It is a sunny day, and the children from Birley Community College are learning about torque, friction and gear ratios. They are laughing uncontrollably: "It's working!" exclaim several of the Sheffield children as they step outside and their creations spin into life.
"It just goes!" says 11-year-old Katie Blackmore. Birley's design and technology teacher Giles Grover is used to the reaction of his pupils when they take their solar-powered cars outside for the first time.
After a lesson of careful construction, when they step outside and put their whirring cars on the ground the excitement is infectious. "We had a training day for teachers, and it was just the same," Giles says. "They loved it. They were saying 'Oh look! Mine goes up the grass!'"
Building a model car to demonstrate the effect of different wheels and gears is nothing new, but replacing the usual batteries with what looks and feels like a piece of laminated cardboard makes the project that bit more exciting, according to David Garlovksy, director of the Schools and Homes Energy Education Project.
"The solar cells you usually get in schools tend to be cheap seconds and might power a buzzer or a tiny fan," he says. "But the ones we use will run a clock, a car, a boat or a radio."
The Schools and Homes Energy Education Project provides a range of ready-made experiments and construction kits to demonstrate the possibilities of renewable energy, including solar, water and wind power.
David says the aim is to develop projects for school that show renewable energy can be applied to the British climate. The solar panels he uses are designed to work in all kinds of weather, "even drizzle", he says.
The car kits use recycled materials as much as possible to help drive home the environmental message and keep costs down - old Blockbuster membership cards cut in two as motor housings, for example, and plastic straws for axles. The kits also include templates for body shells, which can be made from cereal packets.
Three standard car kits are available at around pound;19 to pound;23 each, and an advanced kit with more elaborate gears costs around pound;30.
A day workshop with staff from the Schools and Homes Energy Education Project costs from pound;300 to pound;500, depending on location.
"Using solar cells makes the lesson more exciting to children, because it's new to them," says David Garlovksy. "Here's a piece of what looks like coloured cardboard, and then they go outside and it produces electricity and it's not a fan twirling, it's not a buzzer, it's something that's moving.
Birley Community College used their solar cars in KS3 design and technology projects, covering photovoltaic energy, gears, friction, ratios and design and construction of solid objects. Later in the year, the school is planning a solar-car transition project with Birley's four feeder primaries. "When you take the cars out it's like working magic with the children," says Giles Grover.
"They laugh and the cars keep going and going. The Year 6s would love it.
Magic," he says, just as excited as the 11-year olds scampering after their cars in the sunny playground.
Schools and Homes Energy Education Project: www.pluggingintothesun.org.uk
Tel: 0114 249 9459 SunDay www.brookes.ac.ukotheruk-isessunday