| 1. |
- Baldi, Francesco, 1986, et al.
(författare)
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Energy and exergy analysis of ship energy systems - The case study of a chemical tanker
- 2015
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Ingår i: International Journal of Applied Thermodynamics. - : International Centre for Applied Thermodynamics (ICAT). - 1301-9724 .- 2146-1511. ; 18:2, s. 82-93
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Tidskriftsartikel (refereegranskat)abstract
- Shipping contributes today to 2.1% of global anthropogenic greenhouse gas emissions and its share is expected to grow together with global trade in the coming years. At the same time, bunker prices are increasing and companies start to feel the pressure of growing fuel bills in their balance sheet. In order to address both challenges, it is important to improve the understanding of the energy consumption trends on ships through a detailed analysis of their energy systems. In this paper, energy and exergy analysis are applied to the energy system of a chemical tanker, for which both measurements and technic knowledge of ship systems were available. The application of energy analysis to the case-study vessel allowed for the comparison of different energy flows and therefore identifying system components and interactions critical for ship energy consumption. Exergy analysis allowed instead identifying main inefficiencies and evaluating waste flows. Results showed that propulsion is the main contributor to ship energy consumption (70%), but that also auxiliary heat (16.5%) and power (13.5%) needs are relevant sources of energy consumption. The potential for recovering waste heat is relevant, especially from the exhaust gases, as their exergetic value represents 18% of the engine power output.
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| 2. |
- Johnson, Hannes, 1982, et al.
(författare)
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Increased energy efficiency in short sea shipping through decreased time in port
- 2015
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Ingår i: Transportation Research Part A: Policy and Practice. - : Elsevier BV. - 0965-8564. ; 71, s. 167-178
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Tidskriftsartikel (refereegranskat)abstract
- According to a range of assessments, there exists a large cost-effective potential to increase energy efficiency in shipping through reduced speed at sea enabled by shorter time in port. This means that the energy needed can be reduced whilst maintaining the same transport service. However, the fact that a large cost-effective potential has been identified that is not being harnessed by decision-makers in practice suggests that there is more to this potential to understand. In this paper, the possibilities for increasing energy efficiency by reducing waiting time in port are explored and problematised through a case study of a short sea bulk shipping company transporting dry bulk goods mainly in the North and Baltic seas. Operational data from two ships in the company’s fleet for one year showed that the ships spent more than 40% of their time in ports and that half of the time in port was not productive. The two most important reasons for the large share of unproductive time were that ports were closed on nights and weekends and that ships arrived too early before the stevedores were ready to load or unload the cargo. Reducing all of the unproductive time may be difficult, but the results also show that even a conservative estimate of one to four hours of reduced time per port call would lead to a reduction in energy use of 2-8%. From in-depth interviews with employees of the shipping company, ports and ship agencies, a complex picture is painted when attempting to understand how this potential arises. Aspects such as a lack of effective ship-shore-port communication, little time for ship operators, an absence of means for accurately predicting energy use of voyages as a function of speed, perceived risk of arriving too late, and relationships with third-party technical management may all play a role.
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