SERIIUS R&D Highlights

Read short descriptions of some recent successes by researchers within the Solar Energy Research Institute for India and the United States (SERIIUS). The highlights cover the areas of photovoltaics (PV), concentrating solar power (CSP), and solar energy integration (SEI).

Thumbnail of two overlapping circular flags of India and the U.S.

Management: SERIIUS Fellows and Scholars — 2016

SERIIUS and the McDonnell Academy Global Energy & Environmental Partnership (MAGEEP), with funds from SunEdison, will support the fourth year of SERIIUS Fellows and Scholars.
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India's flag and America's flag superimposed on discs.

Management: SERIIUS Fellows and Scholars — 2015

SERIIUS and the McDonnell Academy Global Energy & Environmental Partnership (MAGEEP), with funds from SunEdison, will support the third year of SERIIUS Fellows and Scholars.
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India's flag and America's flag superimposed on discs.

Management: SERIIUS Fellows and Scholars — 2014

SERIIUS and the McDonnell Academy Global Energy & Environmental Partnership (MAGEEP), with funds from SunEdison, will support the second year of SERIIUS Fellows and Scholars.
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India's flag and America's flag superimposed on discs.

Management: SERIIUS Fellows and Scholars — 2013

SERIIUS, McDonnell Academy Global Energy & Environmental Partnership (MAGEEP), with SunEdison funding, have initiated our SERIIUS Visiting Fellows and Scholars Program, with seven candidates chosen in this first-year competitive process. (Full text)

PV Activity 1: Earth-Abundant PV & Advanced Processing

Chart of capacitance vs frequency, with numerous multi-colored curves generally trending with downward slope from left to right.

Metastable Behavior in Admittance Spectroscopy – CZTSSe September 2016

We clearly demonstrate the impact of a carrier-injection pretreatment on copper zinc tin sulfur-selenium in admittance spectroscopy that has a large impact on the number of defect signatures and their corresponding activation energies.
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PV-1: Demonstrating Band Tail Voltage Limitations in CZTSSe March 2016

For the first time, we clearly demonstrate that band-tail defects in CZTSSe result in reduced carrier collection at forward bias and VOC limitations through voltage-dependent external quantum efficiency analyses.
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Black-and-white cross-section image of two-layer material showing lower layer with regular vertical  columnar crystallization and thicker upper layer with more coarsely crystalline material having an irregular surface geometry.

PV-1: Thin-Film Absorber Materials: Coated CZTS Solar Cell

CZTS nano-size particles were coated onto Mo-coated glass to obtain a working photovoltaic device with 6% efficiency. (Full text)


PV-2: Optimizing the Position of Silver Nanoparticles in Plasmonic Solar Cells March 2016

Study of plasmonic effect of silver nanoparticles in pn-heterojunction solar cells comprising Earth-abundant, non-toxic nanocrystals (CZTS and Cu@AgInS2). Optimization of the position of the plasmonic nanoparticles for both direct and inverted structures.
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PV-2: All-Oxide Solar Cells: NiO/Cu2O/ZnO/SnO2 Heterojunction March 2016

Formation of pn-junction solar cells with a layer of p-type Cu2O and a layer of n-type SnO2 nanoparticles. Band-edges of the materials with respect to their Fermi energy from STS measurements were used to derive the energy band-diagram. The all-oxide inorganic heterojunction solar cells have a photo-conversion efficiency in excess to 1%.
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Plot of normalized efficiency versus time. Three colored curves representing different materials.

PV-3: Stable Perovskite Solar Cells Fabricated Under Humid Ambient Conditions January 2017

We developed a method to fabricate highly stable perovskite solar cells under high relative humidity (50%), without any encapsulation. A typical solar cell retains 80% of maximum efficiency after 1,200 hours and the material is stable for more than 2,500 hours.
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PV-3: Introducing Cu2O in p-i-n Planar Perovskite Solar Cells March 2016

Introduction of cuprous oxide (Cu2O) thin films formed by Successive Ionic Layer Adsorption and Reaction (SILAR) method as a hole-transport layer in perovskite (CH3NH3PbI3) solar cells. Formation of planar p-i-n (direct) structure heterojunction perovskite solar cells positively modifies efficiency and reliability.
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Scanning electron microscope image of the columnar titanium dioxide nanostructure.

PV-3: Scalable Synthesis of Nanostructured Dye-Sensitized Solar Cells

We developed single-step, atmospheric pressure synthesis of single-crystal, one-dimensional nanostructured thin films as absorber material. We are also developing a new hybrid donor systems for enhanced photon harvesting and minimizing recombination. (Full text)

PV Activity 2: Advanced Process / Manufacturing Technology

Schematic of carbon elimination process toward kerf recycling.

PVCore-1: Selective Carbon Elimination for Kerf Recycling September 2015

We have addressed the challenging issue of carbon contaminant removal from silicon kerf using a scalable gas-phase technology.
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Graph of reflectance versus wavelength, showing four different-colored curves representing different wafer samples. Curves are highest to the left, dropping down in the central portion of the plot, and rising again somewhat to the right.

PVCore-1: Recycling Silicon from Kerf

We completed the experimental setup to recover silicon from kerf. Carbon content in swarf was reduced (109 ppb to 105 ppb) using oxidation. We are studying the distribution of Ni in Cz and CCz wafers and started the solar cell fabrication process on CCz wafers. We achieved weighted surface reflectance of 3.6% from ARC textured surface and acceptable sheet resistance of 45–55 Ω/□. (Full text)

Two deep blue solar cell samples.  Small square cell to left, and larger square cell to right. Each sample is covered by very narrow horizontal lines and one wider vertical line.

PVCore-2: Inroads into Si-Heterojunction Device Physics

We proposed a new characterization technique—modulated electroluminescence—for determining lifetime of solar cells. We also developed a diagnostic tool using dark current-voltage measurements. (Full text)

PV Activity 3: Multiscale Modeling & Reliability

An image of colored bar chart.

PV-4: Process-to-Panel Modeling of Silicon Heterojunction Technology March 2016

Developed an end-to-end modeling framework for silicon heterojunction (HJ) solar cell technology to investigate the implication of fabrication process variability on the cell and ultimately on the module (panel) performance.
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Illustration of a stack of 8 labeled layers of a solar cell.

PV-4: Selective-Spectral and Radiative Cooling to Improve Performance and Reliability for Solar Modules December 2016

We identified the physical origins of self-heating in solar modules to parasitic sub-bandgap absorption and imperfect thermal radiation and proposed the corresponding cooling schemes—selective-spectral and radiative cooling.
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Plot showing colored bands from blue to green to yellow from left to right, with various zones labeled for crystal and thin-film types.

PV-4: Prediction and Management of Point Defects for Improved Performance of PV Semiconductors December 2016

A DFT / SRH model run in collaboration with WUStL identified the most detrimental defects to carrier lifetime in SnS. Carrier lifetimes improved from <100 ps in thin films to >3 ns in bulk crystals with targeted defect engineering.
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Plot of photoluminescence intensity versus time of tin sulfide films. Four colored curves that radiate downward and generally to the right from a point at the top left of the plot.

PV-4: Predictive Phase and Point Defect Control in PV Semiconductors November 2015

We hypothesized that extrinsic point defects are a limiting factor in tin sulfide. Our baseline material exhibits about 100 ns minority-carrier lifetime. We grew SnS using 6N pure feedstock and observed luminescence decays > 1 ns—a significant improvement over the baseline.
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Plot of efficiency versus fill factor. A closed polygon shows various path segments from point to point, with each segment representing the performance trend due to the variation of a single parameter listed in a table to the right.

PV-4: Device Engineering of Perovskite Solar Cells to Achieve Near-Ideal Efficiency November 2015

The design space for further optimizing perovskite-based solar cells and the practical limits of efficiency are not well known. To address these issues, we identify the detailed balance performance limits, identify the physical mechanisms that contribute to sub-optimal performance of current perovskites, and suggest schemes to further improve the performance.
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Block diagram of stack of various colored layers making up a bifacial tandem cell.  Blue and red arrows indicate the movement of direct and scattered light, respectively.

PV-4: HIT-Perovskite Bifacial Tandem to Produce Output Power > 330 W/m2 November 2015

We analyze a novel Si heterojunction-perovskite (HIT-PVK) bifacial tandem cell that uses direct light as well as the albedo. Using state-of-the-art sub-cells, the bifacial tandem yields ~330 W/m2, which is 30% higher compared to a conventional HIT-PVK tandem under standard solar illumination.
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Plot of electrical conductivity (0.1 to 1000 S/m on log scale) versus temperature (0 to 1000 K). aMoBT curve closely tracks experimental data, with high peak around 300 S/m at 50 K and sloping down to 1 S/m at 1000 K. A second curve (BoltzTraP) starts at 0.1 S/m and 100 K and generally trends upward to 30 S/m at 500 K.

PV-4: aMoBT—ab initio Model for Calculating Mobility Using Boltzmann Transport August 2015

We developed a new, first-principles model to directly calculate electronic transport properties (e.g., mobility, conductivity, Seebeck coefficient) of semiconductors. (Full text)

Graph of Effective Lifetime versus Open Circuit Voltage

PV-4, PVCore-2: A Multiprobe Analysis to Triangulate the HIT Cell Parameters May 2015

We developed a systematic characterization framework to extract key parameters in HIT solar cells. (Full text)

Experimental data plot of capacitance (y axis) versus voltage (x axis). Three nearly coincident curves that show a hockey-stick trend, gradually increasing nearly linearly from left to right, then hooking sharply upward to nearly vertical on the right side. The three curves represent 100 hertz (blue), 1 kilohertz (green), and 10 kilohertz (red) data.

PV-4: Integrated Modeling

We characterized i09nversion charge in HIT cells using a multi-probe approach that involves I-V and C-V measurements, and illustrated that many features of dark I-V correlate well with C-V measurements. We also developed a comprehensive modeling framework, well calibrated with experimental results from literature, to understand / interpret perovskite-based solar cells and suggest further optimization schemes. (Full text)

Illustration of device structure showing contact, emitter, buffer, and absorber layers.

PV-4: A Multiprobe Analysis to Identify the Performance Bottlenecks in HIT Cell

We developed a systematic characterization framework to extract key parameters in HIT solar cells. (Full text)

Bar chart showing normalized I-V parameters after PID. Left-hand blue bars are for Willow Glass and right-hand red bars are for no Willow Glass.

PV-5: Avoiding PID of Installed and Operating PV Modules in the Field January 2017

Reliability is one of the primary factors dictating the projected PV electricity cost ($/kWh). PV reliability is critical to project developers, to quantify long-term performance and to increase confidence of investors and financial or insurance backers. This work addresses one of the major reliability issues—Potential-Induced Degradation (PID)—of already installed PV modules in the field.1
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Plot of Pmax degradation rate versus six different conditions.

PV-5: Reliability Survey of PV Modules in India January 2017

A comprehensive field survey of PV modules located in different climatic zones in India was undertaken to obtain degradation rates (% reduction in power per year). The main factors found to affect degradation are: climate, module quality, and installation practice.
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Box-and-whisker plot of Pmax degradation rate versus four performance parameters (Pmax, FF, Voc, Isc) in India.

PV-5: Comparing the Reliability of PV Modules in USA and India January 2017

In this bi-national project, we have studied and compared the performance and reliability of c-Si PV modules in the field in the USA and India. This provides an important comparison as to what effects are due to climate, and what are due to other "local" considerations.
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Graph of frequency (0-50) vs degradation rate (0-5), with blue vertical bars in roughly bell shape centered around 1.2

PV-5: Reliability of Modules Deployed in the Field in India December 2016

We performed a survey of over 1,000 modules in the field in different climatic zones of India. This extensive survey yielded performance and reliability data, enabling a scientific analysis of degradation mechanisms.
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Graph of delta QE vs. wavelength. Spectral irradiance curve at top, and four other color-coded sample curves below.

PV-5: Artificial Dust Deposition Using Water as Carrier Solvent December 2016

We developed a method to replicate the natural process of dust deposition on the solar modules in a laboratory environment using deionized water (DI) water as a carrier solvent. DI water is used as a carrier solvent because water, in the natural environment, is present in the form of moisture and dew drops that causes dust deposition and hence leads to cementation of dust over the surface.
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Thumbnail of chart, Accumulated Damage on y axis and Time on x axis. Seven curves rising from lower left to upper right, each labeled with a city name.

PV-5: Climate Specific Thermomechanical Fatigue of PV Module Solder Bonds May 2016

We found that the rate of solder thermomechanical fatigue damage varied significantly depending on deployment location. We also determined the number of accelerated thermal cycles to impart an equivalent amount of damage.
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Graphic that shows levelized cost of electricity split into two components: a performance component (i.e., dollars per kilowatt) and a reliability and durability component (i.e., hours).

PV-5: PV Reliability: Database and Lifetime Prediction

We are developing a comprehensive reliability database for the lifetime prediction of PV technologies, especially in the context of the environment of India and the United States.
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Plot that has price on y axis and dates along x axis. Green curve shows five spikes above a lower baseline of the curve.

PV-5: Cost-Effective and Energy-Efficient PV DC Systems for Commercial Applications

Our analysis, which predicts the cost- and energy-efficient use of DC solar-power systems in commercial buildings, is being validated in India using rooftop PV for DC-powered buildings.
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Graph of mobility vs. temperature. Five curves, four of which curve downward from left to right and one that climbs slightly from left to right.

PV-6: Alloying ZnS to Create High-Performing Transparent Conducting Material December 2016

We identified the most promising n-type ZnS-based TCM as 6.25% Al-doped ZnS, with the optimal combination of physical stability, transparency, and electrical conductivity (3,830 S cm-1 at n=1.0x1021 cm-3 and 300 K). Mobility in this material is limited by ionized impurity scattering at high carrier concentrations.
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x-y Image that shows numerous peak-to-valley curves along horizontal scan lines

PV6: VHF Plasma Etching of Patterned PMMA September 2016

We generated large-area regular micro/nano-size patterns in PMMA on flexible ultrathin glass substrates by means of nano imprint lithography and subsequent VHF plasma etching.
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Illustration of gray-colored cylinder with a tear-drop shape, with '330 degrees' label at apex of the shape

PV6: Encapsulation with Ultralow Permeability September 2016

A single graphene layer embedded in a flexible polymer reduces its water vapor transmission rate (WVTR) by up to a million-fold. We demonstrated large-area, transparent, graphene-embedded polymers with a WVTR as low as 10−6 g/m2/day.

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PV-6: Influence of Soil Composition/Color on the Performance of PV Modules in India March 2016

Soil samples collected from the surface photovoltaic modules installed in six locations of India have different current or performance losses, for identical surface soiling density, depending on the mineral composition/color in the respective soil types. (Full text)

Illustration of optical losses on a soiled photovoltaic module. Six circles representing dust sit on top of a light blue glass layer above a darker blue solar cell layer. Orange arrow indicates incoming solar radiation that penetrates or is reflected from various materials and interfaces.

PV-6: Spectral and Angular Losses of Soiled PV Modules in India and the USA November 2015

We have done extensive spectral and angular loss characterizations and modeling for soiled photovoltaic modules using naturally and artificially deposited field soil samples collected from various locations in India and the U.S.
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Illustration of water vapor being blocked by new hybrid barrier material

PV-6: Enhanced Water-Vapor Blocking for Photovoltaic Cells May 2015

We synthesized a new, hybrid barrier material to protect photovoltaic active layers. It comprises block co-polymer (PS-P2VP) and hygroscopic nanoparticles (MgO). The hybrid structure enhances the barrier properties—hydrophobic polystyrene (PS) layers block most water, and what water makes it through is scavenged by hygroscopic MgO nanoparticles in poly-2-vinylpyridine (P2VP) domains. (Full text)

Photograph showing three rows of blue square solar panels. Panels in left portion are labeled "cleaned" and panels in right portion are labeled "soiled."

PV-6: Solar PV Performance in Harsh Climates: Dust and Soiling Mitigation Research

We developed a unique solar PV module soiling test station that is being deployed to collect and analyze dust samples, test commercially developed PV module coatings, and develop and evaluate new coatings based on nanotechnology approaches. (Full text)

Illustration of junctionless cell with metal/insulator/semiconductor carrier-selective contacts.

PV-6: A High-Efficiency Low-Cost Manufacture of Multijunction Solar Cell

We propose disruptive multi-material solar cells with junctionless metal/insulator/semiconductor (MIS) carrier-selective contacts fabricated on a Si substrate with efficiencies approaching ~39% with substantially lower cost of manufacturing. (Full text)

Plot that shows logarithm scale on y axis and Q vector on x axis. Four curves are shown that all trend downward from upper left to lower right. Some curves have some upward spikes that are labeled and highlighted with arrows.

PV-6: New Polymer Nanocrystal Hybrid Architectures for High-Performance Photovoltaic Encapsulants

Current conventional encapsulants have several significant problems, and we are developing new materials using polymer and nanocrystals to overcome their shortcomings while also improving their properties. (Full text)

CSP Activity 1: High-Temperature, High-Pressure, Closed-Cycle CO2 Brayton

Thumbnail of chart, Radiative Total on y axis and Emissivity on x axis. Three curves rising from lower left to upper right, showing effect of tube diameter.

CSP-1: Radiative Heating of Supercritical Carbon Dioxide Flowing through Tubes May 2016

We characterized convection and radiation heat transfer in simultaneously developing laminar flow of s-CO2 in tubes. This study showed that for certain physical and geometric conditions, neglecting radiative heat transfer—particularly the participation of s-CO2 in thermal transport—can lead to large errors in predicting wall temperature, which affects lifetime and cost.
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Color-coded temperature distribution on tube

CSP-1: High-Temperature Supercritical Carbon Dioxide Coupled Receiver Analysis September 2015

A new coupling method that combines optical, thermal-fluid, and structural analyses has been developed and implemented for the analysis of high-temperature pressurized receivers. (Full text)

Schematic of solarized supercritical carbon dioxide recompression power cycle with thermal storage

CSP-1: Technoeconomic Study of Solarized s-CO2 Power Cycles September 2015

Performed the first comprehensive technoeconomic analysis of alternative solar-driven supercritical CO2 (s-CO2) power cycles. (Full text)

Plot of Efficiency versus Net Specific Work at five different temperatures

CSP-1: Control and Load Regulation Aspects of CO2 Brayton Cycles May 2015

We developed a framework for the control and regulation aspects of CO2 Brayton cycles for solar and non-solar power plants using a relatively unconventional coordinate system involving two thermodynamic path functions, namely, efficiency and specific work output. (Full text)

Diagram of various labeled shapes that represent the components of a typical power cycle.

CSP-1: Optimization of CO2-based Cycles

CO2-based cycles can be can be used in both Brayton and Rankine cycles. Low-side pressure and expansion ratio are the key parameters in optimizing the cycle efficiency for a given source temperature. (Full text)

Bar chart with vertical axis of Annual Average Efficiency and horizontal axis of Aperture Area. Bars for aperture areas of 1, 4, and 9 m2.

CSP-2: Heliostat Field Efficiency Variations

We studied the annual field efficiency of a 1-m2 and a 4-m2 receiver with a range of heliostats. (Full text)

CSP Activity 2: Low-Temperature, Organic Rankine Cycle

Photo of honeycomb structure.

CSPCore-2: Numerical and Experimental Evaluation of Ceramic Honeycombs for Thermal Energy Storage January 2017

Novel compositions of mullite- and chromite-based ceramic honeycombs were developed for high-temperature thermal storage application. The materials have shown favorable performance for use in high-temperature thermal energy storage. (Full text)

An image of a graph

CSP-3: Greater Specular Reflectance for ORC Collector and Optical Materials March 2016

Demonstrated the new alloy design approach involving substitution of Sn by Al in Cu-Sn-based single-phase Cu41Sn11 alloy to enhance the specular reflectance property. In particular, bulk Cu-Sn-Al intermetallic alloy-based solar reflectors with 80%-83% specular reflectance were developed.
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Plot of cost of energy returns versus installed cost for nameplate power for PV and CSP plants. Three circles for Andesol, Solana, and Crescent Dunes CSP plants. Arrows for PV trend upward and to the right, indicating range of hours.

CSP-4: PV and CSP: Why Hybrids Make Sense November 2015

Our comparative analysis of the strengths and weaknesses of photovoltaics (PV) and concentrating solar power (CSP) generation shows that a hybridization may be able to merge the best of both worlds by splitting the solar spectrum and sending the optimum wavelengths to PV and CSP.
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Plot of load (0 to 0.6) versus time of day (0 to 24 hours) for February. Two peaks around 0.25 load at 6 and 20 hours, with lower loads (0.10 to 0.15) plotted between these times.

CSP-4: Micro-CSP Developing Hybrid Mini-Grid Design August 2015

We developed a design and analysis dynamic simulation tool for optimizing micro-concentrating solar power hybridized with photovoltaics and backup fuel sources in islanded mini-grid applications. (Full text)

3D illustration showing roughly cylindrical gray object with various protrusions along the central perimeter.  Red circle on top with red arrow pointing into the cylinder. Blue rectangle in central region of the object, with blue arrow pointing out of cylinder.

CSP-4: Optimization of Scroll Geometries for Small-Scale ORC

We developed a generalized procedure for generating optimum scroll geometries using a genetic algorithm. (Full text)

CSP Activity 3: Thermal Storage & Hybridization

Thumbnail of four vertical bars with various thicknesses of colored bands from blue, to green, to yellow, to red from bottom to top.

CSP-5: Sensitivity of Thermocline-Based Thermal Storage to Flow Disturbances May 2016

Using numerical simulation, we studied the short- and long-term effects of flow disturbances on the performance of thermocline-based thermal energy storage systems. We observed that the thermocline tank is resilient to flow disturbances for high Atwood number values and oscillation frequencies in the thermocline region are lower than Brunt-Väisälä frequency.
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Thumbnail of large circle with some 40 smaller circles within.

CSP-5: Numerical Analysis of Latent Heat Thermal Energy Storage using Encapsulated Phase Change Material for Solar Thermal Power Plant May 2016

We investigated transient response of a packed-bed latent heat thermal energy storage system (LHTES) in removing fluctuations in the heat transfer fluid (HTF) temperature during the charging and discharging period. To evaluate the system performance, we computed the overall effectiveness and transient temperature difference in HTF temperature in a cycle for different geometrical and operational parameters.
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Plot of h versus d showing mushroom-like structures (blue structure to left, orange structure to right, on bright green background).

CSP-5: Instability Effect on the Performance of Thermal Energy Storage November 2015

We studied the interaction of coherent structures with the thermocline and analyzed the coherent structures associated with R-T instability.
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Chart of Reynold's number versus k for different values of anisotropy parameter (seven variously colored curves form a generally wide U-shape, with a narrower U-shape in the middle of most curves).

CSP-5: Stability of Poiseuille Flow Over a Porous Layer November 2015

We found that the following key factors stabilize a system that has Poiseuille flow over a porous layer: decrease in Darcy number, increase in depth ratio, increase in anisotropy parameter, and decrease in inhomogeneity factor.
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Schematic of experimental setup, with numbers highlighting key components: 1 is valve, 2 is density interface, 3 is vortex pair, 4 is pressure tank, 5 is pressure gauge, 6 is compressor, and 7 is pipe.

CSP-5: Mixing Dynamics Across a Stratified Interface November 2015

This work re-examines the underlying physical processes and the factors controlling the interface mixing dynamics across a stratified interface.
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 Color-coded models of single-media thermocline tank.

CSP-5: Comparative Analysis of Dual- and Single- Media Thermocline Tanks for Energy Storage September 2015

Using numerical simulation, we performed a detailed thermal analysis of thermocline tanks with molten salt and quartzite rock (dual-media), and with only molten salt (single-media). Both tank designs have high thermal performance: we observed greater flow disturbance in the single-media tank, and diffusive thermal losses inside the dual-media tank. (Full text)

Image of output from analysis. Black background, with a blue to red spectrum vertically along the left side, and a vertical band in the middle of the plot that shows colored dots.

CSP-5: High-Temperature Molten-Salt Storage for Brayton Cycles

We designed and developed a research (laboratory) molten-salt-loop system for storage for Brayton cycles in concentrating solar power. (Full text)

Diagram that shows gradient from blue (bottom) to red (top) in square storage tank and small inset showing detail of phase-change material and molten salt.

CSP-5: Assessment of Thermocline Tank Energy Storage with Phase-Change Materials

An efficient reduced-order numerical model of thermocline energy storage with phase-change materials (PCMs) is integrated to system-level model of a concentrating solar power plant. A cascaded distribution of PCMs with different melting temperatures can yield to significant improvement in plant performance. (Full text)

Output from simulations: five vertical bars with leftmost bar with thin red layer at top to mostly blue below to rightmost bar with mostly red layer at top to thin blue layer at bottom. Red area increases progressively in bars from left to right.

CSP-5: Simulation of Thermocline Formation in an Experimental Molten-Salt Energy Storage System for CSP Applications

Purdue University conducted thermal analysis of the experimental thermocline tank at IISc Bangalore; simulations are performed at flow velocities below and above a flow rate that induces instability in the thermocline region to identify a stability criterion. (Full text)

Two outputs from simulations: left rectangle shows temperature profile, with red at top and blue below; right rectangle shows velocity magnitude profile.

CSP-5: Comparative Analysis of Dual- and Single-Media Thermocline Tanks for Energy Storage

We use numerical simulation to perform a detailed thermal analysis of thermocline tanks with molten solt and quartzite rock (dual media), and with only molten salt (single media). Both tank designs have high thermal performance: greater flow disturbance is observed in the single-media tank, and diffusive thermal losses inside the dual-media tank. (Full text)

Illustration of thermocline tank showing hotter (red) material at top and colder (blue) material at bottom; inset shows detail of phase-change material and salt.

CSP-5: Assessment of Thermocline Tank Energy Storage with Phase-Change Materials

An efficient reduced-order numerical model of thermocline energy storage with phase-change materials is integrated to a system-level model of a CSP plant. A cascaded distribution of PCMs with different melting temperatures can yield significant improvement in plant performance.
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Plot of tank height (vertical axis) versus temperature (horizontal axis). Five stacked roughly linear curves that slope upward from left to right contain data from experiment and from modeling.

CSP-5: System-Level Analysis of Thermocline Energy Storage

Thermocline tanks are a potential low-cost storage concept for next-generation CSP plants. We developed a new model for thermocline energy storage that is 100x faster than conventional CFD models. Low computing cost enable an advanced system-level simulation of a CSP plant with thermocline storage. (Full text)

SEI Activity 1: Roadmapping & Assessment

Circle with different-colored points representing heliostats at concentric locations around center point. Color represents annual efficiency factor for each heliostat in the layout.

Estimation of Annual Efficiency of Heliostat Field

We developed a comprehensive model to determine the annual efficiency of a heliostat field, considering various factors such as shadowing, blocking effects, and cosine effects. (Full text)

Three vertical tracks of different-colored circles from plot of equity internal rate of return vs. interest rate.

Public Finance as a Means to Promote Indigenous Manufacturing

We developed a comprehensive financial model showing that if lower-interest-rate loans with longer tenures are available to developers using Indian modules, then comparable equity internal rates of return (IRRs) can be achieved, compared to developers using imported modules. (Full text)

C-STEP logo for Center for the Study of Science, Technology and Policy

CSTEP's Session on PPP Models in the Energy Sector

CSTEP conducted an invited training session for senior government officers in the Energy Department (Government of Karnataka) on Public-Private Partnership (PPP) Financial Models in the Energy Sector. (Full text)

SEI Activity 2: Solar Energy Integration and Storage Analysis

Illustration of tower with receiver at top. Three concentric circles around base of tower and five representative heliostat mirrors.

SEI-2: Preliminary Design of Heliostat Field and Performance Analysis of Solar Tower Plants January 2017

We developed a methodology to estimate the preliminary design of a heliostat field and performance of a tower plant with storage and hybridization using an external cylindrical receiver.
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Plot of annual efficiency factor for Gemasolar field

SEI-2: Engineering Models for Solar Tower Technologies May 2015

We developed a detailed procedure to arrive at the critical parameters of solar tower technology (e.g., tower height, mirror area, receiver sizing) for a chosen capacity, storage conditions, and location of tower. (Full text)

Map of Gujarat that highlights with a green dot the more than a dozen sites having excellent data.

SEI-3: Quantifying the Reduction in Solar Generation Variability through Interconnected PV November 2015

Collection and analysis of over 1 year of observed power production data from 50 utility-scale solar plants in the state of Gujarat shows that interconnecting as few as 12 photovoltaic plants achieves the majority of the reduction of variability.
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