Hawaii Natural Energy Institute Research Articles

Optimizing Electric Vehicle Battery Life: A Machine Learning Approach for Sustainable Transportation

Electric vehicles (EVs) are becoming increasingly popular, due to their beneficial environmental effects and low operating costs. However, one of the main challenges with EVs is their short battery life. This study presents a comprehensive approach for predicting the Remaining Useful Life (RUL) of Nickel Manganese Cobalt-Lithium Cobalt Oxide (NMC-LCO) batteries. This research utilizes a dataset derived from the Hawaii Natural Energy Institute, encompassing 14 individual batteries subjected to over 1000 cycles under controlled conditions. A multi-step methodology is adopted, starting with data collection and preprocessing, followed by feature selection and outlier elimination. Machine learning models, including XGBoost, BaggingRegressor, LightGBM, CatBoost, and ExtraTreesRegressor, are employed to develop the RUL prediction model. Feature importance analysis aids in identifying critical parameters influencing battery health and lifespan. Statistical evaluations reveal no missing or duplicate data, and outlier removal enhances model accuracy. Notably, XGBoost emerged as the most effective algorithm, providing near-perfect predictions. This research underscores the significance of RUL prediction for enhancing battery lifecycle management, particularly in applications like electric vehicles, ensuring optimal resource utilization, cost efficiency, and environmental sustainability.

Synthesis of Transition Metal Carbide Catalysts for Vanadium Redox Flow Batteries

Vanadium redox flow batteries (VRFBs) proposed by Skyllas-Kazacos’ group in the 1980s [1] have recently attracted considerable attention for large-scale energy storage due to their desirable features such as flexible and safe design, high efficiency, and long cycle life. Graphite or carbon materials have been the most common catalysts for VRFBs [2]. However, they often show limited activity and reversibility. This issue may be circumvented with the development of new and efficient catalysts. Transition metal carbides are regarded as attractive candidates because they possess good electronic conductivity, low cost, high abundance, and outstanding thermal and chemical stabilities [3]. However, transition metal carbides fabricated by traditional carbothermal reaction methods exhibit a small specific surface area and inevitable aggregation at high reaction temperatures.A transition metal carbide fabrication process is under development at Hawaii Natural Energy Institute, which favors the formation of nano-sized particles that are expected to possess a large specific surface area. Figure 1a shows X-ray diffraction patterns for graphite as carbon source and the resulting vanadium carbide. The dominant phase is V8C7 and the particle size is approximately 50 nm. As shown in Figure 1b, cathodic currents for both electrodes in 3 M H2SO4 are due to the hydrogen evolution reaction. Although the cathodic current remarkably increases for graphite in 1 M (V2++V3+) + 3 M H2SO4 in Figure 1c, a significant anodic current is not detected indicating that the reversibility of the graphite toward the V2+/V3+ redox reactions is poor. In contrast, anodic and cathodic currents substantially increase on vanadium carbide, signifying an improvement in catalytic activity and reversibility toward the negative electrode reactions in comparison to graphite. The undesired hydrogen evolution reaction appears to have an important influence on the V3+ to V2+ reduction reaction. This influence was removed to more clearly show the vanadium V2+/V3+ redox reactions partial currents. Figure 1d shows the catalytic activity of graphite and vanadium carbide after background current subtraction. Vanadium carbide reveals more pronounced redox peaks than graphite signaling that vanadium carbide has a higher catalytic activity and enhanced reversibility toward V2+/V3+ redox reactions than graphite. The vanadium carbide composition, structure, morphology, and particle size will be tuned to improve activity.Figure 1. (a) X-ray diffraction patterns and (b, c, d) cyclic voltammograms (positive scan) for vanadium carbide and graphite. Acknowledgments Authors are grateful to the Office of Naval Research (award N00014-18-1-2127) and the Hawaiian Electric Company.

(Keynote) Corrosion of 1018 Plain Carbon Steel in Petroleum-Based and Renewable Diesel Fuel/Seawater Mixtures

The substitution of biofuels for conventional fuels can result in unexpected issues and forms of corrosion. A study was conducted on corrosion rates and the identification of corrosion products that formed on plain-carbon 1018 steel (UNS G10180) exposed in seawater/fuel mixtures of petroleum-based F-76; a 50%:50% by volume (50:50 v/v) blend of F-76 and hydro-treated renewable diesel derived from algae (HRD-76); or HRD-76 for various time durations (i.e., 3 days, 10 days, 1 month, 6 months, and 1 year). The 1018 coupons were immersed in bottles with the bottom half of the sample submerged in the seawater layer and the top half in the fuel layer. The 1018 steel has a composition which is within specifications for steels typically used for pipelines and storage vessels and tanks. Energy dispersive X-ray analyses (EDXA), X-ray diffraction (XRD), Raman spectroscopy, and FTIR spectroscopy were used to identify the corrosion products. To differentiate between abiotic electrochemical corrosion and microbiologically influenced corrosion (MIC), various permutations of filtered and unfiltered fuel and seawater combinations were used as the exposure media. A 0.22 micron filter was used to produce sterile seawater and fuel. Both aerobic and anaerobic conditions were examined. Natural, off-shore, surface seawater and synthetic seawater according to ASTM International specifications were used in the study. Hence, the test conditions were aerobic or anaerobic of the following seawater-fuel mixtures: 1) filtered seawater/filtered fuel, 2) filtered seawater/non-filtered fuel, 3) non-filtered seawater/filtered fuel, and 4) non-filtered seawater/non-filtered fuel.Corrosion rates of 1018 plain-carbon steel in the seawater-fuel mixtures were driven primarily by oxygen reduction and were highest in HRD-76, followed by the F-76/HRD-76 blend, and then F-76. This ordering corresponded to that of the dissolved-oxygen diffusion coefficients which were also ordered from highest to lowest as HRD-76, F-76/HRD-76 blend, and F-76.The region of steel in the seawater layer was most severely corroded due to the high corrosivity induced by chlorides. Corrosion was dominated by abiotic mechanisms and overshadowed any effects of MIC. At the fuel/water interface and zones submerged in the seawater layer, rust formation showed an inner black layer identified as magnetite and an outer red/yellow layer identified as lepidocrocite and goethite. The amount of magnetite in the inner layer increased with increasing content of HRD-76 in the fuels. Hence, the highest amount of magnetite was observed for the coupons exposed in HRD-76 followed by those in the HRD-76/F-76 50v:50v blend and least in the F-76. White precipitates identified as Mg(OH)2 (magnesium hydroxide), MgO (magnesium oxide), Na2CO3 (sodium carbonate), Na2CO3•H2O (thermonatrite), Na3H(CO3)2(H2O)2 (trona), CaCO3 (calcite and aragonite) formed in the fuel zone and was shown to be a consistent visual indicator for a high corrosion rate of steel. Precipitation was likely induced by a high amount of oxygen reduction (in the fuel layer) that generated OH-, which precipitated the carbonates and hydroxides. The presence of the white precipitates was most abundant on the coupons exposed to the HRD-76 and to a lesser degree on those exposed to the HRD-76/F-76 50v:50v blend, which is consistent with higher rates of oxygen diffusion and hence corrosion in the HRD-76 fuel. Acknowledgements: This work was supported under the Hawaii Natural Energy Institute’s Asia Pacific Research Initiative for Sustainable Energy Systems (APRISES) program, University of Hawaii at Manoa, Office of Naval Research (Grant Award Number N00014-13-1-0463).

How Critical Is Avoiding Critical Metals in Electrocatalysis? Lessons Learned from PGM-Free ORR Catalysts Development

The unprecedented situation with global COVID-19 pandemic exposed a significant vulnerability of world economics related to rearrangement and in some cases disappearance of supply chains. The Platinum Group Metals (PGMs) are listed critical minerals in practically all developed countries including USA, EU, UK and others. To ensure uninterrupted development of clean energy technologies, such as fuel cells and electrolysis, which are heavily depend on PGMs a significant breakthrough should be made to switch to completely PGM-free materials. Pajarito Powder in a close collaboration with world leader in MEA manufacturing IRD Fuel Cells, Hawaii Natural Energy Institute, University of Hawaii, and a number of US DOE National Labs (ANL, ORNL, LANL, NREL and other) developed under US DOE ElectroCat project Fe-N-C PGM-free catalysts for the Oxygen Reduction Reaction which are ready for commercial evaluation in some fuel cells applications [1-7].The main focus of the project was not only to synthesize ORR catalysts with the highest activity and durability, but also in the way which can be easily scaled up to the hundreds of metric tons of catalysts. Pajarito Powder used the VariPore™ method for manufacturing several sets of PGM-free catalysts (with more than 30 synthesized at the time of abstract submission) with variation of surface area, level of graphitization, particle and pore size distribution, bulk and surface chemical composition as well as hydrophobic properties. These materials were synthesized by a bottom-up approach using nitrogen-rich organic compounds, transition metal salts, and particle/pore formers (either one or series of them). Pajarito’s method include aggressive catalyst cleaning where unreacted metal nanoparticles, remaining particle/pore formers, and admixtures from acids are removed. The resulting materials are active towards ORR sites and predominantly consists of atomically dispersed Fe-Nx moieties [1-4].Pajarito’s unique capability to prepare these materials reproducibly at a 50+ grams per batch level allowed IRD Fuel Cells to produce industrial quality MEAs with reproducible performance (~300 MEAs with 25cm2 active area are made at the time of abstract submission).This oral presentation will report results of physical-chemical characterization of PGM-free catalysts, their comprehensive analysis at HNEI, modeling done by Dr. Andrei Kulikovsky, and structure-to-properties correlations obtained by our Team in collaboration with ElectroCat consortium. The critical challenges and path to overcome them will be discussed [1-3]. Acknowledgments: We would like to acknowledge the financial support from US DOE EERE under the grant DE-EE0008419 “Active and Durable PGM-free Cathodic Electrocatalysts for Fuel Cell Application” (PI: Alexey Serov).

Analyses of hydrogen energy system as a grid management tool for the Hawaiian Isles

One of the objectives of the research project at Hawaii Natural Energy Institute (HNEI) is to demonstrate long-term durability of the electrolyzer when operated under cyclic operation for frequency regulation on an Island grid system. In this paper, a Hydrogen Energy System with an electrolyzer is analyzed as a potential grid management tool. A simulation tool developed with a validated model of the hydrogen energy system and Island of Hawaii grid model is presented and employed for this investigation. The simulation study uses realistic measured solar and wind power profiles to understand what optimal electrolyzer size would be required to achieve the maximum level of grid frequency stabilization. The simulation results give insight into critical information when designing a hydrogen energy system for grid management applications and the economic impact it has when operated as a pure grid management scheme or as a limitless hydrogen production system.

Comprehensive Characterization of PGM-Free PEM Fuel Cells Using AC and DC Methods

In the past decade, a lot of efforts have been done to develop a platinum group metal-free (PGM-free), cathodic materials for proton exchange membrane fuel cells (PEMFCs) as alternative to classic Pt/C cathodes [1, 2]. At present, Fe-N-C systems are considered as one of the most promising catalysts for oxygen reduction reaction (ORR) with peak power density of about 0.5 W cm-2 [3]. The key problems in Fe-N-C electrodes relate to ORR mechanism which can proceeds through a combination of 2- and 4-electron pathways depending on operating current density, and to mass transport processes occurring in relatively thick electrodes structure. Herein, we report comprehensive study of Fe-N-C electrocatalyst integrated into cathodic catalyst layers of PEMFC with various composition configurations using AC and DC methods. We fit the physics-based impedance model, which takes into account oxygen transport in the cathode catalyst layer (CCL), gas diffusion layer (GDL) and flow-field channels to the experimental impedance spectra, and obtain main kinetic (Tafel slope) and transport parameters (proton conductivity and oxygen mass transport coefficients) of PGM-free PEMFCs in application-relevant conditions. Electrochemical evaluation has been performed using a segmented cell system and a test station developed at Hawaii Natural Energy Institute. Membrane electrode assemblies (MEAs) consisted of Fe-N-C (with varied catalyst and ionomer loadings) cathode gas diffusion electrodes (GDE), Pt anode GDE (0.1 mgPt cm-2, Alfa Aesar) and Nafion XL. The MEA was operated under galvanostatic control of the whole cell current, 80°C, 304 kPa back pressure, 100% relative humidity for the both electrodes and varied cathode stoichiometry. Details of the impedance model used in the present work have been reported in [4]. Fig. 1 a) shows a representative SEM image of the Fe-N-C GDE cross-section. The cathode thickness was found to be 120-140 μm for a sample with 3.0 mg cm- 2 catalyst loading (Fig. 1 a), while a catalyst content to 1.5 mg cm-2 caused appropriate decrease in the thickness to 70 μm. The independence of electrode thickness from ionomer content (35 vs 45 wt. %) may indicate the preferential distribution of Nafion® inside of large pores of Fe-N-C catalyst synthesized by sacrificial support method. The results obtained from AC-impedance and IV data clearly showed that the largest problem of all the electrodes is high absolute value of the kinetic Tafel slope, which varies from 100 to 250 mV/dec for current densities in the range of 0.025 to 0.4 A cm- 2. This parameter is responsible for faster decay of the cell polarization curve as compared to Pt/C-based PEMFCs. The mean proton conductivity σ p and CCL oxygen diffusivity Dox increase with the cell current density by a factor of ten (Fig. 1 b, c). Both effects take place also in Pt/C systems [5]; however, the absolute value of Dox in the Fe-N-C electrodes is an order of magnitude higher, than in the Pt/C cathodes (0.5-2.5×10- 4 cm2 s-1) [6]. The growth of σ p with current partly is due to accumulation of liquid water in the CCL; however, it may also be due to ionization of acidic molecules on carbon surface at lower cell potentials. A comparison of different CCL configurations shows that each catalyst loading value requires its own optimum ionomer content in the catalyst layer. Detailed analyses of the PGM-free PEMFC performance and its correlation with AC-impedance results will be presented and discussed. ACKNOWLEDGEMENTS We gratefully acknowledge ONR (N00014-18-1-2127), DOE EERE (DE-EE0008419) and Hawaiian Electric Company. The authors are thankful to Rohan Gokhale for preparing some GDE samples, Tina Carvalho for assisting with SEM, Günter Randolf and Jack Huizingh for valuable help in the system operation. REFERENCES S.T. Thompson, A.R. Wilson, P. Zelenay, D.J. Myers, K.L. More, K.C. Neyerlin, D. Papageorgopoulos, Solid State Ionics 319, 68-69 (2018).U. Martinez, S.K. Babu, E.F. Holby, P. Zelenay, Current Opinion Electrochem, 9, 224-232 (2018).A. Serov, K. Artyushkova, E. Niangar, C. Wang, N. Dale, F. Jaouen, M.-T. Sougrati, Q. Jia, S. Mukerjee, P. Atanassov, Nano Energy, 16, 293-300 (2015).A. Kulikovsky, J. Electroanal. Chem., 669, 28-34 (2012).T. Reshetenko, A. Kulikovsky. J. Electrochem. Soc., 163, F1100-F1106 (2016).T. Reshetenko, A. Kulikovsky, J. Electrochem. Soc., 164, F1633-F1640 (2017). Figure 1

PGM-Free Oxygen Reduction Reaction Electrocatalyst: From the Design to Manufacturing

Recently, a significant interess to the development of PGM-free catalysts for both the anode [1] and cathode [2] catalysts for the low temperature fuel cells resulted in increasing of their activity, stability and durability [3]. The activity of transition metal/nitrogen/carbon (M-N-C) materials already achieved ~30% of Pt/C. In order to further advance the research, development and commercialization of these materials Pajarito Powder, LLC utilizes the manufacturing platform under a trade mark VariPore™ which allow to control morphology and hydrophobicity/hydrophilicity, level of graphitization and final activity [4-8]. In a close collaboration with world leaders in MEA manufacturing EWII Fuel Cells these materials were integrated in high performed fuel cell MEAs, which were comprehensively tested in segmented cell at Hawaii Natural Energy Institute, University of Hawaii. All three organization are part of US DOE ElectroCat consortium.The synthetic approach is based forming the M-N-C ORR electrocatalyst from organic molecules (ranged from low molecular weight ones up to polymeric materials), which are combined with precursors of transition metals: M=Fe, Ni, Co, Mn. The main parameter which allow to control mentioned above properties is an addition to hybrid Organic-Transition Metal (TM) mixture the particles and pore forming agents (PFs). In the present work these agents were selected from the family of so called “hard templates”: silica, magnesia and a number of high surface area oxides of transition metal. The fine mixture of Organic-TM-PF was heat treated in an inert atmosphere of nitrogen in order to create the matrix of the catalyst enriched with M-Nx active sites [3]. The catalytically inactive PFs were removed from the heat-treated material by the know-how leaching process developed at Pajarito Powder.The family of Fe-N-C materials prepared at Pajarito Powder by the VariPore™ method at the scale of 200 gram per batch were provided to the EWII Fuel Cell MEA manufacturing Team, where a series of MEAs were fabricated with a variation of catalyst:ionomer ratio, deposition method and other. The electrochemical evaluation of these MEAs at low potentials (OCV-0.85V) were performed at Hawaii Natural Energy Institute using a segmented cell. The main focus of these experiments was the understanding the PGM-free ORR behavior during the MEA activation and revealing the highest intrinsic ORR activity of these catalysts. It should be mentioned that all fuel cell experiments were performed at recommended by DOE ElectroCat consortium conditions and can be compared around the ElectroCat community as well as around research groups adopted these protocols. The details on the materials synthesis and evaluation will be presented.Acknowledgments:We would like to acknowledge the financial support from US DOE EERE under the grant DE-EE0008419 “Active and Durable PGM-free Cathodic Electrocatalysts for Fuel Cell Application” (PI: Alexey Serov).

Evaluation of a 1 MW, 250 kW-hr Battery Energy Storage System for Grid Services for the Island of Hawaii

Battery energy storage systems (BESSs) are being deployed on electrical grids in significant numbers to provide fast-response services. These systems are normally procured by the end user, such as a utility grid owner or independent power producer. This paper introduces a novel research project in which a research institution has purchased a 1 MW BESS and turned ownership over to a utility company under an agreement that allowed the institution to perform experimentation and data collection on the grid for a multi-year period. This arrangement, along with protocols governing experimentation, has created a unique research opportunity to actively and systematically test the impact of a BESS on a live island grid. The 2012 installation and commissioning of the BESS was facilitated by a partnership between the Hawaii Natural Energy Institute (HNEI) and the utility owner, the Hawaiian Electric and Light Company (HELCO). After the test period ended, HELCO continued to allow data collection (including health testing). In 2018, after 8500 equivalent cycles, the BESS continues to operate within specifications. HNEI continues to provide HELCO with expertise to aid with diagnostics as needed. Details about the BESS design, installation, experimental protocols, initial results, and lessons learned are presented in this paper.

Comparison of Battery Degradations Induced By Different Synthetic Driving Cycles and Real-World Traffic Conditions

Advances in lithium ion battery pack technology have led to significant market penetration for electric vehicles (EVs), but there is still a need to develop new battery technologies, better control algorithms, and faster charging strategies to enhance further the ownership experience. Once developed, these advances must be validated. Unfortunately, fleet testing is not often an option because of the associated cost. To address this issue and permit the validation of new technologies in the laboratory quickly, many studies are relying on synthetic driving cycles to mimic the usage cells would experience under actual utilization. Among the more popular ones are the Federal Urban Driving Schedule (FUDS), a US standard; the Dynamic Stress Test (DST) which is a simplified version of the FUDS cycle; and the New European Driving Cycle (NEDC), a European standard. The ability of these cycles to replicate EV usage is usually taken for granted; whereas, to the best of our knowledge, no study has scrutinized these cycles to establish if the induced degradation is indeed comparable with what is observed from real driving data. It is proposed here to investigate the impact of the most-used, standardized driving cycles on state-of-the art lithium-ion cells and evaluate them against the impact of real driving in a laboratory-controlled environment. Different analysis techniques and metrics, such as voltage response, capacity, rate capability, and resistance, are employed to compare the most common synthetic driving cycles (FUDS, DST and NEDC) with scaled-down real driving data selected from the Hawai'i Natural Energy Institute (HNEI) in-house database. Two different sets of real driving data was used, one using a single commute in a loop and one using 25 similar commutes in a loop, to reveal any effect of traffic. This study aimed to elucidate any significant discrepancies between simulated and real driving outcomes, determine the effect of traffic conditions, and propose possible improvements.

U Hawaii fined $115,500 for lab explosion

The University of Hawaii faces a total $115,500 fine for 15 workplace safety violations after a laboratory explosion in March on the university’s Manoa campus. Postdoctoral researcher Thea Ekins-Coward, who worked for the Hawaii Natural Energy Institute, lost one of her arms in the explosion. The Hawaii Occupational Safety & Health Division (HIOSH) issued the fine and citation items on Sept. 16. Ekins-Coward was preparing a gas mixture of 55% hydrogen, 38% oxygen, and 7% carbon dioxide when an electrostatic discharge likely ignited the mixture, according to an investigation report issued in July by the University of California Center for Laboratory Safety. The gas mixture was to be used to feed bacteria to produce biofuels and bioplastics. The gases were combined in a 49-L steel tank that was designed for compressed air and not electrically grounded. The safety violations cited by HIOSH include failing to do the following: identify and

Cycle and Calendar Aging Study of Lithium-Ion Batteries in the Context of Grid-Scale Energy Storage Systems

The Hawai‘i Natural Energy Institute (HNEI) is leading a team engaged in the research, development, deployment, and analysis of grid-scale battery energy storage systems (BESS) that are designed for system control and power quality support at the generation, transmission, and distribution levels. The program aims to identify high value BESS applications at various system levels, develop control algorithms that maximize the benefit to the grid/customer and the lifetime of the BESS, and evaluate and optimize those algorithms under real world operating conditions. The focus is to deploy, operate, and validate the performance of four grid-scale BESS for various ancillary service applications on grid systems across the state. Large scale battery energy storage systems will become an important part of the electric grid in the near future and it will be essential to ensure their reliability. The objective of this project is to understand the degradation of the individual batteries to anticipate failures. Laboratory testing of advanced Li-ion battery cells is performed to support life-time analysis of technologies targeted for large-scale grid energy storage applications. HNEI’s battery testing efforts have focused on grid scale deployment lithium ion titanate battery technology which is successfully being used for a variety of purposes including frequency and power regulation of large scale wind and solar energy generation. There is currently a lack of understanding of long term performance of battery technology in general, and specifically lithium ion titanate, used under large scale, grid conditions.  This work aims to fill that gap in knowledge through laboratory scale battery testing and the development predictive lifetime models of performance of grid battery technology. Accelerated testing of identical lithium ion titanate battery technology was performed in the laboratory and those results will be used to develop predictive performance models. This model will combine existing modules [1-4] that account for single cell asymmetric degradation, single cell heat generation, string imbalance, and cell paralleling. As real world data is collected from the grid batteries, the predictive models will be compared and assessed for accuracy and ability to predict performance. This work will present preliminary results of the cycle and calendar aging long-term studies. [1] M. Dubarry, N. Vuillaume and B. Y. Liaw, J. Power Sources 186(2), (2009) 500-507. [2] M. Dubarry, C. Truchot and B.Y. Liaw, J. Power Sources 219 (2012) 204-216. [3] https://www.soest.hawaii.edu/HNEI/alawa/[4] M. Dubarry, C. Truchot, A. Devie and B. Y. Liaw, J. Electrochem. Soc 162(6), (2015) A877-A884.

(Invited) Development of a Hydrogen Energy System as a Grid Frequency Management Tool

In Hawaii, very high penetration levels of intermittent renewable energy sources such as wind and solar are causing challenges in regulation of grid frequency, and as the percentage of these intermittent resources increases can result in their curtailment. It has been postulated that, similar to a battery, the optimized use of an electrolyzer as a variable load may help regulate grid frequency and increase the penetration of renewable energy resources on the grid. The use of an electrolyzer in this way could provide an “ancillary service” to the grid that can be assigned a monetary value. This monetary value can be used to offset the cost of hydrogen production. The hydrogen in turn can be used in high value applications such as a transportation fuel. The Hawai‘i Natural Energy Institute (HNEI) is conducting research to assess the technical potential and economic value of using an electrolyzer-based hydrogen production and storage system as a demand response tool for grid management.   A 65 kg/day hydrogen energy system (H2ES) consisting of a PEM electrolyzer, 35 bar buffer tank, 450 bar compressor, and associated chiller systems, has been purchased and installed at the Hawaii Natural Energy Laboratory Hawaii Authority (NELHA) to demonstrate long-term durability of the electrolyzer under cyclic operation required for frequency regulation on an island grid system. A secondary objective is to supply hydrogen for three fuel-cell buses to be operated at Hawai‘i Volcanoes National Park (HAVO) and by the County of Hawai‘i Mass Transit Authority. The hydrogen will be transported from the production site by tube trailers to the HAVO dispensing site. A second dispensing site is located at the NELHA production site.      A comprehensive test plan has been developed to characterize the performance and the durability of the electrolyzer under dynamic load conditions and initial testing was conducted at Powertech Labs in Vancouver Canada. A main objective of the test plan is to determine the operating envelope and dynamic limits of the electrolyzer and the overall H2ES.  A long-term study shall evaluate the H2ES performance under a load profile developed from a fast acting Battery Energy Storage System (BESS) that is currently in use as a grid management tool on the Big Island grid.  These tests shall demonstrate whether the electrolyzer has the capability to effectively mitigate the impacts of intermittent solar and wind power on the grid, while continuously generating 90-80% of its designed hydrogen productioncapacity. The presentation will describe the H2ES configuration, plans for operation in the field, and results of initial tests to determine the dynamic response of the eletrolyzer and overall system

Path Dependence in Lithium-Ion Batteries Degradation - a Comparison of Cycle and Calendar Aging

The Hawai‘i Natural Energy Institute (HNEI) is leading research efforts to understand the degradation of lithium-ion batteries under two distinct projects. The first research project is focused on grid-scale battery energy storage systems (BESS) while the second project is targeting electric vehicles (EVs) and their synergy with the grid. Both applications require a combination of long cycle-life (1000 cycles or more) and long shelf-life (10 to 20 years in operation) to meet the expectations of the customers. To determine whether these durability goals are realistic or not, we performed accelerated testing of different lithium-ion battery technologies in the laboratory. For each technology, we conducted a series of cycle and calendar aging experiments. The results of these studies will be used to develop predictive performance models. The concept of accelerated aging is only valid if the degradation the cell underwent is the same than of the one it experienced in real life. In this presentation, we want to share our preliminary observations regarding the differences between cycle aging and calendar aging across the different chemistries and across the industries (EVs, BESS). Our primary objective is to showcase the different degradation pathways, whether calendar-driven or cycle-driven, which can lead to identical capacity losses. This concept is better known as path dependence and this talk will highlight its implications for the design of long-life battery systems, the laboratory testing it requires and the validity of accelerated testing strategies. [1] M. Dubarry, N. Vuillaume and B. Y. Liaw, J. Power Sources 186(2), (2009) 500-507. [2] M. Dubarry, C. Truchot and B.Y. Liaw, J. Power Sources 219 (2012) 204-216. [3] https://www.soest.hawaii.edu/HNEI/alawa/[4] M. Dubarry, C. Truchot, A. Devie and B. Y. Liaw, J. Electrochem. Soc 162(6), (2015) A877-A884.

(Invited) Development of a Hydrogen Energy System as a Grid Frequency Management Tool

It has been postulated that, similar to a battery, the optimized use of an electrolyzer as a variable load may help regulate grid frequency and increase the penetration of renewable energy resources on the grid. The use of an electrolyzer in this way could provide an “ancillary service” to the grid that can be assigned a monetary value. This monetary value can be used to offset the cost of hydrogen production. The hydrogen in turn can be used in high value applications such as a transportation fuel. The Hawai‘i Natural Energy Institute (HNEI) is conducting research to assess the technical potential and economic value of using an electrolyzer-based hydrogen production and storage system as a demand response tool for grid management. This presentation will describe the Hydrogen Energy System (HES) configuration, plans for operation in the field, and results of initial tests to determine the dynamic response of the electrolyzer and overall system.

Researcher loses arm in Hawaii explosion

Postdoctoral researcher Thea Ekins-Coward, 29, lost an arm and suffered other injuries in a lab explosion at the University of Hawaii (UH), M¯anoa, on March 16. Queen’s Medical Center, where Ekins-Coward was initially hospitalized, declined to release any information about her condition as of C&EN press time. Ekins-Coward was working for the Hawaii Natural Energy Institute (HNEI), which is a research unit within UH. HNEI researcher Jian Yu operates the lab in which the explosion happened. Yu’s research program includes developing microbial processes for producing biofuels and bioplastics from renewable feedstocks. At the time of the incident, Ekins-Coward was combining hydrogen, carbon dioxide, and oxygen gases from high-pressure cylinders into a lower pressure container, said Brian Taylor, dean of the School of Ocean & Earth Science & Technology, during a March 17 news conference. The mixture was to be used to feed bacteria. “Since 2008, when the project began, the

Catching Some Rays: Variable Generation Integration on the Island of Oahu

Starting in 2009, the Hawaii Natural Energy Institute, the Hawaiian Electric Company, and the General Electric Company, in collaboration with DOE, jointly developed and validated state-of-the-art power systems models of the Oahu and Maui electrical systems to study the operational impacts of increasing levels of wind and solar generation. These models were central to a series of coordinated, detailed technical studies which included the 2010 Hawaiian Islands Transmission Interconnection Studies (Stage I: Cable), the 2011 Oahu Wind Integration and Transmission Study (OWITS), the 2012 Hawaii Solar Integration Study (HSIS), and the 2013 Hawaiian Islands Interconnection Studies (Stage II: Grid Tie). This article focuses on key OWITS and HSIS findings for Oahu.

Investigation of path dependence in commercial lithium-ion cells chosen for plug-in hybrid vehicle duty cycle protocols

There is a growing need to explore path dependence of aging processes in batteries developed for long-term usage, such as lithium-ion cells used in hybrid electric vehicle (HEV) or plug-in hybrid vehicle (PHEV) applications that may then be “retired” to be utilized in grid applications. To better understand the foremost influences on path dependence in the PHEV context, this work aims to bridge the gap between ideal laboratory test conditions and PHEV field conditions by isolating the predominant aging factors in PHEV service, which would include, for example, the nature and frequency of duty cycles, as well as the frequency and severity of thermal cycles. These factors are studied in controlled and repeatable laboratory conditions to facilitate mechanistic evaluation of aging processes. This work is a collaboration between Idaho National Laboratory (INL) and the Hawaii Natural Energy Institute (HNEI). Commercial lithium-ion cells of the Sanyo Y type (18650 configuration) are used in this work covering two initial independent studies of path dependence issues. The first study considers how the magnitude of power pulses and charging rates affect the aging rate, while the second seeks to answer whether thermal cycling has an accelerating effect on cell aging. While this work is in early stages of testing, initial data trends show that cell aging is indeed accelerated under conditions of high discharge pulse power, higher charge rates, and thermal cycling. Such information is useful in developing accurate predictive models for estimating end-of-life conditions.

Advances in copper-chalcopyrite thin films for solar energy conversion

Promising alternatives to crystalline silicon as the basic building block of solar cells include copper-chalcopyrite thin films such as copper indium gallium diselenide, a class of thin films exhibiting bandgap-tunable semiconductor behavior, direct bandgaps and high absorption coefficients. These properties allow for the development of novel solar-energy conversion configurations like ultra-high efficiency multi-junction solar cells utilizing combinations of photovoltaic and photoelectrochemical junctions for hydrogen production. This paper discusses the current worldwide status as well as the development and optimization of copper-chalcopyrite thin films deposited onto various substrate types for different photovoltaic and photoelectrochemical applications at the Hawaii Natural Energy Institute.

Vehicle Evaluation, Battery Modeling, and Fleet-testing Experiences in Hawaii

Hawaii is an attractive proving ground for electric and hybrid vehicles (EHV) evaluation. Envisioning and embracing the needs for environmental-friendly advanced transportation technology developments, the Hawaii Center for Advanced Transportation Technologies (HCATT) and the Electrochemical Power Systems Laboratory (EPSL) at the Hawaii Natural Energy Institute (HNEI) of the University of Hawaii, are working together to promote and facilitate EHV development in Hawaii. This paper reports some of the recent activities in EHV evaluation, battery modeling, and fleet testing in the HCATT program. The fleet of EHV in this program includes battery-powered EV (BEV) and battery-fuel cell hybrid electric vehicles (HEV). We will present vehicle test results, battery modeling and simulation tool developments, and data analysis approaches that we developed and used in the program.

Deep, slim hole, diamond drilling program proves effective for geothermal assessment in Hawaii

The Hawaii State legislature, in 1988, funded a deep, slim-hole, diamond core drilling program, known as the Scientific Observation Hole (SOH) program, stimulate geothermal development and confirm the geothermal resources of This program was designed by the Hawaii Natural Energy Institute (HNEI) at the University of Hawaii at Manoa to assess the geothermal resources of the Kilauea East Rift Zone (KERZ) on the Big Island of Hawaii. The program is funded by the Hawaii Department of Business, Economic Development, and Tourism and managed by HNEI. To assess the geothermal potential of the KERZ, a fence of four holes, three of which were drilled, were sited along the long axis of the KERZ within existing Geothermal Resource Subzones. These holes were located to provide stepout drill coverage between existing and planned geothermal production wells, and to pair the SOHs with production wells to test for permeability across the rift zone. Successful drilling techniques and casing procedures were devised as the rock section became known and its characteristics noted. Above 130°C (270°F) a complex stearate was added to the drilling fluids to maintain lubricity. Above 165°C (330°F) a mixture of soda ash, high temperature polymer, complex stearate, and sepiolite virtually eliminated high torque and vibration problems frequently associated with high temperature drilling. The core and other data from the SOHs have proven to be extremely valuable for both active developers in siting production wells, and in the understanding of the subsurface geologic conditions. The first hole drilled, SOH-4, provided thermal and permeability conditions along the eastern portion of the TruelMid-Pacific Geothermal Venture's lease, and was instrumental in the proposed location of True's #2 site. SOH-4 was drilled to a total depth of 2,000.1 m (6,562 ft) and recorded bottom hole temperatures of 306.1°C (583°F) at a depth of 1,950.7 m (6,400 ft). The second hole, SOH-I, effectively defined the northern extent ofthe Puna Geothermal Venture's (PGV) HGP-AlPGV reservoir, doubled the proven reservoir size, and provided sufficient data to the lending institution for continued project funding. SOH-l was drilled to a total depth of 1,684.3 m (5,526 ft) and recorded a bottom hole temperature of 206.1°C (403°F). The third hole, SOH-2, was drilled on a PGV lease to a total depth of 2,073.2 m (6,802 ft), recorded a bottom hole temperature of 350.6°C (663°F), and may have intersected a potential reservoir at a depth of approximately 1,490 m (4,900 ft).