It's one thing to drive a vehicle that's called "eco-friendly" - it's another to actually know why and how said vehicle is better for the environment than the one your neighbor is driving? Do you know what the difference is between a hybrid and a plug-in electric vehicle? Don't feel too bad if you don't because you're far from the only one.

Here's a brief rundown of the what's what in environmentally-conscious vehicles so the next time someone asks you your thoughts on the low-emission trend, you can nod knowledgeably and add your two cents to the conversation. Or even better, make a green choice should you be in the market for a new set of wheels!

Plug-in electric
Plug-in electric vehicles have no emissions thanks to an internal combustion engine that does not require the use of a gasoline-powered engine. Instead they use battery packs and energy from your local grid, but do not require the frequent trips to a local station or the accompanying oil changes of a more traditional vehicle. Nor do they have the fuel tank and other components of the car you are probably used to driving. Instead you simply plug your vehicle into an electrical outlet, much the way you would with your cell phone that requires recharging.

Though electric cars have no fuel emissions to consider, they do consume electricity and should the demand for the vehicles ever be great enough, could significantly increase the demand for electricity.

Hydrogen-powered
A hydrogen-powered vehicle may be one of the most eco-friendly of all - a vehicle that runs on clean water with absolutely no carbon emission. But is it realistic? Experts say not yet, though there is a push to make it happen. The BMW Hydrogen 7 version of a hydrogen vehicle has been a hit with celebrities like Brad Pitt, Angelina Jolie and Kristen Davis, while America Ferrera (aka Ugly Betty) has been rumored to be a fan of the Chevrolet Equinox Fuel Cell. However, the fact remains, the high costs of manufacturing fuel cell vehicles and the lack of infrastructure to actually support them.

In a car with a hydrogen internal combustion engine, the hydrogen burns the same was as the fuel does in a traditional vehicle. In a hydrogen fuel cell vehicle, the reaction between hydrogen and oxygen produces water and electricity to power an electric traction motor.

Solar-powered car
This type of vehicle almost explains itself. Much the same as solar panels work to power a home, they work to provide power to a car. These panels are used to generate electricity by converting sunlight into energy. Because sunlight is already used to provide heat and electricity to homes, some hold onto the hope that they can revolutionize the auto industry.

Currently solar cars are mostly built as an experiment by teams in a competition, not as viable vehicles to be purchased on a lot by consumers. These cars use different types of batteries in its electrical system including lead-acid batteries, nickel-metal hydride and Lithium ion batteries. 

Hybrid
Hybrid vehicles use two sources of power, such as the internal combustion engine you would find in a traditional vehicle with a rechargeable system such as a battery or an electric motor. Hybrids are not just limited to the production of cars, but include SUVs, trucks and even buses.

The two sources used in hybrid vehicles is rapidly expanding to include plug-in hybrids, diesel-electric hybrids that rely on bio diesel and even hydrogen fuel cell hybrid.

Fuel-efficient
These vehicles don't technically classify as one the green cars as they do not necessarily utilize any of the aforementioned technology. Instead these vehicles are "traditional" ones that get great gas mileage and have reduced emissions.

It also turns out the even the newer cars don't always equal the best; often times older models of some cars get more miles per gallon. The 1996 Geo Metro XFI for example, achieves the same number of miles per gallon as the Toyota Prius, however without the recent manufacturing process to factor in.

» Plug In America

Electrovaya may be a Canadian company, but their latest product is geared toward an American audience - for now. The four-passenger, lithium-ion powered electric car named the Maya 300 can drive up to 120 miles without recharging using an extended battery option which is 27 kilowatt hours , while the standard battery can drive for up to 60 miles at 12 kilowatt hours.

The Maya 300 is being introduced to the public as part of Altcar, a new electric car share-and-rental program in Baltimore. The car features similar properties to a traditional car including its size (the same as a subcompact car), ability to fit four adult passengers, as well as airbags, power windows, an air-conditioning and heating system and front wheel drive. Where it differs from the family car that is currently sitting in your driveway is the Lithium-Ion SuperPolymer battery, developed by Electrovaya. Unlike the batteries in other cars, this one is significantly smaller than a conventional lead acid battery pack, and therefore takes up much less space. For now the car is only ideal for use in the city, as it reaches a maximum speed of 35 miles per hour, however Sankar Das Gupta, CEO of Electrovaya says there are plans to produce a version of the car suitable for highway travel in the future.

Gupta also says he hopes to see the Maya 300 available to Canadians in the near future. "The regulations in Canada are slightly different from the U.S. regulations, but I think it should be available [in Canada] shortly."

ExxonMobil is also a partner of the project, having developed the car's lithium-ion battery separator film. The company counts its collaboration with the Maya 300 as part of the ongoing efforts to improve energy efficiency and reduce greenhouse gas emissions associated with the business operations.

The Maya 300 will not be available to the public for purchase until 2011, however those interested in seeing it first-hand can visit the Maryland Science Center until the end of this month and test-drive the Maya 300 for free with the purchase of admission to the center. Beginning August 1, drivers can rent the car for $7.50 per hour upon becoming a member of the Altcar program. The program features a car-sharing fleet of battery powered electric vehicles, as well as plug-in hybrid cars. The Altcar initiative is the first program in the U.S. to use this new advanced lithium-ion polymer technology. 

The inner-city traffic congestion and air pollution in Baltimore made it an ideal location to test the Maya 300 and the Altcar program, but Van Reiner, president and CEO of the Maryland Science Center, believes there could be potential elsewhere as well.

"Certainly other cities could copy," he said. "There are other cities with downtown congestion that would also benefit from use of an all-electric urban car-share program."

Reiner is also optimistic regarding the long-term success of the Altcar program.

"I believe this will outlast me," says Reiner. "We are very optimistic this urban car share program is just the tip of the iceberg and I expect that as time goes on, it will continue to grow and will be self-sustaining. There are a lot of city vehicles that never leave the confines of the city where this would be absolutely perfect for them."

» Electrovaya (Official Site)

Earlier this week we told you about a rumored partnership between the Electric Power Research Institute (EPRI) and General Motors. Today EPRI confirmed the research and development venture that they, GM and 34 other top utility providers will work on in an effort to make plug-in hybrid electric vehicles (PHEVs) more mainstream and accessible to consumers than they currently are.

These type of vehicles are seen as the most likely solution to reducing society's dependency on traditional gasoline, as they not only substanially reduce greenhouse gas emissions, but cost less to fuel as well. The project will also seek to find solutions for safe and convenient vehicle charging, educating the public and creating public policies  that will help aid the transition to alternative-fuel vehicles. Both major players in the collaboration commented on the importance of the sectors working together to achieve this.

“The EPRI-GM-utility effort is the result of many years of work by EPRI and its members to advance plug-in hybrids and related infrastructure technology to a point of feasible implementation and eventual commercialization,” said Arshad Mansoor, EPRI’s vice president of Power Delivery and Utilization. “Seamless integration of PHEVs into the electric grid will require close collaboration between the automobile and electric sectors.”

“Electrically powered vehicles are going to provide tremendous benefit and excitement for the customer, while also hastening the move to a more diverse choice of energy alternatives,” said Jon Lauckner, GM vice president of Global Programs. “But we know that there are some key elements that need to be understood and put in place so customers can enjoy those benefits and get maximum use of these vehicles when we bring them to market. That’s why this relationship with EPRI and the utility partners is so important.”

» The Auto Channel

The British International Motor Show begins one week from today and the UK's first electric taxi is going to do it's darndest to steal the green spotlight when it officially launches.

The E7 taxi was built by Allied Vehicles in Glasgow and took three years of research and development by the company to get to this stage. The E7 runs entirely on Lithium-ion batteries manufactured by Axeon Holdings, and these batteries allow the car to travel up to 100 miles with one charge at a maximum speed of 60 miles per hour.The nature of the battery means the car has no carbon or pollutant emissions.

It's a shame then the Public Carriage office in the taxi licensing division of Transport for London denied the new vehicle, making it unlikely the the taxi will actually be used for its intended purpose in the near future. Here's hoping that changes because Allied is confident that the E7 could be an answer to some of the problems taxi drivers in the UK currently face.

“Taxis and their drivers have a hard life and with the rising cost of diesel at the moment, it is only going to get worse,” said Gerry Facenna, Chairman of Allied Vehicles.

“For the majority of taxi drivers, the key issue when buying a new cab is usually the cost to run, service and maintain their vehicle. In the current economic climate drivers are looking for ways to reduce costs and electric power offers an ideal solution, especially for congested urban areas where traffic is stop-start for much of the day.

“We’ve had a positive response to electric vehicles from many local authorities, both in the UK and in Europe. However it’s a shame that London looks set to miss out, especially since its famous taxi fleet is currently responsible for 4% of all emissions in the capital,” he added.

» The Auto Channel

The Electric Lightning GT is Britain's latest eco-friendly car set to launch next year, and sports car enthusiasts may feel their hearts start to race and their palms start to sweat when they learn some of the car's impressive features.

Acceleration of zero to 60 miles per hour in four seconds? Check. Top speed of 130 miles per hour and 700 horse-power? You betcha. Regenerative braking and rechargeable batteries? Well of course.

The total charge time for the 30 batteries in the Lightning GT is ten minutes, allowing a travel distance of 200 miles. It's even said to be more powerful than a Porsche and 10 times less expensive to run than the equivalent gasoline engine. You'll probably want to make sure you have some expendable income kicking around though, since the £120,000 price tag isn't exactly pocket change, nor is the vehicle the most practical replacement for a family car.

For now all you'll need to scrounge up is the £15,000 deposit to secure one of the cars. If you want to see it up close and in-person, the prototype will make its debut at the British International Motor Show in London later this month.

» Telegraph

The Volkswagen Golf Twin Drive Concept is generating even more interesting the the Golf TDI Hybrid that was introduced at the Geneva Car Show . The car will combine a fuel-efficient diesel engine with plug-in hybrid technology, running in electric mode for up to 30 miles on an 82 horsepower electric motor. Once the batteries are dead it will switch to a 2.0-liter turbo-diesel engine for a combined total of 174 horsepower. In an effort to reduce emissions, the car will feature start-stop technology to prevent idling, while regenerative braking will recharge the batteries. The energy needed to charge the batteries will also be green, coming from windmills and hydro-electric dams.

The Golf Twin Drive sounds like a good concept, but that's the key word: concept. Whether the car will eventually be mass-produced and available for purchase is unknown at this point, however 20 of the vehicles will be test driven beginning in 2010 to determine if the model will have a place in the future market.

» Jalopnik