In June, Baylis plans to walk for 100 miles across the Namibian desert in Africa and to make a phone call on a cellular mobile phone to U.K. Prime Minister Tony Blair during the walk. There are apparently one or two GSM basestations on the periphery of the desert.

Before he begins his trek, Baylis' shoes are to be fitted with a piezoelectric transducer system developed by the Defense Evaluation Research Agency (DERA), an agency of the U.K. Ministry of Defense.

DERA claims its system yields more electrical energy through walking than has previously been available with solid-state devices.

The ability to generate electrical energy by walking has already been established, and has been employed by sports shoe companies who have installed blinking light emitting diodes in their footwear. However, the power consumption of an LED is a fraction of what's required for a mobile phone.

"The Electric Shoe Co. paid for this so I am not sure how much we can say in terms of the efficiency or the amount of energy recovered per step," said Steve Mahon, technical leader at DERA. It would be necessary to walk for many miles to completely charge a mobile phone battery, Mahon said, but through DERA's work walking has now become a useful additional energy source, he said.

The technology works through the pressure and flexing action on piezoelectric transducers in the heel of each shoe, which generates electricity. The Electric Shoe Co. has been formed to develop this new technology and its potential applications.

"We only worked on this project for two or three months, but DERA has studied piezoelectricity for many years and that is the reason why we have been successful," Mahon said. "The alternative technologies — mechanical or hydraulic — are too bulky to be put inside shoes."

Development of the charging system "required a team of experts that combined advanced materials knowledge with mechanical and electrical engineering expertise," Mahon said. "The innovative solution now makes charging a battery through walking feasible. This energy can be used to power anything which needs a similar output, for example, torch flashlight batteries and Global Positioning Systems."