Analysis of the experimental behaviour of a 100 kWth latent heat storage system for direct steam generation in solar thermal 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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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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Detailed partial load investigation of a thermal energy storage concept for solar thermal power plants with direct steam generation

10.1063/1.4949140 ◽

2016 ◽

Cited By ~ 4

Author(s):

M. Seitz ◽

S. Hübner ◽

M. Johnson

Keyword(s):

Energy Storage ◽

Thermal Energy ◽

Thermal Energy Storage ◽

Power Plants ◽

Thermal Power ◽

Thermal Power Plants ◽

Steam Generation ◽

Solar Thermal Power ◽

Partial Load ◽

Direct Steam

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Considering Uncertainties in Research by Probabilistic Modeling

ASME 2012 6th International Conference on Energy Sustainability, Parts A and B ◽

10.1115/es2012-91055 ◽

2012 ◽

Cited By ~ 2

Author(s):

Markus Eck ◽

David Kretschmann ◽

Jan Fabian Feldhoff ◽

Michael Wittmann

Keyword(s):

Power Plants ◽

Thermal Power ◽

Thermal Power Plants ◽

Steam Generation ◽

Parabolic Trough ◽

Levelized Cost Of Electricity ◽

Solar Thermal Power ◽

Economical Evaluation ◽

Direct Steam ◽

Stochastic Input

Technical and economical evaluation of solar thermal power plants constantly gains more importance for industry and research. The reliability of the results highly depends on the assumptions made for the applied parameters. Reducing a power plant system to one single, deterministic number for evaluation, like the levelized cost of electricity (LCOE), might end in misleading results. Probabilistic approaches can help to better evaluate systems [1] and scenarios [2]. While industry looks for safety in investment and profitability, research is predominantly interested in the evaluation of concepts and the identification of promising new approaches. Especially for research, dealing with higher and hardly quantifiable uncertainties, it is desirable to get a detailed view of the system and its main influences. However, to get there, also a good knowledge on the stochastic interrelations and its interpretation is required. Therefore, this paper mainly assesses the influences of basic stochastic assumptions and suggests a methodology to consider suitable stochastic input, especially for parameters of systems still under research. As examples, the comparison between a parabolic trough plant with synthetic oil and direct steam generation is used.

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Latent Heat Storage Systems for Solar Thermal Power Plants and Process Heat Applications

Journal of Solar Energy Engineering ◽

10.1115/1.4001405 ◽

2010 ◽

Vol 132 (2) ◽

Cited By ~ 25

Author(s):

Wolf-Dieter Steinmann ◽

Doerte Laing ◽

Rainer Tamme

Keyword(s):

Latent Heat ◽

Power Plants ◽

Heat Storage ◽

Storage Systems ◽

Thermal Power ◽

Solar Thermal ◽

Thermal Power Plants ◽

Latent Heat Storage ◽

Solar Thermal Power ◽

Process Heat

Solar thermal systems using absorber evaporating steam directly require isothermal energy storage. The application of latent heat storage systems is an option to fulfill this demand. This concept has been demonstrated mainly for low temperature heating and refrigeration applications, the experience for the power level and temperature range characteristic of solar process heat and solar thermal power plants is limited. Cost effective implementation of the latent heat storage concept demands low cost phase change materials (PCMs). These PCMs usually show low thermal conductivity limiting the power density during the charging/discharging process. This paper describes various approaches, which have been investigated to overcome these limitations. Based on fundamental PCM-research and laboratory-scale experiments, the sandwich concept has been identified to show the highest potential. The sandwich concept has been demonstrated successfully for three different storage units ranging from 2 kW to 100 kW at melting temperatures of 145°C and 225°C.

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Detailed Modeling of Parabolic Trough Collectors for the Part Load Simulation of Solar Thermal Power Plants

Volume 6: Oil and Gas Applications; Concentrating Solar Power Plants; Steam Turbines; Wind Energy ◽

10.1115/gt2012-68032 ◽

2012 ◽

Cited By ~ 2

Author(s):

F. Zaversky ◽

S. Bergmann ◽

W. Sanz

Keyword(s):

Heat Transfer ◽

Power Plant ◽

Power Plants ◽

Thermal Power ◽

Solar Thermal ◽

Thermal Power Plants ◽

Steam Generation ◽

Parabolic Trough ◽

Solar Thermal Power ◽

Direct Steam

Solar thermal power plants are a promising way of providing clean renewable electric energy. These plants concentrate the incoming solar direct irradiation in order to heat up a heat transfer fluid. The collected thermal energy can be stored or instantly delivered to a power block where part of the thermal energy is converted to electrical energy in a turbine with the connected generator. The parabolic trough collector plant is the today’s most developed solar thermal power plant type. There the solar irradiation is focused on receiver tubes which are concentrically placed to the focal lines of the parabolic trough collectors. A high temperature oil is pumped through these receiver tubes, which collects the heat and delivers it later on to the steam generator of the connected Rankine steam cycle. In order to improve the efficiency of these solar thermal power plants, the direct steam generation (DSG) within the parabolic trough collector receiver tubes is being investigated. Both types of parabolic trough collectors, the conventional type using oil as heat transfer fluid and the direct steam generation type, are subject of this paper. A detailed steady-state parabolic trough collector model was developed for each type, using the thermodynamic simulation software IPSEpro. The developed models consider the cosine-loss attenuation factor, the shading attenuation factor, optical losses, as well as thermal losses. Appropriate heat transfer and pressure loss correlations were implemented for both collector types. For the direct steam generation model, distinct collectors for the preheating section, the evaporation section and the superheating section were used. Furthermore, the suitable length of discretization for the modeling of one collector loop within a center-fed solar field was investigated. Calculated solar field performance data for the oil concept were compared to validated data available in open literature. Finally, a power plant simulation with each collector type, over the course of one reference day, showed the great potential of the direct steam generation, as well as the suitability of IPSEpro for running solar thermal power plant yield simulations.

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