Combined use of volumetric expanders and Scheffler receivers to improve the efficiency of a novel direct steam solar power plant

This research proposes an innovative solar thermal plant able to generate mechanical power through an optimized system of heliostats with Scheffler-type solar receivers coupled with screw-type steam expanders. Scheffler receivers appear to perform better than parabolic trough collectors due to the high compactness of the focal receiver, which minimizes convective and radiative heat losses even at high vaporization temperatures. At the same time, steam screw expanders are volumetric machines that can be used to produce mechanical power with satisfactory efficiency also by admitting two-phase mixtures and with further advantages compared to steam turbines: low working fluid velocities, low operating pressures, and avoidance of overheating. This study establishes a mathematical model to assess the energetic advantages of the planned solar thermal power system by evaluating the solar-to-electricity efficiency for different off-design working conditions. For this purpose, a numerical model on the Scheffler receiver is initially investigated, thus assessing all the energy losses which affect the heat transfer phase. A thermodynamic model is then developed to evaluate the energy losses and performance of the screw expander under real working conditions. Finally, parametric optimization of the solar energy conversion is performed in a wide range of operating conditions by establishing thermodynamic formulations related to the whole solar electricity generation system. Water condensation pressure and vaporization temperature are so optimized with respect to global energy conversion efficiency which, under the best operating conditions achieved in this research, rises from 10.9% to 14.4% with increasing solar irradiation intensity. Hence, the combined use of screw expanders and Scheffler receivers for solar thermal power system application can be a promising technology with advantages over parabolic dish concentrators. Novelty statement: This research proposes an innovative direct steam solar power plant based on an SRC, with water utilized as both heat transfer and working fluid, equipped with Scheffler solar receivers as a thermal source and screw expanders as work-producing devices. Technical studies and energy assessments of this kind of SEGS at part-load operation do not exist in scientific literature; after reviewing the literature, it was determined that volumetric expanders have been rarely combined with Scheffler receivers for solar thermal power system application. In effect, combined use of screw expanders and Scheffler-type solar concentrator in a direct steam solar power system represents a completely new plant configuration; however, as a promising DSG solar system, at present numerical model of this new sort of SEGS is lacked in literature and the optimum operating conditions have yet to be defined. For this reason, the chief objective of this paper is to define a first parametric optimization of all thermodynamic variables involved to maximize global efficiency of the proposed solar thermal power generation system for ordinary working conditions

Evaluation of Small Vase and Y-trellis Orchard Systems for Peach and Nectarine Production in Mediterranean Regions

Two peach planting systems, Small Vase (SV) and Y-trellis (Y), were evaluated and compared in the Mediterranean settings of Southern Italy. The two orchards were located next to each other on relatively uniform soil and terrain, and the observations included two peach (Rich May and Summer Rich) and two nectarine (Big Bang and Nectaross) cultivars. In the SV system, trees were spaced at 4.5 x 2.5 m (888 trees/ha), whereas in the Y system, trees were spaced at 5.5 x 2 m (909 trees/ha) and no roof gap was left between rows. Yield per tree, fruit size grade, unit price of sold peaches for each size grade, materials and labor for cultural management and associated costs, fixed costs at planting, and grower's profit were quantified during the first six years from planting. Fixed costs at planting were twice as much in the Y system, and no significant yield was recorded in the first two years in any of the two systems. Regardless of cultivar, the Y system reported 20% higher yields, 31% greater amount of management labor, and 10% lower labor efficiency (kg fruits/hr) than the SV system. Fruit unit value (euro/kg) was similar in the two systems. Profit varied greatly depending on the cultivar, and only 'Nectaross' generated a greater profit in the Y than the SV system. For this cultivar, the pay-back period (years needed to pay off the additional investment of establishing a Y trellis by its additional profit) was 2.5 years, indicating an advantage of the Y system over the SV by the 4th year. The yield gap between the two systems tended to decrease after the 5th year. The latter trend, along with the high initial investment and management costs in the Y system, suggests better performance and more sustainable productions in the SV than in the Y system

Effect of rootstock on growth, yield and fruit characteristics in cv 'Bianca' pistachio (Pistacia vera L.) trees

This paper, following preliminary field evaluation trials started in 1993, reports a study on the effect of eight different in vitro-propagated clonal rootstocks (P. atlantica and P. integerrima) and one seedling rootstock (P. terebinthus) on the vegetative and productive behaviour of pistachio cultivar 'Bianca'. The trees, budded in 1991, were grown using standard cultural practices for dry-land farming in a sandy clay loam soil, located inland in Sicily. On average, clones of P. integerrima (I-6 and I-2) were the most vigorous rootstocks. Clones of P. atlantica had intermediate vigour. Rootstock significantly affect yield but not fruit weight, kernel to nut ratio, splitting and blanking percentages. The highest yield efficiencies were observed with I-4 and A-3 and A-5, whereas the lowest were obtained with I-6 and I-2 and A-8. Nut shape was significantly affected by the rootstock. Slight differences in leaf mineral content were observed among the tested graft combinations

Automatic detection and agronomic characterization of olive groves using high-resolution imagery and LIDAR data

The Common Agricultural Policy of the European Union grants subsidies for olive production. Areas of intensified olive farming will be of major importance for the increasing demand for oil production of the next decades, and countries with a high ratio of intensively and super-intensively managed olive groves will be more competitive than others, since they are able to reduce production costs. It can be estimated that about 25-40% of the Sicilian oliviculture must be defined as “marginal”. Modern olive cultivation systems, which permit the mechanization of pruning and harvest operations, are limited. Agronomists, landscape planners, policy decision-makers and other professionals have a growing need for accurate and cost-effective information on land use in general and agronomic parameters in the particular. The availability of high spatial resolution imagery has enabled researchers to propose analysis tools on agricultural parcel and tree level. In our study, we test the performance of WorldView-2 imagery relative to the detection of olive groves and the delineation of olive tree crowns, using an object-oriented approach of image classification in combined use with LIDAR data. We selected two sites, which differ in their environmental conditions and in their agronomic parameters of olive grove cultivation. The main advantage of the proposed methodology is the low necessary quantity of data input and its automatibility. However, it should be applied in other study areas to test if the good results of accuracy assessment can be confirmed. Data extracted by the proposed methodology can be used as input data for decision-making support systems for olive grove management

An investigation of the self- and inter-incompatibility of the olive cultivars 'Arbequina' and 'Koroneiki' in the Mediterranean climate of Sicily

In this investigation, the self-(in)compatibility of the Spanish cultivar Arbequina and the Greek cultivar Koroneiki was studied for the first time in Sicily, where these low vigour cultivars were recently introduced in super-intensive olive groves. Self- (S.P.) and openpollination (O.P.) tests, observation of fruit set and paternity test of seeds with microsatellite (SSR) markers, were performed to ascertain whether these cultivars were self-fertile and/or inter-compatible. For S.P. tests, branches with flowers at the balloon stage were bagged. For the O.P. tests, flowers were left to pollinate under natural conditions. Fruits from S.P. and O.P. were collected in November and fruit set was calculated. Genomic DNA was extracted from seeds. None of the 'Arbequina' seeds studied in either the S.P. or O.P. tests originated from self-fertilization. In addition, none of these seeds had 'Koroneiki' as the pollen parent. In contrast, 'Koroneiki' was found to be predominantly self-compatible in self-bagged branches, with 70% of the seeds originating from selffertilization. However, the incidence of self-fertilization was low (11%) in seeds from the O.P. test. Low levels of inter-compatibility were found between 'Arbequina' and 'Koroneiki', while many local cultivars were found to be good pollinators. The information presented here will be useful to growers for planning their orchards with suitable pollinators and for our breeding program aiming at obtaining new low vigour olive genotypes. In addition, our results suggested that the recent model of attribution of S-alleles and the prediction of suitable pollinizers for a given variety should be more cautious and always based on controlled crosses and paternity testing of seed from those crosses

Musculoskeletal Pain in Gymnasts: A Retrospective Analysis on a Cohort of Professional Athletes

Gymnastics athletes are exposed to a high risk of injury, but also of developing muscu- loskeletal pain. These data are still little investigated in the available scientific literature. An online survey was distributed to 79 professional athletes who practiced artistic and rhythmic gymnastics. The survey collected demographic and anthropometric data, information about the sport practice, the training sessions, the prevalence of musculoskeletal pain gymnastics-related, and lifestyle habits. Musculoskeletal pain had a high prevalence, involving 65 of 79 athletes (82.3%). A significant correla- tion was found between musculoskeletal pain and the duration of sports practice, both for general pain (p = 0.041) and for specific districts: right wrist pain (p = 0.031), left wrist pain (p = 0.028), right shoulder (p = 0.039), left hip (p = 0.031), right thigh (p = 0.031), and left knee (p = 0.005). Another statistical association was found between right wrist pain and BMI (p = 0.001), and hip pain and BMI (p = 0.030). Hours spent in a sitting position were also correlated with the incidence of pain (p = 0.045). Wrist pain and right shoulder pain had a statistically significant association with the age of the athletes (right wrist pain: p = 0.038; left wrist pain: p = 0.004; right shoulder pain: p = 0.035). The more the gymnasts practice this sport, the more likely they are to develop musculoskeletal pain. Increased age and a higher BMI, as well as daily prolonged sitting position, seem to be potential risk factors for the onset of musculoskeletal pain. Future studies could plan training strategies aimed at preventing musculoskeletal pain associated with gymnastics, in order to promote its further spread

The first high-density sequence characterized SNP-based linkage map of olive (Olea europaea L. subsp. europaea) developed using genotyping by sequencing

A number of linkage maps have been previously developed in olive; however, these are mostly composed of markers that have not been characterized at the sequence level, supplemented with smaller numbers of microsatellite markers. In this investigation, we sought to develop a saturated linkage mapping resource for olive composed entirely of sequence characterized markers. We employed genotyping by sequencing to develop a map of a F2 population derived from the selfing of the cultivar Koroneiki. The linkage map contained a total of 23 linkage groups comprised of 1,597 tagged SNP markers in 636 mapping bins spanning a genetic distance of 1189.7 cM. An additional 6,658 segregating SNPs were associated with the 23 linkage groups identified but their marker order was not determined in this investigation. The SNP markers sequences were submitted to NCBI database. The linkage map produced will be an invaluable resource for the study of tree habit and vigour traits segregating in the progeny, and will assist to anchor and orientate sequencing scaffolds from future genome sequencing efforts

Algerian Olive Germplasm and Its Relationships with the Central-Western Mediterranean Varieties Contributes to Clarify Cultivated Olive Diversification

Olive tree with its main final product, olive oil, is an important element of Mediterranean history, considered the emblematic fruit of a civilization. Despite its wide diffusion and economic and cultural importance, its evolutionary and phylogenetic history is still difficult to clarify. As part of the Mediterranean basin, Algeria was indicated as a secondary diversification center. However, genetic characterization studies from Maghreb area, are currently underrepresented. In this context, we characterized 119 endemic Algerian accessions by using 12 microsatellite markers with the main goal to evaluate the genetic diversity and population structure. In order to provide new insights about the history of olive diversification events in the Central-Western Mediterranean basin, we included and analyzed a sample of 103 Italian accessions from Sicily and, a set of molecular profiles of cultivars from the Central-Western Mediterranean area. The phylogenetic investigation let us to evaluate genetic relationships among Central-Mediterranean basin olive germplasm, highlight new synonymy cases to support the importance of vegetative propagation in the cultivated olive diffusion and consolidate the hypothesis of more recent admixture events occurrence. This work provided new information about Algerian germplasm biodiversity and contributed to clarify olive diversification process