Techno-economic assessment of providing control energy reserves with a biogas plant

Grid stability is being challenged by the increasing integration of power plants with volatile power generation into the energy system. Power supply fluctuations must be compensated by energy system flexibility. The storability of the energy carrier enables biogas plants to generate power flexibly. In this study, the technical and economic effects of providing positive secondary control energy reserves with an Austrian biogas plant were assessed. The plant’s main focus lies in biomethane production with the option of heat and power generation through combined heat and power (CHP) units. A detailed simulation model of the investigated biogas plant was developed, which is presented in this work. Ex-post simulations of one year of flexible plant operation were conducted with this model. The findings show that the installed biogas storage capacity is sufficient to provide control energy reserves while simultaneously producing biomethane. Profitability of providing control energy reserves largely depends on the prices at the control energy market and on CHP unit start-up costs. A cost efficiency analysis demonstrated that investing in a hot water tank with a volume of 5 m³ for short-term heat storage turned out to be economically viable.

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Similarities and differences in four views of David.

In this article, each author gives a brief comment on similarities he or she sees throughout the case formulations captured in the articles by Watson (2010a), Silberschatz (2010), Goldfried (2010), and Caspar (2010). A systematic comparison is added. Overall, the impression is confirmed and maintained that if authors are ready to renounce the use of the jargon of their specific approach, many similarities can be found. There are nevertheless differences that would lead us to expect a different course of therapy and different effects beyond the main effect of recovery in the case of David, pursuing the conceptualization and interventions proposed by Watson (2010b). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analytical solutions for one-phase seepage flows impeded by wellbore seals

Steady, one-phase, plane and axisymmetric, Darcian seepage in a homogeneous rock adjacent to a partly isolated wellbore with annular seals is analytically studied. Water flows from an isobaric feeding contour and a fracture, which is kept at the same pressure as the feeding contour, to a wellbore. Partial isolation of the wellbore makes its wall a composition of intermittently arrayed no-flow boundaries, which model the wellbore seals, and isobaric surfaces, which model the annular compartments between the seals and a wellbore tubular on which the seals are mounted. Pressure drops from the aquifer (fracture) to the compartments and further to the borehole that generates a hierarchy of flows mathematically equivalent to the Toth [Freeze, R.A., Cherry, J.A., 1979. Groundwater. Prentice Hall, Englewood Cliffs] hydrogeological patterns of regional, intermediate and local groundwater flows on the scale of catchments. Conformal mappings of complex potential domains onto physical planes, where water seepage takes place, are used to tackle the fragments of the full feeding contour-fracture–sealed wellbore system. Explicit rigorous solutions for the flow characteristics (pressure and stream function) enable calculating optimal wellbore isolation with a criterion of minimal water flow rate from the fracture.     

LANASOL(R)染料比媒介染料更适用于羊毛染色

欧洲化学品管理局(ECHA)现已将重铬酸盐列入了高关注物质(SVHC)的名单.用含有重铬酸钾和重铬酸钠等的媒介染料染制羊毛的工厂正面临着越来越大的压力.这意味着采用这种技术的染厂未来可能要得到特别授权才能使用这种化学品.     

Personality–relationship transaction in young adulthood.

Personality and social relationships were assessed twice across a 4-year period in a general population sample of 489 German young adults. Two kinds of personality–relationship transaction were observed. First, mean-level change in personality toward maturity (e.g., increase in Conscientiousness and decrease in Neuroticism) was moderated by the transition to partnership but was independent of other developmental transitions. Second, individual differences in personality traits predicted social relationships much better than vice versa. Specifically, once initial correlations were controlled for, Extraversion, Shyness, Neuroticism, self-esteem, and Agreeableness predicted change in various qualities of relationships (especially with friends and colleagues), whereas only quality of relationships with preschool children predicted later Extraversion and Neuroticism. Consequences for the transactional view of personality in young adulthood are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spiral-CT-based assessment of tracheal stenoses using 3-D-skeletonization

PURPOSE: Demonstration of a technique for three-dimensional (3-D) assessment of tracheal-stenoses, regarding site, length and degree, based on spiral computed tomography (S-CT). PATIENTS AND METHODS: S-CT scanning and automated segmentation of the laryngo-tracheal tract (LTT) was followed by the extraction of the LTT medial axis using a skeletonization algorithm. Orthogonal to the medial axis the LTT 3-D cross-sectional profile was computed and presented as line charts, where degree and length was obtained. Values for both parameters were compared between 36 patients and 18 normal controls separately. Accuracy and precision was derived from 17 phantom studies. RESULTS: Average degree and length of tracheal stenoses was found to be 60.5% and 4.32 cm in patients compared with minor caliber changes of 8.8% and 2.31 cm in normal controls (p < 0.0001). For the phantoms an excellent correlation between the true and computed 3-D cross-sectional profile was found (p < 0.005) and an accuracy for length and degree measurements of 2.14 mm and 2.53% respectively could be determined. The corresponding figures for the precision were found to be 0.92 mm and 2.56%. CONCLUSION: LTT 3-D cross-sectional profiles permit objective, accurate and precise assessment of LTT caliber changes. Minor LTT caliber changes can be observed even in normals and, in case of an otherwise normal S-CT study, can be regarded as artifacts.