The evaluation of a new air water generator (AWG) based on absorption and reverse osmosis is described. For the evaluation, an aqueous lithium bromide solution has been selected from a wide range of liquids as the absorbent. At high salt mass fractions, the aqueous lithium bromide solution has a low vapour pressure and a high osmotic pressure. The low vapour pressure ensures that the water vapour can be absorbed from the air, but the high osmotic pressure leads to high pressures over the membrane. Due to the high osmotic pressures, several reverse osmosis membrane modules are necessary and salt solution has to be present on both sides of the membrane, which leads to an additional inlet on the permeate side. Models for the absorber, the reverse osmosis membrane module and the complete multi-stage reverse osmosis system have been developed in Python. The model of the complete system has then been used to simulate the performance of the AWG at different boundary conditions. The simulations have shown that based on the defined assumptions, extracting water from the air with absorption and reverse osmosis is possible and that the energy demand per litre of pure water is similar to AWG systems which use condensation.

Microwaves are a fast way to dry moist goods through volumetric heating. During the drying process, materials change their electrical properties. As a result, the impedances at the feed port of the applicator will change and the microwave source is not matched anymore. The amount of reflected power increases and the process efficiency reduces. New semiconductor high power sources can perform a dynamic impedance matching. A lab scaled functional model with two sources was designed and realized. For measuring the scattering parameters during the process run, an embedded two-port vector network analyzer was added. Measurement results confirm the feasibility of the concept.   Keywords: Microwave drying, dynamic efficiency optimization, multichannel feed, solid state based microwave source

Vor 140 Jahren verkehrte die Honigmannsche Natronlok in Aachen. Ihre Fahrten blieben eine Episode der Eisenbahngeschichte – ihr Wirkprinzip dagegen macht man sich aktuell bei einem thermischen Energiespeicher zunutze.

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Technologies for obtaining drinkable water are becoming more important as global water consumption steadily increases and climate change progresses. One possibility for obtaining water is the extraction of water vapor from ambient air by means of air water generators (AWG). Previous studies in the field of AWG have mainly dealt with the condensation of humidity on cold surfaces with a cooling system or with absorption and thermal desorption. In this paper, another possibility for AWG is investigated, specifically AWG using absorption and reverse osmosis. For this purpose, models have been set up for an absorber operated in countercurrent and reverse osmosis membrane modules operated in co-current and countercurrent. With these models, simulations with different boundary conditions were then carried out using the programming language Python. The simulations have shown that the reverse osmosis membrane modules operated in countercurrent generally have a lower energy demand and require fewer reverse osmosis stages than those operated in co-current.