ORCID Profile
0000-0002-4579-6183
Current Organisations
Boise State University
,
Exaeris Water Innovations, LLC
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Publications
Envisioning advanced solar electricity generation: Parametric studies of CPV/T systems with spectral filtering and high temperature PV
Publisher: Elsevier BV
Date: 02-2015
Impact of size and scattering mode on the optimal solar absorbing nanofluid
Publisher: ASMEDC
Date: 2009
DOI: 10.1115/ES2009-90066
Abstract: The concept of using a direct absorbing nanofluid, a liquid-nanoparticle suspension, has recently been shown numerically and experimentally to be an efficient method for harvesting solar thermal energy. Studies show that the size and shape of the nanoparticles as well as the scattering mode (e.g. dependent, independent, and multiple) all impact the amount of energy absorbed and emitted by the nanofluid. In order to optimize the efficiency of a direct absorption solar thermal system the optimum nanoparticle-liquid combination needs to be developed. The optimum nanofluid for a direct absorption solar thermal collector is investigated numerically through the variation of particle size, including the impact of size on optical properties, and scattering mode. The study addresses both the absorption of solar energy within the fluid as well as the emission of the fluid.
Numerical Study of Solar Photovoltaic/Thermal (PV/T) Hybrid Collector Using Nanofluids
Publisher: American Society of Mechanical Engineers
Date: 11-12-2013
Abstract: The commonly used methods to harness solar energy are solar thermal and solar photovoltaic (PV). A new category photovoltaic/thermal (PV/T) hybrid combines these two technologies, and achieves higher combined efficiency. The challenge is to keep the operating temperature of the PV low and at the same time not compromise on the temperature of the thermal cycle. Various designs of PV/T hybrids (both flat plate and concentrated) have already been proposed which utilize air or water to remove the heat from PV cells in order to enhance the overall efficiency of PV/T hybrid collector. Recent papers have showed that nanofluids can be used as an optical filter to filter the required wavelength range (equivalent to the band gap of the PV cell) from solar spectra. Thus, the heating of PV cells can be significantly reduced and higher overall efficiencies can be achieved using selective absorption by nanofluids. In this study, a new design of a PV/T hybrid collector was proposed and two nanofluid filters that can be used with Silicon (Si) PV cells were identified and corresponding thermal and overall efficiencies of PV/T hybrid collector were calculated.
A review of nanofluid-based direct absorption solar collectors: Design considerations and experiments with hybrid PV/Thermal and direct steam generation collectors
Publisher: Elsevier BV
Date: 2020
Vapor generation in a nanoparticle liquid suspension using a focused, continuous laser
Publisher: AIP Publishing
Date: 19-10-2009
DOI: 10.1063/1.3250174
Abstract: This letter discusses experimentation with optically induced phase change in nanoparticle liquid suspensions—commonly termed nanofluids. Four different types of nanofluids at five concentrations were exposed to a ∼120 mW, 532 nm laser beam to determine the minimum laser flux needed to create vapor. Laser irradiance was varied between 0–770 W cm−2. While the experiments were simple, they involved many complex, interrelated physical phenomena, including: subcooled boiling, thermal driven particle/bubble motion, nanoparticle radiative absorption/scattering, and nanoparticle clumping. Such phenomena could enable novel solar collectors in which the working fluid directly absorbs energy and undergoes phase change in a single step.
Fabrication and comparison of selective, transparent optics for concentrating solar systems
Publisher: SPIE
Date: 05-09-2015
DOI: 10.1117/12.2185742
Characterization of light-induced, volumetric steam generation in nanofluids
Publisher: Elsevier BV
Date: 06-2012
Filtering light with nanoparticles: A review of optically selective particles and applications
Publisher: The Optical Society
Date: 02-09-2016
DOI: 10.1364/AOP.8.000541
Solar energy harvesting using nanofluids-based concentrating solar collector
Publisher: American Society of Mechanical Engineers
Date: 03-03-2012
Abstract: Dispersing trace amounts of nanoparticles into the base-fluid has significant impact on the optical as well as thermo-physical properties of the base-fluid. This characteristic can be utilized in effectively capturing as well as transporting the solar radiant energy. Enhancement of the solar irradiance absorption capacity of the base fluid scales up the heat transfer rate resulting in higher & more efficient heat transfer. This paper attempts to introduce the idea of harvesting the solar radiant energy through usage of nanofluid-based concentrating parabolic solar collectors. In order to theoretically analyze the nanofluid-based concentrating parabolic solar collector (NCPSC) it has been mathematically modeled, and the governing equations have been numerically solved using finite difference technique. The results of the model were compared with the experimental results of conventional concentrating parabolic solar collectors under similar conditions. It was observed that while maintaining the same external conditions (such as ambient/inlet temperatures, wind speed, solar insolation, flow rate, concentration ratio etc.) the NCPSC has about 5–10% higher efficiency as compared to the conventional parabolic solar collector. Furthermore, some parametric studies were carried out which reflected the effect of various parameters such as solar insolation, incident angle, convective heat transfer coefficient etc. on the performance indicators such as thermal efficiency etc.
Tuning the Extinction Coefficient for Direct Absorption Solar Thermal Collector Optimization
Publisher: ASMEDC
Date: 2010
DOI: 10.1115/ES2010-90022
Abstract: Direct-absorption solar thermal collectors have recently been shown to be a promising technology for photothermal energy conversion but many parameters affecting the overall performance of such systems haven’t been studied in depth, yet alone optimized. Earlier work has shown that the overall magnitude of the extinction coefficient can play a drastic role, with too high of an extinction coefficient actually reducing the efficiency. This study investigates how the extinction coefficient impacts the collector efficiency and how it can be tuned as a function of depth to optimize the efficiency, and why this presents a unique design over conventional solar thermal collection systems. Three extinction profiles are investigated: uniform, linearly increasing, and exponentially increasing.
Feasibility of nanofluid-based optical filters
Publisher: The Optical Society
Date: 25-02-2013
DOI: 10.1364/AO.52.001413
Solar Selective Volumetric Receivers for Harnessing Solar Thermal Energy
Publisher: ASME International
Date: 11-04-2018
DOI: 10.1115/1.4039214
Abstract: Given the largely untapped solar energy resource, there has been an ongoing international effort to engineer improved solar-harvesting technologies. Toward this, the possibility of engineering a solar selective volumetric receiver (SSVR) has been explored in the present study. Common heat transfer liquids (HTLs) typically have high transmissivity in the visible-near infrared (VIS-NIR) region and high emission in the midinfrared region, due to the presence of intramolecular vibration bands. This precludes them from being solar absorbers. In fact, they have nearly the opposite properties from selective surfaces such as cermet, TiNOX, and black chrome. However, liquid receivers which approach the radiative properties of selective surfaces can be realized through a combination of anisotropic geometries of metal nanoparticles (or broad band absorption multiwalled carbon nanotubes (MWCNTs)) and transparent heat mirrors. SSVRs represent a paradigm shift in the manner in which solar thermal energy is harnessed and promise higher thermal efficiencies (and lower material requirements) than their surface absorption-based counterparts. In the present work, the “effective” solar absorption to infrared emission ratio has been evaluated for a representative SSVR employing copper nanospheroids/MWCNTs and Sn-In2O3 based heat mirrors. It has been found that a solar selectivity comparable to (or even higher than) cermet-based Schott receiver is achievable through control of the cut-off solar selective wavelength. Theoretical calculations show that the thermal efficiency of Sn-In2O3 based SSVR is 6–7% higher than the cermet-based Schott receiver. Furthermore, stagnation temperature experiments have been conducted on a laboratory-scale SSVR to validate the theoretical results. It has been found that higher stagnation temperatures (and hence higher thermal efficiencies) compared to conventional surface absorption-based collectors are achievable through proper control of nanoparticle concentration.
Nanofluid optical property characterization: towards efficient direct absorption solar collectors
Publisher: Springer Science and Business Media LLC
Date: 15-03-2011
Abstract: Suspensions of nanoparticles (i.e., particles with diameters 100 nm) in liquids, termed nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, their absorption of the solar spectrum must be established. Accordingly, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (0.25 to 2.5 μm). A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient. Comparisons with measured extinction coefficients reveal that the approximation works well with water-based nanofluids containing graphite nanoparticles but less well with metallic nanoparticles and/or oil-based fluids. For the materials used in this study, over 95% of incoming sunlight can be absorbed (in a nanofluid thickness ≥10 cm) with extremely low nanoparticle volume fractions - less than 1 × 10 -5 , or 10 parts per million. Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase.
Solar Energy Harvesting Using Nanofluids-Based Concentrating Solar Collector
Publisher: ASME International
Date: 08-2012
DOI: 10.1115/1.4007387
Abstract: Dispersing trace amounts of nanoparticles into common base-fluids has a significant impact on the optical as well as thermophysical properties of the base-fluid. This characteristic can be utilized to effectively capture and transport solar radiation. Enhancement of the solar irradiance absorption capacity leads to a higher heat transfer rate resulting in more efficient heat transfer. This paper attempts to introduce the idea of harvesting solar radiant energy through usage of nanofluid-based concentrating parabolic solar collectors (NCPSC). In order to theoretically analyze the NCPSC, it has been mathematically modeled, and the governing equations have been numerically solved using finite difference technique. The results of the model were compared with the experimental results of conventional concentrating parabolic solar collectors under similar conditions. It was observed that while maintaining the same external conditions (such as ambient/inlet temperatures, wind speed, solar insolation, flow rate, concentration ratio, etc.) the NCPSC has about 5–10% higher efficiency as compared to the conventional parabolic solar collector. Furthermore, parametric studies were carried out to discover the influence of various parameters on performance and efficiency. The following parameters were studied in the present study: solar insolation, incident angle, and the convective heat transfer coefficient. The theoretical results clearly indicate that the NCPSC has the potential to harness solar radiant energy more efficiently than a conventional parabolic trough.
Photovoltaic/thermal system performance utilizing thin film and nanoparticle dispersion based optical filters
Publisher: AIP Publishing
Date: 05-2013
DOI: 10.1063/1.4811095
Abstract: Hybrid photovoltaic/thermal (PV/T) collectors would benefit from the use of fluid based optical filters as a means to separate the useful irradiance for the PV cell from those wavelengths which are more suited to heat generation. Nanoparticle based dispersions within a working fluid can be designed/tuned to serve as optical filters for this purpose. The advantage of this concept is that the thermal part of the system is separated, allowing the photovoltaic and thermal components to operate at significantly different temperatures. Additionally, by using a fluid filter, it is relatively easy to remove heat from the thermal side. This paper theoretically investigates the performance of nanoparticle-based and conventional thin film-based optical fluid filters within a concentrating hybrid PV/T system. General results are presented to demonstrate the impact to overall efficiency when a realistic (i.e., non-ideal) filter is used at a wide-range of operating conditions. The results demonstrate that nanoparticle based filters have a slightly lower overall efficiency compared to the conventional thin film filters due to their lower performance within the window of high transmittance to the PV cell. However, nanoparticle based filters achieve up to 4% higher thermal efficiencies as a result of their significantly reduced filter thickness demonstrating their potential as a favorable compact and lower cost design.
Multifunctional core-shell nanoparticle suspensions for efficient absorption
Publisher: ASME International
Date: 21-11-2013
DOI: 10.1115/1.4007845
Abstract: Nanoparticle suspensions are known to offer a variety of benefits for thermal transport and energy conversion. Of particular relevance here are the vast changes to the radiative properties due to the plasmonic nanostructures' large extinction cross section at the corresponding surface plasmon resonance (SPR) wavelength. Recent papers have showed that dielectric core/metallic shell nanoparticles yielded a plasmon resonance wavelength tunable from visible to infrared by changing the ratio of core radius to the total radius. Therefore, we are interested in developing a dispersion of core-shell multifunctional nanoparticles capable of dynamically changing their volume ratio and thus their spectral radiative properties. This paper investigates the surface plasmon resonance effect, wavelength tuning ranges for different metallic shell nanoparticles, and explores the solar-weighted efficiencies of corresponding core-shell nanoparticle suspensions. Through our electrostatic model, we estimate a red-shift in the plasmon resonance peak from a wavelength of about 600 nm to around 1400 nm for Au coated silicon core nanoparticles. Using core-shell nanoparticle dispersions, it is possible to create efficient spectral solar absorption fluids and design materials for applications which require variable spectral absorption or scattering.
Trends and Opportunities in Direct-Absorption Solar Thermal Collectors
Publisher: ASME International
Date: 17-05-0022
DOI: 10.1115/1.4023930
Abstract: Efficient conversion of sunlight into useful heat or work is of increasing global interest. Solar-to-thermal energy conversion, as opposed to solar-to-electricity, is enabled by solar thermal collectors that convert sunlight into heat at some useful temperature. We review here recent developments in solar thermal energy conversion. Our emphasis is on “direct-absorption” solar thermal collectors, in which incident sunlight is absorbed directly by a working fluid. This contrasts with conventional solar thermal collectors where the sunlight strikes and is absorbed by a solid receiver, which then transfers heat to the working fluid. Both liquid-based and gas-based direct-absorption collectors are described, although liquid-based systems are emphasized. We propose that if “direct-absorption” technologies could be developed further, it would open up a number of emerging opportunities, including applications exploiting thermochemical and photocatalytic reactions and direct absorption of a binary fluid for absorption refrigeration.
Surface plasmon resonance shifts of a dispersion of core-shell nanoparticles for efficient solar absorption
Publisher: American Society of Mechanical Engineers
Date: 03-03-2012
Abstract: Nanoparticles are known to offer a variety of benefits for thermal transport, and of particular relevance here are the vast changes to the radiative properties due to the large extinction cross section at the corresponding surface plasmon resonance wavelength [1, 2]. Recent papers have indicated that dielectric core metallic shell nanoparticles yielded a plasmon resonance tunable from ultraviolet to infrared by changing the ratio of core radius to the total radius [3–6]. We are interested in developing a dispersion of core-shell multifunctional nanoparticles capable of dynamically changing their volume ratio and thus their spectral radiative properties. This work addresses the plasmon resonance tuning ranges for different metallic shell nanoparticles, and explores the solar-weighted efficiencies of corresponding core-shell nanoparticle dispersions. Through our electrostatic model, we achieve a shift in the plasmon resonance peak from a wavelength of about 500 nm to around 1500 nm for Au-coated silica core nanoparticles. Using core-shell nanoparticles dispersions, we show that it is possible to create efficient spectral solar absorption fluids. We also demonstrate that it is possible to design materials for applications which require variable spectral absorption or scattering.
Experimental results for light-induced boiling in water-based graphite nanoparticle suspensions
Publisher: ASMEDC
Date: 2009
DOI: 10.1115/HT2009-88176
Abstract: One relatively simple subset of nanotechnology is nanofluids, obtained by the addition of nanoparticles to a conventional base fluid. The promise of nanofluids stems from the fact that at relatively small particle loading (typically & % by volume) significant enhancement in thermal transport may be possible [1–3]. Since there are a wide variety of nanoparticle materials to choose from, nanofluidic systems can be tuned to fit a number of applications. This research focuses on direct thermal collection of light energy using highly absorptive nanofluids. Experimental tests are conducted using a 0.1% by volume graphite/water (30nm nominal particle diameter) nanofluid exposed to a 130 mW, 532 nm, continuous laser. A lens is placed between the laser and the fluid to achieve a high-energy flux (∼ 490 Wcm−2). Since initially over 99.9% of the light is absorbed in a path length of 0.1 mm, the irradiated portion of the base fluid collects enough energy to vaporize. Heuristic methods of analysis demonstrate this situation incorporates several interesting modes of heat transfer and fluid mechanics. These experiments also reveal the possibility for novel solar collectors in which the working fluid directly absorbs energy and undergoes phase change in a single step.
Solar Selective Volumetric Receivers for Harnessing Solar Thermal Energy
Publisher: American Society of Mechanical Engineers
Date: 11-11-2016
Abstract: Given the largely untapped solar energy resource, there has been an ongoing international effort to engineer improved solar-harvesting technologies. Towards this, the possibility of engineering a solar selective volumetric receiver (SSVR) has been explored in the present study. Common heat transfer liquids (HTLs) typically have high transmissivity in the visible-near infrared (NIR) region and high emission in the mid-infrared region, due to the presence of intra-molecular vibration bands. This precludes them from being solar absorbers. In fact, they have nearly the opposite properties from selective surfaces such as cermet, TiNOx, and black chrome. However, liquid receivers which approach the radiative properties of selective surfaces, can be realized through a combination of anisotropic geometries of metal nanoparticles and transparent heat mirrors. Solar selective volumetric receivers represent a paradigm shift in the manner in which solar thermal energy is harnessed and promise higher thermal efficiencies (and lower material requirements) than their surface-absorption based counterparts. In this paper, the ‘effective’ solar absorption to infrared emission ratio has been evaluated for a representative SSVR employing copper nanospheroids and Sn-In2O3 based heat mirrors. It has been found that a solar selectivity comparable to (or even higher than) cermet-based Schott receiver is achievable through control of the cut-off solar selective wavelength. Theoretical calculations show that the thermal efficiency of Sn-In2O3 based SSVR is 6 to 7% higher than the cermet-based Schott receiver. Furthermore, stagnation temperature experiments have been conducted on a lab-scale SSVR to validate the theoretical results. It has been found that higher stagnation temperatures (and hence higher thermal efficiencies) compared to conventional surface absorption-based collectors are achievable through proper control of nanoparticle concentration.
Prospects for solar cooling - An economic and environmental assessment
Publisher: Elsevier BV
Date: 05-2012
Nanofluid-based direct absorption solar collector
Publisher: AIP Publishing
Date: 05-2010
DOI: 10.1063/1.3429737
Abstract: Solar energy is one of the best sources of renewable energy with minimal environmental impact. Direct absorption solar collectors have been proposed for a variety of applications such as water heating however the efficiency of these collectors is limited by the absorption properties of the working fluid, which is very poor for typical fluids used in solar collectors. It has been shown that mixing nanoparticles in a liquid (nanofluid) has a dramatic effect on the liquid thermophysical properties such as thermal conductivity. Nanoparticles also offer the potential of improving the radiative properties of liquids, leading to an increase in the efficiency of direct absorption solar collectors. Here we report on the experimental results on solar collectors based on nanofluids made from a variety of nanoparticles (carbon nanotubes, graphite, and silver). We demonstrate efficiency improvements of up to 5% in solar thermal collectors by utilizing nanofluids as the absorption mechanism. In addition the experimental data were compared with a numerical model of a solar collector with direct absorption nanofluids. The experimental and numerical results demonstrate an initial rapid increase in efficiency with volume fraction, followed by a leveling off in efficiency as volume fraction continues to increase.
Photothermal energy conversion in liquid nanoparticle suspensions
Publisher: ASMEDC
Date: 2010
DOI: 10.1115/FEDSM-ICNMM2010-30172
Abstract: Liquid nanoparticle suspensions, popularly termed “nanofluids,” have been the subject of numerous investigations because of their interesting thermal transport properties. Their propensity to scatter and absorb electromagnetic radiation enables other applications that can take advantage of both their radiative and thermal transport properties. In particular, we are working to develop direct-absorption solar thermal collectors in which nanofluids serve to absorb incident sunlight, thus heating the fluid directly and more efficiently than conventional solar collectors. Our experimental results, in which we irradiate nanofluids with a continuous-wave laser, demonstrate that boiling can be induced at lower incident light fluxes compared to a thin layer of pure water in front of a black absorptive backing. These findings suggest that improved solar energy conversion systems can be developed, including solar-driven direct-steam generators.
Socioeconomic impacts of heat transfer research
Publisher: Elsevier BV
Date: 12-2012
Limits of selectivity of direct volumetric solar absorption
Publisher: Elsevier BV
Date: 04-2015
Small particles, big impacts: A review of the diverse applications of nanofluids
Publisher: AIP Publishing
Date: 02-01-2013
DOI: 10.1063/1.4754271
Abstract: Nanofluids—a simple product of the emerging world of nanotechnology—are suspensions of nanoparticles (nominally 1–100 nm in size) in conventional base fluids such as water, oils, or glycols. Nanofluids have seen enormous growth in popularity since they were proposed by Choi in 1995. In the year 2011 alone, there were nearly 700 research articles where the term nanofluid was used in the title, showing rapid growth from 2006 (175) and 2001 (10). The first decade of nanofluid research was primarily focused on measuring and modeling fundamental thermophysical properties of nanofluids (thermal conductivity, density, viscosity, heat transfer coefficient). Recent research, however, explores the performance of nanofluids in a wide variety of other applications. Analyzing the available body of research to date, this article presents recent trends and future possibilities for nanofluids research and suggests which applications will see the most significant improvement from employing nanofluids.
Theoretical Analysis and Testing of Nanofluids-Based Solar Photovoltaic/Thermal Hybrid Collector
Publisher: ASME International
Date: 09-2015
DOI: 10.1115/1.4030228
Abstract: Solar energy can be harvested via thermal, photovoltaic, and photovoltaic/thermal (PV/T) hybrid technologies. PV/T systems are advantageous because they utilize more of the solar spectrum and achieve a higher combined efficiency. One approach to PV/T design is to keep the operating temperature of the PV low while achieving a high temperature for the thermal absorber. Various designs of PV/T hybrids (both flat plate and concentrated) have already been proposed which utilize air or water to remove the heat from PV cells in order to enhance the overall efficiency of PV/T hybrid collector. We propose that a nanofluid can be used instead, doubling as both the heat transfer medium and an optical filter, which allows for thermal isolation of the PV and thermal receiver. Thus, unwanted IR and UV light is filtered before it hits the PV cells, which allows for higher overall efficiencies. In this study, a new design of a PV/T hybrid collector was proposed and two nanofluid filters (based on gold and silver nanoparticles) were tested with a silicon (Si) PV cell. The corresponding stagnation temperatures of PV/T hybrid collector were measured and compared with a theoretical model. The experimental measurements validate the theoretical model, giving similar results over the range of parameters tested. The silver nanofluid design achieved the highest thermal, PV and overall efficiency and both nanofluid configurations out-performed an analogous surface absorber PV/T design under similar conditions. Overall, this study shows that nanofluids represent a feasible and viable multifunctional (optical filter and heat transfer) media in PV/T solar systems.
Applicability of Nanofluids in Concentrated Solar Energy Harvesting
Publisher: ASMEDC
Date: 2010
DOI: 10.1115/ES2010-90055
Abstract: Concentrated solar energy is becoming the input for an increasing number of thermal systems [1]. Recent papers have indicated that the addition of nanoparticles to conventional working fluids (i.e. nanofluids) can improve heat transfer and solar collection [2–4]. Thermal models developed herein show that nanofluid collectors can be more efficient than conventional concentrating solar thermal technology. This work indicates that power tower schemes are the best application for taking advantage of potential nanofluid efficiency improvements. This study provides a notional design of how such a nanofluid power tower receiver might be built. Using this type of design, we show a theoretical enhancement in efficiency of up to a 10% by using nanofluids. Further, we compare the energy and revenue generated in a conventional solar thermal plant to a nanofluid one. It was found that a 100MWe capacity solar thermal power tower operating in a solar resource similar to Tucson, AZ could generate ∼$3.5 million more per year by incorporating a nanofluid receiver.
Applicability of nanofluids in high flux solar collectors
Publisher: AIP Publishing
Date: 03-2011
DOI: 10.1063/1.3571565
Abstract: Concentrated solar energy has become the input for an increasing number of experimental and commercial thermal systems over the past 10–15 years [M. Thirugnanasambandam et al., Renewable Sustainable Energy Rev. 14 (2010)]. Recent papers have indicated that the addition of nanoparticles to conventional working fluids (i.e., nanofluids) can improve heat transfer and solar collection [H. Tyagi et al., J. Sol. Energy Eng. 131, 4 (2009) P. E. Phelan et al., Annu. Rev. Heat Transfer 14 (2005)]. This work indicates that power tower solar collectors could benefit from the potential efficiency improvements that arise from using a nanofluid working fluid. A notional design of this type of nanofluid receiver is presented. Using this design, we show a theoretical nanofluid enhancement in efficiency of up to 10% as compared to surface-based collectors when solar concentration ratios are in the range of 100–1000. Furthermore, our analysis shows that graphite nanofluids with volume fractions on the order of 0.001% or less are suitable for 10–100 MWe power plants. Experiments on a laboratory-scale nanofluid dish receiver suggest that up to 10% increase in efficiency is possible (relative to a conventional fluid)—if operating conditions are chosen carefully. Lastly, we use these findings to compare the energy and revenue generated in a conventional solar thermal plant to a nanofluid-based one. It is found that a 100 MWe capacity solar thermal power tower operating in a solar resource similar to Tucson, AZ, could generate ∼$3.5 million more per year by incorporating a nanofluid receiver.
Harvesting solar thermal energy through nanofluid-based volumetric absorption systems
Publisher: Elsevier BV
Date: 10-2014
Plasmon-enhanced properties of metallic nanostructures and their application to direct solar absorption receivers
Publisher: ASME
Date: 08-07-2012
DOI: 10.1115/HT2012-58183
Experimental and numerical study on the optical properties and agglomeration of nanoparticle suspensions
Publisher: Springer Science and Business Media LLC
Date: 18-10-2013
Comparison of selective transmitters for solar thermal applications
Publisher: The Optical Society
Date: 09-05-2016
DOI: 10.1364/AO.55.003829
Characterization of a Nanofluid Volumetric Solar Absorber / Steam Generator
Publisher: ASMEDC
Date: 2011
DOI: 10.1115/ES2011-54062
Abstract: Solar thermal energy has shown remarkable growth in recent years — incorporating many new technologies into new applications [1]. Nanofluids — suspensions of nanoparticles in conventional fluids — have shown promise to make efficient volumetric-absorption solar collectors [2–4]. It has also been shown that concentrated light energy can efficiently cause localized phase change in a nanofluid [5]. These findings indicate that it may be advantageous to create a ‘direct, volumetric nanofluid steam generator’. That is, a solar collector design which could minimize the number of energy transfer steps, and thus minimize losses in converting sunlight (via thermal energy) to electricity. To study this, we use a testing apparatus where concentrated laser light at 532 nm — a wavelength very near the solar spectrum peak — is incident on a highly absorbing s le. The highly absorbing s les compared in this study are black dyes, black painted surfaces, and silver nanofluids — with de-ionized water as a base fluid. Each of these s les converts light energy to heat — to varying degrees — in a localized region. This region is monitored simultaneously with a digital camera and an infrared camera. The resulting observed temperature profile and bubble dynamics are compared for these fluids. For pure water with a black backing, some very high temperatures ( °C) are observed with a laser input of ∼75 W/cm2. Using a similar absorption potential, we observed higher temperatures in the nanofluids when compared to black dyes. A simplified boiling heat transfer analysis based on these results is also presented. We also noticed differences in bubble size and growth rates for the different s les. Overall, this study represents a proof-of-concept test for a novel volumetric, direct steam generator. These results of this test indicate that it may be possible to efficiently generate steam directly in a controlled, localized volume — i.e. without heating up passive system components.
Spatially Varying Extinction Coefficient for Direct Absorption Solar Thermal Collector Optimization
Publisher: ASME International
Date: 22-03-2012
DOI: 10.1115/1.4003679
Abstract: Direct absorption solar thermal collectors have recently been shown to be a promising technology for photothermal energy conversion but many parameters affecting the overall performance of such systems have not been studied in depth, yet alone optimized. Earlier work has shown that the overall magnitude of the extinction coefficient can play a drastic role, with too high of an extinction coefficient actually reducing the efficiency. This study investigates how the extinction coefficient impacts the collector efficiency and how it can be tuned spatially to optimize the efficiency, and why this presents a unique design over conventional solar thermal collection systems. Three specific extinction profiles are investigated: uniform, linearly increasing, and exponentially increasing with the exponentially increasing profile demonstrating the largest efficiency improvement.
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