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| Fig. 1: Illustration of the nuclear-solar power concept. (Image Source: I. Nafi) |
Our world is experiencing rapid climate change as the utilization of fossil fuels have fueled extensive environmental degradation and an energy crisis. Consequently, states have been looking into alternatives to fulfill internal demands and slow down climate change by harnessing possibilities within the renewable energy realm. One of these options has been nuclear power generation, which has taken off since the Cold War era and currently helps fulfill the electrical needs of more than 33 countries. [1] However, given its own challenges, researchers have been looking into ways to optimize the benefits of power generation from nuclear energy, over its tradeoffs, through a possible combination of another renewable energy source.
In recent years, researchers and developers have been experimenting with a combination of nuclear and solar photovoltaic generation systems coupled with an energy storage system, as illustrated in Fig. 1. [2] With solar technology becoming more affordable and mass-produced and newer more cost-efficient ways of energy storage becoming available, this combination brings a lot of promise and potential. Several studies were conducted using load patterns from power plants in states like South Korea to study energy generation and storage demands.
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| Table 1: Detailed comparison of CSP and MMR. [4] |
Considering that the world's energy consumption is estimated to grow by about 50% between 2018 and 2050, researchers and developers have been exploring hybrid renewable energy generation options. [3] One proposed option includes a hybrid system combining solar and nuclear power towers coupled with a thermal energy storage system into one cycle. This system would leverage nuclear power as a main-heater, a solar power tower, and the thermal energy storage as the re-heating mechanism. [3] Studies have shown that this system can reduce the costs of energy generation by 25% compared to a concentrating solar power system (CSP) that's mainly connected to a thermal energy storage system and brings high efficiency and low installation and operating costs. [3]
To examine the energy generation potential, this particular study included developers actualizing a Micro Modular Reactor (MMR) through a combination of a supercritical CO2 power cycle and a small long-life reactor core to supplement a CSP. [3] This hybrid system, which is tailored for microgrids in remote areas, typically has a ceiling of 50 MWe in capacity. [4] A remote region in South Korea was selected since it was comparable to an isolated grid and the results could be mapped to general South Korean electricity demand. In this study, the base demand of the target region was 12 MWe and the annual peak electricity demand was 21 MWe. [3] Considering the annual largest peak to base ratio which is 1.75, the total peak demand comes out to 25.6 MWe which is about 122% of the 21 MWe.[3] Without the solar field, the nuclear plant would only be able to generate about 12 MWe considering it's a smaller reactor with a core that contains a smaller life. [3]
The study found that the MMR could fulfill the demands. The system on average generated about 27.3 MWe. Taking a closer look at the system's performance, when the TES capacity is 200 MWhth, the system can store more energy than 100 MWhth, thus keeping up with the demand for a considerable period of time. [4] As TES capacity increases, more overall demand is fulfilled compared to a lower TES capacity, thus showing how steep the increase of the capacity factor and demand fulfillment ratio is. However, in the case of large TES capacity, for example at 400-800 MWhth, most of the electricity demand is fulfilled except for the 2400-4200 and 5600-7600 h zones.
On top of this, adirect comparison was made between the standard CSP system and the hybrid system. As seen in Table 1, while most outputs are comparable, the hybrid system had a greater capacity factor and electricity demand fulfillment ratio with a smaller solar field area size compared to its standard counterpart.
The hybrid system promises to outshine its standalone CSP counterpart, harnessing the complementary abilities of each energy source to overcome inherent limitations. Even with a solar field area nearly two and a half times smaller, the hybrid system boasts superior metrics: a higher capacity factor and enhanced electricity demand fulfillment ratios. By combining the CSP and MMR, we not only streamline solar field space but also retain MMR's high capacity factor, surpassing what MMR could achieve in isolation.
Yet, challenges exist for broadscale implementation. The hybrid system struggles to attain 100% electricity demand fulfillment, considering weather fluctuations and seasonal variations. Despite an impressive capacity factor of 75% and an electricity demand fulfillment ratio of 95% with an 800 MWhth TES capacity, the hybrid system falls short of the elusive 100% benchmark. Thus despite being designed for a robust 25.6MWe output, achieving full electricity demand fulfillment requires an annual peak electricity demand below this threshold, within a range of TES capacities from 100 to 800 MWhth.
© Itbaan Nafi. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute, and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] J. Kim et al., "Global Radioactive Waste Disposal Trends and Prospects," J. Korean Soc. Environ. Eng. 45, 210 (2023).
[2] C. Lowe et al., "Load Following Capability for Hybrid Nuclear and Solar Photovoltaic Power Plants with an Energy Storage System," 2020 52nd North American Power Symposium (NAPS), IEEE 9449816, 11 Apr 21.
[3] I. W. Son et al., "Feasibility Study of Solar-Nuclear Hybrid System For Distributed Power Source," Energy Convers. Manage. 230, 113808 (2021).
[4] S.-B. Cho and M.-S. Yim, "Examining the Feasibility of Nuclear-Renewable Hybrid Energy System in Korea: A Case-Based Analysis of High Penetrations of Solar Energy," Int. J. Energy Res. 44, 8133 (2020).