A novel Compound Elliptical-type Concentrator for parabolic primaries with tubular receiver

The Parabolic Trough (PT) is the most used concentrator in CSP (Concentrated Solar Power). However, this concentrator technology is facing a significant challenge to increase its overall efficiency and cost-effectiveness. Meanwhile, other low-cost solutions such as Fresnel concentrators are also being perceived as potentially attractive. In order to achieve the lower cost goal, new optical solutions can be considered, in parallel with improvements coming, for instance, through the use of new materials or manufacturing solutions. But conventional PTs can still be improved to yield, for instance, higher concentration values, a possible starting point for higher conversion efficiency. These new solutions, in turn, can also be useful for other technologies and applications (Fresnel Concentrators, Central Tower Receivers, etc.). However it is easier to develop and test these solutions in conjunction with parabolic primaries (continuum primary). And that is the topic of this paper: to present a new Compound Elliptical-type Concentrator for a parabolic primary with a tubular receiver. A comparison is made between this new concentrator and two other concentrators (a conventional PT concentrator and a XX SMS (Simultaneous Multiple Surface) concentrator), as well as a calculation of the total amount of collected energy (kW h) for a particular location, Faro (Portugal). The paper ends with a discussion of the results obtained, their impact and possible applications in the future.

Selective Sonogashira Couplings in 1,2,4,5-tetrazine derivatives

1,2,4,5-Tetrazines are six-membered heterocyclic compounds in which the four nitrogen atoms are displayed in a symmetric fashion. Their reactivity is quite different from other heterocyclic aromatic systems due to its unique electron-withdrawing character, comparable to tetra-nitrobenzene. 1 In particular, 1,2,4,5- tetrazines are known to take part in [4+2] inverse-Diels–Alder cycloaddition processes which efficiently lead to the construction of substituted pyridazine systems that are important in drug development and biomarker applications. 2 However, the electronic character of 1,2,4,5-tetrazines hampered the development of 3- ethynyl- and 3,6-diethynyl-1,2,4,5-tetrazine derivatives for molecular electronic applications, proved by the scarcity of examples found in the literature. 3 Herein, we describe the synthesis and characterization of two novel ethynyl-based 1,2,4,5-tetrazine derivatives. Synthesis of 3,6-(4-bromophenyl)-1,2,4,5-tetrazine precursor (1) was achieved in good yield by Pinner’s method, starting from 4-bromobenzonitrile. Despite its low solubility in common organic solvents, this precursor was found to react smoothly under typical Sonogashira coupling conditions to selectively afford the 3-ethynyl (2) and 3,6-diethynyl (3) protected derivatives (Figure 1). Reaction conditions were evaluated in order to provide the best yields and to promote selectivity of the mono- or disubstituted ethynyl derivatives. Finally, deprotection was achieved affording, in the case of compound 3, an unprecedented 3,6- diethynyl-1,2,4,5-tetrazine compound. Time-Dependent Density Functional Theory (TDDFT) calculations for both deprotected ethynyl derivatives were used to simulate electronic spectra. A deep knowledge of the relevant electronic transitions involved and quantitatively satisfactory results of the calculated electronic excitations in comparison with experimental data were obtained.