Heat Utilisation via Thermally Regenerative Electrochemical System

很大一部分低品位热量（<100℃）以太阳能热和住宅建筑和工业废热的形式存在。然而，使用传统的基于固态热电器件的系统转换低品位的热量是具有挑战性的，因为转换效率低，成本效益低。由于氧化还原液流电池的可扩展性，使用热再生电化学循环（TREC）氧化还原液流电池（RFB）进行电化学热-电转换可以被认为是一种有前途的方法，可以确保具有足够高额定功率的低成本低等级储热。尽管有这些优点，TREC RFB的记录转换效率低于6%，远远落后于其理论最大值，在80℃的温度梯度下可以超过20%。这是由于电解质设计没有考虑其热力学和电化学特性，这是基于trec的系统的关键方面。在此，我们建议通过数据和模型驱动的氧化还原化学物质筛选和电解质设计，开发一个高效的基于trec的RFB系统，并开发一个可扩展的演示器。在动态操作参数下，如温度、流量、电导率、电阻等，将进行全面的分析式热电化学模型研究和实证研究，这些参数在TREC设计中非常重要，但研究较少。从实验室规模和大面积多堆叠流动电池获得的长期电流-电压特性将用于使用反馈回路方案（即逆建模过程）进行进一步的模型开发（经验常数和过电位项的其他因变量）。通过数据收集矩阵收集和评估氧化还原对的关键参数，包括但不限于热电（Seebeck）系数、反应熵、溶解度、电导率、反应速率等，然后进行一系列综合的理论和实验筛选步骤。从数量上讲，通过上述活动，该项目旨在提供一种具有破纪录的热-化学-电转换效率的TREC RFB系统（在最大功率密度下，60℃温度梯度下达到10%），相当于卡诺极限的70%。该项目是一项具有挑战性和雄心勃勃的跨学科工程研究，需要广泛的合作。理论建模与氧化还原对的初步筛选和原型系统开发将在Heriot-Watt大学进行，而Strathclyde大学将准备和表征候选氧化还原对的基本特征。为了项目的成功，还将与各种外部专家建立密切的伙伴关系。奥胡斯大学（A. Bentien教授小组）将支持有机化学处理的外部研究停留机会。KIST欧洲（位于萨尔大学）也将为PDRA的研究停留提供最先进的多堆电池测试设施和研究人员支持。爱依斯太阳能有限公司将作为工业合作伙伴参与，为集热器设计提供技术支持。林德有限公司也将为该项目提供商业规模的测试设施。这项工作的成果将成为能源存储和电化学领域的一个重要里程碑。我们设想在高效和耐用的太阳能存储方面取得技术进步，以迅速满足英国零排放未来的时代需求。此外，更重要的是，考虑到最近欧洲的国际武装冲突，该项目的目的满足了能源安全的需要。除了目前英国为碳中和社会制定的可再生能源路线图政策外，该项目也非常适合EPSRC的储能投资组合。

An enormous portion of low-grade heat (<100C) exists in the form of solar heat and waste heat from residential buildings and industries. However, converting low-grade heat using a conventional solid-state thermoelectric device-based system is challenging due to poor conversion efficiencies and low cost-effectiveness. Electrochemical heat-to-electricity conversion using a thermally regenerative electrochemical cycle (TREC) redox flow battery (RFB) can be considered a promising means for securing cost-effective low-grade heat storage with a sufficiently high-power rating due to the scalability of the redox flow batteries. Despite such benefits, the record conversion efficiency of the TREC RFB is less than 6%, which is far behind its theoretical maximum, which can be over 20% at a temperature gradient of 80C. This is attributable to the electrolyte design that does not consider its thermodynamic and electrochemical characteristics, which are the key aspects of TREC-based systems. Herein, we propose developing an efficient TREC-based RFB system through a data- and modelling-driven screening of the redox chemicals and electrolyte design and developing a scalable demonstrator. Comprehensive analytic thermoelectrochemical model studies and empirical research will be carried out under dynamic operational parameters, such as temperature, flow rate, conductivities, resistance and etc., which have been poorly studied despite their high importance in TREC design. The long-term current-voltage characteristics obtained from both lab-scale and large area multi-stack flow cells will be used for further model development (empirical constants and other dependent variables for overpotential terms) using a feedback loop scheme (i.e., inverse-modelling process).Critical key parameters of redox couples, including but not limited to thermogalvanic (Seebeck) coefficient, reaction entropy, solubility, conductivity, reaction rate and etc., will be collected and assessed by using data collection matrix followed by a series of comprehensive theoretical and experimental screening steps. Quantitatively, through the activities outlined above, this project is aimed to deliver a TREC RFB system with a record-breaking heat-to-chemical-to-electricity conversion efficiency (>10% at 60C temperature gradient at maximum power density) which is equivalent to 70% of the Carnot limit.This project is a challenging and ambitious interdisciplinary engineering study, requiring a broad spectrum of collaborations. Theoretical modelling with the initial screening of redox couples and prototype system development will be conducted at Heriot-Watt University, while the University of Strathclyde will prepare and characterise the fundamental characteristics of candidate redox couples. Close partnership with various external experts will also be carried out for the success of the project. Aarhus Univ. (Prof. A. Bentien's group) will support external research stay opportunities for organic chemical treatment. KIST Europe (in Saarland Univ) also will provide access to state-of-the-art multi-stack battery testing facilities and research staff support for PDRA's research stay. AES Solar Ltd. shall participate as an industrial partner, providing technical support for heat-collector design. LIND Ltd. will also support the project with access to their commercial-scale testing facilities. Outcomes from this work will be an important milestone in both energy storage and electrochemistry areas. We envisage technological advances for efficient and durable solar energy storage that promptly meet the needs of the times for the UK's zero-emission future. In addition, more importantly, the purpose of the project meets the needs of energy security considering recent international armed conflicts in Europe. Alongside the current UK's renewable energy roadmap policy for a carbon-neutral society, this project also fits well in the EPSRC's Energy Storage portfolio.