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，利用可再生能源发电变得越来越重要。到2050年，中国在总用电量中所占的份额将至少上升到80%。中国可再生能源发电量居世界首位，总发电量1870太瓦时，占全国总用电量的26.7%。由于可再生能源自然比化石燃料受到更大的波动，能源系统转型将导致对强大的分散式储能系统的更大需求。与其他技术相比，抽水蓄能电站是一种高效且技术成熟的储能形式。在发电过剩的时期，水被从下游水库抽到上游水库，在那里作为当地能源储存起来。当需要电力时，储存的水被排入下游水库，在那里势能被涡轮机和发电机转化为电能。抽水蓄能电站的发电量取决于压力库内的水量、可储水量以及上下游水库的垂直差。这就解释了为什么最合适的地点是在德国南部或中国的山区。在生产和消费地点附近实施抽水蓄能设施的另一种可能性是地下建筑，如现有矿山或专门为抽水蓄能设施设计的新挖掘。除了不受地形条件的影响外，其优点是减少了对地表空间的需求，这可能会使人们更容易接受。此外，在地下抽水蓄能电站（UPSP）中，原矿山的上下水库之间的垂直差预计会更大，从而产生比传统抽水蓄能电站更高的蓄能。设想项目的目的是研究利用废弃煤矿地下空间作为UPSP水库的可行性。这需要详细的水文地质、水文化学和岩石力学稳定性考虑以及对可用地下空间的分析。第二步，考虑额外的岩石支撑、电厂运行相关的动力和循环过程以及水动力过程，分析了周期性荷载作用下煤矿储层的长期稳定性。

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.