Sustainable energy system – A case study from Chile

This paper presents some of the results of a power system analysis for Chile. The two major Chilean electric systems are roughly modelled and optimized using a linear programming method with the option to integrate renewable energy sources like wind power, solar power, mini-hydropower and biomass-fired power and also “municipal waste”. A total of four different scenarios are outlined: reference system, new production units, gas and coal price variations and a policy measure to encourage power production based on renewable energy. The objective of the scenarios was to illustrate under what conditions integration of the different energy sources in the existing production system is possible. The study shows that even under current conditions, mini-hydro and waste to energy plants are economically viable. Wind power might be interesting alternatives if policy instrument measures are applied. On the other hand, it is hard for the other energy sources to enter the system even when higher price levels of gas and coal are applied. The system is more sensitive to coal price increases than to gas price increases and this mainly encourages CO₂ emission reduction.     

Modelling and optimization of district heating and industrial energy system—an approach to a locally deregulated heat market

Regions with densely concentration of industries and district heating systems (DHS) could be interesting study object from the light of an integrated heat market on local basis. System analysis with a widened system boundary could be used as an approach to evaluate the benefit of an integrated heat supply system. In this study, an energy system model consisting of totally seven different participants is designed and the optimization results of the system analysis are presented. With applied data and assumptions, the study shows that a significant amount of the heat demand within two sub‐systems can be covered by heat supply from the heat market (the entire heat comes from two industries). Shadow prices, which can be used for heat pricing, indicate the advantage of an integrated system. The system cost reduction through integration and the availability of several actors with diverse energy supply system, makes the region under study an interesting area to prove a locally deregulated heat market. Copyright © 2004 John Wiley & Sons, Ltd.     

The dynamics of urban expansion and land use/land cover changes using remote sensing and spatial metrics: the case of Mekelle City of northern Ethiopia

Information on the rate and pattern of urban expansion is required by urban planners to devise proper urban planning and management policy directions. This study evaluated the dynamics and spatial pattern of Mekelle City’s expansion in the past three decades (1984–2014). Multi-temporal Landsat images and Maximum Likelihood Classifier were used to produce decadal land use/land cover (LULC) maps. Changes in LULC and spatial pattern of urban expansion were analysed by post-classification change detection and spatial metrics, respectively. The results showed that in the periods 1984–1994, 1994–2004, and 2004–2014, the built-up area increased annually by 10%, 9%, and 8%, respectively; with an average annual increment of 19% (100 ha year^?1), from 531 ha in 1984 to 3524 ha in 2014. Between 1984 and 2014, about 88% of the gain in built-up area was from conversion of agricultural lands, which decreased by 39%. Extension of existing urban areas was the dominant growth type, which accounted for 54%, 75%, and 81% of the total new development during 1984–1994, 1994–2004, and 2004–2014, respectively. The spatial metrics analyses revealed urban sprawl, with increased heterogeneity and gradual dispersion in the outskirts of the city. The per capita land consumption rate (ha per person) increased from 0.009 in 1984 to 0.014 in 2014, indicating low density urban growth. Based on the prediction result, the current (2014) built-up area will double by 2035, and this is likely to have multiple socioeconomic and environmental consequences unless sustainable urban planning and development policies are devised.     

Preparation of polypropylene/high-melt-strength PP open-cell foam for oil absorption

Oil spills not only cause significant economic losses; they also harm the environment. In this study, high-melt-strength polypropylene (HMSPP) and linear polypropylene (PP) were compounded at different ratios and foamed by supercritical CO₂ at various temperatures and pressures to develop open-cell foams for oil absorption applications. The experimental results show that adding HMSPP increased the foam expansion ratio and the open-cell content and that the foam processing window widened with increasing HMSPP content. The oil absorption experiment results show that the amount of oil absorption increased with the foam expansion ratio and that low oil viscosity resulted in high oil absorption. In addition, the amount of oil absorption remained unchanged after 10 cycles of oil absorption experiments. The oil absorption kinetics study shows that the oil absorption process complied with the pseudo-second-order law.     

Employment,income, migration and public services: A simultaneous spatial panel data model of regional growth*

We estimate a regional spatial panel simultaneous‐equations growth model, using a five‐step new estimation strategy that generalizes an approach outlined in Kelejian and Prucha. The study region consists of the 418 Appalachian counties 1980?2000. Estimates show feedback simultaneities among the endogenous variables, conditional convergence with respect to the respective endogenous variables, and spatial autoregressive lag and spatial cross‐regressive lag effects with respect to the endogenous variables. A key policy conclusion is that sector‐specific programs should be integrated and harmonized and that regionally differentiated development policies may yield greater returns than treating all locations the same. Estimamos un modelo de crecimiento de panel espacial regional por ecuaciones simultaneas, utilizando una nueva estrategia de estimación de cinco pasos que generaliza una enfoque descrito en Kelejian y Prucha. La región de estudio comprende los 418 condados Apalaches 1980‐2000. Las estimaciones muestran simultaneidades de retroalimentación entre las variables endógenas, convergencia condicional con respecto a las variables endógenas respectivas, y un retardo espacial autorregresivo y efectos de retardo regresivos cruzados espaciales con respecto a las variables endógenas. Una conclusión clave sobre políticas es que los programas sectoriales específicos deberían estar integrados y armonizados, y que las políticas de desarrollo diferenciadas regionalmente podrían producir mejores retornos que si se tratasen todas las localizaciones del mismo modo.      

Assessment of phenomenological failure criteria for wood

Many different phenomenological failure criteria have been proposed. These type of criteria do not explain the mechanism of failure itself. They merely identify failure (yes or no) and are usually regarded in practice as a simple and reliable tool for design. Most of them were developed for composite materials, but are extensively applied for wood. In this study, existing phenomenological strength criteria for orthotropic materials were applied to clear wood data. Instead of fitting the criteria to available experimental data, the criteria were used to predict failure of biaxial tests based on uniaxial strength. This procedure is closer to practice, and hence an answer to the question “is there any reliable failure criterion for wood?” Predictability of the criteria was assessed using normalisation procedure, and statistical significance of the difference of the means analysed. Based on the results, it can be concluded that a general criterion cannot be applied to predict failure, but should be chosen according to the biaxial stress state.     

A framework for scalable greedy coloring on distributed-memory parallel computers

We present a scalable framework for parallelizing greedy graph coloring algorithms on distributed-memory computers. The framework unifies several existing algorithms and blends a variety of techniques for creating or facilitating concurrency. The latter techniques include exploiting features of the initial data distribution, the use of speculative coloring and randomization, and a BSP-style organization of computation and communication. We experimentally study the performance of several specialized algorithms designed using the framework and implemented using MPI. The experiments are conducted on two different platforms and the test cases include large-size synthetic graphs as well as real graphs drawn from various application areas. Computational results show that implementations that yield good speedup while at the same time using about the same number of colors as a sequential greedy algorithm can be achieved by setting parameters of the framework in accordance with the size and structure of the graph being colored. Our implementation is freely available as part of the Zoltan parallel data management and load-balancing library.     

County-level determinants of local public services in Appalachia: a multivariate spatial autoregressive model approach

We develop a multivariate spatial autoregressive model of local public expenditure determination based on the maximization of a strictly quasi-concave community utility function. The existence of spatial interdependence is tested for both the spatial error and spatial lag model. The full model is estimated by efficient GMM following Kelejian and Prucha (J Real Estate Finan Econ 17(1):99?C121, 1998). The results indicate significant spillover effects among local governments with respect to spending on public services. The OLS estimates of the conventional (non-spatial) model and the corresponding maximum likelihood estimates of the spatial lag and the spatial error models are presented for comparison purposes. The GMM estimates are found to be more efficient.     

Optimisation of merged district-heating systems—benefits of co-operation in the light of externality costs

Studies have shown that separate actors can benefit from co-operation around heat supply. Such co-operation, for example, might be between an industry selling waste heat to a district-heating system or two district-heating systems interconnecting their respective systems. Co-operation could also be expected to reduce the environmental impacts of the energy systems by choosing the plants with the lowest emissions. It is widely accepted that the production of heat and electricity causes damage to the environment. This damage often imposes a cost on society, but not on company responsible. In general, using a broader system perspective when analysing local energy systems results in a lower total cost, more efficient use of plants and a greater potential for producing electricity in combined heat-and-power (CHP) plants. Internalising the externality costs in the energy system model facilitates the study of what co-operation can mean for reducing emissions. This study shows that co-operation between the two systems is on the whole cost-effective, but the benefits are greater when external costs are not included in the calculation. Considering externality costs in combination with current electricity prices would lead to a higher system cost, but the quantity of emission gases will be lower. If, on the other hand, the calculation is made taking externality costs and corresponding adjusted electricity prices (the adjustment being necessary to compensate for the additional cost due to externality costs) into consideration, the quantities of emission gases will rise because more heat-and-power will be generated by one of the CHP plants.