The urgent need for renewable energy sources to combat environmental pollution and ecological damage cannot be overstated. Solar energy presents an attractive solution due to its abundant availability, with the solar energy reaching the Earth’s surface far exceeding global power consumption. Among solar thermal power technologies, parabolic trough concentrator (PTC) solar power systems have gained prominence, accounting for about 75% of solar power capacity due to their mature technology. However, one significant challenge has been the high cost of PTC solar power compared to traditional thermal power generation. Addressing this cost disparity is a primary focus to capitalize on the technology and promote its wide spread use, and the effective approaches are to improve the system efficiency and Increase PTC aperture width. To address these limitations, a recent study published in the Journal of Energy, Dr. Gong Jing-hu, Dr. Li Yong, Dr. Wang Jun, and Dr. Peter Lund from Xi’an University of Architecture and Technology and Southeast University and Aalto university proposed a multi-stage heating PTC system that combines different-shaped absorber tubes (AT) at different temperature sections to maximize thermal efficiency and achieve an outlet temperature of 580°C.
The research team developed a geometric model for the multi-stage large aperture PTC system using a semi-circular AT with two outer fins, a semi-circular AT, and a circular AT. The temperature rises from 300°C at the inlet to 580°C at the outlet through these three ATs, each optimized for its respective temperature range. This multi-stage heating strategy allows for reduced heat loss and efficient temperature control. They validated optical and thermal models using various parameters and conditions, including optical efficiency and thermal efficiency. The validation results confirmed the accuracy and applicability of the models for the proposed multi-stage PTC system. Thermal calculations and analysis further supported the advantages of the multi-stage PTC system. The authors found that thermal efficiency increased with higher Direct Normal Irradiance (DNI) levels, emphasizing the importance of locating solar power stations in regions with abundant solar resources. Additionally, the unique design of the multi-stage system allowed for efficient energy absorption and reduced external radiation loss.
The research culminated in the evaluation of the proposed multi-stage PTC system’s efficiency in generating solar power. The authors’ findings demonstrated that the system in Dunhuang, China, could achieve an annual average solar-to-electric efficiency of 24.5%, with variations based on seasonal DNI levels. The thermal efficiency of the system played a crucial role in achieving such high solar-to-electric efficiency, as it reached an average of 62.3%. This is impressive and significantly outperformed existing solar thermal power stations, which typically have lower thermal efficiencies. In conclusion, the study conducted by Dr. Gong Jing-hu and colleagues presented a promising solution to improve the efficiency and reduce the cost of large aperture PTC solar power systems. The researchers successfully achieved a high thermal and solar-to-electric efficiencies by implementing a multi-stage heating strategy with different-shaped ATs optimized for specific temperature ranges. These findings have profound implications for the future of renewable energy, as they offer a path to harnessing the vast potential of solar power in a cost-effective and environmentally sustainable manner.
Gong Jing-hu, Li Yong, Wang Jun, Peter Lund, Performance optimization of larger-aperture parabolic trough concentrator solar power station using multi-stage heating technology, Energy, Volume 268, 2023, 126640,