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DOE OSTI2022

Desulfurization and sulfur tolerant hydrogenation processes of hydrocarbon feedstocks

The present invention relates to the use of adsorbents comprising zinc oxide nanowires decorated with catalytically active metal particles for the removal of sulfur from hydrocarbon feedstocks, including the desulfurization of diesel fuels and the deep desulfurization of natural gas, and to the use of decorated zinc oxide nanowire adsorbents for the hydrogenation of naphthalene selectively to tetralin in the presence of sulfur compounds. The adsorbent comprises nickel metal particles or nickel-zinc alloy particles deposited on zinc oxide nanowires.

Sunkara, Mahendra↗

DOE OSTI2022

Fuel and fuel blend for internal combustion engine

A fuel or fuel blending agent for an internal combustion engine includes a ketone compound that is a C 4 to C 10 branched acyclic ketone, cyclopentanone, or a derivative of cyclopentanone. The ketone compound may be blended with a majority portion of a fuel selected from the group consisting of: gasoline, diesel, alcohol fuel, biofuel, renewable fuel, Fischer-Tropsch fuel, or combinations thereof. The ketone compound may be derived from biological sources. A method for powering an internal combustion engine with a fuel comprising the ketone compound is also provided.

Dec, John E.↗

DOE OSTI2022

Decarbonizing Medium & Heavy-Duty On-Road Vehicles

We analyze the decarbonization potential of medium and heavy-duty vehicles (MHDVs) across multiple vehicle classes and market segments. We evaluate the timeframe in which zero-emission vehicles (ZEVs) could achieve cost parity with conventional diesel vehicles and the implications for energy and emissions. Our results show that ZEVs can achieve cost parity with conventional vehicles by 2035 across the majority of vehicle classes and market segments. Emissions reductions range from 27% to 77% by 2050 relative to 2019 across multiple fuel cost and technology progress sensitivities. Multiple technology pathways are viable for decarbonization, including battery-electric vehicles and hydrogen fuel cell electric vehicles. This presentation is based on previous work published by NREL: Ledna, C., Muratori, M., Yip, A., Jadun, P., and Hoehne, C. 2022. Decarbonizing Medium & Heavy-Duty On-Road Vehicles: Zero-Emission Vehicles Cost Analysis. National Renewable Energy Laboratory, https://www.nrel.gov/docs/fy22osti/82081.pdf.

ADVANCED PROPULSION SYSTEMS↗

DOE OSTI2023

Hydrogen Fuel Cell Electric Bus (FCEB) Evaluations in US Public Transit Service

The National Renewable Energy Laboratory (NREL) is a Department of Energy (DOE) national laboratory focused on renewable energy and energy efficiency. NREL has evaluated alternative fuel and advanced propulsion transit buses for DOE and the U.S. Department of Transportation's Federal Transit Administration (FTA). These evaluations are focused on determining the status of fuel cell systems and the corresponding infrastructure in transit applications to help DOE and FTA assess the progress toward technology readiness. For the last 19 years NREL has evaluated FCEBs in service around the United States and in Canada. The results of these evaluations have been published in numerous reports that compare FCEB performance to conventional technology as well as document the implementation experience and lessons learned by the transit agencies and their demonstration teams. Currently, 70 fuel cell buses are in active service in the US and 66 FCEBs are in development. NREL is evaluating a subset of the active FCEBs that includes three transit agencies demonstrating 25 fuel cell electric buses in California. One bus has exceeded 35,000 hours in service and 12 have exceeded 25,000 hours. Fuel economy for the current generation of FCEBs has improved 35% over the previous generation and is double that of conventional buses. Maintenance cost for FCEBs is equivalent to diesel and BEBs. The most up-to-date performance results will be presented, including fuel economy, availability, reliability, and operational costs.

bus↗

DOE OSTI2023

Direct Conversion of Delignified Biomass into Non-Volatile Products Using Thermophilic Bacteria

Butyric acid (BA) can be used as a platform intermediate for diesel and sustainable aviation fuels (SAFs) as well as a precursor for diverse commodity chemicals for the production of polymers, fibers, solvents, and preservatives. This work presents a co-culture-based bioprocess for the production of BA from corn stover by two thermophilic bacteria, Clostridium thermocellum, a well-known efficient degrader of insoluble and oligomeric cellulosic substrates, and Clostridium thermobutyricum, a highly efficient BA producer from monomeric sugars. First, we tested the capability of C. thermocellum to deconstruct three different biomass streams from the NREL pilot plant pretreatment process -raw, deacetylated, and deacetylated and mechanically refined corn stover (DMR)-, and up to 82% solids deconstruction and 91% carbohydrate utilization were obtained when using DMR solids. Then, the sugar utilization and by-product formation capabilities on various substrates by C. thermobutyricum were compared to evaluate its potential as a co-culture partner for C. thermocellum. Model carbon sources -glucose and xylose- were compared to a mixture of substrates present in soluble DMR hydrolysate streams, and the highest cell density as well as the maximum BA titer (8.3 g/L) were observed on DMR hydrolysate. Finally, clostridial co-cultivations on DMR solids were performed to investigate the inoculation time for both organisms that enhances BA production; while C. thermocellum was always inoculated at the beginning of the cultivation, C. thermobutyricum was inoculated at 0, 36, or 72h. It was found that BA production begins immediately upon inoculation of C. thermobutyricum regardless of the inoculation time. However, higher solids deconstruction and carbohydrate utilization results (83.7 and 95.6%, respectively) were obtained when both organisms were inoculated at the beginning of the fermentation. Under those conditions, up to 2.6 g/L of BA were obtained from DMR solids after 120h of cultivation. This work provides relevant information for the sustainable production of BA using thermophilic bacteria.

bacterial co-culture↗

DOE OSTI2023

Examination of a Methane/Diesel RCCI Engine Using Pele: Preprint

Multi-fuel, advanced injection strategies have become increasingly promising as a strategy to mitigate the emissions generated from internal combustion engines. By carefully controlling the combustion phasing in-cylinder, these new multi-pulse, multi-fuel injection strategies are able to burn in the low-temperature combustion regime where both NOx and soot are not readily produced, reducing the need for extensive exhaust gas recirculation systems. In this study, we examine a reactivity-controlled compression ignition (RCCI) strategy that uses an early pre-filled methane-air mixture with low turbulence background as the low-reactivity fuel and a direct injection of four discrete dodecane jets as a surrogate for the high-reactivity diesel fuel. We use the Pele software suite, a highly optimized, exascale-ready, adaptive mesh refinement codebase to perform high-resolution numerical simulations of a scaled down, single cylinder from the RCCI engine. Here, we resolve the ignition kernels down to micrometer scales and present several statistical quantities evaluating the development of the flow and detailing the onset of ignition and subsequent flame development. Particular attention is paid to the conditions surrounding the onset of the first ignition kernels and discussing what led to the development of those conditions.

CFD↗

DOE OSTI2023

Marine Alternative Fuel Pricing, Supply, and Demand

The International Maritime Organization low sulfur fuel rules and greenhouse gas-reduction strategy may create a significant perturbation to global refinery operations, impacting volumes and prices of marine fuel globally and within the United States and incentivizing the transition to alternative fuel use. The goals of this project are to (1) enhance understanding of how very low-sulfur fuel-primarily fuel oil and diesel-and low carbon fuel requirements and promising biofuel processes will affect the marine fuel supply chain; and (2) explore how these perturbations interact with and impact indicators such as pricing, number of trips, and demand behavior, along with the potential to meet low sulfur and carbon fuel demand with biofuel supply chains, (3) merge innovative thinking in the area of marine fuels within research centers of DOE (NREL) and the U.S. Department of Transportation (Volpe). These goals will be accomplished through the combination of detailed refinery, marine fuel burn, system dynamics, and geospatially explicit linear programming models.

biofuel↗

DOE OSTI2023

Impacts of Dispatch Strategies and Forecast Errors on the Economics of Behind-the-Meter PV-Battery Systems

To assess the economic value of batteries in hybrid PV-battery systems, one must create a dispatch profile for the battery. Many analyses of battery value assume perfect forecasts of PV generation and load, determining an upper limit on the value of the battery. Prior work that accounts for forecast uncertainty often does so in the context of a single dispatch algorithm, which does not provide a baseline for comparison. Furthermore, when multiple dispatch algorithms are assessed with uncertainty, the benefits considered are for diesel generation in a microgrid, not retail rate savings. This work addresses the gaps in the literature by comparing the performance of both heuristic and optimal dispatch algorithms for retail rate savings under forecast uncertainty, and provides comparisons of the robustness of these algorithms and their associated estimates of economic value. We find that using a perfect forecast can overestimate the value of hybrid PV-battery systems between 1% and 8% compared to the reality of using a day-ahead forecast, depending on the dispatch algorithm used. Thus, accounting for forecast uncertainty in system design and analysis will significantly improve the accuracy of modeled system values.

batteries↗

DOE OSTI2023

Wet biofuel compression ignition

A compression ignition engine system allows use of hydrous fuels, in particular hydrous biofuels, with high water content (e.g., 20-85% water). The hydrous fuel is pressurized, and also preferably heated via the engine's exhaust gas, to increase its enthalpy, and is then directly injected into the engine cylinder(s) near top dead center. The system provides brake thermal efficiency increases of 20% or more versus a comparable system using conventional diesel fuel, while allowing the use of inexpensive undistilled or lightly distilled biofuels.

Wickman, David Darin↗

DOE OSTI2023

Impacts of Dispatch Strategies and Forecast Errors on the Economics of Behind-the-Meter PV-Battery Systems: Preprint

batteries↗

DOE OSTI2023

Spatio-temporal and weather characterization of road loads of electrified heavy-duty commercial vehicles across U.S. interstate roads

Adoption of battery electric vehicles (BEV) in heavy duty (HD) commercial freight transportation is difficult due to technological and economic hurdles. Beyond safety and compliance, fleet and operational logistics necessitate both high uptime and parity with diesel system productivity/Total Cost of Ownership to support widespread deployment of electric powertrains. However, relatively high energy storage costs, along with the higher weight of BEV systems, limit the viability of HD commercial freight transport to shorter-range applications where smaller batteries will serve for mission energy requirements (single operational shift). Knowing the energy consumption and operating variations of these commercial vehicle systems is crucial for effectively sizing the energy storage systems. This paper is the first in a series of studies to understand the regional specific operating design domain variations of commercial Class 8 HD trucks and the associated impact to their energy requirements. In particular, the local weather conditions are shown to influence the total vehicle energy usage. Further, the impact of temperature, pressure, and humidity changes are shown to impact the local air density. This is needed to calculate aerodynamic drag on vehicles and has been found to play a significant role in the overall performance of a vehicle. Although the methodology of calculating air density varies only slightly throughout the literature, the application to transportation has still been limited. This study provides a means by which air density can be estimated for the contiguous U.S. using the NOAA MADIS dataset. These air density estimates were then used to determine vehicle performance in varying regions of the country to highlight the importance of consideration of weather variables when monitoring vehicle performance, but also to provide recommendations based on these locales upon fleet conversion to BEVs.

Moore, Amy↗

DOE OSTI2021

Combustion studies of n-butyl acetate synthesized by a new biological process and comparisons with neat n-butyl acetate

Blending petroleum fuels with biofuels is a common approach for stemming the depletion of crude oil while also mitigating the impact of their combustion on the environment. It has recently been considered that n-butyl acetate (BA, C6H12O2, boiling point of 399K) could be a viable biofuel additive to diesel fuel. This paper reports the combustion dynamics of BA droplets in the absence of external convection. Two grades of BA were examined: one synthesized by a new process that uses a solventogenic Clostridium strain through an extractive fermentation process using n-hexadecane as the extractant (SBA); the other commercially available as a high-purity (99.9%) 'neat' BA grade produced by Fischer esterification (NBA). The mass concentration of by-products from the synthesis process amounted to approximately 6% of the total composition and included n-butanol, n-hexadecane, iso-propyl alcohol and ethyl acetate. The platform used to study the combustion of commercial and synthesized BA was an isolated droplet burning with spherical symmetry. Initial droplet diameters were fixed at 0.6 mm. Experiments were carried out in a drop tower to promote one-dimensional transport dynamics, in the standard atmosphere, and with ignition accomplished by spark discharge. Differences in droplet burning rates and flame structures were undetectable between NBA and SBA, despite the differences in burning among the SBA components individually. The results presented show that the new synthesis process for butyl acetate yields a sustainable alternative to conventional methodologies with burning characteristics that are identical to NBA in stagnant gas transport fields.

Wang, Yujie↗

DOE OSTI2023

Fuel and fuel blend for internal combustion engine

Dec, John E.↗

DOE OSTI2023

Validation of Interconnection and Interoperability of Grid-Forming Inverters Sourced by Hydrogen Technologies in View of 100% Renewable Microgrids

Grid-forming assets are required in microgrids to act as voltage-frequency masters. These grid-forming assets can operate in two modes of operation: grid-following mode and grid-forming mode. In grid-following mode of operation, these assets will follow real power and reactive power setpoints and in grid-forming mode of operation these assets will follow voltage and frequency setpoints. Traditionally, diesel generators or natural gas-based generators are widely used to act as a voltage-frequency master. However, many utilities are aiming to replace generators with grid forming-inverters supplied by solar photovoltaics (PV), batteries or fuel cells. Since grid-forming assets need a long-term reliable energy source, fuel cells are a reasonable and viable choice to supply the grid-forming inverters, but some of the challenges facing the wide deployment of grid-forming fuel cell inverters need to be addressed. Specifically, in our proposed work, we aim to focus on the interconnection and interoperability requirements of grid-forming fuel cell inverters. Currently, state-of-the-art fuel cell inverters follow the general interconnection requirements of distributed energy resources (DERs) and general interoperability requirements of DERs, but these requirements were built with PV and battery systems in mind. Fuel cells have different operational requirements, and therefore these requirements need to be appropriately modified for the grid operators to use. These additional steps add to the investment and operational cost to the grid operators. Through the ARIES platform, this proposed project aims to bridge this gap and use power hardware-in-the-loop (PHIL) and controller hardware-in-the-loop (CHIL) experiments to inform the creation of open-source interconnection and interoperability information that can aid in faster and cheaper installation and operation of grid-forming fuel cell inverters.

grid-forming↗

DOE OSTI2023

Droop Control-Based Dispatch of an Islanded Microgrid With Multiple Grid-Forming Sources

Before rotating, fossil fuel-based, synchronous generators (SGs) are phased out, in line with renewable generation goals, grid-forming (GFM) inverters are expected to parallel SGs. Primary droop control allows GFM inverters to share power without communication; however, it is necessary to dispatch GFM inverters and/or SGs with the desired output power for better energy management (e.g., one GFM inverter needs to charge the battery due to a low state of charge). Therefore, this paper develops an analytic approach to dispatching GFM inverters and SGs with the desired output power by shifting the droop intercept up/down while maintaining the same frequency operating point for improved transient stability. This concept is demonstrated through a pure hardware setup with two off-the-shelf inverters and one diesel generator under an islanded microgrid, and we provide insight on the real-world implementation of the proposed concept.

droop control↗

DOE OSTI2023

Droop Control-Based Dispatch of an Islanded Microgrid with Multiple Grid-Forming Sources: Preprint

Before rotating fossil-fuel based synchronous generators (SGs) are phased out in line with renewable goals, grid-forming (GFM) inverters are expected to parallel with SGs. Primary droop control allows them share power without communication, however, it is necessary to dispatch GFM inverters and/or SG with desired output power for better energy management (e.g., one GFM inverter needs to charge the battery due to low state-of-the charge). Therefore, this paper develops analytic approach to dispatch GFM inverters and SG with desired output power by shifting the droop intercept up/down while maintain the same frequency operating point for improved transient stability. This concept is demonstrated through pure hardware setup with two off-the-shelf inverters and one diesel generator under islanded microgrid, and we also provide insight on real-world implementation of the proposed concept.

droop control↗

DOE OSTI2023

Enabling a Sustainable Future: Zero-Emission Vehicles Cost Analysis to Inform Decarbonization Pathways

Despite being only 5% of vehicles on the road, medium- and heavy-duty vehicles (MHDVs) are the second largest contributor to transportation emissions (21%) and a major source of local air pollution disproportionally affecting disadvantaged communities. This talk summarizes a cost analysis for zero emissions vehicles (battery electric EVs and hydrogen fuel cell FCEVs) for all medium and heavy duty applications, ranging from large pick-up trucks, to delivery vans, buses, and heavy trucks. Results show that with continued improvements in vehicle and fuel technologies (in line with U.S. Department of Energy targets and vetted with industry), zero-emission vehicles (ZEVs) can reach total-cost-of-driving parity with conventional diesel vehicles by 2035 for all medium- and heavy-duty (MD/HD) vehicle classes without incentives. Assuming economics drives adoption, ZEV sales could reach 42% of all MD/HD trucks by 2030, reflecting lower combined vehicle purchase and operating costs (using real-world payback periods). Two technological solutions - battery electric vehicles (BEVs) and fuel cell electric vehicles (FCEVs) - are viable in multiple market segments, offering alternative pathways for decarbonization: a) BEVs tend to become cost-competitive for smaller trucks before 2030 and for short-haul (<500-mile) heavy trucks before 2035. b) Hydrogen FCEVs tend to become cost-competitive for long-haul (>500-mile) heavy trucks by 2035. Results are very sensitive to technology improvement trajectories, adoption decision-making, and uncertain assumptions about future freight demand, logistics, and vehicle use explored in multiple scenarios.

ADVANCED PROPULSION SYSTEMS,ENERGY PLANNING, POLIC↗

DOE OSTI2020

Optical Investigation of Catalyst Heating Operation in a Light-Duty Compression-Ignition Engine

It is well known that cold start engine operation contributes a majority of tail-pipe emissions during a vehicle drive cycle. Aftertreatment catalysts have poor conversion efficiency during this period due to low conversion efficiency at temperatures less than their light-off temperature. A late post injection strategy, with a delayed injection to increase exhaust enthalpy, can help decrease the time required to heat-up the catalyst. However, late injections into conditions with decreasing temperature and density can result in high emissions and combustion instability. In this study a three-injection strategy with a late-post injection was investigated in an optically-accessible engine. For the first two injections (pilot and main) timing and duration were held constant as the post injection timing was swept and duration varied to hold load constant, at a relevant light-load catalyst heating operating condition. Simultaneous double-pass schlieren and OH chemiluminescence data were acquired in an optically-accessible 0.4 L single-cylinder engine to understand spray characteristics and combustion behavior for #2 diesel fuel. Optical images analysis revealed higher liquid penetration and lower vaporization of the liquid fuel jet as post injection is retarded. It is also observed that retarding post injection timing to +25 CAD resulted in lower observed soot concentration in the piston bowl.

99 GENERAL AND MISCELLANEOUS↗