You’d be surprised to know that Swiss engineers had developed a zero-emission electric bus back in the 1940s. The Gyrobus featured big spinning flywheel for the sake of storing energy as opposed to rechargeable batteries. They did so because they wanted to create something that was cleaner and quieter. A number of Swiss cities at the time of the advent of Gyrobus had trolley buses as public transport that were used on predetermined routes that used electricity for the sake of power.
Bjarne Storsand, the chief engineer of Maschinenfabrik Oerlikon, conceptualized Gyrobus in 1946. The Gyrobus was powered by using an electric motor, and the motor was provided electricity by a generator that relied on a huge spinning flywheel for storage of energy. The flywheel was spun by making use of three booms that had been mounted on the bus’s roof at charging stations.
The Gyrobus was fully charged once the flywheel achieved the maximum speed of 3,000 RPM. Once it had been fully charged, the bus could travel for about 6 km at speeds of around 50-60 kph. The flywheel measured in at 160 cm diameter and had a weight of 1.5 ton. It was installed in an airtight chamber that had been filled with hydrogen gas at reduced pressure, thus lowering resistance. If the flywheel was being charged after becoming fully exhausted; it took around 40 minutes. However, if additional energy was being added to the flywheel; it required only two to five minutes. Charging stations were installed to make sure that the flywheel onboard the Gyrobus never lost energy below a certain level, thus making sure that the bus was moving at a consistent speed.
The Gyrobus was utilized in limited quantities in various cities in Belgium, Switzerland, and in Belgian Congo. The system was eventually discarded owing to its high energy consumption and because of the risks of a big steel wheel rotating at dangerous speeds. You can still, however, find one Gyrobus at the Flemish Tram and Bus Museum in Antwerp.