Comparison In order to show the true revenue making potential of gas turbine driven LNGC alternatives, they have to be compared with the current state-of-the-art conventional LNGC. First of all, on the basis of many contact with the LNG shipping community the most likely LNGC configuration was selected on the basis of technological merits. Initially, calculations showed the gas turbine electric podded drive LNGC to have the best revenue making capacity, with its high cargo capacity and highly efficient propulsion system. However, in the light of recent events involving podded drive failures, it seems that the reliability of these systems does not yet comply with the requirements of the LNG shipping industry. The next best alternative, the gas turbine mechanical drive LNGC offers unsurpassed thermal efficiency and high cargo capacity. However, the durability of the reduction gear, clutches and reversing gear for the FPP in commercial marine application is as yet unknown. Some owners have voiced objections to an alternative equipped with a CPP, citing its slightly lower propulsion efficiency. The gas turbine electric drive LNGC combines excellent thermal efficiency and high cargo capacity, paired with the use of proven technology in the power train. Electric drive systems have gained some acceptance within the LNG shipping community, as illustrated by the order for one 74,000 cubic meter diesel-electric drive LNGC at Chantiers de l'Atlantique last year. Reliability, redundancy and revenue are the key words to this propulsion alternative. To check the economic viability of the gas turbine electric drive LNGC, a cost calculation model has been designed using a range of input parameters to calculate long run economic performance under differing circumstances and on different trading routes. Three LNG trades are simulated; the short trade (Algeria - France), the medium trade (Trinidad - Spain) and the long trade (Qatar - Korea/Japan). Two different liquid fuel price levels, representing the extremes of the last ten years, have been used to check the survivability of the gas turbine drive alternatives in changing economic circumstances. Six different aero-derivative gas turbines configuration have been selected to take part in the comparison, making this study the first full-scale performance comparison of all major aero-derivative gas turbine makes for commercial marine propulsion.
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Voyage Parameters | Short | Medium | Long | Itinerary |
Voyage Length | 1,5 | 5,0 | 14,0 | days |
Maneuvering | 0,125 | days | ||
Loading Time | 1,00 | days | ||
Off-loading Time | 1,00 | days | ||
Non-workable Days Per Year | 5 | days | ||
Cargo Capacities LNGC Alternatives | ||||
Gas Turbine Mechanical Drive LNGC | 157 000 | cubic meter | ||
Gas Turbine Electric Drive LNGC | 157 000 | cubic meter | ||
Gas Turbine Electric Podded Drive LNGC | 160 000 | cubic meter | ||
Conventional Steam Turbine Driven LNGC | 138 000 | cubic meter | ||
Technical Parameters | ||||
Effective Capacity | 98,5% | of the nominal cargo capacity | ||
Boil Off Fraction when Loaded | 0,15% | of cargo volume / 24 h | ||
Boil Off Fraction when in Ballast | 0,04% | of cargo volume / 24 h | ||
Gas/Liquid ratio | 618.1 | |||
LNG Density | 475 | kg/m3 | ||
LNG LHV | 48
422 | kJ/kg | ||
MGO LHV | 42
700 | kJ/kg | ||
HFO LHV | 41
200 | kJ/kg | ||
Propulsion Load when Loaded | 26
000 | kW | ||
Propulsion Load in Ballast | 23
500 | kW | ||
Maneuvering Load | 5
000 | kW | ||
Sea Load | 1
200 | kWe | ||
Harbor Load | 1
500 | kWe | ||
Cargo Loading Load | 2
400 | kWe | ||
Cargo Discharging Load | 4
500 | kWe | ||
Fuel Gas Compressor Load when Loaded | 1
500 | kWe | ||
Fuel Gas Compressor Load in Ballast | 1
200 | kWe | ||
Gearbox Efficiency | 98% | |||
Frequency Converter Efficiency | 98% | |||
Electric Motor Efficiency | 98% | |||
Shafting Efficiency | 99% | |||
Boiler Efficiency | 88% | |||
Steam Turbine Efficiency | 35% | |||
HRSG in Fired Boiler Mode Efficiency | 80% | |||
Steam Turbine Generator Efficiency | 25% | |||
Podded Drive Propulsion Efficiency Increase | 5% | |||
Financing Parameters | ||||
Capital cost | 12,00% | per year | ||
Economic lifespan | 20,0 | years | ||
Financing cost | 10,00% | of contract value | ||
Pre-delivery cost | 3,50% | of contract value | ||
Residual value | $15
000 000 | |||
Bunker Price Level | Low | High | ||
HFO380 | $70,00 | $180,00 | per ton | |
MGO | $150,00 | $310,00 | per ton | |
LNG Pricing | Short | Medium | Long | Itinerary |
LNG FOB | $2,30 | $2,30 | $2,30 | /MMBTU |
LNG CIF | $2,80 | $3,10 | $3,65 | /MMBTU |
Operational Parameters | ||||
Crew Cost | $13
000 | per day | ||
Harbour Dues | $100
000 | per arrival | ||
P&I | $1
500 | per day | ||
Miscellaneous | $1
000 | per day | ||
Maintenance Budget | ||||
Conventional LNGC | $3
000 | per day | ||
Gas turbine maintenance surcharge | ||||
| $60 | per fired hour | ||
| $60 | per fired hour | ||
| $60 | per fired hour | ||
| $80 | per fired hour | ||
| $80 | per fired hour | ||
| $60 | per fired hour |
Three alternative fuel schedules have been used in this comparison:
The results are presented in the diagrams below: Long itinerary High (left) v/s Low (right) Liquid Fuel Prices Medium Itinerary High (left) v/s Low (right) Liquid Fuel Prices
Short Itinerary High (left) v/s Low (right) Liquid Fuel Prices There are a number of preliminary conclusion to be drawn:
Additional calculations show that, under certain circumstances, it is economically feasible to re-engine a conventional LNGC with a gas turbine electric drive power plant incorporating gas turbine types GT1, GT2, GT3 or GT6, even if the cargo capacity is not increased. However, the conversion should take place early in the charter for the conversion to be profitable and the vessel will not have the same flexibility and high ROI as LNGCs especially designed to exploit the benefits of gas turbine propulsion to the maximum. More information on the gas turbine types and configurations can be obtained from MPT Consultancy. |