Grid Scale Thermal and Thermo-Chemical Electricity Storage

热化学储能（TCES）具有在小空间内以低成本存储大量能量的潜力。这是通过可逆化学反应将热能（“热量”）转化为化学能来实现的。例如，通过将粒状金属氧化物加热到合适的温度和合适的压力，一些氧气被驱除（即，该物质被“还原”）并且在该过程中吸收热量。由此产生的“还原氧化物”是稳定的，可以长期储存而不会降解。当需要时，随后可以通过使高压空气通过还原的氧化物来回收热量。然后空气中的一些氧气被吸收，但剩余的气体被反应加热，并且（因为它也处于高压下）可以用于驱动气体涡轮机发电。其他气固反应也是可能的，包括石灰石的“煅烧”（即，将其加热以驱除二氧化碳）和例如氧化钙的水合作用（用蒸汽）。每一种反应都有其自身的特点，可以利用这些特点来发挥其优势。例如，从煅烧反应中产生的二氧化碳可以被压缩和液化。这本身吸收电能（以驱动压缩机），并构成额外的，令人惊讶的紧凑和稳定的能量存储形式，通过使用高压CO2驱动涡轮发电机，可以从中回收电力。与电池相比，TCES具有在电网规模下以低得多的每千瓦时存储容量成本存储能量的潜力，尽管往返效率较低。这是因为TCES系统可以基于单元操作和发电厂技术构建，与电化学系统相比，这些技术容易扩大规模。热化学系统的效率可能在40%至60%的范围内，但是“节能”意味着剩余的能量不需要浪费：它可以用于加热建筑物，提供热水或为工业过程供热。此外，这些系统提供了在没有任何安全危险或加压储存设施的情况下提供长时间储存的可能性。需要评估这些技术如何为各种电网服务做出贡献，所需的规模以及如何最好地在配电网络中定位它们。许多组件具有惯性，这将提供一些频率支持，但热响应可能会限制服务提供，特别是如果还利用废热。在这笔赠款中，我们将开发和测试新材料，以实现更高效和更具成本效益的TCES流程。调查的问题包括材料的循环稳定性，它们的容量和转化率。实验室规模的测试将展示周期的关键方面，并提供设计和建模工作所需的信息，以评估这些过程。我们将对工艺流程进行建模，并提供详细的组件模型，以识别损失并优化工艺和材料组合。为了了解这些技术对社会的价值，我们将进行系统级动态建模，以了解它们在各种情况下提供电网服务的能力，包括为区域/工业供暖应用提供热能的情况。我们将通过采用整体系统方法分析和量化TCES技术的电网规模集成潜力，从而将其与电/热/冷/气网络集成。这将使我们能够释放这种新型多能源存储技术所提供的机会，以提高整个能源网的灵活性，从而实现可再生能源高度渗透的未来能源系统。

Thermo-chemical energy storage (TCES) has the potential to store very large amounts of energy within a small space and at low cost. This is achieved by converting thermal energy ('heat') to chemical energy via a reversible chemical reaction. For example, by heating a granular metallic oxide to the right temperature and at the right pressure, some of the oxygen is driven off (i.e., the substance is 'reduced') and heat is absorbed during the process. The resulting 'reduced oxide' is stable and can be stored for long periods without degradation. Heat can subsequently be recovered, when required, by passing air at elevated pressure over the reduced oxide. Some of the oxygen in the air is then absorbed but the remaining gas is heated by the reaction and (since it is also at high pressure) can be used to drive a gas turbine to generate electricity.Other gas-solid reactions are also possible, including 'calcination' of limestone (i.e., heating it up to drive off carbon dioxide) and hydration (with steam) of e.g. calcium oxide. Each reaction has its own set of peculiarities which can be exploited to its advantage. For example, the carbon dioxide emerging from the calcination reaction can be compressed and liquefied. This in itself absorbs electrical energy (in order to drive the compressors) and constitutes an additional, surprisingly compact and stable form of energy storage, from which electricity can be recovered by using the high-pressure CO2 to drive a turbo-generator. Compared with batteries, TCES has the potential to store energy at much lower cost per kilowatt-hour of storage capacity at grid scale, despite having a lower round trip efficiency. This is because TCES systems can be built based on unit operations and power plant technologies which scale up easily, compared to electrochemical systems. The efficiency for a thermo-chemical system is likely to be in the range 40 to 60%, however the 'conservation of energy', means that the remaining energy need not be wasted: it can be exploited for heating buildings, providing hot water or supplying heat for industrial processes. Furthermore, these systems offer the possibility to provide long duration storage without any safety hazards or pressurised storage facilities. How these technologies can contribute to various grid services, the scale needed and how best to locate them within the distribution network needs to be assessed. Many of the components have inertia, which will provide some frequency support, but the thermal response may limit service provision, particularly if waste heat is also being utilised. In this grant we will develop and test new materials to enable more efficient and cost effective TCES processes. Issues investigated include the cycle stability of the materials, their capacities and rates of conversion. Lab scale testing will demonstrate key aspects of the cycles and provide information needed for design and modelling work to evaluate these processes. We will conduct modelling on the process flowsheet, with detailed component models to allow losses to be identified and the process and material combinations to be optimised. To understand the value of these technologies to society, we will conduct system level dynamic modelling to understand their ability to provide grid services under various scenarios, including those in which there is the provision of thermal energy for district/industrial heating applications. We will analyse and quantify the grid-scale integration potentialities of TCES technology by adopting a whole-system approach, thus its integration with electricity/heating/cooling/gas networks. This will allow us to unlock the opportunities offered by this novel multi-energy storage technology to enhance the flexibility of the energy grid as a whole, and thus enable a future energy system with a high penetration of renewables