Hybrid Types

Hybrid Electric Vehicle

A hybrid electric vehicle (HEV) is a vehicle which combines a conventional propulsion system with an on-board rechargeable energy storage system (RESS) to achieve better fuel economy than a conventional vehicle without being hampered by range from a charging unit like a battery electric vehicle, which uses batteries charged by an external source. The different propulsion power systems may have common subsystems or components.

Regular HEVs most commonly use an internal combustion engine (ICE) and electric batteries to power electric motors. Modern mass produced HEVs prolong the charge on their batteries by capturing kinetic energy via regenerative braking, and some HEVs can use the combustion engine to generate electricity by spinning an electrical generator (often a motor-generator) to either recharge the battery or directly feed power to an electric motor that drives the vehicle. Many HEVs reduce idle emissions by shutting down the ICE at idle and restarting it when needed. An HEV's engine is smaller and may be run at various speeds, providing more efficiency. [wikipedia.org]. The Prius is an HEV

An HEV gets all it's energy from petrol. All Prius sold in South Africa are HEVs

Plugin Hybrid Electric vehicle

A plug-in hybrid electric vehicle (PHEV) is a hybrid vehicle with batteries that can be recharged by connecting a plug to an electric power source. It shares the characteristics of both conventional hybrid electric vehicles and battery electric vehicles, having an internal combustion engine and batteries for power. Most PHEVs on the road today are passenger cars, but there are also PHEV versions of commercial passenger vans, utility trucks, school buses, motorcycles, scooters, and military vehicles. PHEVs are sometimes called grid-connected hybrids, gas-optional hybrids, or GO-HEVs. [wikipedia.org] According to the US Department of Transportation 80% of people drive 80km per day or less. This means that a PHEV with an all electric range of 80km will eliminate emissions from 80% of cars. Not bad. The cool thing is that when you do want to take that long trip, your car will run electric for the first 80km then revert to a standard HEV after that with reduced fuel consumption.

Hymotion in the US is taking deposits on PHEV upgrades for the 2004-2008 model Prius. Cost, about R80 000! This is bound to come down though. The upgrade will allow your Prius to achieve up to 2.5l/100 km by simply recharging at home. It is now cheaper, per kilometre, to use electricity to power a vehicle than it is to use petrol. See my post.

Video outlining the Plugin version of the Prius based on the 2010 model. Available in the US from next year for evaluation

Mild Hybrid

 Engine stop icon of the BMW 1 series manual diesel

Mild hybrids are essentially conventional vehicles with oversized starter motors, allowing the engine to be turned off whenever the car is coasting, braking, or stopped, yet restart quickly and cleanly. Accessories can continue to run on electrical power while the engine is off. The larger motor is used to spin the engine up to operating rpm speeds before injecting any fuel.

Many people do not consider these to be hybrids at all since they do not have hybrid drivetrains (there is no electric motor to drive the vehicle), they don´t have battery storage and do not achieve the fuel economy of full hybrid models. A major example is the 2005 Chevrolet Silverado Hybrid, a full-size pickup truck. Chevrolet was able to get a 10% improvement on the Silverado's fuel efficiency by shutting down and restarting the engine on demand. Mild hybrids often use 48 volt systems to supply the power needed for the startup motor, as well as to compensate for the increasing number of electronic accessories on modern vehicles. [wikipedia.org]

Examples : BMW EfficientDynamics available on 1, 3 and 5-series

Hydraulic Hybrid

Instead of storing excess energy in batteries, it is stored in a hydraulic cylinder. A device is available as a retrofit for existing rear-wheel drive vehicles where a hydraulic pump connects to the drive shaft. This system works well, but may be a challenge to fit to smaller vehicles.