Solar powered thermoelectric distillation system

Al-Madhhachi, Hayder ORCID: https://orcid.org/0000-0001-9440-9015 2017. Solar powered thermoelectric distillation system. PhD Thesis, Cardiff University.

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Abstract

An efficient thermoelectric distillation system was designed, constructed and tested. The unique aspect of this design is to use the waste heat from the hot side of thermoelectric module for heating of the feed water, to improve the evaporation while using the cold side of the module to cool the condenser and improve the condensation process. The developed thermoelectric distillation system produces 28.5 mL of distilled water (equivalent to 678 mL/m2) over a period of 1 hour. The corresponding electrical energy required for the water production is 0.0324 kWh, which gives a specific energy consumption of 0.00114 kWh/mL. The developed system in this research has significantly lower energy consumption than the existing thermoelectric distillation systems. The transient to steady state behaviour of the developed thermoelectric distillation system was investigated. It was found that the system reaches steady state after approximately three hours of the system operation. The water temperature in evaporation chamber was increased from 22.3 oC to 47.8 oC. Similarly, the vapour temperature was increased moderately from 20.3 oC to 30.4 oC. The steady state water production, humidity, energy consumption and COP of the thermoelectric distillation system were 15.3 mL/h, 81%, 0.0324 kWh and 1.04, respectively. Thermal models have been developed through water-vapour phase-change theory to interpret the evaporation and condensation processes involved in the fresh water production of the thermoelectric distillation system. The first model was related to the evaporation process to determine the vapour production in the system. A theoretical distillation ratio of 12% was obtained, with a predicted water temperature of 42.7 oC. This is in reasonable agreement with the 9.5% value experimentally obtained. The second ii model has been developed for the water condensation process. The developed model can be used for determining the key parameters that control the condensation processes and the system thermal performance. This model shows that the rate of water condensation is dependent upon the convection heat transfer coefficient of the cold-side heat exchanger. The fitted value of the convection heat transfer coefficient in the thermoelectric distillation system is 8 W/m2.K. Key factors that influence the total water production and water production rate have been investigated, including sample water temperature, vapour volume at sample water level, Peltier current and thermoelectric input power. The experimental data shows that an increase in sample water temperature from 30 oC to 60 oC gives a 47 % increase in total water production. Peltier current is demonstrated as a control factor in the design of an effective thermoelectric distillation system. The results show that the total water production increases by 61%, when the volume occupied by the vapour is reduced from 600 cm3 to 400 cm3 by increasing the sample water level from 10 mm to 30 mm in the system. The maximum water production is achieved by increasing sample water temperature and the corresponding optimised input power. Measurements of the distilled water show that it has similar quality to drinkable tap water in terms of pH, total dissolved solids and electrical conductivity values. Photovoltaic Geographical Information System was used to estimate the global irradiation per square meter and the solar electricity generation in kWh received by a solar panel in a specific region. Using the experimental prototype, the maximum monthly average water production is 4023.3 mL when using 8.52 kWh of electricity produced during March at the University of Kufa. The minimum average monthly water production is 2970.3 mL using 6.29 kWh of electricity produced during November.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Engineering
Uncontrolled Keywords:	Thermoelectric; Distillation; Desalination; Energy; Solar; Design.
Date of First Compliant Deposit:	15 December 2017
Last Modified:	03 Nov 2022 10:18
URI:	https://orca.cardiff.ac.uk/id/eprint/107598

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