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The aim of this paper is to study the equilibrium and dynamics of water adsorption on a commercial silica gel Siogel. This adsorbent has recently been suggested and tested for adsorptive transformation and storage of low temperature heat. The original data on the water vapour equilibrium and dynamics are compared with those earlier reported for the Fuji silica RD. This database can be used for theoretical analysis, mathematical modeling and evaluation of adsorptive cycles based on the working pair “water – Siogel” and driven by heat from renewable heat sources. [ABSTRACT FROM AUTHOR]

Methanol, and more recently ethanol, have been deeply employed as adsorbate phase (refrigerant) in adsorption chiller and heat pump applications (e.g. refrigerator adsorption ice maker). The use of anhydrous alcohols however can cause several problems related to the corrosiveness of such molecules towards light alloys (from titanium to aluminium). The problem was already highlighted in bio-fuel technology where bio-ethanol was considered as a promise alternative to fossil hydrocarbons. Water content was observed as one of the main factors influencing corrosion rate. In the present works several accelerated corrosion tests on 6061 Aluminium alloy have been carried out in autoclave in a temperature range from 110 to 135 °C with different ethanol to aluminium mass ratio. Highly exothermic reactions related to aluminium oxidation, coupled to hydrogen evolution, have been recorded. The main drawback of hydrogen evolution is the formation of a stagnant layer over the heat exchangers surface, which can limit the ethanol vapour diffusion, thus reducing adsorption/condensation rate. [ABSTRACT FROM AUTHOR]

Adsorption desalination is a novel technology to supply high-quality potable water driven by a low-temperature heat source. However, only a few composite sorbents, whose excellent performances have been demonstrated in other adsorption-based systems, have been applied in adsorption desalination (AD) systems. This study evaluated the performances of LiCl-silica gel (30 % wt) composite in a lab-scale AD system, realized by packing the sorbents beads inside a finned flat-tube heat exchanger. For the first time, the ad/desorption dynamics under various operating conditions were measured using a T-LTJ (thermal-large temperature jump) apparatus, which has not been employed for evaluation of desalination prototypes so far. The sorption dynamics was compared with silica gel, which is a standard material for AD systems. Results were used to calculate the maximum specific daily water production (SDWP) and optimized cycle time. Moreover, three design strategies of the AD system were proposed, including 2-beds, 3-beds and 4-beds. The 3-beds-configuration was selected for the composite sorbent, being able to reach an SDWP as high as 69 m3/tonne/day under the condition of T eva/cond = 20 °C and T de = 80 °C. The optimized cycle time is dependent on operating conditions, varying in the range of 240–470 s. • An innovative lab-scale desalination unit employing composite sorbent based on silica gel and LiCl is tested. • The kinetic performance under several operating conditions is compared against state-of-the-art silica gel material. • A numerical model, based on the experimental outcomes, is used to optimize the adsorption desalination unit architecture. [ABSTRACT FROM AUTHOR]

• Wave analysis method is initially introduced to estimate steady heat output. • Relationship between sorption process and output stages are established. • Influence of isotherms and design parameters on wave parameters is determined. • The maximum energy storage density through this method reaches 191.4 kWh·m−3. Sorption thermal battery has attracted burgeoning attention which is considered as a promising method to reduce energy consumption for space heating. Sorption "reaction wave" model could be used to find the criteria for stable output. However, mechanism of sorption process evolution in reactor is still unclear since the method cannot derive more reaction details. The paper initially proposes a comprehensive wave analysis method which could bring more insights of sorption thermal battery from a heat and mass transfer perspective. The wave parameters are analysed and orthogonal experiments are then carried out. Results indicate that solid sorbents with type I and V isotherms have the advantage of stable heat supply. Air velocity and inlet relative humidity have the most significant influence on the output parameters. Besides, response surface methodology is adopted to evaluate the critical parameters, e.g., relative humidity, flow rate, temperature of inlet air. The optimal system energy storage density could reach 191.7 kWh·m−3 when sorption reactor length is 0.178 m and the relative humidity is 70 % using zeolite 13X as sorbents. Therefore, the proposed wave analysis method is expected to become a potential solution which would guide sorbent selection and reactor design for sorption thermal battery. [ABSTRACT FROM AUTHOR]

• Heat pump assisted open three-phase sorption thermal battery is proposed. • System performs three patterns in liquid desorption, crystallization and dehydration stages. • The maximum average system COP is 7.54, corresponding charging temperature is 40 °C. • The optimal end state of sorbent for LiCl is either liquid desorption or dehydration stage. Open three-phase sorption thermal battery has recently received particular attention for its high energy storage density. Meanwhile, air source heat pump can be considered a potential heat source for open three-phase sorption thermal battery due to its broad applicability and high energy efficiency. However, research on the intergration of these two systems are rarely reported. A heat pump assisted sorption thermal batttery is proposed and evaluated based on a general thermodynamic analysis for charging process. Three indicators are targeted in terms of coefficient of performance (COP), energy storage rate and energy storage density. Results show that system characteristics present three different patterns, i.e., liquid desorption, crystallization and dehydration stages. When ambient condition is 20 °C and 60% RH, the maximum system average COP is 7.53, the corresponding charge temperature is 40 °C and end-state sorption capacity is 2.33 g/g. The optimal charging condition for comprehensive performance index is greatly affected by the weights of basic indicators. When the weight of energy storage density is dominating, three-phase sorption performs better. Within the range of this study, the optimal sorbent end state locates on either liquid desorption stage or dehydration line. [ABSTRACT FROM AUTHOR]

The present paper analyzed the thermal performance and control optimization of a solar system based on seasonal sorption storage for domestic applications. The system control, which could choose between 41 operational modes, was optimized based on operational costs and maximization of sorption system use. The system was composed by 17.5 m2 of evacuated tube collectors, 3.6 m3 of composite sorbents based on lithium chloride and a stratified water tank. High efficiency of a sorption storage system was obtained when continuous charges or discharges occur, which, in this study, depended on weather conditions (ambient temperature and solar irradiation). The operational economic benefits were maximized using a sorption system with 9% less capacity and, therefore, less storage volume. The sorption thermal energy storage system obtained energy densities of 90 and 106 kWh/m 3. The whole system could supply 35% of the total thermal demand of a single family house in Nuremberg. The study concluded that the control optimization of a seasonal sorption system is a key factor to make the technology competitive, define its optimal size and, therefore, maximize its energy density in further designs. • A solar-driven seasonal sorption storage system was analyzed under optimal control. • 35% of the thermal demand of a single-family house located in Central Europe was supplied. • Maximum energy density of the sorption storage system of 106 kWh/m 3 was obtained. • Control optimization showed minimum operational costs with 9% less sorption storage size. [ABSTRACT FROM AUTHOR]

• A novel hybrid sorption chiller was investigated. • Electricity energy savings from 15% to 25% can be achieved by the hybrid system. • The overall performances are slightly affected by the sorption driving temperature. • Cascade coupling let to enhance performances of hybrid system. The energy demand of industries accounts for about 30–35% of world yearly energy consumption, a relevant percentage is due to the need of heating and cooling demand. Solar heating and cooling technologies can be integrated in industrial processes to reduce the fossil fuels consumption as well as the related greenhouse gas emissions. This paper reports the experimental analysis of a novel hybrid sorption-compression chiller for cooling and refrigeration purposes in cascade layout, which uses silica gel/water for the sorption cycle and a low Global Warming Potential (GWP) refrigerant, i.e. propylene for the compression cycle. The experimental results highlighted the flexibility of the system in terms of performances and operating conditions, these were compared to the theoretical performances and it was found out that electricity energy savings from 15% to 25% can be achieved when using the hybrid system over a compression one with the same cooling capacity. The results were converted in performance maps and processed in a statistical model, in order to get a simplified expression for determining the overall performances of the hybrid system through variables that could be measured by a final user, such as the operating temperatures. Optimization strategies were identified for a further enhancement of the performance of the chiller, i.e. the reduction of the electricity consumption, by controlling the intermediate temperature (evaporation temperature of the sorption chiller) through sorption cycle management and the use of variable speed of the pumps in all the circuits to reduce the parasitic consumption especially at low part loads. [ABSTRACT FROM AUTHOR]

One of the main limitations for the wide diffusion of sorption systems, either as stand-alone and in hybrid configurations, is the low heat transfer inside the adsorber, as well as the low volumetric cooling power. In this context, the present paper reports the experimental activity on four different advanced configurations for the adsorber, based on microchannel heat exchangers where the gap between the channels is filled with porous structures where zeotypes of SAPO-34 family were synthetized. The porous structures evaluated are high-density fins, two different aluminium foams and compressed chips from the waste of aluminium machining. The sorption dynamic and cooling power density of each structure were measured through a Gravimetric Large Temperature Jump testing apparatus. The results obtained showed that the best-performing configuration is the one with high-density fins, that, for a 90/30/20 °C cycle showed a Specific Cooling Power up to 1.1 kW/kg. The other structures exhibit a much slower adsorption process, corresponding to power densities of about 0.3 kW/kg. The results were used for sizing a full-scale adsorber, whose expected Volumetric Cooling Power is 500 kW/m3. [ABSTRACT FROM AUTHOR]

• Capability of Posidonia Oceanica seagrass as a reinforcement material in adobe specimens is analysed. • Posidonia Oceanica seagrass is a biomass by-product from the Mediterranean coastlines. • First, the fibres were evaluated to understand their behaviour. • Samples were subjected to mechanical and thermal tests. • Seagrass fibres with their natural long length showed the most suitable mechanical behaviour. There is an incipient necessity and interest of generating sustainable materials for application in green buildings. In this study, the capability of Posidonia Oceanica seagrass, a biomass by-product from the Mediterranean coastlines, is analysed as a reinforcement material in adobe bricks. For this purpose, earthen specimens with these sea-plant fibres were compared with the most traditional additives for this purpose, i.e. straw-based adobes. Both biomass fibres were included with different lengths and quantities. First, to understand their behaviour, the fibres were evaluated; water absorption and tensile strength tests were performed. Test specimens themselves were subjected to mechanical and thermal tests as well as measuring dimensional changes. Tested as fibres, straw presented higher tensile resistance and water absorption than seagrass; but tested within adobe specimens, straw containing samples had worse mechanical behaviour than those containing seagrass. Specially, adobe with Posidonia Ocenaica seagrass fibres with their natural long length showed to be the most suitable in terms of mechanical behaviour. Furthermore, good thermal conductivity results were achieved with this level of biomass reinforcement, generating a sustainable and value-added construction product. [ABSTRACT FROM AUTHOR]

This paper assesses the mechanical stability and dehydration behaviour of a new composite material constituted by magnesium sulphate hepta-hydrate, used as filler at vary contents, and a porous silicone, used as matrix in order to evaluate its applicability in sorption thermal energy storage field. This new composite was developed to avoid the typical issues of salt hydrates such as swelling, agglomeration and corrosion issues occurring during hydration/dehydration process. A preliminary physical-mechanical characterization, by means of morphological and calorimetric analysis, was carried out to investigate the main properties of the composite foams. The morphological characterization showed that the foam pores were homogenously distributed and well interconnected to each other. Thermo-gravimetric dehydration tests, have demonstrated that the tested samples are able to exchange efficiently water. Static compression tests evidenced a high compression stability of the material, indicating a high flexibility of the cellular silicone structure. Furthermore, cyclic compression test was performed to evaluate the progressive loss of salt at increasing number of the cycles. After 50 cycles, a reduction of salt hydrate up to 13% was observed. This behaviour, that is potentially a critical factor in these composite structures, was studied for showing that the loss of the salt does not compromise considerably the sorption storage performance of the filled silicone foams. Eventually, the assessment of thermo-gravimetric characteristics and mechanical stability was performed on the MgSO 4 ·7H 2 O silicone composite foam. • Polymeric foams filled by MgSO 4 ·7H 2 O for seasonal TES applications. • Evaluation of foam features. • Evaluation of foam efficiency for TES application. [ABSTRACT FROM AUTHOR]