Why don't most consumer vehicles use kinetic energy recovery systems?

Question

I know that Formula One and some sports cars have KERS systems to recover kinetic energy, but is there an expense/practicality barrier to installing them in consumer vehicles? As the technology clearly serves efficiency purposes beyond just providing extra horsepower, and as KERS can capture energy electrically or mechanically, it seems that it would be a useful step towards increased consumer vehicle efficiency.

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Note: I recognize that there's a significant cost associated with thermoelectric capture, and that this suggested duplicate raises the concern of how it's impractical to slow heat dissipation. However, if we limit the energy capture to brakes (typically cooled by natural convection and therefore not subject to any air/liquid cooling), could we see a more practical energy capture solution than trying to capture kinetic energy straight from an internal combustion engine?

Answer 1

It is used - check out buses / coaches but size / weight / cost tend to preclude it for cars - also the centrifugal forces can cause catastrophic failure so the enclosing drum adds weight as well.

After a quick search, an interesting paper shows that it could be applied to cars at a cost of approx $2000 - for a possible fuel saving of 35% - given how the bean-counters make adjustments to cars in the cents range the chances of it becoming mainstream are limited. Unless, of course, the Government legislate it in - chances of that with all the lobbyists....

https://www.google.ch/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&cad=rja&uact=8&ved=0ahUKEwi8tYfj3u_WAhWE7RQKHRr3A2oQFghaMAc&url=http%3A%2F%2Fwww.mdpi.com%2F1996-1073%2F8%2F10%2F10636%2Fpdf&usg=AOvVaw3rFfUNMeDuvzwcLZSogR28

Answer 2

Actually, a lot of consumer cars do use kinetic energy recovery. Every hybrid and electric car that I know of does this, and there are significant numbers of hybrids and electric cars out there now.

Since these cars already have a electric motor connected to the wheels, it only takes a little addition to the control electrics to run the motor as a generator when you want to slow down. The cost of the additional electronics is minimal compared to the cost of the motor and the electrical system as a whole, so this is a no-brainer in most cases.

The same system is used to charge the battery when going down a hill.

My Honda Civic hybrid works this way, for example. Stepping on the brake lightly while moving first runs the motor in reverse. I can see the battery charge/discharge indicator going to charge. Stepping harder on the brake causes more charging, and therefore more drag. Eventually the friction brakes are also engaged. This is all done quite smoothly and seamlessly.