Low carbon fuel standards: Implementation scenarios and challenges

Performance-based low carbon fuel standards (LCFS) of the type implemented in California and being adopted in the European Union, are a promising policy approach for decarbonizing transport fuels and reducing fossil fuel use. This paper examines the efficacy of LCFS policies, along with four major challenges that threaten their effectiveness. These challenges include leakage and shuffling of greenhouse gas (GHG) emissions, impacts on energy security, increased GHG emissions due to global land use conversion (indirect land use changes), and sustainability issues associated with biofuel production. We identify complementary policies that mitigate the severity of these challenges, while noting that some of these challenges are inherent to carbon and alternative fuel policies.     

An evaluation of the alternative transport fuel policies for Turkey

The search for alternative fuels and new fuel resources is a top priority for Turkey, as is the case in the majority of countries throughout the world. The fuel policies pursued by governmental or civil authorities are of key importance in the success of alternative fuel use, especially for widespread and efficient use. Following the 1973 petroleum crisis, many users in Turkey, especially in transportation sector, searched for alternative fuels and forms of transportation. Gasoline engines were replaced with diesel engines between the mid-1970s and mid-1980s. In addition, natural gas was introduced to the Turkish market for heating in the early 1990s. Liquid petroleum gas was put into use in the mid-1990s, and bio-diesel was introduced into the market for transportation in 2003. However, after long periods of indifference governmental action, guidance and fuel policies were so weak that they did not make sense. Entrepreneurs and users experienced great economical losses and lost confidence in future attempts to search for other possible alternatives. In the present study, we will look at the history of alternative fuel use in the recent past and investigate the alternative engine fuel potential of Turkey, as well as introduce possible future policies based on experience.     

Indirect fuel use change (IFUC) and the lifecycle environmental impact of biofuel policies

A common assumption in lifecycle assessment (LCA) based estimates of greenhouse gas (GHG) benefits (or costs) of renewable fuel such as biofuel is that it simply replaces an energy-equivalent amount of fossil fuel and that total fuel consumption remains unchanged. However, the adoption of renewable fuels will affect the price of fuel and therefore affect total fuel consumption which, may increase or decrease depending on the policy regime and market conditions. Using a representative two-region model of the global oil market in which, one region implements a domestic biofuel mandate and the other does not, we show that the net change in global fuel consumption due to the policy, which we term indirect fuel use change (IFUC), can have a significant impact on the net GHG emissions associated with biofuel. If LCA-based regulations are designed to account for indirect emissions such as indirect land use change, then we argue that IFUC emissions cannot be ignored. Our work also shows how different policies can affect the environmental impact from adopting a given clean technology differently.     

The co-evolution of alternative fuel infrastructure and vehicles: A study of the experience of Argentina with compressed natural gas

In a quest for strategic and environmental benefits, the developed countries have been trying for many years to increase the share of alternative fuels in their transportation fuel mixes. They have met very little success though. In this paper, we examine the experience of Argentina with compressed natural gas. We conducted interviews with a wide range of stakeholders and analyzed econometrically data collected in Argentina to investigate the factors, economic, political, and others that determined the high rate of adoption of this fuel. A central objective of this research was to identify lessons that could be useful to developed countries in their efforts to deploy alternative fuel vehicles. We find that fuel price regulation was a significant determinant of the adoption of compressed natural gas, while, contrary to expectations, government financing of refueling infrastructure was minimal.     

E85 and fuel efficiency: An empirical analysis of 2007 EPA test data

It is well known that ethanol has less energy per unit volume than gasoline. Differences in engine design and fuel characteristics affect the efficiency with which the chemical energy in gasoline and ethanol is converted into mechanical energy, so that the change in fuel economy may not be a linear function of energy content. This study analyzes the fuel economy tests performed by the US Environmental Protection Agency (EPA) on 2007 model year E85-compliant vehicles and finds that the difference in average fuel economy is not statistically different from the differential in energy content.     

Coal production forecast and low carbon policies in China

With rapid economic growth and industrial expansion, China consumes more coal than any other nation. Therefore, it is particularly crucial to forecast China's coal production to help managers make strategic decisions concerning China's policies intended to reduce carbon emissions and concerning the country's future needs for domestic and imported coal. Such decisions, which must consider results from forecasts, will have important national and international effects. This article proposes three improved forecasting models based on grey systems theory: the Discrete Grey Model (DGM), the Rolling DGM (RDGM), and the p value RDGM. We use the statistical data of coal production in China from 1949 to 2005 to validate the effectiveness of these improved models to forecast the data from 2006 to 2010. The performance of the models demonstrates that the p value RDGM has the best forecasting behaviour over this historical time period. Furthermore, this paper forecasts coal production from 2011 to 2015 and suggests some policies for reducing carbon and other emissions that accompany the rise in forecasted coal production.     

A comprehensive review of direct carbon fuel cell technology

Fuel cells are under development for a range of applications for transport, stationary and portable power appliances. Fuel cell technology has advanced to the stage where commercial field trials for both transport and stationary applications are in progress. The electric efficiency typically varies between 40 and 60% for gaseous or liquid fuels. About 30–40% of the energy of the fuel is available as heat, the quality of which varies based on the operating temperature of the fuel cell. The utilisation of this heat component to further boost system efficiency is dictated by the application and end-use requirements. Fuel cells utilise either a gaseous or liquid fuel with most using hydrogen or synthetic gas produced by a variety of different means (reforming of natural gas or liquefied petroleum gas, reforming of liquid fuels such as diesel and kerosene, coal or biomass gasification, or hydrogen produced via water splitting/electrolysis). Direct Carbon Fuel Cells (DCFC) utilise solid carbon as the fuel and have historically attracted less investment than other types of gas or liquid fed fuel cells. However, volatility in gas and oil commodity prices and the increasing concern about the environmental impact of burning heavy fossil fuels for power generation has led to DCFCs gaining more attention within the global research community. A DCFC converts the chemical energy in solid carbon directly into electricity through its direct electrochemical oxidation. The fuel utilisation can be almost 100% as the fuel feed and product gases are distinct phases and thus can be easily separated. This is not the case with other fuel cell types for which the fuel utilisation within the cell is typically limited to below 85%. The theoretical efficiency is also high, around 100%. The combination of these two factors, lead to the projected electric efficiency of DCFC approaching 80% - approximately twice the efficiency of current generation coal fired power plants, thus leading to a 50% reduction in greenhouse gas emissions. The amount of CO₂ for storage/sequestration is also halved. Moreover, the exit gas is an almost pure CO₂ stream, requiring little or no gas separation before compression for sequestration. Therefore, the energy and cost penalties to capture the CO₂ will also be significantly less than for other technologies. Furthermore, a variety of abundant fuels such as coal, coke, tar, biomass and organic waste can be used. Despite these advantages, the technology is at an early stage of development requiring solutions to many complex challenges related to materials degradation, fuel delivery, reaction kinetics, stack fabrication and system design, before it can be considered for commercialisation. This paper, following a brief introduction to other fuel cells, reviews in detail the current status of the direct carbon fuel cell technology, recent progress, technical challenges and discusses the future of the technology.     

New vehicle fuel economy in the UK: Impact of the recession and recent policies

Interests in vehicle fuel economy have increased in the past few years with the implementations of more stringent CAFE standard in USA and mandatory carbon emission standard in the EU. We seek to understand the effects of recent policies such as restructuring of Vehicle Excise Duties and EU standard on new vehicle fuel economy in the UK. In the past few years there have been substantial fluctuations in income and fuel prices, offering an interesting testing ground to understand their impact on the demand for fuel economy in vehicles. We use a monthly dataset to find that the emission standard is the largest driver for fuel economy improvements in recent years. Also, contrary to some recent findings in Europe and in UK, we find that income has an effect and that the recession had some role in improving the fuel economy. The effects of fuel prices were relatively small. Restructuring of the VED also improved new vehicle fuel economy in the UK, but the scrappage scheme had no significant effect. Results indicate that both supply and demand side policies are effective in improving fuel economy, although quantitatively the emission standard appears more effective due to its stringency. It is also important to consider the effects of income while devising demand side policies.     

Characterization and effect of using rubber seed oil as fuel in the compression ignition engines

Vegetable oils pose some problems when subjected to prolonged usage in compression ignition engines because of their high viscosity and low volatility. The common problems are poor atomization, carbon deposits, ring sticking, fuel pump failure, etc. Converting the high viscosity vegetable oil into its blends or esters can minimize these problems. The various blends of rubber seed oil and diesel were prepared and its important properties such as viscosity, calorific value, flash point, fire point, etc. were evaluated and compared with that of diesel. The blends were then subjected to engine performance and emission tests and compared with that for diesel. It was found that 50–80% of rubber seed oil blends gave the best performance. Long run tests were conducted using optimized blend and diesel. It was found that blend fueled engine has higher carbon deposits inside combustion chamber than diesel-fueled engine. Utilization of blends requires frequent cleaning of fuel filter, pump and the combustion chamber. Hence, it is recommended that rubber seed oil–diesel blend fuel is more suitable for rural power generation.     

A review on amorphous noble-metal-based electrocatalysts for fuel cells: Synthesis,characterization, performance,and future perspective

An urgent need for cleaner energy alternatives has driven the research of fuel cells, and consequently, electrocatalysts. Noble metals such as Pt and Pd are well known as the most suitable catalysts for fuel cell reactions. However, because of their high costs, much effort has been invested to improve their efficiency. Amorphous noble metal nanoparticles are promising electrocatalysts because of their abundant uncoordinated active sites that result from their long-range disordered lattice. Researches on amorphous Pt- and Pd-based catalysts have progressed well with several different synthesis routes. This review aims to systematically study the differences, advantages, and disadvantages of these methods and the resulting characteristics, performance in fuel cell applications, and future prospects of the amorphous Pt- and Pd-based catalysts.     

Oxy‐fuel combustion technology: current status,applications, and trends

The increased level of emissions of carbon dioxide into the atmosphere due to burning of fossil fuels represents one of the main barriers toward the reduction of greenhouse gases and the control of global warming. In the last decades, the use of renewable and clean sources of energies such as solar and wind energies has been increased extensively. However, due to the tremendously increasing world energy demand, fossil fuels would continue in use for decades which necessitates the integration of carbon capture technologies (CCTs) in power plants. These technologies include oxycombustion, pre‐combustion, and post‐combustion carbon capture. Oxycombustion technology is one of the most promising carbon capture technologies as it can be applied with slight modifications to existing power plants or to new power plants. In this technology, fuel is burned using an oxidizer mixture of pure oxygen plus recycled exhaust gases (consists mainly of CO₂). The oxycombustion process results in highly CO₂‐concentrated exhaust gases, which facilitates the capture process of CO₂ after H₂O condensation. The captured CO₂ can be used for industrial applications or can be sequestrated. The current work reviews the current status of oxycombustion technology and its applications in existing conventional combustion systems (including gas turbines and boilers) and novel oxygen transport reactors (OTRs). The review starts with an introduction to the available CCTs with emphasis on their different applications and limitations of use, followed by a review on oxycombustion applications in different combustion systems utilizing gaseous, liquid, and coal fuels. The current status and technology readiness level of oxycombustion technology is discussed. The novel application of oxycombustion technology in OTRs is analyzed in some details. The analyses of OTRs include oxygen permeation technique, fabrication of oxygen transport membranes (OTMs), calculation of oxygen permeation flux, and coupling between oxygen separation and oxycombustion of fuel within the same unit called OTR. The oxycombustion process inside OTR is analyzed considering coal and gaseous fuels. The future trends of oxycombustion technology are itemized and discussed in details in the present study including: (i) ITMs for syngas production; (ii) combustion utilizing liquid fuels in OTRs; (iii) oxy‐combustion integrated power plants and (iv) third generation technologies for CO₂ capture. Techno‐economic analysis of oxycombustion integrated systems is also discussed trying to assess the future prospects of this technology. Copyright © 2017 John Wiley & Sons, Ltd.     

A comprehensive review on oxygen transport membranes: Development history,current status,and future directions

In view of its important role as raw materials in various energy and environment fields, pure oxygen has been widely required. The present cryogenic distillation, polymeric membrane and pressure swing adsorption (PSA) air separation methods are either energy-intensive or producing non-high purity oxygen. The comparative analysis of the inorganic dense ceramic-based oxygen transport membranes (OTMs) with these traditional oxygen production technologies and the H₂/O₂ production by electrolysis of water shows irreplaceable advantages. The oxygen transport mechanism has been elaborated further to reveal the theoretical basis for the development of OTMs. The dual-phase membranes that have been widely studied are divided into three types according to the conduction paths of oxygen ions and electrons. Based on a review of the different types of OTM materials experienced in the past 30 years, its applications such as oxygen-enriched combustion involving H₂ and membrane reactors have been discussed. Finally, challenges and future directions are analyzed according to potential industrial design directions and competitive technologies of OTMs.     

The impacts of carbon tax and complementary policies on Chinese economy

Under the pressure of global warming, it is imperative for Chinese government to impose effective policy instruments to promote domestic energy saving and carbon emissions reduction. As one of the most important incentive-based policy instruments, carbon tax has sparked a lively controversy in China. This paper explores the impact of carbon tax on Chinese economy, as well as the cushion effects of the complementary policies, by constructing a dynamic recursive general equilibrium model. The model can describe the new equilibrium for each sequential independent period (e.g. one year) after carbon tax and the complementary policies are imposed, and thus describe the long-term impacts of the policies. The simulation results show that carbon tax is an effective policy tool because it can reduce carbon emissions with a little negative impact on economic growth; reducing indirect tax in the meantime of imposing carbon tax will help to reduce the negative impact of the tax on production and competitiveness; in addition, giving households subsidy in the meantime will help to stimulate household consumptions. Therefore, complementary policies used together with carbon tax will help to cushion the negative impacts of carbon tax on the economy. The dynamic CGE analysis shows the impact of carbon tax policy on the GDP is relatively small, but the reduction of carbon emission is relatively large.     

Assessment of fuel cell studies with particle image velocimetry applications: A key review

Fuel cells are considered to be a promising system that is utilized in several applications and in various sectors. Particle image velocimetry is extremely practicable for the exploration of the flow field inside fuel cells and channels. This paper reviews fuel cell studies focusing on the particle image velocimetry technique in the open literature. In this regard, state-of-the-art and comparative evaluation have been investigated and are discussed. Additionally, challenges, opportunities and future direction have been studied in terms of fuel cell type, size, voltage value, current value, power output capacity, and CFD applications. It is concluded that the growing demand on fuel cells will increase system design, performance improvement and cost benefit efforts affected by the flow and design parameters and characteristics which are other important issues that could be covered using PIV methods in the future. Moreover, this review paper is expected to be a better guide for researchers, policy makers and technologists working on potential commercial applications of fuel cells in mobile and stationary platforms.     

Effect of carbon fiber paper made from carbon felt with different yard weights on the performance of low temperature proton exchange membrane fuel cells

This study employed fuel cell gas diffusion layers (GDLs) consisting of carbon fiber paper made from carbon fiber felt with different yard weights in proton exchange membrane fuel cells (PEMFCs), and investigated the relationship between the yard weight of the carbon fiber paper and the fuel cell performance and thickness of the gasket. In this paper we discuss the relationship between carbon fiber felt with different yard weights and fuel cell performance and also explore the effect of carbon fiber paper thickness, air permeability, surface resistivity, and structural study. We focused on the material used for the gas diffusion layer in this study. Carbon fiber paper made in-house in this study contained 10 wt% (all percentages are by weight unless otherwise noted) phenolic resin. When the tested area was 25 cm², the test temperature was 40 °C, the gasket thickness was 0.06 mm, and the yard weight 70 g m⁻², fuel cell current density was 1968 mA cm⁻² at a load 0.3 V. When the gasket thickness was 0.36 mm and yard weight was 190 g m⁻², fuel current density was 1710 mA cm⁻² at a load of 0.3 V.     

Environmental life cycle assessment of alternative fuels for city buses: A case study in Oujda city,Morocco

The road transport sector, particularly public transport, generates significant greenhouse gas emissions due to the excessive use of petroleum-based fuels. The use of alternative fuels with lower environmental impacts is therefore a major challenge to move towards a more sustainable public transport sector. In this context, the current study presents an environmental life cycle assessment of alternative buses, including hybrid (diesel-electricity), electric, and fuel cell buses at a city level in Oujda, Morocco. This study is perfromed according to three main outputs: total energy use by fuel type, GHG emissions, and criteria air pollutants. It is concluded that electric and fuel cell buses represent efficient and sustainable alternatives to public transport during the operational phase and their deployment in Oujda city can potentially offer significant environmental savings in terms of GHG emissions and air pollutants during both the WTT and TTW phases.     

Life cycle cost of conventional,battery electric,and fuel cell electric vehicles considering traffic and environmental policies in China

Electric vehicles (EVs) are considered a promising alternative to conventional vehicles (CVs) to alleviate the oil crisis and reduce urban air pollution and carbon emissions. Consumers usually focus on the tangible cost when choosing an EV or CV but overlook the time cost for restricting purchase or driving and the environmental cost from gas emissions, falling to have a comprehensive understanding of the economic competitiveness of CVs and EVs. In this study, a life cycle cost model for vehicles is conducted to express traffic and environmental policies in monetary terms, which are called intangible cost and external cost, respectively. Battery electric vehicles (BEVs), fuel cell electric vehicles (FCEVs), and CVs are compared in four first-tier, four new first-tier, and 4 s-tier and below cities in China. The comparison shows that BEVs and FCEVs in most cities are incomparable with CVs in terms of tangible cost. However, the prominent traffic and environmental policies in first-tier cities, especially in Beijing and Shanghai, greatly increase the intangible and external costs of CVs, making consumers more inclined to purchase BEVs and FCEVs. The main policy benefits of BEVs and FCEVs come from three aspects: government subsidies, purchase and driving restrictions, and environmental taxes. With the predictable reduction in government subsidies, traffic and environmental policies present important factors influencing the competitiveness of BEVs and FCEVs. In first-tier cities, BEVs and FCEVs already have a competitive foundation for large-scale promotion. In new first-tier and second-tier and below cities, stricter traffic and environmental policies need to be formulated to offset the negative impact of the reduction in government subsidies on the competitiveness of BEVs and FCEVs. Additionally, a sensitivity analysis reveals that increasing the mileage and reducing fuel prices can significantly improve the competitiveness of BEVs and FCEVs, respectively.     

Effect of carbon fiber cloth with different structure on the performance of low temperature proton exchange membrane fuel cells

This study uses fuel cell gas diffusion layers (GDLs) fabricated in the laboratory from carbon fiber cloth with different structure in proton exchange membrane fuel cells (PEMFCs), and investigates the relationship between the structure of the carbon fiber cloth and fuel cell performance.The paper discusses the relationship between fuel cell performance and structure of the carbon fiber cloth, and also examines the effect of the carbon fiber cloth’s thickness, air permeability, surface resistivity, XRD and elemental analysis. Carbon fiber cloth is carbonized at rates of 190, 220, 250, 280, and 310 °C min⁻¹ respectively, and the resulting carbon fiber cloth is tested in cells. When the test piece area is 25 cm², the test temperature 40 °C, the gasket thickness 0.36 mm, and the carbonization rate 280 °C min⁻¹, a fuel cell using the carbon fiber cloth achieves a current density of 1968 mA cm⁻² and a maximum power density of 633 mW cm⁻² at 0.3 V.     

The future of hydrogen – opportunities and challenges

The following article is reproduced from ‘The Hydrogen Economy: Opportunities and Challenges’, edited by Michael Ball and Martin Wietschel, to be published by Cambridge University Press in June 2009. In the light of ever-increasing global energy use, the increasing cost of energy services, concerns over energy supply security, climate change and local air pollution, this book centres around the question of how growing energy demand for transport can be met in the long term. Given the sustained interest in and controversial discussion of the prospects of hydrogen, the authors highlight the opportunities and the challenges of introducing hydrogen as alternative fuel in the transport sector from an economic, technical and environmental point of view. Through its multi-disciplinary approach the book provides a broad range of researchers, decision makers and policy makers with a solid and wide-ranging knowledge base concerning the hydrogen economy.     

Trade-off in emissions of acid gas pollutants and of carbon dioxide in fossil fuel power plants with carbon capture

This paper investigates the impact of capture of carbon dioxide (CO₂) from fossil fuel power plants on the emissions of nitrogen oxides (NO_X) and sulphur oxides (SO_X), which are acid gas pollutants. This was done by estimating the emissions of these chemical compounds from natural gas combined cycle and pulverized coal plants, equipped with post-combustion carbon capture technology for the removal of CO₂ from their flue gases, and comparing them with the emissions of similar plants without CO₂ capture. The capture of CO₂ is not likely to increase the emissions of acid gas pollutants from individual power plants; on the contrary, some NO_X and SO_X will also be removed during the capture of CO₂. The large-scale implementation of carbon capture is however likely to increase the emission levels of NO_X from the power sector due to the reduced efficiency of power plants equipped with capture technologies. Furthermore, SO_X emissions from coal plants should be decreased to avoid significant losses of the chemicals that are used to capture CO₂. The increase in the quantity of NO_X emissions will be however low, estimated at 5% for the natural gas power plant park and 24% for the coal plants, while the emissions of SO_X from coal fired plants will be reduced by as much as 99% when at least 80% of the CO₂ generated will be captured.