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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.

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.

Abstract With this work, we introduce numeric three-dimensional simulation of metal spiking into highly boron-doped surfaces of n-type silicon solar cells, which is moreover performed with a simulation of the quasi-steady-state photoconductance technique. This setup serves as a virtual experiment to simulate the dark saturation current density j 0,met of metallized boron-doped emitters with respect to metal spikes originating from the silver–aluminum (Ag–Al) contact. With the results obtained from this simulation model we approach quality and quantity of increased j 0,met and give detailed insight to which degree a solar cell’s performance is possibly harmed by this effect. We show that metal spikes penetrating into boron-doped emitters are of harmless nature concerning j 0,met until their tips reach depths where boron doping concentration is lower than approximately 10 18 cm −3 . Deeper spikes then lead to an exponential increase in j 0,met as more and more carriers from emitter and also the base are able to diffuse to its tip and recombine there. With the help of j 0 -results obtained experimentally in combination with the simulation results, we discuss the influence of spikes on emitter recombination, the benefits that can be achieved with deeper emitter doping profiles, and suggestions for the further development of pastes to contact boron-doped surfaces.

Abstract With this work, we introduce numeric three-dimensional simulation of metal spiking into highly boron-doped surfaces of n-type silicon solar cells, which is moreover performed with a simulation of the quasi-steady-state photoconductance technique. This setup serves as a virtual experiment to simulate the dark saturation current density j 0,met of metallized boron-doped emitters with respect to metal spikes originating from the silver–aluminum (Ag–Al) contact. With the results obtained from this simulation model we approach quality and quantity of increased j 0,met and give detailed insight to which degree a solar cell’s performance is possibly harmed by this effect. We show that metal spikes penetrating into boron-doped emitters are of harmless nature concerning j 0,met until their tips reach depths where boron doping concentration is lower than approximately 10 18 cm −3 . Deeper spikes then lead to an exponential increase in j 0,met as more and more carriers from emitter and also the base are able to diffuse to its tip and recombine there. With the help of j 0 -results obtained experimentally in combination with the simulation results, we discuss the influence of spikes on emitter recombination, the benefits that can be achieved with deeper emitter doping profiles, and suggestions for the further development of pastes to contact boron-doped surfaces.

Abstract Fluidized-bed electrodes could offer an interesting way to increase the electrode surface area applicable in electrochemical processes when the problem of poor electrical contact within the particle bed could be overcome. We recently demonstrated, that the contacting can be improved by the use of magnetizable electrode particles and the superposition of a magnetic field. However, details of the magnetic influence on the charge transport are still mostly unknown. In this work, we investigate the electrodynamics of a fluidized bed electrode with and without the superposition of a magnetic field by means of chronoamperometry and electrochemical impedance spectroscopy (EIS). In the chronoamperometric studies two types of charge transfer mechanism can be distinguished by the slope of the resistance increase with increasing distance between the electrodes. In close proximity to the electrodes direct conductive charge transfer along statistically formed particle chains dominates. Because the probability of uninterrupted particle chains quickly diminishes with increasing length, above a certain distance of approx. 6 mm a second, so-called convective, charge transfer mechanism dominates. This mechanism is based on the transfer of electrons between colliding fluidized particles and corresponds with a substantially higher specific resistance. The conductive charge transfer mechanism can be enhanced by up to a factor of four applying a superimposed magnetic field, while the second mechanism shows only a weak field dependence. The presented equivalent circuit model and the magnetic field dependency of its parameters contribute to a deeper understanding of the novel magnetically stabilized fluidized bed electrode and demonstrate the usefulness of EIS measurements for the prediction of the effectiveness of a particle based electrochemical reactor.

Abstract Fluidized-bed electrodes could offer an interesting way to increase the electrode surface area applicable in electrochemical processes when the problem of poor electrical contact within the particle bed could be overcome. We recently demonstrated, that the contacting can be improved by the use of magnetizable electrode particles and the superposition of a magnetic field. However, details of the magnetic influence on the charge transport are still mostly unknown. In this work, we investigate the electrodynamics of a fluidized bed electrode with and without the superposition of a magnetic field by means of chronoamperometry and electrochemical impedance spectroscopy (EIS). In the chronoamperometric studies two types of charge transfer mechanism can be distinguished by the slope of the resistance increase with increasing distance between the electrodes. In close proximity to the electrodes direct conductive charge transfer along statistically formed particle chains dominates. Because the probability of uninterrupted particle chains quickly diminishes with increasing length, above a certain distance of approx. 6 mm a second, so-called convective, charge transfer mechanism dominates. This mechanism is based on the transfer of electrons between colliding fluidized particles and corresponds with a substantially higher specific resistance. The conductive charge transfer mechanism can be enhanced by up to a factor of four applying a superimposed magnetic field, while the second mechanism shows only a weak field dependence. The presented equivalent circuit model and the magnetic field dependency of its parameters contribute to a deeper understanding of the novel magnetically stabilized fluidized bed electrode and demonstrate the usefulness of EIS measurements for the prediction of the effectiveness of a particle based electrochemical reactor.

Abstract In this first part a comprehensive thermophysical characterisation of six activated carbons – based on coconut, peat and stone coal with focus on thermally driven chillers is reported. Pore and surface analysis are performed using N2 and CO2 adsorption. Furthermore the density and heat capacity of the samples is determined. Methanol adsorption measurements for evaporation between −5 °C and 35 °C and driving temperatures up to 130 °C are realized using a thermobalance and evaluated using the Dubinin–Astakhov (DA) approach. Based on the given DA equations, the possible loading lifts for typical applications like 95°-35°-7 °C are calculated. The samples show very attractive maximum loading lifts up to 0.385 g g−1. Furthermore the mass and volume specific cooling enthalpy of 244 kJ kg−1 and 126 kJ dm−3 under realistic conditions demonstrates the good performance of this working pair.

Abstract In this first part a comprehensive thermophysical characterisation of six activated carbons – based on coconut, peat and stone coal with focus on thermally driven chillers is reported. Pore and surface analysis are performed using N2 and CO2 adsorption. Furthermore the density and heat capacity of the samples is determined. Methanol adsorption measurements for evaporation between −5 °C and 35 °C and driving temperatures up to 130 °C are realized using a thermobalance and evaluated using the Dubinin–Astakhov (DA) approach. Based on the given DA equations, the possible loading lifts for typical applications like 95°-35°-7 °C are calculated. The samples show very attractive maximum loading lifts up to 0.385 g g−1. Furthermore the mass and volume specific cooling enthalpy of 244 kJ kg−1 and 126 kJ dm−3 under realistic conditions demonstrates the good performance of this working pair.