Additional cost due to fuel consumption of a device in flight

[adgirard]

Hi everybody,

I am conducting a very simple business case of the cost of a chiller (to cool food) for an airline but I am pretty surprised by one factor which is huge.

You know that it costs something to carry weight in an aircraft, I read it is about 100 USD/kg/year.
Then, if my chiller consumes 1000 kg of fuel/year, it means it will cost me 100 000 USD/year to carry the fuel.
Whereas, the price of the fuel is only 1000 USD/year (about 1 USD/kg of Jet Fuel), and the price of the chiller is 200 USD/year.

Do I am making some mistake somewhere?

Thank you very much for your help.

Appendix:
A chiller cost less than 20 000 USD and has a lifetime greater than 10 years. Then the cost can be estimate at 200 USD/year.
A narrow body aircraft (i.e. A320) flies 2000 hours/year. If the fuel consumption of the chiller is 0.5 kg/hour (very low).

 

[mbt22]

Have you calculated the price for flying 1,000 kg around for a year, rather than the average amount of fuel on board at any one time?

Matt

 

[adgirard]

Thank you for your answer!

I am not sure I understand you perfectly.
Yes in this simple example I assume that there is always the max of fuel carried and then no fuel is consumed by the chiller, which is not true.
I wanted to keep it simple. For my study I consider a very long fly of 2000 hours (why are you laughing?!), I have thus 1000 kg of fuel FOR THE CHILLER at the take-off and 0 kg at landing. Thus, around 500 kg during the fly. But, it does not really matter, I am more focused on the method, if I am right or not.

What do you think?

 

[rb1957]

i think you're on the wrong path ... i don't think you should calculate the fuel used to carry the weight of the chiller.

if you're adding weight to the airplane, then the operator loses some useful weight ... a passenger, or some range ('cause the fuel load in the plane is reduced).

from your other thread, you've figured out the chiller consumes .5kg/hr of fuel ... so the operator has less fuel to use for range ... the range of the plane will reduce ('cause you can't carry more fuel). if a typical flight is 2hrs, the effect of losing 1 kg of fuel would be minimal on range, however the operator will have used this. so i think the .5kg/hr is the cost of operating the chiller; over a year the chiller will consume 1000 kg of fuel.

Quando Omni Flunkus Moritati

 

[adgirard]

The 100 USD/kg/year is an useful value used by salesmen (no formula behind) at my company.
It used to estimate the benefits of one technology on an other.

The A320 has a range of 6 150 km, but makes usually smaller flights (2000 km to 3000 km), it means that it does not take-off with tank fully filled.
I thus assume that it has to take more fuel if it uses the chiller or not (fuel consumed by the chiller), this increase of weight has a price (around 100 USD/kg/year).

I hope it helps a little bit.

 

[IRstuff]

There are couple of other ways to determine the cost, opportunity cost, and market cost. Opportunity cost is the lost revenue from removing the seat and passenger weight to accommodate the fridge. That can range up to $1000/flight. Alternately, you can look at how the airlines cost baggage, which is priced around $1/lb/flight, with some of it allocated to handling.

TTFN
faq731-376

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[YoungTurk]

You forgot to factor in the fuel to carry the fuel you will need to carry the fuel for the chiller.

Its turtles all the way down.

 

[rb1957]

i think you've got a reasonable story with the cost of fuel ($1000/yr) and the capital cost of the chiller ($200/yr).

what is included in the $100/kg ? if anything i'd apply it to the weight of the chiller, to account for the fuel burnt flying the chiller about (amongst other things). it does sound like an opportunity cost, rather than a real cost; in your case i don't think there's an opportunity cost, unless the chiller takes out a seat. i suspect that this chiller is going in a galley, probably replacing a galley cart ... which sounds like the weight of the chiller is off-set by the weight of the galley cart (not carried).

but then, if you're doing a business case, what's the value of having a chiller onboard ? what's the cost of the approval ? etc

Quando Omni Flunkus Moritati

 

[Compositepro]

The $100/kg/yr is probably a reasonable figure. But the weight to be counted is the weight that is going to be carried by the plane at all times during its flights. That would be the weight of the chiller and half the weight of the fuel it uses between refueling. Half is the average weight of fuel carried for the whole trip. Generally an aircraft is refueled every time it lands so it is not carrying fuel it does not need to get to the destination. Extra fuel (fuel that is not used)costs cost $100/kg/yr. Fuel that is used costs $50/kg/yr to carry. If your chiller uses 1 kg of fuel per trip then it cost $50/year.

 

[adgirard]

Compositepro I like you!

But does it is because you have the same method as I have or because you are right?
I still do not know

Anyway, you explain the same thing in a slightly different way. If someone else agree this method I will definitely keep it.

But, it is still pretty strange, because my chiller consume 1000 kg/year which means the plane carries at every moment 500 kg multiplied by 100 USD/kg/year, 50 k$!

It is a lot!

 

[dgapilot]

I guess it's a little silly to ask, but why are you running a chiller in flight? Just modify the current environmental system to cool it. When your flying along at FL 350, it's pretty cold outside!

 

[rb1957]

i imagine he's chilling some drinks, ice cream maybe. modifying the ECS would be Very difficult (IMHO) ... adding a dedicated duct for cold air, eccentially around the ECS (to avoid warming it), humidifing (or de-humidifing) it ... compared to a "plug and play" appliciance.

personally, i don't understand the "business case" ... either you want chilled drinks or you don't, the operator is paying to be able to deliver a service. now it's different if you're comparing two different means of delivering the same function, eg one is "plug and play" and consumes electricity (= fuel) and the other isn't (uses external cold air); or two appliances that consume electricity but one is more expensive and more efficient ... and i think your calcs are showing that running costs are way more significant than initial capital costs.

Quando Omni Flunkus Moritati

 

[Compositepro]

"because my chiller consume 1000 kg/year which means the plane carries at every moment 500 kg multiplied by 100 USD/kg/year, 50 k$!"

You have misunderstood. You have to convert your 1000 kg/year to kg/trip (period between refueling). If the plane makes 1000 flights/year then it is 1 kg of fuel used per trip and the annual cost of the fuel used is $50. One extra kilogram is what the plane is carrying at the beginning of the trip, not 500 kg.

 

[dgapilot]

So for an airliner, say like a 737 that's burning 5500 lbs per hour, you think they would worry about another 2.2 lbs per hour? Your chiller wouldn't use enough fuel that they would worry about it.

 

[adgirard]

Thank you rb1957

Indeed I am comparing several solution to cool during fly with the best efficiency according to the mass, the cost and the energy consumption.

Thank you Compositepro

You right the result is very different if I suppose one trip of 2000 hours or 1000 trips of 2 hours. I did it now.

dgapilot

I do not care about what an airliner consume, what I do know is if my solution consume less they will pick it, it is just logical.
For your information, 1kg/h = 2kg/flight (2 hours flight) = 200 USD/flight = 200 000 USD/year = 100 millions USD/year assuming that American Airline has 500 aircraft of this kind.

 

[rb1957]

it sounds like you're comparing an expensive more efficient unit with a less efficient cheaper one.

i don't think it's right to cost fuel as payload. i'd cost the chiller's weight as $100/kg/year and add the cost of fuel burnt and of course the cost of investment

Quando Omni Flunkus Moritati

 

[Compositepro]

"1kg/h = 2kg/flight (2 hours flight) = 200 USD/flight = 200 000 USD/year = 100 millions USD/year assuming that American Airline has 500 aircraft of this kind."

Adgirard, you still have quite got it right. 1 kg/hr for a 2 hr flight is 2 kg at the start of the flight, but only a 1 kg average payload increase for the whole flight. (The 2 kg of fuel at the start is zero at landing). That costs $100/year/aircraft, not per flight.

If you have any sense of reality and money you ought to be able to catch errors that are off by a factor of 2000. Your 100 million dollar cost savings now becomes $50,000.

 

[adgirard]

Thank you Compositepro.

You right I corrected it after my message and I founded the same things as you do.
By the way I have actually no sense of reality and money (in this field indeed) I focus more on math and logic, but one of my colleague from sale check me.

Anyway, thank you everybody I think I clarified this for my self and finally come with the right answer. I hope it may help someone else.