SolMist

What it does

Purifies water using the sun’s heat and solar power, outperforming traditional solar stills. By separating the evaporation and condensation chambers, it creates ideal conditions for each process, making water production faster, more efficient, and sustainable.

Your inspiration

Growing up in Africa, I witnessed a daily struggle that many take for granted: access to clean drinking water. My community relied on purchasing water, a costly and unsustainable solution. After moving to the UK, I knew I wanted to use my knowledge to give back. While studying thermodynamics, I stumbled upon a powerful insight: water boils at a lower temperature under reduced pressure. Combine this with the intense African sun, and suddenly, the solution became clear. By optimising evaporation and condensation conditions, we could design a solar-powered water purification system that’s both efficient and accessible.

How it works

Evaporation Chamber Mist Generation: Water is atomised into fine mist droplets. Solar Heating: Transparent top + black aluminium sheets create a greenhouse effect. Insulated walls minimise heat loss. Piston Mechanism: Moves forward to push mist/steam, creating a partial vacuum behind it (lowers evaporation temp). Acts as a one-way valve (allows air intake on the return stroke but blocks forward leaks). Pressure release valves are used to maintain chambers to a set pressure by bringing closer to atmospheric pressure Hydrophobic Membrane: Blocks liquid mist but permits steam passage into the condensation chamber. Automated Gate Valve: Opens only during steam transfer to maintain the pressure differential. Condensation Chamber Cooling Design: Shaded by a reflective mirror to avoid solar heating. A copper layer with an air gap acts as a heat sink for rapid steam condensation. Freshwater Collection: Condensed water drips down from the mesh of nets for storage.

Design process

After exploring water purification methods, I discovered reverse osmosis and distillation and stumbled upon ultrasonic mistifiers. I considered using the mistifier to separate salt from water droplets by separating droplets with no salt from those with salt by means of a centrifuge or charge attractor, but research showed that the salt-free droplets were insufficient for reasonable water gain. Then I refocused on solar stills and realised they are inefficient because evaporation and condensation need different conditions, yet most systems combine both in one chamber. So, I designed 2 chambers, insulated from each other, to optimise each process. Using a mistifier increases the water surface area, speeding evaporation, and with the evaporation chamber at low pressure, while the condensation chamber is at high pressure. Initially, I planned modular cubes so you could change different materials for each side to experiment and play with them like in Minecraft, but switched to a single cylindrical block for better strength and flow efficiency. I think of my final design as a blueprint; further testing is required to finalise the design in practice, but in theory, everything is complete, just like those internal combustion engine videos.

How it is different

Most solar-powered purifiers suffer from slow speeds and inefficiency because they evaporate and condense water in the same environment, requiring large setups and prolonged exposure to heat. By separating evaporation and condensation into distinct environments, we unlock faster, more efficient purification in a compact, scalable device. Unlike traditional methods, we rapidly evaporate water at low pressure, then immediately condense it in a separate chamber, dramatically speeding up the process. A lightweight, low-energy piston system actively controls pressure, optimising evaporation without relying solely on solar heat (though solar can still power it). Small enough for household use, but easily scaled for larger applications, with no complex filters or high-maintenance parts. Highly sustainable due to solar power and no one-time use components

Future plans

I would like to build a small working model, then optimise the pressure and piston speed (variation) for maximum output for minimum energy. Improve the piston to remove rubbish and salts left after evaporation, and have the piston and gate powered mechanically by one motor. Afterwards, I would love to design a larger modular version for communities, adaptable to solar, waste heat, and mechanical power. Then give out multiple prototypes to test real-world usability to get feedback on design iterations.

Awards