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Water Vapor Adsorbent FAM-Z02 and Its Applicability to Adsorption Heat Pump
Abstract
CHA-type structure silicoaluminophosphate zeolite (SAPO-34) was examined as an AHP adsorbent and the influence of silicon content on its adsorption performance was evaluated. SAPO-34 with silicon content of 7.5 mol% (Functional Adsorbent Material-Zeolitc 02; FAM-ZO(2)) was selected for further testing. The water vapor adsorption isotherm of FAM-ZO2 was S-shaped and highly dependent on temperature, and a small hysteresis was observed with adsorption/desorption at 363K. No changes were observed in the properties of FAMZO(2) after 100000 cycles of water vapor adsorption-desorption, indicating that FAM-ZO(2) is Suitable durable for practical use. When the AHP was operated under conditions of T,(L)/T-M/T-H=283 K/313 K/363 K, the adsorption capacity of FAM-ZO(2) was 4.8 times and 3.8 times those of Y zeolite and silica gel.
... Notice that the error bars in the experimental adsorption isotherms are indistinguishable from the reported mean values, since the accuracy of the dynamic gravimetric vapor sorption analyzer is in the order of few micrograms. A comparison among the experimental equilibrium data measured in this work and the results from Kayal et al. [36], Kakiuchi et al. [41] and Goldsworth [42] is reported in Fig. 4. The measured adsorption isotherms were almost at the same temperature (i.e. maximum difference 5 K), showing, in general, a good agreement. ...
... (1) provides an average isosteric heat of adsorption of water onto SAPO-34 equal to 61.8 kJ/mol in the range 0-0.4 p p / 0 . This value is in good agreement (i.e. ± 6% discrepancies) with the average isosteric heat of adsorption of water onto SAPO-34 found in the literature: 60.3 kJ/mol by Kayal et al. [36], 65.8 kJ/mol by Jänchen et al. [44], 58.2 kJ/mol by Kakiuchi et al. [41] and 64.8 kJ/mol by Sun et al. [45] (estimations). ...
... Comparison between measured water adsorption isotherms of SAPO-34 (AQSOA Z02) and data from Kayal et al.[36], Kakiuchi et al.[41] and Goldsworth[42], at about (a) 303 K and (b) 333 K. The reported relative pressures are referred to the saturation pressure of water at the temperature at which the isotherms are evaluated. ...
SAPO-34 – a silicoaluminophosphate microporous material – has recently attracted a great attention in the field of sorption thermal storage, since it is characterized by good water adsorption behavior (i.e. type V adsorption isotherms) and low regeneration temperature (i.e. 80 °C, for instance available by standard solar thermal energy collectors). However, the nanoscale mechanisms of water transport and adsorption in the microporous framework of SAPO-34 cannot be fully unveiled by experiments alone. In this work, water adsorption onto SAPO-34 is for the first time studied by means of an atomistic model built upon experimental evidence. First, Monte Carlo simulations are employed to set up a convenient atomistic model of water/SAPO-34 interactions, and numerical adsorption isotherms are validated against experimental measures. Second, the validated model is used to study the water diffusion through SAPO-34 by molecular dynamics simulations, and to visualize preferential adsorption sites with atomistic detail. Such atomistic model validated against experiments may ease the investigation and in silico discovery of silicoaluminophosphates for thermal storage applications with tailored adsorption characteristics.
... The studied adsorber configuration consists of a compact flat tubes HEx widely employed in adsorption chiller prototypes, which main characteristics are reported in [18] and summarized in Table 4. The adsorbent material considered is a commercial water sorbent named Mitsubishi AQSOA FAM Z02 [22][23][24]. ...
... For all the adsorbers, the water sorbent used was the Mitsubishi FAM-Z02 with a grain size equal to 425-500 µm [24]. Tests were conducted with the same amount of dry sorbent (13.9 g) and similar ratio HT area/dry sorbent mass (S/m = 1.12 ÷ 1.22 m 2 /kg) ...
In this work, plastic adsorbent heat exchangers were developed by a 3D printing technique and experimentally tested aiming at evaluating their potential for adsorption cooling applications.
Various plastic materials were selected and characterized to measure the most interesting physical behaviours both before and after the printing process.
Micro scale plastic flat type heat exchangers were also realized by a 3D printer, integrated with the water sorbent AQSOA FAM Z02 and experimentally tested under real operating conditions typical for adsorption cooling applications to measure the dynamic performance of the new adsorber configurations. To conclude the study, a thermodynamic analysis was carried out by the use of a mathematical model to evaluate the influence of plastic materials on the cooling Coefficient Of Performance.
Results showed that both in terms of thermodynamic and dynamic performance the plastic adsorbers are competitive with metallic ones with a relevant mass reduction and the possibility to manufacture complex geometries by the 3D printing technology. In particular, under the tested operating conditions, the plastic adsorbers were able to deliver a specific cooling power of 1.88-2.40 kW per kg of dry sorbent while the metallic adsorber reached 2.34 kW/kg.
... Die von Keller [57] gemessenen Gleichgewichte dieses direkt aufkristallisierten SAPO-34 unterscheiden sich von den von Núñez gemessenen Gleichgewichten des unter dem Handelsnamen FAMZ02 bzw. AQSOA-Z02 von Mitsubishi Chemicals [58] vertriebenen SAPO-34 [13]. Bei den Messungen von Keller [57] wird deutlich sichtbar, dass der direkt aufkristallisierte SAPO-34 die für die Gleichgewichtsbeschreibung nach Dubinin geforderte Temperaturinvarianz verletzt [13]. ...
... Bei den Messungen von Keller [57] wird deutlich sichtbar, dass der direkt aufkristallisierte SAPO-34 die für die Gleichgewichtsbeschreibung nach Dubinin geforderte Temperaturinvarianz verletzt [13]. Dies zeigt sich auch bei den Messungen von Kakiuchi et al. [58] an FAM-Z02. Die Gleichgewichtsmessungen wurden von Keller an SAPO-34 Pulver durchgeführt, welches als Nebenprodukt der direkten Aufkristallisation von Adsorptionswärmeübertragern anfällt [57]. ...
Der Energieverbrauch von fossilen Energieträgern für das Beheizen von Wohngebäuden und die Warmwasserbereitstellung führt zu CO2-Emissionen, welche den Klimawandel weiter antreiben. Von den jetzt schon spürbaren Auswirkungen, wie beispielsweise der zeitlichen Häufung von Wetterextremen, sind weltweit unzählige Menschen direkt oder indirekt betroffen. Diese Arbeit ist ein technischer Beitrag zur Einsparung von fossilen Energieträgern für die Wärmeversorgung von Gebäuden. Die hier untersuchte Technologie ist die thermisch angetriebene Adsorptionswärmepumpe. Diese kann neben anderen Wärmepumpentechnologien eine sinnvolle Ergänzung zur weit verbreiteten Gas-Brennwerttherme darstellen. Unter Nutzung von praktisch frei verfügbarer Umweltwärme (Luft, oberflächennahe Geothermie) kann eine thermisch angetriebene Wärmepumpe den Primärenergiebedarf für das Heizen um 20-50 % senken. Die Herausforderungen dieser Technologie für die Anwendung in Privathaushalten liegen derzeit in der eher niedrigen Effizienz und der geringen Leistungsdichte, wodurch der zusätzliche Platzbedarf auch für Systeme mit kleiner Leistung (< 10 kW) erheblich ist. Die thermisch angetriebene Adsorptionswärmepumpe basiert auf dem physikalischen Phänomen der Adsorption. Bei der Adsorption wird durch Anlagerung von Molekülen des Arbeitsmittels (Wasser) an eine Feststoffoberfläche Wärme frei. Dieser Prozess kann durch Zufuhr von Wärme umgekehrt werden (Desorption). Nach der Desorption liegt das Arbeitsmittel als Dampf vor und kann unter Freisetzung von Kondensationswärme kondensiert werden. Durch die geeignete Verschaltung der Komponenten (Adsorptionswärmeübertrager, Verdampfer, Kondensator) zu einem Adsorptionsmodul kann die Wärme der Adsorption und die Kondensationswärme für die Wärmeversorgung von Gebäuden genutzt werden. Dabei wird die Umweltwärme über den Verdampfer zugeführt. Die erforderliche Antriebswärme zur Desorption wird bei der thermisch angetriebenen Wärmepumpe durch die Verbrennung eines geeigneten Energieträgers (beispielsweise Erdgas) zugeführt.
In dieser Arbeit werden systematisch verschiedene Varianten von Adsorptionsmodulen betrachtet, die durch Wärmerückgewinnung eine Steigerung der Effizienz ermöglichen. Dafür wird zunächst mit einem stationären Wärmebilanzmodell die maximal erreichbare Effizienz berechnet. Es werden die drei Adsorbentien SAPO-34, Zeolith NaY und Zeolith 13X mit Wasser als Arbeitsmittel untersucht. Die Leistungsdichte hängt vor allem von der Dynamik des Wärme- und Stofftransports im Adsorptionsmodul ab. Die Geometrie des Adsorptionswärmeübertragers als Kernkomponente wird in dieser Arbeit unter Verwendung eines räumlich aufgelösten numerischen Simulationsmodells auf eine möglichst hohe Leistungsdichte hin optimiert. Die hier untersuchte Bauform des Adsorptionswärmeübertragers besteht aus Flachrohren und Faserpaketen aus versinterten Aluminiumfasern. Die wesentlichen Freiheitsgrade der geometrischen Optimierung sind die Schichtdicke des Adsorbens auf der Faseroberfläche, die Dicke des Faserpakets zwischen den Flachrohren, die Porosität des Faserpakets, die Geometrie des Flachrohrs auf Wärmeträgerfluidseite, die Länge des Wärmeübertragers und die hydraulische Verschaltung (parallel, seriell) der Flachrohre im Wärmeübertrager. Bei der geometrischen Optimierung wird auch die hydraulische Verschaltung der angrenzenden Komponenten berücksichtigt, sodass am Ende geometrisch optimierte Varianten des Adsorptionswärmeübertragers für verschiedene Verschaltungen vorliegen.
Die verwendeten numerischen Modelle werden umfassend mit experimentellen Daten validiert, sodass die Ergebnisse der numerischen Simulation auf einem soliden Fundament stehen. Dafür wurden acht verschiedene Proben bestehend aus Trägerblech und Faserpaket mit einer direkten Aufkristallisation des Adsorbens SAPO-34 experimentell charakterisiert. Weitherin werden experimentelle Daten eines Sorptionsmoduls mit einem Adsorptionswärmeübertrager basierend auf direkt aufkristallisierten Faserpaketen zur Validierung herangezogen.
Durch die anschließende numerische Simulation der Adsorptionsmodule im System „Gaswärmepumpe“ wird der Einfluss verschiedener Temperaturrandbedingungen und Leistungsanforderungen des Systems auf Effizienz und Leistungsdichte untersucht. Es konnte gezeigt werden, dass sich mit einer geeigneten Verschaltung und mit Hilfe eines dazu passenden, geometrisch optimierten Adsorptionswärmeübertragers eine saisonale Effizienz von 1.95 erreichen lässt. Die maximale Leistungsdichte liegt bei über 600 W/dm³ bezogen auf den Adsorptionswärmeübertrager, sodass durch den Einsatz eines solchen Adsorptionsmoduls die Entwicklung einer platzsparenden, effizienten Gaswärmepumpe für die Anwendung in Privathaushalten technisch möglich ist.
... In the above simulations, Mitsubishi's adsorbent AQSOA 1 -FAM-Z02 (water uptake of 0.27 g/g at p/ p 0 = 0.15 [32]) and the SAPO-34 zeolite (water uptake of 0.31 g/g at p/p 0 = 0.15 [33]) with water as adsorbate was denoted as one of the best working pair candidates for air conditioning and heat pumping similar in performance to LiBr-silica and CaCl 2 -silica. The COP C , COP H , cooling enthalpy and heating enthalpy of AQSOA 1 -FAM-Z02 and SAPO-34 were similar to LiBr-silica and CaCl 2 -silica (see above) [29 ]. ...
... The disadvantageous large size (volume) of AHT devices was addressed by using zeolite ferroaluminophosphate (FAM-Z01 with a water uptake of 0.18 g/g at p/ p 0 = 0.25 [32]) [34]. FAM-Z01 enabled a reduction of system size with comparable COP C (0.59 for FAM-Z01 and 0.61 for silica gel) and larger specific cooling power (280 for FAM-Z01 and 207 for silica gel) than regular density type silica gel/water (all values at evaporation temperature of 10 C and regeneration temperature of 70 C). ...
Adsorption heat transformation (AHT) is an environmentally friendly energy-saving process applied for air conditioning purposes, that is, either for cooling (including also ice making and refrigeration), or heating. AHT is based on the cycling adsorption and desorption of a working fluid in a porous material. When the working fluid is driven to evaporation by the active empty sorbent material, the required heat of evaporation translates into useful cooling in thermally driven adsorption chillers. Driving heat regenerates the empty sorbent material through desorption of the working fluid. The heat of adsorption in the sorbent material and the heat of condensation of the working fluid can be used in the adsorption heat-pumping mode. Thus, adsorption heat transformation contributes to energy-saving technologies. Adsorbent development plays a critical role for the improvement of AHT technologies. Besides silica gel and zeolites as adsorbent materials, which are up to now used in the commercially available AHT devices; especially metal-organic frameworks (MOFs) are getting more attentions in recent years. Composite materials from salts with silica gels, zeolites and MOFs as well as activated carbons have also been researched to contribute to AHT technologies. Reduction of installation/production cost and enhancement of the efficiency of AHT devices need to be achieved to increase the wider usage of AHT.
... In present study, two kinds of zeolite-based adsorbent are used which are commercially named as AQSOA-Z02 (zeolite-1) [30,28,31,32] and AQSOA-Z05 (zeolite-2) [28,31]. Zeolite-1 has structure type CHA and made of silico aluminophosphate gel with a pore size of 3.8E−10m [31] and crystal density of 1.43 g m L −1 [33]. ...
... Water vapor adsorption isotherms of zeolite-1 and zeolite-2 at 298 K, reproduced from Ref.[30]. ...
Effective thermal conductivity (ETC) of the adsorbent is an important parameter which influences the performance of the adsorption heat pump and adsorption cooling systems. Most of the adsorbents are porous in nature and therefore adsorption uptake is affected due to different operating conditions i.e. temperature and relative humidity (RH) that result in different ETC. Effect of temperature on ETC is somehow well-known in the literature, however, studies on RH effect are limited. Therefore, present study experimentally investigates the RH effect on the thermal conductivity of the commercially available zeolite-based adsorbents which are traded as: AQSOA-Z02 (zeolite-1) and AQSOA-Z05 (zeolite-2). The study is useful for the researcher who are working in the field of adsorption cooling, air-conditioning and desalination. In this regard, an experimental setup was developed by which the ETC was measured at different levels of RH. According to the results, the ETC of oven dried zeolite-1 and zeolite-2 was 0.060 W m⁻¹ K⁻¹ and 0.066 W m⁻¹ K⁻¹, respectively. With the increase in RH, the value of ETC increases up to 0.090 W m⁻¹ K⁻¹ for zeolite-1 and 0.089 W m⁻¹ K⁻¹ for zeolite-2. Moreover, an empirical relation is proposed which can estimate ETC at different levels of RH for both adsorbents.
... A disadvantage of micro-/meso-porous silica gels is their low water uptake capacity compared to some other sorbents, such as metal-organic frameworks (MOFs, [18]) and aluminophosphates [19]. One approach to improve their uptake is to use silica gel as a host matrix for hygroscopic salts, such as CaCl 2 or LiCl [2]. ...
... 11 Of these, the S-shaped or stepped isotherm with little or no hysteresis is the most desirable as it enables both high working capacity ( Figure 1B) and low regeneration energy. 12 However, such an isotherm shape is relatively rare in traditional inorganic sorbents [13][14][15] and is often associated with capillary condensation in mesopores at high RH. 16,17 Metal-organic materials, 18 including metal-organic frameworks (MOFs) 19,20 or porous coordination polymers, 21 offer tunable pore shape and pore chemistry thanks to their modular nature and amenability to crystal engineering. ...
... Two AIPO-type adsorbents have been tested under over 100,000 cycles to demonstrate their suitable durability for practical use [132,133]. Among them, FAM-Z01 with 0.73 nm windows can obtain 0.2 g g − 1 of water uptake with adsorption/desorption at 30 • C and 75 • C, while FAM-Z02 with a small pore size of 0.38 nm can absorb a larger amount of water (0.3 g g − 1 ) but need to be regenerated at 90 • C. FAM-Z05 developed by Shimooka et al. [134] is able to adsorb water vapor at an ultra-low temperature of 50 • C. Recently, Liu et al. [123] studied an AlPO-type adsorbent with SFO topology, namely EMM-8, for water adsorption refrigeration. ...
Adsorption thermal storage, which can store heat like a battery, reserve it when it is unneeded and release thermal energy on users’ demands, has been acknowledged as a promising strategy for heat reallocation, especially water based adsorption thermal battery (ATB). This review aims to summarize the recent advances in this domain and provide perspectives for the further development of ATB, focusing on the design of adsorbent materials and the optimization of system configurations in the light of different application scenarios. Here, we start with introducing the fundamental mechanisms concerning thermodynamics and adsorption kinetics. Next, we elaborate properties and performances of various adsorbents and system configurations developed for ATB, with their advantages and limitations as well as design strategies discussed. Importantly, we introduce the application-oriented selection principles of diversified materials and system cycles, which could provide practical guidelines for overall design in various application scenarios. In the last section, we outline the challenges in this field from fundamental research and practical application aspects, and provide a future outlook for the development of ATB technology.
... It is quite reasonable to explain this tendency by decreasing capillary force as the micropore diameter increases [101]. A comparison of different works on SAPO-34 synthesis and water adsorption testing reveals consistency in the obtained capacities with slight deviations, which could be attributed to the different evaluation methods used i.e. volumetric or gravimetric, though both methods displayed the same isotherm shape [99,[102][103][104]. ...
Freshwater resources are being heavily depleted and not replenished at the same high rate, thus, atmospheric water vapor harvesting has earned growing interest. Development of high-performing desiccant or adsorbent materials offering high sorption capacity and selectivity as well as regeneration capability in atmospheric conditions is crucial to tackle water scarcity. The required properties to generate potent water sorbents include pore accessibility, high specific surface area and porosity to enable high capture capacity and kinetics, and hydrothermal resilience to resist cyclic sorption and desorption. Further, polarity, hydrogen bonding, adhesion ability of water molecules to adsorbent surface, and hydrophilic functional groups can boost water adsorption. A highly promising class of water vapor adsorbents is the aluminophosphate molecular sieves (AlPOs), which are microporous zeotype materials. In this review, AlPO-based adsorbents are discussed for water sorption applications and a link is established between performance of materials and their chemical and morphological properties. Synthesis-properties-performance relationships are elucidated in light of synthesis techniques and adsorption behavior, and prospects to enhance AlPOs' water vapor sorption performance toward large-scale water harvesting applications are highlighted.
... ,78,80 On a commercial level, two innovative adsorbent materials were developed by Mitsubishi Plastic Inc. named AQSOA Ò -FAM-Z02 and AQSOA Ò -FAM-Z01.80,81 Both materials have desorption temperatures of 60°C-90°C and seem like a reliable alternative for various applications such as heating. ...
Adsorption heat pumps (AHPs) have gained noticeable attention in recent years. The review discusses significant research in the domain of adsorption heat pumps focusing on heating applications, the working principle, adsorption equilibrium and kinetics, the design of adsorbent beds, physical models, operating parameters, and physical and thermodynamic characteristics of adsorbents. A comparison is presented among AHPs and traditional heating technologies and systems for AHPs that certain market participants have created. The review focuses on the most appropriate conditions for each measurement technique and the constraints of the modeling processes that are an essential element for the comprehensive performance evaluation of adsorption cooling units. For adsorption bed applications, it is suggested to use various bed designs and heat exchanger structures. Moreover, significant literature gaps and constraints in designing AHPs for heating applications are identified and analyzed. The heat and mass transfer resistance should be reduced by developing novel adsorbent materials and an improved interface among the duct wall and the bed, where heat transfer fluid circulates to increase adsorption heat pump system performance. Furthermore, optimum operational modes for the intended application might significantly enhance system performance.
... practical applications. [17][18][19][20][21][22][23] However, these adsorbents have obvious drawbacks in balancing the adsorption capacity and desorption conditions because of too weak or too strong hydrophilicity. [21] Therefore, it is necessary to develop novel porous functional materials with efficient water capture and release performance from atmosphere. ...
Water adsorption based on porous materials is of fundamental importance in atmospheric water harvesting and dehumidification. Herein, a [BOHmim][Zn2Cl5]@MIL‐101(Cr) composite with multiple adsorption sites is designed to enhance the water adsorption capacity. It is interesting to observe that there is a water‐responsive confinement–unconfinement transformation of ionic liquids (ILs) during the water adsorption and release process. Thus, it can simultaneously overcome the limitation of pore volume in traditional porous materials, and the problem of mass transfer in pure ILs. As a result, the obtained IL@MOF composite achieves a high water adsorption capacity (477 wt%) at 298 K and RH = 95%, which can be released under relatively mild operating conditions (313 K, RH = 40%). This work provides a general way to develop adsorbents for the capture of molecules with high polarity and low dew‐point in combination with the advantages of ILs and metal–organic frameworks (MOFs). An IL@MOF composite with multiple adsorption sites is designed and synthesized using [BOHmim][Zn2Cl5] and MIL‐101(Cr) to capture and release water. The composite exhibits a high water adsorption capacity (477 wt%). It can be released at a relatively mild condition, and a water‐responsive confinement–unconfinement transformation of ionic liquids (ILs) occurs during the capture and release process of water.
... In this work, a dynamic comparison of PI and TI cycles was made for a much more complex and realistic bed configuration that was a finnedtube heat exchanger (HEx) filled with loose grains of another commercial adsorbent, aluminophosphate AQSOA-FAM-Z02 or SAPO-34 [17] (referred to below as FAM-Z02). The adsorptive studied (water vapour) was also different from that in [16] (methanol). ...
Adsorption heat transformation is an environmentally friendly and effective method of using low-temperature heat from renewable, industrial and domestic sources. The transformation can be initiated by changing either adsorptive pressure (pressure-initiated, PI) or adsorbent temperature (temperature-initiated, TI). This work aims to elucidate how the initiation pathway affects the dynamics of water adsorption for silicoaluminophosphate AQSOA-FAM-Z02 loaded inside a commercial finned flat-tube heat exchanger. The main findings of this study are as follows: (a) all kinetic curves can be represented as a superposition of fast and slow exponentials associated with the process rate limitation by vapour transfer or heat transfer, respectively; (b) at a short time (<150–200 s), the PI adsorption is faster than the TI one by a factor of 3; (c) at a long time (>100–150 s), the PI desorption is slower than the TI one. From the practical point of view, the revealed differences between the PI and TI dynamics could allow the specific power of adsorption heat transformers to be improved through a better organization of the working cycle.
... The transport properties of adsorbent bed can be accelerated utilizing fins, and/or metal additives [16][17][18][19][20] or coated bed designs [21][22]. The example of new adsorbents can be given as SWS-1L [23], FAM Z01 and Z02 [24,25], AQSOA-Z05 [26], metal-organic frameworks (MOFs) [27], and Maxsorb III [28]. Although the new adsorbent can enhance the adsorption chiller performance, the endurance of new adsorbents under vacuum conditions and thermal treatment during cycles should be well researched. ...
The main objective of this study is to design a low-grade heat driven ethanol-silica gel adsorption chiller. The low-grade waste heat is utilized in an adsorption chiller. For this purpose, an innovative bed heat exchanger including a condenser embedded inside the adsorbent bed is uniquely designed. The silica gel/ethanol pair is examined both analytically and numerically in this article. The cycles of the adsorption chiller are performed experimentally. The obtained isotherm for the silica gel/ethanol fitted to Type III isotherm behavior. The obtained equations of isotherm are also validated numerically. The new adsorption chiller design used in this study has reduced the desorption temperature for silica gel/ethanol pair to 37°C which will widen the application area of adsorption chillers. The COMSOL Multiphysics program is used for 2-D numerical analysis of adsorbent bed. The mass transfer inside of the particle, the heat transfer in porous media, and Darcy law are used for analyzing the heat and mass transfer of the bed. Temperature and concentration distributions of adsorbent bed during the duration of adsorption and desorption processes are examined numerically. The specific cooling power and volumetric cooling power values of the system are found as 20.2 Wkg-1 and 4.5 kWm-3, respectively.
... The characteristic time τ 0.8 allows the specific power generated at 80% conversion W 0.8 = 0.8•ΔH•Δw/τ 0.8 to be estimated, where ΔH = 3240 J/g is the heat of water adsorption on FAM-Z02 [27], Δw = w 2 -w 1 = 0.12 ± 0.01 g/g is the mass of water adsorbed (the relative error δ = 10%). The W 0.8 -value drops down from 1.2 ± 0.2 kW/kg at ΔP air = 0 mbar to 0.1 ± 0.1 kW/kg at ΔP air = 5 mbar (Fig. 5). ...
It is well known that non-adsorbable gas, e.g. residual air, can dramatically slow down the adsorption stage of adsorption heat transformation cycles. So far, this effect has been studied for the cycles initiated by temperature change (temperature-initiated cycles). This work addresses the dynamic effect of residual air for another way of adsorption initiation, namely, by changing vapour pressure over adsorbent (pressure-initiated cycle). Comparison of the pressure- and temperature-initiated cycles is also made. The effects are studied for the working pairs “AQSOA FAM-Z02 – water” and “LiCl/(silica gel) – methanol” promising for adsorption heat transformation. The residual partial air pressure ΔPair was varied from 0 to 5 mbar.
The main finding of this study is that the pressure-initiated adsorption is less sensitive to the presence of residual air than the temperature-initiated adsorption. This is especially true at a low partial air pressure ΔPair. For instance, at ΔPair ≤ 0.5 mbar, residual air has little or no effect on the pressure-initiated adsorption dynamics compared to the temperature-initiated one. A qualitative explanation of this finding is proposed. Thereby, closed adsorption heat transformation cycles based on the pressure-initiated process are more robust and resistant against the presence of residual air that could be a significant practical advantage.
... Adsorbents adapted/developed for AHCS in the first decade of the 21st century (coals [5,12], composites "salt in a porous matrix" (CSPM) [6,13], aluminophosphates [14,15]) were lately gradually improved to fit particular AHCS cycles. For aluminophosphates, the main direction of improvement is increasing hydrothermal stability and reducing cost. ...
The phenomenon of adsorption known since ancient times is now widely used to convert low-temperature heat. This short review addresses recent results and current tendencies in adsorption heat conversion/storage in closed systems, which are the most important according to the author's opinion. The survey is based on literature data, reported mainly in the second decade of this century, and concerns the development of new adsorbents and cycles, improvement of adsorption dynamics, and some other topical issues. The paper aims at highlighting the current progress, research trends and existing gaps of the technology involved.
... As a consequence, a high temperature T H is required for its regeneration. It is clear from these considerations that among adsorbents of water zeolites and aluminophosphates [19,20] could ensure larger temperature lifts, ...
This paper addresses some thermodynamic aspects of adsorptive heat transformation (AHT) driven by ultralow-temperature (ULT) heat. This non-payable heat is available in abundance from various natural thermal sources and as heat wastes from industry, transport and power engineering. The link between the temperature thrush that drives an AHT cycle and the obtained temperature lift is analyzed using the Troutun rule.
It is shown that even if only ULT heat with T ≤ 50 oC is available, it can effectively drive adsorptive cooling cycles and obtain an output temperature sufficient for air-conditioning, ice-making, and freezing. Moreover, heat amplification cycles can be driven by ULT heat with a temperature lower than 20oC. The Dubinin adsorption potential ΔF is proposed as a quantitative measure of the adsorbent affinity, and the quantitative relationship between the temperature thrush and this potential is found for water as an adsorptive. This link can greatly help in choosing adsorbents optimal for the given AHT conditions.
... Jänchen et al. [19] reported sorption capacities of 0.24 kgH 2 O kg − 1 and 0.19 kgH 2 O kg − 1 for Li-X and Na-X, respectively, while zeolite 4A showed a water sorption capacity of 0.22 kgH 2 O kg − 1 [24]. Furthermore, the water sorption and heat storage capacities of different classes of materials such as aluminophosphates (AlPOs) and silicoaluminophosphates (SAPOs) have also been investigated [20,25]. The good thermal stability over successive hydration/dehydration cycles of these materials represents the main advantage for their use as component in thermochemical heat storage systems [26]. ...
Composite materials based on aluminium fumarate (AF) and CaCl2 have been developed for the storage of energy from renewable and waste sources. Composite Salt-Porous Matrix (CSPM) was synthesized by impregnating aluminium fumarate MOF host matrix with various relative CaCl2 salt contents (25–60 wt%). The resulting CSPMs were fully characterized by X-ray diffraction, N2 and H2O sorption isotherms at −196 and 25 °C, respectively, scanning electron microscopy and thermal analysis. The high surface area of the AF matrix (959 m² g⁻¹) drastically decreases upon the addition of salt, to about 50 m² g⁻¹. The heat storage performance of the composites was found to depend on the added amount of salt to the MOF matrix, with higher amounts of salt leading to better performance. The maximum water sorption capacity of 0.68 kgH2O kg⁻¹, coupled with a high heat of water sorption (1840 kJ kg⁻¹), makes these composites interesting when used at a rehydration level not exceeding CaCl2.4H2O to avoid any deliquescence and washing out of the salt. A kinetic study of the hydration demonstrated that salt deposition increases the water sorption rate in comparison with the host matrix. Moreover, the impact of salt deposition on the activation energy of dehydration of the host matrix was also determined by applying integral isoconversional methods.
... Furthermore, the phenomenon of hysteresis is undesired for the adsorption process as this will cause a loss of inefficiency. Many researchers have used silica gel [37,38], zeolite [39,40], and functional adsorbent material such as FAM Z05 [41], Z01 [42], Z02 [43], and [44] for different applications. All these adsorbents show good adsorption characteristics, especially silica gel and zeolites. ...
The reduction of carbon dioxide emissions has become a need of the day to overcome different environmental issues and challenges. The use of alternative and renewable-based technologies is one of the options to achieve the target of sustainable development through the reduction of these harmful emissions. Among different technologies thermally activated cooling systems are one which can reduce the harmful emissions caused by conventional heating, ventilation, and air conditioning technology. Thermal cooling systems utilize different porous materials and work on a reversible adsorption/desorption cycle. Different advancements have been made for this technology but still a lot of work should be done to replace conventional systems with this newly developed technology. High adsorption capacity and lower input heat are two major requirements for efficient thermally driven cooling technologies. In this regard, it is a need of the day to develop novel adsorbents with high sorption capacity and low regeneration temperature. Due to tunable topologies and a highly porous nature, the hybrid porous crystalline materials known as metal–organic frameworks (MOFs) are a great inspiration for thermally driven adsorption-based cooling applications. Keeping all the above-mentioned aspects in mind, this paper presents a comprehensive overview of the potential use of MOFs as adsorbent material for adsorption and desiccant cooling technologies. A detailed overview of MOFs, their structure, and their stability are presented. This review will be helpful for the research community to have updated research progress in MOFs and their potential use for adsorption-based cooling systems.
... Cp,s (J kg −1 K −1 ) 1000 [32] 892 (a) [33] s (kg m −3 ) 2600 [34] 2260 [35] Ds0 (m 2 s −1 ) × 4.9 10 9 ...
The performance of the metal-organic framework (MOF) CPO-27(Ni) for adsorption heat pumps using water as adsorbate was investigated through modeling and Computational Fluid Dynamics (CFD) simulations. A customized solver and methodology to simulate adsorption cycles were developed in OpenFOAM and strictly validated using literature data, since OpenFoam lacks specific tools for these processes and applications.
Due to the potential of adsorbent coatings and metal fibers and foams for improving the performance of such processes, a metal tube of copper surrounded by a composite of copper foam and CPO-27(Ni) coating, was considered in this study.
For evaporation, condensation and bed regeneration temperatures of 278.15 K, 308.15 K and 368.15 K, respectively, the obtained coefficients of performance and specific heating powers for the composite coating CPO-27(Ni)/copper foam were in the range 1.16-1.39 and 1922-5130 W kg⁻¹. Under similar conditions, the MOF was outperformed by the well-known adsorbent AQSOATM FAM-Z02, essentially due to the faster intraparticle mass transfer kinetics for the latter.
... Among the large variety of traditional and innovative materials suggested for AHS are zeolites [10e12], pure and substituted aluminophosphates [12,13], metal-organic frameworks (MOFs) [14e16], and Composite sorbents "Salt in Porous Matrix" (CSPMs) [17]). CSPMs are considered promising for AHS because they are characterized by a large HSC of 0.7e4.0 ...
Adsorption heat storage (AHS) is an energy-saving technology that allows low-temperature heat from renewable energy sources and various wastes to be utilized. One of the most important ways to increase the efficiency of the AHS units is to develop adsorbents with high heat storage density. This work addresses the methanol sorption on an innovative composite based on expanded vermiculite impregnated with LiCl (LiCl/Verm), which is suggested for adsorptive cycles for seasonal heat storage. Such a cycle is typical of regions with moderately cold winter, like the South of the Russian Federation as well as the Northern part of China, Europe etc. The study consists of: (1) synthesis and characterization of the composite; (2) investigation of equilibrium and dynamics of methanol sorption under operating conditions of the seasonal AHS cycle; (3) evaluation of the sorbent heat storage capacity and specific power. The heat storage capacity of LiCl/Verm under conditions of the tested cycle reaches 1.5 kJ/g. This value far exceeds that for conventional and innovative adsorbents. The specific power of 0.9 and 1.5 kW/kg can be realized during discharging and charging stages of the cycle, respectively. These findings demonstrate a high potential of the LiCl/Verm composite as methanol sorbent for AHS.
... Among the several possible adsorbent materials, the zeolite SAPO-34 is particularly promising for heat transformation applications because of its S-shaped water adsorption isotherm, its ability to be regenerated by low-grade heat below 100°C, and its hydrothermal stability. 25 Several research groups have exploited SAPO-34 in heat adsorption applications. In one example, adsorbent HEXs were prepared by dip coating in an aqueous slurry of SAPO-34 particles and bentonite clay as a binder. ...
Adsorption heat pumps offer a clean, zero-emission technology for universally applicable cooling or heating utilizing water as refrigerant and waste or renewable heat as driving energy instead of electricity. Despite their attractive environmental-friendly prospects, the broader application of such class of heat pumps has not yet been possible mainly due to the low power density of adsorption heat exchangers and the corresponding large size and high cost of the adsorption heat pumps. We report an inexpensive route for the fabrication of zeolite coatings with high adsorption power density based on the bottom-up assembly of colloids directed by magnetic and capillary forces. Such assembly process relies on the chaining of oil droplets under an external magnetic field during deposition of the coating, followed by the formation of a percolating network of bridged adsorbent particles upon drying. This results in vertical open channels and thermal bridges that facilitate directed mass and heat transport across the structured zeolite coating during sorption cycles. By reaching up to 3.3-fold higher performance than their unstructured counterparts using readily available zeolite as adsorbent material, the architectured coatings produced through this facile, up-scalable approach hold great potential for next-generation adsorption heat pumps.
... These materials have S-shaped isotherms meaning that they have a high water exchange capacity for low temperature differences [18,21,22]. Recently, Mitsubishi Plastic Inc. developed and commercialized new adsorbent materials, AQSOA ® -FAM-Z01 and AQSOA ® -FAM-Z02 [23,24]. Both materials work with desorption temperatures in the range of 60-90 0 C and seem to be a promising solution for heating applications. ...
A review of the most relevant work on the field of adsorption heat pumps with emphasis on heating applications is presented, covering the working principle, physical models, adsorption equilibrium and kinetics, adsorbent material physical and thermodynamic properties, adsorbent bed designing and operating conditions. The major literature gaps and development challenges of adsorption heat pumps for heating applications are identified and discussed. A bridge between materials and system level studies is lacking. The simultaneous investigation of the adsorption kinetics, adsorbent bed specifications, operating conditions and interaction between all the system components is missing in the literature. Detailed information required for the development and validation of physical models is often not provided in the experimental studies. A physical model that considers an entire adsorption heat pump system, which is required for performance predictions and system's optimization, cannot be found in the literature. To improve the adsorption heat pump system's performance the heat and mass transfer resistances need to be minimized by developing new adsorbent materials and better interaction between the adsorbent bed and the wall of the duct where the heat transfer fluid flows. In addition, operation modes optimized for the desired application can also contribute to improving the system's performance.
... In other words, adsorption materials dominantly 1 3 determine the system performance. A new material of adsorbent, a kind of zeolite, that can be regenerated at relatively low temperature was developed (Mitsubishi Chemical Holdings Corporation 2011) and Kakiuchi et al. (2005) showed the zeolite adsorbent can intake larger amount of water than silica-gel does. Another approach to enhance the adsorption process is charging external impact on the adsorbents. ...
In this study the enhancement effect of adsorption mass transfer by acoustic wave is investigated to understand how the acoustic wave influences the adsorption performance. The experimental data were obtained to show the behavior of silica-gel adsorption with/without acoustic field. The experimental results showed the adsorption speed with acoustic wave became higher than that without acoustic wave although the equilibrium adsorption amount was kept to be the same. From the viewpoint of acoustic wave conditions, the adsorption speed was increased with increasing the velocity amplitude, while the pressure amplitude had no effect on the enhancement. The maximum adsorption speed attained five times as high as the case without acoustic wave when the velocity amplitude was 1.35 m/s. Background air flow velocity is also an influential factor. The experimental results support that the non-dimensional ratio of the velocity amplitude to the background flow velocity is essential to describe the enhancement effect. Based on the observed data, an empirical formula was estimated to express the relationship between the enhancement effect and the non-dimensional velocity amplitude. The liner regression showed the good agreement and gave the critical non-dimensional velocity amplitude of 1.9 over which acoustic wave is effective to amplify the mass transfer rate of adsorption.
... One of the most important challenges is the development of new sorption materials with enhanced heat storage capacity, specialized for SHS. To date, several common and innovative adsorbents have been proposed for SHS: silica gels [12], zeolites [16][17][18], AlPOs and SAPOs [15,18,19], metal-organic frameworks MOFs [20][21][22], Composites "Salt in Porous Matrix" (CSPMs) [23][24][25][26][27][28], etc. New water sorbent on the base of lithium chloride and Multi-Wall Carbon Nano-Tubes (LiCl/MWCNT) has recently been proposed for a daily heat storage cycle [29]. ...
Sorption heat storage (SHS) is a promising technology towards efficient use of renewable energy sources. Composite materials based on hygroscopic salts have a high potential for SHS in term of the heat storage capacity. Recently, a new sorbent “LiCl confined to Multi-Wall Carbon NanoTubes (MWCNT)” with enhanced storage capacity (1.7 kJ/g) has been suggested for SHS. This work addresses the dynamic study of water sorption on this material under operating conditions of a daily heat storage cycle. The study consists of three parts: (1) shaping the LiCl/MWCNT composite as grains (GP) and pellets with (PB) and without a binder (PP); (2) water sorption dynamics under conditions of the selected SHS cycle; (3) evaluation of the specific power achievable. Various configurations of the adsorbent bed were tested, namely, the loose grains GP placed on a metal support, and the pellets PB and PP glued to the support. The dynamic curves of water sorption obey an exponential equation. The PB configuration ensured a maximal specific power of 11.2 kW/kg (at 70% conversion) during the heat storage stage. During the heat release stage, the specific power is lower (5.4 kW/kg), probably due to a kinetic hindrance attributed to solid-solid transformation during the decomposition of LiCl·H2O complex towards the anhydrous salt. The high specific power along with the large heat storage capacity make the LiCl/MWCNT composite a promising new candidate for SHS.
... Quite interesting storage parameters were obtained for new zeolite-like materials that do not contain silicon, namely, pure and substituted aluminophosphates [56][57][58][59]. E.g. an APO-Tric material was suggested for use in low temperature solar energy storage [56], because it exchanges 0.25 g H 2 O/g in an extremely narrow range of the relative pressure P/P o = 0.12-0.15 ...
... In the family of the zeolite, the SAPO-34 seems to possess some attractive features that help to improve the adsorption refrigeration performance [13]. The equilibrium sorption rate of SAPO-34 zeolite can reach 0.35 g w /g a as water as the refrigerant [14]. ...
The dynamic characteristics of SAPO-34 and ZSM-5 zeolite in the desorption process have been experimentally studied with the gravimetric method. The weight change of the test sample was recorded continually for different conditions of temperature and pressure. The curve of the desorption degree with the temperature and the pressure was obtained and discussed. With the intrinsic different micro-structure, the two zeolites showed distinguished characteristics of the desorption. In contrast to an S-shaped desorption curve of the SAPO-34, the ZSM-5 showed an exponential desorption curve. In comparison, the desorption characteristics of the ZSM-5 were better than that of the SAPO-34 in the temperature range of 40 °C ~ 90 °C. Nevertheless, the effect of the pressure on the desorption degree was stronger for the SAPO-34 than for the ZSM-5. Further analysis revealed that the desorption speed was affected more strongly by the temperature than by the pressure.
... The Sorption Heat Storage (SHS) consists of two main phases, namely charging or heat storing phase during endothermic desorption, and discharging or heat releasing phase during exothermic adsorption. A large number of sorbents are currently considered for SHS, both traditional (silica gels [9,13], zeolites [14,15], etc) and innovative (AlPOs and SAPOs [16,17], metal-organic frameworks MOFs [18][19][20], and Composites ''Salt in Porous Matrix" (CSPMs) [21][22][23]). The main drawback of silica gels is relatively small HSC obtained in real systems (down to 50 kW h/m 3 kg) and low temperature lift at discharging stage [9]. ...
Sorption heat storage (SHS) is a promising technology towards efficient use of renewable energy sources. Materials based on hygroscopic salts and their hydrates have a high potential for SHS in term of heat storage capacity. This work addresses the study of the novel composite water sorbent based on expanded vermiculite impregnated with LiCl, specified for two particular SHS cycles, namely seasonal and daily heat storage in winter. The paper consists of two parts: (i) preparation of the LiCl/vermiculite composite and study of its texture, phase composition, as well as equilibrium and dynamics of water sorption; and (ii) evaluation of the potential of the new sorbent for the selected SHS cycles. The results obtained show that the salt, dispersed inside the vermiculite pores, reacts with water molecules, forming the crystalline hydrates LiCl⋅nH2O (n = 1, 2). The heat storage capacity of the LiCl/vermiculite reaches 2.3 (224 kWh/m³) and 2.6 kJ/g (253 kWh/m³) for seasonal and daily SHS cycles at the charging temperature 75-85 °C, that exceeds the appropriate values for common and innovative adsorbents suggested for SHS. This demonstrates the high potential of the new composite for SHS and promotes the broader implementation of this emerging technology.
This is the 9th Heat Powered Cycles Conference. The first edition of the conference was held at Nottingham in 1997. This time the event was co-organized by the University of the Basque Country, (Bilbao, Spain), The University of Applied Sciences, Vorarlberg, (Austria), and GamaTech Thermal Solutions, (Brazil). The conference took place at the University of the Basque Country and hosted by the Department of Energy Engineering at the University of the Basque Country by Prof. Jesús María Blanco Ilzarbe. In addition to formal presentations of technical papers, including invited Keynote papers, the event includes poster sessions and two Special Sessions, being one related to Intelligent Thermal Energy Systems and The Energy in the Post-Covid Scenario, along with a full social program. The conference is concerned with scientific and technological innovations relating to the efficient and economic use of heat, derived from all its sources, for the production of cooling, heating, and mechanical power either independently or co-generatively.
Subject areas of particular interest include; hybrid cycles, ORCs, Stirling cycle machines,
thermo-acoustic engines and coolers, sorption cycle refrigerators and heat pumps, jet-pump (ejector) machines, temperature amplifiers (heat transformers), chemical heat pumps, new working fluids, mass and heat transfer phenomena, desalination of brackish water and seawater, compact heat exchanger research (including foams and other micro-channel research), thermo-economics, process optimisation and modelling, process, and cycle thermodynamics.
This is the 9th Heat Powered Cycles Conference. The first edition of the conference was held at Nottingham in 1997. This time the event was co-organized by the University of the Basque Country, (Bilbao, Spain), The University of Applied Sciences, Vorarlberg, (Austria), and GamaTech Thermal Solutions, (Brazil). The conference took place at the University of the Basque Country and hosted by the Department of Energy Engineering at the University of the Basque Country by Prof. Jesús María Blanco Ilzarbe. In addition to formal presentations of technical papers, including invited Keynote papers, the event includes poster sessions and two Special Sessions, being one related to Intelligent Thermal Energy Systems and The Energy in the Post-Covid Scenario, along with a full social program. The conference is concerned with scientific and technological innovations relating to the efficient and economic use of heat, derived from all its sources, for the production of cooling, heating, and mechanical power either independently or co-generatively.
This study investigates the performance of double effect adsorption refrigeration cycle that utilizes the adsorption heat of a high-temperature adsorbent heat exchanger for desorption of a low-temperature one. Because there is a freedom to select an adsorbent for each adsorbent heat exchanger, the combination of adsorbents such as silica gel, FAM-Z01, FAM-Z02 and FAM-Z05 were examined. The temperature of an external heat source was assumed to be 90°C. Dynamic cycle simulation was employed to estimate the performance in terms of coefficient of performance (COP) and specific cooling power (SCP). The results show that the combination of the adsorbents FAM-Z01 and FAM-Z02 for the low-temperature heat exchanger and high-temperature one, respectively, is the most effective to achieve high COP as well as high SCP. The results also indicate that the COP=1.0 is attainable when the mass allocation of the adsorbents and the cycle time are selected appropriately. From the viewpoint of maximizing the cooling power, COP=0.9 is suggested for the best design, where the mass of high-temperature side is equal to the mass of low-temperature side.
Thermochemical heat storage is currently regarded as the most promising technology with capability of the systems to conserve the thermal energy as long as desired without heat losses due to their reversible sorption and chemical reactions. Design of efficient storage sorption materials with advanced properties is motivated by two driving forces: to increase of the energy storage density and to regenerate the sorbent at low temperature (80–140°C). Since the beginning, highly hydrophilic zeolites and weak hydrophilic silica gels with water vapor systems have been one of the most studied and tested adsorbent/adsorbate pairs for application in thermo‐chemical heat storage. However, zeolites require high temperature for desorption (>200°C), while silica gels need lower desorption temperatures (~100°C), and both adsorbents have a low water loading within a adsorption/desorption cycle. Thus, an optimal sorption material should provide a moderate affinity toward water molecules that depends on particular operating conditions of the cycle. This chapter reviews sorption material developments on zeolites, aluminophosphates, metal organic frameworks (MOFs) and two‐component sorbents (composites) containing porous matrices from zeolites to new mesostructured iron silicate and salt hydrates with high energy storage density. The developments in materials research promise novel and high performance storage materials in near future.
Owing to their high porosity, high water sorption capacity, and thermal stability, aluminophosphate(AlPO) zeolites have shown promising applications in adsorption heat pump(AHP) systems to utilize low-temperature waste heat from heat sources. To accelerate the development of new high-efficiency AHP adsorbents, we report a high-throughput grand canonical Monte Carlo(GCMC) approach to predict the heat storage capabilities of 78 known and 84292 hypothetical AlPO zeolites. We employ three evaluation metrics, including water working capacity, energy density, and regenerability, to comprehensively evaluate the performance of these AlPO structures. Finally, we identify 29 promising candidates with water adsorption properties superior to the commercial adsorbent AQSOA-Z02. This is the first study in large-scale screening of AlPO zeolites for water adsorption. The obtained results will provide important guidance toward the experimental discovery of high-performance AlPO zeolites for AHP applications.
This study focuses on the adsorption heat pump cooling performance enhancement. The corrugated heat exchanger (HEX) has been employed in recent years owing to its excellent heat transfer; however, its filling method require improvement. Therefore, a filling method called dip-coating method is introduced to improve its heat transfer and packing density. The dip-coating method is adapted to accommodate the Wakkanai siliceous shale composite adsorbent, and two types of adsorbent filled-HEX (ad-HEX), i.e., the dip-HEX and dip-filled-HEX, are compared with the conventional ad-HEX of the filled-HEX. The dip-HEX comprises a few mass transfer channels and has a packing density similar to that of the filled-HEX. Meanwhile, the dip-filled-HEX exhibits a 30% higher packing density compared with the filled-HEX. A basic performance experiment is performed, and the results indicate that the dip-HEX outperforms the filled-HEX owing to its higher coefficient of performance (COP) and specific cooling power (SCP). The dip-filled-HEX exhibits a slightly lower SCP than the filled-HEX; however, it exhibits the highest COP among three types of ad-HEXs. Subsequently, mass recovery is applied to enhance the cooling performance. In a typical mass recovery period of 10 s, the COP and SCP of the dip-HEX increases to 0.46 and 0.74 W/g, respectively.
Cyclic physical adsorption and desorption processes on porous materials can be used for the conversion of heat in heat transformation processes, which is the working principle in adsorption heat pumps (AHPs). Environmentally benign water with its high enthalpy of evaporation is the working fluid of choice in AHPs. Metal‐organic frameworks, MOFs can adsorb large amounts of water or methanol, up to their own weight. MOFs could be alternative materials to silica gels, zeolites, or aluminum phosphates for low‐temperature heat transformations in AHPs.
In this work, the study of a novel solar driven Combined Cooling, Heating and Power (CCHP) system is carried out. In particular, the system is composed of a 60 m2 flat plate solar thermal collectors field, a 10 kWe photovoltaic plant, a 2 m3 Thermal Energy Storage (TES), a 3 kWe micro-Organic Rankine Cycle (micro-ORC) prototype, a 4.4 kWc thermally driven Adsorption Chiller (AC) coupled with a 6 kWc auxiliary Heat Pump (HP). It has been conceived for residential applications and has been integrated with a real bioclimatic nearly zero energy building (NZEB). The building-plant system has been modelled in TRNSYS environment and studied for three Italian locations, spread along the peninsula, with three different climates, Messina, Milano and Rome. An energy, environmental and economic analysis have been carried out. The system has been assessed on hourly basis and the sensitivity analysis has demonstrated that performances are sensitive to location. In particular, the effectiveness of the system is greatly affected by solar radiation and weather condition. The CCHP system works for about 2400 h during the whole year on average with global efficiencies ranging from 32% to 42%. The plant is generally suitable for air conditioning applications in residential sector only with a government's financial support. A medium value of Pay Back Time of 6 years has been found with a medium Net Present Value of 50 kEUR. In conclusion, this study has highlighted the potential of solar driven micro-CCHP systems based on advances technologies for residential applications.
This study aims to develop a low-cost and highly efficient adsorption chiller (AHP). A laboratory-scale AHP with a capacity of 1 kW and transparent body was developed to observe the valve's operation and condensed water. A natural mesoporous material, WSS impregnated with 20 wt % LiCl was used as an adsorbent to reduce the initial cost and filled into aluminum corrugated heat exchangers (HEX). Foundation performance experiments were conducted, and the COP of 0.45 and SCP of 0.41 kW/kg were obtained under the following experimental conditions: regeneration at 80 °C, condensation, and sorption at 30 °C, chilled water of 15 °C, and cycle time of 14 min. Further, heat recovery was introduced and experimentally studied to reduce the regeneration heat amount, and the heat balance for this AHP was evaluated. It was confirmed that two types of heat recoveries could improve the COP for this AHP up to 0.54 when the outlet temperature of both adsorbers was 55 °C. The COP could be further improved to 0.57, based on the calculation for the heat balance. This AHP has advantages of high SCP as compared with AHPs in other formal studies, although some details need to be studied in the future.
The composite adsorbent of natural mesoporous powder of Wakkanai siliceous shale (WSS) impregnated with LiCl has been investigated. In this study, the slurry of WSS–LiCl with acryl resin as a binder was prepared for fabricating an adsorbent-filled heat exchanger (HEX). The optimal LiCl content for the impregnation with WSS was 20 wt%, which was chosen from the relation between water uptake and pore volume. The theoretical sorption amounts were estimated from various sorption isotherms, and the value was 0.34 g/g at the temperature conditions of 80 °C (regeneration), 30 °C (condensation and adsorption), and 15 °C (evaporation). From the analysis of sorption heat, it was found that water adsorption and desorption occurred repeatedly at the lower region of 45–50 kJ/mol at the driving conditions for the adsorption heat pump. To evaluate the coefficient of cooling performance (COP) and a specific cooling power (SCP), the adsorbent-filled HEX was prepared using a small-sized corrugated-fin-type aluminum HEX and the slurry. The COP and SCP were 0.41 and 498 W/kg at 80 °C of regeneration, respectively.
This study was focused on the evaluation of the adsorption kinetics of water vapor onto silica-gel with and without an acoustic field, in an objective to reveal the enhancement mechanisms of water vapor adsorption by an acoustic wave. Adsorption uptake curves of water vapor from humidified air onto the silica-gel with and without acoustic field were measured at room temperature under various conditions, after which the adsorption kinetic parameters (fluid film mass transfer coefficient and intraparticle diffusivity) were determined from the uptake curves with the aid of numerical calculations. The results demonstrated that the acoustic field exhibited no effect on the intraparticle diffusion, because the fluid film mass transfer was the rate-limiting step under the condition of this study. In contrast, the fluid film mass transfer was enhanced by the velocity amplitude of the acoustic field. However, the diminished mass transfer was also observed in some cases. For the enhancement and diminution of adsorption rate by the acoustic wave, it was suggested that the ratio of the oscillation flow (U) to the steady flow (u), U’ = U/u, was an important factor. Moreover, the enhanced adsorption kinetics was observed under the conditions of U’ > 2, whereas the adsorption rate was diminished or invariant under the condition of U’ < 2. This would be understood from the viewpoint of the thinning and thickening of fluid film by the oscillation flow caused by the acoustic wave. Even when the direction of the oscillation flow is countercurrent to the steady flow, the thinning of fluid film by the oscillation flow is still possible under U’ = U/u > 2.
This review presents the state-of-the-art in adsorption heat pumps (AHPs) for heating applications. Crucial aspects like operating conditions, working pairs, performances, adsorbent bed forms, adsorbent heat exchanger geometries and cycle features are discussed. A comparison of AHPs with conventional heating technologies is provided, and concepts of AHPs developed by some market players are presented. Important achievements, gaps and trends of the R&D in this field are discussed.
Thick mesoporous silica (MPS) films with sufficient mechanical strength and high porosity were prepared on aluminum plates by using electrophoretic deposition (EPD) with the addition of a small amount of polyvinylbutyral (PVB, 3.5–8.0 wt%) as binder. The porosity of the MPS films was approximately 50 vol%. The film thickness could be controlled by the deposition conditions, and a thickness of ca. 50 μm is reasonable for effectively using the whole MPS film. These MPS films exhibited good water vapor adsorption-desorption properties and sufficient stability for more than 150 adsorption-desorption cycles. When used in dehumidification applications, these MPS films had a dehumidification rate of 6.3 g-H2O/g-MPS per hour, with an adsorption-desorption cycle as short as 2 min even when a low temperature of 60 °C was used to regenerate the adsorbent.
Nitrogen-doped porous carbons were prepared via chemical activation of chitosan using alkali-metal carbonates (Na2CO3, K2CO3, Rb2CO3, and Cs2CO3), and the water adsorption isotherms of prepared carbons were measured to estimate the performance of the carbons in adsorption heat pump/desiccant cooling. Pre-doping of an alkali carbonate activator into the chitosan precursor resulted in a highly developed micropore structure and the introduction of macropores. The macropore structure clearly depended on the alkali carbonate activator. Na2CO3 resulted in two-dimensional macropores because of the hard-template effect, whereas the other alkali carbonate activators resulted in three-dimensional macropores with different cell sizes. A density functional theory calculation study based on X-ray photoelectron spectroscopy analyses of nitrogen-doped activated carbons indicated that pyridinic (pyridine, pyridone, and pyridine N-oxide), amide, and quaternary N groups might be effective for low-pressure water adsorption. Although the water adsorption capacities of the prepared carbons at P/P0 > 0.5 increased with increasing micropore volume, those at the low-pressure region (P/P0 < 0.1) were dependent on the surface density of nitrogen or oxygen functional groups. In addition, the shape of water isotherms preferable for adsorption heat pump/desiccant cooling was observed for the carbons with an appropriate surface density of nitrogen functional groups.
Adsorption cooling system is driven by low‐grade heat sources and is an eco‐friendly system, is therefore considered a potential alternative to the traditional vapor‐compression refrigeration system. An exergy analysis is a tool for identifying the details of energy degradation of each process and component, but there is a critical limitation in previous works which assumed there was no spatial variation in the adsorption beds, i. e., the lumped capacity method. We have conducted both an energy and exergy analysis of an adsorption cooling system. The exergy analysis was conducted based on detailed information obtained from the CFD results of energy analysis. The numerical results provide detailed information which varies in time and space, free of the assumptions used in lumped capacity methods, by including the effects of geometric features (fin height, fin spacing, tube diameter, and thickness) and, the contact resistance between sorbent material and metallic finned tube, which affirmatively enhance the accuracy of the exergy analysis. Finally, we analyze the effect of several main parameters from the view point of the 2nd law of thermodynamics. The results show that increases in the temperature of the heat sources leads to an increase in energy performance while the exergy efficiency decreases; increases in the cooling water temperature reduces the COP, SCP, and ηex. An increase in cycle time improves the COP and ηex but reduces the SCP. The exergy analysis was conducted based on detailed information obtained from the CFD results of energy analysis. The numerical results provide detailed adsorption bed information which varies in time and space, free of the assumptions used in lumped capacity methods. The effect of several main parameters on system performance from the view point of the 2nd law of thermodynamics was discussed, herein.
Analysis of the Ad-HEx dynamic behaviour is of pivotal importance in development of advanced adsorber concepts, enabling reduction of weight and volume of the real adsorption heat pump/chiller unit, as well as its energy density enhancement.
In Chap. 2, the two main methods to study the sorption dynamics for AHT cycles were widely described: (i) the Large Pressure Jump (LPJ) method, in which adsorption is initiated by a jump of pressure over the sample, is the most adequate for pressure-driven AHT cycles; (ii) the Large Temperature Jump (LTJ) method, in which adsorption is enabled by a temperature swing of a heat exchanger wall that is in contact with the adsorbent under an almost isobaric ad/desorption stage, is the proper choice for temperature-driven AHT cycles (see Chaps. 1 and 2). In this chapter, the main factors affecting the sorption dynamics will be highlighted for temperature-driven AHT cycles by the analysis of results achieved by the two versions (namely V-LTJ and G-LTJ) of the LTJ method.
A system which is driven by low-grade heat around 60–90 °C is expected to enhance the use of the solar heat and waste heat. The adsorption refrigeration is capable of operating at low-grade heat while the challenge is how to increase the efficiency of current implementations of adsorption refrigerators. The double-effect cycles have higher COP than a conventional single-stage adsorption cycle because the heat generated from an adsorption process is recovered and reused as a heat source. The double-effect cycles consist of two adsorbers, and there exists freedom to select adsorbent for them. The water adsorbent isotherm of FAM was S shaped and highly dependent on adsorption pressure, and the combination of FAM will be effective for the double-effect cycle according to the adsorption pressure. However, operating temperature range of the double-effect cycles is higher than the conventional single-effect adsorption cycle; the double-effect cycles have lower COP below 80 °C because the condition of adsorption pressure at this temperature range is not suitable for any adsorbents. This study suggests using the double-effect adsorption cycles combined a compressor with a view to improving COP below 80 °C. The compressor sets up, and the adsorption pressure is controlled by compressed refrigerant vapor. The adsorption cycle can work under a lot of changes due to adjusting the adsorption pressure regardless of the external temperature like the heat source. The effect of the combination of adsorbents on adsorption cycle and installation position of a compressor is not clear. The objective of this study is to investigate the COP, SCE, and exergy efficiency of double-effect adsorption cycles with various installation position of a compressor and various adsorbent pairs FAM Z01, FAM Z02, and FAM Z05. The double-effect cycle is examined by means of the static cycle simulation assuming equilibrium stats where the cooling effect is dominated by driven heat source temperature, cooling water temperature, evaporator pressure, condenser pressure, and adsorption pressure. The results from the static cycle simulation imply that the hybrid double-effect adsorption refrigeration cycle is the efficient refrigeration cycle and can enhance the performance. For heat sources in the temperature range of 60–90 °C, the method is superior when the compressor is installed on the high-pressure side and adsorbent pair is Z02-Z01. COP amounts to 1.2, SCE amounts to 350 kJ/kg, and exergy efficiency amounts to 0.45 by supplying a minimal power consumption to the compressor. As a result, this system is expected to increase the non-utilized heat such as solar heat or waste heat utilization.
The objectives of this paper are to analyze adsorption heat pump (AHP) systems using different working pairs such as silica gel/water, zeolite/water, SAPO-34/water, FAPO-34/water and activated carbon/ammonia, and to carry out their boundary conditions. According to the Clapeyron diagram, adsorption equilibrium equations and energy balance equations, feasibility and economic studies under various working conditions are made. Silica gel/water, SAPO-34/water and FAPO-34/water AHPs can feasibly operate for space heating and domestic hot water. Beyond that, zeolite/water and activated carbon/ammonia AHPs can even feasibly operate for heating network or industrial heating/preheating. However, ranges of economic operation are much stricter than that of feasible operation. Silica gel/water, SAPO-34/water and FAPO-34/water AHPs are not convenient for cold winter except zeolite/water and activated carbon/ammonia AHPs. Activated carbon/ammonia AHP even can economically operate in the cold winter with −15 °C ambient temperature. Floor heating is the most convenient technique for silica gel/water, SAPO-34/water and FAPO-34/water AHPs. Zeolite/water and activated carbon/ammonia AHPs require more than 130 °C and more than 140 °C driving source for economic use, respectively. The sequence according to the value of COPH is as follows: silica gel/water, FAPO-34/water, SAPO-34/water, zeolite/water and activated carbon/ammonia AHPs.
The adsorption equilibria of water and ethanol vapour on three kinds of silica gels (SG) and active carbons (AC) with different pore size distributions were measured in the temperature region of 303 to 383K at reduced pressure of less than 0.1MPa. 1) The adsorption equilibrium curves of both adsorbates on SGs correspond to those expected from their pore size distributions. Those for SGs with mono- and di-modal micropores had the shape of one- and two-step increases respectively. The amount of ethanol adsorbed for super-AC is more than six times that for conventional ACs. 2) Heat of adsorption of water vapour on SGs is larger in the case of SG with smaller micropore. 3) Three combinations of adsorbent/adsorbate, i.e. SG and AC with smaller micropore/water vapour and super-AC/ethanol, can be applied to the adsorption heat pump. © 1993, Society of Chemical Engineers, Japan. All rights reserved.
To apply the adsorption/desorption behavior of water on zeolite to a heat storage system which can generate both warm and cold heat, equilibrium data under low relative vapor pressure were measured. Based on the data the adsorptivities under adsorption/desorption are estimated. Heat storing/releasing characteristics were also studied by using an experimental heat storage device with 20 wt-% sodium chloride solution and zeolite 13 X. Heat storing/releasing cycles which have adsorptivity higher than 0.1 kg·kg -1 per cycle even under relative vapor pressure as low as 0.1 and an evaporation process at temperatures lower than 0°C, are achieved. A water-zeolite type heat storage system using a slight amount of sodium chloride for lowering the solidification point of water is proposed for heating and freezing applications.
Adsorption equilibria of ethanol and methanol vapors on activated carbon fibers (ACF) and granular one (GAC) were measured at 30 and 50degreesC, and adsorption isotherms over a wide temperature range were predicted from the experimental equilibrium curves. The cooling effect in an ideal cycle of adsorption refrigerators was estimated under the typical operating temperature conditions from the predicted isotherms. The results obtained showed that the ACF with large surface area has high adsorptive capacity for both ethanol and methanol vapors. The cooling effect estimated for the ACF/methanol pair exceeded 300 kJ/kg, and these values were greater than those for the GAC/methanol pair. Furthermore, we could successfully prepare ACF with high bulk density (HD-ACF) from phenol resin fibers without adding any binders. The prepared HD-ACF has a dense structure with smooth fibers, and has micropores mainly in the range of the radius below 2 nm. The HD-FAC adsorbed rapidly ethanol and methanol vapors comparable to the felt-type ACF. The cooling effect on the apparent volume basis showed an extremely high value of 177 MJ/m(3) for the HD-ACF/methanol pair. Therefore, we concluded that it is feasible to apply this working pair to adsorption refrigerators.