Modern festival-goers who dread ending up with a dead mobile phone battery after days stuck in a muddy field with no electric plug power points may now have a solution -- power boots。

Mobile phone company European Telco Orange has introduced a phone charging prototype -- a set of thermoelectric gumboots or Wellington boots with a 'power generating sole' that converts heat from the wearer's feet into electrical power to charge battery-powered hand-helds。

The boot was designed by Dave Pain, managing director at GotWind, a renewable energy company。

Pain said the boot uses the Seebeck effect, named after physicist Thomas Johann Seebeck, in which a circuit made of two dissimilar metals conducts electricity if the two places where they connect are held at different temperatures. "In the sole of the Wellington boot there's a thermocouple and if you apply heat to one side of the thermocouple and cold to the other side it generates an electrical charge," Pain said。

"That electrical charge we then pass through to a battery which you'll find in the heel of the boot for storage of the electrical power for later use to charge your mobile phone."

These thermocouples are connected electrically, forming an array of multiple thermocouples (thermopile). They are then sandwiched between two thin ceramic wafers。

When the heat from the foot is applied on the top side of the ceramic wafer and cold is applied on the opposite side, from the cold of the ground, electricity is generated。

After a full day's festivalfrolics music lovers can plug their phone into the power output at the top of the welly and use the energy generated throughout the day to charge their phone。

But the prototype boot does have one drawback. You need to walk for 12 hours in the boots to generate one hour's worth of charge。