Design Development and Modeling of High CoP Peltier Assisted Thermal Desalination System with Latent Heat Recovery

Abstract

The persistent global crisis of freshwater scarcity underscores the urgent need for sustainable, decentralized, and energy-efficient desalination solutions. While large scale desalination plants utilizing Multi-Stage Flashing (MSF), Multi-Effect Distil lation (MED), and Reverse Osmosis (RO) technologies prioritize throughput and efficiency through economies of scale, decentralized systems such as solar stills, humidification-dehumidificationunits, andmembranedistillationmodulesoffersim plicity and minimal external energy dependence but suffer critically from low pro ductivity. Although thermoelectric modules, specifically Peltier devices, have re cently been recognized for enhancing condensation and evaporation performance in small-scale desalination systems, the existing literature reveals a significant re search gap in the absence of a comprehensive approach for closed-loop latent heat recovery using thermoelectric modules. The thesis addresses this critical gap by proposing, developing, and rigorously validating a novel hybrid-source thermal desalination system that uniquely inte grates Peltier modules both as active heat pumps for latent heat recycling and as pre cise, non-invasive thermal sensors for enhanced system monitoring and control. The developed system employs a closed-loop latent heat recovery mechanism in which the Peltier module simultaneously facilitates evaporation and condensation. Oper ating under minimal temperature gradients, this design maximizes the system’s co efficient of performance (COP) and significantly reduces energy input. Theoretical frameworks groundedinthermoelectric principles, latent heat transfer analysis, and precise boiling water temperature modelling were developed to predict system be haviour comprehensively under varying operational conditions. Experimental val idation confirms substantial improvements in freshwater productivity and energy efficiency: condensation onset time is significantly reduced from 58 minutes in a conventional heater-only system to 40 minutes in the developed Peltier-assisted sys tem at 4A current, with water production increasing by approximately 50%, from 0.848 L to 1.272 L. Furthermore, the system efficiency demonstrates a notable im provementfrom54.93%(conventional heater-only operation) to 64.83% (with Peltier assistance at 3A current). Experimentally obtained COP values (8.30, 4.17, 2.23, and 1.50 at respective currents of 1A, 2A, 3A, and 4A)stronglycorroborate the theoretical predictions, highlighting the system’s robust latent heat recovery capability. Whileaddressing the longstanding challenge of precise internal and surface tem perature monitoring in operational desalination environments, this research inno vatively repurposes the Peltier module as a precision sensor, capitalizing on the in trinsic Seebeck effect. An analytical electrothermal model linking internal temper ature differentials directly to measurable load currents was developed and experi mentally validated. Complemented by material characterization (Scanning Electron Microscopy and Energy Dispersive X-ray spectroscopy), this model reliably iden tifies the intrinsic material composition of the Peltier module to identify the mate rial parameter of the Peltier module, accurately predicting surface temperatures and module voltages within exceptionally low error margins (below 1% and 2%, respec tively). Sensitivity analysis further establishes the dominant role of the Seebeck co efficient, underscoring its criticality for accurate temperature estimation and system control, while clarifying that variations in internal resistance are of minor influence under typical operating currents. This novel dual-functionality not only provides unprecedented accuracy in real-time thermal management but also significantly en hances the predictive fidelity and robustness of desalination system modeling. Further contribution of the thesis extends beyond steady-state conditions to dy namic modeling and analysis of the thermoelectric system, essential for robust real time control and adaptability. Employing small-signal linearization methods, gov erning thermoelectric and thermal energy balance equations were analytically de rived and transformed into frequency-domain transfer functions. A reduced-order second-order transfer function clearly illustrates dependencies on key operational parameters such as applied current and cold-side temperature. Frequency-domain (Bode) analyses uncover how the system’s dominant poles, zeros, and overall gain evolve dynamically, revealing new insights into the thermoelectric system’s intrin sic physical mechanisms and stability. Comprehensive simulations confirm that the developed dynamic model facilitates precise and robust control of temperature set points under varying thermal loads and ambient conditions, providing an essential scientific foundation for future model-based control strategies and scalable imple mentations. Overall, the thesis makes substantial theoretical and practical contributions to thermoelectric technologies, thermal management, andsustainable water-energy so lutions. By pioneering the dual use of Peltier modules for closed-loop latent heat recovery and precision thermal sensing, coupled with dynamic modeling insights and comprehensive performance evaluation, the present research work sets a robust foundation for advancing decentralized thermal desalination systems, providing a transformative solution to global freshwater scarcity challenges.