Ahmedabad, January 3: ‘‘Abhi to petrol-diesel hai, par bees saal baad kya hoga?.” The question about depleting fuel sources raised by Std XI student Jaydeep Rakholia (16) prompted students of Brahmanand Vidyamandir in Chaparda village of Visawadar taluka in Junagadh to invent a solar bicycle that runs on 36 volt acid-lead battery for an hour.

This is one of the 380-odd projects on display at the science-maths exhibition being held at Science City. The projects concentrate on how to make use of non-conventional and non-polluting sources of energy like sun, water and air instead of the fast-depleting, conventional energy sources.

‘‘We must curb increasing levels of pollution. The depleting ozone layer is a cause of worry. By thinking of the future and devising ways of using non-conventional sources of energy, we are taking a step towards protecting our environment,’’ said Mehul Jethwa 17, another student of Brahmanand Vidyamandir.

Explaining how the solar bicycle works, project guide Baldania said, ‘‘The solar plate collects heat and transfers it to the battery. The battery converts heat into electrical energy for the DC motor that rotates the wheel.’’ He added, ‘‘The bicycle has certain limitations. It doesn’t have suspension. The motor is not powerful enough to carry more than one person. Currently, it runs on lead-acid dry battery, but needs nickel cadmium battery.’’

Students from 95 primary schools, 100 secondary schools, 88 higher secondary schools, 24 municipal corporation-run schools and 31 PTC schools have displayed their projects here.

The students have worked on themes like agriculture, health and solar energy, environment, mathematics and education technology.

Students of Sonpari Primary School in Palitana taluka took up the ‘safe city system’ project while students of Saraswati Mandir in Mendarda of Junagadh built the model of a special greenhouse.