What Are Hybrid Vehicles?
Hybrid vehicles are called hybrids because they use both a small internal combustion engine (ICE) and an electric motor to obtain maximum power and fuel economy with minimum emissions. How they do this varies from one model to another, with varying success.
What all hybrids have in common is the ability to generate electric current, store it in a large battery, and use that current to help drive the car. Hybrids capture electrical energy produced by a regenerative braking system, and their engines can power a generator, too. Hybrids can also conserve energy by shutting down the ICE when the vehicle is in Park, idling at a light, or stopped in traffic, or when the electric motor’s energy is sufficient to drive the vehicle without assistance from the ICE.
Hybrids have regenerative braking systems that generate electric power to help keep the batteries charged. When the driver applies the brakes, the electric motor turns into a generator, and the magnetic drag slows the vehicle down. For safety, however, there is also a normal hydraulic braking system that can stop the car when regenerative braking isn’t sufficient. There’s no difference in maintenance or repair except that the brake pads tend to last much longer because they don’t get used as much. In fact, if you drive a hybrid in a moderate manner, you almost never actually use the disc brakes on the wheels and may be able to go the life of the car without changing pads. The big difference is that regenerative brakes capture energy and turn it into electricity to charge the battery that provides power to an electric motor.
Parallel hybrids
A parallel hybrid uses both an electric motor and an ICE for propulsion. They can run in tandem, or one can be used as the primary power source with the other kicking in to assist when extra power is needed for starting off, climbing hills, and accelerating to pass other vehicles. Because both are connected to the drive train, they’re said to run “in parallel.”

How a parallel hybrid works.
Series hybrids
A series hybrid uses a gasoline or diesel ICE, coupled with a generator, to generate electricity but not to drive the car. The engine can send the electric current directly to the electric motor or charge a large battery that stores the electricity and delivers it to an electric motor on-demand. The electric motor propels the vehicle, using its power to rotate a driveshaft or a set of drive axles that turn the wheels.

A series hybrid.
Plug-in hybrids
Because plug-in hybrids feature larger batteries that can be charged at any ordinary 110-volt electrical socket, they have the capacity to extend the ability of the electric motor to drive the car farther without the need for starting the ICE and therefore substantially increase the vehicle’s fuel efficiency. Estimates have ranged as high as 100 mpg!
Some technologically savvy individuals have adapted their hybrid vehicles into plug-in hybrids, and automakers are in the process of developing and producing them (sometimes in cooperation with major utility companies). The development of new, smaller, high-capacity lithium-ion batteries that can be recharged many times is the key to making plug-in hybrids available to the general public. Estimates are that plug-in hybrids equipped with these more powerful batteries will have a range of as much as 125 miles before the charge is depleted and the vehicle reverts to standard hybrid mode.

A plug-in hybrid.
The main environmental problem with plug-in hybrids is that the electric current they draw is usually generated by utility companies powered by fossil fuels. The good news is that some major chains have committed to establishing charging stations powered by solar panels or wind energy, and many hybrid owners are willing to install solar panels to recharge these vehicles at home. Plug-in hybrids charged by commercial sources of electricity or solar panels will be less dependent on the ICE, but will still need it for long trips, climbing hills, and so on. Future hybrids may use a small fuel cell to make electricity from hydrogen, which would mean the ICE would have to run even less frequently.
Two-mode hybrids
Two-mode hybrids may be the key to a competitive place for the U.S. in the hybrid market. Instead of the large storage battery found on conventional hybrids, two-mode hybrids use smaller batteries and two electric motors located inside an automatic transmission with two sets of gears — one for the ICE and the other to amplify the power of the electric motors. The transmission can function as a continuously variable transmission, as well. In one mode, at lower speeds, the vehicle can run with one or both electric motors, with or without the ICE, or on the ICE alone. At higher speeds, the second mode kicks in, and the ICE runs continuously in its higher gear ratios.

A two-mode hybrid.

Green Living Glossary
acid rain
A mild acidic solution that falls in rain or as dry particles caused when fossil fuel burning produces sulfur dioxide and nitrogen oxides. Acid rain has been linked to damaging effects on waterways and forests.

Green Living Glossary
active solar design
A strategy for designing high-performance, ultra-energy-efficient buildings. Active solar incorporates all the elements of a passive solar design with additional mechanical equipment, such as pumps or fans, to take advantage of the heat from the sun.

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alternative energy sources
Wind, hydro (water), biomass (fuel from natural material such as crops and agricultural waste), and solar power.

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biodegradable
Made from materials that will decay and break down into naturally occurring elements in a fairly short amount of time.

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biomass
Fuel made from natural material such as crops and agricultural waste.

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Bokashi
A Japanese term referring to a process of fermenting organic matter

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carbon emissions
Carbon released when many substances — particularly fossil fuels such as oil, gas, and coal — are burned by vehicles and planes; by the manufacturing processes of many consumer goods; and by the heating, cooling, and electricity for your home.

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carbon neutral
The state of reducing a person’s carbon emissions as much as possible and balancing the remaining carbon emissions by offsetting them with processes that consume carbon.

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carbon offsets; carbon credits
Paying for or participating in programs that reduce the carbon in the atmosphere. Purchased shares go toward reducing the same amount of environmental costs that an activity expends. Carbon offset programs or projects often involve tree planting because trees have a huge capacity to absorb carbon from the atmosphere. Other programs involve everything from supporting solar and wind power to replacing fossil fuel–burning stoves in developing countries with more sustainable energy sources.

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carcinogen
A cancer-causing substance.

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carpooling
Reducing the number of vehicles going to the same destination by having two or more people ride in the same vehicle. In most cases, carpoolers take turns being the driver and using their own vehicles.

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car-sharing
A system in which a person pays a fee that gives them access to a vehicle (or a pool of vehicles), usually parked in an easily accessible location. Car-sharing can eliminate the need for a personal vehicle.

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climate change; global warming
Changes in the concentrations of various gases in the atmosphere that are affecting the planet’s climate. Many scientists believe that the increase of carbon dioxide is a primary contributor to global warming, which occurs when gases trap warmth in the earth’s atmosphere instead of letting the atmosphere release it.

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compact fluorescent CFL bulbs
Fluorescent light bulbs that fit into a standard light bulb socket and use a fraction of the energy of their incandescent counterparts.

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compost
Decayed plants and other organic matter that breaks down into rich soil.

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core aerating
Poking small holes in the top few inches of lawn to encourage the flow of air, water, and nutrients.

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corporate social responsibility
Principles adopted by a business to make sure that its operations harm no one and instead benefit everyone around it and involved in it.

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daylighting
Bringing natural light into a home.

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ecosystem
A community of living organisms and nonliving materials.

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ecotourism
Sustainable and ethical travel in a natural environment.

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Energy Star
The federal government system for rating energy efficiency in appliances.

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Environmental Protection Agency EPA
Federal agency that regulates environmental laws.

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Fairtrade
System to ensure that workers and producers receive fair value for their products and that mandates sustainable practices in producing those products.

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food miles
The distance food travels from where it’s produced to the consumer.

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foodprint
The amount of land that various diets require to sustain them.

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fossil fuels
The energy-rich organic substances, traced back to the remains of organisms that lived 300 to 400 million years ago, that modern societies burn to provide power.

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geothermal
Energy within the Earth in the form of heat.

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greenhouse effect
The warming of the planet caused by gases in the atmosphere trapping the sun’s heat instead of letting it get through to space. This action is very similar to what happens in a greenhouse.

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greenhouse gases
Gases such as carbon dioxide, methane, and nitrous oxide produced by the burning and processing of fossil fuels and that contribute to global warming and acid rain.

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greywater
Water already used for washing, laundry, or showering that is appropriate for household functions from toilet flushing to watering plants.

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Leadership in Energy and Environmental Design LEED
A scoring system to rate how ecologically friendly buildings are.

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light shelves
White or light-colored horizontal fins above windows that bounce sunlight up onto the ceiling to bring it deeper into the room.

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light-emitting diode LED
A tiny semiconductor that emits light.

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natural gas
An energy source that burns cleaner than coal and oil but still releases carbon dioxide when it burns and methane during production, storage, and transportation.

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organic
Of living things; in food, grown without chemical fertilizers or pesticides or genetically modified organisms.

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passive solar design
Building design that takes advantage of the fact that the summer sun is higher than the winter sun. Overhangs shade the building from the summer sun and allow the lower winter sun to enter the building and heat it.

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petrochemicals
Chemicals derived from petroleum.

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phantom load; standby power
Energy drawn by a plugged-in appliance even when the appliance is turned off.

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plastic identification code
A triangle with a number from 1 to 7 inside indicating what type of plastic an item is made from.

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PV cell
A photovoltaic cell; a cell with a thin semiconductor that converts solar power into electricity.

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recycling
Collecting goods that have reached the end of their lives and processing them, their parts, or some of their parts, into the raw materials from which new goods are made.

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renewable energy
Energy from sources that cannot be used up, such as wind, water, and the sun.

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skylight
A rooftop window that brings in twice the light of a traditional window of the same size.

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solar panel
A panel containing cells that convert sunlight into electricity.

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sun tunnel
A passage that brings light into a room by bouncing sunlight through a small dome skylight on the roof connected to another skylight on the ceiling of the room. (Also known as a sun tube, sun pipe, and solar tube.)

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sustainable
Using natural resources in a way that allows for continued viability.

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thermal hole
An opening such as a window that leaks heat and air-conditioning energy.

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thermal mass
The ability of a material to absorb and store temperature.

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three Rs
The environmental practices of reducing consumption, reusing items, and recycling.

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top-dressing
Applying a light scattering of compost, other mulch, or sometimes fertilizer, over soil surfaces to add organic matter or nutrients without digging it in

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toxic waste
Disposed materials that can cause harm to people, animals, or the environment.

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vermicomposting
Composting with worms.

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xeriscaping
Landscaping for water conservation; a practice of garden planning and maintenance.