A New Conversion Section for Parabolic Trough - Concentrated Solar Power (CSP-PT) Plants☆

Abstract One of the most important challenges facing our future is the balance between energy needs and production, in the framework of the CO 2 commitments almost universally adopted. The total energy consumption is still a prerogative of fossil fuels, with a share close to 90%, [1]; renewable energy, apart from the energy production from hydro, photovoltaic, biomass, waste and others, counts 3-4% since many years ago. This discouraging result calls for new conversion technologies based on renewables, if the concept of sustainability is really adopted. Concentrated Solar Power (CSP) plants technology could make the difference with respect to the other renewable technologies, thanks to "bridity"n combining the concentrated solar energy source and the conventional power generation (actually steam turbine plants as energy conversion section). In the sector of energy production, parabolic trough (PT) type is more promising. Recently, the Authors showed in [2,3] how convenient could be the utilization of gases as Heat Transfer Fluid (HTF) with advantages from a technological point of view in the heat collector section and, mainly, from the conversion section point of view, having the possibility to use gas turbines in which the HTF directly expands. In this work, the Authors discuss some thermodynamic and engineering aspects concerning the use of gases as HTF, limiting the attention to air and CO 2 and they further discuss the performances of an innovative gas turbine power plant. It is based on a sequence of compressions and expansions, intercooled and reheated (inside linear solar receivers) respectively, in order to increase cycle specific work and efficiency. The paper focuses the attention on the optimum number of compressions and expansions: when it changes, pressure levels change too, requiring a series of reheating processes which operate in parallel, so increasing the overall solar receiver length and, definitively, investment costs. The optimization has been done adopting as design parameter the power per unit of collector length [kW/m], which is the most sensible parameter defining investment cost

Anisotropy in the Turbulent Flow through Random and Emergent Rigid Vegetation on Rough Beds

In this study, we explore for the first time the turbulence anisotropy of flows through random and emergent rigid vegetation on rough beds, using the anisotropy invariant maps (AIMs). We present the results of an experimental campaign, based on Acoustic Doppler Velocimeter (ADV) measures, varying the bed sediment size (coarse sand, fine gravel, and coarse gravel), under the same hydraulic conditions. The evolution of the stress ellipsoid formed by the Reynolds stresses is discussed, together with the analysis of the anisotropic invariant function. We demonstrate that vegetation distribution is of paramount importance in the turbulence anisotropy evolution along the water depth. While in the case of a regular pattern the bed roughness is the key parameter in determining the shape of the stress ellipsoid in the near-bed region, in a random vegetation distribution this assumption is no longer valid. However, by increasing the bed roughness in such kind of arrangement, its effect on the turbulence anisotropy are visible in specific areas around the vegetation stem. This is confirmed by the analysis of the anisotropic invariant function calculated for different sections close to the stem itself

Does routinization affect occupation dynamics? Evidence from the ‘Italian O*Net’ data

Taking advantage of a dataset providing O*Net-type information on the task content of Italian occupations, this work analyses empirically if and to what extent employment patterns are affected by task characteristics in terms of ‘relative routinarity’. The investigation focuses on the 2005-2016 period relying on a panel including all Italian 4-digit occupations. Occupations characterized by relatively large shares of routinary tasks are penalized in terms of employment dynamics. This result proves to be robust despite the inclusion of a large number of worker, occupation and industry-level controls. A considerable heterogeneity between manufacturing and services is highlighted. While in services the negative relationship between routine task and employment is verified, in manufacturing the same relationship becomes statistically weak. Moreover, Italian occupations with high level of routinary tasks seems to get ‘younger’ rather than ‘older’. According to our empirical results, in highly routinary occupations youth employment tends to grow rather than shrink. Finally, being in highly routinary occupations seems to be less an issue for workers with college degree given the weaker significance of the RTI coefficient as compared to the whole sample model

Il prisma sudafricano. Sport, turismo e avventura nel paese del post-apartheid

This essay, which relies mostly on a cultural studies approach, aims to highlight the discursive and semiotic strategies which have defined official tourism promotion in South Africa since the end of apartheid. In particular, hosting the FIFA World Cup, a mega-event which placed the Country at the crossroads of international touristic flows in 2010, was not so much a finishing line, but rather a turning point for the self-refashioning of the country’s image. Shedding stereotyped definitions such as “the country of the big five”, South African Tourism has rebranded itself so as to mirror the new, complex reality and international status achieved by the nation since the advent of freedom. South Africa’s new public imaginary resembles a challenging, richly-textured prism, whose multiple facets concur to articulate a domestic discourse of reconciliation and unity along with the international projection of a powerful national identity, rebranded for the 21st century. By focusing on the promotion of so diverse branches of tourism as wildlife and conservation, township tourism and sport mega-events, this article aims to shed light on South Africa’s extraordinary achievement in nation-branding over the last decade, and on the way this process has been transformed into an effective tool of nation-building and public diplomac