Characterization of Pyromark 2500 for High-Temperature Solar Receivers

2012 ◽  
Author(s):  
Clifford K. Ho ◽  
A. Roderick Mahoney ◽  
Andrea Ambrosini ◽  
Marlene Bencomo ◽  
Aaron Hall ◽  
...  
Keyword(s):  
High Temperature ◽  
Elevated Temperatures ◽  
Normal Incidence ◽  
Radiative Properties ◽  
Plant Laboratory ◽  
Solar Absorptance ◽  
Total Hemispherical Emittance ◽  
Curing Methods ◽  
The Cost ◽  
Solar Receiver

Pyromark 2500 is a silicone-based high-temperature paint that has been used on central receivers to increase solar absorptance. The cost, application, curing methods, radiative properties, and absorber efficiency of Pyromark 2500 are presented in this paper for use as a baseline for comparison to high-temperature solar selective absorber coatings currently being developed. The directional solar absorptance was calculated from directional spectral absorptance data, and values for pristine samples of Pyromark 2500 were as high as 0.96–0.97 at near normal incidence angles. At higher irradiance angles (>40°–60°), the solar absorptance decreased. The total hemispherical emittance of Pyromark 2500 was calculated from spectral directional emittance data measured at room temperature and 600°C. The total hemispherical emittance values ranged from ∼0.80–0.89 at surface temperatures ranging from 100°C – 1,000°C. The aging and degradation of Pyromark 2500 with exposure at elevated temperatures were also examined. Previous tests showed that solar receiver panels had to be repainted after three years due to a decrease in solar absorptance to 0.88 at the Solar One central receiver pilot plant. Laboratory studies also showed that exposure of Pyromark 2500 at high temperatures (750°C and higher) resulted in significant decreases in solar absorptance within a few days. However, at 650°C and below, the solar absorptance did not decrease appreciably after several thousand hours of testing. Finally, the absorber efficiency of Pyromark 2500 was determined as a function of temperature and irradiance using the calculated solar absorptance and emittance values presented in this paper.

Characterization of Pyromark 2500 Paint for High-Temperature Solar Receivers

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Clifford K. Ho ◽  
A. Roderick Mahoney ◽  
Andrea Ambrosini ◽  
Marlene Bencomo ◽  
Aaron Hall ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Normal Incidence ◽  
Radiative Properties ◽  
Solar Absorptance ◽  
Thermal Emittance ◽  
Percentage Points ◽  
Original Coating

Pyromark 2500 is a silicone-based high-temperature paint that has been used on central receivers to increase solar absorptance. The radiative properties, aging, and selective absorber efficiency of Pyromark 2500 are presented in this paper for use as a baseline for comparison to high-temperature solar selective absorber coatings currently being developed. The solar absorptance ranged from ∼0.97 at near-normal incidence angles to ∼0.8 at glancing (80°) incidence angles, and the thermal emittance ranged from ∼0.8 at 100 °C to ∼0.9 at 1000 °C. After thermal aging at temperatures of ∼750 °C or higher, the solar absorptance decreased by several percentage points within a few days. It was postulated that the substrate may have contributed to a change in the crystal structure of the original coating at elevated temperatures.

scholarly journals Improved High Temperature Solar Absorbers for Use in Concentrating Solar Power Central Receiver Applications

2011 ◽  
Author(s):  
Andrea Ambrosini ◽  
Timothy N. Lambert ◽  
Marlene Bencomo ◽  
Aaron Hall ◽  
Kent vanEvery ◽  
...  
Keyword(s):  
High Temperature ◽  
Solar Power ◽  
Low Cost ◽  
Concentrating Solar Power ◽  
Solar Absorptance ◽  
Thermal Emittance ◽  
Solar Absorbers ◽  
Operating Temperatures ◽  
Stability Issues ◽  
The Cost

Concentrating solar power (CSP) systems use solar absorbers to convert the heat from sunlight to electric power. Increased operating temperatures are necessary to lower the cost of solar-generated electricity by improving efficiencies and reducing thermal energy storage costs. Durable new materials are needed to cope with operating temperatures < 600°C. The current coating technology (Pyromark High Temperature paint) has a solar absorptance in excess of 0.95 but a thermal emittance greater than 0.8, which results in large thermal losses at high temperatures. In addition, because solar receivers operate in air, these coatings have long term stability issues that add to the operating costs of CSP facilities. Ideal absorbers must have high solar absorptance (>0.95) and low thermal emittance (<0.3 at receiver surface operating temperatures), be stable in air, and be low-cost and readily manufacturable. Recent efforts at Sandia National Laboratories have begun to address the issue of more efficient solar selective coatings for tower applications. This paper will present an overview of these efforts which address the development of new coatings on several fronts.

Progress in Development of High-Temperature Solar-Selective Coating

Solar Energy ◽  
2005 ◽  
Author(s):  
C. E. Kennedy ◽  
H. Price
Keyword(s):  
High Temperature ◽  
Computer Aided Design ◽  
Solar Absorptance ◽  
Selective Coating ◽  
Operating Limits ◽  
And Performance ◽  
The Stability ◽  
Solar Electricity ◽  
The Cost ◽  
Aided Design

Improving the properties of the selective coating on the receiver represents one of the best opportunities for improving the efficiency of parabolic trough collectors and reducing the cost of solar electricity. Additionally, increasing the operating temperature above the current operating limits of 400°C can improve power cycle efficiency and reduce the cost of thermal energy storage resulting in reductions in the cost of solar electricity. Current coatings do not have the stability and performance necessary to move to higher operating temperatures. The objective of this effort was to develop new, more-efficient selective coatings with both high solar absorptance (α ≥ 0.96) and low thermal emittance (ε ≤ 0.07 at 400°C) that are thermally stable above 500°C, ideally in air, with improved durability and manufacturability and reduced cost. Using computer-aided design software, we successfully modeled a solar-selective coating composed of materials stable at high temperature that exceeded our property goals. In preparation for characterization of samples of these new coatings, a round-robin experiment was conducted to verify the accuracy of the selective coating reflectance measurements.

Optical Properties of Select Particulates After High-Temperature Exposure

2014 ◽  
Author(s):  
Jonathan Roop ◽  
Sheldon Jeter ◽  
Said I. Abdel-Khalik ◽  
Clifford K. Ho
Keyword(s):  
Optical Properties ◽  
High Temperature ◽  
High Temperatures ◽  
Viable Option ◽  
Solar Absorptance ◽  
High Temperature Exposure ◽  
Central Receiver ◽  
Total Hemispherical Emittance ◽  
Receiver System ◽  
Temperature Exposure

One increasingly viable option for high temperature concentrator solar power (CSP) is a central receiver system with a particle heating receiver (PHR). A PHR system uses suitable particulates to capture and store energy. It is expected that the particles will be sustained at high temperatures (in the range of 300°C or 400°C to 700°C or 800°C or even 1000°C) on most typical days of plant operation, so there is interest in how the particle optical properties might change after prolonged high-temperature exposure. This paper presents the results from experiments conducted over a 5-month period in which samples of various types of particulates including silica sands and alumina proppants were exposed to high temperatures for extended periods of time. The reflectance of a bed of particles was measured at room temperature in 8 wavelength bands using the 410-Solar reflectometer device developed by Surface Optics Corporation. The infrared emittance was determined using the ETS-100 emissometer instrument, also developed by Surface Optics Corporation [1,2]. Particles were heated to 950°C and 350°C, and measurements were recorded at intervals during the exposure so that trends in the optical properties over time could be observed. From the measured data, the total solar absorptance and total hemispherical emittance at high temperature were computed; these results are also presented.

Application of Sol-Gel Method as a Protective Layer on a Specular Reflective Surface for Secondary Reflector in a Solar Receiver

2016 ◽  
Author(s):  
Samia Afrin ◽  
John Dagdelen ◽  
Zhiwen Ma ◽  
Vinod Kumar
Keyword(s):  
Optical Properties ◽  
High Temperature ◽  
High Efficiency ◽  
Elevated Temperatures ◽  
Sol Gel ◽  
Film Structure ◽  
Gel Method ◽  
Sol Gel Method ◽  
Reflective Surface ◽  
Solar Receiver

Highly-specular reflective surfaces that can withstand elevated-temperatures are desirable for many applications including reflective heat shielding in solar receivers and secondary reflectors, which can be used between primary concentrators and heat collectors. A high-efficiency, high-temperature solar receiver design based on arrays of cavities needs a highly-specular reflective surface on its front section to help sunlight penetrate into the absorber tubes for effective flux spreading. Since this application is for high-temperature solar receivers, this surface needs to be durable and to maintain its optical properties through the usable life. Degradation mechanisms associated with elevated temperatures and thermal cycling, which include cracking, delamination, corrosion/oxidation, and environmental effects, could cause the optical properties of surfaces to degrade rapidly in these conditions. Protected mirror surfaces for these applications have been tested by depositing a thin layer of SiO2 on top of electrodeposited silver by means of the sol-gel method. To obtain an effective thin film structure, this sol-gel procedure has been investigated extensively by varying process parameters that affect film porosity and thickness. Endurance tests have been performed in a furnace at 150°C for thousands of hours. This paper presents the sol-gel process for intermediate-temperature specular reflective coatings and provides the long-term reliability test results of sol-gel protected silver-coated surfaces.

High-Temperature Instability of A Cr2Nb-Nb(Cr) Microlaminate Composite

1996 ◽  
Vol 54 ◽  
pp. 374-375
Author(s):  
M. Larsen ◽  
R.G. Rowe ◽  
D.W. Skelly
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Aircraft Engine ◽  
Lattice Parameter ◽  
Microstructural Stability ◽  
Elevated Temperature Strength ◽  
Cross Sectional ◽  
Bcc Structure

Microlaminate composites consisting of alternating layers of a high temperature intermetallic compound for elevated temperature strength and a ductile refractory metal for toughening may have uses in aircraft engine turbines. Microstructural stability at elevated temperatures is a crucial requirement for these composites. A microlaminate composite consisting of alternating layers of Cr2Nb and Nb(Cr) was produced by vapor phase deposition. The stability of the layers at elevated temperatures was investigated by cross-sectional TEM.The as-deposited composite consists of layers of a Nb(Cr) solid solution with a composition in atomic percent of 91% Nb and 9% Cr. It has a bcc structure with highly elongated grains. Alternating with this Nb(Cr) layer is the Cr2Nb layer. However, this layer has deposited as a fine grain Cr(Nb) solid solution with a metastable bcc structure and a lattice parameter about half way between that of pure Nb and pure Cr. The atomic composition of this layer is 60% Cr and 40% Nb. The interface between the layers in the as-deposited condition appears very flat (figure 1). After a two hour, 1200 °C heat treatment, the metastable Cr(Nb) layer transforms to the Cr2Nb phase with the C15 cubic structure. Grain coarsening occurs in the Nb(Cr) layer and the interface between the layers roughen. The roughening of the interface is a prelude to an instability of the interface at higher heat treatment temperatures with perturbations of the Cr2Nb grains penetrating into the Nb(Cr) layer.

Phase transformation and layer evolution in molybdenum disilicide-silicon carbide nanolayered coatings

1994 ◽  
Vol 52 ◽  
pp. 538-539
Author(s):  
H. Kung ◽  
T. R. Jervis ◽  
J.-P. Hirvonen ◽  
M. Nastasi ◽  
T. E. Mitchell ◽  
...  
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Oxidation Resistance ◽  
Elevated Temperatures ◽  
Matrix Material ◽  
Molybdenum Disilicide ◽  
High Temperature Strength ◽  
Cross Sectional ◽  
Good Oxidation Resistance ◽  
Structural Applications

MoSi2 is a potential matrix material for high temperature structural composites due to its high melting temperature and good oxidation resistance at elevated temperatures. The two major drawbacksfor structural applications are inadequate high temperature strength and poor low temperature ductility. The search for appropriate composite additions has been the focus of extensive investigations in recent years. The addition of SiC in a nanolayered configuration was shown to exhibit superior oxidation resistance and significant hardness increase through annealing at 500°C. One potential application of MoSi2- SiC multilayers is for high temperature coatings, where structural stability ofthe layering is of major concern. In this study, we have systematically investigated both the evolution of phases and the stability of layers by varying the heat treating conditions.Alternating layers of MoSi2 and SiC were synthesized by DC-magnetron and rf-diode sputtering respectively. Cross-sectional transmission electron microscopy (XTEM) was used to examine three distinct reactions in the specimens when exposed to different annealing conditions: crystallization and phase transformation of MoSi2, crystallization of SiC, and spheroidization of the layer structures.

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