Review of heliostat calibration and tracking control methods

Large scale central receiver systems typically deploy between thousands to more than a hundred thousand heliostats. During solar operation, each heliostat is aligned individually in such a way that the overall surface normal bisects the angle between the sun’s position and the aim point coordinate on the receiver. Due to various tracking error sources, achieving accurate alignment ≤1 mrad for all the heliostats with respect to the aim points on the receiver without a calibration system can be regarded as unrealistic. Therefore, a calibration system is necessary not only to improve the aiming accuracy for achieving desired flux distributions but also to reduce or eliminate spillage. An overview of current larger-scale central receiver systems (CRS), tracking error sources and the basic requirements of an ideal calibration system is presented. Leading up to the main topic, a description of general and specific terms on the topics heliostat calibration and tracking control clarifies the terminology used in this work. Various figures illustrate the signal flows along various typical components as well as the corresponding monitoring or measuring devices that indicate or measure along the signal (or effect) chain. The numerous calibration systems are described in detail and classified in groups. Two tables allow the juxtaposition of the calibration methods for a better comparison. In an assessment, the advantages and disadvantages of individual calibration methods are presented

Building Tomograph – From Remote Sensing Data of Existing Buildings to Building Energy Simulation Input

Existing buildings often have low energy efficiency standards. For the preparation of retrofits, reliable high-quality data about the status quo is required. However, state-of-the-art analysis methods mainly rely on on-site inspections by experts and hence tend to be cost-intensive. In addition, some of the necessary devices need to be installed inside the buildings. As a consequence, owners hesitate to obtain sufficient information about potential refurbishment measures for their houses and underestimate possible savings. Remote sensing measurement technologies have the potential to provide an easy-to-use and automatable way to energetically analyze existing buildings objectively. To prepare an energetic simulation of the status quo and of possible retrofit scenarios, remote sensing data from different data sources have to be merged and combined with additional knowledge about the building. This contribution presents the current state of a project on the development of new and the optimization of conventional data acquisition methods for the energetic analysis of existing buildings solely based on contactless measurements, general information about the building, and data that residents can obtain with little effort. For the example of a single-family house in Morschenich, Germany, geometrical, semantical, and physical information are derived from photogrammetry and quantitative infrared measurements. Both are performed with the help of unmanned aerial vehicles (UAVs) and are compared to conventional methods for energy efficiency analysis regarding accuracy of and necessary effort for input data for building energy simulation. The concept of an object-oriented building model for measurement data processing is presented. Furthermore, an outlook is given on the project involving advanced remote sensing techniques such as ultrasound and microwave radar application for the measurement of additional energetic building parameters

The solar power tower Jülich – a solar thermal power plant for test and demonstration of air receiver

The paper explains the fundamentals of the open volumetric receiver technology and shows the history of its development. It gives technical information about the system definition and the engineering of the Solar Power Tower Jülich. The open volumetric receiver technology allows the use of air as heat transfer medium at high temperatures in solar thermal power tower plants. It combines porous ceramic or metallic absorber structures with a strictly modular receiver design. Highly concentrated solar radiation is used to produce hot air as ‘firing’ for a steam rankine cycle. The advantages of this technology are simplicity and scalability, the ability to include a thermal storage, the low thermal capacity and a high efficiency potential. This receiver technology was developed in various joint projects of research and industry over the past years. It was tested and qualified in the worlds largest test center for concentrating solar power, the Plataforma Solar de Almería (PSA) in Southern Spain with a nominal power of 3 MW incident radiation. In June 2006 it was decided to build a tower power plant with thermal storage in Jülich, Germany, with a design power of 1,5 MWe. The objectives of this plant are to test and demonstrate the solar air technology as a complete system, to develop control and plant management strategies and to improve the overall performance and reliability. The location in Germany was chosen as it is close to the research institutions involved and it allows the investigation of the system performance under fluctuating irradiation conditions. The Solar Power Tower Jülich is scheduled to start operation by the end of 2008. The five year project comprises design, construction and a two year test operation phase, accompanied by an intensive R&D program. The experiences of this project will be a vital step towards a successful market introduction

A CPS-Based Simulation Platform for Long Production Factories

Production technology in European steel industry has reached such a level, that significant improvements can only be reached by through process optimization strategies instead of separately improving each process step. Therefore, the connection of suitable technological models to describe process and product behavior, methods to find solutions for typical multi-criterial decisions, and a strong communication between involved plants is necessary. In this work, a virtual simulation platform for the design of cyber-physical production optimization systems for long production facilities focusing on thermal evolution and related material quality is presented. Models for describing physical processes, computers, software and networks as well as methods and algorithms for through process optimization were implemented and merged into a new and comprehensive model-based software architecture. Object-oriented languages are addressed and used because they provide modularity, a high-level of abstraction and constructs that allow direct implementation and usage of the cyber-physical production systems concepts. Simulation results show how the proper connection between models, communication, and optimization methods allows feasibility, safety and benefits of cyber-physical production systems to be established. Furthermore, the software architecture is flexible and general and thus, can be transferred to any steel production line as well as outside the steel industry

Development of a 30m² Heliostat with Hydraulic Drive

Reliable and cost-effective heliostats with high accuracy are a prerequisite for the successful market introduction of solar tower systems. The advantages of hydraulic drives are high positioning precision, no backlash, ability to go to stow position at electrical power loss and optional overload protection. Initial cost calculations indicated that a cost-competitive solution could be provided. The design of a heliostat with 30m² mirror area is described. The oil reservoir with pump, the valve bloc and the cylinders for the azimuth drive are located in the cross bar. The results of wind tunnel measurements with heliostat models of various aspect ratios led to an aspect ratio of 1.2. A wind fence was not assumed because in the rear part of usual heliostat fields it has no significant advantage as wind tunnel measurements showed. For the canting an automatic procedure will be applied at which the deflectometry method is used for the determination of the shape and orientation of the mirror facets. The first six prototypes will be erected at the Jülich solar tower site, Germany and one at the Plataforma Solar de Almeria, Spain. Extensive testing will be carried out to verify the design goals with respect to mechanical properties, optical performance, system functionality and power consumption. Based on the results a cost-benefit-based optimization of the construction and the drives will be carried out

Algen für die Abwasserbehandlung und ihre Verwendung in der Düngemittelproduktion

Abwässer aus Kläranlagen und (Lebensmittel-) Industrie enthalten unterschiedliche Konzentrationen von Mineralie, bspw. Stickstoff und Phosphat, die für das Pflanzenwachstum esentiel sind. Wenn diese Abwässer in die Umwelt gelangen, können sie Grund- und Oberflächengewässer verunreinigen. Algen sind effizient bei der Entfernung von Nährstoffen aus dem Wasser. Im Rahmen des Projektes "AlgaeSolarBoxes" konstruieren wir (IBG-2 und SIJ) ein mobiles System mit (i) einem Photobioreaktor zur Reinigung der Abwässer durch Algen, (ii) einem Spiegelsystem zur Versorgung des Photobioreaktors mit sichtbarem Sonnen- und LED-Licht und (iii) einem Infrarot-Photovoltaik Modul zur Erzeugung von Strom aus dem nicht für die Photosynthese verwertbaren Infrarotanteil des Sonnenlichts. Das System wird zur Wasseraufbereitung an Kläranlagen und (Lebensmittel-) Industrie verwendet werden können. Das mobile System wird sich vor allem für saisonal anfallende Abwässer mit geringen Verunreinigungen (bspw. Lebensmittelindustrie) eignen können

Algenbasierte Kreiswirtschaft mittels AlgaeFertilizerBox

Intensive Landwirtschaft aber auch Anwohner und Industrie belasten die Oberflä-chen- und Grundgewässer mit Nährstoffen (Landesamt für Natur, Umwelt und Ver-braucherschutz NRW, 2014). Die Nährstoffanreicherung in Oberflächengewässern (Eutrophierung) äußert sich in Abhängigkeit vom Schweregrad durch Algenblüten. Algen haben eine hohe Kapazität für die Phosphataufnahme und können im Idealfall bis zu 90% des Phosphats aus dem Abwasser entfernen (Solovchenko et al., 2016). Diese Fähigkeit der Algen wird im Projekt AlgaeFertilizerBoxes genutzt, um einen Demonstrator zur Wasseraufbereitung mittels Algen zu entwickeln.Das System wird aus zwei Modulen bestehen: i. Algen Modul und einem Spektral Modul. Dieses besteht aus einer flachen, geneigten (0,5-2% Gefälle) und freiliegen-den Oberfläche mit gepulstem Wasserfluss (Calahan et al., 2018). Hier bildet sich ein schnellwachsender, benthischer Biofilm aus überwiegend filamentösen Algen (Sala-ma et al., 2017, Calahan et al., 2018). Der Biofilm kann aus über 100 Algenspezies bestehen, ist gegenüber Umwelteinflüssen sehr robust (Kangas et al., 2017) und zeigt eine überwiegend gleichbleibende Funktionalität (Calahan et al., 2018). Im Ge-gensatz zur üblichen, energieaufwendigen Algenbiomasseernteverfahren durch Zent-rifugation, wird der Biofilm aus dem ATS-System durch Schrubben (scrubbing) ge-erntet. Unter kontrollierten Bedingungen entfernte das ATS-System bereits nach 24 Stunden bis zu 70% der Nitrate und 80% der Phosphate aus der Nährlösung. Der Biofilm ist photoautotroph und wird mit Licht der Sonneneinstrahlung und LED-Beleuchtung versorgt. Die Konzentration der Sonnenstrahlung wird mit einem mehr-stufigen Lichtsammel- und -lenksystem aus Mikroheliostat Boxen (Synhelion GmbH, Bergisch Gladbach, Deutschland) und einem linearen Spiegel zur Lenkung der Son-nenstrahlung in den Container erreicht. Das Spiegelsystem wird sich auf dem Dach des Containers befinden, um den Demonstrator möglichst kompakt zu halten. Da derBiofilm nur das sichtbare Licht für die Photosynthese nutzen kann (Nwoba et al., 2019), wird der Infrarotanteil mittels einer spektral selektiven Folie ausgekoppelt um die Überhitzung des Photobioreaktors zu verhindern. Die ausgekoppelte Infrarot-strahlung wird zur Stromerzeugung im Infrarot-Photovoltaik Modul genutzt. Abschlie-ßend wird das sichtbare Licht mit Hilfe eines Spiegelsystems im Photobioreaktor ver-teilt. Zusätzlich wird der Photobioreaktor mit LEDs ausgestattet, um den Demonstra-tor von Wetter- und Jahresbedingungen unabhängig zu machen. Darüber hinaus werden die LEDs einen Dauerbetrieb (24/7) des Demonstrators ermöglichen. Die Algen und Spektral Module werden in einen 20-Fuß-ISO-Container integriert, um die Mobilität des Systems zu gewährleisten.Die ATS-Biofilme wurden auf Nährstoffzusammensetzungen untersucht. Aus der Perspektive der Nährstoffzusammensetzungen sind diese als Stickstoff/ Phosphat Dünger (NP-Dünger) geeignet. Die Untersuchungen zur Nutzung des Biofilms als Dünger für Weizen sind in der Durchführung

Net-exergetic, hydraulic and thermal optimization of coaxial heat exchangers using fixed flow conditions instead of fixed flow rates

<jats:title>Abstract</jats:title><jats:p>Previous studies optimized the dimensions of coaxial heat exchangers using constant mass flow rates as a boundary condition. They show a thermal optimal circular ring width of nearly zero. Hydraulically optimal is an inner to outer pipe radius ratio of 0.65 for turbulent and 0.68 for laminar flow types. In contrast, in this study, flow conditions in the circular ring are kept constant (a set of fixed Reynolds numbers) during optimization. This approach ensures fixed flow conditions and prevents inappropriately high or low mass flow rates. The optimization is carried out for three objectives: Maximum energy gain, minimum hydraulic effort and eventually optimum net-exergy balance. The optimization changes the inner pipe radius and mass flow rate but not the Reynolds number of the circular ring. The thermal calculations base on Hellström’s borehole resistance and the hydraulic optimization on individually calculated linear loss of head coefficients. Increasing the inner pipe radius results in decreased hydraulic losses in the inner pipe but increased losses in the circular ring. The net-exergy difference is a key performance indicator and combines thermal and hydraulic calculations. It is the difference between thermal exergy flux and hydraulic effort. The Reynolds number in the circular ring is instead of the mass flow rate constant during all optimizations. The result from a thermal perspective is an optimal width of the circular ring of nearly zero. The hydraulically optimal inner pipe radius is 54% of the outer pipe radius for laminar flow and 60% for turbulent flow scenarios. Net-exergetic optimization shows a predominant influence of hydraulic losses, especially for small temperature gains. The exact result depends on the earth’s thermal properties and the flow type. Conclusively, coaxial geothermal probes’ design should focus on the hydraulic optimum and take the thermal optimum as a secondary criterion due to the dominating hydraulics.</jats:p&gt

Net-exergetic, hydraulic and thermal optimization of coaxial heat exchangers using fixed flow conditions instead of fixed flow rates

O estudo teve como objetivo analisar o desempenho dos serviços de saúde que executam a Terapia Diretamente Observada (DOT) no domicílio para o controle da tuberculose. Foram estudados quatro Programas de Controle da Tuberculose nomeados como A, B, C e D a partir dos seguintes indicadores: aproveitamento dos recursos; agilidade do desempenho; monitoração da administração da medicação; tempo gasto por visita domiciliar. Os dados foram coletados durante a visita a 47 doentes em DOT no domicílio. Observou-se que o aproveitamento dos recursos foi maior no programa B (91,3%); maior agilidade (5,8) e maior porcentagem de visitas com monitoração da administração da medicação (77,4%) no programa A; maior tempo gasto por visita no programa C (14,7 minutos) e menor no programa A (10,4 minutos). O maior ou menor desempenho expressa numericamente a forma como os recursos estão sendo utilizados e se a observação da ingestão medicamentosa está sendo alcançada.La finalidad del estudio fue analizar el desempeño de los servicios de salud que brindan Tratamientos por observación en domicilio para el control de la tuberculosis. Se estudiaron cuatro Programas de Controle da Tuberculosis identificados como A, B, C y D a partir de los indicadores de Aprovechamiento de recursos; Agilidad en el desempeño; Supervisión de la administración del medicamento y Tiempo utilizado por visita domiciliaria. Los datos fueron recolectados durante la visita a 47 enfermos. Se observó que el aprovechamiento de recursos fue mayor en el programa B (91,3%); en el programa A fue observada mayor agilidad (5,8) y mayor porcentaje de visitas con supervisión en la administración del medicamento (77,4%); en el programa C fue mayor el tiempo utilizado por visita (14,7 minutos), siendo este menor para el programa A (10,4 minutos). El mayor o menor desempeño expresa numéricamente la forma cómo los recursos están siendo utilizados, así como el alcance de las metas al respecto de la observación durante la ingestión de medicamentos.The study had the objective to analyze the performance of the health services that implement the Directly Observed Therapy at home for tuberculosis control. This study analyzed four Tuberculosis Control Programs, referred to as A, B, C, and D, using the following indicators: Resource use; Performance quickness; Monitoring medication administration; Time spent per home visit. Data were collected during visits to 47 patients receiving DOT at home. Resource use was higher in program B (91.3%); program A showed quicker performance (5.8) and more visits during which medication administration was monitored (77.4%); program C had the longest time spent per home visit (14.7 minutes) and program A the shortest (10.4 minutes). The best or worst performance numerically expresses how resources are being used and whether the observation of medication intake is being achieved

AIR-SAND HEAT EXCHANGER: MATERIALS AND FLOW PROPERTIES

In this paper, detailed analyses of some bulk materials and their flow properties related with the operation with porous heat exchanger wall types are presented. A focus is on granular media and their properties. Investigations with respect to attrition and abrasion have been performed to identify the most suitable granular product in combination with different wall materials. Tested products are alumina grinding balls, sintered bauxite, fused silica and silicon carbide on the ceramic side, quartz sand and flints, basalt and normal corundum on the natural products side