data were fitted with Henry–Sips and Do–Do isotherm models. The current ACs exhibit an excellent water adsorption capacity (up to 0.41 g/g). The efficacy of the ACs for dehumidification applications was assessed using the weather data from several regions of Indonesia, from North Sumatera to Papua. The results revealed that under the studied conditions, the new desiccant material showed a better dehumidification capacity than silica gel. Moreover, the reported AC can be regenerated using temperatures as low as 40 °C, which is readily available from waste heat, including the heat rejection from the condenser of an air-conditioning unit.

DOI： 10.1016/j.egyr.2021.09.003

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Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Elsevier {BV}  

Indoor air humidity plays a vital role in determining occupants’ health and industrial product quality. Removing excess humidity by adsorption dehumidification is still facing a challenge in finding a suitable material with high adsorption capacity and low regeneration temperature. In this study, the theoretical dehumidification capacity of prepared acorn nutshell-based activated carbons was calculated and compared with silica gel type RD and RD-2060. The calculation was based on the outdoor air condition in two Asian capital cities: Jakarta and Tokyo. The theoretical study found that prepared activated carbon has better dehumidification performance under Jakarta conditions using regeneration temperatures of less than 60°C. Under Tokyo conditions, activated carbon shows auspicious performance during the summer season. Compared with silica gels, acorn nutshell-based activated carbon has a better dehumidification capacity to process high humidity ambient air with a lower regeneration temperature.

DOI： 10.1016/j.ijrefrig.2021.08.012

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Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

In this study, we evaluated the performance of low Global Warming Potential (GWP) refrigerant R1234yf on the activated carbon (MSC‐30) for adsorption heating applications. The ad-sorption isotherms of MSC‐30/R1234yf were measured using a constant‐volume–variable‐pressure (CVVP) method from very low relative pressure to the practical operating ranges. The data were fitted with several isotherm models using non‐linear curve fitting. An improved equilibrium model was employed to investigate the influence of dead thermal masses, i.e., the heat exchanger assembly and the non‐adsorbing part of the adsorbent. The model employed the model for the isosteric heat of adsorption where the adsorbed phase volume was accounted for. The performance of the heat pump was compared with MSC‐30/R134a pair using the data from the literature. The analysis cov-ered the desorption temperature ranging from 60 °C to 90 °C, with the evaporation temperature at 5 °C and the adsorption temperature and condensation temperature set to 30 °C. It was observed that the adsorption isotherms of R1234yf on MSC‐30 were relatively lower than those of R134a by approximately 12%. The coefficient of performance (COP) of the selected pair was found to vary from 0.03 to 0.35 depending on the heat source temperature. We demonstrated that due to lower latent heat, MSC‐30/R1234yf pair exhibits slightly lower cycle performance compared to the MSC‐ 30/R134a pair. However, the widespread adaptation of environmentally friendly R1234yf in auto-mobile heat pump systems may call for the implementation of adsorption systems such as the direct hybridization using a single refrigerant. The isotherm and performance data presented in this work will be essential for such applications.

DOI： 10.3390/app11052279

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

Adsorption cycles have been gaining significant interest in waste-heat recovery and renewable energy utilization. Adsorption isotherm data and the equilibrium cycle analysis are crucial steps in evaluating a typical adsorbent + adsorbate pair. In this paper, the performance of Maxsorb III + R245fa and spherical activated carbon, SAC-2 + R245fa were studied for adsorption cooling and adsorption heat transformer (AHT) cycles. Adsorption isotherms of these pairs were measured using the constant-volume-variable-pressure apparatus for temperatures ranging from 30 °C to 60 °C, and fitted with the Dubinin–Astakhov (D–A) and the Tóth isotherm model. An improved equilibrium model was developed, accounting the effects of thermal masses. The specific cooling energy (SCE) and the coefficient of performance (COP) of the adsorption cooling cycle were evaluated for various thermal mass to adsorbent mass ratios. It is observed that SAC-2 + R245fa pair offers better SCEs (20 kJ kg−1and 160 kJ kg−1 at 60 °C and 90 °C, respectively) when compared to that of Maxsorb III + R245fa. The impact of thermal mass is found to be significant for all regeneration temperatures for Maxsorb III + R245fa while the deterioration of COP in SAC-2 + R245fa is notable for high regeneration temperatures (> 75 °C). When employed in the AHT cycle, Maxsorb III offers a slightly higher useful heat while SAC-2 provides a better Quh/QQR albeit by a small margin. The Quh/QQR values for both studied pairs are more than 0.6 for all regeneration temperatures for the heat extraction at 120 °C.

DOI： 10.1016/j.ijrefrig.2020.12.005

Web of Science

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Interdisciplinary Graduate School of Engineering Sciences, Kyushu University  

As an environment-friendly approach for low-grade thermal utilization, adsorption technology has received more and more attention since it can have a plethora of applications, such as thermal energy storage, heat pumps and carbon dioxide capture etc. The performance of this technology is highly affected by the heat and mass transfer efficiency in the adsorption heat exchangers. This minireview is focused on recent studies and investigations on performance improvement of the adsorption heat exchangers, especially on the improvement of the thermal conductivity of adsorbents, the reduction of the thermal contact resistance, and the improvement of the heat exchange area. Discussion on the future research required to improve the heat and mass transfer performance was presented. These technologies and results are expected to provide insights and guidance for performance improvement of both adsorption heat pumps and adsorption thermal energy storage systems.

DOI： 10.5109/4738594

Scopus

CiNii Research

Publishing type：Research paper (international conference proceedings)  

Various technologies for renewable energy need to be employed for sustainability and the hydrogen production through water electrolysis (WE) is one of the green energy approaches. In this study, solar energy was used for splitting sodium chloride solution into hydrogen gas using an experimental electrolyzer, while the hydrogen production and the performance of the PV cell were evaluated. The incoming solar radiation ranged from 810.1 W/m2 to 637.8 W/m2 whereas the respective atmospheric temperature increased, and humidity subsequently decreased. The efficiency of WE (ȠF) was 61.8% and the PV cell efficiency (ȠSP; at temperature; 25.5oC, humidity; 42.2% and IR; 810.1 810.1 W/m2) was 12.7%. The H2 production was coupled with voltage drop whose minimization needs to be addressed in future research along with improvement of efficiency and costeffectiveness.

DOI： 10.46855/energy-proceedings-9303

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Elsevier {BV}  

Adsorption thermal energy storage plays a vital role in supporting the availability of renewable energy. Activated carbons produced from local waste biomass have been attracting considerable attention in adsorption technology due to their unique properties and sustainability. However, their limitation in water vapor uptake hinders the practical application of this material. In this work, acorn nutshells were utilized as a base material to produce activated carbon. Air oxidation was performed as a versatile and low-cost technique to enhance the material's properties and water adsorption capacity. By applying air oxidation as a post-treatment during material production, the amount of active functional groups and the water adsorption on activated carbon has been successfully enhanced. From the theoretical calculation, it is found that activated carbon–water working pairs shown promising performance to be used for adsorption thermal energy storage applications. The adsorption of water vapor on the post-treated-activated carbon releases the isosteric heat between 2400 kJ/kg to 2500 kJ/kg. Moreover, this study's working pair can be driven by a temperature of less than 50 °C. From the results, it is confirmed that by controlling the adsorbent's surface properties, activated carbon–water working pairs can be a promising way to provide alternative material and reduce the energy demand for driving the system.

DOI： 10.1016/j.egyr.2020.11.038

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：{MDPI} {AG}  

A new model of adsorption isotherms Type IV and V is proposed as a basis for theoretical calculations and modelling of adsorption systems such as adsorption heat storage and heat pumps. As the current models have decent yet limited applicability, in this work, we present a new combined model with universal use for micro-mesoporous silica/water adsorption systems. Experimental measurement of adsorption isotherm of water onto seven different samples of micro and mesoporous silica and aluminium-silica were used to fit new adsorption models based on a combination of classical theories and a distribution function related to the pore-size distribution of the selected materials. The fitting was conducted through a repeated non-linear regression using Trust Region Reflective algorithm with weighting factors to compensate for the scalability of the adsorption amount at low relative pressure with optimization of the absolute average deviation fitting parameter. The results display a significant improvement for most of the samples and fitting indicators compared to more common models from the literature with average absolute deviation as low as AAD = 0.0025 g g−1 for material with maximum uptake of q = 0.38 g g−1. The newly suggested model, which is based on a combination of BET theory and adjusted normal distribution function, proved to bring a higher degree of precision and universality for mesoporous silica materials with different levels of hydrophilicity.

DOI： 10.3390/en13164247

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (international conference proceedings)  

This work focuses on experimental assessment of nano-tailored microporous silica doped with 1.5 % of aluminium in adsorption chiller application. The mean pore size of the selected material is ~1.8 nm. The addition of aluminium shows a significant increment of the adsorption of water in the experimental setup in the lower region of adsorption. The tested amount was approximately 100 grams in a closed-loop one cycle adsorption chiller system in a fully controlled environment to test the energy output and energy capacity of the material in combination with the water evaporative cooling in downscaled system. The material was tested under different conditions focusing on input temperature and cooling output at different flowrates. Compared to the theoretical values based on the measurements of adsorption isotherms the actual experimental values exhibit diminution in all parameters due to various thermal losses in the practical system. The potential of the material, however, shows better results in comparison to many other typical adsorption materials for this application such as silica gel and some zeolitic materials.

DOI： 10.18462/iir.gl.2020.1201

Scopus

Language：English   Publishing type：Doctoral thesis  

DOI： 10.15017/2534478

Language：English   Publishing type：Research paper (scientific journal)  

A detailed investigation on the main characteristics was conducted on a novel and unique group of industrially produced mesoporous silica material. Six materials from a TMPS group were selected in the respect to their pore size ranging from 1.8 nm up to 4.2 nm. Four of the selected samples were also made with silica doping making them potentially attractive for water adsorption applications with the advantage of the pore-tuning possibilities for specific use. The surface area, pore volume and pore size distribution of these materials were established by standard nitrogen adsorption at T = 77.4 K showing typical values of mesoporous silica materials such as high surface area in the range from 600 to 750 m2g−1 and pore volumes reaching 0.38 cm3g−1 in the case of the smallest TMPS-1.5A and 0.98 cm3g−1 in the case of the largest TMPS-4R. The wall thickness was found out regular around 1.5 ~ 2 nm with lower values attributed to bigger pore sized samples promising good structural integrity. Specific heat showed regular values through all the samples at ~ 0.85 J g−1K−1. Additional information on the structural characteristics and the effect on the amount of silanol group presence and the difference on regular and aluminium-doped samples were studied by means of 29Si DD/MAS NMR. Additionally, elemental analysis by EDS was conducted as well. All the characteristics of the TMPS materials were compared to the standard mesoporous silica materials SBA-15 and MCM-41.

DOI： 10.1016/j.micromeso.2019.109644

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media {LLC}  

Six samples from the TMPS family of mesoporous silica nano-materials from Taiyo Kagaku Co., Ltd. were studied for their potential as a medium for the adsorption thermal energy storage. Selected specimens are distinguished by their pore size from 1.9 to 4.1 nm and aluminium doping. As the adsorbate for the adsorption pair was selected water with the most advantageous properties of high latent heat and safe chemical properties. The tested materials doped with aluminium show high affinity towards the selected adsorbate and high uptakes. The theoretical storage energy density of the materials spans from 700 to 1700 kJ kg−1 based on the adsorption heat. The storage capacity depends mostly on the pore volume and partially on the pore size. The theoretical estimation shows the temperature gain of the adsorption potential as high as ΔT=23∘C for the material TMPS-1.5A with the smallest pore diameter and aluminium doping and as low as ΔT=6∘C for the TMPS-4R with the biggest pore diameter and without aluminium doping.

DOI： 10.1007/s10450-019-00107-4

Web of Science

Scopus

Publishing type：Research paper (international conference proceedings)  

The stability of water molecular bridges (WaMB) is investigated on the ombrotrophic organic peatland type soil. The samples of the soil collected in the north part of Scotland (UK) near the city of Stornoway. The temperature dependence of the WaMB breaking point was measured through differential scanning calorimetry and shows how much are the organic structures inside the peat type soil susceptible to drying. The deeper peatland soil in this work shows much lower temperature values of WaMB breaking of around T* ~ 47 °C compared to the top layer where the middle temperature of WaMB breakage is T* ~ 58 °C, comparable to regular soil types. This temperature dependence shows higher susceptibility of the studied peal soil for drying and therefore higher sensitivity to changes in the water table levels and disturbance of the top layers of the soil system.

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

A detailed investigation into the viscosity, density, and refractive index of a binary mixture of propane-1,3-diol/water was performed for the whole range of mass fractions of propane-1,3-diol. The viscosity and density were measured over a wide range of temperatures from T = 253.15 K to T = 353.15 K where possible, or to the nearest safe point before freezing. The refractive indices were measured for the same dilutions as in the case of the viscosity and density over a reduced temperature range of T = (278.15 to 318.15) K. A mathematical analysis via excess properties was conducted and fitted to the Redlich-Kister equation. Furthermore, a prediction of density data is provided by a polynomial and DIPPR exponential model. The viscosity data are fitted to Grunberg-Nissan, Lederer, McAllister, and Heric models and a new combined model with variable temperature and molar and mass fractions based on these models is presented. Data comparison of the propane-1,3-diol/water binary mixture is performed on propan-1,2-diol/water mixture as the physically closest binary system and application alternative fluid.

DOI： 10.1021/acs.jced.8b00403

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.18462/IIR.TPTPR.2017.0112

Web of Science

Event date： 2019.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Okinawa   Country：Japan  

Event date： 2019.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Kanazawa   Country：Japan  

Event date： 2019.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Fukuoka   Country：Japan  

Event date： 2019.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Hradok pri Jelsave   Country：Slovakia  

Event date： 2019.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Vemyslice   Country：Czech Republic  

Event date： 2018.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Hradok pri Jelsave   Country：Slovakia  

Event date： 2018.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Pusan   Country：Korea, Republic of  

Event date： 2018.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Fukuoka   Country：Japan  

Event date： 2017.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Fukuoka   Country：Japan  

Event date： 2017.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Tokyo   Country：Japan  

Event date： 2017.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Tokyo   Country：Japan  

Event date： 2017.4

Language：English   Presentation type：Oral presentation (general)  

Venue：Seol   Country：Korea, Republic of  

Event date： 2014.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Brno   Country：Czech Republic  

Language：English   Presentation type：Oral presentation (invited, special)  

Event date： 2014.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Hrádok   Country：Slovakia  

Event date： 2013.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Blansko   Country：Czech Republic  

Event date： 2012.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Hrádok   Country：Slovakia  

Event date： 2012.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Hrotovice   Country：Czech Republic