Multi-scale modelling of a large scale shell-and-tube latent heat storage system for direct steam generation power plants

For future parabolic trough plants direct steam generation in the absorber pipes is a promising option for reducing the costs of solar thermal power generation. These new solar thermal power plants require innovative storage concepts, where the two-phase heat transfer fluid poses a major challenge. A three-part storage system is proposed where a phase change material (PCM) storage will be deployed for the two-phase evaporation, while concrete storage will be used for storing sensible heat, i.e., for preheating of water and superheating of steam. A pinch analysis helps to recognize interface constraints imposed by the solar field and the power block and describes a way to dimension the latent and sensible components. Laboratory test results of a PCM test module with ∼140 kgNaNO3, applying the sandwich concept for enhancement of heat transfer, are presented, proving the expected capacity and power density. The concrete storage material for sensible heat was improved to allow the operation up to 500°C for direct steam generation. A storage system with a total storage capacity of ∼1 MWh is described, combining a PCM module and a concrete module, which will be tested in 2009 under real steam conditions around 100 bars.

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Comparative System Analysis of Direct Steam Generation and Synthetic Oil Parabolic Trough Power Plants With Integrated Thermal Storage

ASME 2011 5th International Conference on Energy Sustainability, Parts A, B, and C ◽

10.1115/es2011-54345 ◽

2011 ◽

Author(s):

Jan Fabian Feldhoff ◽

Kai Schmitz ◽

Markus Eck ◽

Lars Schnatbaum-Laumann ◽

Doerte Laing ◽

...

Keyword(s):

Power Plant ◽

Power Plants ◽

System Analysis ◽

Storage System ◽

Steam Generation ◽

Parabolic Trough ◽

Synthetic Oil ◽

Direct Steam ◽

Oil Plant ◽

Steam Parameters

Parabolic trough power plants are currently the most commercially applied systems for CSP power generation. To improve their cost-effectiveness, one focus of industry and research is the development of processes with other heat transfer fluids than the currently used synthetic oil. One option is the utilization of water/steam in the solar field, the so-called direct steam generation (DSG). Several previous studies promoted the economic potential of DSG technology [1–3]. Analyses’ results showed that live steam parameters of up to 500°C and 120 bars are most promising and could lead to a reduction of the levelized electricity cost (LEC) of about 11% [4]. However, all of these studies only considered plants without thermal energy storage (TES). Therefore, a system analysis including integrated TES was performed by Flagsol GmbH and DLR together with Solar Millennium AG, Schott CSP GmbH and Senior Bergho¨fer GmbH, all Germany. Two types of plants are analyzed and compared in detail: a power plant with synthetic oil and a DSG power plant. The design of the synthetic oil plant is very similar to the Spanish Andasol plants [5] and includes a molten salt two-tank storage system. The DSG plant has main steam parameters of 500 °C and 112 bars and uses phase change material (PCM) for the latent and molten salt for the sensible part of the TES system. To enable comparability, both plants share the same gross electric turbine capacity of 100 MWel, the same TES capacity of nine hours of full load equivalent and the same solar multiple of the collector field of about two. This paper describes and compares both plants’ design, performance and investment. Based on these results, the LEC are calculated and the DSG plant’s potential is evaluated. One key finding is that with currently proposed DSG storage costs, the LEC of a DSG plant could be higher than those of a synthetic oil plant. When considering a plant without TES on the other hand, the DSG system could reduce the LEC. This underlines the large influence of TES and the still needed effort in the development of a commercial storage system for DSG.

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Latent Heat Storage for Solar Steam Systems

Journal of Solar Energy Engineering ◽

10.1115/1.2804624 ◽

2007 ◽

Vol 130 (1) ◽

Cited By ~ 81

Author(s):

Wolf-Dieter Steinmann ◽

Rainer Tamme

Keyword(s):

Latent Heat ◽

Power Plants ◽

Phase Change Materials ◽

Heat Storage ◽

Storage Systems ◽

Storage System ◽

Saturation Temperature ◽

Steam Generation ◽

Latent Heat Storage ◽

Research Activities

Solar thermal systems, including direct steam generation in the absorbers, require isothermal energy storage systems. One option to fulfil this requirement is the application of phase change materials (PCMs) to absorb or release energy. The implementation of cost-effective storage systems demands the compensation of the low thermal heat conductivity that is characteristic for the candidate materials for PCM. Solar steam generation for power plants requires latent heat storage systems for a saturation temperature range between 200°C and 320°C. This paper describes the basic concepts investigated and first results of research activities aiming at the demonstration of a storage system using steam provided by parabolic trough collectors.

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Development of a Thermal Energy Storage System for Parabolic Trough Power Plants With Direct Steam Generation

ASME 2009 3rd International Conference on Energy Sustainability, Volume 2 ◽

10.1115/es2009-90038 ◽

2009 ◽

Cited By ~ 5

Author(s):

Doerte Laing ◽

Thomas Bauer ◽

Dorothea Lehmann ◽

Carsten Bahl

Keyword(s):

Heat Transfer ◽

Power Plants ◽

Storage System ◽

Thermal Power ◽

Sensible Heat ◽

Steam Generation ◽

Parabolic Trough ◽

Two Phase ◽

Solar Thermal Power ◽

Direct Steam

For future parabolic trough plants direct steam generation in the absorber pipes is a promising option for reducing the costs of solar thermal power generation. These new solar thermal power plants require innovative storage concepts, where the two phase heat transfer fluid poses a major challenge. A three-part storage system is proposed where a phase change material (PCM) storage will be deployed for the two-phase evaporation, while concrete storage will be used for storing sensible heat, i.e. for preheating of water and superheating of steam. A pinch analysis helps to recognize interface constraints imposed by the solar field and the power block and describes a way to dimension the latent and sensible components. Laboratory test results of a PCM test module with approx. 140 kg NaNO3, applying the sandwich concept for enhancement of heat transfer, are presented, proving the expected capacity and power density. The concrete storage material for sensible heat was improved to allow the operation up to 500 °C for direct steam generation. A storage system with a total storage capacity of approx. 1 MWh is described, combining a PCM module and a concrete module, which will be tested in 2009 under real steam conditions around 100 bar.

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Test Results of a Combined Storage System for Parabolic Trough Power Plants With Direct Steam Generation

ASME 2011 5th International Conference on Energy Sustainability, Parts A, B, and C ◽

10.1115/es2011-54850 ◽

2011 ◽

Cited By ~ 4

Author(s):

Doerte Laing ◽

Martin Eickhoff ◽

Michael Fiß ◽

Matthias Hempel ◽

Mirko Meyer-Gru¨nefeldt ◽

...

Keyword(s):

Power Plants ◽

Storage System ◽

Heat Transfer Fluid ◽

Steam Generation ◽

Parabolic Trough ◽

Two Phase ◽

Water Steam ◽

Direct Steam ◽

Two Phase Heat Transfer ◽

Heating Up

For future parabolic trough plants direct steam generation in the absorber pipes is a promising option for reducing the costs of solar thermal energy. These new solar thermal power plants require innovative storage concepts, where the two phase heat transfer fluid poses a major challenge. A three-part storage system is proposed for the two phase fluid water/steam. Concrete storage is used for the process steps involving transfer of sensible heat — i.e. preheating of water and superheating of steam — while for the two-phase evaporation a phase change material (PCM) storage will be deployed. This technology is currently developed by DLR and Ed. Zu¨blin AG within the project ITES, funded partly by the German Ministry for the Environment, Nature Conservation and Nuclear Safety. A combined storage solution with a 22 m3 concrete storage test module for superheating of steam and a 8.5 m3 PCM-storage for evaporation of water was build in 2009 in a direct steam test loop, set up at the power plant Litoral of Endesa in Carboneras, Spain. This high temperature storage system has a total capacity of approx. 1000 kWh and it will be the first demonstration of such a combined storage system for the two phase heat transfer fluid water/steam. Commissioning was completed in 2010, implying first heating-up of the concrete storage to expel the excess water in the concrete, first heating-up of the PCM storage including final filling of the storage with salt. Cycling tests for each storage unit separately are in progress. Combined testing will start in 2011. Results on the commissioning and testing will be reported in the paper.

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