Designed by Paula Denby, a graduate of the University of East London, the sill generates small amounts of electricity and channels it to a charging bay for mobile phones and MP3 players.

“In the Thames Gateway, architects of new buildings are trying to achieve a zero-carbon environment and lifestyles,” she said. “That inspired me to think how I could design low-energy products for the home. I wanted to design something affordable and easy to understand.” Several manufacturers have expressed an interest.