Concentrating Solar Power

Optically transparent, thermally insulating monolithic silica aerogel, with its high solar transmittance and low thermal conductivity, is well-suited for solar thermal applications, particularly concentrated solar power systems. The properties of silica aerogel are directly determined by the structure of the highly porous, interconnected silica network. By using high temperature annealing to control this structure post-synthesis, we were able to optimize the material to increase solar transmittance using an easy and scalable method.The changes caused by annealing were investigated with respect to both temperature and time to relate the structural change to the optical and thermal performance change. The temperaturedependent study samples were annealed for 1 hour at various temperatures ranging from 400-1000 'C. The time-dependent studies used samples made from two silica aerogel chemistries and were annealed at two temperatures (400 'C and 600 C). In general, lower temperatures and times have less overall change (slower change rates) than higher temperature or longer time annealing. Both annealing studies indicate optical performance has an optimum with respect to annealing time, and additional temperature or time negatively affects optical properties due to appreciable structural change.After the temperature annealing studies were used to understand general trends, the timedependent studies were used to maximize the properties of aerogel for CSP applications. The samples showed an increase in solar spectral transmittance of over 3% while the effective thermal 3 conductivity was shown to increase by as much as 40%, indicating a need to optimize the annealing time for maximum performance. The properties of the characterized aerogels were used to demonstrate aerogel annealing optimization in a concentrated solar power receiver model operating at 400 *C. The model predicted a 1% receiver efficiency increase for an operating temperature of 400 *C by annealing for 24 hours, representing a significant gain in overall system efficiency.

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“…However, insulating the thermal receiver without affecting thermal energy collection can increase overall system efficiency. 5 …”

Section: Reached Maximum Solar Transmission At Much Longer Annealing mentioning

confidence: 99%

“…Using a simple idealized model, we can estimate receiver efficiency as described by Weinstein et a1 5 . We used a 1-D receiver configuration with an aerogel layer as shown in Figure 29 and receiver efficiency defined as…”

Section: Solar Thermal Receiver Efficiency Modelmentioning

confidence: 99%

High temperature annealing for structural optimization of silica aerogels in solar thermal applications

Strobach

Bhatia

Yang

et al. 2017

Journal of Non-Crystalline Solids

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“…[8][9][10][11][12] Plasmonic nanoparticles with absorption and scattering cross-sections exceeding their geometrical cross-sections have been recently developed and applied for direct solar steam generation [13][14][15][16][17][18][19][20][21][22][23][24] , but they typically require optical concentration of 10-1000x for steam generation. However, optical concentrators are expensive ($200/m 2 ) 25 , often accounting for a major portion of the capital cost of solar thermal systems.…”

mentioning

confidence: 99%

“…However, optical concentrators are expensive ($200/m 2 ) 25 , often accounting for a major portion of the capital cost of solar thermal systems. 8,11,26 In addition, they require support structures and access to electrical energy to track the sun. Although optical concentration is currently necessary for applications that require high temperatures such as concentrated solar power generation, solar thermal technologies that reduce or completely eliminate the reliance on optical concentration would have better market penetration.…”

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confidence: 99%

Steam generation under one sun enabled by a floating structure with thermal concentration

et al. 2016

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Abstract:Harvesting solar energy as heat has many applications, such as power generation, residential water heating, desalination, distillation and wastewater treatment. However, the solar flux is diffuse, and often requires optical concentration, a costly component, to generate high temperatures needed for some of these applications. Here we demonstrate a floating solar receiver capable of generating 100°C steam under ambient air conditions without optical concentration. The high temperatures are achieved by using thermal concentration and heat localization, which reduce the convective, conductive, and radiative heat losses. This demonstration of a low-cost and scalable solar vapor generator holds the promise of significantly expanding the application domain and reducing the cost of solar thermal systems. Keywords: solar thermal, steam generation, thermal concentration, water treatmentThe sun is a promising and abundant source of renewable energy that can potentially solve many of society's challenges. Solar thermal technologies, i.e., the conversion of the sunlight to thermal energy, are being developed for many applications such as power generation, domestic water heating, desalination, and other industrial processes. [1][2][3][4][5][6][7] Steam and vapor generation is often desired in these applications, but the dilute solar flux (1000 W/m 2 ) does not provide enough power per unit area of the absorber to reach the required high temperatures and to compensate for the large latent heat of water vaporization. Optical

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“…Photovoltaic cells are based on the principle of converting the photons into electricity by a photon absorption process in which the electron-hole pairs are generated. In the photo-thermal processes, heat can be generated by the device by efficiently absorbing the incident photons from the solar radiation with applications such as solar-heating, solar-thermal-electricity generation, solar-thermoelectrics, solar-thermophotovoltaics, and so on13456.…”

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confidence: 99%

High photon-to-heat conversion efficiency in the wavelength region of 250–1200 nm based on a thermoelectric Bi2Te3 film structure

Yao

Zang

et al. 2017

Sci Rep

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In this work, 4-layered SiO2/Bi2Te3/SiO2/Cu film structures were designed and fabricated and the optical properties investigated in the wavelength region of 250–1200 nm for their promising applications for direct solar-thermal-electric conversion. A typical 4-layered film sample with the structure SiO2 (66.6 nm)/Bi2Te3 (7.0 nm)/SiO2 (67.0 nm)/Cu (>100.0 nm) was deposited on a Si or K9-glass substrate by magnetron sputtering. The experimental results agree well with the simulated ones showing an average optical absorption of 96.5%, except in the shorter wavelength region, 250–500 nm, which demonstrates the superior absorption property of the 4-layered film due to the randomly rough surface of the Cu layer resulting from the higher deposition power. The high reflectance of the film structure in the long wavelength region of 2–20 μm will result in a low thermal emittance, 0.064 at 600 K. The simpler 4-layered structure with the thermoelectric Bi2Te3 used as the absorption layer may provide a straightforward way to obtain solar-thermal-electric conversion more efficiently through future study.

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Concentrating Solar Power

Cited by 453 publications

References 323 publications

High temperature annealing for structural optimization of silica aerogels in solar thermal applications

High temperature annealing for structural optimization of silica aerogels in solar thermal applications

Steam generation under one sun enabled by a floating structure with thermal concentration

High photon-to-heat conversion efficiency in the wavelength region of 250–1200 nm based on a thermoelectric Bi2Te3 film structure

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