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A worldwide trend to reduce greenhouse gases emissions has encouraged researchers to study more efficient solutions in oil and gas Industry. Most offshore units are energized by equipment operating at low loads, increasing environmental impact. This work aims identifying optimal designs and layouts of a combined cycle floating power hub tailored for offshore oil production applications. The Brazilian pre-salt basin which forecast high fuel gas production is taken as a case study. A model was developed, integrating the design of the gas turbine, heat recovery units, steam turbine and condenser. Genetic algorithms were applied in two optimization approaches, single-objective and multi-objective. Three parameters were evaluated: equipment purchase cost, thermal efficiency and total weight. The results of the multi-objective optimization indicated that dual-pressure arrangements, featuring 3 gas turbines, 1 heat recovery steam generator and 1 steam cycle, could be an attractive design solution for power hubs. This arrangement has a low cost and weight, while the thermal efficiency is maintained at a reasonably high level (around 53.2%). Moreover, results indicated that CO2 emissions may be reduced by 18.7%–27.2% at design point and 19% for the power hub lifetime, when compared with the conventional energy supply scenario. • A power hub design was optimized to improve energy efficiency in oil platforms. • Gas turbine design was integrated to comprehend more component selection scenarios. • Single-pressure and double-pressure heat recovery steam generators were considered. • All power hub scenarios resulted in lower fuel consumption and CO2 emissions. [ABSTRACT FROM AUTHOR]

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]

Organic Rankine cycle power systems represent a viable and efficient solution for the exploitation of medium-to-low temperature heat sources. Despite the large number of commissioned units, there is limited literature on the design and optimization of organic Rankine cycle power systems considering multistage turbine design. This work presents a preliminary design methodology and working fluid selection for organic Rankine cycle units featuring multistage axial turbines. The method is then applied to the case of waste heat recovery from a large marine diesel engine. A multistage axial turbine model is presented and validated with the best available data from literature. The methodology allows the identification of the most suitable working fluid considering the trade-off between cycle and multistage turbine designs. The results of the optimization of cycle and turbine suggest that the fluid n-butane yields the best compromise in terms of cycle net power output, turbine cost and efficiency for the considered case study. When a conservative design approach is adopted, the turbine features a two-stage configuration with supersonic converging nozzles and post-expansion. Conversely, a single-stage turbine featuring a supersonic converging-diverging nozzle and Mach number up to 2 is the resulting ideal choice when a more advanced design approach is implemented. [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]

Electricity and power produced from waste heat is particularly relevant in shipping because fuel expenses constitute the majority of the cost of operating the ships; however, the cost-benefit aspect limits the widespread implementation of waste heat recovery power units on ships. This paper presents the thermodynamic analysis of a concept that aims at reducing the cost of an organic Rankine cycle unit by using one of the cylinders in a large diesel engine as expansion device. Numerical models were used to optimise the process parameters and thereby determine the power potential for this concept. The evaluation of 104 working fluids points to cyclopropane, R245fa and R1234ze(z) as the most promising. The results suggest that the power produced by the organic Rankine cycle cylinder is at least equivalent to that of the cylinders operating with the diesel process. This enables potential fuel savings and emissions reductions of about 8.3% in the studied scenario. [ABSTRACT FROM AUTHOR]

The utilization of solar energy based technologies has attracted increased interest in recent times in order to satisfy the various energy demands of our society. This paper presents a thorough review of the open literature on solar energy based heat and power plants. In order to limit the scope of the review, only fully renewable plants with at least the production of electricity and heat/hot water for end use are considered. These include solar photovoltaic and solar thermal based plants with both concentrating and non-concentrating collectors in both solar-only and solar-hybrid configurations. The paper also presents a selection of case studies for the evaluation of solar energy based combined heat and power generation possibility in Denmark. The considered technologies for the case studies are (1) solar photovoltaic modules, (2) solar flat plate collectors, (3) a ground source heat pump, (4) a biomass burner, and (5) an organic Rankine cycle. The various cases are compared on the basis of economic profitability and environmental performance. The results from the case studies indicate that it is economically and environmentally beneficial to invest in both small and large capacity solar-biomass hybrid plants for combined heat and power production in the Nordic climatic conditions. The results also suggest that the configuration with an organic Rankine cycle with solar thermal collectors and a biomass burner is particularly attractive for large capacity plants. [ABSTRACT FROM AUTHOR]

Concentrating solar power plants use a number of reflecting mirrors to focus and convert the incident solar energy to heat, and a power cycle to convert this heat into electricity. This paper evaluates the use of a high temperature Kalina cycle for a central receiver concentrating solar power plant with direct vapour generation and without storage. The use of the ammonia-water mixture as the power cycle working fluid with non-isothermal evaporation and condensation presents the potential to improve the overall performance of the plant. This however comes at a price of requiring larger heat exchangers because of lower thermal pinch and heat transfer degradation for mixtures as compared with using a pure fluid in a conventional steam Rankine cycle, and the necessity to use a complex cycle arrangement. Most of the previous studies on the Kalina cycle focused solely on the thermodynamic aspects of the cycle, thereby comparing cycles which require different investment costs. In this study, the economic aspect and the part-load performance are also considered for a thorough evaluation of the Kalina cycle. A thermoeconomic optimization was performed by minimizing the levelized cost of electricity. The different Kalina cycle simulations resulted in the levelized costs of electricity between 212.2 $ MWh −1 and 218.9 $ MWh −1 . For a plant of same rated capacity, the state-of-the-art steam Rankine cycle has a levelized cost of electricity of 181.0 $ MWh −1 . Therefore, when considering both the thermodynamic and the economic perspectives, the results suggest that it is not beneficial to use the Kalina cycle for high temperature concentrating solar power plants. [ABSTRACT FROM AUTHOR]

The pollutant emissions from ships in harbor are a pressing concern due to their direct impact on the health of the population. The use of electric-battery propulsion is a viable solution to reduce the emissions in coastal areas, but it is only applicable to small ferries. Large cruise ships commonly utilize shore power connection to provide onboard electricity, avoiding pollution during harbor stays. However, this solution is not applicable during short stays. This paper presents a novel and energy-efficient way to supply zero-emission power during harbor stays of marine vessels. The proposed system combines the use of a thermal energy storage and a waste heat recovery system based on the organic Rankine cycle technology. The objective of this work is to investigate the technical feasibility of the proposed system and to compare its cost-effectiveness with the alternative solution of using batteries during harbor stays. The study is based on a case study of a hypothetical ferry requiring 1 MW of auxiliary power during harbor stays. The results suggest that the proposed system would require the installation of a storage tank of around 82 m3, and that it could be economically competitive with the battery-based solution, especially when considering its installation on newly built ships. Lastly, it is estimated that the installation of the proposed concept would lead to reduction of the ferry's carbon dioxide emissions by 8%. • Emission-free power production in harbor can be attained using the proposed concept. • The use of a stratified tank or a two-tank system leads to similar power production. • The system has the highest economic attractiveness when installed on new-built ships. • In comparison with batteries, the system is less affected by fuel price variations. [ABSTRACT FROM AUTHOR]