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Divyasri Kothapalli’s project uses a Fresnel lens to concentrate sunlight, boil contaminated water, and condense vapor into clean water, in a low-cost solution recognized at the Stockholm Junior Water Prize and aimed at rural communities without reliable access to energy.
A water purification system powered solely by sunlight led a UK student to receive the People’s Choice Award at the Stockholm Junior Water Prize, an international competition aimed at student projects created to tackle major water challenges.
At the heart of the proposal is a Fresnel lens, used to concentrate solar radiation on a metal container, boil contaminated water, and conduct the vapor through silicone tubes until it condenses into clean water.
Developed by Divyasri Kothapalli, the project was presented under the name Sun-based water distillation system and proposes a low-cost solar distiller for rural communities and off-grid locations.
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According to the Stockholm Water Foundation, the solution aims to improve access to drinking water without pumps, chemicals, or energy connection, using a known physical process and simple materials to transform solar heat into purification.
Solar distillation transforms contaminated water into clean water
The logic of the equipment is based on a known physical principle: when heated to form vapor, water separates from impurities present in the original liquid, as these residues do not accompany evaporation in the same way.
After leaving the heated container, the vapor passes through a food-grade tube, cools during the journey, and returns to a liquid state, allowing the distilled water to be collected in another reservoir.
The project’s differential appears in the way heat is obtained, as the student replaced stove, electricity, or fuels with a lens capable of concentrating sunlight on a metal pan.
Thinner and lighter than conventional thick lenses, the Fresnel lens directs radiation to a smaller area and increases the intensity of heat at the chosen point to heat the water.
Fresnel lens concentrates heat without using electricity
Designed for rural areas and off-grid communities, a term used for locations without regular access to the power grid, the system aims to operate in contexts where traditional water treatment methods can be expensive or difficult to maintain.
In these regions, equipment that relies on constant energy, frequent material replacement, or complex infrastructure tends to encounter practical barriers, especially when the available water is not safe for direct consumption.
The proposal was also associated with the challenge of expanding access to clean water without increasing carbon emissions, as the operation described by the organization relies on sunlight during the purification process.
By combining simple materials, renewable energy, and condensation, the project transforms a known physical mechanism into an experimental alternative aimed at places where sanitation, electricity, and equipment transportation represent concrete obstacles.
The structure presented by Kothapalli uses a metal pot as a heating chamber, a Fresnel lens to concentrate light, food-grade silicone tubes to transport steam, and a container to collect the condensed water.
Due to its reliance on recognizable components, the idea is suited to contexts where complex sanitation solutions can be difficult to install, operate, or maintain continuously in isolated communities.
Tests evaluated light, climate, and water volume
In the tests described by the Stockholm Water Foundation, the student conducted three experiments with variables such as initial water volume, light intensity, and natural climate conditions, elements directly linked to the performance of any solar system.
Even in moderate climates, such as the United Kingdom, the system showed consistent results, a relevant point for a technology often associated only with regions of intense sunlight or very dry environments.
The research originated from a practical question: transforming an available heat source, sunlight, into an accessible purification method for places where water exists but is not safe for consumption.
Through evaporation and condensation, solar distillation seeks to separate water from undesirable substances without requiring industrial treatment infrastructure, which increases interest in compact and low-cost solutions.
Project won popular vote in world young scientists award
International recognition came at the Stockholm Junior Water Prize, a competition aimed at students aged 15 to 20 who develop projects related to major water challenges in different areas of science and technology.
In the edition in which Kothapalli participated, national finalists from various countries presented research evaluated in an environment dedicated to solutions for water, climate, and infrastructure problems.
The student received the People’s Choice Award, a category defined by global public vote, for the solar distillation project presented by the United Kingdom at the international competition organized by the Stockholm Water Foundation.
This result placed a seemingly simple solution alongside student research of international scope, highlighting a proposal that combines clean water, solar energy, and accessible materials in a single experimental system.
The relevance of the idea grows because the problem faced is not limited to a specific region, as rural communities, coastal areas, isolated locations, and regions with poor infrastructure may deal with water unsuitable for consumption.
In such situations, the critical step is not just finding a water source, but making it safe in a viable way, especially where electricity and traditional equipment cannot be taken for granted.
Potable water in areas without an electrical grid
In Kothapalli’s project, solar energy replaces equipment that would require an electrical grid or fuels, while the lens concentrates light on the container, heats the water, generates steam, and allows the collection of liquid after condensation.
This sequence makes the process visually easy to understand and helps explain why school inventions based on simple physical principles often attract attention when addressing concrete environmental problems.
Common objects also help bring the research closer to everyday life, as a pot, tube, lens, and container form an experimental system capable of demonstrating how science can reorganize simple materials to meet basic needs.
In award-winning youth projects, this type of innovation frequently appears precisely because it does not depend solely on sophisticated equipment, but on the careful application of scientific knowledge to real and recognizable problems.
According to the Stockholm Water Foundation, the work showed consistent production under different test conditions, with variables such as light intensity and natural climate evaluated during the experiments conducted by the student.
This detail reinforces the technical interest of the project, as solar solutions need to demonstrate performance outside of fully controlled environments, where changes in brightness and temperature can affect the final result.
The clean water obtained by condensation arises from a simple but organized chain: concentrated solar radiation generates heating, heating produces steam, steam moves through the tube, and cooling allows collection.
By receiving the popular vote in an international award, Kothapalli’s system gained visibility for the clarity of the problem it tries to tackle: contaminated water in places where electricity cannot be taken for granted.
What is more surprising in an invention like this: the technology used or the fact that it starts from such simple materials?
