| 1971. |
- Gustavsson, Mikael, 1983, et al.
(författare)
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Estimation of Maximum Loss - A comparison study
- 2010
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Ingår i: SHO2010: INTERNATIONAL SYMPOSIUM ON OCCUPATIONAL SAFETY AND HYGIENE. - 9789729950469 ; , s. 280-284
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Petroleum refineries are at risk due to the flammability of both the raw material and the products. In addition to the threat to the working force there is also an apparent economical risk associated with the processing of flammable compounds. This economical risk is not only due to the direct impact of a fire or explosion but also includes the cost of business interruption in case of a shutdown due to an accident. As with any situation that involves economical risks refineries may share their risk with insurers. The premium is then based on the size of the financial risk. Thus a decision has to be made by the operator how to share the risk of economical losses with insurance companies at a fair price. However, the decision process is not easy and it generally includes modelling of various scenarios to determine to which extent the process area can be damaged if, for example, a pipe rupture occurs. On the extreme end of modelling the so called Estimated Maximum Loss (EML) scenarios are found. These scenarios try to predict the maximum loss a particular installation can sustain due to an accident. Unfortunately a standard model for estimation of maximum loss does not exist. It means that brokers reach different results on the same scenario due to applying different models and different assumptions. Thus an operator may face uncertainty during the decision process. Hence improvements should be made not only to the models used but also to the concept of EML itself. Therefore, a study has been conducted on a case "Preem Refinery" where several scenarios previously had been modelled by two different brokers using two different softwares, ExTool and SLAM. The aim of this paper is to review the concept of EML and to analyse the used models to see which parameters that influenced the results. The results of the study show that: Overpressure damage threshold values, cloud weights, and releasable inventory are the main sources of deviation in the modelled scenarios; Clear cut-off values for the probabilities of an accident should be used to avoid the "not plausible" argument sometimes heard. As for improving the models themselves, no clear reason for working with threshold values when it comes to overpressure damage can be found. A continuous curve seems more fitting in the age of computers. The possibility to shift such a curve to account for the difference in overpressure sustainability between different types of process equipment could also be explored; and, there are many aspects to investigate further in order to make potential loss predictions more reliable, and this should be well worthwhile since a lot of money is at stake when plant owners and insurers decide on insurance limits and premiums.
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| 1972. |
- Gustavsson, Patrik, et al.
(författare)
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A New Algorithm Using the Non-dominated Tree to improve Non-dominated Sorting
- 2018
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Ingår i: Evolutionary Computation. - : MIT Press. - 1063-6560 .- 1530-9304. ; 26:1, s. 89-116
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Tidskriftsartikel (refereegranskat)abstract
- Non-dominated sorting is a technique often used in evolutionary algorithms to determine the quality of solutions in a population. The most common algorithm is the Fast Non-dominated Sort (FNS). This algorithm, however, has the drawback that its performance deteriorates when the population size grows. The same drawback applies also to other non-dominating sorting algorithms such as the Efficient Non-dominated Sort with Binary Strategy (ENS-BS). An algorithm suggested to overcome this drawback is the Divide-and-Conquer Non-dominated Sort (DCNS) which works well on a limited number of objectives but deteriorates when the number of objectives grows. This paper presents a new, more efficient, algorithm called the Efficient Non-dominated Sort with Non-Dominated Tree (ENS-NDT). ENS-NDT is an extension of the ENS-BS algorithm and uses a novel Non-Dominated Tree (NDTree) to speed up the non-dominated sorting. ENS-NDT is able to handle large population sizes and a large number of objectives more efficiently than existing algorithms for non-dominated sorting. In the paper, it is shown that with ENS-NDT the runtime of multi-objective optimization algorithms such as the Non-Dominated Sorting Genetic Algorithm II (NSGA-II) can be substantially reduced.
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| 1973. |
- Guthed, Arvid, 1976, et al.
(författare)
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EXPANDED VIEW ON THE CONCEPT OF INTERMODALITY
- 2005
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Ingår i: 8th NECTAR CONFERENCE, Las Palmas G.C. June 2-4, 2005.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Intermodal research has to a large extent focused on the technical issues of intermodality and transport optimisation. While the focal point of the theoretical intermodal concept is on the transfer of load units between transport modes, practitioners acknowledge the transfer of information and responsibilities between involved actors as key issues.This research investigates the contradiction of viewpoints: on one hand, the goods flow perspective where flows are seen as continuous chains through nodes and links in a transport network, and on the other hand, the firm perspective with focus on the transport operators internal productivity and profitability. There is thus a conceptual limitation in the simplistic linear view of the theoretical intermodal concept, referring to intermodal transport chains as seamless, with regard to cooperation among actors in the network structure. As a consequence, a conflict of interests may occur between the two perspectives. The conclusions have been reached through two extensive case studies where findings have been categorised into three key areas that are essential in order to attain high performance in an intermodal assignment: interfaces, chain integration and resource utilisation. The key areas include both technical and organisational aspects, to reflect the characteristics of intermodality. Execution of an intermodal transport assignment relies on both the operators business strategies and the characteristics of their respective transport modes. The former relates to the efficiency of information transfer and the willingness to cooperate among the actors, whereas the latter refers to connectivity in terms of appropriate facilities and bridging of gaps between the modes concerning frequency, capacity and time. This paper focuses on the first issue and the objective is to broaden the view on intermodal transportation by bringing organisational and managerial aspects into consideration besides the pure technical description. There is thus a need of expanding the most widespread theoretical definition of intermodality in order to reflect the distinguishing characteristics of intermodal transportation. Thereby the theoretical description of the concept better reflects practice.
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| 1974. |
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| 1975. |
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| 1976. |
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| 1977. |
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| 1978. |
- Gärling, Tommy, 1941, et al.
(författare)
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Satisfaction with travel and the relationship to well-being
- 2021
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Ingår i: Vickerman, R. (Ed.), International encyclopedia of transportation (Vol. 7,). - : Elsevier. - 9780323916363 ; , s. 177-181
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Bokkapitel (refereegranskat)abstract
- What makes everyday travel satisfying or dissatisfying, and how does satisfaction or dissatisfaction with everyday travel influence well-being? To address these questions self-report ratings of satisfaction with travel have been developed and used primarily in studies of commutes to and from work. Main findings include: (1) Satisfaction is lower with travel for work than leisure purposes; (2) Satisfaction with walking and cycling are higher than satisfaction with car use, and satisfaction with car use is higher than satisfaction with public transport use; (3) Long commutes are stressful or boring; (4) Negative carry-over effects are observed on daily emotional well-being and performance of activities at the destination. In order to further increase knowledge of how satisfaction is related to features of travel, more refined online measurements of satisfaction are needed. This is essential for increasing travel-related satisfaction with the aim of reducing the negative consequences for emotional well-being and life satisfaction.
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| 1979. |
- Göransson, Lisa, 1982, et al.
(författare)
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Dispatch modeling of a regional power generation system - Integrating wind power
- 2009
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Ingår i: Renewable Energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 34:4, s. 1040-1049
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Tidskriftsartikel (refereegranskat)abstract
- A modeling tool has been developed which can be used to analyze interaction between intermittent wind power generation and thermal power plant generation in a regional electricity grid system. The model uses a mixed integer programming (MIP) approach to determine the power plant dispatch strategy which yields the lowest systems costs. In the model, each large thermal plant is described separately, including properties such as start-up time, start-up cost and minimum load level. The model is evaluated using western Denmark as a case study.For western Denmark, it is found that the inclusion of start-up performance (i.e. start-up time and related costs) and minimum load level of the power generating units have a significant impact on the results. It is shown that the inclusion of these aspects influences the analysis of the effect of wind power variations on the production patterns of thermal units in the system. The model demonstrates how the introduction of wind power production and associated variations change the dispatch order of the large thermal power plants in the western Denmark system so that the unit with the lowest running costs no longer has the highest capacity factor. It is shown that this effect only is detected if start-up performance and minimum load level limitations are included in the optimization. it can also be concluded that start-up performance and minimum load level must be taken into account if the total system costs and emissions are not to be underestimated. The simulations show that if these aspects are disregarded, both total costs and total emissions of the power system are underestimated, with 5% in the case of western Denmark. Models such as the one developed in this work can be efficient tools to understand the effects of large-scale wind power integration in a power generation system with base load plants.
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| 1980. |
- Göransson, Lisa, 1982
(författare)
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Wind power in thermal power systems
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- AbstractWind power is a key technology in the effort to transform the power system in order to reduce its climate impact. However, the ability of wind power to reduce CO2-emissions depends on the properties of the power system. As large-scale wind power is integrated in a power system (typically 20% wind power grid penetration and beyond), the intermittent nature of wind power will result in an increase in variations in load on the other units in the system (e.g. thermal power plants). There are three main alternatives for the power system to respond to this increase in variations; by an increase in power plant cycling (i.e. starting/stopping), by an increase in part load operation hours or by wind power curtailment. In a system dominated by thermal base load units, the integration of large-scale wind power might thus result in an increase in costs and emissions related to thermal operation and/or an increase in wind power curtailment.This work investigates consequences of large-scale wind power integration in a thermal power system. Operation of units in a regional thermal power system have been investigated and quantified by means of modelling. Furthermore, the possibility to reduce the influence from wind power variations by means of introducing a variation moderator or demand side management has been evaluated. A variation moderator is a unit with the ability to reallocate power in time. Pumped hydro power stations, compressed air energy storages, batteries and transmission lines providing power exchange are examples of variation moderators which are all investigated in this work. Demand side management will allow for some flexibility in the allocation of parts of the load and in this work evaluates the ability of plug-in hybrid electric vehicles (PHEV:s) to provide such flexibility. The simulations are carried out with a simplified version of the western Denmark power system as a starting point. This, since this system already has a high share of wind power and wind power data is available.For the system studied, simulations show that for 24% wind power grid penetration, variations in wind power generation results in start-up emissions corresponding to 5% of the total CO2-emissions of the power generation system. It is also shown that the inclusion of start-up and minimum load level aspects has an impact on the dispatch of units in the system. By integration of a moderator in the wind-thermal system, emissions are reduced with 7.2% mainly due to a decrease in power plant cycling. At wind power grid penetration levels of around 20%, a daily balanced moderator is sufficient, whereas more extensive storage capacity is required at higher wind power penetration levels such as for the 40% penetration level investigated in this work.The ability of PHEV:s to manage wind power variations depends strongly on the choice of PHEV integration strategy. With a strategy where the power system is free to allocate the load in time, emissions from the power system (excluding vehicles) are up to 6% lower than a corresponding system without PHEV:s. A passive approach to PHEV integration results in increased emissions from the system. For the system studied, the PHEV share of the electricity consumption should be around 12% to obtain maximum reduction in emission. This, since this share of PHEV capacity approximately corresponds to the difference in average load between night and day (evens out variations in load profile).
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