Hydraulic Hybrids for Retrofit Applications

Hydraulic hybrids utilize hydraulic hardware to augment the conventional engine of a vehicle to reduce fuel consumption by recovering energy normally wasted when a vehicle is braking. This is similar to what is done with electric hybrids, except that hydraulic hybrids have the ability to store and release much larger amounts of power than most electric hybrids. This results in hydraulic hybrids having the capability to save larger amounts of fuel than electric hybrids when used on vehicles that undergo repeated stop/start operation. As hydraulic hybrids favor applications with high dynamic driving cycles (i.e., frequent start and stop cycles) they are being designed for use in commercial refuse trucks, city buses, and delivery vehicles.

When a vehicle equipped with a hydraulic hybrid needs to stop the energy can be recovered by using the pump to pressurize fluid which can be stored in the accumulator. This regenerative braking not only recovers the energy, it dramatically reduces the brake wear. When the vehicle needs to accelerate from a stop, that high pressure fluid can be used to power the pump and accelerate the vehicle. This saves fuel and reduces emissions. The remainder of the time the hydraulic hybrid system is not used.

Because of the large fuel savings 15-30%, and the dramatic reduction in brake wear the systesm can have payback periods between 2 and 3 years.

Czero has partnered with the Colorado State University to develop a hydraulic hybrid retrofit kit to upgrade existing vehicles with this fuel savings technology. The Czero/CSU team has their second prototype demonstration vehicle up and running. The team is focusing on commercializing the product for domestic markets, but aims to take the technology to interntaional markets at a later date.