| 1. |
- 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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| 2. |
- 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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| 3. |
- Baldi, Francesco, 1986, et al.
(författare)
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Energy and exergy analysis of a cruise ship
- 2015
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Ingår i: Proceedings of ECOS 2015 - the 28th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems. - Pau : Pau University. - 9782955553909
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Konferensbidrag (refereegranskat)abstract
- The shipping sector is today facing numerous challenges. Fuel prices are expected to increase in the medium-long term, and a sharp turn in environmental regulations will require several companies to switch to more expensive distillate fuels. In this context, passenger ships represent a small but increasing share of the industry. The complexity of the energy system of a ship where the energy required by propulsion is no longer the trivial main contributor to the whole energy use thus makes this kind of ship of particular interest for the analysis of how energy is converted from its original form to its final use on board.To illustrate this, we performed an analysis of the energy and exergy flow rates of a cruise ship sailing in the Baltic Sea based on a combination of available measurements from ship operations and of mechanistic knowledge of the system. The energy analysis allows identifying propulsion as the main energy user (41% of the total) followed by heat (34%) and electric power (25%) generation; the exergy analysis allowed instead identifying the main inefficiencies of the system: exergy is primarily destroyed in all processes involving combustion (88% of the exergy destruction is generated in the Diesel engines and in the oil-fired boilers) and in the sea water cooler (5.4%); the main exergy losses happen instead in the exhaust gas, mostly from the main engines (67% of total losses) and particularly from those not equipped with heat recovery devices.The improved understanding which derives from the results of the energy and exergy analysis can be used as a guidance to identify where improvements of the systems should be directed.
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| 4. |
- Castro Flores, José Fiacro, et al.
(författare)
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Energetic and exergetic analysis of a low- Temperature based district heating substation for low energy buildings
- 2015
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Ingår i: ECOS 2015 - 28th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems. - : International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems. - 9782955553909
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Konferensbidrag (refereegranskat)abstract
- District Heating (DH) technology contributes to the low GHG emissions energy system, facilitates a renewable energy usage, and increases the overall system efficiency, while providing the necessary heating services to the built environment. However, the existing DH technology may not be technically and economically effective to service buildings with low-energy demands. Here, low- Temperature based district heating (LTDH) provides a better match between supply and demand in terms of energy quality. This paper deals with the energy and exergy analyses of a LTDH substation supplying a secondary LTDH network as a subnet of the existing DH system. The substation is supplied with a mix of supply and return flows from the main DH network. An energy and exergy analysis was employed based on modelling and simulation to compare the performance of two proposed substation configurations to that of a conventional DH substation operating at low- Temperature. The study was performed for a year round outdoor temperatures scenario under steady-state conditions. The exergy destruction at the system components was identified and compared. The results of this analysis show that by using the low- Temperature flow from the DH return pipe, the final exergy efficiency of the overall system is increased. On the other hand, assuming an adiabatic system the energy performance stays the same. As compared with the conventional DH network, the integration of the proposed LTDH substation reduced the share of energy demand covered by the main DH supply by 20-25% and improved the overall exergy efficiency from 79% to 85-87% depending on the substation configuration. Based on the results, the solution presented is seen as an effective approach to reduce the system's losses, and to increase the quality match between the low-energy heating demands and the supply.
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| 5. |
- Eriksson, Lina J, 1985, et al.
(författare)
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Greenhouse gas emissions consequences of utilization of excess heat from an oil refinery
- 2015
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Ingår i: Proceedings of ECOS 2015 – The 28th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, June 29-July 3, 2015, Pau, France. - 9782955553909
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Konferensbidrag (refereegranskat)abstract
- Increasing utilization of industrial excess heat is an important step towards reaching EU targets for increased energy efficiency and decreased greenhouse gas (GHG) emissions. There are many options for harnessing excess heat. However, the corresponding impact on GHG emissions differ significantly depending on the assumed marginal production technology replaced in the surrounding energy system. In order to identify robust solutions and avoid sub-optimization, different possibilities for utilizing excess heat need to be compared and evaluated using a systems perspective with different future energy markets scenarios. The purpose of this paper is to investigate and compare different utilization options in terms of GHG emission reduction potential. The paper presents an illustrative case of a large modern refinery on the West Coast of Sweden with a crude oil capacity of 11.4 Mt crude/y. The potential for producing electricity with an Organic Rankine Cycle (ORC), delivering excess heat to a district heating (DH) network and using it for post combustion carbon capture (CCS) are quantified using pinch analysis tools. Consequences for GHG emissions are evaluated based on different assumptions for future grid marginal electricity production. The results indicate that the GHG emission reduction potential is larger for CCS and DH than for electricity production via ORC. CCS achieves the highest GHG reduction potential per MW of recovered excess heat whereas DH shows the largest total potential for GHG reduction. It is possible to combine CCS and DH, and it is recommended to utilize first the maximum amount of excess heat in CCS and the remaining in DH. This combination results in GHG emission reduction corresponding to up to 40% of the onsite CO2 emissions.
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| 6. |
- Grip, Carl-Erik, et al.
(författare)
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Forestry meets Steel. A system study of the possibility to produce DRI (directly Reduced Iron) using gasified biomass.
- 2015
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Ingår i: ECOS 2015 - 28th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems. - : International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems. - 9782955553909
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Konferensbidrag (refereegranskat)abstract
- The main production of primy Iron from ore is now made by reduction using fossil reductants, either by producing hot metal in the blast furnace process or as directly reduced iron with natural gas as most common reductant. The climate gas impact would be improved if at least pt of the reductants could be produced from Biomass. One possibility could be to use gasified Biomass to produce DRI (Directly Reduced Iron). This is studied in a cooperative project where LTU, MEFOS, ETC and five industries in the eas forestry & pulp, mining, iron and gas e involved. The investigation is made in four pts where the first one is on the supply of biomass. A lge amount of Biomass has to be delivered into a single site to exchange a lge amount of fossil reductant. Also, forestry by-products should be used as most of the round wood is reserved for other uses. Hvesting, logistics and economics e considered. The second pt is on the gasification of the biomass, where the aim is to use to produce hot gas that can be used directly. Pilot experiments e cried out using oxygen in an entrained flow gasifier. The third pt is on the metallurgical processes, where reduction tests e cried out with gas that can be produced in the gasifier. The limitations of the gas content e studied as well as the effect on DRI. Also the suitability of the DRI product is evaluated. The fourth pt of the project uses process integration to model the whole process chain. The results from the other project pts e used to build the system model. It is then used for technical economic optimization the whole system hvesting- Transport-gasifier-direct reduction-use of DRI. The first use of the system model has been to find the best supply road (hvesting, pretreatment and transport) for a chosen production case The simulations indicated that the supply of residuals is possible but will need material from a lge pt of the north Sweden wood ea, and that a relatively lge amount of gas recirculation is needed. The continuing work is focused on further development of the optimization tool and the use of it for more extensive studies of the trade-off between pameters of metallurgy, gasification and supply. The result can be important for evaluation of future industrial applications. It could also help in understanding the effect of governmental control instruments. The paper will mainly focus on the process integration study.
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| 7. |
- Lovella, Y. G., et al.
(författare)
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Multi-objective optimization of the thermal and hydraulic design of a heat exchanger of the type shell and tubes
- 2015
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Ingår i: ECOS 2015 - 28th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems. - : International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems. - 9782955553909
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Konferensbidrag (refereegranskat)abstract
- The extensive use of heat exchangers in the industry makes its optimization be crucial for raising efficiency and energy conservation. In the context of cleaner production and energy sustainability of the industrial sector, energy efficiency is a cornerstone to reduce fuel consumption. In this way the performance of the heat exchanger is a key factor. This work aims to contribute to energy efficiency, for this purpose a multi-objective optimization of the thermal and hydraulic design of heat exchangers of shell and tubes is implemented. A meta-heuristic technic of genetic algorithm, using two fitness functions, number of entransy dissipation and total cost was programed. Finally it is obtained the Peto front with multiple solutions, these solutions where adjusted to the operating conditions.
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| 8. |
- Mesfun, Sennai, et al.
(författare)
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Integrated SNG production in a typical Nordic sawmill
- 2015
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Ingår i: ECOS 2015. - : International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems. - 9782955553909
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Konferensbidrag (refereegranskat)abstract
- Advanced biomass based motor fuels and chemicals are becoming increasingly important to replace fossil energy sources within the coming decades. It is likely that the new biorefineries will evolve mainly from existing forest industry sites as they already have the required biomass handling infrastructure in place. The main objective of this work is to assess the potential for increasing the profit margin from sawmill byproducts by integrating innovative downstream processes. The focus is on the techno-economic evaluation of an integrated site for bio-SNG production. The option of using the syngas in a b-IGCC for the production of electricity (instead of SNG) is also considered for comparison. The process flowsheets that are used to analyse the energy and material balances are modelled in MATLAB and Simulink. A mathematical process integration model of a typical Nordic sawmill is used to analyse the effects on the energy flows in the overall site as well as to evaluate the site economics. Different plant sizes have been considered in order to assess the economy-of-scale effect. The technical data required as input are collected from the literature and, in some cases, from experiments. The investment cost is evaluated on the basis of conducted studies, third party supplier budget quotations and in-house database information. This paper presents complete material and energy balances of the considered processes and the resulting process economics.
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| 9. |
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| 10. |
- Sundqvist, Maria, et al.
(författare)
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System analysis of integrating fast pyrolysis to an iron and steel plant
- 2015
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Ingår i: ECOS 2015 - 28th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems. - : International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems. - 9782955553909
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Konferensbidrag (refereegranskat)abstract
- The reducing of CO2 allowance promotes steel industry to mitigate CO2 emissions. Utilization of biomass e.g., as injectants in the blast furnace to replace pulverized coal (PC), has been proposed as one promising option to meet these requirements in the short- Term. The aim of this work is to integrate a biomass fast pyrolysis to the iron and steel industry and to investigate the potential effects on the energy consumption and CO2 emission. In this work, an iron and steel plant from Sweden was chosen as a case study. An optimization model was extended to cover the fast pyrolysis units in the system boundary. The fast pyrolysis plant produces different types of biomass products i.e., bio-char, bio-oil and bio-syngas. Different alternative to utilize biomass products within the system were included in the model. The investigation shows that the integration of a fast pyrolysis units has great potential on, not only reducing CO2 emission, the potential energy savings.
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