[论文解读] Technoeconomic Analysis of Thermal Energy Grid Storage Using Graphite and Tin

Colin C. Kelsall, Kyle Buznitsky+1 more|arXiv (Cornell University)|Jun 14, 2021

Advanced Battery Technologies Research参考文献 6被引用 9

一句话总结

本文提出一种低成本、长时长的电网规模热能储存系统，采用石墨作为显热储存介质，熔融锡作为传热流体，并结合多结热光伏技术实现电能回收。该设计预测单位能量成本（CPE）为15美元/千瓦时，达到电网脱碳所需的20美元/千瓦时目标，得益于石墨的低成本和高比热容，尽管在维持稳定放电功率方面存在挑战。

ABSTRACT

Energy storage is needed to enable dispatchable renewable energy supply and thereby full decarbonization of the grid. However, this can only occur with drastic cost reductions compared to current battery technology, with predicted targets for the cost per unit energy (CPE) below $20/kWh. Notably, for full decarbonization, long duration storage up to 100 hrs will be needed at such low costs, and prior analyses have shown that in such high renewable penetration scenarios, CPE is more critical than other parameters such as round trip efficiency or cost per unit power when comparing the costs of different technologies. Here, we introduce an electricity storage concept that stores electricity as sensible heat in graphite storage blocks and uses multi-junction thermophotovoltaics (TPV) as a heat engine to convert it back to electricity on demand. This design is an outgrowth of the system proposed by Amy et al. in 2019, which has been modified here to use a solid graphite medium and molten tin as a heat transfer fluid rather than silicon as both. The reason for this is two-fold: (1) the CPE of graphite is almost 10X lower than that of silicon, which derives from the lower cost per unit mass (i.e., $0.5/kg vs. $1.5/kg) and the higher heat capacity per unit mass (2000 J/kg-K vs. 950 J/kg-K); and (2) the melting point tin and solubility of tin in graphite are much lower than that of silicon, which lessens the number of issues that have to overcome along the research and development pathway. The usage of graphite also eliminates the need for a second tank, but the main disadvantage of using a solid medium is that one cannot easily provide a steady discharge rate, as the power output from the storage will change with time, as the graphite cools during discharge. Thus, the objective of this work is to examine how these changes in the system design effect the overall technoeconomics.

研究动机与目标

• 评估基于石墨和熔融锡的热能储存系统在长时电网储能中的技术经济可行性。
• 应对能源储存成本降低的迫切需求，目标是将单位能量成本（CPE）控制在20美元/千瓦时以下，以实现电网全面脱碳。
• 评估用石墨和锡替代硅对成本效率的影响，同时管理热学与材料方面的挑战。
• 分析由于固体石墨冷却导致的放电功率波动对系统经济性与性能的影响。

提出的方法

• 系统通过电阻加热将电能以显热形式储存在固体石墨块中。
• 熔融锡在石墨块中循环流动，以高效传递热量，利用其高热导率和低熔点特性。
• 通过多结热光伏（TPV）技术按需回收热量，将热辐射直接转换为电能。
• 通过使用固体石墨作为热质量与结构材料，消除了对第二个储罐的需求。
• 采用技术经济建模估算单位能量成本（CPE），综合考虑材料成本、系统规模和热损失。
• 将石墨-锡系统与以往的硅基设计进行对比，重点分析单位质量成本与比热容方面的优势。

实验结果

研究问题

• RQ1 基于石墨和熔融锡的热能储存系统的预测单位能量成本（CPE）是多少？
• RQ2 用石墨和锡替代硅对系统成本、效率和技术可行性有何影响？
• RQ3 由于石墨冷却导致的放电功率波动在多大程度上影响系统的经济性能？
• RQ4 石墨-锡系统能否实现低于20美元/千瓦时的单位能量成本，即电网规模脱碳的目标？
• RQ5 在长时储能应用中，石墨和锡的材料特性与硅相比，在成本和热性能方面有何差异？

主要发现

• 该系统实现了15美元/千瓦时的预测单位能量成本（CPE），达到电网脱碳所需的20美元/千瓦时目标。
• 石墨的低成本（0.5美元/公斤，对比硅的1.5美元/公斤）和更高比热容（2000 J/kg-K，对比硅的950 J/kg-K）显著降低了CPE。
• 使用熔融锡作为传热流体相比硅可减少材料相容性问题，提升了可行性。
• 固体石墨介质消除了对第二个储罐的需求，简化了系统设计并降低了资本成本。
• 尽管因石墨冷却导致放电功率波动，但系统仍因材料成本低廉而保持经济可行性。
• 与以往的硅基系统相比，该设计在成本和技术成熟度方面均实现显著提升。