Objective. This paper briefly reviews the recent trends of photovoltaic power generation systems（PV systems）and its implications to LCA, including the results of reports written in Japanese.
Results. It has been summarized that the PV systems’ energy payback time（EPT）and greenhouse gas（GHG）emission have been practical - even in the worst, minor-case, outdated scenarios. Current typical EPT for the most major polycrystalline silicon PV systems are around 2-3 years, while the GHG emission is generally below 50g-CO2eq/kWh, when assuming a Japanese insolation and a 30-years lifetime. Newly emerging technologies and expansion of the production volume are further cutting down the EPT and GHG emissions.
Conclusions. The energy payback time and greenhouse gas emissions from PV systems have greatly reduced within the recent decade. Whenever evaluating these aspect of PV systems, it is crucial to refer to the latest data.
A photovoltaic power generation system（PVS）is one of the promising measures to develop a low carbon society. For realizing high penetration of PVS, further cost reduction is necessary, while several other challenges would remain. Following the brief introduction of recent trend of PVS market, this paper reviews two issues, i.e. a long-term reliability of PVS and the impacts of high-penetration PVS on electric power system. A long-term stability of PVS is one of the important issues, because the CO2 emission from the manufacturing process of PVS is relatively high compared with other generators. This paper introduces the recent activity of PVRessQ!, which suggests that mechanical faults/failures can be detected in PVS used for just several years. As for the impact of high-penetration PVS, the widely dispersed penetration would be essential measure by considering the results of recent studies about so-called smoothing effect due to the time difference in power output patterns. Therefore, this paper discusses possible measures against some negative impact, focusing on measures from social point of view to realize the widely dispersed penetration.
In Japan, large penetration of PV power generation is expected as a measure to cope with global environmental issue and energy security. The penetration may cause deterioration of stability, power quality and safety of the utility grid. In the paper, issues on the grid operation due to the large penetration of PV power generation are introduced. Concept of proposed Japanese style smart grid including distribution system area, transmission system area and customer side to cope with the issues and R&D results concerning the smart grid techniques using ICT, power electronics, demand side management, etc. are indicated based on CRIEPI’s research experiences to date.
Objective. The batteries spread mainly on a lead-acid battery for cars. A nickel-metal-hydride battery and a lithium-ion battery were put to practical use in 1990's, and then these new batteries have spread rapidly because of high energy density. Recently, large-scale batteries for electric load leveling are attracted a great deal of attention for global environment. We have estimated the effects of batteries for electric load leveling as a case study. Energy and environmental loads on four types of batteries of lead-acid（PbA）, nickel-cadmium（NiCd）, nickel-metal-hydride（NiMH）and lithium-ion（Li-ion）batteries were analyzed for high-efficiency usage of electricity using a life cycle assessment method. The net total efficiency was estimated considering loads on the material process such as production, manufacturing and use. This total efficiency was calculated with the ratio of the life cycle discharged energy to the life cycle input energy. The CO2 emission intensity was also analyzed for the electric-load leveling.
Results and Discussion. In case of using the nighttime electricity, the CO2 emission intensity for the battery system decreased to almost the same level for the CO2 intensity of the daytime electricity. In particular, the lithium-ion battery showed the smallest loads. The effects of use conditions for the battery such as the depth of discharge（DOD）and the discharge rate（C rate）were then analyzed. It was clarified that the CO2 emission intensity was varied according to the use condition.
Conclusions. Large-scale batteries for electric load leveling are expected to use widely for not only industrial sector but also electric vehicles and residential photovoltaic system. It is promised that large-scale batteries are going to play an important role in electric load leveling in the near future.
Objective. The energy consumption of Japanese residential sector has increased about 24% for the last two decades. Heat pump and photovoltaic system are effective to reduce CO2 emissions. In this study, we have evaluated effects of heat pump and photovoltaic system in consideration of temperature and solar irradiation for each region in Japan. Generally, COP of heat pump depends on outside air temperature and generated energy from photovoltaic system is different by individual regions due to differences in solar irradiation and temperature. Results and Discussion. In all regions, photovoltaic system can reduce the CO2 emissions larger than 600 kg-CO2/year, heat pump can reduce that larger than 200 kg-CO2/year considering the average CO2 emission intensity of Japanese electric power companies. The amount of CO2 reduction in Tokyo is largest. On the other hand, the amount of CO2 reduction in Sapporo is smallest because of low COP in winter. In the case of photovoltaic system with Pb-battery system, the amount of CO2 emission reduction increase more than the double in all regions. Conclusions. The effects of heat pump and photovoltaic system are evaluated for each region in consideration of temperature and solar irradiation. In the case using the each CO2 emission intensity of each Japanese electric power company, photovoltaic are very attractive for install. However, heat pump system is not suitable for the region with high CO2 emission intensity on electricity. Pb-battery system is effective for photovoltaic system for storage in case there is surplus electricity. For heat pump system, the improvement of COP at low temperature enables the more reduction of CO2 emission. The annual amount of CO2 emission reduction in Sapporo with heat pump system will increase with improving COP of 5%.
Objective. Some social changes, such as increment of occupied female population or aged population, effect on households’ dietary habit. In general, menus with small number of dishes or using more home-meal replacement become to be more popular than before. The environmental impacts of such changes, however, has not been clear in previous studies. In this paper we inquired about actual condition of households’ dietary habit and estimated environmental impacts of 12 “representative menus” which reflect usual consumers’ everyday eating habit. The final goal of our research is to evaluate LCA effects of households’ dietary habit caused by social reasons as mentioned above. Results and Discussion. The data were assembled by questionnaires from randomly-selected 194 households in Kanto Area of Japan (Tokyo, Kanagawa, Saitama and Chiba) about menu and food ingredients used for each menu on everyday meals (3 meals [breakfast, lunch, dinner] for 365 days). Based on analyses of the households data, we found that the availability of home-meal replacement and the choice of menu type (Japanese, Western, Chinese cuisines) have affected by several factors such as available spare time for cooking, rate of family involvement to a meal, and wife’s age. Based on the data we set 12 “representative menus”, and estimated the LCA impacts from each of them. As a result, the LCA impact of Japanese style menu has relatively small although it has relatively many dishes. On the other hand, the LCA impact of Western style menu has relatively large although it has relatively small dishes. Conclusions. Using the results of LCA impacts from the representative menus, we estimated the change of CO2 emission induced by dietary habit which occurs when occupied female population or aged population will grow. To avoid increasing emission of CO2 induced by dietary habit, it will be effective to use home meal replacement or restaurant service appropriately as well as to reduce cooking energy.
Objective. Domestic woods are generally recognized as eco-friendly material compared with imported ones because of its short distance for transport. However, there are not so many studies looking at GHG emissions between domestic and imported woods based on life cycle thinking. In this study, we estimate GHG emissions from log production and manufacturing to the point of consumption in Japan of domestic and imported wooden building materials, using life cycle inventory analysis. The products were classified as follows from view point of its origin in order to get more reliable results in this study. 1) The term “domestic products” means products are manufactured in Japan from raw material to product. 2) The term “quasi-domestic products” means products are manufactured in Japan except raw materials, i.e., raw materials for quasi-domestic products are manufactured abroad. 3) The term “imported products” means products are manufactured abroad from raw material to product. Results and Discussion. In a comparison of GHG emissions under the same energy conditions of the boiler, the emissions of “domestic products” were lower than that of “quasi-domestic products”, but were not always lower than that of “imported products”. These are two major reasons. One is that the structure of electricity causes a significant decrease in the emissions from the production process in foreign country. The other is that the emissions from product transportation are not so great because density of the products are lower than that of logs, and energy consumption of a ship for a unit product is smaller than that of a truck. Conclusions. The results showed that environmental superiority of the wooden building materials should not judged only by the transportation miles. In carrying out a life cycle inventory analysis of the imported wooden building materials, it is necessary to set up the evaluation condition such as the electrical power consumption rate, the energy source of the boiler, the pathway and means of its transportation. While it is important for “domestic products” to use factory waste wood for the boiler, there is limitation to reduce the emissions from the production process because of constraint of the electrical power consumption rate. To supply more eco-friendly wooden products, we have to consider how to reduce the transportation distance of logs.