Innovative Off-Grid Dual Refrigeration System Using Repurposed RV Components

Step 1: Dismantling and Preparing the Old RV Refrigerator

The initial phase involves carefully removing all external fittings, electrical components, and the ammonia-based cooling system from the vintage RV refrigerator. This thorough disassembly ensures a clean workspace free from residual chemicals. Once cleared, the interior of the unit must be meticulously cleaned to eliminate any old refrigerants or contaminants, creating an ideal environment for the new cooling setup.

This project introduces dual cooling methods: the primary approach involves circulating cooled water through the refrigerator to lower its internal temperature, and the secondary method employs an evaporative cooling mechanism. To implement this, two water pipes are strategically positioned along the refrigerator’s edges, with cotton cloth wrapped around the sides. As water flows down these cloths, it evaporates, which actively cools the surrounding air and the refrigerator interior.

Step 2: Integrating the Fish Tank Pump for Water Circulation

Powering this eco-friendly cooling system requires an inverter connected to a deep-cycle battery, which in turn is charged by a compact 25W solar panel. An 8W electric fish tank pump is wired to the inverter, functioning as the heart of the water circulation system. This pump pushes water from a dedicated reservoir—such as a water tank or well—through the coils and back, creating a continuous flow that absorbs heat from the refrigerator’s interior and transfers it away efficiently.

Step 3: Installing Polyethylene Tubing Coils for Heat Exchange

Inside the refrigerator, two long coils of high-quality polyethylene tubing—each approximately 100 feet in length—are carefully installed. These coils are attached to an existing heat sink, which serves as a dissipative element. As water circulates through these coils, it absorbs heat from within the fridge, effectively lowering the internal temperature. The cooled water then transfers this heat to the heat sink, which dissipates it into the surrounding air, maintaining a stable cool environment inside the unit.

Step 4: Enhancing Cooling Efficiency with Evaporative Principles

To significantly boost the system’s cooling capacity, an evaporative cooling setup is integrated using aluminum U-shaped channels fitted along all edges of the refrigerator. These channels are designed to hold absorbent cotton material within, facilitating water wicking and evaporation. The outlet water from the coils flows into these channels, where it saturates the cotton cloth and flows downward by gravity. As the water evaporates from the cotton, it cools the air around it, thus further lowering the temperature inside the fridge.

For even water distribution and consistent cooling, the U channels are interconnected at the corners via flexible garden hoses. This network allows excess water to flow from one channel to another, preventing stagnation and ensuring uniform moisture across all cotton pads. After installation, the cotton sheets are stretched around the interior of the refrigerator, tucked into the channels, with wires securing them in place. An additional tee connector is employed to enable water to flow from both sides of each channel, ensuring even saturation.

To optimize airflow and cooling efficiency, an air gap is maintained between the cotton sheets and the interior surfaces of the refrigerator. This gap prevents direct contact, allowing moisture-laden air to circulate freely, which enhances the evaporative cooling process. The combined use of repurposed components, solar-powered water circulation, and evaporative techniques results in a highly efficient, off-grid refrigeration system capable of maintaining cool temperatures under challenging conditions, all while minimizing energy consumption and environmental impact.