Development of an autonomous, energy-efficient solar-assisted cooling system for agricultural greenhouses using phase-change materials and nanofluids

Project Abstract

This research presents the design, development, and evaluation of an autonomous, energy-efficient cooling system for agricultural greenhouses that integrates solar thermal energy, phase-change materials (PCMs), and nanofluids to maintain optimal microclimate conditions while minimizing electrical energy consumption. The system employs a solar-inspired, hybrid thermal management architecture that leverages concentrated solar collectors to heat a PCM–nanofluid slurry, enabling latent heat storage and rapid thermal buffering during diurnal temperature fluctuations. The PCM chosen exhibits high latent heat capacity, suitable phase change temperature aligned with greenhouse cooling needs, and low supercooling to ensure reliable performance. Nanofluids, engineered by dispersing functionalized nanoparticles in a base coolant, enhance convective heat transfer and thermal conductivity, enabling efficient charging and discharging cycles of the latent storage while reducing pumping power requirements. A multi-physics model integrates solar irradiation, PCM phase transition dynamics, nanofluid thermophysical properties, greenhouse heat transfer, and humidification effects to predict transient thermal behavior under realistic climatic scenarios. The model is validated through laboratory-scale experiments and field trials in a controlled greenhouse environment, capturing performance metrics such as peak cooling rate, latent storage utilization factor, solar-to-cooling efficiency, coefficient of performance (COP), and energy savings relative to conventional ventilation and cooling strategies. Key innovation lies in the synergistic coupling between solar-assisted sensible cooling, latent heat storage with PCM, and enhanced heat transfer via nanofluids, which collectively reduce electrical energy demand by leveraging renewable thermal sources and reducing actuator loading on fans and cooling pads. Optimization studies are conducted to select PCM eutectic compositions, nanoparticle types and concentrations, and flow-path geometries that minimize charging/discharging losses, suppress PCM supercooling, and maximize thermal responsiveness to changing solar input and greenhouse load. The control strategy combines model-p predictive control with adaptive hysteresis to regulate storage charging during high solar availability and discharging during peak cooling demand, ensuring smooth indoor climate setpoints and humidity control without auxiliary cooling. Offshore and on-site validations demonstrate robust performance across seasonal variations, indicating improvements in crop yield potential, quality, and reduced water usage due to optimized transpiration microclimates. Economic and environmental assessments quantify levelized energy costs, payback period, carbon footprint reduction, and lifecycle benefits of the integrated system compared to conventional greenhouse cooling. Sensitivity analyses reveal critical parameters affecting system viability, including PCM thermal reliability, nanoparticle stability, solar collector efficiency, and ambient temperature swings. The study contributes a scalable, modular framework for adopting solar-assisted PCM–nanofluid cooling in modern agriculture, offering a pathway toward autonomous climate control, enhanced energy resilience, and sustainable greenhouse productivity.

Project Overview

What This Project Is About

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A straightforward exploration of a cooling system for greenhouses that uses solar power and special materials to keep temperatures stable. The project looks at how phase-change materials (PCMs) store heat and how nanofluids improve heat transfer, with the goal of reducing energy use while maintaining plant-friendly conditions.

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The Problem It Addresses

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Greenhouses often rely on electricity for cooling, which costs money and increases emissions. There is a need for cheaper, cleaner cooling that works well in sunny, hot climates. The project investigates how to combine solar energy with advanced materials to create an autonomous cooling system that reduces dependence on grid power.

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Objectives of the Project

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1. Assess how solar-powered cooling can be integrated into a greenhouse.
2. Evaluate the use of phase-change materials to smooth temperature swings.
3. Explore nanofluids to improve heat transfer in the cooling loop.
4. Design a small demonstration system and test its performance.
5. Analyze energy savings and potential emissions reductions.

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What You Will Do Step by Step

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1. Review basic greenhouse cooling needs and choose target climate data.
2. Select PCM and nanoparticle options suitable for low-temperature storage and heat transfer.
3. Develop a simple system layout: solar collector, storage, and cooling loop.
4. Build a lab-scale prototype and install sensors to monitor temperature and flow.
5. Run experiments under different sun and ambient conditions.
6. Process data to compare energy use with and without the autonomous system.
7. Assess practicality, costs, and potential environmental impact.
8. Summarize findings and suggest improvements for real-world use.

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Expected Outcome

The project should demonstrate that a solar-powered, PCM- and nanofluid-based cooling system can maintain greenhouse temperatures with lower energy use, offering a feasible route to quieter, greener, autonomous cooling for farms.