| 1. |
- De, S., et al.
(författare)
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Development of an artificial neural network model for the steam process of a coal biomass cofired combined heat and power (CHP) plant in Sweden
- 2007
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Ingår i: Energy. - : Elsevier BV. - 1873-6785 .- 0360-5442. ; 32:11, s. 2099-2109
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Tidskriftsartikel (refereegranskat)abstract
- The development of a model for any energy system is required for proper design, operation or its monitoring. Models based on accurate mathematical expressions for physical processes are mostly useful to understand the actual operation of the plant. However, for large systems like combined heat and power (CHP) plants, such models are usually complex in nature. The estimation of output parameters using these physical models is generally time consuming, as these involve many iterative solutions. Moreover, the complete physical model for new equipment may not be available. However, artificial neural network (ANN) models, developed by training the network with data from an existing plant, may be very useful especially for systems for which the full physical model is yet to be developed. Also, such trained ANN models have a fast response with respect to corresponding physical models and are useful for realtime monitoring of the plant. In this paper, the development of an ANN model for the biomass and coal cofired CHP plant of Visthamnsverket at Helsingborg, Sweden has been reported. The feed forward with back propagation ANN model was trained with data from this plant. The developed model is found to quickly predict the performance of the plant with good accuracy. (C) 2007 Elsevier Ltd. All rights reserved.
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| 2. |
- Ericsson, Karin
(författare)
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Co-firing - A strategy for bioenergy in Poland?
- 2007
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Ingår i: Energy. - : Elsevier BV. - 1873-6785 .- 0360-5442. ; 32:10, s. 1838-1847
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Tidskriftsartikel (refereegranskat)abstract
- Biomass provides the largest reduction of carbon dioxide (CO2) emission when it replaces coal, which is the dominating fuel in heat and electricity production in Poland. One means of replacing coal with biomass is to co-fire biofuels in an existing coal-fired boiler. This paper presents an analysis of the strengths and weaknesses of co-firing biofuels in Poland with respect to technical, environmental, economical and strategic considerations. This analysis shows that co-firing is technically and economically the most realistic option for using biofuels in the large pulverized fuel (PF) boilers in Poland. However, from an environmental perspective, co-firing of biofuels in large combined heat and power (CHP) plants and power plants provides only a small reduction in sulphur dioxide (SO2) emission per unit biofuel, since these plants usually apply some form of desulphurization technology. In order to maximize the SO2 emission reduction, biofuels should be used in district heating plants. However, co-fired combustion plants can handle disruptions in biofuel supply and are insensitive to moderate changes in fuel prices, which makes them suitable utilizers of biofuels from perennial energy crops. Co-firing could therefore play an important role in stimulating perennial crop production.
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| 3. |
- Fredriksson Möller, Björn, et al.
(författare)
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CO2-free power generation in combined cycles - Integration of post-combustion separation of carbon dioxide in the steam cycle
- 2006
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Ingår i: Energy. - : Elsevier BV. - 1873-6785 .- 0360-5442. ; 31:10-11, s. 1520-1532
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Tidskriftsartikel (refereegranskat)abstract
- Ever since the release of the Kyoto protocol the demand for CO2-free processes have been increasing. One of the most expanding sources of electric power in the industrialised world today is the gas-fired combined cycle, combining high efficiency and low investment cost. In this paper, the integration of a post-combustion CO2-separation unit into a combined cycle is studied from a thermodynamic and economic point-of-view. A standard dual-pressure combined cycle is chosen as a reference cycle. It is compared to a dual-pressure combined cycle and a triple-pressure combined cycle with the lowest pressure level producing steam for a CO2-separation unit. The steam pressure levels in the different cycles are optimised for maximum efficiency and minimum specific cost, respectively, using genetic algorithms. The efficiency drop due to CO2-separation is approximately 8% points, from 54 to 46%. The specific cost of the power plant is expected to increase with almost 100% and the cost of electricity with approximately 30%. In several countries a carbon dioxide tax is already introduced as an incentive for more efficient power cycles and use of fuels with lower content of coal. The result above implies that the level of such a tax would be in the order of 30% of the price of electricity to encourage CO2-free power generation.
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| 4. |
- Fredriksson Möller, Björn, et al.
(författare)
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On the off-design of a natural gas-fired combined cycle with CO2 capture
- 2007
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Ingår i: Energy. - : Elsevier BV. - 1873-6785 .- 0360-5442. ; 32:4, s. 353-359
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Tidskriftsartikel (refereegranskat)abstract
- During the last 15 years cycles with CO, capture have been in focus, due to the growing concern over our climate. Often, a natural gas fired combined cycle with a chemical absorption plant for CO, capture from the flue gases have been used as a reference in comparisons between cycles. Neither the integration of the steam production for regeneration of amines in the combined cycle nor the off-design behaviour of such a plant has been extensively Studied before. In this paper, the integration of steam production for regeneration of the amines is modelled at design load and studied in off-design conditions for a combined cycle. Different ambient conditions and part-load strategies and their influence on the cycle performance are also examined. Of particular interest is a novel strategy with the possibility of longer life of gas turbine blading, with marginal loss in efficiency. The off-design performance of the combined cycle is modelled in a rigorous Way using a gas turbine performance deck, while the boiler is calculated using simplified correlations for oft-design heat transfer and pressure drop. The steam turbine calculation is based on verified models for the flow-pressure-efficiency relations, whilst the steam condenser is based oil the HEI method.
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| 5. |
- Grönkvist, Stefan, et al.
(författare)
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Oxygen efficiency with regard to carbon capture
- 2006
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 31:15, s. 3220-3226
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Tidskriftsartikel (refereegranskat)abstract
- Carbon capture is often discussed in the literature with the sole focus on power processes, despite the fact that carbon dioxide emissions from other sources are just as relevant for the impact on the atmosphere. Furthermore, some carbon capture methods are relatively inefficient when applied to power production processes. Carbon capture should preferably be performed where the cost is as low as possible, i.e. not necessarily from power production processes. As an example, carbon capture using combustion with pure oxygen is far more energy efficient if it is used together with lime kilns or cement kilns than together with power production processes. A new concept termed "oxygen efficiency" is introduced in this paper. It describes the amount of carbon dioxide that can potentially be captured per unit of oxygen. As such, the oxygen efficiency quantifies the value of a certain unit of oxygen for carbon capture reasons. The base concept is that the energy penalty for the production of one part of oxygen is the same no matter where it is produced; hence, if this unit of oxygen can be used to capture more carbon dioxide, it is more efficient. Typically, the oxygen efficiency would be five times greater for carbon capture when utilising pure oxygen together with cement kilns rather than together with methane-fired power plants. Furthermore, the concept of oxygen efficiency illustrates the importance of considering how carbon capture methods can be utilised in the most efficient way, in addition to evaluating which carbon capture method is the most suitable for a particular technology.
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| 6. |
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| 7. |
- Höök, Mikael, 1982-, et al.
(författare)
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Future Danish oil and gas export
- 2009
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 34:11, s. 1826-1834
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Tidskriftsartikel (refereegranskat)abstract
- Denmark possesses only a small share of the exploitation rights to North Sea oil and is a minor producer when compared to Norway and the UK. However, Denmark is still an oil exporter and a very important supplier of oil for certain countries, in particular Sweden. A field-by-field analysis of the Danish oil and gas fields, combined with estimated production contribution from new field developments, enhanced oil recovery and undiscovered fields, provides a future production outlook. The conclusion from this analysis is that by 2030 Denmark will no longer be an oil or gas exporter at all. Our results are also in agreement with the Danish Energy Authority’s own forecast, and may be seen as an independent confirmation of their general statements. Decreasing Danish oil production, coupled with a rapid decline in Norway’s oil output, will force Sweden to import oil from more distant markets in the future, dramatically reducing Swedish energy security. If no new gas suppliers are introduced to the Swedish grid, then Swedish gas consumption is clearly predestined to crumble alongside declining Danish production. Future hydrocarbon production from Denmark displays a clear link to Sweden’s future energy security.
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| 8. |
- Jonsson, M., et al.
(författare)
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Humidified gas turbines - a review of proposed and implemented cycles
- 2005
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 30:7, s. 1013-1078
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Forskningsöversikt (refereegranskat)abstract
- Gas turbines with air-water mixtures as the working fluid promise high electrical efficiencies and high specific power outputs to specific investment costs below that of combined cycles. Different humidified gas turbine cycles have been proposed, for example direct water-injected cycles, steam-injected cycles and evaporative cycles with humidification towers. However, only a few of these cycles have been implemented and even fewer are available commercially. This paper comprehensively reviews the literature on research and development on humidified gas turbines and identifies the cycles with the largest potential for the future. In addition, the remaining development work required for implementing the various humidified gas turbine cycles is discussed. This paper can also be used as a reference source that summarizes the research and development activities on humidified gas turbines in the last three decades.
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| 9. |
- Lazzaretto, Andrea, et al.
(författare)
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A method to separate the problem of heat transfer interactions in the synthesis of thermal systems
- 2008
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 33:2, s. 163-170
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Tidskriftsartikel (refereegranskat)abstract
- Most of the efforts to improve energy system configurations are directed towards the recovery of internal heat, which reduces the contribution of the external hot source and enhance system efficiency accordingly. This problem is strictly related to the synthesis of different components into system topology, i.e. with the definition of the optimal system configuration according to specified objectives. A new method for the optimization of the heat transfer interactions within energy systems is presented here, based on the idea of cutting thermal links between the "basic" components of the system. The boundary temperatures of hot and cold flows that are generated as a consequence of these cuts are evaluated in an optimization procedure that involves the design parameters of the system as well. The high potential of the proposed method consists in separating the problem of defining the system configuration into two separate sub-problems, the first regarding the definition of the "basic" topology of the system (related to all components different from the heat exchangers), the second the optimal heat transfer interactions within the system. This feature makes complex systems today only marginally "optimizable", amenable to complete optimization. The method is applied to a humid air turbine (HAT) cycle plant, which represents a good test to prove its reliability and generality, due to the internal recirculation of mass and energy flows
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| 10. |
- Lazzaretto, Andrea, et al.
(författare)
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Four approaches compared on the TADEUS (thermoeconomic approach to the diagnosis of energy utility systems) test case
- 2006
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 31:10-11, s. 1586-1613
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Tidskriftsartikel (refereegranskat)abstract
- Four approaches to the diagnosis of malfunctions in energy systems are presented and applied to the same test case plant. The paper is part of a project, started in 2001 and named thermoeconomic approach to the diagnosis of energy utility systems (TADEUS), aimed at integrating various experiences accumulated by a group of researchers operating in the thermoeconomic diagnostics, a field of research started by Antonio Valero and co-workers in 1990 and then followed by various people all over the world. It is shown how, starting from the same basic set of ideas, researchers developed different approaches, each one having peculiar characteristics that are, however, complementary to each other
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