Globally, over two billion individuals lack a source of clean water. Over 50% of all chronic human diseases in the world originate from drinking polluted water. Due to financial, logistical, or material-based concerns with existing purification systems such as multi-layer filtration mechanisms or purification tablets, access to clean water remains one of the world's largest global health problem today.

In 2005, the Slingshot water purifier utilizing vapor compression distillation was proposed as a potential solution to the water purification problem. While the Slingshot was capable of producing water for a small village in a day, early prototypes cost nearly $100,000, causing the project to be discontinued. The goal of this project is to design and construct a solar-powered, sub-$50 portable water purification apparatus based on the Slingshot purifier capable of producing clean, drinkable water from any polluted water source.

A proof-of-concept prototype was created using a modified tea kettle, copper piping, and other low-cost, low-maintenance structural components. Initially, a two-part heat distiller incorporating several heat exchangers and a vapor compression system was designed. The vapor compression system utilized a pressure chamber (carbonated beverage bottle) with a mechanical compressor (syringe and piston). A prototype was attempted; however, safety regulations regarding gaseous pressures required a different approach.

In order to prove the affordability and portability aspects of the revised design, a self-sustaining vertical distiller incorporating a dual-purpose heat exchanger was created. As the temperature within the boiling chamber increased and steam was created, vapor condensed along the cooler feed water pipe extending through the chamber. The heat of the steam was transferred into the input water, raising the water temperature from room temperature to nearly 90°C. This preheated water was then released into the boiling chamber.

Performance of the prototype was measured through experiments involving tap water, a saline solution, and artificial urine. The pH, Turbidity, and Total Dissolved Solids (TDS) were recorded before and after each trial to evaluate water quality. Serving as the best indicator for the test solutions, the TDS significantly decreased from a starting value of over 20,000 ppm (saline solution) & 4,100 ppm (artificial urine) to an average of 50 ppm. These values are well below the standard for drinking water set by the World Health Organization (500 ppm), indicating that the prototype worked sufficiently to remove the contaminants in the test solutions.

In each 20 minute test, the prototyped required 0.2 kW.h of energy on average to produce 50 mL of clean, distilled water. Electricity consumption could be significantly decreased with an automatic power regulator to monitor the boiling chamber temperature; once the chamber neared 100°C, the power routed to the chamber would

temporarily decrease until the chamber temperature dropped below a threshold.

To power the distillation prototype, a 12V car battery with a power supply of 90 Ah could be connected to a low-cost, trickle-charging 12V solar panel. With this setup, the prototype, proof-of-concept distillation apparatus could be powered for approximately two hours. The electrical improvements described above could extend the operating range to nearly a full day, potentially making the apparatus sustainable for a small family.

To significantly improve the efficiency of the device while maintaining the portability and low cost, an insulated system could be created with vacuum-insulated stainless steel with welded edges. The original design could be implemented as well with a low-cost air compression mechanism. The cost of the prototype could be significantly lower through economies of scale, and the apparatus could be constrained in a structured and durable container for ease of use.