Solar fridges could play a vital role in helping aid workers get life-saving vaccines to people in remote parts of developing countries, researchers have said.
Engineers have developed a prototype that could keep vaccines at the required temperature until they are needed for treatment.
Thousands of children in Third World countries die every day from diseases that are preventable by vaccination.
Researchers believe the technology could have a huge impact in countries where delivering humanitarian aid is challenged by fuel shortages and high temperatures, meaning vaccines often deteriorate before they arrive.
Tests show that the proposed system, designed at the University of Edinburgh and tested in collaboration with the Italian National Research Council's ITAE research institute, can produce up to 5kg of ice each day.
The fridge can store vaccines at between 2°C and 8°C for as long as three days, the target set by the World Health Organization.
The technology is also compliant with the requirements of the main humanitarian organisations in supporting aid operations in areas affected by catastrophic events.
The team at Edinburgh hope a new, more compact and market-attractive prototype can be developed as a result of their research.
Dr Giulio Santori, of the University of Edinburgh's School of Engineering, who is leading the project, said: "We are very pleased by the encouraging results obtained so far on the proof-of-concept prototype.
"We are now seeking to develop a first generation commercial version, which combines the solar thermal and adsorption-based technologies."