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Green car glossary


             

ActiveHybrid
Bioethanol
Biofuels
CNG (compressed natural gas)
CO2
Electric vehicles
Euro 5
E85
Flex fuel
Fuel cell vehicles
Full hybrid
Hybrid cars
Hybrids
Hybrid Synergy Drive (HSD)
Hydrogen

Internal combustion engine (ICE)
Intergrated Motor Assist (IMA)
Kilowatt hour (kWh)
Liquid Petroleum Gas (LPG)
Lithium ion battery (Li-ion)
Micro hybrid
Mild hybrid
Nickel metal hybrid battery (NiMH)
NOx
Plug in hybrid
Range extender
Range anxiety
Regenerative braking
Stop/Start
Voltec
Well-to-wheel cycle
Zero-emissions

 

 

ActiveHybrid

The brand name for BMW’s first roadgoing hybrid cars on the 7-series and X6.

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Bioethanol

Fuel made from plant matter (see biofuels).

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Biofuels

Biofuels are sustainable because they are created by growing crops and turning them into fuel. They still release CO2 from the tailpipe, but because the plants absorbed the same amount of CO2 when they were grown, the fuel is effectively carbon-neutral with no burden on the atmosphere. There are two types of biofuels: bio-alcohols (made through the fermentation of starches and sugars, just like your favourite tipple) and bio-oils (made typically from rape seed oil). Although biofuel can be used neat in an appropriately modified engine, it is usually blended with petrol or diesel. A standard engine should be able to run a blend of up to 5% biofuel without modification. Specially adjusted engines on flex-fuel vehicles can run E85 (85% ethanol/15% petrol). Biofuels would slot easily into our infrastructure since it could be pumped from existing petrol stations.

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Compressed natural gas (CNG)

CNG remains rare in the UK as an automotive fuel though ironically we’ve cooked with it for years. CNG is stored on board the car in gaseous form at high pressure. Burning it produces around 80% less NOx and 50% less CO than petrol – but despite a huge infrastructure in the UK supplying it for domestic and industrial use, CNG hasn’t made inroads onto the forecourt. Despite being greener than petrol or diesel, both LPG and CNG are still unsustainable fossil fuels, carry less energy than the liquid fuels and are harder to package within the car.

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CO2

Carbon dioxide, the exhaust gas that’s been linked to global warming. Most of Europe’s car taxation systems are now based on CO2. An average car today emits around 160 grammes per kilometre; anything under 120g/km qualifies for cheaper road tax, cars with less than 100g/km are free.

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E85

A biofuel mix with 85% biofuel, 15% regular unleaded.

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Electric vehicles (EV)

Electric cars rely on a large electric motor to get around, usually fed with a supply of electricity from a hefty battery. Most EVs are experimental town cars or utility vehicles like milk floats. Because an electric motor delivers maximum torque from standstill, they don’t need a clutch and because the motors spin up to very high speed, you don’t need to change gear either. Want to go backwards? Then the motor reverses. From a green perspective, battery electric power only makes sense if the energy used to charge the batteries isn’t generated by a fossil fuel power station and in the UK, most of it is. Use electricity generated by wind, solar or nuclear power and the argument stacks up. Despite the fact that batteries deliver DC (direct current) modern electric car motors are all AC (alternating current) for greater efficiency. A black box called an inverter converts the juice from DC to AC.

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Euro 5

The emissions laws in Europe. They started with EU1 launched in July 1992 and have progressed through numerous iterations to the current EU5 standard. Since the 1970s passenger car emissions have been cut by more than 95 percent. Consider the drop in allowances from EU1 to 2014’s proposed EU6 regs – diesel cars’s hydrocarbon and NOx emissions will have to fall from 0.97g/km to 0.170g/km.

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Flexfuel

A generic phrase for a car that can run on different fuels. Saab’s flex-fuel vehicles can use biofuels or conventional petrol – the engine management software adjusts depending on the fuel it senses.

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Full hybrid

The more sophisticated hybrid vehicles that can run on electric power alone, such as the 2009 Toyota Prius. Not all hybrids can run on battery-only mode, their electricity merely supplements internal combustion.

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Fuel cell vehicles

When it comes to cleaning up tailpipe emissions, nothing does a better job than fuel-cell power. A fuel cell chemically converts hydrogen and airborne oxygen into electricity, water and heat. Arranging a few hundred individual cells into a ‘fuel cell stack’ provides enough energy to provide a family-sized electric car with punchy performance. Fuel cells succeed where batteries fail. Instead of charging them up, they produce power by consuming hydrogen fuel from a tank – either in liquid or gaseous form then reacting it with oxygen from the air. You refuel from a forecourt pump just as you would with petrol or diesel, so they don’t go ‘flat’ leaving you stranded by the roadside. Best of all is there are no nasty sniffs from the exhaust, just hot air and water vapour. There are problems however – namely cost (current development cars are well over £1m each) and a viable hydrogen refuelling network. Don’t expect widespread commercial fuel cell vehicles any time before 2015 at least.

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Hybrid cars

Hybrid drives combine the power of a combustion engine with the torque of an electric motor. This saves fuels in various ways: the petrol or diesel engine can be downsized and tuned for economy rather than torque; energy wasted during braking can be recaptured through regenerative braking; full hybrids can run on electric power around town. Hybrids are however expensive and widely considered a stepping stone technology rather than an ultimate goal.

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Hybrid Synergy Drive (HSD)

Toyota’s brand name for its patented hybrid system. It’s the technology underpinning the Prius and Lexus’s hybrids.

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Hydrogen

The most plentiful element in the universe. When manufactured using sustainable means, like electrolysis of water using electricity from solar or hydroelectric power, then hydrogen has the potential to deliver an environmentally guilt-free trip. Because it is an element, hydrogen has no carbon in its composition – so it can be burned in an internal combustion engine with only water, heat and a small amount of NOx as a by-product. BMW, Mini and Mazda have all produced experimental cars burning hydrogen. But hydrogen’s biggest potential is to power a fuel cell, producing electricity, heat, water and nothing else. Hydrogen is already widely used in industry and routinely shipped worldwide, but it would take a massive commitment from both politicians and oil companies. One potentially thorny problem is storage on-board vehicles – it’d need to be stored either in a ‘cryogenic’ method, where the hydrogen is kept in liquid form at -253C in a giant thermos flask or compressed in carbonfibre tanks at up to 10,000psi. Even at those sort of pressures, it’s difficult to store the equivalent energy to a tankful of petrol, so range is still a compromise. And despite stringent tests proving the safety of the special fuel tanks, there are concerns about crash safety.

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Internal combustion engine (ICE)

Shorthand for any conventional petrol or diesel engine. Don’t give up on ICE just yet – innovations such as downsizing and Fiat’s MultiAir system will ensure that unleaded and derv continue to provide the lion’s share of motive power for at least the next decade.

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Integrated Motor Assist (IMA)

Honda’s branding for its hybrid tech.

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Kilowatt hour (kWh)

A measure of electrical energy: 1kWh means a constant rate of 1000 watts of energy usage for one hour.

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Liquefied petroleum gas (LPG)

LPG is carried in compressed liquid form and has been a popular alternative to petrol for a few decades now. A number of major manufacturers produce bi-fuel cars capable of running on either petrol or LPG. They cost more but are eligible for government grants and exemption from some urban congestion charges. LPG produces less CO2 than petrol but has a lower energy density – so it produces less power too. It can be used in converted petrol engines fitted with appropriate injection and engine management systems. There are around 1200 LPG sites in the UK, but that’s still too few to guarantee convenient to most motorists.

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Lithium ion battery (Li-ion)

The latest rechargeable battery technology. The anode contains lithium, the cathode a type of carbon. Lithium ion batteries have high energy density and suffer from slow self-discharge when not in use. They are, however, more expensive than older nickel metal hydride batteries.

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Micro hybrid

A fancy name for a stop-start system. This uses a low-cost, belt-driven starter-alternator unit to stop and start the engine in traffic to avoid idling away precious fuel.

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Mild hybrid

A hybrid car that can only run when its petrol or diesel engine is powering the car. Electric power only ever assists the internal combustion engine. The Honda Insight is a mild hybrid – it cannot run on battery power alone.

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Nickel metal hybride battery (NiMH)

An older type of battery technology that’s cheaper and more proven than lithium ion battery packs. However, it has a lower energy density and discharges over time. Most household AA batteries and similar are nickel metal hydride.

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NOx

Nitrogen oxides, a polluting byproduct of burning fossil fuels.

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Plug in hybrid

A type of  hybrid which lets you plug in and charge up the battery at home overnight, so you always start each journey with a full charge – allowing more zero-emissions electric operation around town for a full hybrid.

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Range extender

A hybrid system such as on the Opel Ampera and Chevrolet Volt – where the internal combustion engine is used purely to charge up the battery, rather than power the wheels. Because of this limited use, the motor can be tuned for maximum economy.

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Range anxiety

A phrase coined to express a driver’s worry that his car won’t reach the final destination on the charge availability. Unlike a petrol car, you can’t top up your battery if you run out of juice.

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Regenerative braking

A system on any battery-powered car, where energy wasted during braking is recaptured to top up the battery charge. Rather like a dynamo on your pedal cycle.

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Stop-start

Stop start or ‘starter-alternator’ devices have been around since the 1970s. The idea is that when you pull up to the lights, the engine stops. All you have to do is release the brake or brush the clutch pedal and the engine restarts letting you pull away. VW’s  Polo Formel E of  the 1980s had a system combined with a manual gearbox which utilised the conventional geared starter motor. It was noisy and not all that robust, but today’s technology comprising a belt-driven, combined starter-alternator is far superior. These modern units work quietly and efficiently at around twice the speed of a normal starter, spinning the engine fast to minimise the amount of fuel used during start up. Stop-start can save around 15% in fuel bills – and it’s far cheaper than a full hybrid system.

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Voltec

GM’s range-extending hybrid system – as seen on the Chevrolet Volt and Opel Ampera.

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Well to wheel

This is a way of considering the entire energy cycle for a given mode of transport, rather than just tailpipe emissions. Consider a battery electric vehicle like one of those weird city cars politicians love to be seen in. It produces no CO2 when you drive it so it must be environmentally sound, right? Wrong. If the electricity used to charge the batteries came from a coal-fired power station then your EV’s true CO2 burden would be pretty much as big as that of a petrol engine – or worse. Charged by electricity from a wind turbine, the same car would perform better on a well-to-wheel basis. You can apply the same philosophy to other forms of alternative propulsion. Biofuel is sustainable, but the crops used to make it have to be harvested. Just think of all those diesel-powered combine harvesters and of the electrical power feeding hungry processing plants. There’s still a CO2 penalty to pay. Hydrogen is commonly made by electrolysis of water. But where does that electricity come from? Well-to-wheel arithmetic can be as simple or as complicated as you want. But the results generally point to one simple fact. There’s no such thing as a free lunch.

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Zero emissions (ZE)

The generic term for any car that has zero emissions at the tailpipe. So a battery-powered car is nominally ZE – but don’t forget to ask where the energy came from that went into the battery in the first place.

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