Combined Storage System Developments for Direct Steam Generation in Solar Thermal Power Plants

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

Journal of Solar Energy Engineering ◽

10.1115/1.4001472 ◽

2010 ◽

Vol 132 (2) ◽

Cited By ~ 27

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 ∼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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Comparative System Performance Analysis of Direct Steam Generation Central Receiver Solar Thermal Power Plants in Megawatt Range

Journal of Solar Energy Engineering ◽

10.1115/1.4026279 ◽

2014 ◽

Vol 136 (1) ◽

Cited By ~ 14

Author(s):

Javier Sanz-Bermejo ◽

Víctor Gallardo-Natividad ◽

José Gonzalez-Aguilar ◽

Manuel Romero

Keyword(s):

Power Plants ◽

Superheated Steam ◽

Thermal Power ◽

Solar Thermal ◽

Saturated Steam ◽

Thermal Power Plants ◽

Steam Generation ◽

Optical Efficiency ◽

Solar Thermal Power ◽

Central Receiver

This work proposes and analyses several integration schemes specially conceived for direct steam generation (DSG) in megawatt (MW) range central receiver solar thermal power plants. It is focused on the optical performance related to the heliostat field and the arrangement of receiver absorbers, and the management of steam within a Rankine cycle in the range between 40–160 bar and 400–550 °C at design point. The solar receiver is composed of one single element for saturated steam systems or two vertically aligned separated units, which correspond to the boiler and the superheater (dual-receiver concept), for superheated steam solar thermal power plants. From a fixed heliostat field obtained after layout optimization for the saturated steam solar plant the heliostat field is divided in two concentric circular trapezoids where each of them independently supplies the solar energy required by the boiler and the superheater for the different steam conditions. It has been observed that the arrangement locating the boiler above the superheater provides a slightly higher optical efficiency of the collector system, formed by the solar field and the receiver, compared with the reverse option with superheater above boiler. Besides, two-zone solar fields provide lower performances than the entire heliostat layout aiming at one absorber (saturation systems). Optical efficiency of two-zone solar fields decreases almost linearly with the increment of superheater heat demand. Concerning the whole solar collector, heliostat field plus receiver, the performance decreases with temperature and almost linearly with the steam pressure. For the intervals of steam pressure and temperature under analysis, solar collector of saturated steam plant achieves an optical efficiency 3.2% points higher than the superheated steam system at 40 bar and 400 °C, and the difference increases up to 9.3% points when compared with superheated system at 160 bar and 550 °C. On the other hand, superheated steam systems at 550 °C and pressure between 60 and 80 bar provide the highest overall efficiency, and it is 2.3% points higher than performance of a saturated steam solar plant at 69 bar. However, if saturated steam cycle integrates an intermediate reheat process, both would provide similar performances. Finally, it has been observed that central receiver systems (CRS) producing saturated steam and superheated steam at 500 °C operating at 40 bar provide similar performances.

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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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Energy management in solar thermal power plants with double thermal storage system and subdivided solar field

Applied Energy ◽

10.1016/j.apenergy.2011.04.036 ◽

2011 ◽

Vol 88 (11) ◽

pp. 4055-4066 ◽

Cited By ~ 34

Author(s):

Antonio Rovira ◽

María José Montes ◽

Manuel Valdes ◽

José María Martínez-Val

Keyword(s):

Energy Management ◽

Power Plants ◽

Storage System ◽

Thermal Power ◽

Thermal Storage ◽

Solar Thermal ◽

Thermal Power Plants ◽

Solar Thermal Power ◽

Solar Field

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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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