Improving the efficiency of diesel engines helps to reduce the fuel consumption
Improving the efficiency of diesel engines helps to reduce the fuel consumption and is on the priority list of engine makers and ship owners. A reduction of 10% or more can be achieved by a good heat recovery system, which makes use of the energy in the exhaust gases. This is not a new idea, it is more a revitalization of know-how which has been around for many years.
However, there are some obstacles that need to be overcome. What about slow steaming, how will it work under such conditions? What about the capital expenditure, is it economically viable? What if the design speed drops, is it still a good idea?
Mathematical modelling and simulation may be a good help to answer some of these questions. Three DNV researchers, based in Greece, have been working on this issue combining marine and systems engineering, and have produced a paper with a good theoretical approach to the problem.
The paper concludes that a heat recovery system on a modern container ship will increase the overall efficiency to 51,3%, running on HFO, and have a payback period of some eight years, depending on market conditions and fuel price.
Conclusions
An advanced marine combined cycle concept has been modelled and optimised for an ocean-going containership. An integrated approach to the marine energy system design was followed taking into account its overall operational profile. The system was modelled using a mathematical modelling framework, in which a modular library of reconfigurable component process models suitable for design, performance and transient operation analyses has been employed. The individual component models were calibrated and validated using measured data.
The thermoeconomic optimisation yields a significant savings potential due to the use of the combined cycle system instead of the traditional one, which consisted of a prime mover and diesel generators. The optimal system design and operation can successfully meet all operability and safety constraints imposed on a marine application.
The combined cycle system is cost-effective for a wide range of market conditions and fuel prices, with a payback period of eight years and an overall efficiency of 51.31%. This makes the combined cycle system concept particularly attractive for the present and near-future market conditions in which fuel prices are expected to increase and CO2 production (i.e. low efficiency) might be penalised.
Nikolaos Kakalis
Head of DNV Research & Innovation Greece
George Dimopoulos
Senior Researcher in DNV Research & Innovation Greece
Chara Georgopoulou
Researcher in DNV Research & Innovation Greece
Above article was initially published at DNV website.