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Research Papers

The Dynamic Behavior of Once-Through Direct Steam Generation Parabolic Trough Solar Collector Row Under Moving Shadow Conditions

[+] Author and Article Information
Su Guo

College of Energy and Electrical Engineering,
Hohai University,
Nanjing, Jiangsu 210098, China
e-mail: guosu81@126.com

Yinghao Chu

Department of Mechanical
and Aerospace Engineering,
Jacobs School of Engineering,
Center for Renewable Resource Integration/
Center for Energy Research,
University of California,
San Diego,
San Diego, CA 92093
e-mail: ychu@ucsd.edu

Deyou Liu

College of Energy and Electrical Engineering,
Hohai University,
Nanjing, Jiangsu 210098, China
e-mail: liudyhhuc@163.com

Xingying Chen

College of Energy and Electrical Engineering,
Hohai University,
Nanjing, Jiangsu 210098, China
e-mail: xychen@hhu.edu.cn

Chang Xu

College of Energy and Electrical Engineering,
Hohai University,
Nanjing, Jiangsu 210098, China
e-mail: zhuifengxu@163.com

Carlos F. M. Coimbra

Department of Mechanical
and Aerospace Engineering,
Jacobs School of Engineering,
Center for Renewable Resource Integration/
Center for Energy Research,
University of California,
San Diego,
San Diego, CA 92093
e-mail: ccoimbra@ucsd.edu

Ling Zhou

College of Water Conservancy
and Hydropower Engineering,
Hohai University,
Nanjing, Jiangsu 210098, China
e-mail: zlhhu@163.com

Qunming Liu

College of Energy and Electrical Engineering,
Hohai University,
Nanjing, Jiangsu 210098, China
e-mail: hhulqm@126.com

1Corresponding author.

Contributed by the Solar Energy Division of ASME for publication in the JOURNAL OF SOLAR ENERGY ENGINEERING: INCLUDING WIND ENERGY AND BUILDING ENERGY CONSERVATION. Manuscript received October 4, 2016; final manuscript received February 26, 2017; published online April 25, 2017. Assoc. Editor: Marc Röger.

J. Sol. Energy Eng 139(4), 041002 (Apr 25, 2017) (9 pages) Paper No: SOL-16-1438; doi: 10.1115/1.4036331 History: Received October 04, 2016; Revised February 26, 2017

Compared with recirculation and injection modes, once-through direct steam generation (DSG) parabolic troughs are simpler to construct and require the lowest investment. However, the heat transfer fluid (HTF) in once-through DSG parabolic trough systems has the most complicated dynamic behavior, particularly during periods of moving shadows caused by small clouds and jet contrails. In this paper, a nonlinear distributed parameter dynamic model (NDPDM) is proposed to model the dynamic behavior of once-through DSG parabolic trough solar collector row under moving shadow conditions. Compared with state-of-the-art models, the proposed NDPDM possesses three characteristics: (a) adopting real-time local values of the heat transfer and friction resistance coefficients, (b) simulating the whole collector row, including the boiler and the superheated sections, and (c) modeling the disturbance of direct normal irradiance (DNI) level on DSG parabolic trough solar collector row under moving shadow conditions. Validated using experimental data, the NDPDM accurately predicts the dynamic characteristics of HTF during periods of partial and moving DNI disturbance. The fundamental and specific dynamic process of fluid parameters for a DSG parabolic trough solar collector row is provided in this paper. The results show the following: (a) Moving shadows have a significant impact on the outlet temperature and mass flow rate, and the impact lasts up to 1000 s even after the shadows completely leave the collector row. (b) The time for outlet steam temperature to reach a steady-state value for the first time is independent of the shadow width, speed, and moving direction. (c) High-frequency chattering of the outlet mass flow rate can be observed under moving DNI disturbance and will have a longer duration if the shadow width is larger or the shadow speed is slower. Compared with cases in which the whole system is shaded, partially shading cases have shown a longer duration of high-frequency chattering. (d) Both wider widths and slower speeds of shadow will cause a larger amplitude of responses in the outlet temperature and mass flow rate. When the shadow speed is low, there is a longer delay time of response in the mass flow rate of the outlet fluid. (e) The amplitude of response in the outlet temperature does not depend on the direction of clouds movement. However, if the DNI disturbance starts at the inlet of the collector row, there will be significant delay times in both outlet temperature and mass flow rate, and a larger amplitude of response in outlet mass flow rate.

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References

Figures

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Fig. 1

Photos of partly cloudy skies and jet contrails (In the situations of partly cloudy skies [19] and jet contrails [20], when a cloud shadow enters the solar field, DNI on a certain segment of the collector row decreases for a short period and increases back to its original values after the shadow moves away.)

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Fig. 2

Physical models of moving shadows: (a) model for LINE field and (b) model for U field

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Fig. 3

Physical model of a DSG parabolic trough solar collector

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Fig. 4

Dynamic responses of parameters at the outlet of collector row on moving cloud conditions

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Fig. 5

Dynamic responses of parameters at the outlet of collector row on variable shadow width: (a) response of outlet fluid temperature and (b) response of outlet fluid mass flow rate

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Fig. 6

Dynamic responses of parameters at the outlet of collector row on variable shadow speed: (a) response of outlet fluid temperature and (b) response of outlet fluid mass flow rate

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Fig. 7

Dynamic responses of parameters at the outlet of the DSG parabolic trough solar collector row on variable shadow moving direction: (a) response of outlet fluid temperature and (b) response of outlet fluid mass flow rate

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