Reconciliation of wind power forecasts in spatial hierarchies

We consider reconciliation of wind power forecasts in a spatial hierarchy with three aggregation levels. We produce base forecasts for the bottom level consisting of 407 substations (connection points for local groups of wind turbines). State-of-the-art forecasts from a commercial forecast provider are available for the middle and top levels, which consist of 15 regions and the entire Western Denmark (DK1), respectively. We find that the accuracy of the total forecast can be improved through spatial reconciliation, even with a relatively simple model used at the lowest level of the hierarchy. Computing the base forecasts for the substations using wind speed as the only predictor, the RMSE of the DK1 forecast is reduced by 20.5%, while the RMSE of the regional forecasts is reduced by 4.7%, on average, through reconciliation. The increase in accuracy is partly due to reduced errors in the individual regional forecasts and partly due to reduced residual correlation between the reconciled regional forecasts. We test adaptive estimation of the covariance matrix of the base forecast errors and find that it has a limited impact on the accuracy, hinting toward a time-stable covariance structure.     

Airfoil optimization for wind turbine application

An airfoil optimization method for wind turbine applications that controls the loss in performance due to leading edge contamination is developed and tested. The method uses the class‐shape‐transformation technique to parametrize the airfoil geometry and uses an adjusted version of the panel code XFOIL to calculate the aerodynamic performance. To find optimal airfoil shapes, the derivative‐free Covariance Matrix Adaptation Evolution Strategy is used in combination with an adaptive penalty function. The method is tested for the design of airfoils for the outer part of a megawatt‐class wind turbine rotor blade, and the results are compared with airfoils from Delft University. It is found that the method is able to automatically create airfoils with equal or improved performance compared with the Delft designs. For the tested application, the adjustments performed to the XFOIL code improve the maximum lift, post stall, and the overall drag predictions.     

Influence of the grain structure of yttria thin films on the hydrogen isotope permeation

Steel components are required in the infrastructure and the facilities of the hydrogen economy. The high hydrogen pressures in the hydrogen economy lead to embrittlement and surface corrosion of the steels. For the functionality of the facilities it is necessary to suppress the embrittlement and the surface corrosion of the steels by protective layers, e.g. ceramic thin films. With regard to fusion power plants ceramic thin films on the structural steel materials are also required. These thin films work as a tritium permeation barrier that is necessary to prevent the loss of the radioactive fuel inventory. Oxide thin films, e.g. Al₂O₃, Er₂O₃, and Y₂O₃, are promising candidates as tritium permeation barrier layers. In terms of the application in the first wall, this is especially true for yttrium due to its favorably short decay time after neutron activation compared to the other candidates. The Y₂O₃ layers with thicknesses of 0.5 μm–1 μm are deposited on both substrate sides by RF magnetron sputter deposition. Since the microstructure of the barrier layer plays an important role for the permeation reduction, layers with three different magnetron process modes and thus three different microstructures are prepared. After annealing the cubic crystal structure of all thin films is verified by X-ray diffraction and the different microstructures are investigated by scanning electron microscopy and transmission electron microscopy. The Y₂O₃ stoichiometry of all thin films and a chromium oxide material segregation at the interface are verified by analysis methods such as X-ray photoelectron spectroscopy. The permeation reduction factors of all thin films are determined in gas-driven deuterium permeation experiments. Corresponding to the three different microstructures, reduction factors of 25, 45, and 1100 are identified. Thus, the permeation reduction is strongly dependent on the Y₂O₃ microstructure. The measurement results suggest that a high density of grain boundaries leads to a high hydrogen permeation.     

Behavior of scaled-up sodium alanate hydrogen storage tanks during sorption

Sodium alanate is being experimentally tested in scaled-up quantities. For this purpose, several tanks have been designed and constructed. The tank functionality during absorption and desorption of hydrogen was demonstrated in a scale of 8 kg of alanate, with a peak technical absorption time below 10 min. The absorption and desorption data show good reproducibility. Neutron radiography was used in another tank to show the powder’s physical behavior during sorption, showing conservation of the macroscopic structure during cycling.     

A general method for analysis of planar mechanisms using a modular approach

A method that covers both kinematic, inverse dynamic, dynamic, and static analysis of any type of planar mechanism is presented. The method is based on a subdivision of the mechanism to be analyzed into kinematic chains that are categorized as either neutral or expansion modules. The neutral modules are the well known Assur Groups, characterized by the fact that they have no effect on the degree of freedom of the mechanism. On the contrary each expansion module increases the degree of freedom by one. The coordinates that correspond to the indeterminancy of the expansion modules may be identified as a set of independent coordinates for the subdivided mechanism and used in any type of analysis. The method as it is described in the present paper has been implemented in a menu-controlled PC computer program CADME. A number of practical observations concerning the implementation of a modular approach is made and discussed.     

Interactions of human chorionic gonadotropin with genotype and parity on fertility responses of lactating dairy cows

Fertility-promoting effects of treatment of lactating dairy cattle with human chorionic gonadotropin (hCG) after artificial insemination (AI) have been variable. Here, we tested whether fertility response to hCG in lactating Holstein cows interacts with genotype and parity. Primiparous (n = 538) and multiparous (n = 613) cows were treated with hCG (3,300 IU) or vehicle 5 d after AI. Pregnancy was diagnosed on d 32 and 60 after AI. A subset of cows (n = 593–701) was genotyped for 4 single nucleotide polymorphisms (SNP) previously associated with fertility. Treatment with hCG increased progesterone concentration on d 12 after AI regardless of genotype or parity. Pregnancy per AI was improved by hCG in primiparous cows but not in multiparous cows. Moreover, hCG treatment interacted with a SNP in coenzyme Q9 (COQ9) to affect fertility. Fertility of cows treated with vehicle was greatest for the AA allele, whereas fertility was lowest for the same genotype among cows treated with hCG. Pregnancy per AI was also affected by genotype for heat shock protein A1-like (HSPA1L) and progesterone receptor (PGR), but no interactions were observed with treatment. Genotype for a SNP in prostate androgen-regulated mucin-like protein 1 (PARM1) was not associated with fertility. Overall, results show that variation in response to hCG treatment on fertility depends on parity and interacts with a SNP in COQ9.     

Effect of starter cultures on properties of soft white cheese made from camel (Camelus dromedarius) milk

This experiment was conducted to investigate the effect of starter cultures on the physicochemical properties, texture, and consumer preferences of soft white cheese (SWC) made from camel (Camelus dromedarius) milk. The experiment was laid out in a completely randomized design with 5 treatments [starter cultures; i.e., 1 thermophilic (STI-12), 2 blended (RST-743 and XPL-2), and 2 mesophilic (R-707 and CHN-22) cultures]. Starter cultures STI-12 and RST-743 were inoculated at 37°C, whereas XPL-2, R-707, and CHN-22 were inoculated at 30°C. Camel milk inoculated using STI-12 and RST-743 cultures resulted in faster acidification than XPL-2, R-707, and CHN-22 cultures. Camel milk SWC made using STI-12 and CHN-22 cultures gave lower pH (4.54) and titratable acidity (0.59), respectively, whereas R-707 culture resulted in high cheese yield (13.44 g/100 g). In addition, high fat (20.91 g/100 g), protein (17.49 g/100 g), total solids (43.44 g/100 g), and ash (2.40 g/100 g) contents were recorded for SWC made from camel milk made using RST-743 culture. Instrumental analysis of cheese texture revealed differences in resistance to deformation in which camel milk SWC made using RST-743 culture gave higher firmness (3.20 N) and brittleness (3.12 N). However, no significant difference was observed among camel milk SWC adhesiveness made using different starter cultures. Consumer preference for appearance, aroma, taste, and overall acceptances of SWC were affected by inoculation of starter cultures. Considering curd firmness, cheese yield, compositional quality, and textures using STI-12, RST-743, and R-707, these cultures were found to be better for the manufacture of camel milk SWC.