True Worth Index (TWI) is a measure of the thermal energy in the marine heavy residual fuel that gets converted into useful work with minimum damage to the machinery. The three parameters of the fuel that contribute towards this are
- Calorific Value - 18% contribution
- Engine Friendliness Number - 28% contribution
- Estimated Cetane Number - 54% contribution
- Calorific value of marine heavy fuel varies only around 5% between the best fuel and the worst (39 MJ/kg to 41 MJ/kg).
- Engine Friendliness number evaluates the fuel from the point of view of wear and tear and corrosion potential. This is based mainly on the ISO 8217 parameters. High EFN indicates that is more friendly to the engine and will therefore cause less wear and tear.
- The ignition and combustion properties are very important contributors to the energy that can be extracted from the fuel. If the ignition delay is too long, the combustion will not take place at the right time and there could be a power loss from the delay in the spontaneous combustion of the fuel from 10% to 25%. This is because a diesel engine derives power at the point of explosion and a delayed explosion captures only a part of the explosion power.
Viswa Lab has been providing TWI values at the Bunkerworld site since July 2002 from eight global regions where bunkering was taking place. In 2003, the number of areas was increased to 11. Three major bunkering regions, ARA, US Gulf and Singapore were given two values in view of multiple marine fuels entering the markets in these three bunkering ports. Totally in 8 regions of the world, the fuel quality was benchmarked through TWI.
In two areas, the TWI values were head and shoulders above the rest of the globe. These are Japan/Korea and Middle East/Jeddah, Saudi Arabia.
In viewing these statistics, we looked at two aspects.
- Which are the areas where the TWI benchmark was highest and which were the areas where the benchmark was lowest.
- Considering the changes in the constituents of the bunker fuel driven by regulations, has there been a drop in the average TWI over the years in any of the ports? The results are given below.
|Region||2003||2004||2005||2006||2007||2008||2009||2010||8-year Regional Average|
|Middle East TWI||59.3||66.6||66.7||68||67||66||65||67||65.7|
|ARA - high TWI||54||54.5||53||52||51||50||51||52||52.2|
|ARA - low TWI||50||48.8||50.6||48||45||47||48||49||48.3|
|Singapore - high TWI||54||53.7||52.3||54||48||49||52||51||51.8|
|Singapore - low TWI||52.3||49.2||49||52||46||45||46||46||48.2|
|U.S. Gulf - high TWI||48.3||48.9||47.4||47||49||49||47||47||48|
|U.S. Gulf - low TWI||46||46.9||44.7||46||47||43||45||44||45.3|
|U.S. Northwest TWI||51.3||50.3||51||49||49||50||51||52||50.5|
|U.S. Southeast TWI||50.7||51.4||49.1||48||49||49||47||47||48.9|
Average TWI globally for all regions was 53.0 in 2003 and 51.2 in 2010. This would mean that the average bunker quality has deteriorated between 2003 and 2010.
Here are the observations on the trend of TWI values around the globe:
- The TWI varies from region to region but in 2006, in every region there is moderate peaking of TWI values.
- Marpol Annex VI came into effect from May 19 2005, and there has been a slight drop in TWI since 2007.
- Region wise, Japan/Korea maintained a very high average of 63.9.
- The Middle East had the highest TWI average of 65.7.
- The US Gulf (consisting of Houston, NOLA etc) had the lowest TWI of 48(high) and 45.3(low).
- The ARA region has had less fluctuations in all the values over the years with a TWI average of 52.2 (high) and 48.3(low).
- Singapore TWI values dropped in 2006 and they have stayed low in the subsequent years with an average of 51.8(high) and 48.2 (low).
- Durban TWI was very low in 2003 to 2005. It slowly climbed up and it is maintaining a level of 48.8.
- In US Southeast there has been a continuous drop in TWI with the average in 2003 of 50.7 coming down to 47 in 2010.
This is an attempt to quantify fuel quality based on TWI, EFN and calorific value of the fuel. The finding of the study is given below.
Taking into consideration EFN and TWI, and the water content in the fuels in various ports and the market prices of fuels, we made a study of what the fuel is truly worth. This true worth of the fuel varied considerably (25-30%) from the market prices of the fuels. It is well known that the market price of the fuel is ONLY DICTATED BY MARKET CONDITIONS OF DEMAND AND SUPPLY. It has no connection to the quality of the fuel and the true worth of the fuel.
The Disconnect between Prices and Quality
|Bunker Port||Average Lift (mt)||Average Density (kg/m3)||Quantity Considered for Calculation (kg)||Average Water (%)||Average Water (kg)||kg Available for Combustion|
With TWI (continued)
|Bunker Port||Average Calorific Value (MJ/kg)||MJ in 1000 kg||TWI (expressed as %)||MJ Available for Work||HFO 380 cost||Dollar/MJ||MJ/Dollar|
Best Ports: Jeddah 0.0180 $/MJ and Tokyo 0.018 $/MJ
Higher Prices Paid Compare to Jeddah Taking Fuel Quality Into Account