Ideas: Hybrid energy storage for electric vehicles

I would like to see electric cars adopt hybrid energy storage / generation systems. An advanced controller would direct electricity to and from each system based on which is considered best at handling the current situation. If one has failed, it would simply be cut out of usage. It might include batteries, a generator, capacitors, compressed air systems, etc. A system like this would:

  • allow for characteristics that any one system doesn’t provide
  • provide an alternative / backup for if any one system fails / degrades
  • retain the simple, low maintenance drive system that an electric vehicle has

Vehicles, especially larger ones, may have the ability to swap in different standardized modules to better handle different drive situations or simply to replace a failed module.

Options for storage types that could be included in such a system are:

  • lithium or other advanced technology batteries
  • “super” capacitors
  • compressed air systems
  • combustion fuel generators

The current standard, advanced tech batteries can store a lot of energy fairly densely, and are straightforward to add to vehicles. They last quite a while in car life terms, but will eventually degrade, and are expensive to replace. They have a limited charge rate and faster charging may reduce lifespan. They don’t work as efficiently in extreme temperatures. Their production requires minerals that are in limited supply and will likely become more limited. They don’t currently have a good end of life situation, though that may change.

Super-capacitors and compressed air systems will likely be able to more rapidly charge and discharge than batteries. They will likely be more robust and last longer than batteries. They could be used to take some initial charge at charging stations and from regenerative braking, especially when the batteries are cold. Moving 20-30 miles of the vehicle’s overall capacity to these could provide enough to handle a normal commute for some when the batteries become too degraded, or at least help get back to a charger if they unexpectedly fail.

Current hybrid cars use a hybrid drive system, with an electric motor and combustion engine both providing power to the wheels. This results in a vehicle that requires more potential maintenance than either type of vehicle alone. If either system fails, it is unclear what would happend, but I suspect they won’t run at all or won’t run well. They require convential vehicle sized engines. They require transmissions that can fail, unlike electric vehicles (1 speed transmissions are unlikely to fail). They require normal vehicle exhaust systems that rust. They require normal vehicle oil changes.

Having a generator that just produces electricity for direct consumption or charging would allow for the high energy density of combustion fuels to extend range without most of the normal drive-train engine downfalls. A smaller engine could be used with a smaller exhaust system and no to-the-wheel transmission. It could run at maximum efficiency whenever it is running. And if it fails or needs some maintenance, it can just be turned off until that can be completed.

As electric vehicle technology improves, I would like to see this type of system implemented to improve energy storage characteristics and allay some concerns of problems and expenses associated with this type of otherwise low maintenance vehicle.