Solar powered thermoelectric distillation system

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

Evaluation of the convection heat transfer coefficient in a thermoelectric distillation system

In this paper, a thermal model has been developed for a water distillation system which uses a thermoelectric module. The thermoelectric module cools a heat exchanger and extracts the latent heat of condensation from the water vapour at the cold side, releasing heat at the hot side to supplement the water heating. It is important to take into account the temperature distribution and the heat transfer of the thermoelectric distillation system to enhance the thermal performance. The model shows that the rate of water condensation is dependent upon the cold side temperature of the thermoelectric module, vapour temperature, geometry of the heat exchanger and the convection heat transfer coefficient of the heat exchanger at the cold side. The thermal model is used to analyses the experimental data of the thermoelectric distillation system. The results shows that the local convection heat transfer coefficient is 8 W/m2.K. Measurements of the distilled water show that the produced water has similar quality to the tap water in terms of PH, total dissolved solids and electrical conductivity values

Validation of vapour / water production in a thermoelectric distillation system

In this study, mathematical calculations developed through water-vapour phase-change theory is used to interpret the processes involved in the fresh water production of a thermoelectric distillation system. The rate of water production depends on various parameters of vaporization phenomena such as water and vapour temperatures, pressure, specific volume, heat capacity and water-vapour surface area. The water-vapour surface area is constant 10 x 10 cm2, the initial depth of the sample water is 3 cm and the air occupies the 500 cm3 volume inside the chamber. The volume and the mass of vapour and water at water-vapour interface are calculated through one hour of the system operation. The temperatures of the system components, humidity and water production of the thermoelectric distillation system are measured. As a result, an increase in the temperature of water and hot side of the thermoelectric module leads to an increase in the water production by increasing the vapour formation at atmospheric pressure. After one hour of system operation, the water production reaches 34.5 mL and the humidity inside the chamber increases from 51 % to 74 %. The results also show the distillation ratio is 11.5%. The mathematical calculations validate the experimental data with reasonable agreement

Effective thermal analysis of using peltier module for desalination process

The key objective of this study is to analyse the heat transfer processes involved in the evaporation and condensation of water in a water distillation system employing a thermoelectric module. This analysis can help to increase the water production and to enhance the system performance. For the analysis, a water distillation unit prototype integrated with a thermoelectric module was designed and fabricated. A theoretical model is developed to study the effect of the heat added, transferred and removed, in forced convection and laminar flow, during the evaporation and condensation processes. The thermoelectric module is used to convert electricity into heat under Peltier effect and control precisely the absorbed and released heat at the cold and hot sides of the module, respectively. Temperatures of water, vapour, condenser, cold and hot sides of the thermoelectric module and water production have been measured experimentally under steady state operation. The theoretical and experimental water production were found to be in agreement. The amount of heat that needs to be evaporated from water-vapour interface and transferred through the condenser surface to the thermoelectric module is crucial for the design and optimization of distillation systems

Effective use of thermal energy at both hot and cold side of thermoelectric module for developing efficient thermoelectric water distillation system

An efficient thermoelectric distillation system has been designed and constructed for production of drinkable water. The unique design of this system is to use the heat from hot side of the thermoelectric module for water evaporation and the cold side for vapour condensation simultaneously. This novel design significantly reduces energy consumption and improves the system performance. The results of experiments show that the average water production is 28.5 mL/h with a specific energy consumption of 0.00114 kW h/mL in an evaporation chamber filled with 10 × 10 × 30 mm3 of water. This is significantly lower than the energy consumption required by other existing thermoelectric distillation systems. The results also show that a maximum temperature difference between the hot and cold side of the thermoelectric module is 42.3 °C, which led to temperature increases of 26.4 °C and 8.4 °C in water and vapour, respectively

Key factors affecting the water production in a thermoelectric distillation system

A thermoelectric distillation system has recently been demonstrated to have a great potential of improving the efficiency of distillation processes due to the use of waste heat from the hot side of thermoelectric module to assist evaporation while the cold side for condensation. This work investigates the key factors that affect the water production in a thermoelectric distillation system. An experimental investigation was performed to investigate the influence of evaporation temperature, vapour volume, Peltier current and input power on the water production rate. The results of the experiment show that an increase in the sample water temperature from 30 °C to 60 °C led to an increase in total water production by 47%. In addition, an increase in total water production by 58% was obtained by reducing the vapour volume from 600 cm3 to 400 cm3 during a 3-h operation. The maximum water production rate is achieved by appropriate selection and control of the Peltier current to the thermoelectric device based on the operating condition of the distillation system