Hybrid Vehicles: You may Plug-in your Car!!!

Summary:  

To reduce the harmful transport effects on the environment, different options are available such as advanced vehicle technologies, alternative fuels and improved conventional fuel quality.

To reduce the harmful transport effects on the environment, different options are available such as advanced vehicle technologies, alternative fuels and improved conventional fuel quality.

Road transport is responsible for 17-18% of global CO2 emissions from fossil fuel combustion. Significant improvements in fuel usage efficiency are required to decrease greenhouse gas emissions from the transport sector.

Besides CO2 emissions, the transport sector is responsible for an estimated 70-90% of air pollution in urban areas – especially in developing countries where fuel quality, vehicle technology, and inspection and maintenance regimes are inadequate.

In summary, reducing vehicle emission and utilizing cleaner fuel are the main targets of the state of the art vehicles technology.

A new generation of vehicles that use electricity is one of the solutions. The presence of electric power is intended to achieve better fuel economy than a conventional vehicle, less Co2 emission and less population. The electric drive vehicles can be divided into three categories: hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and all-electric vehicles (EVs).

Hybrid Electric Vehicles

HEVs utilize two or more different power sources. The regular gasoline engine is combined with another electric motor.

The gasoline engine can run on conventional or alternative fuel and the electric motor uses energy stored in a battery.

The extra power provided by the electric motor allows for a smaller engine, resulting in better fuel economy without sacrificing performance. HEVs combine the benefits of high fuel economy and low emissions with the power of conventional vehicles.

HEVs do not require a plug to charge the battery; instead, they charge using regenerative braking and the internal comiliary power when idling.


Plug-in hybrid vehicles

Plug-in hybrid-electric vehicles have recently emerged as a promising alternative that uses electricity to displace a significant fraction of fleet petroleum consumption. A plug-in hybrid electric vehicle (PHEV) is a hybrid-electric vehicle (HEV) with the ability to recharge its electrochemical energy storage with electricity from an off-board source (such as the electric utility grid). The vehicle can then drive in a charge-depleting (CD) mode that reduces the system’s state-of-charge (SOC), thereby using electricity to displace liquid fuel that would otherwise have been consumed. This liquid fuel is typically petroleum (gasoline or diesel), although PHEVs can also use alternatives such as bio-fuels or hydrogen. PHEV batteries typically have larger capacity than those in HEVs so as to increase the potential for petroleum displacement.

PHEV batteries can be charged several ways: by an outside electric power source, by the internal combustion engine, or through regenerative braking. If a PHEV is never plugged in to charge, its fuel economy will be about the same as that of a similarly sized HEV. If the vehicle is fully charged and then driven a shorter distance than its all-electric range, it is possible to use electric power only.

All-Electric Vehicles

 

EVs use a battery to store the electrical energy that powers the motor. EV batteries are charged by plugging the vehicle into an electric power source.

EVs are considered to be zero-emission vehicles because their motors produce no exhaust or emissions. Since EVs use no other fuel, they help reduce petroleum consumption.

Currently available EVs have a shorter range per charge than most conventional vehicles have per tank of gas. Light-duty HEV, PHEV, and EV models are currently available from a number of auto manufacturers, with additional models expected to be released in coming years. There are a variety of medium- and heavy-duty options available.

The first gasoline-electric hybrid automobile in the world was developed in 1900 by Ferdinand Porsche (the Lohner-Porsche Mixte Hybrid). The hybrid- electric vehicle did not become widely available until the release of the Toyota Prius in Japan in 1997, followed by the Honda Insight in 1999.

Worldwide sales of hybrid vehicles produced by Toyota, the market leader, reached 1.0 million vehicles by May 31, 2007; the 2.0 million mark was reached by August 31, 2009; and 3.0 million units by February 2011, with hybrids sold in 80 countries and regions. Worldwide sales are led by the Toyota Prius, with cumulative sales of 2.0 million by September 2010, and sold in 70 countries and regions. The United States is the largest hybrid market in the world, with 2 million hybrid automobiles and

SUVs sold through May 2011, and California is the biggest regional American market. The Prius is the top selling hybrid car in the U.S. market with 1 million units sold by April 2011.

How are EV and PHEV batteries charged?

Charging EVs and PHEVs requires plugging the vehicle into charging equipment, also called electric vehicle supply equipment (EVSE).

Charging times vary based on how depleted the battery is, how much energy it holds, and the type of battery and EVSE. The charging time for a fully depleted battery can range from 30 minutes to more than 20 hours, depending on the vehicle and the type of charging equipment used. Because charging an EV or PHEV takes significantly longer than fueling a conventional vehicle at a gas station, most EVSE will be available in locations where vehicles park for extended periods, including residences, workplaces, and parking garages. The table above presents several EVSE options.

Modern charging equipment and vehicles are designed with standard connectors and plug receptacles, so drivers do not need to worry about whether their vehicles are compatible with charging equipment. Utilities are also working to upgrade local distribution infrastructure in neighborhoods with higher EV and PHEV concentrations to handle increased electricity demand and ensure uninterrupted service.

 

Are electric drive vehicles safe?

HEVs, PHEVs, and EVs undergo the same rigorous safety testing as conventional vehicles sold in the United States and must meet the Federal Motor Vehicle Safety Standards. In addition, their battery packs are encased in sealed shells and meet testing standards that subject batteries to conditions such as overcharge, vibration, extreme temperatures, short circuit, humidity, fire, collision, and water immersion. Manufacturers also design vehicles with insulated high-voltage lines and safety features that deactivate electric systems when they detect a collision or short circuit. For additional electric-drive vehicle safety information, refer to the AFDC’s Maintenance and Safety of Hybrid, Plug-In Hybrid, and All-Electric Vehicles page

How do maintenance requirements compare to those of conventional vehicles?

Because HEVs and PHEVs have internal combustion engines, their maintenance requirements are comparable to conventional vehicles. The electrical system (battery, motor, and associated electronics) doesn’t require scheduled maintenance. Due to the effects of regenerative braking, brake systems on these vehicles typically last longer than those on conventional vehicles.

EVs typically require less maintenance than conventional vehicles because:

• They have fewer moving parts

• Their brake fluid is the only fluid to change

• Regenerative braking reduces brake wear

• Their electrical systems don’t require regular maintenance.

How do fuel costs compare to those of conventional vehicles?

When discussing electric drive vehicles, “fuel” includes the gasoline, diesel, or alternative fuel used in the internal combustion engine, as well as the electricity used to charge the EV or PHEV battery. Taking both fuel types into account, fuel costs for electric drive vehicles are generally less than conventional vehicles due to higher vehicle fuel economy and low costs for electricity.

Electricity prices also tend to be more stable than conventional fuel prices, allowing greater certainty when budgeting for fuel costs.

For EPA fuel economy ratings and fuel cost comparisons between different vehicle models currently available in the United States refer to the Fuel Economy.gov website.

What are the emissions benefits of electric drive vehicles?

In general, HEVs, PHEVs, and EVs produce lower emissions than conventional vehicles. Vehicle emissions can be considered in terms of tailpipe emissions or well-to-wheel emissions. Tailpipe emissions refer to emissions produced through fuel combustion during a vehicle’s operation. Well-to-wheel emissions take into consideration the production and distribution of the fuel as well as the actual operation of the vehicle.

HEV tailpipe emissions are generated from the vehicle’s internal combustion engine and vary by vehicle and type of hybrid power system. Because HEVs generally achieve better fuel economy than comparable conventional vehicles, they produce lower emissions.

Because PHEVs can operate either in all-electric mode or with the help of the internal combustion engine, emissions vary based on the vehicle’s operating mode. When the vehicle is charged by an electrical power source, emissions calculations must take electricity production into account. On average, most categories of emissions are lower for electricity generated from power plants than from engines running on gasoline or diesel. However, emissions from electricity production depend on the efficiency of the power plant and the mix of fuel sources used. To determine your region’s specific fuel mix, as well as the emissions rates of electricity in your zip code, see EPA’s Power Profiler.

All-electric vehicles do not produce tailpipe emissions, so EVs are considered zero-emission vehicles by EPA. However, as with PHEVs, there are emissions associated with most U.S. electricity production. If electricity is generated from nonpolluting, renewable sources, EVs have the potential to produce zero well-to-wheel emissions.

Rania Hassan Mekky, M.Sc.

Senior Analog-Mixed Signal Design Engineer

rania_mekky@ieee.org

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