Kunkel Sebastian, Seeliger Felix, Hanke Andrea, Bauer Thomas, Bonk Alexander
German Aerospace Center (DLR), Institute of Engineering Thermodynamics, 70569, Stuttgart, Germany.
German Aerospace Center (DLR), Institute of Engineering Thermodynamics, 51147, Cologne, Germany.
Heliyon. 2023 Nov 23;9(12):e22363. doi: 10.1016/j.heliyon.2023.e22363. eCollection 2023 Dec.
Among the variety of energy storage techniques thermal energy storage (TES), based on molten salts, is already in use for the storage of heat in a gigawatt hour scale. At the time of writing virtually all TES in CSP utilize Solar Salt (60 wt-% NaNO and 40 wt-% KNO) due to its competitively low price, low vapor pressure and non-toxicity. On the downside, the operating temperature is limited to 560 °C based on its thermal stability. However, increasing the operating temperature while maintaining thermal stability of the salt using techniques that are realizable in industrial scale remains one of the main challenges. Up to now this could only be achieved in a small scale by flushing with synthetic purge gas or sealing and pressurizing the system, maintaining the necessary gas atmosphere and shifting the chemical equilibrium to the nitrate side. Both methods are hardly realizable in an industrial scale. In this work we show a new strategy to stabilize Solar Salt at 620 °C by combining the gas-purged configuration and sealed system with maximum pressure of few tens of millibars in a 100 kg scale. The formed gas phase was within the expected range in terms of oxygen and nitrous gases. Additionally, the concentration of the nitrate and nitrite ions aligned well with salt systems with gas-purged atmosphere at 620 °C. We demonstrate the first experiments on long-term thermal stabilization (4000 h) of Solar Salt at 620 °C in a 100 kg technical-scale. These findings represent an important step in the development of modern storage systems.
在各种储能技术中，基于熔盐的热能储存（TES）已在吉瓦时规模的热量储存中得到应用。在撰写本文时，由于其具有竞争力的低价格、低蒸气压和无毒特性，几乎所有聚光太阳能热发电（CSP）中的TES都使用太阳盐（60重量%的NaNO和40重量%的KNO）。不利的是，基于其热稳定性，其工作温度限制在560°C。然而，利用工业规模可实现的技术在保持盐的热稳定性的同时提高工作温度仍然是主要挑战之一。到目前为止，这只能通过用合成吹扫气体冲洗或密封并对系统加压、维持必要的气体气氛并将化学平衡向硝酸盐一侧移动来在小规模上实现。这两种方法在工业规模上都很难实现。在这项工作中，我们展示了一种新策略，即在100千克规模下，将气体吹扫配置和密封系统相结合，在几十毫巴的最大压力下，将太阳盐稳定在620°C。就氧气和一氧化二氮气体而言，形成的气相在预期范围内。此外，硝酸盐和亚硝酸盐离子的浓度与620°C下具有气体吹扫气氛的盐系统吻合良好。我们展示了在100千克技术规模下对太阳盐在620°C进行长期热稳定（4000小时）的首次实验。这些发现代表了现代储能系统发展中的重要一步。
