Simulation Techniques for Design and Control of a Waste Heat Recovery System in Marine Natural Gas Propulsion Applications

Waste Heat Recovery (WHR) marine systems represent a valid solution for the ship energy eciency improvement, especially in Liquefied Natural Gas (LNG) propulsion applications. Compared to traditional diesel fuel oil, a better thermal power can be recovered from the exhaust gas produced by a LNG-fueled engine. Therefore, steam surplus production may be used to feed a turbogenerator in order to increase the ship electric energy availability without additional fuel consumption. However, a correct design procedure of the WHR steam plant is fundamental for proper feasibility analysis, and from this point of view, numerical simulation techniques can be a very powerful tool. In this work, the WHR steam plant modeling is presented paying attention to the simulation approach developed for the steam turbine and its governor dynamics. Starting from a nonlinear system representing the whole dynamic behavior, the turbogenerator model is linearized to carry out a proper synthesis analysis of the controller, in order to comply with specific performance requirements of the power grid. For the considered case study, simulation results confirm the validity of the developed approach, aimed to test the correct design of the whole system in proper working dynamic conditions

Techno economic and environmental assessment of wind assisted marine propulsion systems

In recent years, the increase in marine fuel prices coupled with stricter regulations on pollutant emissions set by the International Maritime Organization have promoted the research in new propulsion technologies and the utilisation of cleaner fuels. This paper describes a novel methodology to enable quantifying and evaluating the environmental and economic benefits that new technologies and fuels could allow in the marine sector. The proposed techno economic and environmental analysis approach enables consistent assessment of different traditional propulsion systems (diesel engine and gas turbine) when operated in conjunction with a novel environmental friendly technology, such as a vertical axis wind turbine. The techno-economic and environmental assessment is focused on the potential reduction in fuel consumption and pollutant emissions that may be accrued while operating on typical Sea Lines Of Communication (Mediterranean, North Sea, Atlantic). The study demonstrates the benefits of the installation of two vertical axis wind turbines on the deck of a ship in conjunction with conventional power plants. The analysis indicates that the performance of the wind turbines and the corresponding benefits strongly depend on the routes and environment in which they operate (therefore favourable wind conditions) allowing fuel savings from 14% (in the gas turbine case) to 16% (in the diesel engine case). The study also indicates that possible benefits may diminish for weak wind conditions. The results reported in this paper establish the economic benefits of installing vertical axis wind turbines in conjunction with conventional technology (Diesel and Gas Turbine Power plants) when installed on a ship travelling through the Atlantic Ocean. The primary purpose of this study is to introduce a methodology to demonstrate the application, performance and economic benefits of the technology at a preliminary design phase and further form a foundation for more elaborate analysis on the subject in the future

Energy, economic and environmental analysis of a BOG re-liquefaction process for an LNG carrier

Due to tighter environmental regulations, newly built liquefied natural gas (LNG) carriers are equipped with a re-liquefaction system to minimize combustion of surplus boil-off-gas (BOG). Thus, this paper comparatively analyzes the re-liquefaction system for a low-pressure gas injection engine according to the refrigerant (no external refrigerant or single mixed refrigerant) with three key performance indicators: energy, economic, and environmental aspects. For an energy efficiency analysis, we proposed several process alternatives and optimized them to minimize the specific power consumption required to liquefy BOG. In economic analysis, minimizing total annualized cost is the objective. For an environmental analysis, CO2 emissions at each optimal point is calculated and comparatively analyzed. The results show that the process without external refrigerant has 10% better performance in terms of economy, while the single mixed refrigerant process is suitable in terms of energy efficiency (6%) and environmental (15%) impact.Energy, economic and environmental analysis of a BOG re-liquefaction process for an LNG carrierpublishedVersio

Mathematical Modelling of LNG Dispersion Under Various Conditions

The global demand of liquefied natural gas (LNG) has risen rapidly in recent years. A new modelling method, direct CFD simulation method, was developed, due to the risks associated in handling, storage and transport of LNG. This method was shown to accurately model a LNG spill, pool formation and dispersion; and has been used to study the effect of (a) Impoundments, (b) Sea and air temperature and; (c) Sea and air stability

Study of solvent-based carbon capture for cargo ships through process modelling and simulation

Controlling anthropogenic CO2 emission is crucial to mitigate global warming. Marine CO2 emissions accounts for around 3% of the total CO2 emission worldwide and grows rapidly with increasing demand for passenger and cargo transport. The International Maritime Organization (IMO) has adopted mandatory measures to reduce greenhouse gases (GHGs) emissions from international shipping. This study aims to explore how to apply solvent-based post-combustion carbon capture (PCC) process to capture CO2 from the energy system in a typical cargo ship and to evaluate the cost degrees of different integration options through simulation-based techno-economic assessments. The selected reference cargo ship has a propulsion system consisting of two four-stroke reciprocating engines at a total power of 17 MW. The study first addressed the challenge on model development of the marine diesel engines and then developed the model of the ship energy system. The limitations of implementing onboard carbon capture were discussed. Two integration options between the ship energy system and the carbon capture process were simulated to analyse the thermal performance of the integrated system and to estimate equipment size of the carbon capture process. It was found that the carbon capture level could only reach 73% when the existing ship energy system is integrated with the PCC process due to limited heat and electricity supply for CCS. The cost of CO2 captured is around 77.50 €/ton CO2. With installation of an additional gas turbine to provide extra energy utilities to the capture plant, the carbon capture level could reach 90% whilst the cost of CO2 captured is around 163.07 €/ton CO2, mainly because of 21.41% more fuel consumption for the additional diesel gas turbine. This is the first systematical study in applying solvent-based carbon capture for ships, which will inspire other researchers in this area

Maritime Computing Transportation, Environment, and Development: Trends of Data Visualization and Computational Methodologies

This research aims to characterize the field of maritime computing (MC) transportation, environment, and development. It is the first report to discover how MC domain configurations support management technologies. An aspect of this research is the creation of drivers of ocean-based businesses. Systematic search and meta-analysis are employed to classify and define the MC domain. MC developments were first identified in the 1990s, representing maritime development for designing sailboats, submarines, and ship hydrodynamics. The maritime environment is simulated to predict emission reductions, coastal waste particles, renewable energy, and engineer robots to observe the ocean ecosystem. Maritime transportation focuses on optimizing ship speed, maneuvering ships, and using liquefied natural gas and submarine pipelines. Data trends with machine learning can be obtained by collecting a big data of similar computational results for implementing artificial intelligence strategies. Research findings show that modeling is an essential skill set in the 21st century

ENVIRONMENTAL AND COST-EFFECTIVENESS COMPARISON OF DUAL FUEL PROPULSION OPTIONS FOR EMISSIONS REDUCTION ONBOARD LNG CARRIERS

The selection of the suitable propulsion system for LNG carrier highly affects the ship capital and life cycle costs. The current paper compares between the available propulsion systems for LNG carriers from environmental and economic points of view operated with heavy fuel oil (HFO) and marine gas oil (MGO). In addition, the cost-effectiveness for emission reduction due to using dual fuel propulsion options using natural gas fuel (NG) is calculated. As a case study, large conventional LNG carrier class has been investigated. The results show that steam turbine (ST), Ultra-ST, dual fuel diesel engine (DFDE), and combined gas and steam (COGAS) propulsion options can comply with NOx and SOx emissions regulations set by IMO using dual fuel mode with NG percentages of 87.5%, 82%, 98.5% and 94%, respectively. DFDE operated with pilot HFO and NG is the most economic propulsion option. It reduces the dual fuel costs by 1.37 MUS$/trip compared with HFO cost. The annual cost-effectiveness for the most economic and emission compliance propulsion option is 6.07$/kg, 6.39 $/kg, and 0.55$/kg for reducing NOx, SOx, and CO2 emissions, respectively

Techno economic and environmental assessment of Flettner rotors for marine propulsion

Wind energy is a mature renewable energy source that offers significant potential for near-term (2020) and long-term (2050) greenhouse gas (GHG) emissions reductions. Similar to all sectors of the transportation industry, the marine industry is also focused towards reduction of environmental emissions. A direct consequence of this being is a renewed interest in utilising wind as supplementary energy source for propulsion on cargo/merchant ships. This research utilises a techno economic and environmental analysis approach to assess the possibility and benefits of harnessing wind energy, with an aim to establish the potential role of wind energy in reducing GHG emissions during conventional operation of marine vessels. The employed approach enables consistent assessment of different competing traditional propulsion systems when operated in conjunction with a novel environmental friendly technology, in this instance being the Flettner rotor technology. The assessment specifically focuses on quantifying the potential and relative reduction in fuel consumption and pollutant emissions that may be accrued while operating on typical Sea Lines of Communication. The results obtained indicate that the implementation of Flettner towers on commercial vessels could result in potential savings of up to 20% in terms of fuel consumption, and similar reductions in environmental emissions

Advancing sustainability in the maritime sector: energy design and optimization of large ships through information modelling and dynamic simulation

This paper deals with a new energy design approach for ships to reduce the fuel consumption and the related environmental impact. The proposed method is based on the application of the Building Information Modeling (BIM) to Building Energy Modeling (BEM) technique. Specifically, by a BIM model of the ship a 3D physics-based model (BEM) can be suitably created. Then, by BEM the ship energy performance is simulated under real and dynamic operating conditions. By the presented method the whole design-to-delivery process of the ship can be simplified and speeded up with respect to traditional approaches, without losing reliability. As an example, HVAC systems design is easier through BIM since a high number of thermal zones can be effectively handled. Due to BEM, also the optimal design for exploiting waste heat recoveries of on-board combustion engines is easier and faster. To show the capability of the proposed approach a suitable case study was developed. Basically, it concerns the energy performance analysis of the Allure of the Seas, a 6000-passenger cruise ship operating in the Caribbean Sea. Two different scenarios for recovering the waste heat of the ship diesel generators are investigated. Simulation results highlight that significant primary energy saving can be obtained by optimizing the strategy to recover the available thermal energies (up to 600 MWh per trip), with a remarkable amount of avoided pollutant emissions (58, 0.06, 4.0, 0.2, 2.0 kg/km of CO2, PM2.5, NOx, HC, SOx, respectively).The presented new approach can be easily adopted to design and optimize the energy system of any new or existing ships, with the twofold aim to achieve economic savings and to fulfil environmental sustainability standards

Optimal design and operation of maritime energy systems based on renewable methanol and closed carbon cycles

The phasing out of fossil fuels in the shipping sector is of key importance for reducing greenhouse gas emissions. Synthetic fuels based on renewable energy are a promising option for a sustainable maritime sector, with renewable methanol being one of the most widely considered energy carriers. However, the availability of renewable methanol is still limited and the costs associated with it are significantly higher than for conventional fuels, also because fuel synthesis must rely on carbon dioxide as a resource. Through the use of onboard carbon capture, the release of carbon dioxide during combustion can be avoided, and this closed cycle reduces the need for carbon sources. This paper investigates such a scenario by analyzing overall ship energy systems that use internal combustion engines with connected pre-combustion and post-combustion carbon capture technologies. The effect of these technologies on the techno-economic performance of a fully renewable energy system is investigated by setting up a mixed-integer optimization framework for the optimal design and operation of ship propulsion systems. The propulsion demand for the chosen case study consists of a typical operational profile of a ferry operating in the Baltic Sea. Comparison of the capture cases to a system solely based on renewable methanol reveals significant cost advantages of the closed carbon cycle systems. The baseline scenario has nearly 20% lower annual costs, with total capture rates of 90% in the post-combustion case and around 40% in the pre-combustion case. An extensive sensitivity analysis shows that these cost advantages are robust against various technological and economic boundary conditions. In the pre-combustion case, process heat demand reduction in combination with increased engine heat supply might enable higher capture rates beyond 90%. The results indicate that combining renewable fuels with onboard carbon capture creates opportunities for cost-effective, sustainable shipping