| 1. |
- Beiron, Johanna, 1992, et al.
(författare)
-
A multiple system level modeling approach to coupled energy markets: Incentives for combined heat and power generation at the plant, city and regional energy system levels
- 2022
-
Ingår i: Energy. - : Elsevier BV. - 0360-5442. ; 254
-
Tidskriftsartikel (refereegranskat)abstract
- The energy system can be subdivided into interconnected structural levels with differing boundary conditions and objectives. For heat and power generation, these levels may be the: electricity price area (regional); heat price area (city); and production site (power plant). This work presents a multi-system modeling approach for the analysis of investments and operation of combined heat and power (CHP) plants, as optimized on a regional, city, or production site energy system level. The modeling framework, comprising three energy system optimization models at the respective levels, is applied to a case study of Sweden, electricity price area SE3. The modeling levels are optimized separately but linked through electricity and heat prices. The results show that optimized CHP plant investments and operation on the three levels can both align and differ, depending on conditions. With a low biomass price and moderate congestion in transmission capacity into the city, the results from the three levels generally align. Differences arise if the biomass price is increased, which impacts the competitiveness of CHP plants in the region, while city-level CHP investments are mainly determined by the local heat demand and less-sensitive to external changes. The differences indicate a risk for diverging expectations between system levels.
|
|
| 2. |
- Beiron, Johanna, 1992, et al.
(författare)
-
Flexibility provision by combined heat and power plants – An evaluation of benefits from a plant and system perspective
- 2022
-
Ingår i: Energy Conversion and Management: X. - : Elsevier BV. - 2590-1745. ; 16
-
Tidskriftsartikel (refereegranskat)abstract
- Variable renewable electricity generation is likely to constitute a large share of future electricity systems. In such electricity systems, the cost and resource efficiency can be improved by employing strategies to manage variations. This work investigates combined heat and power (CHP) plant flexibility as a variation management strategy in an energy system context, considering the operation and cost-competitiveness of CHP plants. An energy system optimization model with detailed representation of CHP plant flexibility is applied, covering the electricity and district heating sectors in one Swedish electricity price area. The results show that investments in CHP plants are dimensioned based on the demand for district heating rather than electricity. In the system studied, this implies that CHP plant capacity is small relative to electricity system variations, and variation management using CHP plants has a weak impact on the total system cost of supplying electricity and district heating. However, flexibility measures increase CHP plant competitiveness in scenarios with low system flexibility (assuming low availability of hydropower or no thermal energy storage) although investments in CHP capacity are sensitive to fuel cost. It is found that while district heating is the dominant CHP product (constituting 50%–90% of the annual CHP energy output), the dispatchable electricity supply has a high value and comprises around 60% of the annual CHP plant revenue. In all scenarios, operational flexibility of the boiler is more valuable than a flexible steam cycle power-to-heat ratio.
|
|
| 3. |
- Òsk Gardarsdòttir, Stefanìa, 1987, et al.
(författare)
-
Improving the flexibility of coal-fired power generators: Impact on the composition of a cost-optimal electricity system
- 2018
-
Ingår i: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 209, s. 277-289
-
Tidskriftsartikel (refereegranskat)abstract
- A transformation of the electricity generation system is required to drastically reduce the associated CO2 emissions. In future systems, variable renewable energy sources (wind and solar) are expected to provide a significant fraction of the electricity supply, increasing the requirement for variation management compared with today´s situation. This paper investigates the impacts of measures designed to increase the competitiveness of coal-fired power plants in future energy systems, which are facing restrictions related to CO2 emissions and variable operation as a consequence of high penetration levels of wind and solar power. We investigate the cost-optimal compositions of three regional electricity generation systems with different conditions for generation using renewables with a linear cost-minimizing investment model. The model is applied in two energy policy scenarios: one with a tight cap on CO2 emissions, and one with a stringent requirement for generation from renewables. In a system with a stringent requirement for electricity generation from renewables but without a CO2 cap, coal-based technologies with improved cycling properties provide variation management, given that the development of measures for ensuring improved flexibility continues and reaches full-scale implementation at moderate cost. The effects of improved cycling properties on the system composition are especially relevant for regions with moderate potential for wind and solar generation, in that they reduce wind curtailment and improve the underlying conditions for investments in solar power. In the system with a tight CO2 cap, only coal-based technologies with Carbon Capture and Storage (CCS) and co-firing of biomass are feasible. Increasing the share of biomass in co-firing technologies to achieve negative CO2 emissions increases the competitiveness of these technologies to a greater extent than if simply the cycling properties are improved. A larger co-firing fraction reduces the total system costs, since it facilitates the provision of low-cost flexibility by Natural Gas Combined Cycle (NGCC) plants, and it is especially important in regions where nuclear power is otherwise cost-competitive, as low-cost flexibility stimulates investments in wind and solar power at the expense of nuclear power.
|
|
| 4. |
- Ajdari, Sima, 1985, et al.
(författare)
-
Evaluation of Operating and Design Parameters of Pressurized Flue Gas Systems with Integrated Removal of NO x and so x
- 2019
-
Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 33:4, s. 3339-3348
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigates the operating and design parameters of product gas compression and integrated control of nitrogen oxides (NO x ) and sulfur oxides (SO x ) in large-scale oxy-fuel and chemical looping combustion processes. A process model that includes a comprehensive description of nitrogen and sulfur chemistry and mass transfer is developed. The results show that the fraction of NO oxidation into NO 2 will be 10-50% in a multistage compressor to 30 bars (1-4% O 2 in the gas) depending on the residence times in intercoolers and pressure levels. At lower O 2 concentrations (>0.1% O 2 in the gas), the oxidation is limited but still active. Nitric acid formation in the compressor condensate is, thus, inevitable, although limited, as most water is condensed in the early stages, whereas the acid gases are formed in the later stages. The NO 2 /NO x ratio has an important effect on the total amount of NO x absorbed and extra residence time should be added after the compressor to increase this ratio. Evaluation of the process behavior in relation to simultaneous absorption of SO 2 and NO x revealed that increased SO 2 /NO x ratio and bottom liquid recycling enhanced the total NO x absorption. In addition, maintaining the pH in the absorbing solution above 5 improves the removal efficiencies of NO x and SO 2 . NO x removal rates of up to around 95% can be achieved for SO 2 /NO x > 1 in the flue gas with appropriate design of the absorber. For SO 2 /NO x < 1, increasing the packing height or addition of S(IV) solutions could enhance the NO x removal rates to 95% or more. The model predictions are compared with the experimental data from a laboratory-scale absorber. The process model developed in this work enables design studies and techno-economic evaluation of absorption-based NO x and SO x removal concepts.
|
|
| 5. |
- Ajdari, Sima, 1985, et al.
(författare)
-
Formation and Control of NOx and SOx in Pressurized Oxy-Combustion Systems
- 2015
-
Ingår i: The Proceedings of the 40th International Technical Conference on Clean Coal & Fuel Systems, 31 May-4 June 2015, Clearwater, Florida, USA.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The formation and control of NOx and SOx in pressurized oxy-fuel combustion systems is discussed in the present work. The chemistry of nitrogen and sulfur species under pressurized conditions and the experiences gained from operating atmospheric oxy-fuel combustion pilot plants are reviewed in brief. In a conventional combustion and gas cleaning process, SO2 and NO are the principle NOx and SOx species. However, the oxidation of NO to NO2 and SO2 to SO3 is favored by low temperature and high pressure. In the present paper we will make a first modelling based of the altered oxidation conditions during both high and low temperature conditions in pressurized oxy-combustion. Besides the gas-phase oxidation, the liquid-phase N-S interactions will further enhance the formation of acids in the flue gas condensate. Thus, these low and high temperature processes will be discussed in the present work due to their relevance for the design of the flue gas compression and gas cleaning system in pressurized oxy-combustion.
|
|
| 6. |
|
|
| 7. |
- Ajdari, Sima, 1985, et al.
(författare)
-
Modeling the Nitrogen and Sulfur Chemistry in Pressurized Flue Gas Systems
- 2015
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 54:4, s. 1216-1227
-
Tidskriftsartikel (refereegranskat)abstract
- A rate-based model is developed to elucidate the chemistry behind the simultaneous absorption of NOx and SOx under pressurized conditions (pressures up to 30 bar) that are applicable to the flue gases obtained from CO2 capture systems. The studied flue gas conditions are relevant to oxy-fuel and chemical-looping combustion systems. The kinetics of the reactions implemented in the model is based on a thorough review of the literature. The chemistry of nitrogen, sulfur, and N-S interactions are evaluated in detail, and the most important reaction pathways are discussed. The effects of pH, pressure, and flue-gas composition on the liquid-phase chemistry are also examined and discussed. Simulations that use existing kinetic data reveal that the pH level has a strong influence on the reaction pathway that is followed and the types of products that are formed in the liquid phase. In addition, the pressure level and the presence of NOx significantly affect the removal of SO2 from the flue gas.
|
|
| 8. |
|
|
| 9. |
- Ajdari, Sima, 1985, et al.
(författare)
-
NOx AND SOx CHEMISTRY IN PRESSURIZED FLUE GAS SYSTEMS: IMPORTANCE FOR CHEMICAL LOOPING COMBUSTION
- 2014
-
Ingår i: 3rd International Conference on Chemical Looping, 9-11 September 2014, Gothenburg, Sweden.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The control of NOx and SOx in chemical-looping combustion systems is discussed with the focus on the importance of the pressurized flue-gas train. The chemistry of nitrogen and sulfur under pressurized conditions and the experiences gained from operating oxy-fuel combustion pilot plants that pertain to chemical looping are reviewed. In the flue gases from the combustion process, SO2 and NO are the principle NOx and SOx species. The oxidation of NO to NO2 is favored by low temperature and high pressure and is enhanced during the compression of flue gases. The oxidation of NO to NO2 in the flue-gas train is significant at pressures >15 bar. The solubilities of NO2 and SO2 in water are high and results in the formation of acids. Once NOx and SOx are absorbed, the liquid-phase N-S interactions lead to the formation of sulfuric and nitric acids. Thus, the chemistry of NOx and SOx is of importance for flue-gas conditioning of chemical-looping combustion systems. Similar to oxy-fuel combustion, the conditions in the chemical-looping flue-gas train offer new opportunities for the design of NOx and SOx removal processes.
|
|
| 10. |
|
|
