Dynamic Simulation of a solar tower system with open volumetic receiver - a review on the vICERP project

The paper presents an overview on the modeling and simulation activities of the virtual institute for central receiver power plants (vICERP). Within a three years launch period models and tools for dynamic simulation of central receiver power plants have been developed by the five research institutes involved. The models are based on the Modelica modeling language. Today, models for the heliostat field, the receiver, the air cycle, the thermal storage, and the water-steam cycle are available within the consortium. As a first application, the Solar Tower Jülich technology was used as a reference. Models are validated with real operational data from the Solar Tower Jülich

Modellgestützte Bewertung und Optimierung der offenen Luftreceivertechnologie

Die offene Luftreceivertechnologie wird in solarthermischen Turmkraftwerken zur Absorption und zur Umwandlung der vom Heliostatenfeld eingestrahlten Energie eingesetzt. Nach der erfolgreichen Demonstration der Technologie im Versuchs- und Demonstrationskraftwerk Solarturm Jülich sollen zukünftig größere kommerzielle Kraftwerkseinheiten realisiert werden. In diesem Zusammenhang ist es das Ziel dieser Arbeit, ein adäquates Modell der Receivertechnologie zur modellgestützten Bewertung und Optimierung der Einflussmöglichkeiten der Receiverauslegung und des Receiverbetriebs zu entwickeln. Der maximierte Luftmassenstrom des Receivers wird dabei als primäres Bewertungskriterium eingesetzt. Es wird daher neben dem Modell auch eine Methode entwickelt, die den Luftmassenstrom des Receivers unter Verwendung der gegebenen Einflussmöglichkeiten maximiert. Die Einflussmöglichkeiten der Receiverauslegung und des Receiverbetriebs, inklusive Zielpunktoptimierung und Luftmassenstromoptimierung, werden am Beispiel eines Kraftwerks in kommerzieller Größe bewertet. Daneben werden vielversprechende Verbesserungsoptionen der Receivertechnologie untersucht, um den Umwandlungswirkungsgrad des Receivers zu verbessern und das Potential der Receivertechnologie abzuschätzen. The open volumetric air receiver technology is a key component of solar thermal power plants to absorb and convert the irradiated solar power. Based on the successful demonstration of open volumetric air receiver technology at the Solar Tower Jülich the strategic focus will be on perspective large commercial power plant projects. In this context it is the goal of this work to develop an adequate model of the receiver technology for a model based evaluation and optimization of options regarding dimensioning of key components of the receiver and receiver operation. The maximized air flow rate at the receiver outlet is used as the primary rating criteria. Thus, besides a model also a method is developed to maximize the mass flow rate of the receiver taking the prevailing dimensioning and operational options of the receiver into account. The prevailing options of the receiver during design and operation, e.g. aim point optimization or the optimization of the mass flow rate distribution, are demonstrated using a test case for an solar thermal power plant with open volumetric air receiver technology in a commercial scale. Furthermore, promising improvements of the receiver technology are analyzed to boost the receiver conversion efficiency and to estimate the potential of the contemplated receiver technology

Betriebsoptimierung von Turmkraftwerken: Optimierung der Heliostatzielpunkte unter Berücksichtigung des thermischen Receiververhaltens

Im Bereich der Solarforschung des DLR in Köln werden zur Analyse und Optimierung von solarthermischen Turmkraftwerken Softwarewerkzeuge entwickelt. Eine wichtige Optimierungsfrage ist die Wahl der Heliostatzielpunkte auf dem Receiver. Anhand von realistischen Simulationsszenarien wird der Einfluss der Zielpunktkonfiguration auf das Leistungsverhalten eines offenen volumetrischen Receivers untersucht

TRANSIENT SIMULATION OF SOLAR TOWER POWER PLANT WITH OPEN VOLUMETRIC AIR RECEIVER

The start up of the PS 10 power plant in Seville, Spain, in 2007 marked the entrance of solar power tower plants into the commercial state. Questions about the right operational strategy, particularly during unsteady operation states, come to the fore, and therewith the need to carry out transient simulations of entire power tower plants including the heliostat field. Meeting this necessity the presented simulation approach opens the way to transient full plant simulations of solar power tower plants. A detailed heliostat field model was linked to a dynamic receiver model by coupling both simulation tools. A second coupling was established to a tool hosting a control panel of the heliostat field model. With this simulation approach a startup procedure and a tracking stop were simulated delivering different transient behaviors of local absorber temperatures and mass flows

Modeling and Simulation of a Solar Tower Power Plant with Open Volumetric Air Receiver

The start-up of the PS10 power plant in Seville, Spain, in 2007 marked the entrance of solar tower power plants into the commercial state. Questions about the right operational strategy, particularly during unsteady operation states, come to the fore, and therewith the need to carry out transient simulations of entire tower power plants including the heliostat field. Meeting this necessity, the presented simulation approach opens the way to transient full plant simulations of solar tower power plants. A detailed heliostat field model was linked to a dynamic receiver model by coupling both simulation tools. A second coupling was established to a tool hosting a control panel of the heliostat field model. With this simulation approach, a start-up procedure and a tracking stop were simulated delivering different transient behaviors of local absorber temperatures and mass flows

a low-cost dynamic shadow detection system for site evaluation

Partial shadowing caused by moving clouds results in spatially and timely alternating supply of direct irradiation to large solar collector fields with extensions of 1 km² and more. Fluctuating inhomogeneous irradiation may lead to harmful dynamic changes of load and temperature in various components of CSP plants. In order to avoid harmful wear and stress the power stations have to be shut down under these weather conditions and production capacity is lost. On the other hand, operation and control strategies for continuous plant operation can be developed with dynamic simulation when appropriate data is available. The paper gives an overview on existing cloud and shadow detection methods and presents a new system for dynamic cloud detection based on autonomous miniature light sensors. Performance analysis by simulation and laboratory experiment was done and showed the feasibility of the system. The cost of the system is estimated as about 10 k€, independent from the field size. The system is especially applicable for site evaluation as it is completely independent from other installations

Automatic determination of heliostat orientation using an auxiliary mirror

In this paper a new method is presented which can be used to determine the heliostat orientation and improve the tracking accuracy in solar thermal power towers during operation. A small mirror attached to every heliostat, the auxiliary mirror, reflects the sunlight onto the target. The resulting spot is used to determine the orientation of the heliostat, which can be used to adjust the heliostat orientation with respect to the assigned aim point. Tracking accuracy of the heliostats can be improved by applying a correction based on the determined orientation. In the study presented the applied method is described and analyzed in detail. Furthermore, restrictions of the method are discussed. Simulations and a short test performed to evaluate the accuracy are presented

Optimization of the Mass Flow Rate Distribution of an Open Volumetric Air Receiver

The thermodynamical efficiency of a solar power tower power plant with an open volumetric air receiver depends among others on the operational strategy of the receiver. This strategy includes, on the one hand, controlling the distribution of irradiated power on the receiver surface via aim point optimization, and on the other hand, controlling the air mass flow rate and its distribution by choosing suitable dimensions of fixed orifices and controlling air flaps. The maximum mass flow rate of the receiver as an indication of the thermal power is commonly used as a quality function when assessing new component designs, comparing different operational strategies, or evaluating the role of aim point optimization for the open volumetric air receiver technology. In this paper, a method is presented to maximize the mass flow rate of the receiver using given technical capabilities of the receiver technology like orifices and air flaps for a desired air outlet temperature of the receiver. The method is based on dynamic programming, a general technique for solving decision making problems where a complex problem can be split up into a sequence of simpler ones. The potential of the method is demonstrated for a prototype solar thermal power tower with open volumetric air receiver technology.</jats:p