Pumped Thermal Electricity Storage

越来越多地使用可再生能源技术发电，其中许多具有不可预测的间歇性，将不可避免地导致对电网规模的电能存储计划的更大需求。英国政府的目标（作为欧盟可再生能源指令的一部分）是到2020年20%的能源来自可再生能源。这将需要更高比例的电力来自风力等不可控来源，而相关的挑战之一将是提供足够的电力储存能力，以应对由此产生的供应变化。目前，英国的电力存储容量约为30吉瓦时，最大输出功率约为3吉瓦。几乎所有这些都是抽水蓄能（PHS）的形式，这是昂贵的，其扩展范围受到地理限制。估计各不相同，但专家的观点是，为了有效地适应风能和其他可再生能源发电技术不断扩大的比例，我们的存储库存至少需要在未来十年左右翻一番。因此，开发新的、高效的、具有成本效益的电力存储方法有很强的动力。该项目旨在研究一种新的存储技术，称为泵送热电存储（PTES）。PTES使用高温比热泵将电能转换为热能，然后存储在两个大型储存器中-一个热一个冷。储层含有砾石或类似的高热容量材料，能够比PHS更紧凑地存储能量。当需要时，热能可以转换回电能有效地运行热泵作为热机向后。预计往返效率约为75%，略低于PHS，但PTES具有许多潜在优势，包括低资本成本和不受地理限制。与化学储能方法（电池和液流电池）相比，它还具有不需要任何危险或稀缺物质的优点。PTES的成功将取决于最小化各种热力学不可逆性的影响（例如，跨越巨大温差的热传递以及与工作流体压缩和膨胀相关的损失），同时保持较低的投资成本。因此，建议的工作重点是研究基本的热力学，流体流动和传热过程，使用实验，理论和计算方法相结合。这项工作的一个重要目标是开发和验证一个整体系统模型，并用它来优化设计和运营策略，并检查PTES可能给电力供应链带来的好处。

The increasing use of renewable energy technologies for electricity generation, many of which have an unpredictably intermittent nature, will inevitably lead to a greater need for grid-scale electrical energy storage schemes. The UK government's target (as part of the EU Renewable Energy Directive) is for 20% of energy to come from renewable sources by 2020. This will require a much a higher proportion of electricity to be generated from uncontrollable sources such as wind, and one of the associated challenges will be providing sufficient electricity storage capacity to deal with the resulting variability in supply. Currently there is about 30 GWh of electricity storage capacity in the UK, with a maximum power output of around 3 GW. Nearly all of this is in the form of Pumped Hydro Storage (PHS), which is expensive and its scope for extension is limited by geographical constraints. Estimates vary, but the expert view is that our storage inventory will need to at least double over the next decade or so in order to efficiently accommodate the expanding fraction of wind and other renewable generation technologies. There is thus strong motivation to develop new, efficient and cost-effective electricity storage methods. This project is aimed at investigating a novel storage technology known as Pumped Thermal Electricity Storage (PTES). PTES uses a high temperature-ratio heat pump to convert electrical energy into thermal energy which is then stored in two large reservoirs - one hot and one cold. The reservoirs contain gravel, or a similar high heat capacity material, and are able to store the energy much more compactly than PHS. When required, the thermal energy can be converted back into electrical energy by effectively running the heat pump backwards as a heat engine. The projected round-trip efficiency is approximately 75%, which is a little lower than PHS, but PTES has a number of potential benefits, including low capital cost and no geographical constraints. Compared to chemical energy storage methods (batteries and flow batteries) it also has the advantage of not requiring any hazardous or scarce substances. The success of PTES will hinge upon minimising the effect of various thermodynamic irreversibilities (for example, heat transfer across substantial temperature differences and losses associated with compression and expansion of the working fluid) whilst simultaneously keeping capital costs low. Accordingly, the proposed work focuses on investigating fundamental thermodynamic, fluid flow and heat transfer processes using a combination of experimental, theoretical and computational methods. An important aim of the work is also to develop and validate an overall system model and to use this to optimise the design and operation strategy, and to examine the benefits that PTES might bring to the electricity supply chain.