A hybrid vehicle is a vehicle that uses two or more discrete power sources to propel the vehicle. Common power sources include:
• On-board or out-board rechargeable energy storage system (RESS) and a fueled power source (internal combustion engine or fuel cell)
• Air engine and internal combustion engines
• Human powered bicycle with electric motor or gas engine assist
• Human-powered or sail boat with electric power
The term most frequently refers to Hybrid-electric vehicle (HEV) which comprises internal combustion engines and electric motors.
Early hybrid systems are being examined for trucks and other heavy highway vehicles with a few operational trucks and buses initial to come into use. The chief barrier seem to be smaller fleet sizes and the extra costs of a hybrid system are yet remunerated for by fuel savings, but with the price of oil set to persist on its upward trend, the tipping point might be reached by the end of 2008. Advances in technology and lesser battery cost and higher capacity etc. urbanized in the hybrid car industry are already filtering into truck use as Toyota, Ford, GM and others initiate hybrid pickups and SUVs. Kenworth Truck Company lately introduced a hybrid-electric truck, called the Kenworth T270 Class 6 that for city usage appear to be competitive. FedEx and others are preparatory to invest in hybrid delivery type vehicles—mainly for city use where hybrid technology may pay off first. The U.S. military is inspecting hybrid Humvees and other vehicles.
When the term hybrid vehicle is used, it normally refers to a Hybrid electric vehicle. These cover such vehicles as the AHS2 (Chevrolet Tahoe, GMC Yukon, Chevrolet Silverado, Cadillac Escalade, and the Saturn Vue), Toyota Prius, Toyota Camry Hybrid, Ford Escape Hybrid, Toyota Highlander Hybrid, Honda Insight, Honda Civic Hybrid and others. A petroleum-electric hybrid normally uses internal combustion engines and electric batteries to control electric motors. There are loads of types of petroleum-electric hybrid drivetrains, from Full hybrid to Mild hybrid, which proffer varying merits and demerits.
While liquid fuel/electric hybrids in the late 1800s, the braking regenerative hybrid was invented by David Arthurs, an electrical engineer from Springdale, Arkansas in 1978-79. His home-converted Opel GT was reported to get as much as 75MPG and plans are still sold to this novel design, and the “Mother Earth News” customized version on their website.
Hybrid fuel (dual mode)
Additionally, vehicles that use two or more different devices for propulsion, some also deem vehicles that use discrete energy sources or input types (“fuels”) using the same engine to be hybrids, even though to avoid confusion with hybrids as described above and to use in the approved manner the terms, these are perhaps more suitably described as dual mode vehicles:
• A few electric trolleybuses can switch between an on board diesel engine and
Overhead electrical power depending on circumstances (see dual mode bus). In principle, this could be pooled with a battery subsystem to create a true plug-in hybrid trolleybus, though as of 2006, no such design seems to have been announced.
• Flexible-fuel vehicles can be able to use an assortment of input fuels (petroleum and biofuels) in one tank — characteristically gasoline and bioethanol or biobutanol, though diesel-biodiesel vehicles would also meet the criteria.
• Dual mode: Liquified petroleum gas and natural gas are diverse from petroleum or diesel and cannot be used in the identical tanks, so it would be unfeasible to build an (LPG or NG) flexible fuel system. As an alternative vehicles are built with two, parallel, fuel systems feeding one engine. While the replicated tanks cost space in some applications, the augmented range and flexibility where (LPG or NG) infrastructure is incomplete may be a noteworthy incentive to purchase.
• Few vehicles have been modified to use another fuel source if it is available, such as cars customized to run on autogas (LPG) and diesels customized to run on waste vegetable oil that has not been processed into biodiesel.
• Power-assist mechanisms for bicycles and additional human-powered vehicles are also integrated.
Fluid power hybrid
Hydraulic and pneumatic hybrid vehicles employ an engine to charge a pressure accumulator to drive the wheels through hydraulic or pneumatic (i.e. compressed air) drive units. The energy recovery rate is elevated and therefore the system is more efficient than battery charged hybrids, demonstrating a 60% to 70% increase in energy economy in EPA testing. Under tests performed by the EPA, a hydraulic hybrid Ford Expedition returned 32 mpg–U.S. (7.35 L/100 km / 38.4 mpg–imp) City, and 22 mpg–U.S. (10.69 L/100 km / 26.4 mpg–imp) highway
The most recent hybrid technology is the Plug-in Hybrid Electric Vehicle (PHEV). The PHEV is inclusive of a gasoline-electric hybrid whose battery pack (usually Li-ion) is upgraded to a superior capacity, which can be recharged by moreover a battery charger curved into the electrical grid or the gasoline engine (only if required). The car runs on battery power for the first 10 to 60 miles (16–100 km), with the gasoline engine on hand for faster speeding up, etc.
After the battery is almost discharged, the car reverts to the gasoline engine to recharge the battery and/or return the car to the charging station. This may get around the fundamental barrier of battery range that has made nearly all pure electric cars impractical. Fuel rates, in principle, may be as low as 5 cents/mile. It’s not obvious yet whether converting an existing hybrid car will ever pay for itself in fuel savings.
The major problem is finding a good, cheap, high-energy battery pack—the equivalent problem that has plagued the unpolluted electric car. If everyone plugged into the function grid to charge up their car this would seem to be just displacing the gasoline/diesel combustion crisis to the trait coal powered electrical generating plant. But, if cars were recharged tardy at night this would allow the base load of the electrical system to be more capable with a much more even base load and electrical power can also be generated by clean wind, hydro, tide power, etc. while most travel is regarding 30 miles/day this may be the cleanest personal transportation system at present available.
There is a “cottage” conversion industry for owner- existing hybrids, and more than a few huge auto industry groups (GM, Toyota, Mercedes etc.) plus the US Department of Energy are investigating this system. No chief car company (as of late 2007) offers PHEVs yet. The characteristic “cottage” industry conversion car is the Toyota Prius (cost of conversion $5k-$40k), as it is a full hybrid with sufficient power in its electrical system to maintain distinctive city speeds.
Fuel consumption and emissions reductions
The hybrid vehicle characteristically achieves greater fuel economy and lower emissions than conventional internal combustion engine vehicles (ICEVs), ensuing in fewer emissions being generated. These savings are mainly achieved by four elements of a typical hybrid design:
– Recapturing energy generally wasted during braking etc. (regenerative braking) this is a mechanism that condenses vehicle speed by converting some of its kinetic energy into a further helpful form of energy, particularly in stop-and-go traffic.
– having important battery storage capacity to store and recycle recaptured energy;
– shutting down the gasoline or diesel engine in traffic stops or while coasting or other idle periods;
– civilizing aerodynamics; A box shaped car or truck has to put forth more force to move through the air causing added stress on the engine making it toil harder. Improving the shape and aerodynamics of a car is a fine way to help better the gas mileage and also get better handling at the same time.
– By means of low rolling resistance tires; (tires these days are made to give a fine, smooth ride but hardly ever is efficiency taken into consideration. These tires cause a great pact of drag, once again making the engine toil harder, intense more gas mileage. Hybrid cars use special tires that are more exaggerated than regular tires and stiffer, which decreases the drag by about half, humanizing fuel economy by mitigating stress of the engine.
– relying on mutually the gasoline (or diesel engine) and the electric motors for peak power requires ensuing in a smaller gasoline or diesel engine sized more for normal usage rather than peak power usage.
These features make a hybrid vehicle chiefly efficient for city traffic where there are recurrent stops, coasting and idling periods. Besides noise emissions are condensed, mainly at idling and low operating speeds, in similarity to conventional gasoline or diesel powered engine vehicles. For constant high speed highway use these features are much less helpful in reducing emissions.