A detailed methodology to design the size of solar field for a parabolic trough plant is not explicitly available in open literature, particularly if thermal storage and hybridization are also considered, as most of the papers present a gross overview. This paper gives a procedure to determine the annual electricity generated for a parabolic trough based solar plant of a given rated capacity (1-50 MWe), at a chosen location & given hourly annual solar input, specified hours of thermal energy storage using a two-tank molten salt system and specified fraction of hybridization using natural gas. In this methodology losses due to shut down or cloud cover are also covered. The size of the solar field is optimized for the maximum annual solar to electric conversion efficiency using the concept of solar multiple (ratio of actual aperture area to the reference aperture area needed to get rated power output at maximum solar input). This procedure is validated with the existing parabolic trough plants (Solar Energy Generating Systems VI and Solana Generating Station) and it was found that the annual electrical energy generated by the plant matches reasonably well.Jodhpur, in India, was considered as a location for the case study and the results are presented to understand the influence of thermal storage and hybridization for a given capacity of the plant. The results for various combinations of thermal storage hours and fraction of hybridization used with respect to plant capacity, solar multiple, annual plant efficiency etc. have been discussed in detail. It is observed from the results that, under design conditions, the reference aperture area per MW decreases as plant capacity increases and reaches a limiting value asymptotically at a capacity of 50 MW. The optimized size of the solar field, with respect to annual efficiency, is found to be 1.4 and 2.3 times the size under design conditions for zero and six hours thermal storage respectively. The benefit of hybridization is high for lower solar multiples.

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We report our findings on the aerodynamic characteristics of thin slab delta wings at hypersonic speeds. We have tested wings with three sweeps (76°,70° and 65°) and four t/c ratios (0·04, 0·053, 0·066 and 0·10) using a special thin three-component balance. To date, the wing with tic of 0·040 is the thinnest wing ever tested without lee-side body at any hypersonic Mach number. The study was carried out at Mach number of 8·2, Reynolds number of 2·13 x 106 and incidence of -4° to 12°. In general, for any given t/c ratio, the increase in sweep decreased the CN whereas increased CM and CA. A possible explanation, for the effect of sweep, is given using the pressure data available in the literature. We also observed that for the sweeps considered, the t/c does not have any effect on CN and CL but increasing t/c increased CM and CA, reduced (L/D)max and moved the Xcp upstream. Blunt slab delta wings are shown to possess a unique property, wherein the CD increases with increase in sweep at higher sweep angles. This property also reflects in the (L/D) characteristics. Furthermore, the slab delta wings does not exhibit the classical CLα behaviour of sharp delta wings given in the literature. An empirical correlation has been developed to correlate CAo over a wide range of Mach number, t/c and sweep. Linearised theory has been shown to be useful in predicting the (L/D)max at Mach numbers as high as 20, for a wide range of t/c and sweep back angle.

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Solar tower technology has gained considerable momentum over the past decade. In a solar tower plant, the power collected by the heliostat field is strongly coupled to the height of the tower and its location with respect to the field. This paper provides a methodology to fix the boundary of the field (non-dimensionalised with respect to the tower height). While developing this methodology, it was realised that one needs to have an estimation of the nominal variation of packing density with nondimensional distance of the heliostat from the tower base. Packing density is fixed during the design of the field. A nominal variation of packing density was obtained by studying three existing plants which use radial staggered field patterns. This packing density data was used to arrive at contours of equal annual energy per unit land area (e l). This approach was then evaluated qualitatively and verified quantitatively with non-dimensional solar fields of existing plants. Based on these comparisons, it is suggested that for preliminary analysis, a seed value of e l = 0.16 MWh/m 2 may be used as a nominal value to set the field boundary. The significance of coupling of the solar field boundary with tower height is also discussed.