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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).

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.

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.

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.

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.

PV Activity 1: Earth-Abundant PV & Advanced Processing

PV-2: Improving OPV Active Layer Photostability with Perfluoroalkyl Fullerenes March 2018

A perfluoroalkyl fullerene stabilized the photobleaching rate of two organic donor molecules by a factor of 15 over blends with a traditional fullerene in unencapsulated thin films.

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.

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.

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.

PV-2: OPV Morphology and Charge Carrier Dynamics: Towards Thicker Devices August 2017

We employ a powerful new combination of techniques (STM, TRMC) to understand how OPV active-layer morphology influences device performance metrics.

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.

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%.

PV-3: Correlation of Simulation and Experiment for High-Efficiency Perovskite Solar Cell March 2018

We fabricated a highly efficient (17.5%), hysteresis-free CH3NH3PbI3-based solar cell. We also developed a SCAPS-1D simulator model to understand the loss mechanism in solar cells.

PV-3: Electrospray-Assisted Fabrication of Highly Stable and Efficient Perovskite Solar Cells March 2018

An aerosol-based method (electrospray deposition) is demonstrated to fabricate a stable CH3NH3PbI3-based perovskite layer at ambient humidity (30%–50% relative humidity). Subsequently, perovskite solar cells with 0.1-cm2 area and ̴12% efficiency were fabricated, which retain 75% of their initial efficiency (average over various devices) for 5.5 months.

PV-3: Band Structure Determination for Perovskites March 2018

We determined the electronic band structure for FA0.85Cs0.15PbI3-xBrx compositions.

PV-3: Large-Grained and High Charge-Carrier Lifetime CH3NH3PbI3 Thin Films and Implications for Solar Cells November 2017

Simple vapor annealing process in methylamine ambient to get perovskite films with very large grain (>15 μm) and uniform coverage. High charge-carrier recombination lifetime in perovskite thin films measured by microwave-detected photoconductivity.

PV-3: Hole-Selective Electron-Blocking Copper Oxide Contact for Silicon Solar Cells November 2017

A Cu2O/Si heterojunction fabricated at room temperature using a facile sputtering process was demonstrated to work as a hole-selective contact for silicon solar cells. Passivating the Cu2O/Si interface leads to an open-circuit voltage (Voc) of 528 mV, which is 200 mV higher than the state-of-the-art.

PV-3: BaBiO3: A Potential Absorber for All-Oxide Photovoltaics November 2017

BaBiO3 has been investigated as a potential photovoltaic absorber, with devices showing photo-response at 1 sun.

PV-3: Optical Properties of Zn2Mo3O8: GW+BSE Study November 2017

We computed the DFT band structure and orbital-resolved density of states for ZMO. Quasiparticle corrections have also been included within G0W0 approximation. To obtain absorption spectra, we solved the Bethe-Salpeter equation, which is a state-of-the-art methodology that captures electron-hole interactions as well.

PV-3: Flexible Perovskite Solar Cells on Ultrathin Glass: Implications of the TCO November 2017

We obtained 18.1% power conversion efficiency from a flexible perovskite solar cell (PSC) based on ultra-thin Corning® Willow® glass. Such high efficiency is achieved by studying various transparent conductive oxides (TCOs), including tin-doped indium oxide (ITO), indium zinc oxide (IZO), and aluminum-doped zinc oxide (AZO).

PV-3: Towards All-Inorganic Transport Layers for Wide-Bandgap FAPbBr3-Based Planar Photovoltaics August 2017

We report PV devices using all-inorganic transport layers under p-i-n planar device configuration using formamidinium lead tri-bromide (FAPbBr3) as an absorber. Resulted in 6.75%-efficient planar FAPbBr3 devices with open-circuit voltage of 1.23 V.

PV-3: Stable Perovskites by Aerosol Processing August 2017

We developed an electrospray technique to deposit highly stable, uniform, and moisture-resistant perovskite solar cells under high relative humidity (50%), without any encapsulation. The solar cells retain 70% of maximum efficiency after 4,000 hours.

PV-3: Radiative Thermal Annealing/In-Situ X-ray Diffraction Study of MAPbI3 August 2017

Used in-situ synchrotron XRD to comprehensively understand MAPbI3 formation/degradation dynamics during radiative thermal annealing, and the effect of such dynamics on the performance of the resulting solar cells.

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.

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.

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.

PV Activity 2: Advanced Process / Manufacturing Technology

PVCore-2: A Versatile Lifetime Measurement Technique and a Robust Characterization Framework March 2018

Developed modulated electroluminescence (MEL) technique for relaxation time measurements of different kinds of solar cells. Developed a systematic characterization framework to extract key parameters in HIT solar cells.

PVCore-2: Modulated Electroluminescence for Minority-Carrier Relaxation in HJ-Si and CIGS Cells November 2017

Relaxation time of minority carriers in solar cells is obtained from the frequency dependence of inphase (Ain) and quadrature (Aquad) components of modulated electroluminescence (MEL) using standard electrical equipment.

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.

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/□.

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.

PV Activity 3: Multiscale Modeling & Reliability

PV-4: Improving SnS Performance through Targeted Defect Management November 2017

We computationally predicted lifetime-limiting point defects in SnS—the sulfur vacancy VS and impurity-related substitutionals FeSn, CoSn, and MoSn. We also optimized growth parameters to suppress these defects and achieved >1 ns lifetime in SnS crystal samples.

PV-4: Sometimes Less is More! The Case for a Vertical Bifacial Solar Farm November 2017

Bifacial solar modules, which accept light from both faces, are an exciting photovoltaic (PV) technology for vertical integration with buildings and bridges. This first report establishes the design principle of vertical bifacial solar farms (BVFs) across the globe.

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.

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.

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.

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.

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.

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.

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. 

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.

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.

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.

PV-5: Residual Dust Benefits; BIPV vs BAPV March 2018

We accomplished the following: Experimental comparison of panels at various dust deposition densities and wind speeds; dust deposition intensities at various tilt angles; testing non-water-based cleaning mechanisms; testing hypothesis of residual dust aiding overall PV performance: and testing a whole-building BIPV/BAPV integrability index.

PV-5: Correlating IR Thermography with Electrical Degradation of PV Modules  April 2017

We correlated power degradation rate of field-aged modules to the module temperature data obtained from infrared (IR) thermography. Modules with higher temperature inhomogeneity (module ΔT) degrade at a faster rate, mainly due to faster degradation in the fill factor.

PV-5: Quantitative Determination of Performance Loss due to Cell Cracks using EL Images  April 2017

We correlated inactive areas in an electroluminescence (EL) image to the short-circuit current loss of the solar cells.

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 CID)—of already installed PV modules in the field.1

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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. 

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

CSP-1: On-Sun Testing of a Novel High-Temperature Bladed Gas Receiver and Validation Using CFD March 2018

A solar thermal receiver capable of heating sCO2 was constructed and tested on-sun. Preliminary tests using air show that the novel bladed receiver design absorbs more sunlight than conventional flat-panel receivers. The tests were validated using coupled modeling (optical/thermal/fluid).

CSP-1: On-Sun Testing of a Novel High-Temperature Bladed Supercritical CO2 (sCO2) Receiver Design November 2017

A solar thermal receiver capable of heating sCO2 has been constructed and tested on-sun. Preliminary tests using air show that the novel bladed receiver design absorbs more sunlight than conventional flat-panel receivers.

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.

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.

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.

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.

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.

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.

CSP Activity 2: Low-Temperature, Organic Rankine Cycle

Modelling and Design of a Pressurized Solar Air Receiver for Concentrating Solar Power March 2018

A Scheffler optical concentrator was geometrically modelled and ray-tracing analysis was performed to obtain input power to the receiver. A novel cavity-air-receiver with porous absorber was subjected to CFD and CHT analysis for design optimization.

CSPCore-2: Numerical Analysis of Pressurized Cavity Air Receiver in Concentrating Solar Power System March 2018

We carried out a coupled analysis of the cavity air receiver with porous absorber using the finite-element method and completed fabricating the receiver.

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.

CSPCore-3: Natural Gas Combustor as Hybrid Heating Source for Solar Thermal Loop March 2018

Developed a natural-gas-fired combustor with near-zero NOx emissions and low temperatures as a hybrid heating source for the solar thermal Brayton cycle using supercritical CO2 as working fluid.

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.

CSP-4: Solar PV Compared with ORC and Thermal Storage: Capacity Factor Insights August 2017

We describe the implications of the performance and cost of solar generation systems featuring batteries or thermal energy storage from the perspective of capacity utilization factor and levelized cost of electricity.

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.

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. 

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

We developed a generalized procedure for generating optimum scroll geometries using a genetic algorithm.

CSP Activity 3: Thermal Storage & Hybridization

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.

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.

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.

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.

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.

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.

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. 

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.

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.

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. 

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.

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.

SEI Activity 1: Roadmapping & Assessment

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. 

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.

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. 

SEI Activity 2: Solar Energy Integration and Storage Analysis

SEI-2: SAM for India: A Tool for Understanding Solar Deployment Barriers and Costs August 2017

SAM for India builds on the existing, well-known System Advisor Model platform and provides a practical financial modeling tool for the Indian context. The model and corresponding introductory webinar are publicly available.

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.

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.

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.