Energy security implications of a national low carbon fuel standard

This paper discusses the potential energy security implications of a national low carbon fuel standard (NLCFS). A low carbon fuel standard is designed to reduce greenhouse gas (GHG) emissions by targeting the fuel portion of the fuel-vehicle system. Specifically, a NLCFS would set national targets for the average carbon intensity (CI) of motor fuels, and establish a market for credits that allows fuel producers and importers to respond in a variety of ways to the signal provided by the credit price. An important method for lowering the CI of transportation is to substitute lower-carbon alternative fuels such as advanced biofuels, electricity, CNG, and H2. Despite the focus on GHGs, so long as transportation fuels remain dominated by petroleum, transportation fuel policies like a NLCFS also will be evaluated in terms of their energy security impacts. We examine the fuel substitutions that are projected to be induced by a NLCFS and consider the energy security implications of displacing higher carbon fuels, such as imported Canadian Oil Sands oil or certain imported crude oils, with lower-carbon domestic oil, biofuels, or lower carbon oil imported from other sources.     

Applying life-cycle assessment to low carbon fuel standards—How allocation choices influence carbon intensity for renewable transportation fuels

The Energy Independence and Security Act (EISA) of 2007 requires life-cycle assessment (LCA) for quantifying greenhouse gas emissions (GHGs) from expanded U.S. biofuel production. To qualify under the Renewable Fuel Standard, cellulosic ethanol and new corn ethanol must demonstrate 60% and 20% lower emissions than petroleum fuels, respectively. A combined corn-grain and corn-stover ethanol system could potentially satisfy a major portion of renewable fuel production goals. This work examines multiple LCA allocation procedures for a hypothetical system producing ethanol from both corn grain and corn stover. Allocation choice is known to strongly influence GHG emission results for corn-ethanol. Stover-derived ethanol production further complicates allocation practices because additional products result from the same corn production system. This study measures the carbon intensity of ethanol fuels against EISA limits using multiple allocation approaches. Allocation decisions are shown to be paramount. Under varying approaches, carbon intensity for corn ethanol was 36–79% that of gasoline, while carbon intensity for stover-derived ethanol was −10% to 44% that of gasoline. Producing corn-stover ethanol dramatically reduced carbon intensity for corn-grain ethanol, because substantially more ethanol is produced with only minor increases in emissions. Regulatory considerations for applying LCA are discussed.     

Gauging citizen support for a low carbon fuel standard

Since 2007, several variations of a low carbon fuel standard (LCFS) have been implemented around the world. While emerging research tends to focus on greenhouse gas emission reductions from an LCFS, no studies have assessed the policy's political acceptability—a critical component of implementation. We elicit public support for an existing LCFS in British Columbia and a hypothetical (proposed) LCFS for the rest of Canada using survey data collected from a representative sample of Canadian citizens (n=1306). Specifically, we assess: (1) citizen awareness of British Columbia's LCFS, (2) stated citizen support for the LCFS, and (3) how individual characteristics relate to levels of citizen support. We find that British Columbia's LCFS is almost unknown among British Columbia respondents, but once explained, 90% of respondents support it. We refer to this combination of low knowledge and high support as “passive support.” We find similarly broad support in all other Canadian provinces, implying that citizen opposition is unlikely in jurisdictions considering an LCFS. Statistical analysis identifies some individual characteristics associated with LCFS support, including attitudes, demographics, and contextual factors. Results indicate where policymakers might anticipate opposition if it arises due to increased policy stringency or media coverage.     

Temporal carbon intensity analysis: renewable versus fossil fuel dominated electricity systems

In order to overcome the negative effects of climate change and ensure a global low-carbon future, decarbonizing the electricity sector has been recognized as an important focus area. Internationally, policymakers use average carbon intensity (in gCO₂-e/kWh) in calculating greenhouse gas (GHG) emissions from the electricity system. However, average carbon intensity is a single rate and a fixed quantity; thus, it does not provide any information about the time-varying nature of carbon intensity. The focus of this paper is to show the usefulness of time-varying carbon intensity estimation, which can provide detailed insights into GHG emissions, and help in identifying potential emission cut opportunities from the electricity sector in order to lessen atmospheric pollution. Time-varying carbon intensity estimation (i) reveals temporal variability of carbon intensity, (ii) explores the interplay between generations and emissions, (iii) identifies peak carbon-intensive hours, and (iv) provides evidence for designing appropriate demand-side management strategies with respect to GHG emission reduction.     

Fuel economy and life-cycle cost analysis of a fuel cell hybrid vehicle

The most promising vehicle engine that can overcome the problem of present internal combustion is the hydrogen fuel cell. Fuel cells are devices that change chemical energy directly into electrical energy without combustion. Pure fuel cell vehicles and fuel cell hybrid vehicles (i.e. a combination of fuel cell and battery) as energy sources are studied. Considerations of efficiency, fuel economy, and the characteristics of power output in hybridization of fuel cell vehicle are necessary. In the case of Federal Urban Driving Schedule (FUDS) cycle simulation, hybridization is more efficient than a pure fuel cell vehicle. The reason is that it is possible to capture regenerative braking energy and to operate the fuel cell system within a more efficient range by using battery.Life-cycle cost is largely affected by the fuel cell size, fuel cell cost, and hydrogen cost. When the cost of fuel cell is high, hybridization is profitable, but when the cost of fuel cell is less than 400 US$/kW, a pure fuel cell vehicle is more profitable.     

Lignite as a fuel for direct carbon fuel cell system

Lignite, also known as brown coal, and char derived from lignite by pyrolysis were investigated as fuels for direct carbon solid oxide fuel cells (DC-SOFC). Experiments were carried out with 16 cm² active area, electrolyte supported solid oxide fuel cell (SOFC), using pulverized solid fuel directly fed to DC-SOFC anode compartment in a batch mode, fixed bed configuration. The maximum power density of 143 mW/cm² was observed with a char derived from lignite, much higher than 93 mW/cm² when operating on a lignite fuel. The cell was operating under electric load until fuel supply was almost completely exhausted. Reloading fixed lignite bed during a thermal cycle resulted in a similar initial cell performance, pointing to feasibility of fuel cell operation in a continuous fuel supply mode. The additional series of experiments were carried out in SOFC cell, in the absence of solid fuels, with (a) simulated CO/CO₂ gas mixtures in a wide range of compositions and (b) humidified hydrogen as a reference fuel composition for all cases considered. The solid oxide fuel cell, operated with 92%CO + 8%CO₂ gas mixture, generated the maximum power density of 342 mW/cm². The fuel cell performance has increased in the following order: lignite (DC-SOFC) < char derived from lignite (DC-SOFC) < CO + CO₂ gas mixture (SOFC) < humidified hydrogen (SOFC).     

Catalysis and oxidation of carbon in a hybrid direct carbon fuel cell

The hybrid direct carbon fuel cell (HDCFC), combining molten carbonate fuel cell and solid oxide fuel cell technology, is capable of converting solid carbon directly into electrical energy without intermediate reforming. Here, we report the investigation of the HDCFC with yttria stabilized zirconia (YSZ) electrolyte, NiO-YSZ anode and lanthanum strontium manganite (LSM) cathode using the eutectic mixture of 62 mol% Li₂CO₃ and 38 mol% K₂CO₃. An open circuit voltage (OCV) of 0.71 V at 800 °C is recorded without the carbonate which increases to 1.15-1.23 V in the presence of the carbonate at the same temperature. In addition, the cell's OCV is enhanced not only by the thermal history but also by the carbonate, which is in excess of 1.57 V after the high temperature treatment. Electrochemical performance analysis indicates a suitable amount of the carbonate enhanced the carbon oxidation. With 1 mm robust thick electrolyte and commercial carbon, the cell (1.13 cm² active area) generates the peak density of 50 mW cm⁻² at 800 °C. There are significant losses from electrolyte resistance, which would be overcome by the application of a thinner electrolyte.     

Evaluation of carbon materials for use in a direct carbon fuel cell

The direct carbon fuel cell (DCFC) employs a process by which carbon is converted to electricity, without the need for combustion or gasification. The operation of the DCFC is investigated with a variety of solid carbons from several sources including some derived from coal. The highly organized carbon form, graphite, is used as the benchmark because of its availability and stability. Another carbon form, which is produced at West Virginia University (WVU), uses different mixtures of solvent extracted carbon ore (SECO) and petroleum coke. The SECO is derived from coal and both this and the petroleum coke are low in ash, sulfur, and volatiles. Compared to graphite, the SECO is a less-ordered form of carbon. In addition, GrafTech, Inc. (Cleveland, OH) supplied a well-fabricated baked carbon rod derived from petroleum coke and conventional coal–tar binder. The open-circuit voltage of the SECO rod reaches a maximum of 1.044 V while the baked and graphite rods only reach 0.972 V and 0.788 V, respectively. With this particular cell design, typical power densities were in the range of 0.02–0.08 W cm⁻², while current densities were between 30 and 230 mA cm⁻². It was found that the graphite rod provided stable operation and remained intact during multi-hour test runs. However, the baked (i.e., non-graphitized) rods failed after a few hours due to selective attack and reaction of the binder component.     

Implications of local lifecycle analyses and low carbon fuel standard design on gasohol transportation fuels

State and regional policies, such as low carbon fuel standards (LCFSs), increasingly mandate that transportation fuels be examined according to their greenhouse gas (GHG) emissions. We investigate whether such policies benefit from determining fuel carbon intensities (FCIs) locally to account for variations in fuel production and to stimulate improvements in FCI. In this study, we examine the FCI of transportation fuels on a lifecycle basis within a specific state, Minnesota, and compare the results to FCIs using national averages. Using data compiled from 18 refineries over an 11-year period, we find that ethanol production is highly variable, resulting in a 42% difference between carbon intensities. Historical data suggests that lower FCIs are possible through incremental improvements in refining efficiency and the use of biomass for processing heat. Stochastic modeling of the corn ethanol FCI shows that gains in certainty due to knowledge of specific refinery inputs are overwhelmed by uncertainty in parameters external to the refiner, including impacts of fertilization and land use change. The LCA results are incorporated into multiple policy scenarios to demonstrate the effect of policy configurations on the use of alternative fuels. These results provide a contrast between volumetric mandates and LCFSs.     

Identifying the main uncertainty drivers of energy security in a low-carbon world: The case of Europe

This analysis contributes to recent efforts to better understand the evolution of energy security in a low-carbon world. Our objective was to assess how energy security may change over the course of the century, and to what extent these changes depend on the uncertainty of the factors that drive the evolution of energy systems, including future technologies, improved energy efficiency, fossil fuel resources and markets, and economic growth. To this end, we focused on Europe and on a set of energy security indicators based on three perspectives: sovereignty, robustness and resilience. A database of scenarios allowed us to account for the large uncertainties surrounding the determinants of future energy systems. We then analyzed the way energy security indicators evolve over time, and how their trajectories vary across scenarios. We identified the indicators that vary the most between scenarios, i.e., the indicators whose future evolution is the most uncertain. For these indicators, we performed an analysis of variance to estimate the contribution of each driver to the uncertainty of the indicators. The paper shows that the European double target of significantly decreasing CO₂ emissions and increasing the security of the supply of energy may be difficult to reach. Nevertheless, some levers could facilitate the transition to a low-carbon society while improving energy security, or by limiting its degradation. The results emphasize not only the importance of policies in favor of low or zero carbon technologies in power generation but also the differences in their contributions to the complete uncertainty of the indicators. Policies promoting energy efficiency also play a role but only in the resilience of TPES. These policies are thus important levers for mitigating the negative impacts of climate policies on energy security.     

A comparison of the environmental benefits of bagasse-derived electricity and fuel ethanol on a life-cycle basis

The energetic utilisation of agricultural residues is considered to be an important element in any strategy to achieve renewable energy targets. In the approximately 80 cane-sugar producing countries there is potential to make better use of the fibrous residue known as bagasse. Subject to improved energy efficiency, sugar producers could supply energy either as “green”, co-generated electricity, or as fuel ethanol through cellulose hydrolysis followed by fermentation. This paper compares their projected environmental benefits from a life-cycle perspective, using South African data. Mass and energy analyses were prepared for the two systems and a base case (producing sugar with current methods), relative to the annual sugarcane production on one hectare. In both cases, the environmental burdens avoided by replacing an equivalent amount of fossil energy were included. The results obtained confirm that for all the impact categories considered, both “bioenergy” products result in environmental benefits. The co-generation option results in lower energy-related emissions (i.e. lower global warming, acidification and eutrophication potentials), whereas the fuel ethanol option is preferred in terms of resource conservation (since it is assumed to replace oil not coal), and also scores better in terms of human and eco-toxicity if assumed to replace lead-bearing oxygenates.     

Border carbon adjustments: Addressing emissions embodied in trade

Approximately one fourth of global emissions are embodied in international trade and a significant portion flows from non-carbon-priced to carbon-priced economies. Border carbon adjustments (BCAs) figure prominently as instruments to address concerns arising from unilateral climate policy. Estimating the volume of emissions that could be potentially taxed under a BCA scheme has received little attention until now. This paper examines how a number of issues involved in the implementation of BCAs can affect their ability to cover emissions embodied in trade and thus address carbon leakage. These issues range from ensuring compliance with trade provisions and assumptions on the carbon intensity of imports, to determining which countries are included and whether intermediate and final demand are considered. Here we show that the volume of CO₂ captured by a scheme that involved all Annex B countries could be significantly reduced due to these issues, particularly by trade provisions, such as the principle of ‘best available technology’ (BAT). As a consequence, the tariff burdens faced by non-Annex B parties could dwindle considerably. These findings have important policy implications, as they question the effectiveness and practicalities of BCAs to reduce carbon leakage and alleviate competitiveness concerns, adding further arguments against their implementation.     

Biomass to power conversion in a direct carbon fuel cell

Direct carbon fuel cells (DCFC) offer clear advantages over conventional power generation systems including higher conversion efficiency, low emissions and production of a near pure CO₂ exit stream which can be easily captured for storage. When operated on biomass-derived fuels and combined with carbon capture and storage they have the potential to be a carbon negative technology. Currently most studies relating to DCFC's focus on the use of synthetic high purity fuels. Although of significant academic interest, the high energy requirements for the production of such fuels and high cost would negate the advantages offered by DCFCs over conventional combustion technologies that can produce power from lower-grade fuels. A number of industrial processes (such as pyrolysis or gasification) can produce high carbon containing and low cost chars from biomass sources. This paper describes the operation of a novel solid state direct carbon fuel cell operated on two such commercially available bio-mass derived chars, an agricultural waste derived bio-char used for soil enrichment and coconut char used for the processing of ceramics. Chemical analysis (ICP, XRF), X-ray diffraction and thermo-gravimetric analysis have been used to characterise the fuels. Testing on small button cells showed that it is possible to operate fuel cells directly on low grade unprocessed chars. Although initial power densities were low, significant improvements to cell materials and designs can lead to practical devices. Overall the stability of the fuel cell materials in contact with bio-chars appeared to be good with no phase decomposition of any material observed.     

US electric industry response to carbon constraint: a life-cycle assessment of supply side alternatives

This study explores the boundaries of electric industry fuel switching in response to US carbon constraints. A ternary model quantifies how supply side compliance alternatives would change under increasingly stringent climate policies and continued growth in electricity use. Under the White House Climate Change Initiative, greenhouse gas emissions may increase and little or no change in fuel-mix is necessary. As expected, the more significant carbon reductions proposed under the Kyoto Protocol (1990—7% levels) and Climate Stewardship Act (CSA) (1990 levels) require an increase of some combination of renewable, nuclear, or natural gas generated electricity. The current trend of natural gas power plant construction warrants the investigation of this technology as a sustainable carbon-mitigating measure. A detailed life-cycle assessment shows that significant greenhouse gas emissions occur upstream of the natural gas power plant, primarily during fuel-cycle operations. Accounting for the entire life-cycle increases the base emission rate for combined-cycle natural gas power by 22%. Two carbon-mitigating strategies are tested using life-cycle emission rates developed for US electricity generation. Relying solely on new natural gas plants for CSA compliance would require a 600% increase in natural gas generated electricity and almost complete displacement of coal from the fuel mix. In contrast, a 240% increase in nuclear or renewable resources meets the same target with minimal coal displacement. This study further demonstrates how neglecting life-cycle emissions, in particular those occurring upstream of the natural gas power plant, may cause erroneous assessment of supply side compliance alternatives.     

Framework for the analysis of the low-carbon scenario 2020 to achieve the national carbon Emissions reduction target: Focused on educational facilities

Since the increase in greenhouse gas emissions has increased the global warming potential, an international agreement on carbon emissions reduction target (CERT) has been formulated in Kyoto Protocol (1997). This study aimed to develop a framework for the analysis of the low-carbon scenario 2020 to achieve the national CERT. To verify the feasibility of the proposed framework, educational facilities were used for a case study. This study was conducted in six steps: (i) selection of the target school; (ii) establishment of the reference model for the target school; (iii) energy consumption pattern analysis by target school; (iv) establishment of the energy retrofit model for the target school; (v) economic and environmental assessment through the life cycle cost and life cycle CO₂ analysis; and (vi) establishment of the low-carbon scenario in 2020 to achieve the national CERT. This study can help facility managers or policymakers establish the optimal retrofit strategy within the limited budget from a short-term perspective and the low-carbon scenario 2020 to achieve the national CERT from the long-term perspective. The proposed framework could be also applied to any other building type or country in the global environment.     

Mechanism for carbon direct electrochemical reactions in a solid oxide electrolyte direct carbon fuel cell

The carbon direct electrochemical reactions in a solid oxide electrolyte direct carbon fuel cell (DCFC) are investigated experimentally with CH₄-deposited carbon at the anode as fuel. The surface morphology of the anode cross-sections is characterized using a scanning electron microscope (SEM), the elemental distribution using an energy dispersive spectrometer (EDS) and an X-ray photoelectron spectroscopy (XPS), and the deposited carbon microstructures using a Raman spectrometer. The results indicate that all the carbon deposited on the yttrium-stabilized zirconium (YSZ) particle surfaces, the Ni particle surfaces, as well as the three-phase boundary, can participate in the electrochemical reactions during the fuel cell discharging. The direct electrochemical reactions for carbon require the two conditions that the O²⁻ in the ionic conductor contact with a carbon reactive site and that the released electrons are conducted to the external circuit. The electrochemical reactions for the deposited carbon are most difficult on the Ni particle surfaces, easier on the YSZ particle surfaces and easiest at the three-phase boundary. Not all the carbon deposited in the anode participates in the direct electrochemical reactions. The deposited carbon and the O²⁻ in the YSZ react to form the double-bonded adsorbed carbonyl group CO.     

Electrochemical performance of different carbon fuels on a hybrid direct carbon fuel cell

In this work, three processed carbon fuels including activated carbon, carbon black and graphite have been employed to investigate influence of the chemical and physical properties of carbon on the HDCFC performance in different anode atmospheres at 650–800 °C. The results reveal that the electrochemical activity is strongly dependent on crystalline structure, thermal stability and textural properties of carbon fuels. The activated carbon samples demonstrate a better performance with a peak power density of 326 mW cm^?2 in CO₂ at 750 °C, compared to 147 and 59 mW cm^?2 with carbon black and graphite samples, respectively. Compared to the ohmic resistance, the polarization resistance plays a more dominated role in the cell performance. When replacing N₂ by CO₂ purge gas, the power density is the strongly temperature dependent due to the Boudouard reaction.     

Benefits of using carbon nanotubes in fuel cells: a review

A carbon nanotube (CNT) is a nanoscale cylindrical tube formed from a single atomic layer of carbon atoms. CNTs are known to possess several unique characteristics, including high thermal and electrical conductivity, superior mechanical strength and chemical stability, as well as a high surface area. These characteristics, in addition to the fundamental advantages of being a carbon material, cause CNTs to be a favorable candidate for fuel cell applications. In this current assessment, past findings in relation to CNTs are summarized. Additionally, future prospects for microscopic study of CNTs are also presented. Copyright © 2016 John Wiley & Sons, Ltd.     

Carbon anode in direct carbon fuel cell

Direct carbon fuel cell (DCFC) is a kind of high temperature fuel cell using carbon materials directly as anode. Electrochemical reactivity and surface property of carbon were taken into account in this paper. Four representative carbon samples were selected. The most suitable ratio of the ternary eutectic mixture Li₂CO₃–K₂CO₃–Al₂O₃ was determined at 1.05:1.2:1(mass ration). Conceptual analysis for electrochemical reactivity of carbon anode shows the importance of (1) reactive characteristics including lattice disorder, edge-carbon ratio and the number of short alkyl side chain of carbon material, which builds the prime foundation of the anodic half-cell reaction; (2) surface wetting ability, which assures the efficient contact of anode surface with electrolyte. It indicates that anode reaction rate and DCFC output can be notably improved if carbon are pre-dispersed into electrolyte before acting as anode, due to the straightway shift from cathode to anode for CO₃²⁻ provided by electrolyte soaked in carbon material.     

Sensitivity analysis of temperature uncertainty in an aircraft PEM fuel cell

Nowadays, growing interest in the application of renewable energy sources has led to a rapid development of more environmentally sustainable and green thinking applications. The application of fuel cell technology to aircraft propulsion and/or auxiliary energy supply is becoming of great interest for undoubted advantages in terms of pollution emissions, noise reduction and lower dependency on oil price and availability. In 2006 European Commission founded the ENFICA-FC project, coordinated by Politecnico di Torino, whose aim was to develop new all-electric and more-electric aircraft concepts and to directly prove the feasibility of such designs by flying an all-electric general aviation aircraft powered by hydrogen fuel cells. Reliability of fuel cell system is a very important aspect for the safety of these aircraft, but experimental data concerning fuel cell systems in aeronautics are still unavailable to scientific community. This paper presents the research activity done by authors to support the design of “fuel cell aircrafts” from the failure analysis point of view; classic approaches to structural reliability are here applied to rank the importance of the failures of sensors used by fuel cell control logic in order to support the definition of accurate Failure Mode, Effects and Criticality Analysis (Risk matrix).