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Development of Concentrating Solar Power (CSP) systems has started about 40 years ago. A first commercial implementation was performed between 1985 and 1991 in California. However, a drop in gas prices caused a longer period without further deployment. It was overcome in 2007 when new incentive schemes for renewables in Spain and the US enabled a commercial restart. In 2017, almost 100 commercial CSP plants with more than 5 GW are installed worldwide. This paper describes the physical background of CSP technology, its technical characteristics and concepts. Furthermore, it discusses system performances, cost structures and the expected advancement.

Development of Concentrating Solar Power Systems has started about 40 years ago. A first commercial implementation was performed between 1985 and 1991 in California. However, a drop in gas prices caused a longer period without further deployment. It was overcome in 2007 when new incentive schemes for renewables in Spain and the US enabled a commercial restart. In 2016, almost 100 commercial CSP plants with more than 5GW are installed worldwide. This paper describes the physical background of CSP technology, its technical characteristics and concepts. Furthermore, it discusses system performances, cost structures and the expected advancement.

A completely new ray tracing software has been developed at the German Aerospace Center The main purpose of this software is the flux density simulation of heliostat fields with a very high accuracy in a small amount of computation time. The software is primarily designed to process real sun shape distributions and real highly resolved heliostat geometry data, which means a clam set of normal vectors of the entire reflecting surface of each heliostat in the field. Specific receiver and secondary concentrator models, as well as models of objects that are shadowing the heliostat field, can be implemented by the user and be linked to the simulation software subsequently. The specific architecture of the software enables the provision of other powerful simulation environments with precise flux density simulation data for the purpose of entire plant simulations. The software was validated through a severe comparison with measured flux density distributions. The simulation results show very good accordance with the measured results. [DOI: 10.1115/1.3139139]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2005.11.006 Byline: M. Becker (a), Th. Fend (a), B. Hoffschmidt (b), R. Pitz-Paal (a), O. Reutter (a), V. Stamatov (c), M. Steven (c), D. Trimis (c) Keywords: Volumetric receiver; Flow instabilities; Solar tower technology Abstract: This article reports results of a theoretical analysis as well as a numerical study investigating the occurrence of flow instabilities in porous materials applied as volumetric solar receivers. After a short introduction into the technology of volumetric solar receivers, which are aimed to supply heat for a steam turbine process to generate electricity, the general requirements of materials applied as solar volumetric receivers are reviewed. Finally, the main methods and results of the two studies are reported. In the theoretical analysis it is shown that heat conductivity as well as permeability properties of the porous materials have significant influence on the probability of the occurrence of flow instabilities. The numerical study has been performed to investigate the occurrence of unstable flow in heated ceramic foam materials. In the simulations a constant heat flow of radiation, that is absorbed in a defined volume, and constant permeability coefficients are assumed. Boundary conditions similar to those of the 10MW Solucar Solar project have been chosen. In a three dimensional, heterogeneous two phase heat transfer model it was possible to simulate local overheating of the porous structure. The parameters heat conductivity, turbulent permeability coefficient and radial dispersion coefficient have been varied systematically. Consequently, for a heat flux density of 1MW/m.sup.2 a parameter chart could be generated, showing the possible occurrence of 'unstable' or 'stable' thermal and fluid mechanical behaviour. These numerical results are beneficial for the design of optimized materials for volumetric receivers. Author Affiliation: (a) Institute of Technical Thermodynamics, German Aerospace Center, Linder Hohe, D-51147 Koln, Germany (b) Solar-Institut Julich, Heinrich-MuAmann-Str. 5, 52428 Julich, Germany (c) Institute of Fluid Mechanics, Friedrich-Alexander University Erlangen-Nuremberg, Cauerstr. 4, D-91058 Erlangen, Germany Article History: Received 26 August 2005; Revised 30 September 2005; Accepted 22 November 2005 Article Note: (miscellaneous) Communicated by: Associate Editor Carlos Ramos Berumen

Numerical results found in the literature predict the capability of volumetric receivers to produce gas outlet temperatures of more than 1000 [degrees] C. Other approaches found the tendency for an inherent flow instability for volumetric absorbers at high outlet temperatures. Both aspects, which are based on one-dimensional approaches, do not fit the experimental experience available even for semi-commercial volumetric receivers in the case of non-homogeneous flux distribution. Since this is the general case in solar power plants, a new analytical approach which takes into consideration a three-dimensional irradiance distribution and its influence on fluid flow and radial heat transfer is presented in this article. A comparison with experimental data for four totally different volumetric absorber types coincides well with the measured overall thermal efficiency as well as with the local temperature distribution. The model helps to explain how thermal efficiencies and temperature distributions are strongly influenced by non-homogeneous irradiation. Moreover, it demonstrates how flow instabilities are partly prevented by radial heat transfer. Finally, it is shown that a volumetric receiver consisting of sufficiently small absorber modules which are equipped with an additional orifice plate at the rear side will always run under stable flow conditions.

Concentrating solar power (CSP) is a commercially available renewable energy technology capable of harnessing the immense solar resource in Southern Europe, the Middle East and North Africa (the MENA region), and elsewhere. This paper summarises the findings of a study by the European Academies Science Advisory Council which has examined the current status and development challenges of CSP, and consequently has evaluated the potential contribution of CSP in Europe and the MENA region to 2050. It identifies the actions that will be required by scientists, engineers, policy makers, politicians, business and investors alike, to enable this vast solar resource to make a major contribution to establishing a sustainable energy system. The study concludes that cost reductions of 50-60% in CSP electricity may reasonably be expected in the next 10-15 years, enabling the technology to be cost competitive with fossil-fired power generation at some point between 2020 and 2030. Incorporation of storage delivers added value in enabling CSP to deliver dispatchable power. Incentive schemes will be needed in Europe and MENA countries to enable this point to be achieved. Such schemes should reflect the true value of electricity to the grid, effectively drive R&D, and ensure transparency of performance and cost data.