The use of waste for energy purposes becomes increasingly interesting both with respect to waste management and for the energy systems. The decisions on alternative uses of waste for energy are mainly influenced by different policies, waste management, energy supply and use, as well as technologies. Two important issues, namely, a clear priority of waste prevention in waste management within EU and the growing concern for food losses and food waste at global and at national level, shall be carefully considered and addressed. This paper proposes scenarios for waste to energy systems with focus on Sweden and with a broader EU approach is applied: Biofuels Sweden, Electric vehicles and Bioenergy Europe. As baseline for the scenario development inventory of waste-to-energy related policies and goals on international, national, regional and local level as well as inventory of existing scenarios and reports with future trends is made. A low waste availability level is recommended to be included in sensitivity analysis for scenarios.
The use of waste for energy purposes becomes increasingly interesting with respect to waste management and the energy systems. The decisions on alternative uses of waste for energy are mainly influenced by different policies, waste management, energy supply and use, as well as technologies. Two important issues, namely, a clear priority of waste prevention in waste management within EU and the growing concern for food losses and food waste at global and national level, shall be carefully considered and addressed. This paper proposes policy based scenarios for waste-to-energy systems with a focus on Sweden and with a broader EU approach. As baseline for the scenario development an inventory of waste-to-energy related policies and goals on international, national, regional and local level as well as inventory of existing scenarios and reports with future trends is made. The main substitute for fossil fuels and the possibilities for renewable energy export are basic elements that define scenarios. Biofuels and electricity are identified as main substitutes for the fossil fuels. A low waste availability level is recommended to be included in sensitivity analysis for scenarios. This paper assumes relative decoupling in Low Waste scenario in 2030, and absolute decoupling first in 2050.
Energy recovery from waste becomes increasingly interesting both with respect to waste management and for the sustainable energy supply. The REMOWE (Regional Mobilizing of Sustainable Waste-to-Energy Production) project, seeks to facilitate the implementation of sustainable systems for waste-to-energy in the project regions. Based on investigations done within the REMOWE project this paper discusses increased waste-to-energy utilization in Poland with focus on a comparison with the current state in Sweden. There are big differences between Sweden and Poland, and between Lower Silesia Voivodship in Poland and Västmanland County in Sweden. The REMOWE project through its outputs and discussions during meetings support transfer of technology, knowledge and best practice. Procedural justice and early involvement of public can increase social acceptance and successful implementation of projects regarding incineration, biogas production and separate collection of biodegradable waste.
There are four possible transportation means that could be used to deliver CO2: motor carriers, railway carriers, water carriers, and pipeline. The impurities in CO2-fluids have significant impacts on the thermodynamic properties that will further affect the design, operation and cost of CO2 transport. This paper focuses on how impurities in CO-fluids affect thermodynamic properties, and how the changes of properties affect CO2 transport process. Vapor-liquid equilibrium (VLE), critical point and densities are essential thermodynamic properties for designing a CO2 transport process. Studies on these properties will be carried out for CO2-mixtures based on the combinations of the common impurities such as SO2, H2S, CH4, Ar, O-2 and N-2. Moreover with a real case of pipeline for CO transport, the impact of impurities on transport process will be demonstrated in more details.
Oxy-fuel combustion is one of promising technologies for CO2 capture, which uses simple flue gas processing normally including compression, dehydration and purification/liquefaction (non-condensable gas separation). However relatively high levels of impurities in the flu gas present more challenges for the gas processing procedure. This paper studied the sensitivity of operating parameters to inlet composition, the effects of impurities on energy consumption, and the relationship between energy consumption and operating parameters. Results show that comparatively the total compression work is more sensitive to the composition of SO2 if the total mass flow is constant; while the operating temperature of purification is more sensitive to N-2. To pursue the minimum energy consumption, from the viewpoint of impurity, the content Of O-2, N-2, Ar and H2O should be lowered as much as possible, which means the amount of air leakage into the system and excess oxygen should be controlled at a low level in the combustion; as to SO2, if it is possible to co-deposit with CO2, its existence may be helpful to decrease compression work. From the viewpoint of operating parameters, low intermediate pressure, high intercooling temperature and high outlet pressure are favorable to achieve high energy utilization, if heat recovery is considered.
Energy recovery from waste treatment is of great significance for the waste management and sustainable energy supply. Sweden has proposed an ambitious vision of zero net greenhouse gases emissions by 2050, which makes most possible use of resources that the waste represents necessary. This paper is to study how the waste-to-energy (WtE) can interact with other forms of renewable energy to affect the energy supply and demand in Sweden. Based on an assumption of waste generation-treatment balance in 2050 with two cases, power preference and motor fuels preference, are investigated under diverse WtE scenarios. The results indicate that WtE production can contribute to the primary energy supply by 38 to 186 TWh, amounting to 6% to 47% of the total. The power production can be ranged from 7 to 35 TWh and motor fuels from 2 to 34 TWh through under different WtE scenarios. Furthermore, the final mitigation of CO2 emission is estimated to be from 1 to 12 Mt in 2050 compared to base year of 2010, really depending on which WtE scenario is considered.
A dynamic model of a regional energy system has been developed to support sustainable waste treatmentwith greenhouse gases (GHG) mitigation, addressing the possibility for development towardsa regional fossil fuel-free society between 2011 and 2030. The model is based on conventional mixedinteger linear programming (MILP) techniques to minimize the total cost of regional energy systems. TheCO2 emission component in the developed model includes both fossil and biogenic origins whenconsidering waste, fossil fuels and other renewable sources for energy production. A case study for thecounty of Västmanland in central Sweden is performed to demonstrate the applicability of the developedMILP model in five distinct scenarios. The results show significant potential for mitigating CO2 emissionby gradually replacing fossil fuels with different renewable energy sources. The MILP model can be usefulfor providing strategies for treating wastes sustainably and mitigating GHG emissions in a regionalenergy system, which can function as decision bases for formulating GHG reduction policies andassessing the associated economic implications.
Three optional pellet production processes integrated with an existing biomass-based CHP plant using different raw materials (wood chips and solid hydrolysis residues) are studied. The year is divided into 12 periods, and the integrated biorefinery systems are modeled and simulated for each period. The annual economic performance of three integrated biorefinery systems is analyzed based on the simulation results. The option of pellet production integrated with the existing CHP plant with the exhaust flue gas and superheated steam as drying mediums has the lowest specific pellet production cost of 105 €/tpellet, the shortest payback time of less than 2 years and the greatest CO2 reduction of the three options. An advantage in common among the three options is a dramatic increase of the total annual power production and significant CO2 reduction in spite of a small decrease of power efficiency.
Bioethanol is an alternative to fossil fuels in the transportation sector. The use of pellet for heating is also an efficient way to mitigate greenhouse gas emissions. This paper evaluates the techno-economic performance of a biorefinery system in which an existing combined heat and power (CHP) plant is integrated with the production of bioethanol and pellet using straw as feedstock. A two-stage acid hydrolysis process is used for bioethanol production, and two different drying technologies are applied to dry hydrolysis solid residues. A sensitivity analysis is performed on critical parameters such as the bioethanol selling price and feedstock price. The bioethanol production cost is also calculated for two cases with either 10 year or 15 year payback times. The results show that the second case is currently a more feasible economic configuration and reduces production costs by 36.4%-77.3% compared to other types of poly-generation plants that are not integrated into existing CHP plants.
Abstract: Bioethanol is considered an alternative to fossil fuels in the transportation sector. The use of pellets for heating is another efficient way to mitigate greenhouse gas emissions. This paper evaluates the techno-economic performance of a biorefinery system in which an existing combined heat and power plant integrates with the productions of bioethanol and pellets using straw as feedstock. A two-stage acid hydrolysis process for bioethanol production is used, and two different drying technologies are chosen for drying hydrolysis solid residues. A sensitivity analysis on critical parameters, such as the bioethanol selling price and feedstock price, is performed. The bioethanol production cost is also calculated for two cases at the conditions of ten-year and five-year payback time. The results show that the first case is a more feasible economic configuration at present, having an over 30% production cost reduction compared with the conventional cogeneration plants of bioethanol and solid fuel.
One of the by-products from bioethanol production using woody materials is lignin solids, which can be utilized as feedstock for combined heat and power (CHP) production. In this paper, the influence of integrating a drying process into a biomass-based polygeneration system is studied, where the exhaust flue gas is used to dry the lignin solids instead of direct condensation in the flue gas condenser (FGC). The evaporated water vapor from the lignin solids is mixed with the drying medium for consequent condensation. Thus, the exhaust flue gas after the drying still has enough humidity to produce roughly the same amount of condensation heat as direct condensation in the existing configuration. The influence of a drying process and how it interacts with the FGC in CHP production as a part of the polygeneration system is analyzed and evaluated. If a drying process is integrated with the polygeneration system, overall energyefficiency is only increased by 3.1% for CHP plant, though the power output can be increased by 5.5% compared with the simulated system using only FGC.
Many key aspects of society, such as transport, housing and health care, have been significantly improved by the advent of a range of electricity applications, and the power generation for electricity applications has been a major field of research. Photovoltaic (PV) self-powered technologies are promising technologies for addressing applications' power supply challenges and alleviating conventional electricity load and environmental pollution. This study reviews solar energy harvesting (SEH) technologies for PV self-powered applications. First, the PV power generation and scenarios of PV self-powered applications are analyzed. Second, analysis of system design for PV self-powered applications is presented. Third, key components for PV self-powered applications, including maximum power point tracking (MPPT) techniques and power management (PM) systems are discussed in detail. Furthermore, numerous PV self-powered applications and utilizations of energy harvesting are summarized. Finally, some recommendations are proposed for further research.
Biogas produced from anaerobic digestion processes is considered as an important alternative to natural gas and plays a key role in the emerging market for renewable energy. Aiming at achieving a more sustainable and efficient biomethane production, this work proposed a novel energy system, which integrates concentrating photovoltaic/thermal (C-PV/T) hybrid modules into a biogas plant with chemical absorption for biogas upgrading. The investigated energy system was optimized based on the data from an existing biogas plant, and its techno-economic feasibility was evaluated. Results show that about 7% of the heat consumption and 12% of the electricity consumption of the biogas plant can be covered by solar energy, by using the produced heat in a cascade way according to the operating temperature of different processes. The production of biomethane can also be improved by 25,800 N m3/yr (or 1.7%). The net present value of the integrated system is about 2.78 MSEK and the payback period is around 10 years. In order to further improve the economic performance, it is of great importance to lower the capital cost of the C-PV/T module.
Considering the current challenges posed by energy structural transformation on remote islands, the technical and economic assessment of a hybrid renewable power system were performed considering the Huraa Island of Maldives as a case study. This work models and discusses possible hybrid power system configuration modes based on varying combinations of diesel power, solar photovoltaic (PV) power, wind power, and battery storage. For each mode, the effects of the installed capacity on renewable penetration (RP) and levelized cost of electricity (LCOE) were analyzed. Furthermore, the configuration modes were compared, and optimal operation schemes were developed by considering RP, LCOE, and CO2 emissions. The results suggest that the use of a high-rated PV power is optimal owing to its high RP and low LCOE. However, when wind power is available, a wind power rating of 1000 kW is an optimal solution, followed by a 500-kW rating; when battery storage is used, a battery capacity of 4000 kWh is ideal. Moreover, it is unnecessary to combine battery storage with these power schemes when an RP <53% is acceptable. The recommended maximum available RP is approximately 96% when using an 1800 kW PV, 1000 kW wind, and 4000 kWh battery storage system.
In general, the post-combustion capture of CO2 is costly; however, swing adsorption processes can reduce these costs under certain conditions. This review highlights the issues related to adsorption-based processes for the capture of CO2 from flue gas. In particular, we consider studies that investigate CO2 adsorbents for vacuum swing or temperature swing adsorption processes. Zeolites, carbon molecular sieves, metal organic frameworks, microporous polymers, and amine-modified sorbents are relevant for such processes. The large-volume gas flows in the gas flue stacks of power plants limit the possibilities of using regular swing adsorption processes, whose cycles are relatively slow. The structuring of CO2 adsorbents is crucial for the rapid swing cycles needed to capture CO2 at large point sources. We review the literature on such structured CO2 adsorbents. Impurities may impact the function of the sorbents, and could affect the overall thermodynamics of power plants, when combined with carbon capture and storage. The heat integration of the adsorption-driven processes with the power plant is crucial in ensuring the economy of the capture of CO2, and impacts the design of both the adsorbents and the processes. The development of adsorbents with high capacity, high selectivity, rapid uptake, easy recycling, and suitable thermal and mechanical properties is a challenging task. These tasks call for interdisciplinary studies addressing this delicate optimization process, including integration with the overall thermodynamics of power plants. © 2012 Elsevier Ltd.
In general, the post-combustion capture of CO2 is costly; however, swing adsorption processes can reduce these costs under certain conditions. This review highlights the issues related to adsorption-based processes for the capture of CO2 from flue gas. In particular, we consider studies that investigate CO2 adsorbents for vacuum swing or temperature swing adsorption processes. Zeolites, carbon molecular sieves, metal organic frameworks, microporous polymers, and amine-modified sorbents are relevant for such processes. The large-volume gas flows in the gas flue stacks of power plants limit the possibilities of using regular swing adsorption processes, whose cycles are relatively slow. The structuring of CO2 adsorbents is crucial for the rapid swing cycles needed to capture CO2 at large point sources. We review the literature on such structured CO2 adsorbents. Impurities may impact the function of the sorbents, and could affect the overall thermodynamics of power plants, when combined with carbon capture and storage. The heat integration of the adsorption-driven processes with the power plant is crucial in ensuring the economy of the capture of CO2, and impacts the design of both the adsorbents and the processes. The development of adsorbents with high capacity, high selectivity, rapid uptake, easy recycling, and suitable thermal and mechanical properties is a challenging task. These tasks call for interdisciplinary studies addressing this delicate optimization process, including integration with the overall thermodynamics of power plants.
This paper addresses the potential of sustainability improvement by increased efficiencyin milk and cattle production. The experience of Swedish improvement over the last half centuryreveals the global potential for the sustainable management of land use, nutrition balance andbioenergy supply.Ruminants are an important part of the global food production system. Ruminantproduction has the potential to substantially increase land area available for bioenergy production.They can use energy in foodstuffs with none human nutritive value and simple nitrogencompounds in the production of high quality feeds. They can convert renewable natural resourcesfrom ecosystems, that otherwise have low capacity to transform solar energy fluxes to food, tohigh quality food.Globally, the area of pasture is 2.5 times larger than the area of cropland. Ruminants arean important part of the global food system, supplying human energy metabolism. Due to thecompetition for land, the skilfulness in rumen production affects potentials for green energyproduction supplying the energy metabolism in the technical systems of society.This paper discusses two aspects of ruminant production affecting the potential for greenenergy production:(i) The impact of increased nutritional physiological efficiency, i.e., better feedingstrategies, and(ii) The importance of utilising ruminants as ruminants, where they transform solar energyfluxes to high quality foodstuffs from ecosystems with low capacity to produce food throughother paths.The focal point is the impact on the land remaining for green energy production supplyingthe technical systems of society, after food supply needs are met. Estimates are provided on theimpact on other sustainability aspects at different system levels as well as in the threesustainability-dimensions. The results are provided through the application of a methodologywithin the frame of integrated assessment for analysis of sustainability effects in systems withmutual dependencies between systems and system levels. This is of general interest as amethodology, supporting the development of sustainable green energy production and meetingthe needs of society. It contributes with concrete results, supporting an increased sustainableproduction of green energy due to increased efficiency within a sector that competes for land
This paper studied the integration of Evaporative Gas Turbine (EvGT) cycle with oxy-fuel combustion for CO2 capture. The impact of key parameters on system electrical efficiency, such as the oxygen purity, Water/Gas ratio (W/G) has been investigated concerning thermal efficiency. The performance of dry recycle and wet recycle also has be analyzed and compared. Simulation results shows that: (1) 97% can be considered as the optimum oxygen purity taking into account the trade-off between the air separation unit (ASU) consumption penalty of producing higher-purity oxygen and electrical efficiency; (2) there exists an optimum point of W/G for both EvGT and EvGT combined with oxy-fuel combustion CO2 capture technology; (3) dry recycle has a considerably higher electrical efficiency comparing with wet recycle, but more cooled water can be saved in the wet recycle. The performance of EvGT cycle was also compared to the combined cycle (CC) when CO2 capture was considered. The comparison shows that CC has a higher net power output and electrical efficiency than the EvGT cycle no matter if combined with oxy-fuel combustion CO2 capture technology or not.
Oxy-coal combustion has different flue gas composition from the conventional air-coal combustion. The different composition further results in different properties, such as the absorption coefficient, emissivity, and density, which can directly affect the heat transfer in both radiation and convection zones of utility boilers. This paper numerically studied a utility boiler of oxy-coal combustion and compares with air-coal combustion in terms of flame profile and heat transferred through boiler side walls in order to understand the effects of different operating conditions on oxy-coal boiler retrofitting and design. Based on the results, it was found that around 33vol% of effective O2 concentration ([O2]effective) the highest flame temperature and total heat transferred through boiler side walls in the oxy-coal combustion case match to those in the air-coal combustion case most; therefore, the 33vol% of [O2]effective could result in the minimal change for the oxy-coal combustion retrofitting of the existing boiler. In addition, the increase of the moisture content in the flue gas has little impact on the flame temperature, but results in a higher surface incident radiation on boiler side walls. The area of heat exchangers in the boiler was also investigated regarding retrofitting. If boiler operates under a higher [O2]effective, to rebalance the load of each heat exchanger in the boiler, the feed water temperature after economizer can be reduced or part of superheating surfaces can be moved into the radiation zone to replace part of the evaporators
Introducing CO2 capture and storage (CCS) into the power systems requires the re-investigation of the load balance for the electrical grid. For the oxy-coal combustion capture technology, the energy use of ASU can be shifted between the peak-load and off-peak-load periods, which may bring more benefits. In this paper, peak and off-peak (POP) operations for the air separation unit (ASU) with liquid oxygen storage were studied based on a 530MW coal-fired power system. According to the simulation results, the oxy-coal combustion power system running POP is technically feasible that it can provide a base load of 496MW during the off-peak period and a peak load of 613MW during the peak period. And the equivalent efficiency of the power system running POP is only 0.3% lower than the one not running POP. Moreover, according to the economic assessments based on the net present value, it is also economically feasible that the payback time of the investment of the oxy-coal combustion power system running POP is about 13years under the assumptions of 10% discount rate and 2.5% cost escalation rate. In addition, the effects of the difference of on-grid electricity prices, daily peak period, investment for POP operations, and ASU energy consumption were also analyzed, concerning the net present value.
Traditional energy storage systems have a common feature: the generating of secondary energy (e.g. electricity) and regenerating of stored energy (e.g. gravitational potential, and mechanical energy) are separate rather than deeply integrated. Such systems have to tolerate the energy loss caused by the second conversion from primary energy to secondary energy. This paper is concerned with the system dynamics of oxyfuel power plants with liquid oxygen energy storage, which integrates the generation of secondary energy (electricity) and regeneration of stored energy into one process and therefore avoids the energy loss caused by the independent process of regeneration of stored energy. The liquid oxygen storage and the power load of the air separation unit are self-adaptively controlled based on current-day power demand, day-ahead electricity price and real-time oxygen storage information. Such an oxyfuel power plant cannot only bid in the day-ahead market with base load power but also has potential to provide peak load power through reducing the load of the air separation unit in peak time. By introducing reasoning rules with fuzzy control, the oxygen storage system has potential to be further extended by integrating renewable energy resources into the system to create a cryogenic energy storage hub.
Oxy-fuel combustion is one of potential technologies for carbon dioxide (CO2) capture in fossil fuel fired power plants. Characterization of flue gas composition in the oxy-fuel combustion differs from that of conventional air-coal combustion, which results in the change of radiative heat transfer in combustion processes. This paper presents a numerical study of radiation intensity on lateral walls based on the experimental results of a 0.5MW combustion test facility (CTF). Differences in the oxy-coal combustion are analyzed, such as flue gas recycle, absorption coefficient and radiation intensity. The simulation results show that an effective O2 concentration ([O2]effective) between 29 and 33vol% (equivalent to the flue gas recycle ratio of 72-69%) constitutes a reasonable range, within this range the behavior of oxy-coal combustion is similar to air-coal combustion. Compared with the air-coal combustion, the lower limit (29vol%) of this range results in a similar radiative heat flux at the region closed to the burner, but a lower radiative heat flux in the downstream region of the CTF; the upper limit (33vol%) of this range results in a higher radiative heat flux at the region closed to the burner, while a similar radiative heat flux in the downstream region of the CTF
This paper studied the integration of Evaporative Gas Turbine (EvGT) cycle with oxy-fuel combustion for CO2 capture. The impact of key parameters on system electrical efficiency, such as the oxygen purity, Water/Gas ratio (W/G) has been investigated concerning thermal efficiency. The performance of dry recycle and wet recycle also has be analyzed and compared. Simulation results shows that: (1) 97% can be considered as the optimum oxygen purity taking into account the trade-off between the air separation unit (ASU) consumption penalty of producing higher-purity oxygen and electrical efficiency; (2) there" exists an optimum point of W/G for both EvGT and EvGT combined with oxy-fuel combustion CO2 capture technology; (3) dry recycle has a" considerably higher electrical efficiency comparing with wet recycle, but more cooled water can be saved in the wet recycle. The performance of EvGT cycle was also compared to the combined cycle (CC) when CO2 capture was considered. The comparison shows that CC has a higher net power output and electrical efficiency than the EvGT cycle no matter if combined with oxy-fuel combustion CO2 capture technology or not.
Oxy-coal combustion has different flue gas composition from the conventional air-coal combustion. The different composition further results in different properties, such as the absorption coefficient, emissivity, and density, which can directly affect the heat transfer in both radiation and convection zones of utility boilers. This paper numerically studied a utility boiler of oxy-coal combustion and compares with air-coal combustion in terms of flame profile and heat transferred through boiler side walls in order to understand the effects of different operating conditions on oxy-coal boiler retrofitting and design. Based on the results, it was found that around 33 vol% of effective O-2 concentration ([O-2](effective)) the highest flame temperature and total heat transferred through boiler side walls in the oxy-coal combustion case match to those in the air-coal combustion case most; therefore, the 33 vol% of [O-2](effective) could result in the minimal change for the oxy-coal combustion retrofitting of the existing boiler. In addition, the increase of the moisture content in the flue gas has little impact on the flame temperature, but results in a higher surface incident radiation on boiler side walls. The area of heat exchangers in the boiler was also investigated regarding retrofitting. If boiler operates under a higher [O-2](effective), to rebalance the load of each heat exchanger in the boiler, the feed water temperature after economizer can be reduced or part of superheating surfaces can be moved into the radiation zone to replace part of the evaporators.
The techno-economic evaluation of the evaporative gas turbine (EvGT) cycle with two different CO(2) capture options has been carried out. Three studied systems include a reference system: the EvGT system without CO(2) capture (System I), the EvGT system with chemical absorption capture (System II), and the EvGT system with oxyfuel combustion capture (System III). The cycle simulation results show that the system with chemical absorption has a higher electrical efficiency (41.6% of NG LHV) and a lower efficiency penalty caused by CO(2) capture (10.5% of NG LHV) compared with the system with oxyfuel combustion capture. Based on a gas turbine of 13.78 MW, the estimated costs of electricity are 46.1 $/MW h for System I. while 70.1 $/MW h and 74.1 $/MW h for Systems II and III, respectively. It shows that the cost of electricity increment of chemical absorption is 8.7% points lower than that of the option of oxyfuel combustion. In addition, the cost of CO(2) avoidance of System II which is 71.8 $/tonne CO(2) is also lower than that of System III, which is 73.2 $/tonne CO(2). The impacts of plant size have been analyzed as well. Results show that cost of CO(2) avoidance of System III may be less than that of System II when a plant size is larger than 60 MW.
The techno-economic evaluation of the evaporative gas turbine (EvGT) cycle with two different CO2 capture options has been carried out. Three studied systems include a reference system: the EvGT system without CO2 capture (System I), the EvGT system with chemical absorption capture (System II), and the EvGT system with oxyfuel combustion capture (System III). The cycle simulation results show that the system with chemical absorption has a higher electrical efficiency (41.6% of NG LHV) and a lower efficiency penalty caused by CO2 capture (10.5% of NG LHV) compared with the system with oxyfuel combustion capture. Based on a gas turbine of 13.78 MW, the estimated costs of electricity are 46.1 $/MW h for System I, while 70.1 $/MW h and 74.1 $/MW h for Systems II and III, respectively. It shows that the cost of electricity increment of chemical absorption is 8.7% points lower than that of the option of oxyfuel combustion. In addition, the cost of CO2 avoidance of System II which is 71.8 $/tonne CO2 is also lower than that of System III, which is 73.2 $/tonne CO2. The impacts of plant size have been analyzed as well. Results show that cost of CO2 avoidance of System III may be less than that of System II when a plant size is larger than 60 MW.
Introducing CO2 capture and storage (CCS) into the power systems requires the re-investigation of the load balance for the electrical grid. For the oxy-coal combustion capture technology, the energy use of ASU can be shifted between the peak-load and off-peak-load periods, which may bring more benefits. In this paper, peak and off-peak (POP) operations for the air separation unit (ASU) with liquid oxygen storage were studied based on a 530 MW coal-fired power system. According to the simulation results, the oxy-coal combustion power system running POP is technically feasible that it can provide a base load of 496 MW during the off-peak period and a peak load of 613 MW during the peak period. And the equivalent efficiency of the power system running POP is only 0.3% lower than the one not running POP. Moreover, according to the economic assessments based on the net present value, it is also economically feasible that the payback time of the investment of the oxy-coal combustion power system running POP is about 13 years under the assumptions of 10% discount rate and 2.5% cost escalation rate. In addition, the effects of the difference of on-grid electricity prices, daily peak period, investment for POP operations, and ASU energy consumption were also analyzed, concerning the net present value.
Oxy-coal combustion is one of the technical solutions for mitigating CO2 in thermal power plants. For designing a technically viable and economically effective CO2 capture process, effects by coals and configurations of flue gas cleaning steps are of importance. In this paper, characterization of the flue gas recycle (FGR) is conducted for an oxy-coal combustion process. Different configurations of FGR as well as cleaning units including electrostatic precipitators (ESP), flue gas desulfurization (FGD), selective catalytic reduction (SCR) deNOx and flue gas condensation (FGC) are studied for the oxy-coal combustion process. In addition, other important parameters such as FGR rate and FGR ratio, flue gas compositions, and load of flue gas cleaning units are analyzed based on coal properties and plant operational conditions.
Oxy-fuel combustion is one of potential technologies for carbon dioxide (CO2) capture in fossil fuel fired power plants. Characterization of flue gas composition in the oxy-fuel combustion differs from that of conventional air-coal combustion, which results in the change of radiative heat transfer in combustion processes. This paper presents a numerical study of radiation intensity on lateral walls based on the experimental results of a 0.5MW combustion test facility (CTF). Differences in the oxy-coal combustion are analyzed, such as flue gas recycle, absorption coefficient and radiation intensity. The simulation results show that an effective O2 concentration ([O2]effective) between 29 and 33vol% (equivalent to the flue gas recycle ratio of 72-69%) constitutes a reasonable range, within this range the behavior of oxy-coal combustion is similar to air-coal combustion. Compared with the air-coal combustion, the lower limit (29vol%) of this range results in a similar radiative heat flux at the region closed to the burner, but a lower radiative heat flux in the downstream region of the CTF; the upper limit (33vol%) of this range results in a higher radiative heat flux at the region closed to the burner, while a similar radiative heat flux in the downstream region of the CTF.
This paper examined and assessed various configuration options about emission removal including particles, SO x and NO x in an oxy-coal combustion system for CO 2 capture. A performance analysis was conducted in order to understand the impacts of those options concerning process design, process operation and system efficiency. Results show that different flue gas recycle options have clear effects on the emissivity and absorptivity of radiating gases in boiler due to the change of flue gas compositions. The maximum difference amongst various options can be up to 15% and 20% for emissivity and absorptivity respectively. As a result, the heat transfer by radiation can vary about 20%. The recycle options also have impacts on the design of air heater and selective-catalytic-reduction (SCR) preheater. This is due to that the largely varied operating temperatures in different options may result in different required areas of heat exchangers. In addition, the dew point of flue gas and the boiler efficiency are affected by the configurations of flue gas recycle as well.
This paper examined and assessed various configuration options about emission removal including particles. SOx and NOx in an oxy-coal combustion system for CO2 capture. A performance analysis was conducted in order to understand the impacts of those options concerning process design, process operation and system efficiency. Results show that different flue gas recycle options have clear effects on the emissivity and absorptivity of radiating gases in boiler due to the change of flue gas compositions. The maximum difference amongst various options can be up to 15% and 20% for emissivity and absorptivity respectively. As a result, the heat transfer by radiation can vary about 20%. The recycle options also have impacts on the design of air heater and selective-catalytic-reduction (SCR) preheater. This is due to that the largely varied operating temperatures in different options may result in different required areas of heat exchangers. In addition, the dew point of flue gas and the boiler efficiency are affected by the configurations of flue gas recycle as well.
The water-energy nexus has been introduced into urban water supply systems (WSSs) to improve the current plight of scarce resources and greenhouse effect in recent years. Urban water-energy integrated management is limited by the characteristics and reality of each city. In this paper, we characterize the comprehensive influence factors of energy use in China urban WSSs including geographic differences and city forms. The results indicate that the pressure of pipeline network and plain area ratio restricted by geomorphology would significantly impact the energy consumption during conveyance and distribution stage. For the city form aspect, the total volume of urban water supply and the leakage rate of pipeline networks play important roles in energy consumption of urban WSSs in China. In this study, the specific electricity consumption in WSSs was quantified, and several factors affected by city features which show strong correlation with energy use were determined. The results are of great significance to the energy saving in water supply systems in urban areas.
To combine the abilities of lipids extraction and CO2 capture by algae + IL system, chlorella hydrolysis integrating CO2 removal by ILs ([bmim][BF4], [bmim]Cl and [amim]Cl) to extract lipids energy-efficiently was demonstrated in this study. The addition of CO2 to [bmim][BF4] can increase the lipids yield from 14.2% to 15.6%. The value of net energy gain increased from 10.4 to 35.9 with the CO2 addition to [bmim][BF4] because of the compensated CO2 capture energy in the algae extraction process.
As climate issues gradually attract public attention worldwide, the operation and construction of oil product pipelines have been attached with new energy-saving and emission-reduction targets. Though previous studies concerning Life Cycle Assessment of oil and gas pipelines have estimated the carbon footprint to some extent, there is a lack of researches that take the characteristics of oil products pipelines into consideration. Oil products pipelines undertake the task of delivering various products to downstream demand locations, which differs greatly from other pipeline transportation systems as back-to-back sequential delivery is adopted. In this paper, a detailed Life Cycle Assessment model is established to analyze carbon emissions of oil products pipeline system from construction to disposal as well as its impact on soil environment. Data from practical pipes is adopted as the case study to reflect emissions produced in different stages, and the amount of total and unified emissions of different pipes provided through the proposed model is within the range of 2.78 to 4.70 tCO2e/t·km. Then, sensitivity analysis is carried out to identify the driving factors of emissions. According to the calculation results, pipe length, diameter and throughput turn out to be the dominating factors, and an empirical formula is derived for future planned pipes. Relevant recommendations are put forward based on the results to help reduce emissions from oil product pipe transportation.