Sort of still on topic
World First: Hybrid-Drive Caravan System
GOING HYBRID
In essence, the technology – which is not yet commercially available – comprises special motors on each wheel that ‘drive’ the caravan, offsetting the ‘dead weight’ of the van so that the load in lateral acceleration is reduced or, in some cases, mitigated completely.
The motors are powered by an onboard 16kW/h battery, which is charged by the energy that is normally lost in braking. This battery can also be charged off the tow vehicle via a DC-DC charger, as well as solar on the van.