In the heart of China, researchers are tackling a pressing issue for the solar power industry: how to keep solar power towers running smoothly when clouds roll in. Jing Nie, a researcher at the Zhejiang University of Water Resources and Electric Power, has been delving into the intricacies of Direct Normal Irradiance (DNI) fluctuations—essentially, how changes in sunlight intensity affect solar power towers. Her work, recently published, offers a roadmap for optimizing solar power tower operations, with significant implications for the energy sector.
Solar power towers, or Concentrated Solar Power (CSP) plants, use mirrors called heliostats to focus sunlight onto a receiver at the top of a tower. This intense heat is then used to generate electricity. However, when clouds pass by, the amount of sunlight hitting the receiver can fluctuate dramatically, causing rapid temperature changes that can damage the system. “These fluctuations can lead to thermal stresses on the receiver, potentially reducing its lifespan and increasing maintenance costs,” Nie explains.
Nie’s research, conducted with colleagues at the School of Mechanical Engineering, focuses on developing operational strategies to mitigate these issues. By categorizing different types of DNI fluctuations, the team created a 3D model to simulate the effects of various operational strategies on the outlet temperature of molten salt and the rate of temperature change in the receiver’s tubes.
The findings are compelling. For instance, during periods of high DNI fluctuations, the team recommends defocusing the heliostat field—essentially, adjusting the mirrors to reduce the concentration of sunlight on the receiver. This strategy can help protect the receiver from thermal stress. “Under long-time high fluctuations and moderate fluctuations with high dispersion, defocusing the heliostat field is the way to go,” Nie states.
However, the strategy isn’t one-size-fits-all. For periods of moderate or low fluctuations, maintaining the rated outlet temperature of 565°C is sufficient. But there’s a catch: to prevent rapid temperature changes, the flow of molten salt needs to be increased before and after periods of low DNI.
The economic implications are significant. While implementing these operational strategies reduces electricity generation by about 3.39%, the increased lifespan of the receiver leads to a 2.17% reduction in the Levelized Cost of Energy (LCOE). In other words, the initial loss in generation is more than offset by the long-term savings.
This research, published in the journal Scientific Reports, which translates to Reports of Science, could shape the future of solar power tower operations. By providing a clear framework for managing DNI fluctuations, it offers a path to more efficient and cost-effective solar power generation. As the energy sector continues to evolve, such innovations will be crucial in making solar power a more viable and sustainable option.
For solar power companies, the takeaway is clear: adapting operations based on real-time DNI data can lead to significant savings and improved system performance. As Nie puts it, “The key is to understand the specific conditions and apply the right strategy.” With this research, the industry has a new tool to navigate the challenges of solar power generation, paving the way for a brighter, more sustainable future.
