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Abstract For biomass/waste fueled power plants, stricter regulations require a further reduction of the negative impacts on the environment caused by the release of pollutants and withdrawal of fresh water externally. Flue gas quench (FGQ) is playing an important role in biomass or waste fueled combined heat and power (CHP) plants, as it can link the flue gas (FG) cleaning, energy recovery and wastewater treatment. Enhancing water evaporation can benefit the concentrating of pollutant in the quench water; however, when FG condenser (FGC) is not in use, it results in a large consumption of fresh water. In order to deeply understand the operation of FGQ, a mathematic model was developed and validated against the measurements. Based on simulation results key parameters affecting FGQ have been identified, such as the flow rate and temperature of recycling water and the moisture content of FG. A guideline about how to reduce the discharge of wastewater to the external and the withdrawal of external water can be proposed. The mathematic model was also implemented into an ASPEN Plus model about a CHP plant to assess the impacts of FGQ on CHP. Results show that when the FGC was running, increasing the flow rate and decreasing the temperature of recycling water can result in a lower total energy efficiency.

Abstract Variable electricity generation from wind and solar influences the design of a cost-efficient and reliable energy system. This paper presents a method that uses stochastic programming to represent variable renewable electricity generation in long-term energy system models, and demonstrates this on a Norwegian TIMES model. First, we derive hourly PV- and wind-generation data by modifying satellite-based data, based on a comparison with historical generation data. Second, the satellite-based dataset is transformed into a manageable set of scenarios that is used as an input to the stochastic energy-system model. This is done using six different scenario generation methods. Third, we solve the energy-system model with three of the scenario-generation methods and evaluate the quality of the corresponding model value by stability tests. We demonstrate that scenarios generated from the six methods have significantly different moment-based and Wasserstein distance error relative to the dataset. Further, the energy system model results show that the number of scenarios needed to achieve stability differs between the three used scenario generation methods.

Time-use data, describing in detail the everyday life of household members as high-resolved activity sequences, have a largely unrealized potential of contributing to domestic energy demand modelli ...

Over the past three decades, Swedish energy policy has evolved in three major stages—oil reduction, phase-out of nuclear energy, renewable energy—each with a different focus. Since 1977, Swedish law has required municipalities to develop an energy plan that addresses the supply, distribution, and use of energy. Whether such plans have contributed to the development of local energy-systems has been a subject for debate. This paper is based on a study of 12 municipal energy-plans that attempted to control and develop local energy-systems in southern Sweden. The analysis examines how municipalities promote oil reduction, efficient energy use, and the use of renewable energy. The plans varied in planning processes, contents, and level of ambition. The results of the study show that the contents of the plans follow the national energy-policies with respect to reduction of oil use, improved energy efficiency, and increased use of renewable energy.

The reactivity and attrition resistance of Mn–Fe oxygen carriers with addition of Al2O3 as support have been investigated. Spray-dried oxygen-carrier particles with Mn:Fe molar ratios of 80:20 and 33:67 were prepared using different amounts of Al2O3. Each material was calcined for 4 h at 950 °C, 1100 °C or 1200 °C. The oxygen carriers were studied in a batch fluidized bed reactor to investigate their reactivity with wood char, CH4, syngas and also their oxygen release in N2. In order to measure the mechanical stability of the different materials, the attrition resistance was measured in a jet-cup apparatus. Addition of Al2O3 to materials with a Mn:Fe molar ratio of 80:20 was not advantageous. Generally oxidation of these materials was problematic. The Al2O3 supported materials with a Mn:Fe molar ratio of 80:20 calcined at 950 °C and 1100 °C showed poor attrition resistance and were highly fragmented or turned to dust, whereas those calcined at 1200 °C showed high attrition resistance but poor gas conversion.Materials with a Mn:Fe molar ratio of 33:67 supported with Al2O3 generally showed better attrition resistance. Also their oxidation with 5 vol% of oxygen was possible at temperatures higher than 850 °C. Furthermore, some of these materials showed good reactivity with methane, syngas and char. Low attrition, good reactivity and CLOU properties in combination with potentially low raw materials costs, make these materials interesting for CLC.

Abstract Directed relation graph with error propagation (DRGEP) method combined with extensive validation for 0D, 1D and 2D CFD modeling supported by sensitivity and Rate-Of-Production (ROP) analyses are implemented for comparative study of detailed and reduced kinetic mechanisms for CH4 + H2 combustion. To this end, two detailed kinetic mechanisms, namely AramcoMech 2.0 and recently updated Konnov mechanism, were validated using available measurements of ignition delay times and laminar burning velocities for hydrogen, methane and hydrogen + methane fuel mixtures. For all experimental conditions visited, both detailed mechanisms demonstrated good and close to each other performance. Two-stage DRGEP method and reaction reduction based on computational singular perturbation (CSP) were then implemented to achieve two skeletal models: 25 species and 105 reactions for AramcoMech 2.0 and 27 species and 107 reactions for the Konnov model. The conditions for skeletal models generation cover ɸ = 0.5–2.0, temperature 900–2000 K, and pressure 1–50 bar. Turbulent non-premixed flames of CH4 + H2 in the Jet in Hot Co-flow (JHC) burner for two different oxygen concentrations in a co-flow were modeled using both skeletal models. 2-D RANS simulations with OpenFOAM code of the flame structure using the two skeletal kinetic mechanisms are similar except for the mass fraction of OH and CO. To elucidate the differences between two skeletal mechanisms generated using the same reduction method, extensive validation for 0D, 1D and 2D CFD modeling were supported by sensitivity analysis for detailed and skeletal reaction models. Good agreement between the skeletal and detailed mechanisms was found in top reactions as well as their sensitivity coefficients, which affect auto-ignition process and laminar flame propagation. Further chemical and sensitivity analysis of the structure of laminar flames demonstrate that three important reactions, i.e. CO + OH = CO2 + H, H2 + OH = H + H2O, and CH4 + OH = CH3 + H2O have different rate constants in the Aramco and Konnov models that may contribute to the differences in the prediction of CO concentration profiles. The simulation predictions for CO concentrations are improved for laminar flames and JHC flame by using a 25-species modified version in which these rate constants were taken from the Konnov mechanism. It was noted that DRGEP method applied to different detailed kinetic schemes generate skeletal models with different, non-overlapping lists of retained species. The presence of CH2CHO in the Aramco 25-species skeletal mechanism and its absence in the Konnov 27-species mechanism, and the presence of CH, CH2, CH2CO in the latter and their absence in the former mechanism were analysed and explained using Rate-Of-Production analysis for conditions found in the CFD simulations.

Recent improvements in low-temperature heat-to-power (LTHtP) technologies have led to an increase in efficiency at lower temperatures and lower cost. LTHtP has so far not been used in district heat ...

Abstract Novel interfacial microwave heating of a layered structure has been applied to the process of low-temperature annealing of titania mesoporous films for dye-sensitized solar cells. Interfacial microwave annealing dramatically enhances the cell performances as compared with conventional heating in an electric oven. The improvement of cell performance is attributed to the electron transport properties in the titania films annealed by MW resulting in longer diffusion length as compared with conventional heating.

This paper is a contribution to the discussion on the relation between thermodynamics and economic theory. With respect to thermodynamic constraints on the economy, there are two diametrically opposite positions in this discussion. One claims that the constraints are insignificant (‘of no immediate practical importance for modelling’) and in the intermediate run, do not limit economic activity and, therefore, need not be incorporated in the economic theory. The other holds that thermodynamics tells us that there are practical limits to materials recycling, which already puts bounds on the economy and, therefore, must be included in the economic models. Using the thermodynamic concept of entropy, we show here that there are fundamental problems with both positions. Even in the long run, entropy production associated with material dissipation need not be a limiting factor for economic development. Abundant energy resources from solar radiation may be used to recover dissipated elements. With simple, quantitative analysis we show that the rate of entropy production caused by human economic activities is very small compared to the continuous natural entropy production in the atmosphere and on the Earth’s surface. Further, the societal entropy production is well within the range of natural variation. It is possible to replace part of the natural entropy production with societal entropy production by making use of solar energy. Society consumes resources otherwise available for coming generations. However, future generations need not have less resources available to them than the present generation. Human industrial activities could be transformed into a sustainable system where the more abundant elements are industrially used and recycled, using solar energy as the driving resource. An economic theory, fit to guide industrial society in that development, must not disregard thermodynamics nor must it overstate the consequences of the laws of thermodynamics. © 2001 Elsevier Science B.V. All rights reserved.