A few degrees can make a big differencewhen it comes to food storage.Foods can go bad if they get too warm.But for many of the world's poor,finding a good way to keep food cool is difficult.Refrigerators are costly and they need electricity.Yet spoiled food not only creates health risksbut also economic losses.Farmers lose moneywhen they have to throw away productsthat they cannot sell quickly.But in nineteen ninety-five a teacher in northern Nigerianamed Mohammed Bah Abba found a solution.He developed the "Pot-in-Pot Preservation/Cooling System."It uses two round containers made of clay.A smaller pot is placed inside a larger one.The space between the two pots is filled with wet sand.The inner pot can be filled with fruit, vegetables or drinks.A wet cloth covers the whole cooling system.Food stored in the smaller pot is kept from spoilingthrough a simple evaporation process.Water in the sand between the two pots evaporatesthrough the surface of the larger pot,where drier outside air is moving.The evaporation process creates a dropin temperature of several degrees.This cools the inner potand helps keep food safe from harmful bacteria.Some foods can be kept fresh this way for several weeks.People throughout Nigeria began using the invention.And it became popular with farmersin other African countries.Mohammed Bah Abba personally financedthe first five thousand pot-in-pot systemsfor his own community and five villages nearby.In two thousand, the Rolex Watch Company of Switzerlandhonored him with the Rolex Award for Enterprise.This award recognizes people trying to develop projects aimed at improving human knowledge and well-being.A committee considers projects in science and medicine,technology, exploration and discovery,the environment and cultural history.Winners receive financial assistance to help developand extend their projects.The awards are given every two years.The next awards will be presented in late two thousand twelve.Last year, Rolex launched the Young Laureates Programfor the younger generation.And that's the VOA Special English Technology Report,written by Jill Moss.Transcripts, MP3s and podcasts of our reports are at 51voa.com.We're also on Facebook and Twitter at VOA Learning English.