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The objective of this paper is to analyze the most up-to-date data available on total greenhouse-gas emissions of a LNG fuel supply chain and life-cycle of city gas 13A 1 based on surveys of the LNG projects delivering to Japan, which should provide useful basic-data for conducting life-cycle analyses of other product systems as well as future alternative energy systems, because of highly reliable data qualified in terms of its source and representativeness. In addition, the life-cycle greenhouse-gas emissions of LNG and city-gas 13A in 2010 were also predicted, taking into account not only the improvement of technologies, but also the change of composition of LNG projects. As a result of this analysis, the total amount of greenhouse-gas emissions of the whole city-gas 13A chain at present was calculated to be 61.91 g-CO2/MJ, and the life-cycle greenhouse-gas emissions of LNG and city-gas 13A in 2010 could be expected to decrease by about 1.1% of the current emissions.

We evaluated total energy consumption and CO2 emissions in the phases of a city gas utilization system from obtaining raw materials to consuming the product. Assuming monthly and hourly demand figures for electricity, heat for space heating, and hot water in a typical hospital, we explore the optimal size and operation of a city gas system that minimizes the life cycle CO2 emissions or total cost. The cost-effectiveness of conventional cogeneration, a solar heating system, and hybrid cogeneration utilizing solar heat is compared. We formulate a problem of mixed integer programming that includes integral parameters that express the state of system devices such as the on/off condition of switches. As a result of optimization, the hybrid cogeneration can reduce annual CO2 emissions by 43% compared with the system without cogeneration. The sensitivity of CO2 reduction and cost to the scale of the CGS is also analyzed. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(1): 22–32, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10369

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.

We evaluate total energy consumption and CO2 emissions in the phase of the city gas utilization system from obtaining raw materials to consuming the product. First, we develop a simulation model which calculates CO2 emissions for monthly and hourly demands of electricity, heats for air conditioning and hot-water in a typical hospital. Under the given standard capacity and operating time of CGS, energy consumption in the equipments is calculated in detail considering the partial load efficiency and the control by the temperature of exhaust heat. Then, we explored the optimal size and operation of city gas system that minimizes the life cycle CO2 emissions or total cost. The cost-effectiveness is compared between conventional co-generation, solar heat system, and hybrid co-generation utilizing solar heat. We formulate a problem of mixed integer programming that includes integral parameters that express the state of system devices such as on/off of switches. As a result of optimization, the hybrid co-generation can reduce annual CO2 emissions by forty-three percent compared with the system without co-generation. Sensitivity for the scale of CGS on CO2 reduction and cost is also analyzed.

In this paper, we proposed a procedure for calculation of room temperature in multi-room building using the backward-difference method. Based on this procedure and using our simulation program, we evaluated CO2 reduction by installating high light-reflective and high heat-emissive paint in buildings. Heat balance equations on each heat point in each room or wall in the building were deduced from one-dimensional heat-conduction equation and converted to the matrix equation. We improved matrix computing and developed a different procedure from conventional methods. Because this procedure is simple, we consider that this is applicable to estimation of most building’s technologies. As its application, the effects of high light-reflective and high heat-emissive paint was evaluated. Although the paint increases heating load, it can reduce cooling load. We thus conclude that the paint is effective for CO2 reduction.

Partial oxidation was applied to enhance the gasification efficiency of the supercritical water gasification of biomass. Hydrogen peroxide was employed as oxygen source and effect of partial oxidation on supercritical water gasification of 0.6M glucose, a model compound of biomass, and cabbage slurry was experimentally investigated using a bench-scale continuous reactor. For gasification at 873K, gasification efficiency close to unity was obtained, but at a lower temperature, the value decreased. The effect of partial oxidation was thus investigated at lower temperatures. Partial oxidation was effective in improving gasification efficiency for both glucose solution and cabbage slurry. The improvement of gasification efficiency was accompanied with higher yield of both hydrogen and carbon monoxide. The effect is clear at higher temperature. Proper amount of oxidant addition needs to be decided.

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.

Clean development mechanism (CDM) is expected to facilitate technology transfer from developed to developing countries and to reduce greenhouse gas emissions economically. This article evaluates a CDM project utilizing photovoltaic (PV) systems. For this purpose, we first estimated life cycle CO2 emissions of PV and other power generation systems based on an input-output table for environmental analysis. The cost of the PV systems was also evaluated, taking into consideration the effect of mass production. Next, two dynamic scenarios were developed to disseminate PV systems. One is a scenario only for domestic dissemination, and the other includes a CDM project utilizing PV systems as well as domestic dissemination. We then evaluated a net present value of the CDM as well as CO2 reductions in the dynamic scenarios. A net present value of the CDM project was estimated to be negative at 5% of the discount rate. At the same time, it was shown to be much higher at a lower discount rate and at higher prices of certified emission reduction by the CDM. Accordingly, we proposed new schemes to make the CDM viable. In particular, we discussed how to lower project risks with CDM.

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.

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.

An analysis was conducted on greenhouse gas emissions from the liquified natural gas (LNG) chain and life cycle of City Gas 13A [caloric value: 46 MJ/Nm3(11,000 kcal/Nm3)], which is produced from LNG. The analysis was based on highly reliable data which are qualified in terms of source and representativeness. Actually, the latest data for CO2 and CH4 emissions from the natural gas field and liquefaction plant were obtained from field studies. Moreover, the analysis includes CO2 emissions during the LNG transportation from exporting countries to Japan, city gas production and distribution stage in Japan and the manufacturing of facilities associated with the production of natural gas overseas to final domestic consumption. The reduction effect of CO2 using LNG cryogenic energy was also considered. The evaluation showed that the level of greenhouse gas emissions and energy consumptions in the modern natural gas production and liquefaction plants were lower than those previously reported due to improvements in the production process. The results of the analysis also provide basic data essential for conducting life cycle analyses in many fields using natural gas.

The clean development mechanism (CDM) is expected to facilitate technology transfer from developed to developing countries, as well as to economically reduce greenhouse gas emissions. This article aims at evaluating strategies in CDM, in which developing countries can improve industrial energy efficiency with financial support from developed countries. First, we investigated characteristics of the systems utilizing game theory. Analytical results revealed that technology transfer through the system might be considerably diminished, depending on the shapes of the marginal cost functions for reducing CO2. Next we estimated actual marginal cost curves of countries involved in CDM, in order to know the cost-effectiveness of CO2 reduction options. Input-output tables were utilized in this analysis, since these are established in developing countries as well as in developed countries. We have transformed one country’s input-output table to be adjusted against another country, taking the difference in goods prices into consideration. As far as data on the economy and industry are concerned, we used those from Japan and China, since China has been rapidly increasing its economic scale and greenhouse gas emissions. However, the implications from these analyses are useful also for other countries.

The transport of what would otherwise be waste-heat (at temperatures between 30°C and 300°C) through pipelines using as an energy carrier either methanol or hydrogen gas has been studied. By using numerical models, the relative costs of new kinds of waste-heat transportation systems are evaluated and compared with those using vapor or hot water, which have been the major energy-carriers in pipeline transmission systems until now. Also, environmental regulations and a carbon tax are investigated as incentives for introducing these systems.

After COP3 a lot of countries and even their local governments are struggling to reduce CO2 emissions. However, the way to define CO2 emissions is not consistently standardized. In this study we calculate CO2 emissions in two ways: appar-ent and responsible emissions. Apparent CO2 emissions are caused by the domestic industrial activities and they include CO2 embodied in exports. Responsible CO2 emis- sions are attributed to domestic final demand and they include CO2 embodied in imports. We classify domestic production into that of Tokyo and that of the other regions, and cal-culate regional CO2 emissions by the above two ways. From the viewpoint of LCA (Life-Cycle Assessment), we utilized the regional input-output table for the database. Apparent and Responsible CO2 emissions of Tokyo are 17 Mt-C and 32Mt-C, respectively. Because the amount of CO2 results in such different values, standardizing the way to define CO2 emissions is a critical problem for deciding the goal of CO2 reduction. Concerning the emissions in each sector, power generation and transport have the largest reduction potential in industrial sectors. Making the life of buildings longer is the most effective measures from the consumers' viewpoint.

Degradation of the global environment and depletion of resources are threatening sustainable development of mankind. In particular, climate change caused by increasing greenhouse gases is one of the most serious issues in analyzing energy systems. This paper aims at proposing frameworks to investigate sustainability and at evaluating technologies for sustainable energy systems. For this purpose, we first define the index of sustainable limits on resource depletion and emissions. Sustainability of mineral and energy resources is evaluated based on the index. Estimations indicate that energy resources and CO2 are unsustainable, and that we should introduce technologies to reduce energy consumption and CO2 emissions. Life cycle energy requirements are assessed for photovoltaic systems as representatives of the technologies. Through the life cycle assessment, we quantitatively evaluate measures to improve life cycle energy requirements and capital costs. At the same time, we clarify the direction of research and development required for technologies to realize sustainable energy systems. © 1999 Scripta Technica, Electr Eng Jpn, 130(2): 25–31, 2000

This paper deals with sustainable energy technologies under restrictions on resources and environmental impact. We have developed a database to estimate life-cycle efficiencies and greenhouse-gas emissions. Next, we define sustainability limitations on resource depletion and emissions. Based on these concepts, the present world energy system is judged to be unsustainable. Mitigation measures such as disposal of CO 2 and solar power generation are evaluated utilizing the concept. We show how sustainability influences the cost-effectiveness of measures taken.

This paper deals with sustainable energy technologies under restrictions on resources and environmental impact. We have developed a database to estimate life-cycle efficiencies and greenhouse-gas emissions. Next, we define sustainability limitations on resource depletion and emissions. Based on these concepts, the present world energy system is judged to be unsustainable. Mitigation measures such as disposal of CO 2 and solar power generation are evaluated utilizing the concept. We show how sustainability influences the cost-effectiveness of measures taken. At the same time CO 2 removal is shown to play a transitional but important role to realize sustainable energy scenario in ultra-long term.

This paper aims at clarifying key points for realizing sustainable energy supply under restrictions on resource and environment. For this purpose, we first developed a database to estimate life cycle efficiencies and greenhouse gas emissions for various energy systems. Then on the basis of this life cycle assessment, we quantitatively define the concept of ‘Sustainability Limitations’ on resource depletion and environmental emissions. From this concept, present world is judged to be unsustainable both from resource and environmental viewpoints. At the same time, we clarify how far present world is from Sustainability Limitations. Then we describe our mathematical model simulating global energy supply and demand in ultra-long term. In this model, the concept of Sustainability Limitations is utilized so as to impose economic incentives to make energy system shift to a sustainable one in long term. Sustainability limitations of resource depletion and CO2 emissions are taken into consideration. As energy resources, this model includes coal, oil, natural gas, other unconventional fossil fuels, uranium and renewable resources. As energy technologies, it includes major technologies of mining, transport, conversion and final utilization. Computed results have shown that present energy system, which is judged to be unsustainable, shifts to a sustainable system in the ultra-long term with appropriate incentives.

Depletion of the fossil fuels and climate change caused by the greenhouse effect is threatening the sustainable development of mankind. Since the CO 2 produced by burning fossil fuels is the dominant source of anthropogenic greenhouse gas emissions, CO 2 disposal is expected to be an effective option for mitigating climate change. However, if we took the option of CO 2 disposal and continued relying on fossil fuels, it could not be the sustainable use of energy resources. Therefore we need some theoretical framework for realizing the sustainable development. In this paper, we have developed a model to demonstrate the way of sustainable use of energy resources under constraints on CO 2 emissions. Computed results have shown that present energy system based on fossil fuels shifts to the system based on renewable resources in the ultra-long term with appropriate incentives. CO 2 disposal plays an important but a transitional role in this analysis.

In this paper we have investigated the modification of energy system for reducing CO 2 economically. Hydrogen production plants with CO 2 removal systems and cogeneration plants are key technologies to reduce CO 2 economically. Characteristics of a novel energy system, which includes energy plants as described above, has been investigated with a linear programming model. A reference system has also been represented which behaves similarly to the present energy system for comparison. Static analyses of the models has demonstrated that CO 2 emissions can be reduced more economically and efficiently in the novel energy system than in the reference system. Dynamic analyses has shown the processes of the transitions from the present energy system to the novel energy system.

The future demand for electricity is uncertain and difficult to forecast, but it is necessary to do so in order to construct power plants. In that sense, a large-scale power plant is disadvantageous because it takes a long time to construct. On the other hand, although it takes less time to construct, a small-scale power plant is more expensive. Therefore large- and small-scale power plants could complement the disadvantages of each other. This paper develops a stochastic dynamic programming model to investigate the possibility. The model determines the capacities of large- and small-scale power plants in the face of uncertain demand to minimize the expected value of the total cost. Computed results have shown that small-scale plants can play a significant role in this case even if they are more expensive than large-scale plants.

Publisher Summary CO2 reduction in the automobile sector is difficult because regulations are not easily applied to the consumers sector. Green taxation is considered to be an effective option as a measure for the automobile sector, which reduces taxes for fuel-efficient automobiles. The green taxation policy, which has already started in Japan, does not seem to be effective enough for CO2 reduction since the car models that benefit from the tax reduction are limited and the abatement is limited to only two years. A more effective method on green taxation is required for CO2 emission reduction in the automobile sector to achieve the goals of the Kyoto Protocol. This chapter evaluates the effect of the tightened green taxation plan in which taxes are imposed in proportion to the fuel efficiency. Green taxation is one of the most effective economic policies for CO2 suppression with a small burden for taxpayers. A car type preference model is developed, based on a detailed database on sales and characteristics of cars in the 1990s. The preference model adopts the framework of nested logit. The preference model analyzes the CO2 reduction effects of green taxation on car possession. The effect of the new tax was simulated and imposed in proportion to fuel efficiency, instead of the present tax with revenue-neutral taxation, assuming the minimum tax level is not less than 7200 Yen/year, the tax charge of the class under 660 cc. As a result of imposing such taxation, if the preference of consumers' shifts to more fuel-efficient cars, then CO2 emissions can be reduced. Estimated CO2 emissions reduction is by approximately 3% in the flow base.

Publisher Summary Transportation is the basis of economic and social activities, which are indispensable for our human life. On the other hand, a large amount of energy is consumed through transportation, such as motor cars. This results in an increase in environmental emissions such as CO 2 , which contributes towards global warming. It is necessary to establish transportation systems with low environmental burdens, properly according to the growth in traffic demands and the needs of users. There are many countermeasures to reduce CO 2 emissions in the transportation sector. Among them, modal shift has not taken effect widely, although its necessity has beenrecognized in the past. While encouraging modal shift, it is the characteristics and transportability of substitutes for conventional means of transport that count. Under these circumstances, taking encouragement of modal shift in the passenger transportation sector into account, the authors have focused upon electric trolley buses (ETBs) as one of the substitutes for motor cars. This chapter aims to make an environmental evaluation of the ETB system. Initially, CO 2 emissions from ETBs, when driven under urban traffic conditions, were estimated and subsequently estimated from the viewpoint of life cycle assessment (LCA) to compare with those from other public transportation systems. Finally, an environmental evaluation in urban motor traffic system was carried out on the condition that ETBs be introduced as substitutes for diesel route buses. Results conclude that ETBs is one of the promising public transportation systems for establishing a transportation system with low environmental burdens, by encouraging modal shift in the passenger transportation sector.

Publisher Summary This chapter evaluates the potential for reducing fluorocarbon emissions as a measure for the abatement of global warming by enforcing new laws: the Law for Recycling of Specified Kinds of Home Appliances and the Law for Recovering and Decomposing of Specific Fluorocarbons. The chapter focuses on the three different kinds of fluorocarbons: CFCs, HCFCs, and HFCs, and targets refrigerant use because of the availability of relevant data. The Kyoto Protocol regulated the emissions of six types of greenhouse gases (GHGs): CO2, CH4, N2O, hydrofluorocarbons (HFCs), sulphur hexafluoride (SF6), and perfluorocarbons (PFCs). Under the protocol, Japan committed a 6% reduction from the level of equivalent CO2 emissions in 1990. However, it is a difficult task for Japan to achieve this reduction target by reducing the energy-related CO2 emissions, as its energy efficiency has already reached the world's highest level. Therefore, by considering the large effects on global warming caused by fluorinated GHGs, measures for reducing emissions of non-CO2 GHGs can be regarded as one of the important strategies to comply with the Kyoto Protocol. The restrictions for emissions of chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) have been omitted in the Kyoto Protocol, because CFCs and HCFCs have already been regulated as ozone depleting substances (ODSs) under the Montreal Protocol.

Publisher Summary CO2 emissions from the commercial and residential sectors have greatly increased in Japan. Governmental regulations for energy saving are very effective for the industrial sector, but they are found to be rather ineffective for the commercial and residential sectors. Thus, low-cost measures for CO2 reduction are really required in these two sectors. This chapter focuses on the installation of outer skin surface technologies to buildings. These technologies, low-cost measures for CO2 reduction, are applicable to buildings that have high light-reflective and high heat-emissive paint and the low light-reflective and the low heat-emissive outer skin surface. The air-conditioning demand in the building is calculated according to the recently developed dynamic heat load simulation program, and assesses the extent of reduction in CO2 emissions brought by high light-reflective and high heat-emissive paint or low light-reflective and low heat-emissive outer skin surface.

In this paper, we have investigated the cost-effectiveness of alternative fuel vehicles as a measure for CO2 reduction. Computed results indicate that the installation of alternative fuel vehicles is much more expensive than fuel switching in industry or the power generation sector. However, some economic incentives will make the price go down to the level at which alternative fuel vehicles are competitive with conventional vehicles. At the same time, mass production makes their prices go down although it is rather expensive at present. Then, we developed the scenarios in which CO2 emissions could be stabilised at the level in 1990. In the higher demand case (1.2%/yr.), it is indispensable to introduce alternative fuel vehicles into the market. Our model selects electric vehicles and compressed natural gas vehicles as cost-effective options. In the scenario where carbon tax revenue is not offset by subsidy, we have to impose prohibitively high carbon tax to suppress CO2. However, CO2 emission can be suppressed by a reasonable carbon tax if the tax revenue is returned to the market to subsidise alternative fuel vehicles and their infrastructures.

Input–output (I–O) analysis is frequently applied to the energy–environmental area, because not only the direct but also the indirect environmental repercussions of different patterns of final demand can be explored. I–O analysis has a structural deficiency in evaluating the system, including the production of by–products, since joint production is not assumed to appear in the theory of I–O analysis. Although several methods were developed so as to overcome this drawback, this problem has not been fundamentally solved. In this study, a three–dimensional input–output table (3DIO) is suggested in order to deal with joint production. 3DIO is an extension of the I–O table. It shows the interrelations between all of the activities and consists of I–O tables which are made for each commodity. The structure is described in the simple equations corresponding to the conventional I–O equations. The amount of produced commodities is correctly counted in 3DIO although the amount of by–products is not accurately counted in conventional methods. As an application of 3DIO analysis, we developed an energy–economic model and evaluated CO2 emissions as well as economic growth, taking several measures for CO2 abatement into account. One of the main characteristics of the model is that the measures involving joint production can be evaluated in the framework of I–O analysis. Computed results indicate that fuel switching in the power generation sector is the most cost–effective in the measures evaluated in this study. Then, fuel switching in industry heat, utilization of exhaust heat and CO2 recycling follow in order of cost–effectiveness.

This paper aims at evaluating technologies to realise a sustainable energy system within the constraints of resources and environment. For this purpose, we first developed a database to estimate life cycle efficiencies and greenhouse gas emissions for various energy technologies. Then, on the basis of this life cycle assessment, we quantitatively define the concept of sustainability limitations on resource depletion and environmental emissions. From this concept, the present energy system of the world is judged to be unsustainable from both resource and environmental viewpoints. Then, various mitigation measures such as disposal of CO2 and solar power generation are evaluated utilising the concept. The evaluated result showed how sustainability influences cost–effectiveness of the measures. At the same time we clarified the key points to realise a sustainable energy scenario in ultra–long term.

In recent years, human activities have begun to seriously influence local and global environments. Under the circumstances, Life Cycle Assessment (LCA) is expected to be a powerful tool in evaluating impacts on environments. However, LCA is not yet established methodologically or formulated systematically. The main problems are: 1. Estimation of the repercussions of the activity of a main product on others. 2. Allocation of resource consumption or emission between a main product and recycling or cascading products. 3. Allocation of resource consumption or emission between a main product and co–products in a combined production. In this context, we have developed novel LCA procedures using linear programming (LP), an allocation method using the best base inverse matrix of LP (BI–allocation) and investigated passenger cars as an example. As a result of these procedures, the repercussion effect and allocation problems are systematically calculated and it is proved that BI–allocation makes a system more suitable than allocation by product weights.

For a traffic control of ships passing the control region arbitrarily, optimization techniques can be utilized to get smooth and safe courses avoiding dangerous encounters where miss distance and destination error for each ship are evaluated as a criterion function. To realize such optimal course selection, however, reliable communication systems are indispensable, because ships may take the nearest courses just beyond the miss distance.In the paper, a communication system using conventional marine radars is proposed to realize mutual communication between ships and/or the control station. In the proposed system, control information such as position or velocity of each ship is broadcast to surrounding ships by PPM (pulse position modulation) of radar pulse with dual-k convolutional coding. The information is broadcast, divided into 4 subframes corresponding to each scan of the radar antenna, and those subframes of different radars are identified by detecting the preamble uniquely specified to each radar. The data of 80 bit length can be broadcast within 20 seconds using conventional radars.Use of the coding technique as well as the PPM ensures reliability of the communication, enabling each receiver to separately extract correct information of other ships in heavy radio interference environment. The applicability of the system is evaluated for the situation investigated in the previous papers. From the investigation, it is shown that the overall error rate of the communication system, taking account of false preamble error and decoding error, is less than 10-5 over 99.99999% of the total time, which is regarded sufficient for such purposes.