Evaluating the Potential of Variable Renewable Energy for a Balanced Isolated Grid: A Japanese Case Study

There is a global push to develop renewable energy to further a low-carbon society. However, the nature of variable renewable energy (VRE) sources such as wind power and solar photovoltaic (PV) systems may create problems because electricity grids require a stable power supply to match demand. To evaluate the potential capacity of VREs that may be installed, we develop an optimized model that balances power supply and demand and also considers grid balancing by battery storage and load frequency control. The model was applied to a case study of an isolated grid on a remote Japanese island. When set to optimize the grid in terms of lowest cost, the model suggested that, compared with the base case, the capacity of wind power should be increased by a factor of 1.7 and 15.8 for situations without and with battery storage, respectively. Since it was always considered to be more expensive than wind power, no change in solar PV capacity was observed. These approaches resulted in a decrease in the total power generation cost of 2% and 24%, respectively, while total CO2 emissions fell by 3% and 52%, primarily driven by decreased used of the existing fossil-fueled thermal plant

The Right Place for the Right Job in the Photovoltaic Life Cycle

The potential for photovoltaic power generation (PV) to reduce primary energy consumption (PEC) and CO₂ emissions depends on the physical locations of each stage of its life cycle. When stages are optimally located, CO₂ emissions are reduced nearly ten times as much as when each stage is located in the country having the largest current market share. The usage stage contributes the most to reducing CO₂ emissions and PEC, and total CO₂ emissions actually increase when PV is installed in countries having small CO₂ emissions from electricity generation. Global maps of CO₂ reduction potential indicate that Botswana and Gobi in Mongolia are the optimal locations to install PV due to favorable conditions for PV power generation and high CO₂ emissions from current electricity generation. However, the small electricity demand in those countries limits the contribution to global CO₂ reduction. The type of PVs has a small but significant effect on life cycle PEC and CO₂ emissions

Impacts of city-block-scale countermeasures against urban heat-island phenomena upon a building's energy-consumption for air-conditioning

This study quantifies the possible impacts of urban heat-island countermeasures upon buildings' energy use during summer in Tokyo metropolis. Considering the dependency of the buildings air temperature upon the local urban canopy structure, Tokyo urban canopies were classified in the city-block-scale using the sky-view factor (svf). Then, a multi-scale model system describing the interaction between buildings' energy use and urban meteorological conditions was applied to each classified canopy. In terms of urban warming alleviation and cooling energy saving, simulations suggested that the reduction in the air-conditioning anthropogenic heat could be the most effective measure in office buildings' canopies, and that vegetative fraction increase on the side walls of buildings in residential canopies. Both measures indicated daily and spatially averaged decreases in near-ground summer air temperature of 0.2-1.2 °C. The simulations also suggested these temperature decreases could result in the buildings' cooling energy-savings of 4-40%, indicating remarkable savings in residential canopies. These temperature drops and energy savings tended to increase with the decrease of the svf of urban canopies.Urban heat-island Mitigation measures Urban canopy model Building energy-simulation Urban energy conservation

Development of a numerical simulation system toward comprehensive assessments of urban warming countermeasures including their impacts upon the urban buildings' energy-demands

One of the detrimental effects caused by the urban warming phenomena is the increase of energy consumption due to the artificial air-conditioning of buildings in summer. In greater Tokyo, the temperature sensitivity of the peak electricity demand reaches up to 3%/°C in recent years, and about 1.5 GW of new demand is required as the daily maximum temperature increases by 1.0 °C. This huge demand for summer electricity is considered to be one of the common characteristics of big cities in Asian countries. In order to simulate this increase in cooling energy demands and to evaluate urban warming countermeasures from the viewpoint of buildings' energy savings, a numerical simulation system was developed adopting a new one-dimensional urban canopy meteorological model coupled with a simple sub-model for the building energy analysis. Then, the system was applied to the Ootemachi area, a central business district in Tokyo. Preliminary verification of the simulation system using observational data on the outdoor and indoor thermal conditions showed good results. Simulations also indicated that the cut-off of the anthropogenic heat from air-conditioning facilities could produce a cooling energy saving up to 6% with the outdoor air-temperature decrease by more than 1 °C in the summer urban canopy over Ootemachi area.Urban warming countermeasure Anthropogenic heat Urban canopy layer Cooling energy conservation