Effect of soiling in CPV systems

The effect of soiling in flat PV modules has been already studied, causing a reduction of the electrical output of 4% on average. For CPV's, as far as soiling produces light scattering at the optical collector surface, the scattered rays should be definitively lost because they cannot be focused onto the receivers again. While the theoretical study becomes difficult because soiling is variable at different sites, it becomes easier to begin the monitoring of the real field performance of concentrators and then raise the following question: how much does the soiling affect to PV concentrators in comparison with flat panels?? The answers allow to predict the PV concentrator electrical performance and to establish a pattern of cleaning frequency. Some experiments have been conducted at the IES-UPM and CSES-ANU sites, consisting in linear reflective concentration systems, a point focus refractive concentrator and a flat module. All the systems have been measured when soiled and then after cleaning, achieving different increases of ISC. In general, results show that CPV systems are more sensitive to soiling than flat panels, accumulating losses in ISC of about 14% on average in three different tests conducted at IESUPM and CSES-ANU test sites in Madrid (Spain) and Canberra (Australia). Some concentrators can reach losses up to 26% when the system is soiled for 4 months of exposure

The homotopy type of the loops on (n−1)(n-1)-connected (2n+1)(2n+1)-manifolds

For $n\geq 2$ we compute the homotopy groups of $(n-1)$-connected closed manifolds of dimension $(2n+1)$. Away from the finite set of primes dividing the order of the torsion subgroup in homology, the $p$-local homotopy groups of $M$ are determined by the rank of the free Abelian part of the homology. Moreover, we show that these $p$-local homotopy groups can be expressed as a direct sum of $p$-local homotopy groups of spheres. The integral homotopy type of the loop space is also computed and shown to depend only on the rank of the free Abelian part and the torsion subgroup.Comment: Trends in Algebraic Topology and Related Topics, Trends Math., Birkhauser/Springer, 2018. arXiv admin note: text overlap with arXiv:1510.0519

Immunological Change in a Parasite-Impoverished Environment: Divergent Signals from Four Island Taxa

Dramatic declines of native Hawaiian avifauna due to the human-mediated emergence of avian malaria and pox prompted an examination of whether island taxa share a common altered immunological signature, potentially driven by reduced genetic diversity and reduced exposure to parasites. We tested this hypothesis by characterizing parasite prevalence, genetic diversity and three measures of immune response in two recently-introduced species (Neochmia temporalis and Zosterops lateralis) and two island endemics (Acrocephalus aequinoctialis and A. rimitarae) and then comparing the results to those observed in closely-related mainland counterparts. The prevalence of blood parasites was significantly lower in 3 of 4 island taxa, due in part to the absence of certain parasite lineages represented in mainland populations. Indices of genetic diversity were unchanged in the island population of N. temporalis; however, allelic richness was significantly lower in the island population of Z. lateralis while both allelic richness and heterozygosity were significantly reduced in the two island-endemic species examined. Although parasite prevalence and genetic diversity generally conformed to expectations for an island system, we did not find evidence for a pattern of uniformly altered immune responses in island taxa, even amongst endemic taxa with the longest residence times. The island population of Z. lateralis exhibited a significantly reduced inflammatory cell-mediated response while levels of natural antibodies remained unchanged for this and the other recently introduced island taxon. In contrast, the island endemic A. rimitarae exhibited a significantly increased inflammatory response as well as higher levels of natural antibodies and complement. These measures were unchanged or lower in A. aequinoctialis. We suggest that small differences in the pathogenic landscape and the stochastic history of mutation and genetic drift are likely to be important in shaping the unique immunological profiles of small isolated populations. Consequently, predicting the impact of introduced disease on the many other endemic faunas of the remote Pacific will remain a challenge

A study of shading and resistive loss from the "fingers of encapsulated solar cells

Optimised solar cell design is dependent on the assumed shading and resistance losses associated with front contacts. In this study, a spectrophotometer with integrating sphere attachment was used to measure the reflection from the front surface of encapsulated silver electroplated front contact solar cells. The results obtained are in good agreement with a previous study by one of the authors using a different method. The measured effective shading loss is about one third of the coverage fraction of the cell grid because of trapping of light reflected from the grid. The grid loss in 4 x 5 cm silver electroplated front contact solar cells was found to be similar to the predicted loss from buried grid and rear point contact solar cells operating at 30 suns concentration

Natural sunlight calibration of silicon solar cells

The light source is very important when calibrating solar cells. Commonly used light sources – solar simulators – are expensive and frequently inaccurate. This work shows that testing solar cells under natural sunlight is simpler, cheaper, and more accurate than all but the most careful simulator measurements. Solar spectra generated with the model SMARTS2 show that the direct-beam solar spectrum, under clear sky and low air mass conditions, is an excellent match to the AM1.5G standard. Millions of simulations of a broad range of silicon cells (efficiencies 6-25%) under the modelled direct-beam spectra show that measurement uncertainty of less than 5% is achievable. This is comparable to the reproducibility of results achieved by standards laboratories. Climate data shows that the required atmospheric conditions occur commonly in summer for all but polar latitudes. Finally, it is shown that the important atmospheric conditions can be measured without expensive equipment

Initial field performance of a hybrid CPV-Tmicroconcentrator system

The first prototype of the hybrid CPV-T ANU-Chromasun micro-concentrator has been installed at The Australian National University, Canberra, Australia. The results of electrical and thermal performance of the micro-concentrator system, including instanta