Optimal Abandonment of Coal-Fired Stations in the EU

Carbon-fired power plants could face some difficulties in a carbon-constrained world. The traditional advantage of coal as a cheaper fuel may decrease in the future if CO2 allowance prices start to increase. This paper seeks to answer empirically the most drastic question that an operating coal-fired power plant may ask itself: under what conditions would it be optimal to abandon the plant and obtain its salvage value? We try to assess this question from a financial viewpoint following a real option approach at firm level so as to attract the interest of utilities and the broader investment community. We consider the specific case of a coal-fired power plant that operates under restrictions on carbon dioxide emissions in an electricity market where gas-fired plants are considered as marginal units. We also consider three sources of uncertainty or stochastic variables: the coal price, the gas price and the emission allowance price. These parameters are derived from future markets and are used in a three-dimensional binomial lattice to assess the value of the option to abandon. Our results (and sensitivity analysis) show the conditions that have to be met for the abandonment option to be exercised. This option to abandon coalfired plants is, however, hardly likely to be exercised if plants can operate as peaking plants. However, the decision may go differently in different circumstances, such as high CO2 allowance prices, very low volatility of allowance price or a decrease in the price of gas. The decision is also influenced by the remaining lifetime of the plant and its thermal efficiency. In any case the price of CO2 will work to bring forward the decision to abandon in older and less efficient coal-fired plants, which are less likely to be retrofitted in the future.power plants, coal, natural gas, emission allowances, futures markets, stochastic processes, abandonment, real options

Optimal Investment in Energy Efficiency under Uncertainty

This paper deals with the optimal time to invest in an energy efficiency improvement. There is a broad consensus that such investments quickly pay for themselves in lower energy bills and spared emission allowances. However, investments that at first glance seem worthwhile are frequently not undertaken. Our aim is to shed some light on this issue. In particular, we try to assess these projects from a financial point of view so as to attract sufficient interest from the investment community. We consider the specific case of a firm or utility already in place that consumes huge amounts of coal and operates under restrictions on carbon dioxide emissions. In order to reduce both coal and carbon costs the firm may undertake an investment to enhance energy efficiency. We consider three sources of uncertainty: the fuel commodity price, the emission allowance price, and the overall investment cost. The parameters of the coal price process and the carbon price process are estimated from observed futures prices. The numerical parameter values are then used in a three-dimensional binomial lattice to assess the value of the option to invest. As usual, maximising this value involves determining the optimal exercise time. Thus we compute the trigger investment cost, i.e. the threshold level below which immediate investment would be optimal. A sensitivity analysis is also undertaken. Our results go some way towards explaining the so-called energy efficiency paradox.Energy efficiency, Real options

Autophagy is activated and involved in cell death with participation of cathepsins during stress-induced microspore embryogenesis in barley

Microspores are reprogrammed towards embryogenesis by stress. Many microspores die after this stress, limiting the efficiency of microspore embryogenesis. Autophagy is a degradation pathway that plays critical roles in stress response and cell death. In animals, cathepsins have an integral role in autophagy by degrading autophagic material; less is known in plants. Plant cathepsins are papain-like C1A cysteine proteases involved in many physiological processes, including programmed cell death. We have analysed the involvement of autophagy in cell death, in relation to cathepsin activation, during stress-induced microspore embryogenesis in Hordeum vulgare. After stress, reactive oxygen species (ROS) and cell death increased and autophagy was activated, including HvATG5 and HvATG6 up-regulation and increase of ATG5, ATG8, and autophagosomes. Concomitantly, cathepsin L/F-, B-, and H-like activities were induced, cathepsin-like genes HvPap-1 and HvPap-6 were up-regulated, and HvPap-1, HvPap-6, and HvPap-19 proteins increased and localized in the cytoplasm, resembling autophagy structures. Inhibitors of autophagy and cysteine proteases reduced cell death and promoted embryogenesis. The findings reveal a role for autophagy in stress-induced cell death during microspore embryogenesis, and the participation of cathepsins. Similar patterns of activation, expression, and localization suggest a possible connection between cathepsins and autophagy. The results open up new possibilities to enhance microspore embryogenesis efficiency with autophagy and/or cysteine protease modulators.España, MINECO AGL2014-52028-R and AGL2017-82447-

Novel approaches to determine residual stresses by ultramicroindentation techniques: application to sand blasted austenitic stainless steel

This research addresses the determination of residual stresses in sandblasted austenitic steel by ultramicroindentation techniques using a sharp indenter, whose sensitivity to residual stress effects is said to be inferior to that for spherical ones. We propose the introduction of an angular correction in the model of Wang et al. that relates variations in the maximum load to the presence of residual stresses. Likewise, the contribution to hardness of grain size refinement and work hardening, developed as a consequence of the severe plastic deformation during blasting, is determined to avoid overestimation of the residual stresses. Measurements were performed on polished cross sections along a length of several microns, thus obtaining a profile of the residual stresses. Results show a good agreement with those obtained by synchrotron radiation on the same specimens, which validates the method and demonstrates that microindentation using sharp indenters may be sensitive to the residual stress effect.Peer Reviewe

Infestation maps and spatial stability of main weed species in maize culture

A study on the spatial distribution of the major weeds in maize was carried out in 2007 and 2008 in a field located in Golegã (Ribatejo region, Portugal). The geo-referenced sampling focused on 150 points of a 10 x 10 m mesh covering an area of 1.5 ha, before herbicide application and before harvest. In the first year, 40 species (21 botanical families) were identified at seedling stage and only 22 during the last observation. The difference in species richness can be attributed to maize monoculture favouring reduction in species number. Three of the most representative species were selected for the spatial distribution analysis: Solanum nigrum, Chenopodium album and Echinochloa crus-galli. The three species showed an aggregated spatial pattern and spatial stability over both years, although the herbicide effect is evident in the distribution of some of them in the space. These results could be taken into account when planning site-specific treatments in maize.Peer Reviewe

Importancia de la flora ornamental en la aeropalinologia de Sevilla (España)

Importancia de lo flora ornamental en la aeropalinología de Sevilla (España). El trabajo se ha realizado con un captador Cour que muestre() el aire de la ciudad durante ocho años consecutivos (1987- 1994). En total se han establecido 32 tipos polínicos ornamentales, pertenecientes a 30 familias diferentes y que suponen el 30% del polen total recogido. Los tipos con una representación al superior al 0.2% son, por orden de importancia: Cupressaceae, Platanus, Palmae, Moraceae, Fraxintts, Salicaceae, Casuarina, Acer, Ulmus y Citrus. La mayoría de los tipos restantes son de carácter entomófilo, por lo que su aparición en el aire es esporádica y en concentraciones inferiores a 1 grano semanal/m3. El polen ornamental supone un alto porcentaje de polen total entre diciembre y abril. La mayoría de los tipos aparecen en la primera mitad del año (excepto Palmae y Casuarina), produciéndose las semanas de máxima recogida de polen antes de la semana quince del año. La variación, a lo largo del año, de las concentraciones polínicas semanales se caracterizan por un perfil gráfico homogéneo, excepto Palmae y Citrus, en los que se observan continuas subidas y bajadas de las concentraciones.Importance of the ornamental flora in the aeropalynology of Seville (Spain). A Cour trap was used to sample the air of the city for eight consecutive years (1987-1994). A total of 32 pollen types has been established, belonging to 30 different families, and making up 30% of the total pollen collected. The types with a representation higher than 0.2% are, in order of importance: Cupressaceae, Matarais, Palmae, Moraceae, Fraxinus, Salicaceae, Casuarina, Acer, Ulmtts and Citrus. Most of the remaining types are entomophilous, so that their appearance in the air is sporadic and at concentrations lower than 1 grain weekly/m3. The ornamental pollen comprises a high percentage of the total pollen between December and April. Most of the types appear in the first half of the year (except Palmae and Casuarina), with the weeks of maximum pollen collection being before week fifteen of the year. The variation in the weekly pollen concentrations throughout the year shows a homogeneous graphic profile, except Palmae and Citrus, which have continual rises and falls in concentration

¿Es la autotoxicidad responsable de la inhibición del crecimiento de nuevas plántulas conespecíficas bajo el dosel de la invasora Acacia dealbata Link?

Autotoxicity is a particular form of allelopathy and is suspected to be responsible for regulating intraspecific competition under the Acacia dealbata Link (Fabaceae) canopy. Was established a bioassay with controlled conditions following the natural patterns of plant material accumulation under the A. dealbata canopy to determine the effects of chemical compounds released by leaves, bark, flowers and pods of the invasive species on germination and early growth of conspecific seedlings. Morphological changes caused by A. dealbata plant parts in roots of A. dealbata seedlings grown in natural and controlled conditions were evaluated with scanning electron microscopy. The composition and behavior of the phytotoxicity of litter under the A. dealbata canopy throughout its phenological cycle were studied. The main chemical compounds in the soil under the canopy were identified. Most of the tested plant parts inhibited the germination and early seedling growth, prevented the root hair formation, destroyed the rhizodermis and altered the parenchyma tissue of radicles. The pods caused the greatest autotoxicity in seedlings from both study conditions and dominated the plant material accumulated under the canopy for almost all of the phenological cycle. Soil analysis by GC-MS revealed the abundance of fatty acids and the presence of steroids. These results suggest that A. dealbata can control the growth of new conspecific seedlings under its own canopy, and improves the interspecific competitive performance of its adult plants in its non-native range.La autotoxicidad es una forma particular de alelopatía y se sospecha que es responsable de regular la competencia intraespecífica bajo el dosel de Acacia dealbata Link (Fabaceae). Se estableció un bioensayo en condiciones controladas, siguiendo patrones naturales de la acumulación de material vegetal bajo el dosel de A. dealbata, para determinar los efectos de compuestos químicos liberados por hojas, corteza, flores y vainas de esta especie invasora en la germinación y el crecimiento inicial de plántulas conespecíficas. Mediante microscopia electrónica de barrido se evaluaron cambios morfológicos inducidos por las diferentes partes de A. dealbata en raíces de plántulas conespecíficas cultivadas en condiciones controladas y naturales. Se estudió la composición y el comportamiento de la fitotoxicidad del material vegetal depositado bajo el dosel de A. dealbata durante su ciclo fenológico. Se identificaron los principales compuestos químicos presentes en el suelo situado bajo el dosel. La mayoría de los órganos evaluados inhibieron la germinación y el crecimiento temprano de las plántulas, impidieron la formación de pelos radicales, destruyeron la rizodermis y alteraron el tejido parenquimático de las radículas. Las vainas provocaron la mayor autotoxicidad en ambas condiciones de estudio, y dominaron el material vegetal acumulado bajo el dosel por casi todo el ciclo fenológico. El análisis de suelos mediante GC-MS, reveló abundancia de ácidos grasos y presencia de esteroides. Estos resultados sugieren que A. dealbata puede controlar el crecimiento de nuevas plántulas conespecíficas bajo su propio dosel, y mejorar la competitividad interespecífica de sus plantas adultas en su rango no nativo