Device Physics of Dye Solar Cells

Design of new materials for nanostructured dye solar cells (DSC) requires understanding the link between the material properties and cell efficiency. This paper gives an overview of the fundamental and practical aspects of the modeling and characterization of DSCs, and integrates the knowledge into a user‐friendly DSC device model. Starting from basic physical and electrochemical concepts, mathematical expressions for the IV curve and differential resistance of all resistive cell components are derived and their relation to electrochemical impedance spectroscopy (EIS) is explained. The current understanding of the associated physics is discussed in detail and clarified. It is shown how the model parameters can be determined from complete DSCs by current dependent EIS and incident‐photon‐to‐collected‐electron (IPCE) measurements, supplemented by optical characterization, and used to quantify performance losses in DSCs. The paper aims to give a necessary theoretical background and practical guidelines for establishing an effective feedback‐loop for DSC testing and development.     

Transmutation of americium in a medium size sodium cooled fast reactor design

We have performed transient analysis of a medium size sodium cooled reactor loaded with different fractions of americium in the fuel. Unprotected Loss of Flow (ULOF) and Unprotected Transient over Power (UTOP) accidents were simulated in a geometrical model of BN600, using safety parameters obtained with the SERPENT Monte Carlo code.     

Explaining experience curves for new energy technologies: A case study of liquefied natural gas

Many new energy technologies seem to experience a fall in unit price as they mature. In this paper we study the unit price of liquefying natural gas in order to make it transportable by ship to gas power installations all over the world. Our point of departure is the experience curve approach, however unlike many other studies of new energy technologies, we also seek to account for autonomous technological change, scale effects and the effects of upstream competition among technology suppliers. To our surprise we find that upstream competition is by far the most important factor contributing to the fall in unit price. With respect to the natural gas business, this may have implications for the future development in prices as the effect of increased upstream competition is temporary and likely to weaken a lot sooner than effects from learning and technological change. Another more general policy implication, is that while promoting new energy technologies, governments must not forget to pay attention to competition policy.     

Modelling and experimental studies on heat transfer in the convection section of a biomass boiler

This paper describes a model of heat transfer for the convection section of a biomass boiler. The predictions obtained with the model are compared to the measurement results from two boilers, a 50 kW_th pellet boiler and a 4000 kW_th wood chips boiler. An adequate accuracy was achieved on the wood chips boiler. As for the pellet boiler, the calculated and measured heat transfer rates differed more than expected on the basis of the inaccuracies in correlation reported in the literature. The most uncertain aspect of the model was assumed to be the correlation equation of the entrance region. Hence, the model was adjusted to improve the correlation. As a result of this, a high degree of accuracy was also obtained with the pellet boiler. The next step was to analyse the effect of design and the operating parameters on the pellet boiler. Firstly, the portion of radiation was established at 3–13 per cent, and the portion of entrance region at 39–52 per cent of the entire heat transfer rate under typical operating conditions. The effect of natural convection was small. Secondly, the heat transfer rate seemed to increase when dividing the convection section into more passes, even when the heat transfer surface area remained constant. This is because the effect of the entrance region is recurrent. Thirdly, when using smaller tube diameters the heat transfer area is more energy‐efficient, even when the bulk velocity of the flow remains constant. Copyright © 2006 John Wiley & Sons, Ltd.     

Being polite while fulfilling different discourse functions in online classroom discussions

Using a discourse analytic qualitative approach, we investigated the naturally-occurring discourse that arose as part of two kinds of regular course activities, synchronous and asynchronous computer-mediated discussions. The messages contributed by members of a graduate course were analyzed for the kind of discourse functions and the kind of politeness strategies they displayed. Results indicated that synchronous CMD afforded more information seeking, information providing, and social comments than asynchronous CMD. Asynchronous discussions were slightly more likely to allow for such functions as discussion generating, experience sharing, idea explanation, and self-evaluation functions than synchronous discussions. Proportionately the two modes were similar in how politeness was expressed. Finally, in relating politeness and function, we found more politeness indicators when students were posting messages with such functions as positive evaluation and group conversation management, functions that carried the potential for face threat, and the least politeness associated with messages serving the function of experience sharing.     

High-pressure AB2 metal hydrides with low hysteresis

The effect of minor substitution for Mn on the basic hydriding properties of Ti_0.95Zr_0.05Cr_1.2Mn_0.7X_0.1 (X = Mn, Fe, Co or V) has been studied at 20 and 60 °C in order to find alloy-hydrogen systems for high-pressure applications in which high capacity, low hysteresis and flat pressure-composition-isotherm (PCI) plateaus are required. Samples have been synthesized by arc melting, and characterized by X-ray diffraction (XRD) and volumetric PCI measurements. Experimental evidence shows that even a small amount of V practically eliminates hysteresis while at the same time the PCI plateau slopes increase. Co-substitution also decreases hysteresis and keeps the PCI plateaus flat, but Fe-substitution does not seem to have any favourable effect on the basic hydriding properties. Possibility to study the relationship between hysteresis effect of high-pressure hydrides and their crystal structure is discussed.     

Book reviews

URBAN TRANSPORT. Kevin Hay and John Sheldrake (editors). Ashgate, Aldershot, UK, 1997. ISBN 1 85972 466 3 (hardback). 133 pp, bibliography and index. rrp $84.50.

ASIANS IN AUSTRALIA: Patterns of Migration and Settlement. James E. Coughlan and Deborah J. McNamara (editors). Macmillan Education Australia, Melbourne, 1997. ISBN 0 7329 4561 5 (hardback). 330pp, bibliography and index. rrp $64.95.

SOCIAL EXCLUSION IN EUROPEAN CITIES: Processes, Experiences and Responses. Ali Madanipour, Goran Cars and Judith Allen (editors). Jessica Kingsley and the Regional Studies Association, London, 1998. ISBN 1 85302 609 3 (paperback). 301pp, bibliography and index. rrp UK17.95stlg.

THE PROPERTY DEVELOPMENT PROCESS: Western Australia. Hugh Reynolds and Peter Solomon. Victor Publishing, Perth, 1998. ISBN 0 646 35442 6 (paperback). 174pp. rrp $65.00.

THE ANTHROPOLOGY OF POLICY: Critical Perspectives on Governance and Power. Shore, C. and Wright, S. (editors). Routledge, London, 1998. ISBN 0 415 13221 5. 294pp, bibliography and index. rrp $39.95.

THE CHANGING SHAPE OF WORK. Richard K. Brown (editor). Macmillan Press Limited, London, 1997. ISBN 0 312 17251 6 (paperback). 223pp including bibliography and index. rrp $42.95.