A combined process integration and fuel switching strategy for emissions reduction in chemical process plants

The combustion of fossil fuel to provide process heating is the major source of atmospheric pollution. Combustion products such as carbon dioxide, oxides of sulfur, oxides of nitrogen and particulates are known to be the major causes for global warming, acid rains and smog. This paper presents a combined method of fuel switching and heat exchanger network (HEN) retrofit to reduce flue gas emissions. The method is demonstrated using pre-heat train of a crude oil distillation unit as the case study. Target emissions reduction of 50% is achieved at an approximate payback period of 0.44 year on the capital investment due to the combination of the two methods.     

The effect of driving cycles and H2 production pathways on the lifecycle analysis of hydrogen fuel cell vehicle: A case study in South Korea

This study focuses on the simulation and analysis on the fuel economy of a hydrogen fuel cell vehicle, data collection and modeling to estimate greenhouse gas emission during its lifecycle. Since regenerative braking is a velocity related process, a car which is equipped with it can be significantly affected by the driving cycle. Therefore, the influence of five driving patterns on the fuel economy of a FCEV is investigated. Further prediction of life cycle emission is carried out by several hydrogen production pathways. The results indicate that the mileage of this FCEV for 1 complete charging can be extended by as much as 7% in fast shift driving mode with energy recovery of 30% during braking. The results also prove that hydrogen produced by natural gas in an on-site manner can reduce the lifecycle emission by more than 50%, comparing to that by Naphtha.     

Transitioning a bus transit fleet to hydrogen fuel: A case study of Knoxville Area Transit

The current climate crisis and recent world events, including the global economic crisis and growing concerns over the availability and cost of petroleum fuels, has sparked a global interest in developing alternative, sustainable, clean fuel technologies for the transportation sector. While a multitude of alternative fuel and vehicle technologies have been presented, hydrogen is considered by many as an option of choice. However, the mass-adoption of hydrogen presents many challenges, including appropriate refueling infrastructure supply transitions, consumer vehicle purchase behavior, and fuel costs. Early fleet adoption is one proposed strategy to transition hydrogen use in the transportation sector. Bus-transit demonstration projects have proven the technology, yet there has not been large-scale adoption by transit fleets. This paper addresses infrastructure, vehicle, and personnel needs to support the transition of a medium sized transit agency to full conversion to hydrogen fuel, using Knoxville Area Transit (KAT) as a case study. Specifically, requirements for hydrogen bus fleets, production, storage, refueling and maintenance facilities, and personnel are addressed as well as the transition strategy for implementing the technology.     

The rise and fall of oil generation in the USA: A study in institutional adaptability

After 1978, the US electric power industry more than halved oil generation of electricity. This reversed a rising trend that had accelerated with the liberalization of residual fuel oil import quotas in 1966. This paper uses detailed data on inter- utility sales filed with the US government and limited circulation statistical reports from electric utilities to appraise the changes. The changes reflect the capacity of a flexible, growing, integrated electric utility system to adapt to changing circumstances. Much of the reduction in oil use was effected by purchases of coal-generated electricity by oil-based companies on the east coast. Another major development was the introduction of new coal-fired plants to the west- south-central states. This allowed coal to take over from oil as the alternative to increasingly more expensive natural gas. In New York and California, however, gas became available to displace oil. A further more modest contribution was made by having plants that had shifted from coal to oil resume coal use.     

Economics of Wind turbine as an energy fuel saver – A case study for remote application in oman

This paper presents a study carried out to investigate the economics of wind turbine as an energy fuel saver. The load and the wind data is taken from a remote agricultural research station in Oman. Presently, the station is provided with electricity from diesel-engine generating units. The annual peak load and minimum load recorded at the site is 130 kW and 28 kW respectively. The annual average wind speed at the site is 5.7 m/s. A 50-kW wind turbine is selected to demonstrate the economic feasibility of the turbine as a fuel saver. The results show that wind energy utilization is an attractive option with total specific cost of the selected wind turbine ranges between 7.4 and 8.45 ¢/kWh at 7.55% discount rate comparing to diesel generation operating cost of 14.3 ¢/kWh, considering the capital cost of diesel units as sunk. The simple payback period of the turbine is between 5.1 and 5.4 years and discounted payback between 6.7 and 8.0 years.     

A method for detection and location of current-free spots in a fuel cell stack: Numerical study

In a fuel cell stack, the current-free spot induces the variation of potential along the end faces of the bipolar plates clamping the defective cell. Numerical model shows that measuring these voltage shapes one can identify the presence of the spot and locate position of the spot center. Possible development of spot tomography in stacks based on this technique is discussed.     

A 5 kWt catalytic burner for PEM fuel cells: Effect of fuel type,fuel content and fuel loads on the capacity of the catalytic burner

For proton exchange membrane fuel cell systems (PEMFC) integrated with fuel processors, the calorific value of reformate gases produced during the start-up phase must be recovered. An appropriate exhaust after treatment system has crucial importance for PEMFC systems. Catalytic combustion is a promising alternative regarding its total oxidation capability of low calorific value gases at low temperatures, thereby reducing environmentally hazardous emissions. The aim of the study is to develop an after treatment system using a catalytic burner with a nominal capacity of 5 kW_t, which is also adaptive to partial loads of PEM fuel cell capacity. Fuel type, fuel composition and fuel loads are important parameters determining the operating window of the catalytic burner. Precious metal based catalysts, as proved to be the most active catalysts for the oxidation of hydrocarbons, can withstand temperatures of about 1073 K without exhibiting a rapid deactivation. This is the main barrier dictating the operating window and thereby determining the capacity of the burner. In this work, 1.5% natural gas (NG) alone was found to be the upper limit to control the catalyst bed temperature below 1073 K. In the case of catalytic combustion of hydrogen–NG mixture, 7% of hydrogen with NG up to 0.6% could be totally oxidized below 1073 K. Within the experimented ranges of fuel loads, between 2.5 kW_t and 5.5 kW_t, the temperature of the catalyst bed was seen to increase with increasing the fuel load at constant fuel percentages. It has been observed that fuel type was another parameter affecting the exhaust gas temperature.     

A semi-empirical method for electrically modeling of fuel cell: Executed on a direct methanol fuel cell

In this paper, a novel semi-empirical modeling method to mathematically derive a nonlinear equivalent circuit from a special group of impedance fuel cell models is proposed. As an example, a 5-cm² direct methanol fuel cell (DMFC) was modeled by this method. The derived equivalent circuit is composed of lumped nonlinear resistors, capacitors and an inductor. The nonlinear circuit has an impedance equivalent to the target fuel cell in various operating conditions and provides a good approximation of the static and transient behaviors of the fuel cell. The equivalent circuit fuel cell model was validated by comparing its numerical simulation results with its polarization curve and the dynamic behavior of the target DMFC. These comparisons were performed while the DMFC was operating under square current pulses with different upper and low current levels.     

A quasi-Delphi study on technological barriers to the uptake of hydrogen as a fuel for transport applications—Production, storage and fuel cell drivetrain considerations

The introduction of hydrogen in transport, particularly using fuel cell vehicles, faces a number of technical and non-technical hurdles. However, their relative importance is unclear, as are the levels of concern accorded them within the expert community conducting research and development within this area. To understand what issues are considered by experts working in the field to have significant potential to slow down or prevent the introduction of hydrogen technology in transport, a study was undertaken, primarily during 2007. Three key technology areas within hydrogen transport were selected - hydrogen storage, fuel cell drivetrains, and small-scale hydrogen production - and interviews with selected experts conducted. Forty-nine experts from 34 organisations within the fuel cell, automotive, industrial gas and other related industries participated, in addition to some key academic and government figures. The survey was conducted in China, Japan, North America and Europe, and analysed using conventional mathematical techniques to provide weighted and averaged rankings of issues viewed as important by the experts. It became clear both from the interviews and the subsequent analysis that while a primary concern in China was fundamental technical performance, in the other regions cost and policy were rated more highly. Although a few individual experts identified possible technical showstoppers, the overall message was that pre-commercial hydrogen fuel cell vehicles could realistically be on the road in tens of thousands within 5 years, and that full commercialisation could take place within 10-15 years, without the need for radical technical breakthroughs. Perhaps surprisingly, the performance of hydrogen storage technologies was not viewed as a showstopper, though cost was seen as a significant challenge. Overall, however, coherent policy development was more frequently identified as a major issue to address.     

Impact of reform and privatization on consumers: A case study of power sector reform in Orissa,India

Orissa is the first state in India to have undergone reform in the power sector, with the government withdrawing its control. The model of this reform is known as the WB–Orissa model. The goal of this paper is to examine the impact of this reform on consumers of electricity, which has been measured using multiple regression models. The variables represent the parameters that consumers are most interested in, and the regression coefficients represent the weights of the corresponding variables. The data were collected using a survey methodology. The impact of reform was found to be mixed. Some groups of consumers saw benefits, while others felt a negative impact. A focus group study was conducted to identify the variables of interest to consumers of electricity. The model was used to estimate consumer benefit and was validated using primary data and structural equation modeling. The study revealed beneficial aspects of reform and areas with no benefits.     

Effects of fuel processing methods on industrial scale biogas-fuelled solid oxide fuel cell system for operating in wastewater treatment plants

The performance of three solid oxide fuel cell (SOFC) systems, fuelled by biogas produced through anaerobic digestion (AD) process, for heat and electricity generation in wastewater treatment plants (WWTPs) is studied. Each system has a different fuel processing method to prevent carbon deposition over the anode catalyst under biogas fuelling. Anode gas recirculation (AGR), steam reforming (SR), and partial oxidation (POX) are the methods employed in systems I-III, respectively. A planar SOFC stack used in these systems is based on the anode-supported cells with Ni-YSZ anode, YSZ electrolyte and YSZ-LSM cathode, operated at 800 °C. A computer code has been developed for the simulation of the planar SOFC in cell, stack and system levels and applied for the performance prediction of the SOFC systems. The key operational parameters affecting the performance of the SOFC systems are identified. The effect of these parameters on the electrical and CHP efficiencies, the generated electricity and heat, the total exergy destruction, and the number of cells in SOFC stack of the systems are studied. The results show that among the SOFC systems investigated in this study, the AGR and SR fuel processor-based systems with electrical efficiency of 45.1% and 43%, respectively, are suitable to be applied in WWTPs. If the entire biogas produced in a WWTP is used in the AGR or SR fuel processor-based SOFC system, the electricity and heat required to operate the WWTP can be completely self-supplied and the extra electricity generated can be sold to the electrical grid.     

Development of Oshawa hydrogen hub in Canada: A case study

Consumption of fossil fuels, which makes an immense contribution to greenhouse gas emissions, must be reduced. Hydrogen emerges as a unique solution to serve as fuel, energy carrier and feedstock because it is a clean, abundant, environmentally friendly and energy intensive gas. This study aims to investigate the development of a potential hydrogen hub located in Oshawa, Canada, which is aimed to provide a hydrogen infrastructure for future hydrogen economy. Numerous life cycle assessment and cost assessment studies are conducted to investigate what benefits such a hydrogen will bring to the city. The results show that fuel cell electric buses emit 89% fewer pollutants. Also, 60% of overall CO₂ reduction is possible with a gradual transition to fuel cell technology within 20 years. However, in order for hydrogen infrastructure and costs to compete with fossil fuels, high-scale projects need to be developed with governmental incentives.     

Environmental aspects of ethanol-based fuels from Brassica carinata: A case study of second generation ethanol

One of the main challenges faced by mankind in the 21st century is to meet the increasing demand for energy requirements by means of a more sustainable energy supply. In countries that are net fossil fuel importers, expectation about the benefit of using alternative fuels on reducing oil imports is the primary driving force behind efforts to promote its production and use. Spain is scarce in domestic energy sources and more than 50% of the energy used is fossil fuel based. The promotion of renewable energies use is one of the principal vectors in the Spanish energy policy. Selected herbaceous crops such as Brassica carinata are currently under study as potential energy sources. Its biomass can be considered as potential feedstock to ethanol conversion by an enzymatic process due to the characteristics of its composition, rich in cellulose and hemicellulose. This paper aims to analyse the environmental performance of two ethanol-based fuel applications (E10 and E85) in a passenger car (E10 fuel: a mixture of 10% ethanol and 90% gasoline by volume; E85 fuel: a mixture of 85% ethanol and 15% gasoline by volume) as well as their comparison with conventional gasoline as transport fuel. Two types of functional units are applied in this study: ethanol production oriented and travelling distance oriented functional units in order to reflect the availability or not of ethanol supply. E85 seems to be the best alternative when ethanol production based functional unit is considered in terms of greenhouse gas (GHG) emissions and E10 in terms of non-renewable energy resources use. Nevertheless, E85 offers the best environmental performance when travelling distance oriented functional unit is assumed in both impacts. In both functional unit perspectives, the use of ethanol-based fuels reduces the global warming and fossil fuels consumption. However, the contributions to other impact indicators (e.g. acidification, eutrophication and photochemical oxidants formation) were lower for conventional gasoline.Life Cycle Assessment (LCA) procedure helps to identify the key areas in the B. carinata ethanol production life cycle where the researchers and technicians need to work to improve the environmental performance. Technological development could help in lowering both the environmental impact and the prices of the ethanol fuels.     

The benefits of the transition from fossil fuel to solar energy in Libya: A street lighting system case study

The Libyan economy is dominated by the oil and the gas industry which are considered as the primary energy sources for the generating power plants. With the increased energy demands in the near future, Libya will be forced to burn more oil and gas. This, in turn will result in reducing the country revenue, threatening the economy and increasing the CO₂ emission. This triggers the alarm for Libya to an urgent plan to diversify the energy sources through using sustainable energy. The sun showers Libya every day by a huge amount of sunshine, especially during the peaks in the summer days. Recently, the country has been struggling to satisfy its escalating energy demands. The residential and street lighting loads constitute more than 50% of the electricity demands in Libya. Street lighting consumes more than 3.996 TW h, which is around one fifth of the energy demands in Libya. Energy conservation and transition from fossil fuel to renewable energy could have significant profit on the energy sector in Libya. For example, Libya is still relying on the old-fashioned, inefficient and unsustainable street lighting systems. Replacing the old technology lighting systems with up-to-date solar powered lighting system can achieve energy saving and sustainability. In this paper, improving the energy situation in Libya through replacing the high pressure sodium street lighting systems with solar powered LED street lighting systems is investigated. A four km road is chosen as a case study. Four alternatives are analyzed; grid-powered high pressure sodium lamp street lighting system, grid-powered LED lamp street lighting system, stand-alone solar powered LED street lighting system and grid-connected solar powered LED street lighting system. The four options are compared in terms of the capital cost, maintenance cost, total cost, fuel cost and the CO₂ emission. Replacing the high pressure sodium lamp system with LED lamp system saves 75% of energy and reduces the CO₂ emission by 75%. The stand-alone solar powered LED lighting system cuts the CO₂ emission, saves the fuel and is economically feasible. Furthermore, improvement is attained if the solar powered lighting system is connected to the grid where the excess energy is fed to the grid. The two solar powered options are economically feasible and sustainable.     

Kinetics of hydrolysis of sodium borohydride for hydrogen production in fuel cell applications: A review

Hydrogen generation from the hydrolysis of sodium borohydride (NaBH₄) solution has drawn much attention since early 2000s, due to its high theoretical hydrogen storage capacity (10.8 wt%) and potentially safe operation. However, hydrolysis of NaBH₄ for hydrogen generation is a complex process, which is influenced by factors such as catalyst performance, NaBH₄ concentration, stabilizer concentration, reaction temperature, complex kinetics and excess water requirement. All of these limit the hydrogen storage capacities of NaBH₄, whose practical application, however, has not yet reached a scientific and technical maturity. Despite extensive efforts, the kinetics of NaBH₄ hydrolysis reaction is not fully understood. Therefore, better understanding of the kinetics of hydrolysis reaction and development of a reliable kinetic model is a field of great importance in the study of NaBH₄ based hydrogen generation system. This review summarizes in detail the extensive literature on kinetics of hydrolysis of aqueous NaBH₄ solution.     

Deployment of fuel cell vehicles in China: Greenhouse gas emission reductions from converting the heavy-duty truck fleet from diesel and natural gas to hydrogen

Hydrogen fuel cells, as an energy source for heavy duty vehicles, are gaining attention as a potential carbon mitigation strategy. Here we calculate the greenhouse gas (GHG) emissions of the Chinese heavy-duty truck fleet under four hydrogen fuel cell heavy-duty truck penetration scenarios from 2020 through 2050. We introduce Aggressive, Moderate, Conservative and No Fuel Cell Vehicle (No FCV) scenarios. Under these four scenarios, the market share of heavy-duty trucks powered by fuel cells will reach 100%, 50%, 20% and 0%, respectively, in 2050. We go beyond previous studies which compared differences in GHG emissions from different hydrogen production pathways. We now combine an analysis of the carbon intensity of various hydrogen production pathways with predictions of the future hydrogen supply structure in China along with various penetration rates of heavy-duty fuel cell vehicles. We calculate the associated carbon intensity per vehicle kilometer travelled of the hydrogen used in heavy-duty trucks in each scenario, providing a practical application of our research. Our results indicate that if China relies only on fuel economy improvements, with the projected increase in vehicle miles travelled, the GHG emissions of the heavy-duty truck fleet will continue to increase and will remain almost unchanged after 2025. The Aggressive, Moderate and Conservative FCV Scenarios will achieve 63%, 30% and 12% reductions, respectively, in GHG emissions in 2050 from the heavy duty truck fleet compared to the No FCV Scenario. Additional reductions are possible if the current source of hydrogen from fossil fuels was displaced with increased use of hydrogen from water electrolysis using non-fossil generated electricity.     

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.     

Willingness to pay for green electricity in Korea: A contingent valuation study

Green electricity is energy that is generated from renewable energy sources such as solar power, wind power, small-scale hydroelectric power, tidal power, and biomass power. These sources mostly do not produce pollutants and are considered environmentally friendly. However, considering the current state of technology, they are more costly. Government should take visible actions to compensate for the increased production costs. This paper attempts to apply a contingent valuation (CV) method to obtain at least a preliminary evaluation of the benefits that ensue from the introduction of the policy that raises the percentage of green electricity consumption from 0.2% of the total electricity supply to 7% by 2011. Overall, the CV survey was successful in eliciting the willingness to pay (WTP) for green electricity considering that the CV method operated within respondents’ abilities to answer and the WTP estimates were statistically significant. The monthly mean WTP estimates from parametric and non-parametric methods were KRW 1681 (USD 1.8) and KRW 2072 (USD 2.2), respectively. The estimates of the annual benefits to relevant residents amounted to KRW 150.5 billion (USD 157.5 million) and KRW 185.6 billion (USD 194.2 million), respectively.     

A combined physicochemical and electrocatalytic study of microwave synthesized tungsten mono-carbide nanoparticles on multiwalled carbon nanotubes as a co-catalyst for a proton-exchange membrane fuel cell

Tungsten mono-carbide (WC) nanoparticles supported on multiwalled carbon nanotube (MWCNT) was synthesized by a microwave-assisted solid-state carburization. The prepared samples were used as a co-catalyst to prepare Pt-WC/MWCNT catalyst for a proton-exchange membrane fuel cell. MWCNTs with and without oxidative pretreatments were characterized as the starting precursors. The influence of the carbide formation conditions on the physicochemical characteristics of the final product were extensively investigated. According to the results, surface pretreatment of the MWCNTs can improve the yield of carbide formation. Furthermore, carburization process can improve the catalyst utilization due to increasing the number of surface defects of the MWCNT supporting materials which can be interpreted as structural effect of the carburization process. It is believed that the superior performance of electrodes modified with tungsten carbide is mostly due to the structural effect of the carburization process and synergistic effect between the electrocatalytic activity of WC and Pt.     

An ex-ante evaluation of a White Certificates scheme in The Netherlands: A case study for the household sector

Increased efficiency of energy demand is generally recognized as a very cost-effective strategy to reduce energy requirements and the related environmental impacts (e.g. the greenhouse effect). In order to improve energy efficiency the use of innovative market mechanisms, such as the White Certificates (WhC), has been proposed. The basic idea underlying this policy instrument is that specific energy saving targets are set for energy suppliers or energy distributors. These requirements must be fulfilled in a predefined time frame. The focus of this paper is on the effect on energy efficiency improvement, on the behavior of the end consumers and the market of energy efficiency measures. Furthermore, we study the possible effects of WhC in The Netherlands by means of a theoretical analysis and an empirical bottom-up model. We compare concrete energy efficient technologies in terms of cost-effectiveness and energy efficiency improvement. In combination with existing Dutch policies for energy efficiency improvement in the built environment, the contribution of this innovative scheme could enhance the accomplishment of energy efficiency targets. In this paper, two packages of energy saving measures of a WhC scheme are studied for Dutch households. The costs of these technologies are estimated through the use of different discount rates, which imply overcoming of the market barriers through the use of the WhC. A scheme that includes all available technologies as flexible options appears as a realistic solution and can generate cost effectively up to 180 PJ primary energy savings and 4550 M€ cumulative net savings in the year 2020, at a discount rate of 5%, under the precondition that the policy and administrative costs can be kept low.