While a vehicle is plugged in and not in use, the utility could take advantage of the extra electrical storage capacity in the vehicle’s batteries to help meet peak electricity demand, provide grid support services or respond to power outages. PHEV owners could get “paid” by the utility for use of their vehicle’s energy if needed.
Vehicle manufactures are also developing ranger extenders for plug-in hybrid electric vehicles. With these systems, once the battery is exhausted, an internal combustion engine charges the battery after the electric-only range is exceeded. The vehicle will continue to operate with no change in performance until the battery can be plugged in and recharged.
Fuel cell electric vehicles: A fuel cell combines hydrogen fuel and oxygen to produce electricity used to power an electric motor that moves the vehicle. The only exhaust is water.
Researchers, using detailed computer simulation modeling, have shown that hydrogen-powered fuel cell electric vehicles (FCEVs) are superior to BEVs in terms of greenhouse gas reductions, range, refueling time and lifecycle cost.
FCEVs are more efficient than gasoline-powered vehicles as hydrogen contains three times more energy per weight than gasoline does.
However, there are several key stumbling blocks with fuel cell electric vehicles. One is onboard hydrogen storage. Hydrogen gas contains only a third of the energy per volume gasoline does, making it difficult to store enough hydrogen to go as far as a gasoline vehicle on a full tank – at least within size, weight and cost constraints.
Also, it is critically important to store hydrogen carefully. Hydrogen is explosive when ignited. Many people think of the 1937 Hindenburg disaster when they thing about hydrogen.
Another challenge is fuel cell durability, reliability and cost. Fuel cell systems are not yet as durable as internal combustion engines and do not perform as well in extreme environments, such as in sub-freezing temperatures. These systems always contain water, which can freeze at low temperatures and must reach a certain temperature to attain full performance.
One other drawback is that new facilities and systems will be required for producing, distributing and dispensing hydrogen for FCEVs. In addition, if hydrogen is not produced by renewable energy sources, the well-to-wheel balance is not good.
Typically, electric vehicles use rechargeable batteries as a source of electrical energy. These batteries do not store electrical energy in the same sense that a fuel tank stores liquid fuel. Instead, rechargeable batteries are essentially self-contained electrochemical reactors in which the by-products are retained within the battery housing. During recharge, these by-products are reconstituted into their original state where they are ready for another electrochemical reaction cycle.
Battery life is measured by overall age and cycle stability. Overall age is the number of years a battery can be expected to remain useful. Cycle stability is the number of times a battery can be fully charged and discharged before being degraded to 80 percent of its original capacity at full charge.
The fact is, major technical breakthroughs are needed in rechargeable battery chemistries to make EVs economically viable.
Researchers are working on improved battery technologies. New batteries are being developed to extend the range of electric vehicles and lengthen battery life so that the need to replace batteries during the life of the vehicle may be eliminated.
Under development is integration supercapacitors and ultracapacitors with batteries to improve electric vehicle performances, battery life and energy economy. These capacitors have a high energy density and can quickly store large amounts of electricity and discharge the electricity on demand to batteries or electric motors which can propel vehicles.
The most promising rechargeable batteries for EVs are lithium-ion based batteries. These types of batteries have a higher energy density and power density than most other types of rechargeable batteries. They can store four or five times as much energy of a lead/acid battery.
Lithium-ion batteries also have a lower self discharge rate than other types of rechargeable batteries. This means that once they are charged, they will retain their charge for a longer time than other types of rechargeable batteries.