| 1. |
- Ahlgren, Fredrik, 1980-, et al.
(författare)
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Energy integration of organic rankine cycle, exhaust gas recirculation and scrubber
- 2018
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Ingår i: Trends and challenges in maritime energy management. - Cham, Switzerland : Springer. - 9783319745756 - 9783319745763 ; , s. 157-168
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Bokkapitel (refereegranskat)abstract
- The vast majority of ships trafficking the oceans are fuelled by residual oil with high content of sulphur, which produces sulphur oxides (SOx) when combusted. Additionally, the high pressures and temperatures in modern diesel engines also produce nitrogen oxides (NOx). These emissions are both a hazard to health and the local environment, and regulations enforced by the International Maritime Organization (IMO) are driving the maritime sector towards the use of either distillate fuels containing less sulphur, or the use of exhaust gas cleaning devices.TwocommontechniquesforremovingSOx andlimitingNOx aretheopen loop wet scrubber and exhaust gas recirculation (EGR). A scrubber and EGR installation reduces the overall efficiency of the system as it needs significant pumping power, which means that the exhaust gases are cleaner but at the expense of higher CO2 emissions. In this paper we propose a method to integrate an exhaust gas cleaning device for both NOx and SOx with an organic Rankine cycle for waste heat recovery, thereby enhancing the system efficiency. We investigate three ORC configurations, integrated with the energy flows from both an existing state-of-the-art EGR system and an additional open loop wet scrubber.
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| 2. |
- Ahlgren, Fredrik, 1980-, et al.
(författare)
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Predicting dynamic fuel oil consumption on ships with automated machine learning
- 2019
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Ingår i: Innovative Solutions for Energy Transitions. - : Elsevier. ; 158, s. 6126-6131
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Konferensbidrag (refereegranskat)abstract
- This study demonstrates a method for predicting the dynamic fuel consumption on board ships using automated machine learning algorithms, fed only with data for larger time intervals from 12 hours up to 96 hours. The machine learning algorithm trained on dynamic data from shorter time intervals of the engine features together with longer time interval data for the fuel consumption. To give the operator and ship owner real-time energy efficiency statistics, it is essential to be able to predict the dynamic fuel oil consumption. The conventional approach to getting these data is by installing additional mass flow meters, but these come with added cost and complexity. In this study, we propose a machine learning approach using auto machine learning optimisation, with already available data from the machinery logging system.
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| 3. |
- Ahlgren, Fredrik, 1980-
(författare)
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Reducing ships' fuel consumption and emissions by learning from data
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the context of reducing both greenhouse gases and hazardous emissions, the shipping sector faces a major challenge as it is currently responsible for 11% of the transport sector’s anthropogenic greenhouse gas emissions. Even as emissions reductions are needed, the demand for the transport sector rises exponentially every year. This thesis aims to investigate the potential to use ships’ existing internal energy systems more efficiently. The thesis focusses on making existing ships in real operating conditions more efficient based logged machinery data. This dissertation presents results that can make ship more energy efficient by utilising waste heat recovery and machine learning tools. A significant part of this thesis is based on data from a cruise ship in the Baltic Sea, and an extensive analysis of the ship’s internal energy system was made from over a year’s worth of data. The analysis included an exergy analysis, which also considers the usability of each energy flow. In three studies, the feasibility of using the waste heat from the engines was investigated, and the results indicate that significant measures can be undertaken with organic Rankine cycle devices. The organic Rankine cycle was simulated with data from the ship operations and optimised for off-design conditions, both regarding system design and organic fluid selection. The analysis demonstrates that there are considerable differences between the real operation of a ship and what it was initially designed for. In addition, a large two-stroke marine diesel was integrated into a simulation with an organic Rankine cycle, resulting in an energy efficiency improvement of 5%. This thesis also presents new methods of employing machine learning to predict energy consumption. Machine learning algorithms are readily available and free to use, and by using only a small subset of data points from the engines and existing fuel flow meters, the fuel consumption could be predicted with good accuracy. These results demonstrate a potential to improve operational efficiency without installing additional fuel meters. The thesis presents results concerning how data from ships can be used to further analyse and improve their efficiency, by using both add-on technologies for waste heat recovery and machine learning applications.
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| 4. |
- Ahlgren, Fredrik, 1980-, et al.
(författare)
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Waste Heat Recovery in a Cruise Vessel in the Baltic Sea by Using an Organic Rankine Cycle : A Case Study
- 2015
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Ingår i: ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. - : ASME Press. - 9780791856673 ; , s. 43392-43416
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Konferensbidrag (refereegranskat)abstract
- Maritime transportation is a significant contributor to SOx, NOx and particle matter emissions, even though it has a quite low CO2 impact. New regulations are being enforced in special areas that limit the amount of emissions from the ships. This fact, together with the high fuel prices, is driving the marine industry towards the improvement of the energy efficiency of current ship engines and the reduction of their energy demand. Although more sophisticated and complex engine designs can improve significantly the efficiency of the energy systems in ships, waste heat recovery arises as the most influent technique for the reduction of the energy consumption. In this sense, it is estimated that around 50% of the total energy from the fuel consumed in a ship is wasted and rejected in fluid and exhaust gas streams. The primary heat sources for waste heat recovery are the engine exhaust and the engine coolant. In this work, we present a study on the integration of an organic Rankine cycle (ORC) in an existing ship, for the recovery of the main and auxiliary engines exhaust heat. Experimental data from the operating conditions of the engines on the M/S Birka Stockholm cruise ship were logged during a port-to-port cruise from Stockholm to Mariehamn over a period of time close to one month. The ship has four main engines Wärtsilä 5850 kW for propulsion, and four auxiliary engines 2760 kW used for electrical consumers. A number of six load conditions were identified depending on the vessel speed. The speed range from 12–14 knots was considered as the design condition, as it was present during more than 34% of the time. In this study, the average values of the engines exhaust temperatures and mass flow rates, for each load case, were used as inputs for a model of an ORC. The main parameters of the ORC, including working fluid and turbine configuration, were optimized based on the criteria of maximum net power output and compactness of the installation components. Results from the study showed that an ORC with internal regeneration using benzene would yield the greatest average net power output over the operating time. For this situation, the power production of the ORC would represent about 22% of the total electricity consumption on board. These data confirmed the ORC as a feasible and promising technology for the reduction of fuel consumption and CO2 emissions of existing ships.
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| 5. |
- Mondejar, Maria E., et al.
(författare)
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Analysis of isentropic mixtures for their use as working fluids in organic Rankine cycles
- 2017
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Ingår i: Environmental Progress & Sustainable Energy. - : Wiley. - 1944-7442. ; 36:3, s. 921-935
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Tidskriftsartikel (refereegranskat)abstract
- The selection of appropriate working media for organic Rankine cycles (ORC) is essential for the optimization of their performance. Dry fluids are widely used in existing ORC because, unlike wet fluids, they do not need to be superheated to avoid wet expansion that may cause damage to the expander. However, regeneration is sometimes needed for fluids with a highly dry behavior in order to improve the overall ORC efficiency, at the expense of increasing the total capital costs. On the contrary, isentropic fluids, with a nearly isentropic saturated vapor curve, overcome these two drawbacks. Because the number of single component fluids with isentropic behavior is scarce, we propose the use of isentropic binary mixtures, composed by a wet and a dry component. In this work, we selected several isentropic binary mixtures composed of hydrofluorocarbons, hydrochlorofluorocarbons and hydrocarbons from the Refprop database. The performance of these mixtures was evaluated in a simple saturated ORC model for source temperatures between (350 and 450) K and a fixed sink temperature of 290 K. The results were compared to those yielded by pure isentropic and dry fluids under the same source and sink conditions.
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| 6. |
- Mondejar, Maria E., et al.
(författare)
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Power generation from low heat sources
- 2014
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Ingår i: Advances in Energy Research and Development. - 9780989559010 ; , s. 49-82
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Bokkapitel (refereegranskat)abstract
- In this chapter a thorough review of the latest research findings on power generation from non-conventional low heat sources is presented. Main discoveries and results of research works ranging from source exploitation technologies to final power production are reported and discussed to offer an overview of their potential. Firstly the concept of low-grade source is presented and the main energy sources in this group (i.e. geothermal energy, solar thermal systems, industrial waste heat and ocean thermal energy) are introduced. Each of them is briefly described and the latest developments and improvements on the technologies for their exploitation are enumerated. Afterwards the state-of-the-art available power cycles for the conversion of low heat into electricity are reported. Only thermal power conversion technologies are presented due to their higher presence in commercial applications and their potential for small scale power generation. Among these technologies, last findings and results on organic Rankine cycles (ORC) and power cycles based on working fluid mixtures (e.g. Kalina cycle) are described. A special emphasis is placed on organic Rankine cycles (ORC) since over the last few years this technology has experienced a significant global growth, boosted by their viable performance and the inherited knowledge from the refrigeration industry. In addition, the suitability of less known technologies such as Stirling cycles and their current development status and perspectives are also commented. After this review it follows an examination of the implementation of these technologies in present power production systems. Discussion will be provided on which are the current barriers that the mentioned technologies are facing for their introduction or during their operation. On the other hand, practical restrictions concerning the availability of suitable technology, environmental requirements or economic viability are stated. Limitations regarding thermodynamic and technological aspects, as well as operational concerns will be considered of special interest. In the final section we deal with the future scenario for the integration of small-scale power generation. Potential solutions for overcoming technology development barriers are presented and directions of current research works on this topic are pointed out.
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| 7. |
- Mondejar, Maria E., et al.
(författare)
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Quasi-steady state simulation of an organic Rankine cycle for waste heat recovery in a passenger vessel
- 2017
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Ingår i: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 185:Special Issue Part 2, s. 1324-1335
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Tidskriftsartikel (refereegranskat)abstract
- In this work we present the quasi-steady state simulation of a regenerative organic Rankine cycle (ORC)integrated in a passenger vessel, over a standard round trip. The study case is the M/S Birka Stockholmcruise ship, which covers a daily route between Stockholm (Sweden) and Mariehamn (Finland).Experimental data of the exhaust gas temperatures, engine loads, and electricity demand on board werelogged over a period of four weeks. These data where used as inputs for a simulation model of an ORC forwaste heat recovery of the exhaust gases. A quasi-steady state simulation was carried out on an offdesignmodel, based on optimized design conditions, to estimate the average net power production ofthe ship over a round trip. The maximum net power production of the ORC during the round trip wasestimated to supply approximately 22% of the total power demand on board. The results showed apotential for ORC as a solution for the maritime transport sector to accomplish the new and morerestrictive regulations on emissions, and to reduce the total fuel consumption.
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