| 1. |
- Andreasen, J. G., et al.
(författare)
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Design and optimization of a novel organic Rankine cycle with improved boiling process
- 2015
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Ingår i: Energy. - : Elsevier BV. - 0360-5442. ; 91, s. 48-59
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we present a novel organic Rankine cycle layout, named the organic split-cycle, designed for utilization of low grade heat. The cycle is developed by implementing a simplified version of the split evaporation concept from the Kalina split-cycle in the organic Rankine cycle in order to improve the boiling process. Optimizations are carried out for eight hydrocarbon mixtures for hot fluid inlet temperatures at 120 °C and 90 °C, using a genetic algorithm to determine the cycle conditions for which the net power output is maximized. The most promising mixture is an isobutane/pentane mixture which, for the 90 °C hot fluid inlet temperature case, achieves a 14.5% higher net power output than an optimized organic Rankine cycle using the same mixture. Two parameter studies suggest that optimum conditions for the organic split-cycle are when the temperature profile allows the minimum pinch point temperature difference to be reached at two locations in the boiler. Compared to the transcritical organic Rankine cycle, the organic split-cycle improves the boiling process without an entailing increase in the boiler pressure, thus enabling an efficient low grade heat to power conversion at low boiler pressures.
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| 2. |
- Andreasen, J. G., et al.
(författare)
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Design of organic Rankine cycles using a non-conventional optimization approach
- 2015
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Ingår i: Proceedings of ECOS 2015 : 28th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems. - 9782955553909
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Konferensbidrag (refereegranskat)abstract
- The organic Rankine cycle is a suitable technology for utilizing low grade heat for electricity production. Compared to the traditional steam Rankine cycle, the organic Rankine cycle is beneficial, since it enables the choice of a working fluid which performs better than steam at low heat input temperatures and at lowpower outputs. Selecting the process layout of the organic Rankine cycle and the working fluid are two key design decisions which are critical for the thermodynamic and economic performance of the cycle. The prevailing approach used in the design and optimization of organic Rankine cycles is to model the heatexchangers by assuming a fixed minimum temperature difference. The objective of this work is to assess the applicability of this conventional optimization approach and a non-conventional optimization approach. In thenon-conventional optimization approach a total UA-value (the product of the overall heat transfer coefficient and the heat transfer area) is assigned to the cycle, while the distribution of this total UA-value to each of the heat exchangers is optimized. Optimizations are carried out for three different marine engine waste heatsources at temperatures ranging from 90 °C to 285 °C. The results suggest that the conventional optimization approach is not suitable for estimating the performance potential when the temperature profiles in the heat exchangers are closely matched. This is exemplified for the fluid MDM where the temperature profile of preheating aligns with the heat source fluid and for the zeotropic mixture R32/R134a where the temperature profile of condensation aligns with the cooling water. Furthermore, the conventional optimization approach shows weaknesses in evaluating the feasibility of using a recuperator, when the expander outlet temperature is high. In these cases the non-conventional optimization approach is the more suited methodology for designing organic Rankine cycles.
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| 3. |
- Andreasen, Jesper Graa, et al.
(författare)
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Multi-Objective Optimization of Organic Rankine Cycle Power Plants Using Pure and Mixed Working Fluids
- 2016
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Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 9:322
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Tidskriftsartikel (refereegranskat)abstract
- For zeotropic mixtures, the temperature varies during phase change, which is opposed to the isothermal phase change of pure fluids. The use of such mixtures as working fluids in organic Rankine cycle power plants enables a minimization of the mean temperature difference of the heat exchangers, which is beneficial for cycle performance. On the other hand, larger heat transfer surface areas are typically required for evaporation and condensation when zeotropic mixtures are used as working fluids. In order to assess the feasibility of using zeotropic mixtures, it is, therefore, important to consider the additional costs of the heat exchangers. In this study, we aim at evaluating the economic feasibility of zeotropic mixtures compared to pure fluids. We carry out a multi-objective optimization of the net power output and the component costs for organic Rankine cycle power plants using low-temperature heat at 90 ◦C to produce electrical power at around 500 kW. The primary outcomes of the study are Pareto fronts, illustrating the power/cost relations for R32, R134a and R32/R134a (0.65/0.35mole). The results indicate that R32/R134a is the best of these fluids, with 3.4 % higher net power than R32 at the same total cost of 1200 k$.
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| 4. |
- Andreasen, J. G., et al.
(författare)
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Multi-objective optimization of organic Rankine ycle power plants using pure and mixed working fluids
- 2015
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Ingår i: Proceedings of ASME ORC 2015. ; , s. 11-
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Konferensbidrag (refereegranskat)abstract
- For zeotropic mixtures, the temperature varies during phase change, which is opposed to the isothermalphase change of pure fluids. The use of such mixtures as working fluids in organic Rankine cyclepower plants enables a minimization of the mean temperature difference of the heat exchangers whenthe minimum pinch point temperature difference is kept fixed. A low mean temperature differencemeans low heat transfer irreversibilities, which is beneficial for cycle performance, but it also results inlarger heat transfer surface areas. Moreover, the two-phase heat transfer coefficients for zeotropic mixturesare usually degraded compared to an ideal mixture heat transfer coefficient linearly interpolatedbetween the pure fluid values. This entails a need for larger and more expensive heat exchangers. Previousstudies primarily focus on the thermodynamic benefits of zeotropic mixtures by employing firstand second law analyses. In order to assess the feasibility of using zeotropic mixtures, it is, however,important to consider the additional costs of the heat exchangers. In this study, we aim at evaluatingthe economic feasibility of zeotropic mixtures compared to pure fluids. We carry out a multi-objectiveoptimization of the net power output and the component costs for organic Rankine cycle power plantsusing low-temperature heat at 90 ◦C to produce electrical power at around 500 kW. The primary outcomesof the study are Pareto fronts, illustrating the power/cost relations for R32, R134a and R32/R134a(0.65/0.35mole). The results indicate that R32/134a is the best of these fluids, with 3.4 % higher net powerthan R32 at the same total cost of 1200 k$.
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| 5. |
- Andreasen, J. G, et al.
(författare)
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Selection and optimization of pure and mixed working fluids for low grade heat utilization using organic Rankine cycles
- 2014
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Ingår i: Energy. - 0360-5442. ; 73
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Tidskriftsartikel (refereegranskat)abstract
- We present a generic methodology for organic Rankine cycle optimization, where the working fluid is included as an optimization parameter, in order to maximize the net power output of the cycle. The method is applied on two optimization cases with hot fluid inlet temperatures at 120°C and 90°C. Pure fluids and mixtures are compared to see how mixed working fluids affect performance and important design parameters. The results indicate that mixed working fluids can increase the net power output of the cycle, while reducing the pressure levels. The maximum net power output is obtained by fluids with a critical temperature close to half of the hot fluid inlet temperature. For some mixtures we find the maximum net power when the temperature glide of condensation matches the temperature increase of the cooling water, while for other mixtures there are large differences between these two parameters. Ethane is a fluid that obtains a large net power increase when used in mixtures. Compared to pure ethane, an optimized ethane/propane mixture attains a 12.9% net power increase when the hot fluid inlet temperature is 120_C and a 11.1% net power increase when the hot fluid inlet temperature is 90°C.
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| 6. |
- Baldasso, Enrico, et al.
(författare)
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Prediction of the annual performance of marine organic Rankine cycle power systems
- 2018
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Ingår i: ECOS 2018 - Proceedings of the 31st International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems.
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Konferensbidrag (refereegranskat)abstract
- The increasing awareness about the environmental impact of shipping and the increasingly stricter regulations introduced by the International Maritime Organization are driving the development of solutions to reduce the pollutant emissions from ships. While some previous studies focused on the implementation of a specific technology, others considered a wider perspective and investigated the feasibility of the integration of various technologies on board vessels. Among the screened technologies, organic Rankine cycle (ORC) power systems represent a viable solution to utilize the waste heat contained in the main engine exhaust gases to produce additional power for on board use. The installation of ORC power systems on board ships could result in a reduction of the CO 2 emissions by 5 – 10 %. Although a number of methods to derive the optimal design of ORC units in marine applications have been proposed, these methods are complex, computationally expensive and require specialist knowledge to be included as part of a general optimization procedure to define the optimal set of technologies to be implemented on board a vessel. This study presents a novel method to predict the performance of ORC units installed on board vessels, based upon the characteristics of the main engine exhaust gases and the ship sailing profile. The method is not computationally intensive, and is therefore suitable to be used in the context of large optimization problems, such as holistic optimization and evaluation of a ship performance given the operational profile, weather and route. The model predicted the annual energy production of two case studies with an accuracy within 4 %.
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| 7. |
- Baldasso, Enrico, et al.
(författare)
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Technical and economic feasibility of organic Rankine cycle-based waste heat recovery systems on feeder ships: Impact of nitrogen oxides emission abatement technologies
- 2019
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904. ; 183, s. 577-589
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Tidskriftsartikel (refereegranskat)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.
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| 8. |
- Baldi, Francesco, 1986, et al.
(författare)
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Analysis of the influence of the engine, propeller and auxiliary generation interaction on the energy efficiency of controllable pitch propeller ships
- 2014
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Ingår i: International Conference of Maritime Technology.
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Konferensbidrag (refereegranskat)abstract
- In a context of increasing requirements for energy efficiency, this paper aims at improving theunderstanding on the interaction between engine, propeller, and auxiliary heat and power generation in theparticular case of controllable pitch propeller (CPP) ships. The case study of a CPP propelled chemical tankeris used to analyze the application of the proposed approach. The performance of the ship’s standardarrangement using a shaft generator for the fulfillment of auxiliary power demand is compared to theoperational alternative of using auxiliary engines, and with the possibilities for retrofitting with frequencyconverters and waste heat recovery systems. The influence of control systems parameters and of sea state arealso analyzed and compared. The results show a large possibility for improvements, both via operationaloptimization (up to 8.3% increased energy efficiency) and via different types of retrofitting (with increasedefficiencies of up to 11.4% for frequency converters, and 16.5% for WHR systems). The influence of a broadoperational envelope brings even larger improvements to the efficiency of the energy system at low speeds. Theresults of the paper provide useful information about the influence of different technologies for auxiliary powergeneration on the efficiency of CPP propelled vessels.
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| 9. |
- Baldi, Francesco, 1986, et al.
(författare)
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Comparison of different procedures for the optimisation of a combined Diesel engine and organic Rankine cycle system based on ship operational profile
- 2015
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Ingår i: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 110:Part B, s. 85-93
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Tidskriftsartikel (refereegranskat)abstract
- At a time of strong challenges for shipping in relation to economic and environmental performance, the potential of waste heat recovery has been identified as among the most important technologies to lower fuel consumption. This paper presents the comparison of four different procedures for the optimisation of a combined Diesel and organic Rankine cycle system with increasing attention to the ship operational profile and to the inclusion of engine control variables in the optimisation procedure. Measured data from two years of operations of a chemical tanker are used to test the application of the different procedures. The results indicate that for the investigated case study the application of an optimisation procedure which takes the operational profile into account can increase the savings of the installation of an organic Rankine cycle from 7.3% to 11.4% of the original yearly fuel consumption. The results of this study further show that (i) simulating the part-load behavior of the ORC is important to ensure its correct operations at low engine load and (ii) allowing the engine control strategy to be part of the optimisation procedure leads to significantly larger fuel savings than the optimisation of the waste recovery system alone.
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| 10. |
- Baldi, Francesco, 1986, et al.
(författare)
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Dynamic modelling and analysis of the potential for waste heat recovery on Diesel engine driven applications with a cyclical operational profile
- 2015
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Ingår i: Proceedings of ECOS 2015 - The 28th international conference on efficiency, cost, optimisation, simulation and environmental impact of energy systems. - 9782955553909
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Konferensbidrag (refereegranskat)abstract
- As the world faces the challenge of the need for decreasing the anthropogenic carbon footprint, thecontinuous economic growth puts additional stress on the need for increased energy systems efficiency. In this context, waste heat recovery is identified as one of the most viable solutions for reducing the fuel consumption of existing systems in transportation.In this paper, we present an analysis of the potential of a waste heat recovery system applied to Diesel engine-driven systems where the operational cycle is dynamic but reducible to a limited number of operational modes. The analysis is applied to a case study for which this operational pattern is of particular relevance: a machine for sugar beet harvesting. The existence of periodical low-load periods forces to bypass the waste heat recovery turbine to avoid water condensation during the expansion. Hence, we propose the use of a thermal inertia to keep the required level of steam superheating during low-loadperiods.The results of the study showed an improvement of 27% in the recoverable exergy of the flow at the heat exchanger cold outlet when the heat exchanger wall thickness was increased from 0.5 mm to 2.5 mm. The results also show that a limited amount of the overall heat exchange inertia contributes to such improvement.
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