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Carbon dioxide emissions from plug-in hybrid cars are as much as two-and-a-half times higher than official tests suggest, according to new research.

Plug-in hybrid vehicles are powered by an electric motor using a battery that is recharged by being plugged in or via an on-board petrol or diesel engine.

They account for 3% of new car sales.

But analysis from pressure groups Transport and Environment and Greenpeace suggest they emit an average of 120g of CO2 per km.

That compares with the 44g per km in official "lab" tests

Plug-in hybrid electric vehicles (PHEVs) are sold as a low-carbon alternative to traditional vehicles and conventional hybrids - which cannot be recharged from an external source - and are proving increasingly popular.

The new research is published as the government considers whether to bring forward a proposed ban on the sale of new petrol, diesel and conventional hybrid cars from 2035 to 2030.

'Official' versus 'real world'

The BBC understands one suggestion is that plug-in hybrids should be given a stay of execution, with new sales allowed to continue until 2035.

That's because they can offer a 20- to 40-mile range as a purely electric vehicle and are therefore potentially significantly less polluting than other vehicles.

But this new analysis from Transport and Environment and Greenpeace suggests they don't offer anything like the carbon dioxide savings claimed for them by manufacturers.

The official tests indicate that plug-in hybrids emit an average of 44g per km of CO2. These tests are conducted on a circuit and see vehicles driven in a way that regulators consider "normal".

The real figure, however, according to the report, is more like 120g per km.

A really simple guide to climate change

The five major challenges facing electric vehicles

How will the petrol and diesel car ban work?

The pressure groups have analysed what they say is "real-world" data on fuel efficiency collected from some 20,000 plug-in hybrid drivers around Europe.

These are drivers who have chosen to record their mileage and fuel consumption for surveys or who drive company or leased vehicles whose fuel efficiency is recorded.

According to this data-set the lifetime emissions of a plug-in hybrid average around 28 tonnes of CO2.

By comparison, the average petrol or diesel car is estimated to emit between 39 and 41 tonnes of CO2 from fuel during its lifetime, a conventional hybrid would typically emit more like 33 tonnes.

According to these figures a plug-in hybrid would only deliver an emissions reduction of about a third on a typical petrol or diesel car - far less than the official estimates.

The motor industry acknowledges that lab tests don't always reflect real-world use but criticised the report, saying it uses emissions data from a test that is two years old.

"PHEVs provide a flexibility few other technologies can yet match with extended range for longer, out-of-town journeys and battery power in urban areas, reducing emissions and improving city air quality," Mike Hawes, the chief executive of the Society of Motor Manufacturers and Traders told the BBC.

He says he expects the range and performance will continue to improve, making them an "essential stepping stone to a fully electric vehicle".

Greenpeace meanwhile describes PHEVs as "the car industry's wolf in sheep's clothing".

"They may seem a much more environmentally friendly choice," says Rebecca Newsom, the pressure group's head of politics, "but false claims of lower emissions are a ploy by car manufacturers to go on producing SUVs and petrol and diesel engines."

Driver behaviour

Transport and Environment's analysis says a key problem with plug-in hybrids is that so many owners rarely actually charge their cars, meaning they rely on the petrol or diesel engine.

Another is that many plug-in hybrid models include design features that automatically turn on the petrol/diesel engine at start-up on a cold day, or will kick in that engine if driver accelerates hard.

The latter mode means that the car's emissions will depend a lot on the driver's behaviour.

"If you always charge the battery and tend to do lots of short journeys, they will have very low emissions," says Nick Molden, who runs Emissions Analytics, a company that specialises in vehicle emissions evaluation.

"If you never charge the battery and drive very aggressively then they can have significantly higher emissions than the equivalent petrol or diesel model," he continues.

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Hickky

It strikes me that the level of CO2 emitted by passenger vehicles is but a flea bite on the total CO2 produced by both flora and fauna, the planet and other production from industry, for example, electrical production. 

So what we really need is less of an engine, more of a generator, running at an speed designed for lowest emissions, via a dynamo to a battery that in turn drives electric motors. I guess all you railway engineers are vindicated as diesel/electric locomotives showed mankind the way.

No, not lowest emissions on the road, but how much do gas turbine power stations emit? Maybe we should limit our National Grid to Hydro, Wind and tide then Nuclear Power for zero CO2?

But battery bikes should be compulsory for solo drivers, no cars unless you are two up or more. All deliveries can be via tinternet by then anyway. 

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Trev
3 hours ago, Tel said:

Carbon dioxide emissions from plug-in hybrid cars are as much as two-and-a-half times higher than official tests suggest, according to new research.

Plug-in hybrid vehicles are powered by an electric motor using a battery that is recharged by being plugged in or via an on-board petrol or diesel engine.

They account for 3% of new car sales.

But analysis from pressure groups Transport and Environment and Greenpeace suggest they emit an average of 120g of CO2 per km.

That compares with the 44g per km in official "lab" tests

Plug-in hybrid electric vehicles (PHEVs) are sold as a low-carbon alternative to traditional vehicles and conventional hybrids - which cannot be recharged from an external source - and are proving increasingly popular.

The new research is published as the government considers whether to bring forward a proposed ban on the sale of new petrol, diesel and conventional hybrid cars from 2035 to 2030.

'Official' versus 'real world'

The BBC understands one suggestion is that plug-in hybrids should be given a stay of execution, with new sales allowed to continue until 2035.

That's because they can offer a 20- to 40-mile range as a purely electric vehicle and are therefore potentially significantly less polluting than other vehicles.

But this new analysis from Transport and Environment and Greenpeace suggests they don't offer anything like the carbon dioxide savings claimed for them by manufacturers.

The official tests indicate that plug-in hybrids emit an average of 44g per km of CO2. These tests are conducted on a circuit and see vehicles driven in a way that regulators consider "normal".

The real figure, however, according to the report, is more like 120g per km.

A really simple guide to climate change

The five major challenges facing electric vehicles

How will the petrol and diesel car ban work?

The pressure groups have analysed what they say is "real-world" data on fuel efficiency collected from some 20,000 plug-in hybrid drivers around Europe.

These are drivers who have chosen to record their mileage and fuel consumption for surveys or who drive company or leased vehicles whose fuel efficiency is recorded.

According to this data-set the lifetime emissions of a plug-in hybrid average around 28 tonnes of CO2.

By comparison, the average petrol or diesel car is estimated to emit between 39 and 41 tonnes of CO2 from fuel during its lifetime, a conventional hybrid would typically emit more like 33 tonnes.

According to these figures a plug-in hybrid would only deliver an emissions reduction of about a third on a typical petrol or diesel car - far less than the official estimates.

The motor industry acknowledges that lab tests don't always reflect real-world use but criticised the report, saying it uses emissions data from a test that is two years old.

"PHEVs provide a flexibility few other technologies can yet match with extended range for longer, out-of-town journeys and battery power in urban areas, reducing emissions and improving city air quality," Mike Hawes, the chief executive of the Society of Motor Manufacturers and Traders told the BBC.

He says he expects the range and performance will continue to improve, making them an "essential stepping stone to a fully electric vehicle".

Greenpeace meanwhile describes PHEVs as "the car industry's wolf in sheep's clothing".

"They may seem a much more environmentally friendly choice," says Rebecca Newsom, the pressure group's head of politics, "but false claims of lower emissions are a ploy by car manufacturers to go on producing SUVs and petrol and diesel engines."

Driver behaviour

Transport and Environment's analysis says a key problem with plug-in hybrids is that so many owners rarely actually charge their cars, meaning they rely on the petrol or diesel engine.

Another is that many plug-in hybrid models include design features that automatically turn on the petrol/diesel engine at start-up on a cold day, or will kick in that engine if driver accelerates hard.

The latter mode means that the car's emissions will depend a lot on the driver's behaviour.

"If you always charge the battery and tend to do lots of short journeys, they will have very low emissions," says Nick Molden, who runs Emissions Analytics, a company that specialises in vehicle emissions evaluation.

"If you never charge the battery and drive very aggressively then they can have significantly higher emissions than the equivalent petrol or diesel model," he continues.

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I would agree with this from my first hand experience of running a PHEV and having a couple on our 'fleet' at the company I owned. I never cease to be surprised how little understanding many have of the cars they own and company car owners are often the worst in this respect; can I get a German badge on the front, can I have the SE (insert some other meaningless model reference), how much in BIK will it cost me and that's about it. A PHEV relies on a) you charging it regularly b] having a typical driving profile that includes some short trips that can be covered mainly or exclusively in battery power. 

 

I ran a 292bhp 2.4l diesel + EV D6 Volvo V60 for three years and, including regular trips to France, Scotland and Cornwall, it averaged just over 100mpg, over 75k miles. A colleague (ok employee but I'm being PC :D) had a Mini Countryman PHEV and it wasn't as good on mpg as the diesel Countryman she ran previously. The main reasons (apart from a small performance edge with the Volvo, better range and top speed on EV power) was mainly down to the fact that the lady only charged it on the occasion she visited the office, for most of the time she was using the petrol motor to lug around a set of batteries and an electric motor she hardly used. She actually thought that as the batteries would charge from running the engine it was saving on fuel. Toyota and their 'self charging hybid' b*llocks have a lot to answer for - along wth woeful understanding of O level physics amongst most of the population :blink:

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MatBin
3 hours ago, Hickky said:

It strikes me that the level of CO2 emitted by passenger vehicles is but a flea bite on the total CO2 produced by both flora and fauna, the planet and other production from industry, for example, electrical production. 

So what we really need is less of an engine, more of a generator, running at an speed designed for lowest emissions, via a dynamo to a battery that in turn drives electric motors. I guess all you railway engineers are vindicated as diesel/electric locomotives showed mankind the way.

No, not lowest emissions on the road, but how much do gas turbine power stations emit? Maybe we should limit our National Grid to Hydro, Wind and tide then Nuclear Power for zero CO2?

But battery bikes should be compulsory for solo drivers, no cars unless you are two up or more. All deliveries can be via tinternet by then anyway. 

Already available, Honda Jazz ePhv.

The petrol engine does kick in  and drive the car's wheels for max speed, but it's primary function is to charge the battery and runs at a constant speed most of the time.

Edited by MatBin

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slowboy

Phevs, neither one thing nor the other. A battery powered car hauling an oversized generator, gearbox and a tank of fuel or a fuel powered car hauling round an electric motor and a load of batteries. And goodness only knows the amount of CO2 we generate talking about them 😂

Edited by slowboy
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Tonyj
18 minutes ago, slowboy said:

Phevs, neither one thing nor the other. A battery powered car hauling an oversized generator, gearbox and a tank of fuel or a fuel powered car hauling round an electric motor and a load of batteries. And goodness only knows the amount of CO2 we generate talking about them 😂

Methinks methane is more accurate :0)

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SteveThackery

I think it's important to point out that Toyota developed the Prius originally for the American market.  There was (is?) a long-held resistance to diesels for small cars in America, so the Prius was Toyota's attempt to meet the fuel economy of a diesel car, but with a petrol engine.

 

Back then it was not intended as a "save the world" solution. It was just a petrol car with diesel-like fuel efficiency.  Toyota knew all along that it was only an interim technology.

 

Now, of course, they've come along a fair way, but normal hybrid technology is only intended as a way of increasing the overall powertrain efficiency of an internal combustion car.  Hybrids do this primarily by allowing the engine to run at relatively steady speeds and loads, and in particular to avoid prolonged idling or low speed crawling, which is when they are operating at, or close to, zero efficiency.  Steady speeds/loads permits the use of the Atkinson cycle, which has a higher expansion ratio than compression ratio, which increases the thermal efficiency.

Plug-in hybrids are just a logical development whereby you can preload the battery with energy, rather than it all coming from the petrol.  Because electricity is untaxed, it is cost-effective to do so.  Obviously it requires a bigger battery than the standard hybrid in order to make it worthwhile.

 

I guess as batteries in PHEVs get bigger, they get closer to an EV in terms of their potential for zero tailpipe emissions.  No doubt a good thing, but having an internal combustion powertrain as well adds a tremendous amount of weight and complexity, of course.

I rather like the idea of the "series hybrid", in which the engine is not connected to the wheels at all - merely a generator which charges the battery.  In this mode it is less efficient than driving the wheels directly, but it does remove the need for the traditional IC transmission, plus it allows for constant speed/load operation, which as I said earlier allows for optimising thermal efficiency.  At its logical limit is simply an EV with a small petrol engine to provide range extension.

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tw586

do you guys really think the research from groups like Greenpeace or environmental activist is solid and could stand up to scientific scrutiny  

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Andy m

Not only do these daft things increase pollution, but you have the pollution caused by getting rid of the perfectly good Diesel car, making this thing and now no doubt replacing it. 

 

I had one out of Belfast Airport as a hire car. I was told not to bother trying to charge it, its just a petrol. The charging cable was still in a sealed bag on a 2000 mile car. 

 

The vehicle manufacturers love this stuff for stirring up the market, company cars in particular. Forget your massive Volvo Diesel, have a Rangerover clone with some batteries to make it heavier, we'll give you another in 21 months. They are trying to make life hard for people like me who intend to keep a petrol Toyota to 150000 miles by switching their business to "Employee safety management". 

 

Governments are the stupidest part of this. They know nothing so ask industry what the rules should be. Are we then surprised every VW passed TUV? Deciphering what academic cranks say we should aim for for, setting legislation and then making sure it happens is simply too much like hard work. Imagine the industry consultation response to the abolition of slavery. Sure, let all the people in the Caribbean go, but we can't have sugar running out. Tell you what, we'll get some lads with guns to pop over to China and recuit people, leave it to us, just give us few quid to buy guns and ships to get us going.... 

 

Andy

Edited by Andy m
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Trev
8 hours ago, SteveThackery said:


I rather like the idea of the "series hybrid", in which the engine is not connected to the wheels at all - merely a generator which charges the battery.  In this mode it is less efficient than driving the wheels directly, but it does remove the need for the traditional IC transmission, plus it allows for constant speed/load operation, which as I said earlier allows for optimising thermal efficiency.  At its logical limit is simply an EV with a small petrol engine to provide range extension.

 

I guess the i3 REX that I have is pretty close to this idea, the 2 cyl 'detuned' scooter motor is purely a generator so no gearbox, etc. It still adds just over 100kg but does mean I have full EV for the 95-98% of the time I don't need more than 140 mile range without stopping. Interesting that BMW have stopped producing the i3 in REX form for this third generation, their take is that the 180+ mile range combined with much greater availability of charge points now make it unnecessary but no doubt company car tax regimes (which 'punish'the REX for it's tiny generator by lumping it in with the PHEV's with 20-30 mile range, mainly big SUV's) have something to do with it.

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Mr Toad

I'm sure there's a bloke in a shed somewhere working on an aftermarket range extender. :) 

 

Start out with a generator bungied into the boot and work towards something neat and functional that can be installed post purchase.  

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Tel
6 hours ago, tw586 said:

do you guys really think the research from groups like Greenpeace or environmental activist is solid and could stand up to scientific scrutiny  

...maybe not, but as we've learned from all the bollocks spouted about the current flu-bug, no statistics can be relied on and nor can 'expert' scientific analysis...

I only posted the original for general information as we can, and will, all have our own thoughts on these issues and behave accordingly!

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