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”）转化为化学能来实现的。例如，通过将颗粒状金属氧化物加热到适当的温度和压力，一些氧气被排出（即物质被“还原”），在此过程中热量被吸收。由此产生的“还原氧化物”是稳定的，可以长时间储存而不会降解。随后，当需要时，通过在高压下通过还原氧化物的空气，可以回收热量。然后，空气中的一些氧气被吸收，但剩余的气体被反应加热（因为它也是在高压下），可以用来驱动燃气轮机发电。其他气固反应也是可能的，包括石灰石的“煅烧”（即加热以排出二氧化碳）和氧化钙的水化（与蒸汽）。每种反应都有自己的一套特点，可以利用这些特点来发挥其优势。例如，煅烧反应产生的二氧化碳可以被压缩和液化。这本身就能吸收电能（以驱动压缩机），并构成了一种额外的、令人惊讶的紧凑和稳定的能量储存形式，通过使用高压二氧化碳来驱动涡轮发电机，电力可以被回收。与电池相比，TCES在电网规模上以每千瓦时的存储容量成本低得多的方式存储能量，尽管其往返效率较低。这是因为与电化学系统相比，TCES系统可以基于单元操作和发电厂技术来构建，并且易于扩展。热化学系统的效率可能在40%到60%之间，然而“节约能源”意味着剩余的能源不需要浪费：它可以用于加热建筑物，提供热水或为工业过程提供热量。此外，这些系统提供了长时间储存的可能性，没有任何安全隐患或压力储存设施。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在配电网中最好地定位它们需要进行评估。许多组件都有惯性，这将提供一些频率支持，但热响应可能会限制服务的提供，特别是如果废热也被利用。在这笔拨款中，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工艺。研究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循环的关键方面，并为设计和建模工作提供评估这些过程所需的信息。我们将对工艺流程表进行建模，并提供详细的组件模型，以确定损失，并优化工艺和材料组合。为了了解这些技术对社会的价值，我们会进行系统层面的动态建模，以了解它们在不同情况下提供电网服务的能力，包括为区域供热/工业供热提供热能的情况。我们将通过采用全系统方法分析和量化TCES技术的电网规模集成潜力，从而将其与电力/供暖/制冷/燃气网络集成。这将使我们能够释放这种新型多能量存储技术提供的机会，以提高整个电网的灵活性，从而实现可再生能源高渗透率的未来能源系统

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