[teragram (OP)]

I refer to a magazine advert for the BMW 3 Series Plug-in Hybrid, in particular the quoted fuel consumption figures:-
Mpg(ltr/100Km) (weighted combined): 176.6 (1.6) to 201.8 (1.4). CO2 emissions (weighted) 36gm/Km.
Electric energy consumption (weighted combined) 15.4 - 14.8 KWh/100Km.
To make it easy I assume that 1ltr of petrol contains 10 KWh of energy

I don't know how these figures are arrived at, but on the face of it, 1.6 ltr/100Km = 16 KWh/100Km. If the "Electrical energy consumption" is 15.4 KWh/100Km, does this mean that the overall thermal efficiency is 15.4/16 = 96%?
What am I missing?

[Petrochemicals]

I refer to a magazine advert for the BMW 3 Series Plug-in Hybrid, in particular the quoted fuel consumption figures:-
Mpg(ltr/100Km) (weighted combined): 176.6 (1.6) to 201.8 (1.4). CO2 emissions (weighted) 36gm/Km.
Electric energy consumption (weighted combined) 15.4 - 14.8 KWh/100Km.
To make it easy I assume that 1ltr of petrol contains 10 KWh of energy

I don't know how these figures are arrived at, but on the face of it, 1.6 ltr/100Km = 16 KWh/100Km. If the "Electrical energy consumption" is 15.4 KWh/100Km, does this mean that the overall thermal efficiency is 15.4/16 = 96%?
What am I missing?

My reading is 176 litres ler 100 km or 2 gallon per mile, this is more than the 10mpg of the pegani zonda, perhaps its charging the battery at the same time ?

[alancalverd]

If you start with a full 12.5 kWh battery (standard fit for a BMW3) and 1 liter of gas, you would expect to cover about 2.5 times the distance on battery power alone (over 90% efficient) as on the gasoline, say 40 miles total. At 4.5 liter/gallon you could argue (incorrectly, but we are talking "advertising maths", not the real stuff) that this is equivalent to almost 180 mpg. 

Actual road test figures yield around 65 mpg with a brand new battery, because if you started with a full battery and one liter of gas you would only cover 40 miles before the machine stopped. You would then have to recharge the battery with engine power, which is way less than 50% efficient at converting gasoline to electricity and is just a waste of time - you might as well use the engine to drive the wheels directly.

Looking at actual figures for hybrid taxis (I use a lot of taxis) they get around 60 mpg because they recharge the battery from the mains whenever possible and generally only do short runs. Gasoline mileage on a long run without mains recharging rarely exceeds 50 mpg for a Prius, no better than a 2 liter diesel. The energetic value of a "self-charging hybrid" is in regenerative braking and short-term acceleration, hence the attraction for taxis and city driving. In a sustained cruise you are just lugging the extra weight of a dead battery. 

Fact is that you can't get something for nothing, but the tax on electricity is a lot lower than on gasoline.

[teragram (OP)]

Looking at actual figures for hybrid taxis (I use a lot of taxis) they get around 60 mpg because they recharge the battery from the mains whenever possible and generally only do short runs. Gasoline mileage on a long run without mains recharging rarely exceeds 50 mpg for a Prius, no better than a 2 liter diesel.

My apologies, I omitted the stated battery range which is 34 - 37miles.
As you say, people charge mostly from mains electricity. If you always were able to do that, you could claim the petrol consumption per 100Km to be zero.
Smoke and mirrors trickery?
Sad in my opinion that this sort of misrepresentation is allowed in advertising.

[alancalverd]

...and politics.

"Free" electricity comes at a huge cost of fossil fuel required to build, maintain and dismantle the windmills and maintain uneconomic standby plant for when the wind isn't blowing, but it's paid for by those of us who used the fuel more directly. The overall efficiency of the best thermal* power stations is no better than a small diesel engine, but the tax on their fuel is lower. Likewise the energy payback on solar panels is questionable by the time you have added a reasonable amount of storage and accounted for the limited life of batteries, but it doesn't matter in politics because all the toxic waste and coal-fired power that goes into making the kit, only poisons Chinese workers, and makes a huge profit for Chinese capitalists (who don't exist under communism, of course, but somebody somewhere is pocketing the cash and shaking hands with British ministers).

The electric car is just another bonus for the rich, subsidised by the poor. Can't wait to get mine, but it will be a hybrid with a very small battery for acceleration and braking only, powered by a gas turbine or cooking oil diesel.

*I note that the cost of Britain's next nuclear power station has just increased again. Somebody has discovered that Somerset is boggy - a fact only known to bronze-age farmers and Roman soldiers, apparently. 

[teragram (OP)]

...and politics. "Free" electricity comes at a huge cost of fossil fuel required to build, maintain and dismantle the windmills and maintain uneconomic standby plant for when the wind isn't blowing, but it's paid for by those of us who used the fuel more directly. The overall efficiency of the best thermal* power stations is no better than a small diesel engine, but the tax on their fuel is lower. Likewise the energy payback on solar panels is questionable by the time you have added a reasonable amount of storage and accounted for the limited life of batteries, but it doesn't matter in politics because all the toxic waste and coal-fired power that goes into making the kit, only poisons Chinese workers, and makes a huge profit for Chinese capitalists (who don't exist under communism, of course, but somebody somewhere is pocketing the cash and shaking hands with British ministers).The electric car is just another bonus for the rich, subsidised by the poor. Can't wait to get mine, but it will be a hybrid with a very small battery for acceleration and braking only, powered by a gas turbine or cooking oil diesel. *I note that the cost of Britain's next nuclear power station has just increased again. Somebody has discovered that Somerset is boggy - a fact only known to bronze-age farmers and Roman soldiers, apparently. 

""Free" electricity comes at a huge cost of fossil fuel required to build, maintain and dismantle the windmills and maintain uneconomic standby plant for when the wind isn't blowing, but it's paid for by those of us who used the fuel more directly."

I think we're going a bit off theme here. I don't think I implied that electricity for hybrid cars is free, merely that it's cost is not included in the consumption stats., resulting in impossible claims being allowed in advertisements.
As regards who pays for renewable  infra-structure:-

Quote from Vox.com May 2019:-
"The International Monetary Fund periodically assesses global subsidies for fossil fuels as part of its work on climate, and it found in a recent working paper that the fossil fuel industry got a whopping $5.2 trillion in subsidies in 2017. This amounts to 6.4 percent of the global gross domestic product."

From <https://www.vox.com/2019/5/17/18624740/fossil-fuel-subsidies-climate-imf>

Report in The Guardian, Jan 2019:-
"The UK leads the European Union in giving subsidies to fossil fuels, according to a report from the European commission. It found €12bn (£10.5bn) a year in support for fossil fuels in the UK, significantly more than the €8.3bn spent on renewable energy.
The commission report warned that the total subsidies for coal, oil and gas across the EU remained at the same level as 2008. This is despite both the EU and G20 having long pledged to phase out the subsidies, which hamper the rapid transition to clean energy needed to fight climate change."

House of Commons Library:_
"Taxing aviation fuel Standard Note: SN00523 Last updated: 2 October 2012 Author: Antony Seely Section Business & Transport Section 
At present, although road fuel is charged excise duty, which represents a substantial proportion of the pump price paid by motorists, aviation kerosene (AVTUR) which is used in jet engines is exempt from this tax.
Many commentators have argued that this is an indefensible anomaly, given that aviation accounts for a growing share of greenhouse gas emissions.  However, there are several obstacles to taxing aviation fuel.  First, it is probable that unilateral moves by the UK to impose duty on this category of fuel would be counterproductive, and contrary to EU law."

So another "advantage" then for the UK is that it will be able to add tax to jet fuel when we complete the process of our (self-destruction) exit from the EU. 

What is the efficiency of a small gas turbine? I seem to remember that development of the 1970's Rover gas turbine car was stopped partly because of heavy fuel consumption. Also, would the amount of waste cooking oil produced be sufficient to run all the diesel vehicles currently on the roads?
True that we have exported much of our pollution to China, largely because UK governments have continued Mrs Thatcher's policy of winding down industry in general.

[alancalverd]

AVTUR is tax-exempt everywhere by agreement of the ICAO. The EU is not the principal consumer of aviation fuel. There is a reasonable presumption that any flight from A to B will prompt a return flight from B to A. It is always desirable to arrive with minimum fuel (plus your mandatory reserve). If fuel was noticeably cheaper at B, you would overfill for the return flight to save money. But extra fuel on the ground = extra fuel consumption  en route (to lug all that fuel off the deck)  and reduces your payload capacity, so by common sense, everyone agrees to minimise the cost differential between countries.

Interestingly, although AVGAS is horrendously taxed in the UK, I can reclaim the VAT on any that I export. So it's worth filling the tank of the old Cessna (5 hours endurance) for a flight to France (1 hour each way) or Ireland. Great fun doing the paperwork for an occasional trip, but imagine the aggravation if airlines insisted on routing London-Dublin-Belfast ten times a day to save money instead of flying direct. 

If the UK taxes AVTUR, the airports will go broke. Everyone will fly to Paris or Amsterdam as a hub, use small planes to link to the UK and not buy fuel here.

Gas turbines are very efficient at constant speed, which is why they are used for ships and aircraft, and for generating electricity. The Rover gas turbine racing car needed a huge mechanical reduction gear ratio to the road wheels with a resulting heavy, inefficient gearbox. It was amazingly quiet and accelerated well, but only managed about 8 mpg due to the variable speed demand of road transport and the extra weight of the gear system and ancillary plumbing needed for a variable speed turbine.

If you can buffer a turbine-generator system with a battery, you can use modern electronic control instead of a gearbox to drive the traction motors. This is likely to power the next generation of training and general purpose aircraft where you are doing a lot of short trips, for which piston engines are currently more fuel-efficient than jets. The intermediate solution is actually aviation diesel engines running on tax-free AVTUR and driving propellors.

Road transport (and transport in general) is so important for the health and welfare of all, that taxing fuel has negligible impact on consumption - it just increases the cost of everything.

[Bored chemist]

by common sense, everyone agrees to minimise the cost differential between countries.

It's true that the differential is driven to near zero.
But if every country in the world  taxed it at the same rate their governments would make lots of money.
This would, of course, make flying more expensive.
In turn, that would reduce demand and thus reduce the consumption of aviation fuel together with the associated production of CO2.

[teragram (OP)]

If you can

AVTUR is tax-exempt everywhere by agreement of the ICAO. The EU is not the principal consumer of aviation fuel. There is a reasonable presumption that any flight from A to B will prompt a return flight from B to A. It is always desirable to arrive with minimum fuel (plus your mandatory reserve). If fuel was noticeably cheaper at B, you would overfill for the return flight to save money. But extra fuel on the ground = extra fuel consumption  en route (to lug all that fuel off the deck)  and reduces your payload capacity, so by common sense, everyone agrees to minimise the cost differential between countries.

Interestingly, although AVGAS is horrendously taxed in the UK, I can reclaim the VAT on any that I export. So it's worth filling the tank of the old Cessna (5 hours endurance) for a flight to France (1 hour each way) or Ireland. Great fun doing the paperwork for an occasional trip, but imagine the aggravation if airlines insisted on routing London-Dublin-Belfast ten times a day to save money instead of flying direct. 

If the UK taxes AVTUR, the airports will go broke. Everyone will fly to Paris or Amsterdam as a hub, use small planes to link to the UK and not buy fuel here.

Gas turbines are very efficient at constant speed, which is why they are used for ships and aircraft, and for generating electricity. The Rover gas turbine racing car needed a huge mechanical reduction gear ratio to the road wheels with a resulting heavy, inefficient gearbox. It was amazingly quiet and accelerated well, but only managed about 8 mpg due to the variable speed demand of road transport and the extra weight of the gear system and ancillary plumbing needed for a variable speed turbine.

If you can buffer a turbine-generator system with a battery, you can use modern electronic control instead of a gearbox to drive the traction motors. This is likely to power the next generation of training and general purpose aircraft where you are doing a lot of short trips, for which piston engines are currently more fuel-efficient than jets. The intermediate solution is actually aviation diesel engines running on tax-free AVTUR and driving propellors.

Road transport (and transport in general) is so important for the health and welfare of all, that taxing fuel has negligible impact on consumption - it just increases the cost of everything.

Most informative, but all this tax exemption represents a large subsidy for fossil fuel, whether locally or international, which was my point.
For the record, it seems that Rover started development of a gas turbine car at the end of World War 2, having been involved during the war in research on Frank Whittles ideas. I was not though referring to the Rover BRM racing car. Whatever machine is used, if it runs by burning stuff it is very difficult to wean it off fossil fuel.

[teragram (OP)]

This would, of course, make flying more expensive.In turn, that would reduce demand and thus reduce the consumption of aviation fuel together with the associated production of CO2.

Which would be a huge environmental advantage.

[alancalverd]

If you make flying more expensive, you increase the cost of air freight, which destroys the economy of emerging agricultural nations like Kenya and Peru and hurts the poorest in the consuming nations (like the UK).

It's somewhat bizarre logic to equate not taxing something as subsidising it. The reason electricity is affordable is because there is no tax on the fossil fuel that makes it, but there is a levy to subsidise unreliable sources. And VAT on domestic electricity, because the European Union has decided that, like tampons, it is an unnecessary luxury.

The reason Rolls Royce make jet engines is because Rover, who were granted the original licence to Whittle's patent, made a complete pig's ear of the project.

[teragram (OP)]

If you make flying more expensive, you increase the cost of air freight, which destroys the economy of emerging agricultural nations like Kenya and Peru and hurts the poorest in the consuming nations (like the UK). It's somewhat bizarre logic to equate not taxing something as subsidising it. The reason electricity is affordable is because there is no tax on the fossil fuel that makes it, but there is a levy to subsidise unreliable sources. And VAT on domestic electricity, because the European Union has decided that, like tampons, it is an unnecessary luxury.

Air fuel tax exemption must of course be ended in all countries. You could make aircraft fuel for freight tax exempt, thus protecting the economy of emerging nations, whilst removing tax exemption for passenger flights, again, internationally. This may spur more enthusiastic attempts to reduce aircraft CO2 production.
The logic that equates tax exemption with subsidy is surely that:-
Subsidies come from government funds, largely collected by taxation. Tax exemption is a subsidy by virtue of the fact that the tax money that would provide the "virtual" subsidy is not collected in the first place.

"...but there is a levy to subsidise unreliable sources."
 And very expensive ones. I remember during the last Cameron government that an "extra £1 billion was to be given to North Sea production projects for that year.

My apologies to (un)interested observers:-
The original theme has branched even further because I attempted in Reply #5 to clarify the commonly held belief that sustainable energy is the sole sink for taxpayer support for energy infrastructure.

[alancalverd]

So I must thank the government for subsidising air. I smell communism!

Aviation fuel tax is a small minefield. A significant amount of occasional high-value freight is carried on passenger flights. Around the UK, island scheduled and air taxi services carry mail, food, tourists, patients, human and veterinary pharmaceuticals, business travellers and officials. Are you suggesting that tax should be charged on each flight according to the load manifest?  Or would you rather be transferred to a mainland hospital by sailboat?

[syhprum]

Why is private medical treatment not subject to VAT ? if I send my car for service to have its life extended I am charged VAT but if I send my body to a private hospital have its life extended I am costing the pension funds money but pay no VAT. 

[alancalverd]

Because not all public health services are free of charge. If you start charging VAT on private prescriptions or cosmetic fillings you end up employing accountants and lawyers instead of pharmacists and dentists. Far simpler just to decide that some sectors are VAT-free.

I'm actually in favour of VAT. It's a small admin burden on my business but improves cash flow and, unlike all the other taxes I pay, it's unavoidable as it is based on actual turnover, not declared profit, and collected at the point of final transaction, not where the business is registered. If we abolished all other taxes and charged 40% VAT on every transaction, we could get rid of a whole raft of tax inspectors, accountants and lawyers, and encourage enterprise (no capital gains tax on investment, no corporation tax on profit, no need for PAYE and NI deductions for employees….)

[teragram (OP)]

Aviation fuel tax is a small minefield. A significant amount of occasional high-value freight is carried on passenger flights. Around the UK, island scheduled and air taxi services carry mail, food, tourists, patients, human and veterinary pharmaceuticals, business travellers and officials. Are you suggesting that tax should be charged on each flight according to the load manifest?  Or would you rather be transferred to a mainland hospital by sailboat?

So a partial solution would be to raise tax on air passenger tickets only. A substantial reduction in pollution could perhaps be achieved by encouraging fewer people to fly to other countries for stag and hen parties, weddings, visiting Disneyworld, major sporting events etc. After all it is very necessary to address the problem of aircraft emissions.

[alancalverd]

There is already an air passenger tax on flights from the UK. The remarkable fact is that if you deduct the tax, airlines can still make a profit on their lowest fares. This is due to the fuel efficiency of air transport. The actual operating cost from London to Edinburgh, once you have deducted tax and landing and handling fees, is about £10 per passenger - the price of 8 gallons of fuel, but including maintenance, depreciation, and crew wages. You might drive that distance on 8 gallons of diesel, but the Treasury mileage rate (which allows for depreciation and maintenance) works out at about £160, so even with four people in the car, the plane is more fuel-efficient, safer, and 10 times quicker. Plus, of course, it doesn't need a road and disperses its effluent high above the clouds, with negligible particulates.

Elsewhere in this forum I compared the carbon footprint of building and operating the HS2 railway (no actual track laid yet, after 6 years and some £20,000,000,000 of your money) with shifting the same number of passengers by air (start tomorrow for £20,000,000). No prizes for guessing which was cheaper and better for the environment.

[teragram (OP)]

There is already an air passenger tax on flights from the UK. The remarkable fact is that if you deduct the tax, airlines can still make a profit on their lowest fares. This is due to the fuel efficiency of air transport. The actual operating cost from London to Edinburgh, once you have deducted tax and landing and handling fees, is about £10 per passenger - the price of 8 gallons of fuel, but including maintenance, depreciation, and crew wages. You might drive that distance on 8 gallons of diesel, but the Treasury mileage rate (which allows for depreciation and maintenance) works out at about £160, so even with four people in the car, the plane is more fuel-efficient, safer, and 10 times quicker. Plus, of course, it doesn't need a road and disperses its effluent high above the clouds, with negligible particulates.

Fuel efficiency doesn't necessarily equate with Treasury mileage rate? So should we say that the aircraft is more tax-efficient, not more fuel efficient? And is the 8 gallons of fuel for £10 a special rate for air passenger travel? I currently pay over £40 for that much fuel.
Does it only cost £10 to transport a passenger 325 miles? The cheapest fare I found (not used to this) was £44

The fact is that air travel is so cheap that millions of people are able to fly frequently anywhere in the world  in large numbers, and for often frivolous reasons, across distances that would rarely be considered if land travel only was available.
I understand that aircraft consume fuel at the rate (depending on type) of 2.5 to 12 tonnes per hour. As regards specifying consumption in passenger miles per gallon, the point is that the environment doesn't care how many people have produced all that pollution, only that it has been produced.

"...disperses it's effluent high above the clouds..."
Where it has an effect apparently 2 to 4 times as bad as those dispersed at ground level.

[alancalverd]

Does it only cost £10 to transport a passenger 325 miles? The cheapest fare I found (not used to this) was £44

Yes. The airline has to pay passenger tax, navigation charges, and airport handling charges, and make a profit. As I stated, £10 is the actual cost of fuel, crew wages and aircraft maintenance and depreciation.

The fact is that air travel is so cheap that millions of people are able to fly frequently anywhere in the world  in large numbers, and for often frivolous reasons, across distances that would rarely be considered if land travel only was available.

You are required to state "purpose of travel" on immigration documents. Are you suggesting that there should be an extra tax for frivolous travel? Would anyone admit to it?  I'd happily charge £10 per mile for any passenger who spoke above 50 decibels or claimed to be a nervous/confident/frequent/novice flyer.

I understand that aircraft consume fuel at the rate (depending on type) of 2.5 to 12 tonnes per hour.

Unlikely. Mine only weighs a ton fully loaded, and will fly for about 6 hours (700 miles)  on a full tank (0.1 ton).

As regards specifying consumption in passenger miles per gallon, the point is that the environment doesn't care how many people have produced all that pollution, only that it has been produced.

All living things pollute their environment. It's a question of choice.

[teragram (OP)]

Unlikely. Mine only weighs a ton fully loaded, and will fly for about 6 hours (700 miles)  on a full tank (0.1 ton).

So 700 miles on 100 Kg = 7 miles per Kg? So scale up to a 100 tonne aircraft and passengers and that might become 0.07 mile per Kg, and at 500 mph in one hour would be 7100Kg?

It seems that a Boeing 747 (which model I don't know) consumes about one gallon of fuel per second at cruising altitude. I assume US gallons, so 3.8litrs * 3600 seconds = 13680 litres per hour, or if fuel density is 0.8Kg per litre, 0.8 * 13680 = 10944Kgs or almost eleven tonnes. I know that more modern aircraft are more efficient, but I think the 747 is still the most common amongst large aircraft.