Yutaka Genchi

Influence of Air-Conditioning Waste Heat on Air Temperature in Tokyo during Summer: Numerical Experiments Using an Urban Canopy Model Coupled with a Building Energy Model

Abstract A coupled model consisting of a multilayer urban canopy model and a building energy analysis model has been developed to investigate the diurnal variations of outdoor air temperature in the office areas of Tokyo, Japan. Observations and numerical experiments have been performed for the two office areas in Tokyo. The main results obtained in this study are as follows. The coupled model has accurately simulated the air temperature for a weekday case in which released waste heat has been calculated from the energy consumption and cooling load in the buildings. The model has also simulated the air temperature for a holiday case. However, the waste heat from the buildings has little influence on the outdoor temperatures and can be neglected because of the low working activity in the buildings. The waste heat from the air conditioners has caused a temperature rise of 1°–2°C or more on weekdays in the Tokyo office areas. This heating promotes the heat-island phenomenon in Tokyo on weekdays. Thus, it is ...

CO2 payback–time assessment of a regional-scale heating and cooling system using a ground source heat–pump in a high energy–consumption area in Tokyo

We present an assessment of installing a regional heating and cooling system in the Nishi(West)-Shinjuku area of Tokyo, Japan. In this assessment, we estimate the CO2 payback–time, when air source heat–pumps (ASHP) are replaced with a ground–source heat–pump (GSHP) system. We calculate CO2 emissions from transportation of the cooling tower, materials for the underground heat exchanger, and the digging loads and transportation loads incurred when the GSHP system is installed to replace the air source cooling system. The total CO2 emission from the installation of the GSHP system was estimated to be 67,701t-CO2, with 87% of the CO2 emissions resulting from the digging process. CO2 emissions from the operation of the GSHP system were estimated from the total energy-efficiency of the system and the heating and cooling demand in Nishi-Shinjuku area. Using the GSHP system, 33,935t-CO2 would be emitted per year. We estimate that using the GSHP system would result in a reduction of 54% of the CO2 emissions, or 39,519t-CO2 per year. From these results, the CO2 payback–time for replacing the conventional ASHP in the 1 km2 studied region with the GSHP system is assessed to be 1.7 years.

Life cycle assessment of integrated municipal solid waste management systems, taking account of climate change and landfill shortage trade-off problems

Steps taken to counter the climate change problem have a significant impact on the municipal solid waste management (MSW) sector, which must tackle regional environmental problems such as the shortage of sanitary landfills, especially in Japan. Moreover, greenhouse gas emissions and final disposal have a trade-off relationship. Therefore, alleviation of both these environmental problems is difficult, and Japanese local municipalities are anxious for action to solve these problems and reduce treatment costs. Although ambitious waste management measures have been enacted in many countries, they appear to lack a holistic view and do not adopt a life cycle approach. Therefore, it is important to reconstruct the MSW management system, taking into account environmental and economic aspects. In the present study, life cycle assessment and mathematical modelling were used to seek ways of redesigning the MSW management system in order to minimize environmental impacts and/or reduce treatment costs. One economic block was selected as the study area (Iwate Prefecture in Japan). The life cycle inventory and costs data for every MSW transportation and treatment process in this region were collected and processed. Then, taking account of geographic information, an optimal solution for the minimization of environmental impact or treatment costs was derived. To solve the trade-off problem, a sensitivity analysis was conducted to find optimal reduction targets for climate change and final disposal.

Using a life cycle assessment method to determine the environmental impacts of manure utilisation: biogas plant and composting systems.

The aim of this study was to use life cycle assessment methods to determine the environmental impacts of manure utilisation by a biogas plant and by a typical manure composting system. The functional unit was defined as the average annual manure utilisation on a dairy farm with 100 cows. The environmental impact categories chosen were emissions of greenhouse gases (GHG) and acidification gases (AG). The GHG emissions were estimated as: 345.9 t CO2-equivalents (e) for solid composting (case 1), 625.4 t CO2-e for solid and liquid composting (case 2), and 86.3–90.1 t CO2-e for the biogas plant system. The AG emissions were estimated as: 10.1 t SO2-e for case 1, 18.4 t SO2-e for case 2, and 13.1–24.2 t SO2-e for the biogas plant system. These results show that a biogas plant system produces low GHG emissions, but comparatively high AG emissions with land application. It is suggested that land application using band spread or shallow injection attachments will decrease AG emissions (NH3) from biogas plant systems.

Japanese sleep disturbance and fatigue disability weights in evaluating the effects of increasing temperatures on health by a life cycle approach

PurposeThis study aimed to establish a set of disability weights (DWs) for sleep problems and fatigue which could be applied in composite health outcome measures in order to quantify the burden of symptoms and economically evaluate the effects of increasing temperatures on a life cycle approach.MethodsThe conditions were evaluated by a two-step questionnaire study. In the first step, specialists determined the DW for each condition. The second step was identical to the first, except that the determinations were made by primary care physicians. Both groups of medical practitioners used an interpolation method consisting of a comprehensive set of 31 disease-specific DWs.Results and discussionMean DWs for sleep disturbance were 0.101 for environmental sleep disturbance, 0.069 for mild sleep disturbance, and 0.086 for moderate sleep disturbance. Mean DWs for chronic fatigue syndrome (CFS) were 0.099 for a diagnosis of CFS, 0.164 for mild handicap, 0.281 for moderate handicap, and 0.459 for severe handicap. Mean DWs assigned by primary care physicians for sleep disturbance were 0.114 for environmental sleep disturbance, 0.140 for mild sleep disturbance, and 0.126 for severe sleep disturbance. Those for CFS were 0.154 for a diagnosis, 0.099 for mild handicap, 0.147 for moderate handicap, and 0.226 for severe handicap.ConclusionsUsing the present valuation protocol, it appeared feasible to establish the burden of symptoms as attributable to increasing temperatures. The results can be applied in composite health outcome measures for public health research, environmental research, and economic evaluations.

Potential for Greenhouse Gas Mitigation at a Typical Roughage Production System in the Japanese Dairy System

Increasing domestic roughage production is an important measure in designing a sustainable dairy production system in Japan. However, roughage production is one of the agricultural activities that have a significant environmental impact. The objectives of this study were to reveal potentials of greenhouse gas (GHG) emissions in typical roughage production systems using the life cycle assessment method (LCA). Comparative LCA was conducted to evaluate GHG emissions between the domestic roughage production system and imported hay utilization system. The functional unit of LCA was defined as roughage production at 10a, and GHG/TDN ratio was applied comparing roughage production and GHG emissions of domestic and imported roughages. The results showed that the domestic roughage production system produced 20 % less GHG emissions than the imported hay utilization system. GHG/TDN ratios were associated with the LCA results to compare GHG emissions with production of different roughage production systems.

The Effect of CO2 Information Labelling for the Pork Produced with Feed Made from Food Residuals

In this study, we attempts to evaluate customer reaction to the labelling of food residuals recycling and CO2 reduction for pork, using a web marketing survey and an in-store survey. The results are as follows: (1)The willingness to pay (WTP) for the pork produced with feed from food residuals was approximately an additional 19.3 yen / 100g-pork in comparison with to ordinary Japanese pork; (2) The WTP for life cycle-CO2 (LC-CO2) reduction was approximately an additional 0.4 yen / g-CO2. It can be concluded that many consumers have positive feelings towards pork produced with feed made from food residuals and see added value in this process. Moreover, it is suggested that labels with information concerning resource recycling and LC-CO2 reduction would encourage consumers to purchase the pork produced with feed from food residuals.

Evaluation of the Possibility of Reducing CO2 Emission from Residential Buildings in Cold Districts of Japan by Employing an Micro Gas Turbine Co-Generation System

Introducing a co-generation system is an effective choice for reducing energy derived CO2 emissions and operating costs for the residential and commercial sectors. In this paper, the possibilities of CO2 emission and operating cost reductions were investigated for the case of a micro gas turbine co-generation system being introduced into a 33 household apartment building located in Sapporo, one of the coldest districts in Japan, which demands a lot of energy in winter for hot-water supply and heating.The results were compared with that of the existing system which is composed of an electricity grid and hot water boilers. The CO2 emissions and operating costs of the co-generation system varied according to the ratio of electricity supply from the grid and MGT, MGT generation efficiencies and the season of the year. Using an MGT with an electricity generation efficiency of 35%, a reduction of 10% (23.4 tonne-CO2/y) of CO2 emissions and 9.4% (433ky) of operating costs could be attained compared with the existing system. In the case of a generation efficiency of 30%, a reduction of 3.4 tonne-CO2/y is expected at the same level of operating cost as the existing system. But in the case of a generation efficiency of 25%, there was no signifi-cant reduction in CO2 emission.