Electric bicycles are increasingly popular, but they’re expensive. This new invention from French start-up Rool’in, on the other hand, lets you convert almost any bike into an electric one simply by changing a wheel! It’s equipped with photovoltaic cells that’ll provide enough electricity to power you along for up to 30km, while an accompanying smartphone lets you choose your ’assistance level’ and provides data on distance travelled, average speed and so on.
