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A stochastic optimisation method adapted to illumination and radiative heat transfer problems involving Monte-Carlo ray-tracing is presented. A solar receiver shape optimisation case study illustrates the advantages of the method and its potential: efficient receivers are identified using a moderate computational cost.

As an alternative to conventional tracking solar thermal trough systems, one may use line focus Fresnel reflector systems. In a conventional Fresnel reflector design, each field of reflectors is directed to a single tower. However, efficient systems of very high ground utilisation can be setup if a field of reflectors uses multiple receivers on different towers. This paper describes a line focus system, called the compact linear fresnel reflector system and a project to produce an initial 95 MWth solar array. The array will be used as a retrofit preheater for a coal fired generating plant.

In this study, eleven mathematical models estimating the minimum possible atmospheric dilution of rooftop exhaust gases around buildings are evaluated and reviewed using data obtained from 72 full-scale tracer tests at two buildings. Quantities measured were the stack height, stack-to-intake distance, stack diameter, wind speed and direction, exhaust flux, and the stack-to-intake dilution. These models are all based on wind-tunnel simulations and are designed to account for a worst-case scenario so that they can be used to provide a conservative safeguard for design of new stacks or for modification purposes. Although none of the models gave outstanding performance relative to the others, Halitsky’s model, derived from the prism tests and Clinical Center data incorporating the exhaust momentum ratio, gave particularly good predictions. Further, all models led to very conservative estimates of the dilution in the case of gases exhausted close to a receptor, suggesting that the models reviewed here...

This paper presents experimental evaluation of ammonia receiver geometries with a 9 m2 dish concentrator. The experiments involved varying the geometric arrangement of reactor tubes in a thermochemical reactor built from a series of tubes arranged in a conical shape inside a cavity receiver. Differences in conical arrangement were found to affect the efficiency of energy conversion. The solar-to-chemical efficiency gain obtained by varying the receiver geometry was up to 7% absolute. From this, it is apparent that geometric optimizations are worth pursuing since the resulting efficiency gains are achieved with no increase in costs of manufacture for receivers. The experimental results and methodology can be used when developing receivers for larger dish concentrators, such as the second generation 500 m2 dish concentrator developed at the Australian National University.

This chapter provides an overview of the fundamental principles of CSP systems. It begins with the optical processes and the ultimate limits on the extent to which solar radiation can be concentrated. Practical factors that reduce achievable concentration levels further are discussed. Mechanisms of thermal energy loss from receivers are covered. Available power cycles for electricity generation are reviewed. The second law of thermodynamics is introduced to lead into a consideration of optimization of overall system efficiency via variation of operating temperature and receiver aperture size. Performance modelling of complete systems is introduced and finally the analysis of levelized cost of energy is covered, as a metric for comparing systems, and as a tool to thermo-economic optimization in design.

In open cavity receivers employed in solar paraboloidal dish applications, natural convection occurs and contributes a significant fraction of energy loss. Its characteristics hence need to be clarified so that it can be effectively minimized in order to improve the system efficiency. The investigation of natural convection loss from cavity receivers was undertaken numerically and was validated using the published experimental results for four different receiver geometries. A good agreement between experimental and numerical results was obtained. Furthermore, the numerical results of all receivers were qualitatively comparable to the predictions by other available correlations hitherto, although it was found that each correlation has a limited range of applicability arising from the particular cavity geometry and experimental conditions used to derive it. To address this shortcoming, a new correlation based on the numerical results for three of the above four receivers has been proposed. The correlation employs a new concept of an ensemble cavity length scale, to take into account the combined effects of cavity geometry and inclination. Despite a wide variety of cavity geometries and operating conditions, the proposed correlation predicts approximately 50% of the data within ±20% and 90% of the data within ±50%. This is better than any of the other correlations published to date. The new correlation is also simpler to use than the most accurate of those previously published.

89Sr treatment was used to determine if stem cells in young fetal liver could differentiate to mature B lymphocytes in adult animals that lacked functional bone marrow. Isotope injection alone resulted in a severe and lasting depletion of bone marrow cells and particularly lymphocytes, multipotential stem cells, and progenitors for granulocytes and macrophages. The latter two functional populations of cells expanded in number in the spleen but not the liver after their destruction in bone marrow. The total body content of stem cells did not, however, return to normal. Spleen B cells and lymphocytes lacking B or T cell markers were reduced by 89Sr treatment and possible reasons for this depletion are discussed. B lymphocytes were formed in lethally x-irradiated mice that had less than 1% of normal bone marrow function after reconstitution with fetal liver cells. These cells were immunologically mature by virtue of their ability to mount a primary immune response and function in a thymus-independent adoptive anti-hapten response.

By using a two-stage optimisation process we maximise the heat rate output of afour-parameter axisymmetric direct steam generation cavity receiver. The model includes radiative and hydrodynamic considerations. We show that a significant range of geometrical shapes show similar efficiencies while having different wall flux and temperature profiles.

This study examines experimentally the heat loss from a model solar cavity receiver. For this purpose, laboratory-scale cylindrical cavity models with geometric aspect ratios (cavity length to diameter) of 1 and 2, and aperture opening ratios(aperture diameter to cavity diameter) of 0.5 and 1, were built. Each cavitywas subjected to constant boundary heat inputvia heating cables, and was operated at various downward inclinations. A carefully-applied coating of Pyromark-2500 heat resistant paint on the cavity surface, in conjunction with steady-state experimental temperatures, enabled accurate calculation of the radiative loss from the cavities. The experimental technique allowed precise control of the operating parameters, resulting in determination of the conduction loss, and subsequently, the convection heat loss.Operation at temperatures up to 650 o C allowed for a better understanding of the interaction between radiation and convection heat loss mechanisms. Experimental data obtained in this study are shown to be consistent with the concept of stagnation and convection zone development in cavities, with increasing cavity inclination angle. A qualitative assessment of the impact of these zones on the cavity surface temperatures is presented. Whereas thermocouples located in stagnation region show uniform temperature distribution, the surfaces which are exposed to convective flows exhibit larger temperature variations. The temperature distribution along the cavitywalls and its effect on radiative loss calculation is also investigated in this work. It is seen that radiative loss predictions which consider an average cavity temperature in their model can overestimate the losses due to this mechanism by up to 20%, in comparison to models which use experimental temperatures along the cavity interior. Convection loss from the cavity is calculated and compared with results from correlations proposed in the literature.It is seen that correlations based on surface areas of the stagnation and convection zones are better at predicting the experimental results.

Preprint of the article published in the ASME Journal of Solar Energy Engineering with the same title and the following DOI: 10.1115/1.4051315&nbsp

We perform optical analyses on multi-aperture solar central receiver systems with compound parabolic concentrators to increase the power level for better economics.

We present a numerical function for approximating shading losses around two-axis tracking solar collectors. It is used in a gradient descent algorithm to optimise relative collector position. System yield is increased by 1% - 2%

Optics, thermal emissions, convection and internal flow are treated in a unified model for a tubular cavity receiver for a dish concentrator; a new design is presented that shows a 40% reduction in receiver losses.

BRISBANE, Australia (AP) ” Ellis Genge set the tone when he bumped off Australia skipper Michael Hooper™s attempted tackle in the first minute and Owen Farrell kicked 20 points as England held on for a 25-17 win Saturday to ensure the three-test series will be decided next weekend.Stunned by a 30-28 loss in Perth last week, ending its eight-test winning streak against Australia, England opened the second test in Brisbane with an intensity that rattled the home team and raced to a 19-0 lead. [ABSTRACT FROM PUBLISHER]

BRISBANE, Australia (AP) ” Shakib Al Hasan and his Bangladesh players hugged, traded high-fives, and shook hands with their Zimbabwe rivals as they walked off the field Sunday to celebrate what they thought was a narrow Super 12 win in the Twenty20 World Cup.Back-to-back stumpings by wicketkeeper Nurul Hasan on the last two balls from Musaddek Hossain seemed to do the trick, dismissing two of Zimbabwe's tail-end batters who'd needed five runs off the last two balls for victory. [ABSTRACT FROM PUBLISHER]

BRISBANE, Australia (AP) ” Travis Head defied the hostile pitch conditions to produce a run-a-ball 78 that moved Australia to within seven runs of South Africa™s first innings Saturday, when 15 wickets fell on the opening day of the three-test series.Head™s unbeaten innings containing 13 boundaries and a six and his 117-run partnership with Steve Smith (38) helped justify Pat Cummins™ gamble to bowl first after winning the toss. It was also pivotal in helping Australia reach 145-5 at stumps on Day 1, trailing South Africa by seven runs with five wickets still in hand. [ABSTRACT FROM PUBLISHER]

BRISBANE, Australia (AP) ” Travis Head defied the hostile pitch conditions to produce a run-a-ball 78 that moved Australia to within seven runs of South Africa™s first innings Saturday, when 15 wickets fell on the opening day of the three-test series.Head™s unbeaten innings containing 13 boundaries and a six and his 117-run partnership with Steve Smith (38) helped justify Pat Cummins™ gamble to bowl first after winning the toss. Australia was 145-5 at stumps. [ABSTRACT FROM PUBLISHER]

There was a big song and dance about how Australia scraped into the World Cup. A so-called Wiggles dance made replacement goalkeeper Andrew Redmayne a public enemy in Peru, with his flailing arms and legs as he prepared to make saves in the penalty shootout becoming a meme as the Socceroos secured one of the last spots in Qatar. [ABSTRACT FROM PUBLISHER]