Techno-economic performance evaluation of solar tower plants with integrated multilayered PCM thermocline thermal energy storage: a comparative study to conventional two-tank storage systems

Copyright 2016 AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.Solar Tower Power Plants with thermal energy storage are a promising technology for dispatchable renewable energy in the near future. Storage integration makes possible to shift the electricity production to more profitable peak hours. Usually two tanks are used to store cold and hot fluids, but this means both higher investment costs and difficulties during the operation of the variable volume tanks. Instead, another solution can be a single tank thermocline storage in a multi-layered configuration. In such tank both latent and sensible fillers are employed to decrease the related cost up to 30% and maintain high efficiencies. This paper analyses a multi-layered solid PCM storage tank concept for solar tower applications, and describes a comprehensive methodology to determine under which market structures such devices can outperform the more conventional two tank storage systems. A detail model of the tank has been developed and introduced in an existing techno-economic tool developed by the authors (DYESOPT). The results show that under current cost estimates and technical limitations the multi-layered solid PCM storage concept is a better solution when peaking operating strategies are desired, as it is the case for the two-tier South African tariff scheme.Peer ReviewedPostprint (published version

Start-up performance of parabolic trough concentrating solar power plants

Concentrating solar power plants, even though they can be integrated with thermal energy storage, are still subjected to cyclic start-up and shut-downs. As a consequence, in order to maximize their profitability and performance, the flexibility with respect to transient operations is essential. In this regard, two of the key components identified are the steam generation system and steam turbine. In general it is desirable to have fast ramp-up rates during the start-up of a power plant. However ramp-up rates are limited by, among other things, thermal stresses, which if high enough can compromise the life of the components. Moreover, from an operability perspective it might not be optimal to have designs for the highest heating rates, as there may be other components limiting the power plant start-up. Therefore, it is important to look at the interaction between the steam turbine and steam generator to determine the optimal ramp rates. This paper presents a methodology to account for thermal stresses limitations during the power plant start up, aiming at identifying which components limit the ramp rates. A detailed dynamic model of a parabolic trough power plant was developed and integrated with a control strategy to account for the start-up limitations of both the turbine and steam generator. The models have been introduced in an existing techno-economic tool developed by the authors (DYESOPT). The results indicated that for each application, an optimal heating rates range can be identified. For the specific case presented in the paper, an optimal range of 7-10 K/min of evaporator heating rate can result in a 1.7-2.1% increase in electricity production compared to a slower component (4 K/min).</p

Depositional environment and biofacies characterisation of the Triassic (Carnian to Rhaetian) carbonate succession of Punta Bassano (Marettimo Island, Sicily)

The aims of this study are to reconstruct the geological setting of the Punta Bassano series (Marettimo Island, Egadi Archipelago, western Sicily) and its palaeogeographic evolution. The reference section for the Upper Triassic of Marettimo shows an alternation of marl and limestone beds together with brecciated levels. The limestones are both homogeneous mudstones with evaporite pseudomorphs and laminated with fenestrae. Foraminiferal, palynomorph, and ostracod associations constrain the Punta Bassano sequence to the Carnian-Rhaetian interval. The Punta Bassano succession represents a shallow inner ramp, ranging from open-marine environment with good water circulation to lagoonal and peritidal protected environments. Freshwater input from rivers or groundwater on the carbonate ramp is indicated by the ostracod microfauna. The comparison of facies and microfauna with those from other sequences of the Mediterranean Upper Triassic (Pyrenees, Corsica, Sardinia, and Tunisia) allows us to confine the Punta Bassano sedimentation to the northern margin of the Tethys, between the Corsican and the Pyrenean depositional setting. These new results indicate that Marettimo Island, which is considered a single structural element being formed by four tectonic units, is a piece of the southern margin of the European Plate, displaced over a longer distance to become part of the other Egadi Islands, when the Corso-Sarde block made its rotation and successive collision with the North African Margi

Protective Activity of Broccoli Sprout Juice in a Human Intestinal Cell Model of Gut Inflammation

Benefits to health from a high consumption of fruits and vegetables are well established and have been attributed to bioactive secondary metabolites present in edible plants. However, the effects of specific health-related phytochemicals within a complex food matrix are difficult to assess. In an attempt to address this problem, we have used elicitation to improve the nutraceutical content of seedlings of Brassica oleracea grown under controlled conditions. Analysis, by LC-MS, of the glucosinolate, isothiocyanate and phenolic compound content of juices obtained from sprouts indicated that elicitation induces an enrichment of several phenolics, particularly of the anthocyanin fraction. To test the biological activity of basal and enriched juices we took advantage of a recently developed in vitro model of inflamed human intestinal epithelium. Both sprouts’ juices protected intestinal barrier integrity in Caco-2 cells exposed to tumor necrosis factor under marginal zinc deprivation, with the enriched juice showing higher protection. Multivariate regression analysis indicated that the extent of rescue from stress-induced epithelial dysfunction correlated with the composition in bioactive molecules of the juices and, in particular, with a group of phenolic compounds, including several anthocyanins, quercetin-3-Glc, cryptochlorogenic, neochlorogenic and cinnamic acids

Guidance on safety evaluation of sources of nutrients and bioavailability of nutrient from the sources

Whenever new substances are proposed for use as sources of nutrients in food supplements, foods for the general population or foods for specific groups, EFSA is requested by the European Commission to perform an assessment of their safety and of the bioavailability of the nutrient from the proposed source. This guidance describes the scientific data required to allow an evaluation of the safety of the source within the established framework for risk assessment of food additives and novel food ingredients and the bioavailability of the nutrient from this source. This document is arranged in five main sections: one on technical data aimed at characterising the proposed source and at identifying potential hazards resulting from its manufacture and stability in food; one on existing authorisations and evaluation, providing an overview of previous assessments on the proposed source and their conclusions; one on proposed uses and exposure assessment section, allowing an estimate of the dietary exposure to the source and the nutrient based on the proposed uses and use levels; one on toxicological data, describing approaches which can be used to identify (in conjunction with data on manufacture and composition) and to characterise hazards of the source and any relevant breakdown products; the final section on bioavailability focuses on determining the extent to which the nutrient from the proposed source is available for use by the body in comparison with one or more forms of the same nutrient that are already permitted for use on the positive lists. This guidance document should replace the previous guidance issued by the Scientific Committee for Food and published in 2001

Analysis of synoptic scale water vapor transport

Massachusetts Institute of Technology. Dept. of Meteorology. Thesis. 1967. M.S.Bibliography: leaves 34-35.M.S

Cadmium accumulation and interactions with zinc, copper, and manganese, analysed by ICP-MS in a long-term Caco-2 TC7 cell model

The influence of long-term exposure to cadmium (Cd) on essential minerals was investigated using a Caco-2 TC7 cells and a multi-analytical tool: microwave digestion and inductively coupled plasma mass spectrometry. Intracellular levels, effects on cadmium accumulation, distribution, and reference concentration ranges of the following elements were determined: Na, Mg, Ca, Cr, Fe, Mn, Co, Ni, Cu, Zn, Mo, and Cd. Results showed that Caco-2 TC7 cells incubated long-term with cadmium concentrations ranging from 0 to 10 lmol Cd/l for 5 weeks exhibited a significant increase in cadmium accumulation. Furthermore, this accumulation was more marked in cells exposed long-term to cadmium compared with controls, and that this exposure resulted in a significant accumulation of copper and zinc but not of the other elements measured. Interactions of Cd with three elements: zinc, copper, and manganese were particularly studied. Exposed to 30 lmol/l of the element, manganese showed the highest inhibition and copper the lowest on cadmium intracellular accumulation but Zn, Cu, and Mn behave differently in terms of their mutual competition with Cd. Indeed, increasing cadmium in the culture medium resulted in a gradual and significant increase in the accumulation of zinc. There was a significant decrease in manganese from 5 lmol Cd/l exposure, and no variation was observed with copper. Abbreviation: AAS – Atomic absorption spectrometry; CRM– Certified reference material; PBS – Phosphate buffered saline without calcium and magnesium; DMEM – Dubelcco’s modified Eagle’s medium

La Corte di Giustizia torna sul concetto di atti persecutori in una prospettiva di avanzamento del diritto internazionale sui rifugiati

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Reversible Aphasia in Adolescence: A Late-Onset form of Landau Kleffner Syndrome? Report of a Single Case

An adolescent boy developed a long-lasting pattern of global aphasia, concomitant to focal (left temporal) EEG abnormalities; this was followed by complete recovery. Laboratory and neuroimaging studies were within normal limits. The possibility of a late-onset Landau Kleffner syndrome is discussed