Yoshikuni Yoshida

Comprehensive comparison of efficiency and CO2 emissions between biomass energy conversion technologies - position of supercritical water gasification in biomass technologies.

Abstract Efficiency and CO 2 emissions between various methods of biomass energy conversion are compared from the viewpoint of life-cycle evaluation. As for electricity generation, efficient processes are thermal gasification combined cycle, supercritical water gasification combined cycle, and direct combustion in order of efficiency for low moisture content biomass. Supercritical water gasification combined cycle is the most efficient for high moisture content biomass. Battery electric vehicle, gasoline hybrid electric vehicle, and gas full cell vehicle (FCV) show high efficiency in automobiles. Biomass FCV shows high efficiency in the vehicles utilizing biomass. Biogas combustion is the most efficient for heat utilization. Then, the position of supercritical water gasification in various technologies of energy conversion is examined by modeling an overall energy system. The tradeoff between CO 2 emissions and total cost of technologies is analyzed so that the most cost-effective technology can be determined for different CO 2 emissions constraints. Computed results show that biomass is mainly consumed for electricity and heat generation so as to utilize finite biomass resources efficiently. Transportation fuels are generally made from fossil fuels. Cost-effective processes for CO 2 reduction are thermal gasification and reforming when the present efficiency and prices are assumed. Supercritical water gasification is also one of the optimal processes when the relative cost to fuel cell decreases. Improving heat exchange efficiency also contributes toward enhancing the position of supercritical water gasification in biomass technologies.

An Integrated Computational Infrastructure for a Virtual Tokyo Concepts and Examples

Summary The evaluation of tradeoffs between technologies and policies for mitigation of environmental problems requires a systematic investigation of effects over the entire region under consideration. When attempting to model such large complex systems, issues such as usability, maintenance, and computing efficiency often become major modeling barriers. In this work a software prototype for integrating the services of computational models over the Internet, called DOME (distributed object-based modeling environment) is used to facilitate the construction of virtual Tokyo—a simulation platform for evaluating holistically the tradeoffs between various technologies for reducing the emissions of greenhouse gases. In making steps toward this ultimate goal, two models have been developed that use data defining spatial land-use distributions and the flows of goods expressed as an input-output table to provide information on the spatial and temporal characteristics of an urban region. Integrated, these models form a preliminary virtual Tokyo model when applied to Tokyo-specific databases. Given this platform, process models are applied to examine the effectiveness of using photovoltaic (PV) modules on the demand side to reduce conventional electric power generation and, thereby, also reduce carbon dioxide emissions. The results of introducing PV modules on the rooftops of buildings in Tokyo under various installation conditions are presented as a working example of the prototype. For full deployment on usable rooftop space, PV power generation could reduce carbon dioxide emissions from electric power generation by more than 12%. Future work will use the same methods as presented in this paper to examine cost, a critical determinant in the actual feasibility of PV module installation.

Life cycle of CO2-emissions from electric vehicles and gasoline vehicles utilizing a process-relational model

This article aims at estimating life cycle CO2 emissions from electric vehicles (EV) and gasoline vehicles (GV), although the estimation in this study is not an LCA according to ISO14040s. For this purpose, a mathematical tool called the Process-relational model was developed. The Process-relational model is used for establishing life cycle inventories. The model has a structure which improved the principle of input-output analysis in econometrics that only one product is generated by one process. This model enabled us to overcome difficulties of LCA in retracing complicated repercussions among production systems.Then, life cycle CO2, emissions from electric vehicles (EV) and gasoline vehicles (GV) were estimated with this model. Estimated results indicated that the manufacture and driving of EV resulted in less CO2 emissions than chose of GV. However, the difference between EV and GV dramatically changed depending on traffic situations. Namely, the difference became larger as the average velocity of the vehicles became lower. We also compared CO2, emission from manufacturing EV with that from driving EV. The share of manufacture was shown to increase in total CO2, emissions as the average velocity of the EV became higher. In conclusion, we clarified the direction of research and development of EV and GV for reducing the life cycle CO2.

Environmental evaluation of introducing electric vehicles using a dynamic traffic-flow model

A dynamic traffic-flow model (DTFM) is used in this study to evaluate the effectiveness of introducing electric vehicles (EVs) into the total traffic system as one of the alternative fuel vehicles. This model simulates congested and non-congested traffic flow caused by changes in the traffic demand. An environmental evaluation is carried out on the basis that all vehicles are substituted for EVs. Calculated results indicate that by introducing EVs, the NOx emissions and the CO2 emissions can be reduced by approximately 25.7 and 14.4% respectively. If battery performance of EVs is improved further, emissions can be further reduced by 39.6% (NOx) and 27.8% (CO2). Since emissions from heavy-duty vehicles are greater than other vehicles, the following measures have to be taken for these vehicles to significantly improve their impact upon the overall environment: (1) improvement in fuel efficiency and reductions of NOx in exhaust gas, (2) traffic demand management, such as modal shift.

Reliability of LCI considering the uncertainties of energy consumptions in input-output analyses

The dispersion of input-coefficients in input-output (I-O) tables and the effect on LCA results are evaluated, utilizing the data for compiling the I-O tables. CO2 emission intensity and its variance with each commodity and service categorized in the I-O tables are estimated and applied to the LCA of a specific passenger car. Calculated results show that coefficients of variation (CV) of CO2-emission intensity are about 0.8 for the intermediate commodities which are frequently assessed in LCA. CO2 emissions induced by the production of the passenger car and the CV of the emissions are estimated at 1.3 Mg-C and 0.14, respectively. The value of CV is smaller than that of the most intermediate commodities since the CV of total emissions decreases as the number of components of the passenger car increases. Although emission intensity itself given by I-O tables has large variance, I-O tables are still useful tools for LCA if the number of components of a product is large enough.

Prospective on Policies and Measures for Realizing a Secure, Economical and Low-Carbon Energy System——Taking the Effects of the Great East Japan Earthquake into Consideration

The Great East Japan Earthquake devastated the eastern regions of Japan on this March. Due to the nuclear accident caused by the earthquake, Japan’s Cabinet stated to revise energy policies. This article aims at investigating whether we could establish a secure, economical and low-carbon energy system taking account of the serious situation after the Earthquake. For this purpose, we first evaluated possible technology options along with economic options. Then we integrated these options in a computable general equilibrium model for Japan so as to evaluate the impacts to national economy. As results, we quantified the relationships between energy security, quality of life and CO2 emissions.

Process System Modelling of Production Technology Alternatives using Input- Output Tables with Sector Specific Units

Input–output analysis is usually based on tables of accounts expressed in uniform monetary or physical units. However, from a process system modelling perspective, tables of accounts in sector specific units may be more useful for evaluating the effectiveness of new production technologies on reducing pollutant emissions. Using the sector specific unit conceptualization of an IO table, one can consider the effect of changes in direct input coefficients for a particular sector on the complete set of total input coefficients independently from the other direct input coefficients. A process system modelling based method for calculating the total industrial outputs from a new technology matrix together with the new relative prices for each sector output is presented. The method is then used to study the effect of technology changes in the steel making industry in Liaoning Province, China on prices and pollutant emissions.

Recovery of fluorocarbons in Japan as a measure for abating global warming

The objective of this study is to evaluate the potential for recovering fluorocarbons as measures for the abatement of global warming. In this study, we focused on the three different kinds of fluorocarbons: CFCs, HCFCs and HFCs, and targeted refrigerant use because of the availability of relevant data. We first estimated future fluorocarbon emissions from the targeted appliances; we next compared those emissions in the units of CO2 equivalent to the level of CO2 emissions in 1990 from a quantitative point of view. As the result of this study, it was found that fluorocarbon emissions in 1999 and 2010 would be equal to approximately 7 and 3% of the level of CO2 emissions in 1990 respectively. Moreover, if we implement a 100% recovery rate in every recovery route, we can reduce a large amount of emissions which correspond to approximately 2-5% of the level of CO2 emissions in 1990, even if we take into account the energy-related CO2 emissions by the transportation and decomposition of fluorocarbons.

The decision to invest in emissions reduction technologies based on the real options approach

Publisher Summary This chapter focuses on a study that illustrates the way uncertainty and social costs can influence a firms decision to invest in an emission reduction technology. For a case study, this study considers a firm owing aged coal-fired thermal power plants in the United States. The firm has an option to invest in an Integrated coal Gasification Combined Cycle (IGCC) no capture plant, IGCC capture plant, or Natural Gas Combined Cycle (NGCC) for the substitution of the aged power plants. The optimal investment behavior subject to stochastic CO 2 emission allowance price, natural gas price, and social cost is calculated numerically in the study by using the Bellman equation and lattice models with few variables. The results show that not only CO 2 emission allowance price and natural gas price but also social costs and their uncertainty influence the firms decision to invest in capture plant, especially at an early date. It is suggested that direct subsidies from government to the firms capital cost are worthwhile, but social preference that forms the characteristic of the social costs could be a key issue in a firms decision for the investment in an emission reduction technology.

Economic and Environmental Effects of Installing Distributed Energy Resources into a Household

Improving energy efficiency in the residential sector is a pressing issue in Japan. This study examines the economic and environmental impacts of introducing the following distributed energy resources: photovoltaics (PV), a fuel cell, and a battery. We estimate electricity and hot water demand profiles of a household by using simulated living activities. Electric power from a residential PV system is also calculated from the observed solar radiation. By using mixed integer programming, we perform a cost minimization operating simulation of a residential PV, fuel cell, and battery. The result suggests that we can create a net-zero energy house by installing both a PV system and a fuel cell into one house. On the other hand, using a battery with a fuel cell increases the household energy cost, and has few effects on CO2 emission reduction.