On the physics of power,energy and economics of renewable electric energy sources - Part II

Renewable Energy Technologies (RETs) are often recognized as less competitive than traditional electric energy conversion systems. Obstacles with renewable electric energy conversion systems are often referred to the intermittency of the energy sources [1] and the relatively high maintenance cost. However, due to an intensified discourse on climate change and its effects, it has from a societal point of view, become more desirable to adopt and install CO₂ neutral power plants. Even if this has increased the competitiveness of RETs in a political sense, the new goals for RET installations must also be met with economical viability. We propose that the direction of technical development, as well as the chosen technology in new installations, should not primarily be determined by policies, but by the basic physical properties of the energy source and the associated potential for inexpensive energy production. This potential is the basic entity that drives the payback of the investment of a specific RET power plant. With regard to this, we argue that the total electric energy conversion system must be considered if effective power production is to be achieved, with focus on the possible number of full loading hours and the Degree of Utilization [2]. This will increase the cost efficiency and economical competitiveness of RET investments, and could enhance faster diffusion of new innovations and installations without over-optimistic subsidies. This paper elaborates on the overall problem of the economy of renewable electric energy conversion systems by studying the interface between physics, engineering and economy reported for RET power plants in different scientific publications. The core objective is to show the practical use of the Degree of Utilization and how the concept is crucial for the design and economical optimization disregarding subsidies. The results clearly indicate that the future political regulative frameworks should consider the choice of renewable energy source since this strongly affects the economical output from the RET power plants.     

The mechanism of failure in bending of paperboard

The behaviour of paperboard beams subjected to pure bending is analysed and related to tensile and compression stress-strain behaviour. Since the compression strength is lower than the tensile strength, beam failure occurs in compression. However, beam failure does not occur when the ultimate strain in pure compression is reached in the surface fibres. A plastic yielding in compression, which gives good agreement between experimentally-determined and theoretically-calculated bending moments up to failure is therefore suggested. At failure, the elastic energy stored in the sample causes propagation of an interlaminar crack at the compression side, which is observed in scanning electron micrographs.     

Reply to Dunnette's "Comments on Abrahams and Alf's 'Pratfalls in moderator research'."

Discusses M. Dunnette's (see PA, Vol. 49:Issue 1) comments on moderator techniques and shows that they are only partly correct because of their total reliance on improvements in hit rate. Instances are discussed in which it would seem hazardous to rely solely on empirical results in evaluating a moderator technique, while dismissing conceptual arguments based on methodological flaws. Limitations of his revision of quadrant analysis are discussed. Dunnette's further suggestion for completely removing the bias is shown to be theoretically impossible. Finally, the value of his 2-stage strategy is reduced considerably as a result of incomplete use of data but may, in some cases, improve prediction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A modified index for control performance assessment

A control performance index which relates actual output variance to minimal achievable variance was first presented by Harris [T.J. Harris, Assessment of control loop performance, The Canadian Journal of Chemical Engineering 67 (1989) 856–861]. In the present paper, a modification of that index is applied. Instead of comparing to minimum variance control — which corresponds to placing all closed-loop poles in the origin — one pole is placed using either control design guidelines or additionally available process knowledge. Some possible choices of the free closed-loop pole are discussed. Based on this modified closed-loop system, a performance index can be calculated which relates actual output variance to the minimum achievable variance using the modified closed-loop system. It is shown that for the calculation of this index no other information apart from the measured process output and the time-delay is necessary. Furthermore, a method is presented which allows the assessment of the accuracy of the calculated index. The original Harris index and the proposed modified index are computed using data from industrial processes.     

The impact of individual motivations on idea submission and future motivation to participate in an organization's virtual idea campaign

We used time‐lagged survey data to investigate the effects of various types of motivation on idea submission and future motivation to participate in a virtual idea campaign (VIC). We also used qualitative data to illuminate context and enrich explanations. Applying forms of motivation from self‐determination theory—intrinsic motivation and external motivation—and the additional composite form of identified‐prosocial motivation, our study offers insight into their effects on idea submission and future motivation to participate in idea campaigns. We found that intrinsic motivation led to idea submission and future motivation to participate, while external motivation negatively related to idea submission. Identified‐prosocial motivation positively related to participants' motivation to participate in future idea campaigns, but surprisingly, its interaction with intrinsic motivation did not lead to idea submission. We provide managers and innovation researchers with useful lessons for the effective management of idea campaigns in organizations, and our results highlight the value of autonomous forms of motivation, especially intrinsic motivation.     

Laser-induced charge separation in CdSe nanowires

A combination of electrostatic force microscopy and optical microscopy was used to investigate the charge state of individual CdSe nanowires upon local illumination with a focused laser beam. The nanowires were found to be positively charged at the excitation spot and negatively charged at the distant end(s). For high laser powers, the amount of accumulated charges increases logarithmically with the laser power. These effects are described by a diffusion-based model where the results are in good agreement with the experimentally observed effects. On the basis of this model the charge imbalance along the nanowire should establish in the course of nanoseconds. The net charge separation within homogeneous nanowires upon local illumination is of importance for several electronic devices.     

THE INFLUENCE OF 2-ACETOHYDROXY ACIDS ON THE DETERMINATION OF VICINAL DIKETONES IN BEER AND DURING FERMENTATION

During sampling and determination of diacetyl, 2-acetohydroxy acids are easily converted to vicinal diketones. A simple procedure for gas chromatographic determination of diacetyl, 2-acetolactate, acetoin and the homologous compounds is given. By careful sampling, less than 0·01 ppm of diacetyl was detected during the main fermentation in one brewery, whereas another strain of brewer's yeast yielded a maximum of 1·7 ppm of diacetyl. When samples of fermenting liquids are exposed to air at 60°C, complete conversion of 2-acetohydroxy acids takes place in less than one hour. The possibility that part of 2-acetolactate may be converted to acetoin, however, cannot be excluded. In finished beer 2-acetolactate levels of 0·2–0·5 ppm were observed. During the main fermentation the values ranged from 0·5–2·5 ppm.     

Technical note: A toy as tool: a low-cost image analysis system for the evaluation of tumor size in experimental small animal models

Image analysis systems are an essential tool in measurements of size of intraparenchymal tumors or lesions in experimental small animal models. Conventional image analysis systems are relatively expensive. We therefore compared the performance of a professional image analysis system with an inexpensive setup by evaluating tumor size in an orthotopic glioma mouse model. The maximum cross-sectional tumor area of H&E stained brain-slides of two groups of mice (treatment and control group) was measured by two independent investigators using a professional image analysis system (Leica DM IRB microscope) with the Leica Quantimet 500c software, and a low-cost-system (Intel QX3 microscope) with a non-commercial image analysis software. Mean tumor volumes were calculated and the results from each of the image analysis systems, investigators, and treatment effects were compared. The tumor volumes as measured with the low-cost and the professional system differed between -3.7 and +7.5% (P = 0.69-0.99). Measurements made by investigator A and B differed between -7.0 and +3.9% (P = 0.69-0.88). Treatment in all cases significantly reduced the tumor volume between 58.4 and 62.7% (P = 0.0002 or 0.0003), regardless of the investigator or the used image analysis system. We therefore conclude that the QX3 low-cost microscope in combination with a non-commercial image-analysis software represents an inexpensive solution to reliably analyze the size of regions of interest, if they provide a sufficient contrast. However, the low-cost setup due to its low resolution definitely limits a detailed analysis of histologic features.     

Large array of single, site-controlled InAs quantum dots fabricated by UV-nanoimprint lithography and molecular beam epitaxy

We present the growth of single, site-controlled InAs quantum dots on GaAs templates using UV-nanoimprint lithography and molecular beam epitaxy. A large quantum dot array with a period of 1.5 μm was achieved. Single quantum dots were studied by steady-state and time-resolved micro-photoluminescence experiments. We obtained single exciton emission with a linewidth of 45 μeV. In time-resolved experiments, we observed decay times of about 670 ps. Our results underline the potential of nanoimprint lithography and molecular beam epitaxy to create large-scale, single quantum dot arrays.