都市の省エネルギー方策に関する基礎的研究

University of Tokyo (東京大学

Static analysis of triple-effect adsorption refrigeration with compressor

In order to improve the efficiency of the adsorption refrigeration cycle, this study proposes a triple-effect adsorption refrigeration cycle equipped with a compressor. This cycle can run in order to create a large variation in adsorbent concentration range by the compressor, even if there is little temperature variation in the desorption and adsorption processes. The objective of this study is to clarify the effect that regulating adsorption pressure using a compressor has on the adsorption refrigeration cycle, and to that end cycle efficiency was calculated using a static analysis based on a state of equilibrium. As a results from the simulation, the triple-effect cycles can operate by regulating adsorption pressure. Both COP and exergy efficiency can be improved by a factor of 1.2 if the cycled is regulated the adsorption pressure of each cycle rather than using a shared adsorption pressure. For heat sources in the temperature range of 70–100 °C, this method is superior in terms of COP and exergy efficiency. COP values of approximately 1.7–1.8 can be obtained, which is three times higher than single-effect cycles. The triple-effect cycles have one-third the SCE of single-effect cycles but about the same SCE as double-effect cycles

Evaluation of an Additional Generator on the Economic Effect Based on a Load Sharing Optimization of Medium-Speed/High-Speed Diesel Generators in a Microgrid

This study investigates the additional installation of a high-speed diesel generator to independent microgrids (MG) such as remote islands where relatively efficient medium-speed diesel generators (DGs) are mainly used. While small-sized and lightweight, high-speed DGs are not widely spread for continuous usage because their efficiency is lower than that of the medium-speed DGs. The objective of this study is to evaluate the performance of the new method of load sharing optimization to improve the economy by interconnecting a high-speed DG to an independent MG where the medium-speed DGs are operated. The study investigates the effect of operation cost reduction by installing the new load sharing method of operation following the load sharing pattern derived by the mixed-integer programming. As a result of this study, there was some effect to installing a high-speed DG operated by the conventional method. In addition, by adding the new method of load sharing with optimization, the economic effect became even higher

Evaluation of an Additional Generator on the Economic Effect Based on a Load Sharing Optimization of Medium-Speed/High-Speed Diesel Generators in a Microgrid

This study investigates the additional installation of a high-speed diesel generator to independent microgrids (MG) such as remote islands where relatively efficient medium-speed diesel generators (DGs) are mainly used. While small-sized and lightweight, high-speed DGs are not widely spread for continuous usage because their efficiency is lower than that of the medium-speed DGs. The objective of this study is to evaluate the performance of the new method of load sharing optimization to improve the economy by interconnecting a high-speed DG to an independent MG where the medium-speed DGs are operated. The study investigates the effect of operation cost reduction by installing the new load sharing method of operation following the load sharing pattern derived by the mixed-integer programming. As a result of this study, there was some effect to installing a high-speed DG operated by the conventional method. In addition, by adding the new method of load sharing with optimization, the economic effect became even higher

Two model analyses of the urban structure of minimal transportation energy consumption

The transportation sector needs to reduce fuel consumption to deal with global warming because it depends on fossil fuels strongly and it seems to be difficult to substitute other fuels. This study aims at investigating an optimal land use in urban areas from the viewpoint of reducing energy consumption for transportation. For this purpose, the authors developed two kinds of models. One minimizes the total trip length under the condition of constant congestion. The other minimizes the fuel consumption directly where congestion is taken into account endogenously. The optimal structures calculated numerically illustrate that business areas are located around the center of a city while residential areas are on the suburbs, which is similar to the actual land use observed generally. These results are compared with the land use of the central business district (CBD) in Tokyo.Urban land use Transportation Energy consumption Congestion

Optimum Settings for a Compound Parabolic Concentrator with Wings Providing Increased Duration of Effective Temperature for Solar-Driven Systems: A Case Study for Tokyo

We designed a compound parabolic concentrator (CPC) with wings angled toward the east and west. Normally, solar collectors are straight, facing south, and the effective temperature is only achieved for a short period of time at midday. In the proposed design, the collector is divided into three parts, with the ends angled and tilted at different orientations. The objective was to increase the duration of the effective temperature period by capturing the maximum solar energy in the morning and afternoon without tracking by the collector. A simulation model was developed to evaluate the performance of the proposed CPC. The tilt and bending angles of the CPC wings were optimized for year-round operation in Tokyo, Japan. A 35° tilt for the south-facing central part of the CPC and a 45° tilt for the wings with 50° angles toward the east and west were found to be optimal. Analyses were conducted at these optimum settings with temperatures of 70, 80, and 90 °C as minimum requirements. The effective duration increased by up to 2 h in the winter and up to 2.53 h in the summer using the proposed CPC. The proposed CPC will improve the efficiency of solar-driven systems by providing useful heat for longer periods of time with the same collector length and without the need for tracking

The adoption of cogeneration in the Japanese manufacturing sector : technological, economic and institutional determinants

Combined heat and power (CHP) has been identified by the Second and Third Assessment Report of the Intergovernmental Panel on Climate Change as a powerful carbon abating technology. In this paper, we review trends and overall changes in power generation technologies insofar as these affect industrial CHP in Japan; we also propose an empirical model for the analysis of CHP adoption based on time series cross-sectional (panel) data. This is followed by a discussion on current energy policy targets towards CHP and the changes in steam capacity (process heat) that have occurred during the period 1985-1998. Site information on 1500 CHP sites was gathered and combined with industrial statistics for a 14 year span during which Japanese power markets underwent deregulation. Based on the panel regression, we found that an increase in the probabilities of installing new CHP will be linked with a unit increase in purchased power, industrial production and consumption of self-generated power, while a unit increase in non-CHP boiler steam capacity will decrease the probability of adding CHP for the 7 industries. The fixed effects model showed that CHP faces increasing returns to scale over the period 1985-1998. Empirical work on CHP on cross sectional studies carried elsewhere confirms some of our findings. Additionally, it is found that adoptions of CHP are linked to the small to medium size industrial plants since the latter account for the mass of steam capacity retired

Modelling the adoption of industrial cogeneration in Japan using manufacturing plant survey data

Electric power deregulation in Japan opens opportunity for further penetration of on-site generation (cogeneration) otherwise known as distributed generation. In the paper the authors present a survey on Japanese industrial plants to fill existing gaps for the assessment of modern cogeneration (combined heat and power, CHP). The objective of the paper is to empirically examine CHP systems based on cross-sectional binary models; second to review diffusion trends of CHP by system vintage during the 1980–2000 period in the manufacturing sector. The econometric results point that the probabilities of embracing this technology increase, in declining importance, with on-site power consumption, and steam demand, operational hours as well as with payback period, purchased power. For example the survey shows that the CHP is used for the purpose of exporting power rather than meeting the plant’s own consumption. Some of our results are in line with those of Dismukes and Kleit (Resource Energy Econ. 21 (1999) 153) as well with Rose and Macdonald (Energy J. 12(12) (1991) 47). We also find that a unit increase in satisfaction with CHP will lead to a 54% in CHP capacity. We find significant evidence on the cost effectiveness of CHP under conservative assumptions. Regarding the influence of satisfaction and performance indicators for the several plants, the survey threw some unexpected evidence on the nature of CHP

Performance Evaluation of a Solar Adsorption Refrigeration System with a Wing Type Compound Parabolic Concentrator

Simulation study of a solar adsorption refrigeration system using a wing type compound parabolic concentrator (CPC) is presented. The system consists of the wing type collector set at optimum angles, adsorption bed, a condenser and a refrigerator. The wing type collector captures the solar energy efficiently in the morning and afternoon and provides the effective temperature for a longer period of time compared to that achieved by a linear collector. The objectives of the study were to evaluate the system behavior, the effect of wing length, and to compare the performance of the systems with wing type and linear CPCs. A detailed dynamic simulation model was developed based on mass and energy balance equations. The simulation results show that the system performance with wing type CPC increases by up to 6% in the summer and up to 2% in the winter, compared to the performance with a linear CPC having same collector length. The ice production also increases up to 13% in the summer with the wing type CPC. This shows that the wing type CPC is helpful to increase the performance of the system compared to the linear CPC with the same collector length and without the need for tracking