Influence of the Concentration Ratio on the Thermal and Economic Performance of Parabolic Trough Collectors with Double Glass Envelope

The heat loss of vacuum receiver plays critical important role in solar parabolic trough system. In this paper, experimental measurements and calculation models were conducted to investigate the heat loss of solar parabolic trough receiver with receiver length of 10.2 m and diameter of 0.120 m. In general, the heat loss of receiver decreased with the receiver wall temperature, while it can approach minimum under special wind condition. The heat loss of receiver mainly included the heat loss of glass and boundary region, and the heat losses of receiver, glass region and boundary region with tube temperatures of 176.2oC were respectively 987.1 W, 762.2 W and 224.9 W. Outside the glass envelope, the convection and radiation both play an important role in the heat loss of receiver, while the heat transfer is mainly dependent upon the radiation inside the glass envelope. In addition, the heat losses of convection outside the glass and radiation inside the glass from calculation very well agreed with the experimental data.

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Next Generation Parabolic Trough Solar Collectors for CSP

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

10.1115/es2012-91511 ◽

2012 ◽

Author(s):

Daniel T. Chen ◽

Glenn Reynolds ◽

Allison Gray ◽

Ben Ihas ◽

Gary Curtis ◽

...

Keyword(s):

Solar Collector ◽

Concentration Ratio ◽

Step Change ◽

Successful Implementation ◽

National Renewable Energy Laboratory ◽

Parabolic Trough ◽

Space Frames ◽

The Subject ◽

Utility Scale ◽

Parabolic Collector

In order for Concentrating Solar Power (CSP) to become a significant contributor to utility scale baseload power, dramatic reductions in cost and increases in performance must be achieved. 3M Company and Gossamer Space Frames have developed advanced collectors that are centered on a step-change in solar technology aimed at transforming the economics and industrialization of CSP. In particular, we focus on mirror film based reflective materials, stiff and shape accurate panel constructions, and lightweight and accurate space frames. These technology elements have been combined into a new parabolic collector design with an aperture of 7.3 m and length of 12 m. The geometric concentration ratio of the design is 103, far exceeding current designs. The National Renewable Energy Laboratory (NREL) has measured an intercept factor exceeding 99% on the subject collector fielded at SEGS II (Daggett, CA). The successful implementation of this technology platform has implications for new solar collector designs for both point and line focus systems.

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Performance evaluation and analyses of novel parabolic trough evacuated collector tubes with spectrum-selective glass envelope

Renewable Energy ◽

10.1016/j.renene.2019.02.025 ◽

2019 ◽

Vol 138 ◽

pp. 793-804 ◽

Cited By ~ 13

Author(s):

Qiliang Wang ◽

Mingke Hu ◽

Honglun Yang ◽

Jingyu Cao ◽

Jing Li ◽

...

Keyword(s):

Performance Evaluation ◽

Parabolic Trough ◽

Glass Envelope

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An analysis of the technical and economic performance of a parabolic trough concentrator for solar industrial process heat application

International Journal of Heat and Mass Transfer ◽

10.1016/0017-9310(82)90136-3 ◽

1982 ◽

Vol 25 (9) ◽

pp. 1427-1438 ◽

Cited By ~ 37

Author(s):

J.A. Clark

Keyword(s):

Economic Performance ◽

Industrial Process ◽

Parabolic Trough ◽

Heat Application ◽

Process Heat

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A Transient Thermography Method to Separate Heat Loss Mechanisms in Parabolic Trough Receivers

Journal of Solar Energy Engineering ◽

10.1115/1.4024739 ◽

2013 ◽

Vol 136 (1) ◽

Cited By ~ 5

Author(s):

Marc Röger ◽

Peter Potzel ◽

Johannes Pernpeintner ◽

Simon Caron

Keyword(s):

Heat Loss ◽

Temperature Measurements ◽

Thermal Excitation ◽

Transient Method ◽

Parabolic Trough ◽

Selective Coating ◽

Transient Thermography ◽

Energy Balances ◽

Glass Envelope ◽

Loss Mechanisms

This paper describes a transient thermography method to measure the heat loss of parabolic trough receivers and separate their heat loss mechanisms. This method is complementary to existing stationary techniques, which use either energy balances or glass envelope temperature measurements to derive overall heat losses. It is shown that the receiver heat loss can be calculated by applying a thermal excitation on the absorber tube and measuring both absorber tube and glass envelope temperature signals. Additionally, the emittance of the absorber selective coating and the vacuum quality of the annulus can be derived. The benefits and the limits of the transient method are presented and compared to the established stationary method based on glass envelope temperature measurements. Simulation studies and first validation experiments are described. A simulation based uncertainty analysis indicates that an uncertainty level of approximately 5% could be achieved on heat loss measurements for the transient method introduced in this paper, whereas for a conventional stationary field measurement technique, the uncertainty is estimated to 17–19%.

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Applicability of Heat Mirrors in Reducing Thermal Losses in Concentrating Solar Collectors

Volume 6B: Energy ◽

10.1115/imece2016-66565 ◽

2016 ◽

Author(s):

Prashant Mahendra ◽

Vikrant Khullar ◽

Madhup Mittal

Keyword(s):

Heat Transfer ◽

Thermal Efficiency ◽

Solar Irradiance ◽

Solar Collector ◽

Flux Distribution ◽

Heat Transfer Analysis ◽

Transfer Model ◽

Solar Collectors ◽

Parabolic Trough ◽

Glass Envelope

Flux distribution around the parabolic trough receiver being typically non-uniform, only a certain portion of the receiver circumference receives the concentrated solar irradiance. However, radiative and convective losses occur across the entire receiver circumference. This paper attempts to introduce the idea employing transparent heat mirror to effectively reduce the heat loss area and thus improve the thermal efficiency of the solar collector. Transparent heat mirror essentially has high transmissivity in the solar irradiance wavelength band and high reflectivity in the mid-infrared region thus it allows the solar irradiance to pass through but reflects the infrared radiation back to the solar selective metal tube. Practically, this could be realized if certain portion of the conventional low iron glass envelope is coated with Sn-In2O3 so that its acts as a heat mirror. In the present study, a parabolic receiver design employing the aforesaid concept has been proposed. Detailed heat transfer model has been formulated. The results of the model were compared with the experimental results of conventional concentrating parabolic trough solar collectors in the literature. It was observed that while maintaining the same external conditions (such as ambient/initial temperatures, wind speed, solar insolation, flow rate, concentration ratio etc.) the heat mirror-based parabolic trough concentrating solar collector has about 3–12% higher thermal efficiency as compared to the conventional parabolic solar collector. Furthermore, steady state heat transfer analysis reveals that depending on the solar flux distribution there is an optimum circumferential angle (θ = θoptimum, where θ is the heat mirror circumferential angle) up to which the glass envelope should be coated with Sn-In2O3. For angles higher than the optimum angle, the collector efficiency tends to decrease owing to increase in optical losses.

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