Around 2.2 billion people lack access to safe drinking water. Most solutions focus on infrastructure: wells, pipes, treatment plants. A flat solar device from Sweden has shown for fifteen years that another way exists. The Solvatten system uses sunlight to make dirty water drinkable in hours, without electricity, without fire, without chemicals. Over 800,000 people in 40 countries now use the device, and in 2025 the program scaled significantly in Kenya.
How Solvatten Works
The device was developed by Swedish inventor Petra Wadström and has remained simple since: a flat, dark plastic container in briefcase form holds 10 liters of water. On sunny days the water heats above 55 degrees Celsius, killing most pathogens; simultaneously the water passes through a UV membrane. A sensor button shows green once cleaning is complete. Two containers per unit produce 20 to 30 liters of clean water daily according to manufacturer specifications.
This sounds simple because it is simple. That's precisely what makes it more robust than systems requiring electricity, spare parts, or trained technicians. In areas without power supply, that's not a convenience, it's decisive for actual use.
What This Means for Health and Climate
According to the WHO, roughly 1.4 million people die annually from diarrheal illnesses caused by contaminated water. The lion's share affects children under five in countries without reliable water supply. Solvatten specifically fights cholera, dysentery, and other diarrheal diseases. The project received UNFCCC designation as a Lighthouse Activity, a label requiring third-party verified effectiveness evidence.
The climate aspect is direct: in many Sub-Saharan Africa households, water is boiled daily over open fires. This burns charcoal or kerosene, producing CO2 and often indoor air pollutants. A Solvatten device eliminates this need. The project generated CO2 emission credits for its Kenya programs through UN mechanisms, enabling independent verification of climate impact.
In 2025, the NextEnergy Foundation and Kenyan organization CANCO expanded in the Taita-Taveta region: the number of distributed Solvatten units rose from 214 to 792 according to Solvatten. The expansion followed needs assessment showing many households already knew the device and actively sought it.
LifeStraw, Biosand Filters, and SODIS: What These Solutions Teach
Solvatten is not the only simple water technology to achieve millions-scale distribution in developing countries.
LifeStraw, developed in 2005 by Vestergaard, filters water through a hollow-fiber membrane, removing bacteria, parasites, and microplastics. Over 50 million people in 64 countries now use it, primarily after natural disasters and in refugee camps. Difference from Solvatten: LifeStraw purifies but doesn't heat. Viruses smaller than membrane pores pass through unimpeded; against cholera viruses it offers only limited effectiveness.
Biosand filters, standardized by Canadian organization CAWST in the 1990s, use sand and gravel for filtering. Over one million such concrete containers have since been built in more than 70 countries. They're cheap (around 30 dollars) and durable (ten to twenty years), but require fixed installation and don't suit mobile use.
SODIS, solar disinfection of water in clear PET bottles, is WHO-recommended and has reached millions since the 1990s. SODIS costs nothing but offers no temperature control. On cloudy days uncertainty remains whether UV exposure was sufficient.
The pattern behind these successes: technologies using local resources like sunlight or sand without external inputs like electricity or chemicals have the best scaling chances. Solvatten combines heat and UV, making it more broadly effective than any single alternative.
Who Scales Next: The SDG-6 Gap in South Asia
According to WHO and UNICEF, around 2.2 billion people still lacked safe drinking water access in 2022. The UN set the goal in the Sustainable Development Goals (SDG 6) to ensure clean water for all by 2030. WHO/UNICEF monitoring program JMP estimates the current pace falls short for this goal; realistically 2050 is more likely.
800,000 people from 2.2 billion represents 0.036 percent. This contradicts nothing about the approach, it benchmarks the remaining task. Solvatten has active partnerships in Kenya, Uganda, Ethiopia, Tanzania, and India according to its own statements. Dense South Asian regions emerge as the next major scaling target, with Bangladesh and its roughly 40 million people without safe drinking water identified as priority.
What slows international expansion: the device costs 50 to 80 dollars at sale, unaffordable without subsidy for households earning one to two dollars daily. Many development programs also prefer infrastructure investments like wells and pipes over distributed individual devices because infrastructure can more easily be handed to communities. The UNFCCC Lighthouse designation eases access to international climate funds and could help close this gap.