A scientist in Turkey has imagined Hybrid atmospheric water harvesting systems supported by PV and compared their performance. They were all supposed to work with R1233ZD (E), R1234YF and R600A, as well as R32 cooling agents. The required PV system size was as low as 20 m2.
A researcher from Turkey’s Tarsus University has investigated eight different configurations of hybrid atmospheric water harvest (AWH) systems supported by PV.
AWH Systems extracting water vapor from the air and condense it in liquid water, using desplans, heat exchangers and vapor compression -cooling (video recorder).
“AWH is an emerging technology that allows the extraction of fresh water from ambient air by capturing atmospheric moisture. This approach offers a sustainable water supply solution, in particular in regions that miss centralized water infrastructure or limited by geographical and hydrological limitations,” said the research author, Kamil Neyphel eyphel. “Most systems use the evaporation condensation principle via the video recorder, while some desperate wheels integrate for improved efficiency.”
The systems
In configuration 1, PV panels provide electricity to an electric heating, which heats the regeneration air used by the dry wheel. The drying wheel removes moisture from the procession air and transfers it to the regeneration air, which is moistened and then led by the evaporator, where it is cooled under the temperature of the dew point, which leads to condensation and collecting water.
In configuration 2, a heat exchanger is placed between the drying wheel and the evaporator, while in configuration 3 a second drying wheel downstream from the first dry wheel is integrated. In configuration 4, a heat exchanger is placed between the second dry wheel and the evaporator. Configurations 5-8 are comparable to 1-4, where the change is the positioning of the condenser of the VCR unit upstream of the electric heater. That is for a better use of the waste heat that has been dismissed from the condenser.
All eight systems were tested with three environmentally friendly coolants, namely R1233ZD (E), R1234YF and R600A, as well as conventional Difluoromethane (R32). They were all simulated in the engineering comparison solver (ESS) program, with changing regeneration temperatures and airflow speeds ranging from 70 ° C and 252 kg/h to 360 kg/h respectively. For the first test round, the ambient temperature was set at 25 ° C, the relative humidity at 75%and the solar radiation up to 650 W/m².
The results
“Under the analyzed setups, Configuration 8, with two -stage drying wheels, a heat exchanger and waste heating, consistently demonstrated superior performance,” the researcher said. “It achieved the lowest electricity consumption, the smallest required PV panel area and the highest water harvest efficiency (whe).”
More specifically, when the regeneration temperature was set to 70 ° C, the electricity consumption of the system was 2-2.2 W, depending on the coolant. This corresponded to a PV planting area ranging from 20 m2 to 23 m2, also depending on the coolant. When the regeneration temperature was set at 100 ° C, the reach were 4.2-4.4 W and 44-48 m2 respectively. The whe at 70 ° C was between 0.76 kg/kWh and 0.8 kg/kWh, and between 0.4 kg/kWh and 0.42 kg/kWh at 100 C.
Because the performance of system 8 was the most effective, this system was further investigated under four climate zones: in moderate (m) the outside temperature was set to 22 ° C and the relative humidity to 50%; They were set at 25 C and 75%in moderate and damp (M&H); They were 35 C and 70%in warm and moderately moist (W & MH); And in warm and dry (W&D) they were set at 40 C and 27%respectively.
“The performance confections (COP) of the cooling unit achieved the highest value in the W&MH zone, where the evaporation temperature was also the highest. The second highest COP was observed in the M&H zone, which also had the second highest evaporation temperature,” the researcher concluded. “The highest whet and water harvesting speed (WHR) values were achieved in the W&MH zone, indicating that this climate zone is most suitable for the implementation of the proposed system configuration.”
His findings were presented in “Photovoltaic supported hybrid atmospheric water harvesting systems: comparative performance analysis of various configurations“Published in Case studies in Thermal Engineering.
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