Cyclical Processes in Underground Pumped Storage Power Plants

作为能源转型的一部分，德国政府为自己设定了确保可靠、生态和经济上可持续的能源供应的目标。因此，可再生能源发电正变得越来越重要。到2050年，它在总用电量中的份额将至少上升到80%。中国以1,870太瓦时的总发电量成为世界第一可再生能源生产国，占全国总用电量的26.7%。由于可再生能源比化石燃料自然受到更大的波动，能源系统的转变将导致对强大的、分散的能量存储系统的更大需求。与其他技术相比，抽水蓄能电站是一种高效、技术成熟的储能形式。在发电过剩的时期，水从下游水库被抽出到上游水库，在那里作为当地能源储存。当需要电力时，储存的水被排入下游的水库，在那里，涡轮机和发电机将势能转化为电能。抽水蓄能电站的发电量取决于压力钢管的排水量、可蓄水量以及水库上下游的垂直差。这就解释了为什么最合适的地点是在德国南部的山区或中国。在生产和消费场所附近实施抽水蓄能设施的另一种可能性是地下建筑，例如现有的矿山或专门为抽水蓄能设施设计的新挖掘机。除了独立于地形条件外，其好处是减少了对地面空间的需求，这可能伴随着更大的人口接受度。此外，地下抽水蓄能电站(UPSP)的上、下水库之间的垂直差预计会更大，从而产生与常规抽水蓄能水库相当高的储能。设想的项目的目标是研究利用废弃的煤矿地下空间作为联合包裹处理厂水库的可行性。这需要详细的水文地质、水化学和岩石力学稳定性考虑，以及对可用的地下空间的分析。在第二步中，考虑了额外的岩石支撑、与工厂运行和水动力过程相关的动态和循环过程，分析了周期性载荷下煤矿水库的长期稳定性。

As part of the energy transition, the German government has set itself the goal of ensuring a reliable, ecologically and economically sustainable energy supply. For this reason, energy generation from renewable energy sources is becoming increasingly important. Its share of gross electricity consumption is to rise to at least 80% by 2050. China became number one worldwide in the production of renewable energies with a total of 1,870 TWh representing 26.7% of the country’s total power consumption. As renewable energies are naturally subject to greater fluctuations than fossil fuels, the energy system transformation will result in a greater need for powerful, decentralized energy storage systems. Compared to other technologies, pumped storage power plants represent an efficient and technically mature form of energy storage. In periods of excess electricity generation, water is pumped from a downstream reservoir to an upstream reservoir where it is stored as local energy. When electricity is needed, the stored water is drained into the downstream reservoir, where the potential energy is converted into electrical energy by turbines and generators. The quantity of electricity generation of pumped storage power plants depends on the discharge of water in the penstock, the volume of water that can be stored and the vertical difference between the up- and downstream reservoir. This explains why the most suitable locations are found in the mountainous regions of southern Germany or China. One alternative possibility for implementing pumped storage facilities close to production and consumption sites are underground constructions such as existing mines or new excavations specifically designed for a pumped storage facility. In addition to the independence from topographical conditions, the advantage is a reduced surficial space requirement, which could be accompanied by greater acceptance among the population. In addition, the vertical difference between the upper and the lower reservoir in former mines is expected to be higher in underground pumped storage power plants (UPSP) resulting in comparable higher energy storage than conventional pumped storage reser-voirs. The objective of the envisaged project is to study the feasibility for utilizing abandoned underground space of coalmines as reservoir for UPSP. This requires detailed hydrogeological, hydro-chemical and rock mechanical stability considerations as well as the analysis of the available underground space. In a second step, the long-term stability of reservoirs in coalmines under cyclical loads is analyzed considering additional rock support, dynamic and cyclical processes associated with plant operations and hydrodynamic processes.