Techno-economic environmental and risk assessment for large container ship gas turbine combined cycle propulsion systems

Abstract

In recent years, the International Maritime Organization’s (IMO) stringent regulations on air pollutants, which are associated with increased fuel costs, have encouraged researchers to develop fuels and technologies that are cleaner and more efficient than conventional propulsion systems. This study defines and describes a techno-economic environmental and risk assessment (TERA) method for assessing substitute fuels and technologies that could be utilised in the maritime sector to replace two-stroke diesel engines fuelled by heavy fuel oil (HFO). This study aimed to develop a TERA method for marine technologies and to improve Cranfield University’s ship resistance simulation code, “Poseidon”. The study examined conventional propulsion systems, such as two-diesel engines fuelled by marine diesel oil and gas and steam combined cycle fuelled by liquefied natural gas and marine diesel fuel. The characteristic cryogenic properties of liquefied natural gas were employed to improve the efficiency of the combined cycle gas turbine cycles. The study selection criteria were performance, emissions, weight, and investment costs, including installation, operation, and maintenance costs for advanced combined gas and steam turbine cycles and two-stroke diesel engine propulsion systems for large container ships. A risk assessment was conducted to evaluate the impacts of capital cost, fuel cost, hull fouling resistance, container shipment price, discount rate, and emission taxation on the economic analysis. The results indicated that enhanced LNG combined cycles were the most efficient. Their enhanced combined cycle efficiency was 11% higher than two-stroke diesel engine efficiency and they reduced nitrogen oxide and carbon dioxide emissions by 76.3% and 44.7%, respectively. Regarding the weight of the propulsion systems, the combined gas and steam turbine propulsion system was approximately 24.7% lighter than the diesel engine propulsion system. For the routes that were considered and compared to a two-stroke diesel engine fuelled by MDO, the simple, intercooler/reheat, and enhanced gas and steam combined cycles that were fuelled by LNG increased the net present value by 78.3%, 78.5%, and 76.4%, respectively, and the payback period was reduced by 38.8%, 38.9%, and 35%, respectively. Additionally, the IRR showed a low-risk investment with significant potential benefits of CCGT cycles fuelled with LNG. The discount rate, container price, capital cost, emissions tax, and fuel cost scenarios showed the highest impact on economic results compared with the other scenarios for all technologies. The TERA was performed for different routes to evaluate the benefits and disadvantages of installing combined cycles instead of two-stroke diesel engines.