A hybrid vehicle is a vehicle that uses two or more distinct power sources to propel the vehicle. Power sources include:
An example of a typical "hybrid" is the new Canadian, Bombardier-built railroad engine called the AGC (Autorail à grande capacité, high-capacity railcar) which has dual mode (diesel and electric motors) and dual voltage capabilities (1500 and 25000 V) allowing it to be used on many different rail systems. The first operational prototype of a hybrid train engine with significant energy storage and energy regeneration capability has been introduced in Japan as the Kiha E200. It utilizes battery packs of lithium ion batteries mounted on the roof to store recovered energy. In the U.S., General Electric introduced a prototype railroad engine with their "Ecomagination" technology in 2007. They store energy in a large set of sodium nickel chloride (Na-NiCl2) batteries to capture and store energy normally dissipated during dynamic braking or coasting downhill. They expect at least a 10% reduction in fuel use with this system and are now spending about $2 billion/yr on hybrid research. Variants of typical diesel-electrical locomotives are like the Green Goat (GG) and Green Kid (GK) switching/yard engines built by Canada's Railpower Technologies. They utilize a large set of heavy duty long life (~10 yr) rechargeable lead acid (Pba) batteries and 1000 to 2000 HP electric motors as the primary motive sources and a new clean burning diesel generator (~160 Hp) for recharging the batteries that is used only as needed. No power or fuel are wasted for idling—typically 60–85% of the time for these type locomotives. Its unclear if dynamic braking (regenerative) power is recaptured for reuse; but in principle should be easily utilized. Since these engines typical need extra weight for traction purposes anyway the battery pack's weight is a negligible penalty. In addition the diesel generator and battery package are normally built on an existing "retired" "yard" locomotive's frame for significant additional cost savings. The existing motors and running gear are all rebuilt and reused. Diesel fuel savings of 40–60% and up to 80% pollution reductions are claimed over that of a "typical" older switching/yard engine. The same advantages that existing hybrid cars have for use with frequent starts and stops and idle periods apply to typical switching yard use. "Green Goats" locomotives have been purchased by Canadian Pacific Railway, BNSF Railway, Kansas City Southern Railway and Union Pacific Railroad among others.
Railpower Technologies Corp. engineers working with TSI Terminal Systems Inc. in Vancouver, British Columbia are testing a hybrid diesel electric power unit with battery storage for use in Rubber Tyred Gantry (RTG) cranes. RTG cranes are typically used for loading and unloading shipping containers onto trains or trucks in ports and container storage yards. The energy used to lift the containers can be partially regained when they are lowered. Diesel fuel and emission reductions of 50–70% are predicted by Railpower engineers. First systems are expected to be operational in 2007.
Early hybrid systems are being investigated for trucks and other heavy highway vehicles with some operational trucks and buses starting to come into use. The main obstacles seem to be smaller fleet sizes and the extra costs of a hybrid system are yet compensated for by fuel savings, but with the price of oil set to continue on its upward trend, the tipping point may be reached by the end of 2008. Advances in technology and lowered battery cost and higher capacity etc. developed in the hybrid car industry are already filtering into truck use as Toyota, Ford, GM and others introduce hybrid pickups and SUVs. Kenworth Truck Company recently introduced a hybrid-electric truck, called the Kenworth T270 Class 6 that for city usage seems to be competitive. FedEx and others are starting to invest in hybrid delivery type vehicles—particularly for city use where hybrid technology may pay off first. The U.S. military is investigating hybrid Humvees and other vehicles.
Ships with both mast-mounted sails and engines were an early form of hybrid vehicles. Newer hybrid ship-propulsion schemes include large towing kites manufactured by companies such as SkySails. Towing kites can fly at heights several times higher than the tallest ship masts, capturing stronger and steadier winds.
When the term hybrid vehicle is used, it most often refers to a Hybrid electric vehicle. These encompass 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 most commonly uses internal combustion engines (generally gasoline or Diesel engines, powered by a variety of fuels) and electric batteries to power electric motors. There are many types of petroleum-electric hybrid drivetrains, from Full hybrid to Mild hybrid, which offer varying advantages and disadvantages.
While liquid fuel/electric hybrids date back to 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 original design, and the "Mother Earth News" modified version on their website.
Given suitable infrastructure, permissions and vehicles, BEVs can be recharged while the user drives. The BEV establishes contact with an electrified rail, plate or overhead wires on the highway via an attached conducting wheel or other similar mechanism (see Conduit current collection). The BEV's batteries are recharged by this process—on the highway—and can then be used normally on other roads until the battery is discharged.
This provides the advantage, in principle, of virtually unrestricted highway range as long as you stay where you have BEV infrastructure access. Since many destinations are within 100 km of a major highway, this may reduce the need for expensive battery systems. Unfortunately private use of the existing electrical system is nearly universally prohibited.
The technology for such electrical infrastructure is old and, unfortunately outside of some cities, is not widely distributed (see Conduit current collection, trams, electric rail, trolleys, third rail). Updating the required electrical and infrastructure costs can be funded, in principle, by toll revenue, gasoline or other taxes.
UPS currently has two trucks in service with this technology.
While the system has faster and more efficient charge/discharge cycling and is cheaper than gaselectric hybrids, the accumulator size dictates total energy storage capacity and requires more space than a battery.
The latest hybrid technology is the Plug-in Hybrid Electric Vehicle (PHEV). The PHEV consists of a gasoline-electric hybrid whose battery pack (usually Li-ion) is upgraded to a larger capacity, which can be recharged by either a battery charger hooked 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 available for faster acceleration, etc. After the battery is nearly 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 obstacle of battery range that has made nearly all pure electric cars impractical. Fuel costs (ignoring conversion costs), in principle, may be as low as 5 cents/mile. It's not clear yet whether converting an existing hybrid car will ever pay for itself in fuel savings. The biggest problem is finding a good, cheap, high-energy battery pack—the same problem that has plagued the pure electric car. If everyone plugged into the utility grid to charge up their car this would seem to be merely displacing the gasoline/diesel combustion problem to the typical coal powered electrical generating plant. But, if cars were recharged late at night this would allow the base load of the electrical system to be more efficient with a much more even base load and electrical power can also be generated by clean wind, hydro, tide power, etc. Since most travel is about 30 miles/day this may be the cleanest personal transportation system presently available. There is a "cottage" conversion industry for owners of existing hybrids, and several large auto industry groups (GM, Toyota, Mercedes etc.) as well as the US Department of Energy are investigating this system. No major car company (as of late 2007) offers PHEVs yet. The typical "cottage" industry conversion car is the Toyota Prius (cost of conversion $5k-$40k), since it is a full hybrid with enough power in its electrical system to maintain typical city speeds.
The first type can propel itself using only the electric motor at very low speeds. The gasoline motor also has the ability to kick in and help out the electric engine when more power is needed, such as when passing or climbing a steep grade. The Toyota Prius and the Ford Escape Hybrid fall into this category.
When a car like the Toyota Prius accelerates from a standstill, the electric motor gets the vehicle rolling and continues to drive it up to around 25 mph before the gasoline engine automatically starts up. Under hard acceleration from a stop, the gas engine starts immediately to provide maximum power. The electric motor and the gas engine also work in tandem when driving conditions demand more power, such as while climbing a hill or passing other vehicles. Because the electric motor is used so much at low speeds, the Prius and Escape get better mileage in the city than they do on the highway.
The second type uses the electric motor only to assist the gasoline engine when it needs extra boost, again during brisk acceleration or when going up a hill. The Civic Hybrid and Honda Insight fall into the second category.
When a car like the Honda Insight and Civic Hybrid, the electric motor assists the gas engine only when driving conditions demand more power, such as during hard acceleration from a stop, while climbing a hill or passing other vehicles. As with normal, gas-powered cars, these hybrids get better fuel economy while cruising on the highway, as that is when the gas engine is least taxed.
These features make a hybrid vehicle particularly efficient for city traffic where there are frequent stops, coasting and idling periods. In addition noise emissions are reduced, particularly at idling and low operating speeds, in comparison to conventional gasoline or diesel powered engine vehicles. For continuous high speed highway use these features are much less useful in reducing emissions.
Though hybrid cars take in substantially less petroleum than conventional cars, there is still an issue regarding the environmental damage of the Hybrid car battery. Today most Hybrid car batteries are one of two types: (1) nickel metal hydride, or (2) lithium ion; both are regarded as more environmentally friendly than lead-based batteries (which constitute the bulk of car batteries today). "Jim Kliesch, author of the 'Green Book: The Environmental Guide to Cars and Trucks' told HybridCars.com, 'There are many types of batteries. Some are far more toxic than others. While batteries like lead acid or nickel cadmium are incredibly bad for the environment, the toxicity levels and environmental impact of nickel metal hydride batteries—the type currently used in hybrids—are much lower.'"
Though substantially less toxic than conventional car batteries, nickel-based batteries are known carcinogens, and can lead to a wide array of other health problems (little testing has been done to show the effects of nickel on people but other possible side effects may include: "xencephaly, everted viscera, short and twisted neck, short and twisted limbs, microphthalmia, hemorrhage, and reduced body size" ).
Although companies are funding research to use these safer less toxic batteries, the fact of the matter is lead is so cheap, and money always plays a factor when dealing with mass production of an item. According to a 2003 report entitled, "Getting the Lead Out," by Environmental Defense and the Ecology Center of Ann Arbor, Mich., an estimated 2.6 million metric tons of lead can be found in the batteries of vehicles on the road today. There's little argument that lead is extremely toxic. Scientific studies show that long-term exposure to even tiny amounts of lead can cause brain and kidney damage, hearing impairment, and learning problems in children. The auto industry uses over one million metric tons of lead every year, with 90% going to conventional lead-acid vehicle batteries. While lead recycling is a mature industry, it's impossible to rescue every car battery from the dump. More than 40,000 metric tons of lead are lost to landfills every year. According to the federal Toxic Release Inventory, another 70,000 metric tons are released in the lead mining and manufacturing process. [Jim Kliesch, author of the Green Book: The Environmental Guide to Cars and Trucks]
Nearly all the rare earth elements in the world come from China, and many analysts believe that an overall increase in Chinese electronics manufacturing will consume this entire supply by 2012. In addition, export quotas on Chinese Rare Earth exports have resulted in a generally shaky supply of those metals .
A few non-Chinese sources such as the advanced Hoidas Lake project in northern Canada as well as Mt Weld in Australia are currently under development; however it is not known if these sources will be developed before the shortage hits.