Satellite data improves understanding of solar energy generation in Asia-Pacific
Amid the ongoing energy crisis and the growing threat of climate change, the need to harness renewable energy sources has become increasingly urgent. Solar energy in particular is emerging as a leading candidate, with experts predicting that solar energy could become the primary energy source by the end of the century.
However, solar energy generation is not without challenges. Like wind energy, solar radiation – the amount of sunlight available in a given region – can fluctuate significantly due to weather conditions, leading to variations in energy output. These variations can disrupt power grids and make it difficult to meet energy demands consistently. Therefore, understanding how solar radiation changes over time and in different locations is essential to determine the best locations for solar power plants.
In response to this need, a research team led by specially appointed Assistant Professor Hideaki Takenaka from the Center for Environmental Remote Sensing at Chiba University conducted an extensive study to better understand solar radiation in the Asia-Pacific region. Their findings, published in the July issue of ‘Solar Energy’ and made available online on June 13, 2024, provide valuable insights into how solar radiation varies in both space and time. The research team included Kalingga Titon Nur Ihsan and Atsushi Higuchi from Chiba University, as well as Anjar Dimara Sakti and Ketut Wikantika from Institut Teknologi Bandung.
The study used data from Japan’s Himawari-8 and Himawari-9 satellites, which capture high-resolution images of the Asia-Pacific region. The researchers used AMATERASS solar radiation data, which is derived from real-time analysis synchronized with geostationary satellite observations. AMATERASS was developed by Dr. Takenaka and his team and use neural networks to perform fast radiative transfer calculations, allowing accurate estimates of solar radiation. This data, collected over a period of 16 years and made public by CEReS DAAC of Chiba University, has been downloaded more than 186 million times and used in numerous research and national projects in Japan.
By analyzing the solar radiation data over a 20 by 20 km grid at ten-minute intervals, the researchers were able to estimate the variability of solar radiation both in space and in time. Their analysis revealed a number of important findings. For example, they found that regions near the equator experience less fluctuations in solar radiation over time compared to higher latitudes, mainly due to rain and cloud activity. In addition, areas at higher altitudes showed greater variability due to increased cloud activity. The Tibetan Plateau in particular showed significant seasonal changes in the ‘umbrella effect’, a measure of the amount of solar energy reflected back into space. “Our evaluations based on spatiotemporal data revealed features that would have been impossible to achieve with a traditional approach that relies on simple long-term averages or TMY (Typical Meteorological Year) as typical solar irradiance data,” said Dr. Takenaka.
The research team also evaluated the performance of more than 1,900 existing solar power plants using annual and seasonal data. They found that many of these plants experience suboptimal production from June to August due to the umbrella effect caused by clouds. This finding suggests that regions hit hard by these conditions should not rely solely on solar energy during these months.
Finally, the study examined the optimal configuration for future solar power plants. The researchers concluded that a more distributed approach to solar power generation, involving smaller photovoltaic systems spread over a large area, would be more effective at reducing rapid fluctuations in power production than large, centralized solar power plants. “Based on the spatial and temporal characteristics of solar radiation, we suggest that it should be possible to suppress rapid fluctuations in solar energy production by spreading small photovoltaic systems over a large area rather than relying on large solar power plants,” says Dr. Takenaka. explained. “It is worth noting that these conclusions come from weather and climate research, and not from an engineering perspective.” Rooftop solar panels, which are becoming increasingly popular in many countries, could play an important role in this strategy.
These findings will contribute to more effective solar energy generation planning in the Asia-Pacific region, supporting sustainable energy development and combating climate change.
Research report:Solar irradiance variability around Asia-Pacific: Spatial and temporal perspective for active solar energy utilization
