Green Energy and Technology

Using a global energy model describing the bioenergy sector in detail, this chapter examines the cost-optimal use of modern bioenergy over the period 2010-2100 under a 400 ppmv CO₂ stabilization constraint and its potential contribution to satisfying this stringent constraint. The following three main results are obtained. First, it is cost-optimal to use modern bioenergy largely to generate heat and replace direct coal use until around 2040. As second-generation bioenergy conversion technologies and CO₂ capture and storage (CCS) technologies become mature in the second half of the century, it becomes cost-optimal to produce biofuels and electricity using these technologies. All biomass gasification-based conversion technologies are combined with CCS (called BECCS) from 2060. Second, introducing modern bioenergy, particularly the strategy of negative CO₂ emissions provided by BECCS, makes a substantial contribution to stabilizing the atmospheric CO₂ concentration at 400 ppmv in 2100 and is a robust future technology option under such a stringent climate stabilization constraint. However, from around 2060, bioenergy supply potentials place a severe limit on the amount of modern bioenergy produced. Third, under the 400 ppmv CO₂ stabilization constraint, BECCS holds a large share of the global amount of CCS throughout the time horizon and offers great flexibility in the timing of CO₂ reductions, whose value is estimated to be as high as $13.3 trillion in constant 2000 US dollars. A significant portion of the CO₂ capture is implemented in now-developing regions, implying the importance of the effective transfer of CCS technologies to nowdeveloping regions for achieving stringent climate stabilization targets.

Due to high energy efficiency and zero emissions, some believe fuel cell vehicles (FCVs) could revolutionize the automobile industry by replacing internal combustion engine technology, and could be boosted and boomed in China first. However, hydrogen infrastructure is one of the major barriers. Because different H2 pathways have very different energy and emissions effects, the well-to-wheels analyses are necessary for adequately evaluating fuel/vehicle systems. The pathways used to supply H2 for FCVs must be carefully examined by their WTW energy use, GHGs emissions, total criteria pollutions emissions, and urban criteria pollutions emissions.

Ten hydrogen pathways in Shanghai have been simulated. The results include well-towheels energy use, GHGs emissions, total criteria pollutions and urban criteria pollutions.

A fuel-cycle model developed at Argonne National Laboratory – called the Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET) model – was used to evaluate well-to-wheels energy and emissions impacts of hydrogen pathways in this study. Because GREET model has no coal and naphtha-based hydrogen pathways, four hydrogen pathways (No. 5-8) computer program were added to GREET in the research. To analyze uncertain impacts, commercial software, Crystal BallTM, is used to conduct Monte Carlo simulations. Instead of the point estimates, the results of this study were probability distributions.

Through the research, the following conclusions can be achieved:

(1) All the pathways have significant reduction in WTW petroleum use, except two H2 pathways from naphtha, which achieve about 20% reduction in WTW petroleum.

(2) All the pathways have significant reduction in WTW urban criteria pollutions emissions, except two H2 pathways from coal, which offer significant increase in WTW urban SOx emissions.

(3) The NG-based H2 pathways have best WTW energy efficiencies, and the electrolysis H2 pathways have worst WTW energy efficiencies. The WTW energy efficiencies of H2 pathways from naphtha and coal are between NG-based pathways and electrolysis pathways. The pathways from naphtha have higher energy efficiencies than the pathways from coal. Only four pathways (G NG C, G NG R, G N C, and L NG C) offer WTW energy benefits, and the other six pathways consume more WTW energy than baseline-conventional gasoline vehicles.

(4) Changes in WTW GHGs emissions have nearly identical results with changes in WTW energy use.

(5) For WTW total criteria pollutions emissions, all pathways can achieve significant reduction in WTW total VOCs and CO. the other criteria pollutions emissions-NOx, PM10, and SOx, have certainly reduction in NG and crude oil-based H2 pathways, but have significant increase in electrolysis and coal-based pathways.

Oil shale has constituted for a long time an economical hope for countries that possess important reserves of these rocks and that view to use them as an energy source substitute for petroleum. Morocco, with estimated reserves of 93 billion tons, is increasingly looking at oil shale as an alternative energy source. A lot of studies have concentrated on oil shale located in Timahdit and Tarfaya, because of their high percentage of organic matter. Most of the studies focus either on the effect of various parameters on the yield and the quality of the oil obtained by conventional pyrolysis, or on the characterization of these oils by different physical and chemical techniques.

This paper explores the possibility to produce new materials, starting from the Moroccan oil shale, for different applications. More specifically, we aimed to demonstrate that the organic fraction of the oil shale could be used as precursors of low cost carbon fibres or graphitizable carbon, after appropriate chemical treatments resulting in a “maturation” of this organic phase. We also showed that this organic fraction of the Moroccan oil shale has interesting bioactive properties and that it could be used as a source of compounds with pharmaceutical interests.

The aim of this paper is to discuss potentials of biofuels to contribute to environmentally sustainable energy supplies based on the Sustainable Process Index (SPI), an alternative calculation method for ecological footprints. The paper focuses on energy demand for transport. Comparing biofuels with fossil fuels it can be seen that “conventional” first generation biofuels reduce the overall ecological pressure about 30% compared to fossil fuel. If second generation biofuels are used footprint reductions of factors 13 to 16 compared to fossil fuel can be achieved depending on the production methods and the scale of the plant. On the other hand, production limits occur due to overall environmental capacity limits and resource constraints. If we look into technological options for transport, the long term development seems to be electricity based. Yet, we still lack sufficient sustainable electricity production besides wind and biomass. Therefore, we suggest that biofuels may be an advantageous option in a transition period from fossil based to electricity based transport systems, where minor effort is needed to retrofit vehicles until new electricity based technologies for transport means and the corresponding electricity production are available.

Generation of electrical energy from the wind can be a suitable proposition for off grid power supply at locations having a favorable wind regime. Proper design of wind power generation system is of utmost importance to assure maximum benefit to the consumer in terms of economic competitiveness as well as power supply reliability. Designing a wind power system involves appropriate sizing of different components based on the availability of wind speeds and the energy demand. Since, wind as a resource is intermittent and variable by nature, the mismatch between the generation and demand can be leveled by provision of a battery bank as a storage medium. A methodology for designing an efficient wind-battery power system is presented in this chapter. The major system design parameters are identified to be the wind rotor diameter, the generator rating and the storage capacity. By considering the energy interactions between the generator, the storage system and the load over a given time horizon, a number of feasible design solutions can be generated. A diagrammatic representation of all feasible solutions enables a system designer to understand the tradeoffs between different system design variables, corresponding maximum and minimum limits, and arrive at an optimum solution system subject to an appropriate design objective as well.

This chapter analyses the possibility of implementation of Sustainable Electric Power System (SEPS) as a totally green strategy of electric energy production for the world by the year 2040. The analysis presented in the paper is based on the EREC strategy which foresees the share of 82% of Renewable Energy Sources (RES). The problem of implementation of this strategy is that the more significant RES (Sun and wind) are characterized by intermittence of input energy, for which reason they cannot provide continuous and reliable supply of energy to consumers without electric storage. The solution to this problem and to creating conditions for achieving SEPS is an innovative concept of Solar Hydro Electric (SHE) power plant which is a basically combined photovoltaic power plant and pump storage which can produce and store relatively large quantities of energy and provide continuous supply of electric power and energy to consumers. In this way SHE is put into equal position with power plants using conventional power fuels, and because of that, SHE is presented in this paper as the main building element of the future SEPS. The conducted analysis and results clearly point not only to the reality, but the necessity for SEPS and to the exceptionally big achievements which the PV generator use will reach in the future. The proposed strategy of SEPS development could significantly contribute to realization of sustainability objectives, particularly to reduction of the problem of global warming.

Homogeneous charge compression ignition (HCCI) combustion is a distinct combustion concept, which can be implemented in internal combustion engines. Its development began thirty years ago and is still the focus of many researchers worldwide. The main features which attract attention to HCCI engines are of both environmental and energysaving character. Due to the premixed nature of HCCI combustion and the relatively lean mixtures used, NOx and soot emissions are but a fraction of the ones emitted by conventional spark ignition (SI) or compression ignition (CI) engines. Moreover, the relatively rapid combustion process and the unthrottled operation provide the potential for high thermal efficiency. Apart from these favorable attributes of HCCI combustion, significant issues have to be resolved. These issues are related to the high unburned hydrocarbons and carbon monoxide emissions, which are emitted during HCCI operation. Moreover, technical issues have arisen regarding the implementation of the HCCI combustion concept to actual engines. The latter is related to difficulties in controlling the ignition timing and the combustion rate over a wide load-engine speed range. The ignition timing must be adequately controlled if the thermal efficiency is to be kept high; the combustion rate control is of importance, since the high combustion rates encountered in HCCI combustion increase the peak combustion pressures and the pressure rise rates, thereby limiting the maximum attainable load. The present chapter presents the main features of HCCI combustion, namely its characterization based on experimental data, the pollutant emissions formation processes, the effect of major operating parameters on HCCI combustion and the various strategies used for the realization of the HCCI combustion concept to gasoline or diesel HCCI engines.

Homogeneous charge compression ignition (HCCI) is an autoignition combustion process with a lean or dilute fuel/air mixture. It can provide both good fuel economy and very low emissions of nitrogen oxides (NOx) and particulates. Therefore, it is considered to be one of the most promising internal combustion engine concepts for the future. However, there are some obstacles that must be overcome before the potential benefits of HCCI combustion can be fully realized in commercialization, including combustion phasing control, operation range extending (high levels of noise, UHC and CO emissions), cold start, and homogeneous mixture preparation. All these HCCI characteristics have been summarized in Section 1. To overcome these obstacles, many effective technologies have been carried out and these technologies will be reviewed in Section 2 according to different fuel properties. HCCI can be applied to a variety of fuel types and the choice of fuel will have a significant impact on both engine design and control strategies. Some chemical components have the ability to inhibit or promote the heat release process associated with autoignition. Typical generalized diesel-fuelled HCCI combustion modes include: early direct injection HCCI, late direct injection HCCI, premixed/direct-injected HCCI combustion and low temperature combustion. Mixture control (mixture preparation), including charge components and temperature control in the whole combustion history and high pre-ignition mixing rate, is the key issue to achieve diesel HCCI combustion. The high octane numbers of gasoline fuels mean that such fuels need high ignition temperatures, which highlights the difficulty of autoignition. The main challenge for gasoline HCCI operation is focus on the obtaining sufficient thermal energy to trigger autoignition of mixtures late in the compression stroke, extending the operational range, and the transient control. In addition, alternative fuel can save the fossil fuel and reduce the CO2 emission, therefore it has been got more attention in recent years. And to understand fundamental theory of HCCI combustion process, the primary reference fuel is the best choice due to the better understood chemical kinetics. All these fuels will be also introduced in the Section 2. Advanced control strategies of fuel/air mixture are more important than simple “homogeneous charge’’ for the HCCI combustion control. Further, it is impossible to get an absolutely homogeneous mixture in the operation of practical HCCI engines. Modest inhomogeneity in fuel concentration or temperature appearing in mixing can affect the autoignition and combustion process. And stratification strategy also has the potential to extend the HCCI operation range to higher loads. The thermal stratification can be caused by wall heat transfer and turbulent mixing during the compression stroke for a low-residual engine. This thermal stratification causes the combustion to occur as a sequential autoignition of progressively cooler regions, slowing the rate of pressure rise. For engines with high levels of retained residuals, incomplete mixing between the fresh charge and hot residuals could also contribute to the thermal stratification. Apart from the thermal stratification, more researches are about the charge or compositional stratification. The charge stratification is focus on the different injection strategies, while the compositional stratification means that all the EGR, internal or external, changes the composition of the charge therefore forming the different compositional stratification. These stratification combustion characteristics have been reviewed in Section 3. Finally, a summary for the progress of HCCI combustion and future research direction has been shown in Section 4.

Hydrogen has long been recognized as an energy carrier for the transportation sector with a number of important advantages compared to the currently used fossil fuels. It can be produced from a variety of (renewable) energy sources and it can produce energy in an efficient and clean way. For powering vehicles, hydrogen can be used in two ways, either in a fuel cell (FC) producing electricity, or in an internal combustion engine (ICE) producing mechanical power. Converting an ICE to hydrogen operation is relatively straightforward and is interesting as it offers a bi-fuel possibility. What is less known is that a hydrogen-fueled ICE (H2ICE) has a high efficiency potential, leading to a smaller gap in efficiency compared to a hydrogen-fueled FC than commonly assumed. This chapter describes the physical and chemical properties of hydrogen that theoretically allow a high engine efficiency, and presents experimental confirmation of these theoretical considerations. Published efficiency figures obtained by engine testing are reviewed and recent work on both port fuel injection (PFI) as direct injection (DI) H₂ICEs is discussed. Finally, an outlook is given on the potential for further increases in efficiency.

Currently, major automotive companies are involved intensively in the development of hydrogen-fuelled FCV’s in order to be globally commercialized by 2005. However, the current cost of FCV’s and lack of commercials and information addressing environmental, economical and technological advantages associated with such vehicles leave the general public to be completely unaware. This paper presents a general assessment of commercialization and public acceptance of utilizing FCV’s in terms of their costs in comparison to ICV’s, and safety and dependability at various scenarios over the next twenty years. A significant improvement in the cost fraction of FCV’s was achieved in the 1990’s in comparison with the cost fraction of ICV’s in the same period. Moreover, the calculated results demonstrated a lower cost of FCV’s and a higher safety and dependability could lead to a higher rate of commercialization and public acceptance.

In the automobile industry, engines are mostly 4-stroke engines (intake stroke, compression stroke, combustion stroke and exhaust stroke) and generally there are two kinds of automobile engines: the Otto engine (Spark Ignition, SI) and the Diesel engine (Compression Ignition, CI). These two types of engines will be discussed as well as the most important pollutants they emit. In order to reduce the emission of these pollutants an alternative combustion process is discussed, called the Homogeneous Charge Combustion Ignition (HCCI). The advantages and problems are treated. One of the major problems to be solved is the ignition timing that is spontaneous in contrast with that of the spark ignition and diesel engines. Results from experiments, performed in a mono-cylinder engine, are analysed in order to discuss criteria that should be taken into account before the solution of controlling the auto-ignition can be discussed. The results are subsequently used in order to propose an outline for controlling the autoignition in an HCCI engine.