Supply assessment of forest biomass – A bottom-up approach for Sweden

As there is increasing interest in the use of biomass for energy in Sweden, the potential availability and harvesting costs of forest roundwood, harvesting residues and stumps were estimated up to the year 2069 in 10-year intervals, using a high spatial resolution GIS. In each individual forest area, an average harvesting cost per forest assortment was estimated, based on the geographic and other properties of the area. Using cost structure and resource availability, marginal cost curves were constructed to allow analyses of the effects of changing market conditions and different policy frameworks. Based on geographically explicit data, the results indicated that the average harvesting costs would be 21–24 € m⁻³ for roundwood, depending on the type of harvesting and extraction operation. The corresponding cost estimate for harvesting residues was 23–25 € m⁻³ and 35 € m⁻³ for stumps. The harvesting cost estimates lie on the steeper part of the marginal cost curve, suggesting that increases in the supply of woody biomass can only occur at significantly higher harvesting costs. From a policy perspective, this suggests that subsidies aimed at reducing the harvesting costs will only have limited success in increasing the harvested volumes, given current technology. Therefore, for future development in the supply of forest assortments for energy generation, it is important to consider not only the supply potential, but also the integration of improvements in harvesting and transportation systems.     

Furnace for biomass combustion – Comparison of model with experimental data

As one of the most easily accessible renewable energy resources, straw can be burned to provide heat energy. In this paper, results of theoretical and experimental research conducted under the proceedings of mathematical – numerical modeling of turbulent reacting flows has been presented. Two-dimensional turbulent flow model with homogeneous chemical reactions has been developed. The proposed model has been analyzed on the example of adiabatic combustion chamber for combustion of agricultural biomass. Turbulent flow is considered using time averaging Navier–Stokes equations that are closed by k–ε turbulence model. Calculations based on the proposed models were conducted using commercial CFD package FLUENT 6.3.26. For the purposes of experimental research, measurements of fluid flow and thermal parameters, such as continuous measurement of temperature in different points in the workspace furnace, air flow, flue gas flow, continual analysis of combustion products as well as setting heat and material balance, were carried out. Comparative analysis of the results of experiments and calculations indicate satisfactory agreement between the model and experiment.     

A numerical study of pulverized coal ignition by means of plasma torches in air–coal dust mixture ducts of utility boiler furnaces

Paper presents selected results of numerical simulation of processes in air–coal dust mixture duct of pulverized coal utility boiler furnace with plasma-system for pulverized coal ignition and combustion stabilization. Application of the system in utility boiler furnaces promises to achieve important savings compared with the use of heavy oil burners. Plasma torches are built in air–coal dust mixture ducts between coal mills and burners. Calculations have been performed for one of rectangular air–coal dust mixture ducts with two opposite plasma torches, used in 210 MW_e utility boiler firing pulverized Serbian lignite. The simulations are based on a three-dimensional mathematical model of mass, momentum and heat transfer in reacting turbulent gas-particle flow, specially developed for the purpose. Characteristics of processes in the duct are analyzed in the paper, with respect to the numerical results. The plasma-system thermal effect is discussed as well, regarding corresponding savings of liquid fuel. It has been emphasized that numerical simulation of the processes can be applied in optimization of pulverized coal ignition and combustion stabilization and enables efficient and cost-effective scaling-up procedure from laboratory to industrial scale.     

Steam co-gasification of coal and biomass – Synergy in reactivity of fuel blends chars

Development of clean coal technologies is the answer to increasing energy demand and environmental concerns related to conventional coal processing technologies. The technologies of fossil fuel gasification are technically proven and commercially available. Attempts of utilization of waste materials and renewable energy resources in gasification-based energy generation systems has been made, but wide application of such systems is still hindered by issues inherently combined with the characteristics of the materials. These include discontinuous supplies of a fuel of limited resources and varying composition resulting in poor economy of small-scale systems and operating problems related to tars formation and corrosion, especially when biomass utilization is considered. In the light of the above co-gasification seems to offer several advantages through mitigation of undesired effects of both carbon-intensive utilization of coal and low efficient and troublesome operation of biomass/waste-fed gasification systems. The experimental results presented in the paper address the issues of determination of potential synergy effects resulting from the utilization of fuel blends composed of materials of various physical and chemical characteristics, which are still insufficiently discussed in the literature, especially when hydrogen-rich gas production in co-gasification is concerned. The results of reactivity tests of fuel blends of coal and energy crops biomass in the process of steam co-gasification in a laboratory scale fixed bed reactor at 700, 800 and 900 °C are given proving the synergy effect in co-gasification reflected in increased reactivity of fuel blends when compared to coal and biomass chars reactivity under similar process conditions.     

Acceptance of biomass plants – Results of a longitudinal study in the bioenergy-region Altmark

The present contribution addresses the results of a longitudinal study in a ‘bioenergy-region’ concerning the public acceptance of biomass plants and the corresponding influencing factors. Using a standardized questionnaire, 423 persons were polled between 2009 and 2011 on three points of measurement in four places in the bioenergy-region Altmark. One main result of the study is that the reported public acceptance remains constantly high over time; nevertheless it became evident that the respective influencing factors differ in their strength, whereas the perceived regional benefit shows a strong connection to the reported public acceptance of biomass plants at each point of measurement. Concluding the research results, the acceptance of biomass plants doesn't seem to be a fixed construct, but has to be seen in context of the respective experiences with plants on a local level over time.In addition to the local population, key actors of the regional biomass sector were also interviewed (N = 26). The analyses show significant differences in the perception and evaluation of the current informational level between the population and the key actors. Furthermore, the key actors estimated the utilisation of biomass even more positively and expected a greater ‘signal function’ of the bioenergy-region-project compared to the population.     

Investment screening model for spatial deployment of power-to-gas plants on a national scale – A Danish case

When transitioning to a 100% renewable energy system storing electricity becomes a focal point, as the resource flexibility is lost and the design of the energy system needs to provide flexibility and balancing options to integrate intermittent renewable resources. Using technologies such as power-to-gas offers an opportunity to store electricity in chemical form, which can be used as a long-term storage option. This paper develops a spatial modelling method by using a GIS tool to investigate potential generation sites for power-to-gas plants. The method determines the location of the plants by carbon source potential, proximity of the grid, costs of grid transmission and investment costs of the technology itself. By combining these types of data, it is possible to identify the investment costs of the power-to-gas plants. The method focuses on two paths: biogas upgrade and CO₂ methanation. The method is applied to a specific case by investigating the power-to-gas potential in Denmark. The potential and spatial deployment is found by examining the investment costs of plants with an annual gas production of 60 GWh. The findings of the analysis indicate that the biogas upgrade path is the cheapest one of the two, at the present cost level, but due to the relatively small number of biogas plants in Denmark, the chosen plant size is limited to around 55 plants. CO₂ methanation is a more costly path, but it has a larger potential of around 800 plants. As the analysis is based on the current sources for biogas and CO₂, it is important to emphasise that the potential for CO₂ methanation plants can be expected to diminish in the future as more renewable energy is introduced, lowering the need for thermal energy producers, while biogas production could see an increase. Nevertheless, the analysis of a specific case shows that the method gives a good indication of the extent of the power-to-gas resources by using a novel approach to the matter. The method can be applied in other countries as well, giving it a wide appeal.     

Generation of skeletal and reduced reaction mechanisms for bio-derived syngas generated from biomass gasification – Experimental and numerical approach

Skeletal and reduced reaction mechanisms replicate the behavior of full reaction mechanism within the band/regime of optimization criteria and provide specific computational advantages for resource-intense multi-physics domain analysis. The current work reports on the development of skeletal and reduced mechanisms for bio-derived Producer gas and Hydrogen-rich Syngas by using GRI Mech 3.0 mechanism. The mechanisms are generated adopting graph-based approach, and timescale analysis are validated for laminar flame speed based on experiments in the equivalence ratios regime of 0.6–1.6 adopting a flame tube apparatus built in-house to mimic a freely propagating double infinity domain premixed reactor. Extending the analysis, the reduced/skeletal mechanisms are numerically validated for ignition delay time, major species profile, and volumetric heat release rate with validity established within the 5% tolerance limit. The current work is a first of its kind to propose optimized mechanism for compositions typical of bio-derived Producer gas and Syngas.     

Does a large coal particle in a hot fluidised bed lose its volatile content according to the shrinking core model?

Near-spherical particles (diameter ∼14 mm) of six different coals (ranging in rank from an anthracite to a lignite) were immersed in turn in an electrically heated bed of sand fluidised by nitrogen. Such a bubbling fluidised bed (U/Umf=3.0) was held at a fixed temperature between 750 and 950 °C. A coal particle in such a situation decomposes in the overall reaction:

coal→volatile matter+char,     

Analysis of the potential production and the development of bioenergy in the province of Mendoza – Bio-fuels and biomass – Using geographic information systems

In this work, the partial results of the potential production of energy, starting from the biomass and the development of the crops, directed to the production of bio-fuels (Colza and Topinamur) in the North irrigation oasis of Mendoza, Argentina within the National Program of Bio-energy developed by INTA is presented.     

Statistical phonon transport model for multiscale simulation of thermal transport in silicon: Part I – Presentation of the model

The Boltzmann transport equation can be used to model phonon transport in crystalline materials across multiple length scales. The statistical phonon transport model solves the Boltzmann transport equation in a statistical framework that incorporates a state-based phonon transport methodology. The statistical phonon transport model captures the anisotropy of the first Brillouin zone in addition to nonlinear dispersion. Three-phonon scattering is implemented conserving both energy and pseudo-momentum with probability limits based exclusively on the relative phonon populations available.     

Effects of economies of scale and experience on the costs of energy-efficient technologies – case study of electric motors in Germany

Increasing energy efficiency is discussed as an effective way to protect the climate, even though this is frequently associated with additional (investment) costs when compared to standard technologies. However, the investment costs of emerging energy-efficient technologies can be reduced by economies of scale and experience curve effects. This also brings about higher market penetration by lowering market barriers. Experience curves have already been analyzed in detail for renewable energy technologies, but are not as well documented for energy-efficient technologies despite their significance for energy and climate policy decisions. This work provides empirical evidence for effects of economies of scale and experience on the costs of energy-efficient electric motors. We apply a new methodology to the estimation of learning effects that is particularly promising for energy-efficient technologies where the very low data availability did not allow calculations of learning rates so far. Energy-efficient electric motors are a highly relevant energy technology that is responsible for about 55% of German electricity consumption. The analysis consists of three main steps. First, the calculation of composite price indices based on gross value added statistics for Germany which show the changes in cost components of electric motors over the period 1995 to 2006; second, an estimation of the corresponding learning rate which is, in a third step, compared with learning rates observed for other energy-efficient technologies in a literature review. Due to restrictions of data availability, it was not possible to calculate a learning rate for the differential costs of energy-efficient motors compared to standard motors. Still, we estimated a learning rate of 9% for “Eff2” motors in a period when they penetrated the market and replaced the less efficient “Eff3” motors. Furthermore, we showed the contribution of different effects to these cost reductions, like a reduction of material use per motor produced by 15% and an improvement of labor productivity of 43%.     

Multi-scale complexities of solid acid catalysts in the catalytic fast pyrolysis of biomass for bio-oil production – A review

Despite remarkable progress in catalytic fast pyrolysis, bio-oil production is far from commercialization because of multi-scale challenges, and major constraints lie with catalysts. This review aims to introduce major constraints of acid catalysts and simultaneously to find out possible solutions for the production of fuel-grade bio-oil in biomass catalytic fast pyrolysis. The catalytic activities of several materials which act as acid catalysts and the impacts of Bronsted and Lewis acid site on the formation of aromatic hydrocarbons are discussed. Considering the complexity of catalytic fast pyrolysis of biomass with acid catalysts, in-depth understandings of cracking, deoxygenation, carbon-carbon coupling, and aromatization for both in-situ and ex-situ configurations are emphasized. The limitation of diffusion along with coke formation, active site poisoning, thermal/hydrothermal deactivation, sintering, and low aromatics in bio-oil are process complexities with solid acid catalysts. The economic viability of large-scale bio-oil production demands progress in catalyst modification or/and developing new catalysts. The potential of different catalyst modification strategies for an adequate amount of acid sites and pore size confinement is discussed. By critically evaluating the challenges and potential of catalyst modification techniques, multi-functional catalysts may be an effective approach for selective conversion of biomass to bio-oil and chemicals through catalytic fast pyrolysis. This review offers a scientific reference for the research and development of catalytic fast pyrolysis of biomass.     

How does market power affect the impact of large scale wind investment in 'energy only' wholesale electricity markets?

In the short run, it is well known that increasing wind penetration is likely to reduce spot market electricity prices due to the merit order effect. The long run effect is less clear because there will be a change in new capacity investment in response to the wind penetration. In this paper we examine the interaction between capacity investment, wind penetration and market power by first using a least-cost generation expansion model to simulate capacity investment with increasing amounts of wind generation, and then using a computer agent-based model to predict electricity prices in the presence of market power. We find the degree to which firms are able to exercise market power depends critically on the ratio of capacity to peak demand. For our preferred long run generation scenario we show market power increases for some periods as wind penetration increases however the merit order counteracts this with the results that prices overall remain flat. Returns to peakers increase significantly as wind penetration increases. The market power in turn leads to inefficient dispatch which is exacerbated with large amounts of wind generation.     

Microencapsulation of phase change material in water dispersible polymeric particles for thermoregulating rubber composites—A holistic approach

Summary To avoid the leakage of phase change materials (PCM) to its surrounding, microencapsulation of PCM in a polymeric shell is highly desirable. These microcapsules ideally should provide a platform to store and release latent heat of the PCM without undergoing any physicochemical transformation of core (PCM) as well as shell (polymer) materials. Several characteristics such as heat transfer efficiency, thermal conductivity, water dispersibility, and durability of the PCM capsules are dependent on the nature of shell materials. In the present study, a random copolymer of poly (methyl methcrylate-co-2-hydroxyethyl methacrylate) poly (MMA-co-HEMA) with an optimum ratio of 75/25 (methyl methacrylate (MMA)/2-hydroxyethyl methacrylate (HEMA)) was used as shell material to encapsulate paraffin wax (PCM), using emulsion solvent evaporation method. The microcapsules of ~5-μm size with a shell thickness of ~0.8 μm with high encapsulation efficiency (~92.34%) and thermal storage capability (99.85%) were fabricated. In addition to ease of water dispersibility, PHEMA (poly(2-hydroxyethyl methacrylate)) containing water absorbable shells also exhibit enhanced thermal conductivity from 0.1 to 0.49 W/(m·K) at 25°C in wet state compared with the dry capsule. The capsules show good durability by displaying no significant change in thermal properties and water dispersibility after running through 500 heating/cooling cycles. To test the feasibility of this novel water dispersible microencapsulated PCM, these were mixed with natural rubber latex at various blend ratios, and their thermal behaviour was evaluated. The obtained rubber composite showed good thermoregulation property with enhanced mechanical strength.     

Urban lignocellulosic biomass can significantly contribute to energy production in municipal wastewater treatment plants – A GIS-based approach for a metropolitan area

The common fermentation of biogenic wastes and sewage sludge in digesters of municipal wastewater treatment plants is a technically feasible and economically viable approach. As the number of rural biogas production sites is steadily increasing, the question has been raised which biomass feedstocks are left available in sufficient quantities to be used for energy generation at wastewater treatment plant level. The contribution of lignocellulosic biomass collected from urban areas is generally neglected within this context. In the present study, 24 urban substrates have been analyzed for their theoretical methane potential, while 13 of them were tested in batch assays for the determination of their practical achievable methane yield. The theoretical evaluation of the methane potential yielded values ranging between 0.393 and 0.576 Nm³ kgVS⁻¹. The methane yields obtained by batch assays showed significantly lower yields, which depends on the individual composition of the substrates in terms of lignin, hemicellulose and cellulose. A GIS spatial analysis for the Rhine-Ruhr metropolitan area was performed to evaluate the feasible capacity of urban biomass as co-fermentation feedstock in digesters of municipal wastewater treatment plants. The analysis revealed that green urban areas provide a significant quantity of biomass of 377 t_FM d⁻¹ that could cover 67% of the annual energy demand of twelve typical wastewater treatment plants located in the metropolis.     

Coupling SOFCs to biomass gasification – The influence of phenol on cell degradation in simulated bio-syngas. Part II – Post-test analysis

Anode-supported solid oxide fuel cells (SOFCs) with a state-of-the-art Ni/YSZ anode have been tested in simulated bio-syngas with controlled addition of phenol as a model molecule to study the influence of tars on the degradation of SOFCs operated with gasified biomass. The post-test analysis results of SOFCs are described after operation with different concentrations of phenol. The tests with pure syngas and up to 2 g/Nm³ of phenol show a relatively stable performance in a short-term period of 500 h, but the test with 8 g/Nm³ phenol shows drastic degradation. The microstructural changes of anode and support layers, phase changes, and carbon deposition were analyzed and discussed based on performance degradation and post-test analysis. No structural changes were found after tests with pure syngas. On the other hand, the addition of phenol causes macro- and micro-scale structural changes in the support, spreading from the fuel inlet. The support shows an erosion pattern and both Ni and YSZ were found as dust after the test. In these eroded areas, carbon fibers were observed by SEM and it was more pronounced with higher phenol content. There was no material phase transformation related to syngas or phenol, but surface carbon deposition was confirmed by Raman spectroscopy in the support and anode layers.     

Integrated drying and gasification of wet microalgae biomass to produce H2 rich syngas – A thermodynamic approach by considering in-situ energy supply

A novel integrated drying and gasification of microalgae wet biomass process, involving a chemical-looping combustion (CLC) option to supply energy, is developed using Aspen Plus. The integrated gasification system consists of four primary units, including (i) a wet biomass drying unit, (ii) the gasification system, (iii) the CLC section, and (iv) the gas purification process. The model shows a good accuracy (relative error < 10%) in predicting the product compositions as compared to the experimental results under consistent operating conditions. The performance of the integrated gasification system is evaluated using Spirulina microalgae at various moisture contents (0–45 wt%). The effect of gasifying agents O₂/steam and the fraction of the produced char used in the CLC section on the gasification performance is also evaluated. The tar is successfully reformed into syngas in the pyrolysis stage by adjusting the O₂ flow rate. The C (char) to CLC provides to a positive effect on the syngas composition, particularly for gasification of wet biomass, but brings an adverse impact on the yield of the syngas product. The integration of the CLC process and CO₂ absorber in the gasification system provides high-quality syngas by removing CO₂. The separated pure CO₂ can be used as a feedstock for other chemical industries.     

Availability,supply technology and costs of residual forest biomass for energy – A case study in northern China

In theory, China has vast potential forest resources for production of energy, but utilization on an industrial scale has been negligible. We assessed the practical possibilities and barriers for a forest energy business in a case study in northern China. The specific objectives of the study were 1) to assess the availability of forest biomass for energy production, 2) to determine feasible supply chains, and 3) to estimate the biomass fuel supply costs. Based on the case study results, the stand-level removals of the intended feedstock were low and the supply costs were relatively high. Suggestions for increasing the raw material basis, lowering the costs and further research and development were given. We conclude that although the case study area may not be promising from the feedstock point of view, the development could be started with small steps and proven technology. In order to avoid expensive mistakes further research for transfer of know-how and technology is needed.     

Impacts of nano-metal oxides on hydrogen production in anaerobic digestion of palm oil mill effluent – A novel approach

In the present study, hydrogen production from palm oil mill effluent (POME) was investigated with the incorporation of nanoparticles (NPs) comprising of nickel (NiO) and cobalt oxides (CoO). The NPs of NiO and CoO were prepared using hydrothermal method and were further applied to analyse, their effect on hydrogen production. The results demonstrated that, a maxima volumetric hydrogen production rate of 21 ml H₂/L-POME/h with the hydrogen yield of 0.563 L H₂/g-COD_removed was obtained with 1.5 mg/L concentration of NiO NPs. On the other hand, the addition of CoO NPs produced maximum volumetric hydrogen production rate of 18 ml H₂/L-POME/h with a hydrogen yield of 0.487 L H₂/g-COD_removed with 1.0 mg/L of CoO NPs. Results showed that addition of optimal concentration of NiO and CoO NPs to the POME enhances the hydrogen yield by 1.51 and 1.67 fold respectively. Besides, this addition of NiO and CoO enhanced the COD removal efficiency by 15 and 10% respectively as compared to an un-additive NPs POME. The toxicity of NPs was also tested using bacterial viability test, which revealed that application of 3.0 mg/L of NiO and CoO NPs to modified Luria-Bertani (LB) medium had 63% and 83% reduction in bacterial cell growth. The results concluded that supplementation of NiO and CoO NPs under an optimal range to the wastewater can improve the hydrogen productivity.