[Justin Aerial]

Originally Posted by flagpole

back of the envelope calculation:

lets say travelling at 70mph requires 50hp
power goes with the square of velocity (over the same distance) so 90mph equivalence is 83hp

they sound like reasonable numbers.

a petrol engine is about 25% efficient and 1hp ~750W
so you have cruising at 70mph 150kW
and doing the same journey at 90mph (accounting for it taking less time) 247kW

which is a whole lot of energy like 100kWh per hour driven at 70mph more. a lot of light bulbs.

however, having energy saving light bulbs still saves that energy.

But fuel consumption [i.e. energy used] is measured in mpg, which is the amount used per mile, so the fact the journey may or may not take less time (I generally more or less catch up most speeding drivers by the next set of traffic lights.....) is surely irrelevant for the purposes of this energy efficiency calculation ?

[John146]

Bit of a no brainer this saving electricity with energy saving bulbs, when/if I turn on all the lights in the 'job' I have we burn 48,000 watts,(at least) and to the best of my knowledge there are no energy saving bulbs available that would cut that wattage down.

[samsung29]

Utility companies are no longer allowed to send out free energy light bulbs to customers as the government banned it.
They sent them out to meet targets set by the government in relation to reducing carbon footprint etc.
Some time later apparantly the government realised that. although all these light bulbs were being sent out, a lot of people were not using them and just putting them in a cupboard so nothing was being acheived. Just saying

[Si_Crewe]

Originally Posted by Justin Aerial

But fuel consumption [i.e. energy used] is measured in mpg, which is the amount used per mile, so the fact the journey may or may not take less time (I generally more or less catch up most speeding drivers by the next set of traffic lights.....) is surely irrelevant for the purposes of this energy efficiency calculation ?

Not really.

If you do 90mph in order to get somewhere then you'll get there quicker and that should be factored into any calculation.

Doing so on the basis of kwh is a bare minimum for that purpose.

If you were simply looking at the difference between running a car perpetually at 90mph rather than 70mph it wouldn't manner but if you're looking at a finite journey then it's a valid factor.

[flagpole]

Originally Posted by Justin Aerial

But fuel consumption [i.e. energy used] is measured in mpg, which is the amount used per mile, so the fact the journey may or may not take less time (I generally more or less catch up most speeding drivers by the next set of traffic lights.....) is surely irrelevant for the purposes of this energy efficiency calculation ?

it is. but the OP wanted it in terms of light bulbs so i thought it made sense to do the calculation in BHP and convert to kW. the only way i know how to compare gallons of petrol to light bulbs. it's because we are working in rate of energy consumption that the confusion arises.

the actual specific rate of fuel consumption in say gallons per minute goes with the cube of velocity, (roughly,) by going with the square you take out one of those factors which accounts for the increased speed. i actually chose my language quite carefully because i was expecting someone who knew that to point out my sloppy shortcut. which i guess left me open to the opposite question.

the ballpark figure of an extra 100kW is going to be reasonably accurate for a petrol car. unless you have another way of looking at it?

[Justin Aerial]

I just phoned up Rover and they said they weren`t allowed "by law" to reveal any fuel consumption figures than the official ones, so I don`t actually think I`m going to find the answer to this question. This is why I like doing my own research which is what first started me doing all my tests on aerials and poles etc, you simply couldn`t find out that info, contrary to popular belief you can`t actually find out everything on the internet. Anyway I`m obviously not prepared to buy a Range Rover just to find out its consumption at 70mph and 90mph, oh yes, and I wouldn`t be able to find out without breaking the law anyway, 90mph being 20mph over the speed limit......

[Justin Aerial]

Originally Posted by Si_Crewe

Not really.

If you do 90mph in order to get somewhere then you'll get there quicker and that should be factored into any calculation.

Doing so on the basis of kwh is a bare minimum for that purpose.

If you were simply looking at the difference between running a car perpetually at 90mph rather than 70mph it wouldn't manner but if you're looking at a finite journey then it's a valid factor.

Don`t understand what you`re saying to be honest. If a car does 30mpg at 70mph that means it uses up one gallon in 30 miles, if it does 15mpg at 100mph that means it uses up one gallon in 15 miles.

[KarlSomething]

Everything we do matters. If you're able to give up the car entirely, do that. And don't have too many pets, it takes resources to feed those as well. As it does kids, though at least those kids will grow up to become productive members of society. Although since most of us in the west spend resources at too great a rate, yeah, we'd be better off having fewer kids.

As they would where they're already starving, of course. We need to ship out some birth control along with the other aid.

[flagpole]

Originally Posted by Justin Aerial

Don`t understand what you`re saying to be honest. If a car does 30mpg at 70mph that means it uses up one gallon in 30 miles, if it does 15mpg at 100mph that means it uses up one gallon in 15 miles.

read my answer in post 30.

if you have a way to convert 30mpg in to a rate of energy consumption in the same units as that printed on a light bulb then we'll do it your way.

(I quick hint would be that there is no way.)

[Justin Aerial]

Originally Posted by flagpole

read my answer in post 30.

if you have a way to convert 30mpg in to a rate of energy consumption in the same units as that printed on a light bulb then we'll do it your way.

(I quick hint would be that there is no way.)

Sorry, maybe I was being unclear. What I meant was the energy equivalence. That is to say the amount of extra fuel, (which can surely be converted into energy use from its calorific value) used by the Range Rover at 90mph over 100miles compared with the amount used at 70mph over 100miles. Then how long would that energy light a 23W high efficiency bulb, then double it because what we`re interested in is the saving over an incandescent (which `im prepared to accept, in this country over the course of a year, including spring/winter/autumn) is half the efficiency, though I would possibly dispute even that figure, but let`s not get sidetracked.......
An alternative and somewhat simpler approach would be to calculate the cost savings which would probably amount an approximation of the same answer.
Bobs your Uncle.
However, for either of these we need to know the fuel consumption at 70 and 90 mph, which, if we can`t find out, makes it all a bit irrelevant.

[Si_Crewe]

Originally Posted by Justin Aerial

Don`t understand what you`re saying to be honest. If a car does 30mpg at 70mph that means it uses up one gallon in 30 miles, if it does 15mpg at 100mph that means it uses up one gallon in 15 miles.

A car that uses a given amount of energy will use it for a given length of time.
At different speeds the time will be different so that should be factored into any calculations.

For example, on a 200 mile trip let's say a car uses 50hp to maintain 70mph and 83hp to maintain 90mph

That's 2.85 hours at 70mph and 2.2 hours at 90mph.

So, the car us using 37kw of energy for 2.85 hours at 70mph or using 62kw of energy for 2.2 hours at 90mph.

Thus, at 70mph the 200 mile journey uses 105kwh of energy while at 90mph it uses 136kwh of energy.

Even though the car is using roughly 40% more power at 90mph the total energy used is only 25% more due to the shorter journey time.

And, of course, you get where you're going quicker, which if you're on your way somewhere important might have far bigger cost implications.

[flagpole]

Originally Posted by Justin Aerial

Sorry, maybe I was being unclear. What I meant was the energy equivalence. That is to say the amount of extra fuel, (which can surely be converted into energy use from its calorific value) used by the Range Rover at 90mph over 100miles compared with the amount used at 70mph over 100miles. Then how long would that energy light a 23W high efficiency bulb, then double it because what we`re interested in is the saving over an incandescent (which `im prepared to accept, in this country over the course of a year, including spring/winter/autumn) is half the efficiency, though I would possibly dispute even that figure, but let`s not get sidetracked.......
An alternative and somewhat simpler approach would be to calculate the cost savings which would probably amount an approximation of the same answer.
Bobs your Uncle.
However, for either of these we need to know the fuel consumption at 70 and 90 mph, which, if we can`t find out, makes it all a bit irrelevant.

yep. you do. i'm not disputing that there are other ways of working this out. i'm just explaining why my way is valid, and why i did it that way.

if anyone has another theory i'd like to hear it.

[Justin Aerial]

Actually, I`ve just realised why so many people speed on the motorways and don`t seem to be bothered how much it`s costing them (talk about something being obvious and not actually realising it), it`s because most of them aren`t actually paying for it (because they`re company cars) !
It does make me wonder why companies don`t introduce bonus/fine systems for economical driving, the fact that economical driving is usually safe driving just makes it even more hard to fathom why so few (if any) ever bother.
Let`s face it it`d be pretty easy to find out how economically employees were driving, just work out the average mpg.....

[Si_Crewe]

Originally Posted by Justin Aerial

Actually, I`ve just realised why so many people speed on the motorways and don`t seem to be bothered how much it`s costing them (talk about something being obvious and not actually realising it), it`s because most of them aren`t actually paying for it (because they`re company cars) !
It does make me wonder why companies don`t introduce bonus/fine systems for economical driving, the fact that economical driving is usually safe driving just makes it even more hard to fathom why so few (if any) ever bother.
Let`s face it it`d be pretty easy to find out how economically employees were driving, just work out the average mpg.....

Firstly, I've yet to see any company issue Range Rovers to employees.

Secondly, lots of companies DO employ systems to persuade drivers to be economical.
They have little beepy boxes built into the vehicles to make your life a misery if you accelerate or steer quickly or break the speed limit.

[alias alias]

Time is money, the next meeting down the motorway likely easily covers the extra cost of petrol more meetings in a day the more commission or bonuses they get.

If the difference between 70mph and 90mph at 2.2 hour is...19kwh

light bulb 100 watts 730 hours (i.e., all month) 73 kWh

CFL light bulb 25 watts 730 hours(i.e., all month) 18 kWh

[RobinOfLoxley]

deleted

[Justin Aerial]

Originally Posted by alias alias

Time is money, the next meeting down the motorway likely easily covers the extra cost of petrol more meetings in a day the more commission or bonuses they get.

If the difference between 70mph and 90mph at 2.2 hour is...19kwh

light bulb 100 watts 730 hours (i.e., all month) 73 kWh

CFL light bulb 25 watts 730 hours(i.e., all month) 18 kWh

That seems surprisingly low (19kWH to do 90mph rather than 70 mph for over 2 hours) where do you get those figures ? What sort of car would that be, it surely wouldn`t a big 4WD ? ! ?

[exlordlucan]

Low energy bulbs are more energy efficient than the old ones.

Today's 4x4's are more energy efficient than the old ones.

[spiney2]

yeah! recycle coke cans and then jet off into the sun for your winter holiday ........ sit there basking under outdoor gas heaters despite the sunshine ......

....... most cars are most economical when constantly driven about 25 mph but i daresay that wd muck up traffic flow a wee bit .......

[spiney2]

...... today's iphones are more energy efficient than 10 year old ones ......

[Ghengis Can]

Originally Posted by spiney2

yeah! recycle coke cans and then jet off into the sun for your winter holiday ........ sit there basking under outdoor gas heaters despite the sunshine ......

....... most cars are most economical when constantly driven about 25 mph but i daresay that wd muck up traffic flow a wee bit .......

I don't have a company car, I have a company bike, and my own van. The van is pretty unsophisticated, but the bike is all fuel injected and computerised, fly by wire throttle, and has a fuel consumption indicator. It's a bit slow to respond, but I can assure you that 25mph is a hiding to nothing on fuel economy. It shows about 70MPG at 55mph, and about 30MPG at 25mph. 56MPG at a constant 70. I expect it falls off a cliff after that, but how would I know? I'd expect most cars to mirror that. 25mph is not an economical speed.

[Caldari]

What does the drivetrain of a vehicle have to do with anything?

[Ghengis Can]

Originally Posted by Caldari

What does the drivetrain of a vehicle have to do with anything?

You lose efficiency with more parts. There is drag in the drivetrain of a 4x4 of any sort. I daresay in mine there's quite a bit, it being a 2.5 County LR. Permanenet 4wd is supposed to be at least as efficient as 2wd, but it's not, in practice.

[RobinOfLoxley]

3x3s are a good compromise.

[Caldari]

Originally Posted by Ghengis Can

You lose efficiency with more parts. There is drag in the drivetrain of a 4x4 of any sort. I daresay in mine there's quite a bit, it being a 2.5 County LR. Permanenet 4wd is supposed to be at least as efficient as 2wd, but it's not, in practice.

I know, I was just wondering why they chose the tired old 'lets jump on anything 4x4' bandwagon rather than using something different this time, like say a dirty great lump of Detroit 448ci V8 for example.

Nice choice on the County though, I've a Defender 110 Td5 myself.