Abstract
The study examines the option of adding a bottom Organic Rankine Cycle (ORC) for energy recovery from an internal combustion engine (ICE) for ship propulsion. In fact, energy recovery from the exhaust gas normally rejected to the atmosphere and eventually from the cooling water circuit (usually rejected to the sea) can significantly reduce the fuel consumption of a naval ICE during its operation. In the paper, different possible bottom ORC configurations are considered and simulated using the Aspen® code. Different working fluids are taken into account, jointly with regenerative and two-temperature levels designs. The energy recovery allowed by each solution is evaluated for different engine load, allowing the identification of the most suitable ORC configuration. For the selected case, the preliminary design of the main heat exchangers is carried out and the off-design performance of the whole combined propulsion plant (ICE + ORC) is evaluated, leading to a preliminary analysis of cost saving during normal ship operation. The results of this analysis show an increase in power output of about 10% and an expected Payback Time of less than 6 years.
Highlights
The today’s cost of fossil fuels is constantly evolving
In recent years, polluting emissions produced by merchant ships have to be contained in increasingly restrictive limits to comply with the new regulations coming in force [1]
This study examines the options of energy recovery from an internal combustion engine (ICE) for ship propulsion by adding a bottom Organic Rankine Cycle (ORC), with the aim of reducing the fuel consumption of the propulsion system during its operation
Summary
The today’s cost of fossil fuels is constantly evolving. The present economic crisis, combined with political pressures, make the price of oil strongly uncertain. From the point of view of increasing the whole efficiency of the propulsion system, energy recovery can be considered of the waste heat usually dissipated, for both improving the propulsion power or for producing useful heat on board the ship [6,7,8,9,10] In this context, the use of Organic Rankine Cycles (ORC). The proposed analysis is based on the real operating data of a marine engine, considering the needs of its cooling system, and on the use of a realistic design/off-design simulator of the heat exchangers, available in Aspen® In this way the expectation is to obtain very realistic values of the actual performance increase of the propulsion system. A search for optimal solutions to meet the entire energy demand on board of a cruise ship is presented for example in [28]
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