• Energy Research

This paper describes the effects of the installation of various countermeasures against urban heat-island (UHI) and energy-saving measures on UHI and global warming. A UHI and energy-consumption simulation model was developed by combining the one-dimensional meteorological canopy and building energy use models; further, the proposed model was expanded to evaluate the year-round air temperature and annual energy consumption. The simulation results showed that the humidification and albedo increase at building-wall surfaces reduced the total number of hours for which the air temperature was more than 30 °C during the daytime by more than 60 (h) per year. The UHI countermeasures reduced the annual energy-consumption despite causing a small increase during the winter period. However, they may result in certain unfavorable conditions for pedestrians. Energy-saving measures, on the other hand, reduce the total number of hours for which the air temperature is more than 30 °C by only a few hours per year. Thus, we demonstrate the effectiveness of the UHI countermeasures and measures against global warming by extending the calculation period from summer to an entire year.

This study focused on the effects of green roofs in office building districts. The purpose of this study was to evaluate the effectiveness of green roofs in the reduction of the urban heat island (UHI) effect and CO2 emissions. These effects consider decreased energy consumption for space cooling, and the amount of water needed for evapotranspiration on the green roofs. A coupled urban canopy/building energy model (CM-BEM) was utilized to simulate the effectiveness of green roofs. The amount of water needed for evapotranspiration was calculated by using latent heat flux, which was derived from the results of roof surface heat balance calculations. The effect of green roofs on CO2 emissions was determined based on their effectiveness to reduce the energy demand for space cooling, calculated by air-conditioning load simulation. We calculated the CO2 emissions from powering the pumps and the use of tap water, when the necessary amount of water was supplied by watering. Finally, the relationships between amount of water, UHI mitigation, and CO2 emissions were determined.

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.

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.

SummaryWe investigate the extent to which Japanese people can change their consumption and the corresponding environmental impact. We propose a new analytical framework with a rebound matrix that captures the monetary flow from potential savings to their respending (referred to as rebound). A questionnaire is used to derive the matrix. On average, respondents spent 3.4 million Yen annually, resulting in 12.4 tons of carbon dioxide (CO2) emissions in their daily lives. The survey results suggest that acceptable spending reductions would correspond to a CO2emissions reduction of nearly 6%. However, the CO2emissions would increase by nearly the same amount when the respondents respend their savable money (rebound CO2emissions). The annual CO2emissions and the annually reducible CO2emissions both increase with the increase in annual expenditure. Consequently, the net CO2emissions also increase with the increase in annual expenditure. The rebound spending is approximated using the rebound matrix. Finally, it is suggested that the net CO2emissions can be reduced through lifestyle changes whereby spending on energy items is reduced and the resulting savings are spent on telecommunication, clothes, shoes, education, and housing.

Abstract In this study, the summertime outdoor heat stress hazard and heat disorder risk (HDR) were simulated, and their changes under several heat island mitigation scenarios were quantitatively evaluated. Gridded maps that included the 23 wards of Tokyo (23 Tokyo) were produced with 1-km horizontal resolution for consecutive summer months, facing extremely hot weathers, in 2010. The wet-bulb globe temperature (WBGT) was adopted as an outdoor heat stress indicator. Numerical simulations were applied to evaluate the effects of several heat island mitigation scenarios—including building greening (GR), high-albedo coating (ALB), and roof-level emissions of all waste heat by air conditioning (WH)—on the WBGT and HDR for 23 Tokyo. Results showed no cases that effectively lowered the outdoor WBGT and HDR for the studied region. Conversely, the ALB case increased the daily maximum WBGT by an average of 0.6 °C (maximum of 1.7 °C) over all the grids. This increase induced a 1.4 (3.3) times higher HDR in the area average (at the maximum grid) compared to a control case with no mitigation scenario. Hence, heat island mitigation methods reflecting solar radiation could potentially lead to an increase in the outdoor heat stress hazard and risk to a large extent in urban areas.

One consequence of increasing agricultural trade is a shift of geographic location of agricultural activity to more economically productive countries. Whether or not the economic efficiency translates to environmental efficiency for agricultural goods is an open question. To examine environmental implications of shifting agricultural location, we analysed the life-cycle greenhouse gas (GHG) emissions of rice production in Japan and the US for the Japanese market in a comparative manner. This paper presents the life-cycle assessment of brown japonica rice. Our computation of GHG emissions of rice production in Japan and the US were 3.54 and 2.99 kgCO2-eq kg-rice−1, respectively. With respect to harvested area, the emissions were 18.4 in Japan and 27.8 tCO2-eq ha−1 in the US. For Japan to be environmentally competitive with the US production, fundamental restructuration of field size is necessary to increase yield. In conclusion, economic efficiency does not translate to environmental efficiency with the case of rice production. Importing rice is both economically and environmentally viable option for the Japanese market.

We conducted a detailed estimation of direct and indirect CO2 emissions related to multi-person households in 49 Japanese cities. Direct energy consumption was decomposed into energy use in order to consider the relationship with regional conditions. The results showed that CO2 emissions from direct energy consumption were almost as large as indirect CO2 emissions induced by consuming products and services, suggesting that lifestyle improvements are important for both energy savings and reducing CO2 emissions relating to product and service consumption. In addition, CO2 emissions from direct energy consumption varied widely between cities, making them susceptible to regional conditions. We also calculated CO2 emissions from direct energy consumption and examined the regional conditions for individual forms of energy use. CO2 emissions were higher in cold regions and lower in larger cities. In Japan, large cities are often located in relatively warm areas, so we conducted an analysis to distinguish the effects of climatic conditions from those of urbanization. This analysis allowed us to clarify the effects of regional conditions on factors such as heating/cooling and the ratio of detached houses to apartments.

Abstract To achieve a low-carbon society, it is crucial to make the transition away from wasteful lifestyles that are shaped by mass production/mass consumption towards low-carbon lifestyles. Research in the field of urban environmental studies examining human behavioral factors affecting energy consumption, has mostly focused on CO 2 emissions relating to direct energy consumption, such as the use of air conditioners and water heaters. As CO 2 emissions from the industrial sector are greater than those from the residential and transportation sectors in Japan, it would be prudent for consumers to work on reducing CO 2 emissions relating to products and services. In an effort to provide some basic research to achieve the aforementioned objectives, this study looked at statistical data from sources such as the Japanese Family Income and Expenditure Survey and the Japanese National Survey of Family Income and Expenditure to estimate direct and indirect CO 2 emissions relating to daily expenditures and consumption. As a case study, we selected a sample denizen to calculate the CO 2 emissions relating to daily living. Based on the obtained results, we examined the lifestyle and consumption patterns and their relation to CO 2 emissions. The results suggest that while it is still important for consumers to reduce their direct energy consumption in an effort to create a low-carbon society, there is still potential for indirect CO 2 emission reductions in areas of production and consumption.