> Such schemes used to be thwarted by the difficulty of measuring exact fuel consumption on ships. New technologies allow more accurate readings.
Why is it so difficult to measure fuel consumption on ships?
Why is it so difficult to measure fuel consumption on ships?
I only worked with Diesel, not HFOs.
Due to the rocking of the ship, it's hard to get an accurate reading of the fuel in the tanks. Fuel is transferred from storage tanks to a day tank, and a fuel meter can be used for that, but that only tells you how much you transferred, not how much you consumed. Unless you always fill the day tank to the exact same level (remember, hard to measure at sea) and at the same time each day, you won't know exactly how much was burned in a 24 hour period. And of course fuel consumption changes based on the ships speed.
This is a good, short explanation on how we measure tanks on ships: http://benvalle.com/Level.html
Edit: there is probably a lot of money to be made if someone can come up with a very accurate tank measuring method. I've seen some tanks use ultrasound to detect the level in a sounding tube, but sometimes those can be distorted if the "liquid" sticks to the sensor. Maybe some kind of 3d mapping? However not all tanks have an unabstructed free surface in order to prevent the free surface effect from capsizing the ship: https://en.wikipedia.org/wiki/Free_surface_effect
2nd edit: Maybe not, since measuring at sea isn't as important as measuring in port when the ship is not rocking and the products are being transferred to/from ship. I'll leave the first edit since it might be interesting to people.
Would it not be possible to install a flow rate monitor between the engine and the day tank? If so it would be possible to estimate with okay precision flue usage for any given time period.
I Apologize for the naive question, because I imagine there's a reason it isn't done already.
I've only been on one ship built in the last decade that had that, and you could read the number on a computer screen. (FYI, the computer systems and automation on ships are a joke, if you can do it better than the current companies, you could make some money. Also, tangentially related to why we'll never have fully-automated ships. Stuff breaks, and ships lose money every day they're in port for repairs.)
However not all fuel that goes to the engine ends up being burned. Fuel is always being pumped through the fuel line at a high pressure, and only a fraction of that is burned when the cam system actuates the injectors to inject fuel into the engine cylinders. The rest of the fuel is returned to the tank.
As for the ship I was on that had a more accurate measurement, I don't know exactly what was measured. I can only speculate it was the fuel in minus the fuel out.
It's up to the Chief Engineer if he/she wants to use an Excel spreadsheet to track fuel consumption (and most probably do). As for tracking it based on weight, maybe some chiefs do that, but I imagine it's not worth it for most.
I wasn't a chief, so I don't know what their responsibilities are in regards to fuel consumption. But I imagine they would have to give estimates of future fuel needs to the company based on the ship's schedule.
For the purposes of this article, it would be sufficient to measure how much fuel you transferred during a calendar year, and that's about as much as you consumed. The particular level of the day tank can be ignored as it won't even make a 1% difference to the total amount
For car fuel consumption, most countries can simply count the sales of gasoline and diesel, which are regulated and taxed so they know the total amount sold, and report reasonably accurate official statistics of total countrywide fuel consumption.
Ships move around jurisdictions, refuel whenever and wherever convenient, and it's hard to get the whole picture unless each ship reports to you what it consumed - and noone can unilaterally require that, as ships are under different jurisdictions; unless a requirement is included in one of the large international agreements, most ships can ignore it most of the time.