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Highlights • The use of organic Rankine cycles on board vessels is a cost-effective solution. • Nitrogen oxides emission abatement technologies impact waste heat recovery units. • The organic Rankine cycle unit occupies less volume than a twenty-foot container. • Cyclopentane enables the attainment of the highest net present value in all cases. • The use of exhaust recirculation systems leads to the highest energy production. Abstract The International Maritime Organization recently revised the regulations concerning nitrogen and sulphur oxides emissions from commercial ships. In this context, it is important to investigate how emission abatement technologies capable of meeting the updated regulation on nitrogen oxides emissions affect the performance of waste heat recovery units to be installed on board new vessels. The objective of this paper is to assess the potential fuel savings of installing an organic Rankine cycle unit on board a hypothetical liquefied natural gas-fuelled feeder ship operating inside emission control areas. The vessel complies with the updated legislation on sulphur oxides emissions by using a dual fuel engine. Compliance with the nitrogen oxides emission regulation is reached by employing either a high or low-pressure selective catalytic reactor, or an exhaust gas recirculation unit. A multi-objective optimization was carried out where the objective functions were the organic Rankine cycle unit annual electricity production, the volume of the heat exchangers, and the net present value of the investment. The results indicate that the prospects for attaining a cost-effective installation of an organic Rankine unit are larger if the vessel is equipped with a low-pressure selective catalytic reactor or an exhaust gas recirculation unit. Moreover, the results suggest that the cost-effectiveness of the organic Rankine cycle units is highly affected by fuel price and the waste heat recovery boiler design constraints. [ABSTRACT FROM AUTHOR]

The Kalina cycle has recently seen increased interest as an alternative to the conventional steam Rankine cycle. The cycle has been studied for use with both low and high temperature applications such as geothermal power plants, ocean thermal energy conversion, waste heat recovery, gas turbine bottoming cycle, and solar power plants. The high temperature cycle layouts are inherently more complex than the low temperature layouts due to the presence of a distillation-condensation subsystem, three pressure levels, and several heat exchangers. This paper presents a detailed approach to solve the Kalina cycle in part-load operating conditions for high temperature (a turbine inlet temperature of 500 °C) and high pressure (100 bar) applications. A central receiver concentrating solar power plant with direct vapour generation is considered as a case study where the part-load conditions are simulated by changing the solar heat input to the receiver. Compared with the steam Rankine cycle, the Kalina cycle has an additional degree of freedom in terms of the ammonia mass fraction which can be varied in order to maximize the part-load efficiency of the cycle. The results include the part-load curves for various turbine inlet ammonia mass fractions and the fitted equations for these curves. [ABSTRACT FROM AUTHOR]

In this paper, we present an assessment of methods for estimating and comparing the thermodynamic performance of working fluids for organic Rankine cycle power systems. The analysis focused on how the estimated net power outputs of zeotropic mixtures compared to pure fluids are affected by the method used for specifying the performance of the heat exchangers. Four different methods were included in the assessment, which assumed that the organic Rankine cycle systems were characterized by the same values of: (1) the minimum pinch point temperature difference of the heat exchangers; (2) the mean temperature difference of the heat exchangers; (3) the heat exchanger thermal capacity ( U ¯ A ); or (4) the heat exchanger surface area for all the considered working fluids. The second and third methods took into account the temperature difference throughout the heat transfer process, and provided the insight that the advantages of mixtures are more pronounced when large heat exchangers are economically feasible to use. The first method was incapable of this, and deemed to result in optimistic estimations of the benefits of using zeotropic mixtures, while the second and third method were deemed to result in conservative estimations. The fourth method provided the additional benefit of accounting for the degradation of heat transfer performance of zeotropic mixtures. In a net power output based performance ranking of 30 working fluids, the first method estimates that the increase in the net power output of zeotropic mixtures compared to their best pure fluid components is up to 13.6%. On the other hand, the third method estimates that the increase in net power output is only up to 2.56% for zeotropic mixtures compared to their best pure fluid components. [ABSTRACT FROM AUTHOR]