Underground Power Station Research Articles

Regional development potential of underground pumped storage power station using abandoned coal mines: A case study of the Yellow River Basin, China

China is gradually transforming its coal-based energy supply structure towards sustainable development, resulting in a growing number of abandoned coal mines. Underground pumped storage power stations (UPSPS) using abandoned coal mines efficiently utilize the coal mine space and promote renewable energy applications. This paper introduces a novel framework to evaluate the UPSPS regional development potential in the Yellow River Basin (YRB) from the perspective of sustainable development. A fuzzy normal cloud model based on the combined weight (FNCM-CW) is proposed to calculate the advantages and the four-quadrant method incorporating bubble diagrams is employed to merge the advantage grades. The results indicate that the construction investment, reservoir volume, transport conditions and policy support are the most important indexes affecting the regional development of UPSPS. Shanxi and Inner Mongolia have accumulated a large number of abandoned coal mine resources with shallow mining depths and high productivity. The distribution of economic, technological, environmental and social advantages in the YRB is uneven, where the upstream areas have abundant wind and solar energy resources, the midstream possesses urgent energy transformation demand and the downstream features a stronger economic foundation. The ranking result of the UPSPS regional development potential is: Shanxi > Inner Mongolia > Shandong > Henan > Ningxia > Sichuan > Shaanxi > Qinghai > Gansu. This paper provides decision support for UPSPS engineering practice and is a reference for other countries and coal-producing areas.

Field tests and analyses of thermal and humidity environment and heating and cooling capacity of air intake tunnels into underground plants

The underground air intake tunnel is a natural source of heat and cold that can be utilised to significantly condition the air entering the underground plant, thereby reducing the energy consumption of the plant. The heat and humidity environments of three underground tunnels were tested in winter and summer. The tunnels belong to Jiangxi Hongping Hydropower Station, which has significant cooling and heating characteristics in the air intake tunnel, Sichuan Xiluodu Hydropower Station, the world’s largest underground power station, and Hainan Qiongzhong Hydropower Station, the southernmost in China. The heat and humidity exchange pattern between the underground air intake tunnel of the power station and the air was analysed, including temperature and humidity trends, condensation zoning, inter-seasonal thermoregulation effect. Furthermore, the cooling and heating capacity of the air intake tunnel was calculated and analysed. The results show that: the greater the length and cross-sectional area of the tunnel, the greater the cooling and heating quantity; there is a noticeable difference in heat transfer capacity between different air intake tunnels, and the tunnel length is not a decisive factor for the heat transfer capacity, the heat transfer capacity (enthalpy difference) per unit mass flow rate of air in the air intake tunnels of Jiangxi (1500 m) is more than twice that of Sichuan (2800 m); the test cooling capacity of the Hainan (1400 m) tunnel reaches 606 kW (while the plant chiller rated cooling capacity of 2082 kW), the air intake tunnel can be used as an underground plant energy-efficient air conditioning, the equipment selection of plant mechanical air conditioning should take into account the air handling capacity of the air intake tunnel.

A two-stage framework for site selection of underground pumped storage power stations using abandoned coal mines based on multi-criteria decision-making method: An empirical study in China

With the continued transformation of the energy structure, more and more coal mines have been abandoned. The construction of underground pumped storage power stations using abandoned coal mines not only solves the problem of renovating abandoned coal mines, but also ensures a high level of photovoltaic and wind integration. However, the most basic site selection problem of underground pumped storage power plants using waste coal mines has rarely been studied due to the complexity of the technical scheme and the uncertainty of the decision environment. Therefore, a two-stage fuzzy evaluation model is proposed in this paper. Firstly, two sets of site selection index systems are established, namely the veto assessment system and the comprehensive evaluation criteria system. Triangular intuitionistic fuzzy numbers are used for information representation. Then, the veto assessment system is applied for the initial screening of the alternatives. Afterward, the alternatives are evaluated by the comprehensive evaluation criteria system. The entropy method and step-wise weight assessment ratio analysis are utilized to calculate the objective and subjective weights respectively, and the Lagrange optimization method is used to obtain the combined weights. The sorting results of the alternatives are obtained through multi-attributive border approximation area comparison. Finally, an empirical analysis based on eight abandoned coal mines in Datong, Shanxi Province, proves the rationality of the decision-making framework. The weights of natural condition, society, resources, and economy are 29.52%, 23.83%, 28.42% and 18.23% respectively. Natural condition is the most important factor to consider when choosing the site for underground pumped storage power stations. The ranking results of the alternatives is A5 > A2 > A3 > A8 > A7. Therefore, A5 is the optimal location. The results have a guiding role for both governments and investors in the construction of underground pumped storage power stations and transformation of abandoned coal mines.

A novel design of dehumidifier system in underground pumped storage power station

The heavy water condensation problem has led to safety concern for the workers and electrical facilities in the underground pumped storage power station. As for current dehumidification scheme, heat and humidity load are all removed through the air conditioning unit, which has high energy consumption and low efficiency. As a large amount of moisture comes from the external fresh air, in this study, we set the dehumidification system in the underground ventilation tunnel. By using the air inlet channel to lighten the wet load, the heat and humidity parameters of the fresh air are processed as far as possible in the front of the air supply, so as to achieve the purpose of energy saving operation. In this study, numerical modelling was used to simulate the control scheme of the heat and humidity environment. Compared with the traditional method, the two new dehumidification schemes can take about 1/3 of the wet load of the main workshop, and the dehumidification efficiency is improved. Therefore, this study is expected to be a promising tool for reducing air humidity in underground workshops.

Optimization of Ventilation System for a Main Power Plant in an Underground Pumped Storage Power Station

Pumped storage power station is an economic and reliable means of peak load regulation for power networks. The temperature and humidity control are complicated due to the huge amount of heat and moisture emission in the main power plant. This paper investigates the operating condition of three different ventilation cases in a five-storey underground pumped storage power station. A full-scale model of the main plant was built for numerical simulation. Three ventilation cases were studied by changing the number, area and layout of air supply vents at the top of the main plant. The airflow distribution of three cases in summer condition were calculated and an optimal ventilation case was determined by comparing the jet flow range and temperature in the working zone. The working condition in winter was also simulated and verified in order to ensure the reliability of the ventilation case. Results show that case 1 was determined as a reasonable air supply case. In this paper, a reasonable scheme of ventilation system was proposed in a underground pumped storage power station. The results would be helpful to optimize the air ventilation mode in underground powerhouse of pumped storage power station.

Study on ventilation effect for a large space in an underground hydropower station

Due to the urgent need for reducing carbon emissions, an increasing number of pumped storage power stations have been constructed and used considering its obvious advantages of energy saving. However, relevant design guidance and technical research failed to meet the development demand. There is only a small number of studies focusing on the prediction and evaluation of ventilation system in singlestory stations, however, little on the integral connected plant floors. Thus, it is significant to study safety operation technology of deep underground pumped storage power stations, especially in terms of thermal and humidity environment. A reduced-scale (1/30) model based on an engineering project was set up, and numerical simulations were carried out to study the temperature and velocity distribution in the large underground space under the summer design condition (L=21.1×104m3/s, T=19°C, Q=997KW). Results show that the temperature on the right side of the powerhouse is slightly higher than that on the left side, and the gap is approximately from 1°C to 4°C. Moreover, local overheating may occur in some places. The side air supply velocity and location should be paid more attention to in designing air distribution.

Research on the Prediction of Energy-saving Potential of Traffic Tunnel Based on BP Neural Network

Accurate grasp of underground building environmental temperature and humidity and cooling and heating loads is the basis for energy-saving analysis, ventilation and air conditioning system design and operation control. In order to come up with a method that can quickly and accurately predict the environmental temperature and humidity and energy-saving potential of underground power station traffic tunnel, this paper takes Xiangyou pumped storage power station traffic tunnel as the research object and designs a BP neural network model for traffic tunnel temperature and relative humidity prediction with respect to the main environmental influencing factors. Comparing with the test data, it is verified that the model has high prediction accuracy. At the same time, the prediction model was used to calculate the energy saving potential of traffic tunnel ventilation. The results showed that the relative error of predicting the energy saving potential of traffic tunnel in summer was less than 2% and in winter was less than 0.3%. This prediction method can obtain the traffic tunnel air temperature and humidity and ventilation energy saving potential simply and accurately, so that the design can be developed in the direction favorable to the energy saving of underground buildings.

Analysis of Influencing Factors of Modification Potential of Abandoned Coal Mine Into Pumped Storage Power Station

Abstract By modifying underground spaces of abandoned coal mines into underground pumped storage power stations, it can realize the efficient and reasonable utilization of underground space and, at the same time, meet the increasing demand for energy storage facilities of the grid, bringing social, economic, and environmental benefits. Previous research in this area has been limited to the stage of conceptual discussion, and there is no scientific evaluation method for the modification and utilization potential of abandoned coal mine spaces. Establishing a scientific evaluation indicator system forms the basis for evaluating the underground space development and utilization capacity of abandoned mines. Based on the principle of pumped energy storage and the characteristics of coal mine roadway conditions, this paper utilized an analytical hierarchy process (AHP) to evaluate the main influencing factors, including elevation difference between the upper and lower reservoirs, reservoir capacity, roadway surrounding rock stability, and roadway permeability. It analyzed the modification potential of underground spaces and then verified the development potential of the underground spaces of abandoned mines by a statistic model. The study found that the elevation difference between the upper and lower reservoirs is the most influential indicator; second, the capacity of the upper and lower reservoirs is also an important evaluation indicator. The research methods and conclusions will provide useful tools and decision-making basis for analyzing the feasibility and techno-economic benefit of modifying the underground spaces of abandoned coal mines into pumped storage power stations.

Stability analysis of three-dimensional rock blocks based on general block method

The stability of rock blocks is still a key problem in the rock excavation industry and therefore deserve further research and study. Due to the complicated nature of large-scale, three-dimensional developments in blocky rock masses, it is critical to conduct investigations into the stability of rock blocks and choose a reasonable excavation and rock-supporting scheme for design and construction purposes. This article introduces the basic analysis procedure of the General Block (GB) method and discuss the stability of rock blocks in an underground hydropower station at the Three Gorges Project. The application of the GB method mainly follows four basic steps: the discretization of the domain; removal of incomplete fractures; block identification and finally, the block stability analysis. Block identification is the most important of the four processes. A 3-D block model is set up and analyzed. The results from the analysis is used to evaluate the stability of the surrounding rock mass in the powerhouse during the process of excavation. The findings provide guidance on the excavation process and the support requirements for the underground power station. It is envisaged that model study will serve as a reference for the stability evaluation of rock blocks in some related fields.

A Construction Schedule Robustness Measure Based on Improved Prospect Theory and the Copula-CRITIC Method

A robustness measure is an effective tool to evaluate the anti-interference capacity of the construction schedule. However, most research focuses on solution robustness or quality robustness, and few consider a composite robustness criterion, neglecting the bounded rationality of subjective weights and inherent importance and nonlinear intercriteria correlations of objective weights. Therefore, a construction schedule robustness measure based on improved prospect theory and the Copula-criteria importance through intercriteria correlation (CRITIC) method is proposed. Firstly, a composite robustness criterion is established, including start time deviation rs and structural deviation rp for measuring solution robustness from project execution and completion probability rc for measuring quality robustness from the project result. Secondly, bounded rationality is considered, using prospect theory to calculate subjective weights, which is improved by the interval distance formula. Thirdly, the Copula-CRITIC method is proposed to determine objective weights incorporating both inherent importance and nonlinear intercriteria correlations. Finally, an information-entropy-based evidence reasoning method is applied to combine subjective and objective weights together while identifying their validity. An underground power station in China is used for a case study, whose robustness is measured using the proposed methods, single robustness criterion, and composite robustness criterion using traditional weighting methods. The comparison results verify the consistency, representativeness, and advantage of the proposed criterion and methods.

Optimization of Construction Duration and Schedule Robustness Based on Hybrid Grey Wolf Optimizer with Sine Cosine Algorithm

Construction duration and schedule robustness are of great importance to ensure efficient construction. However, the current literature has neglected the importance of schedule robustness. Relatively little attention has been paid to schedule robustness via deviation of an activity’s starting time, which does not consider schedule robustness via structural deviation caused by the logical relationships among activities. This leads to a possibility of deviation between the planned schedule and the actual situation. Thus, an optimization model of construction duration and schedule robustness is proposed to solve this problem. Firstly, duration and two robustness criteria including starting time deviation and structural deviation were selected as the optimization objectives. Secondly, critical chain method and starting time criticality (STC) method were adopted to allocate buffers to the schedule in order to generate alternative schedules for optimization. Thirdly, hybrid grey wolf optimizer with sine cosine algorithm (HGWOSCA) was proposed to solve the optimization model. The movement directions and speed of grey wolf optimizer (GWO) was improved by sine cosine algorithm (SCA) so that the algorithm’s performance of convergence, diversity, accuracy, and distribution improved. Finally, an underground power station in China was used for a case study, by which the applicability and advantages of the proposed model were proved.

Dynamic Monitoring and Stability Analysis of Rock-bolted Crane Girder In large Cavern With Layered Surrounding Rock

The large and medium-sized hydropower projects underground cavern group are basically in relatively integrate surrounding rock, so there are few engineering examples in layered surrounding rock with type III surrounding rocks as the main rock, and lack of successful experience. According to rock-bolted crane girder under the layered surrounding rock of a large underground power station, analyzing prototype dynamic monitoring data of the excavation, unloading and load-bearing test .The distribution of the monitoring data conforms to the normal law, and there are no large outliers, under the action of a large number of bolts, rock-bolted crane girder basically forms a good integrity with the layered surrounding rock, and the load-bearing test has no effect on the stress condition and stability condition of surrounding rock.

Secondary utilizations and perspectives of mined underground space

The mined underground space is formed by the exploitation of resources and minerals. On the basis of review analysis of experiences of utilization of mined underground space over the world, suitable conditions of surrounding rocks for mined underground space are clarified to various functions of development and utilization of mined underground space. A method is proposed for identifying and estimating the scale of mined underground space, and this is used to obtain an estimate of the volume of available underground space in mines in China and to construct distribution maps of mined underground space available in the country. In order to improve comprehensive utilization of mined underground space, combined with current foundation of underground space utilization and future strategic demands, nine types of functional utilization are proposed systematically, including underground pumped-storage power stations, deep underground medicine and rehabilitation, the storage of strategic energy and resource reserves, underground data centers, domestic and industrial waste disposal, intelligent vertical parking systems, cutting-edge scientific facilities, underground agriculture, and underground ecological cities.

Deformation and Reinforcement Monitoring Analysis of Tail Water Outlet Slope in a Hydropower Station

The slope stability situation surrounding the dam site area is very important to each correlative department during constructing hydroelectric power station. So it is important to enforce the high slope rock deformation monitoring, and to process and analyze the measuring data timely. Surface displacement of different height of slope were tracked and monitored based on the field investigation of a hydroelectric power station in Jinsha river. Deformation and the static stability of high slope were analyzed by utilizing rock deformation monitoring data. Taking the left-bank tailrace outlet slope of underground power station for example, we analyzed the slope stability by numerical simulation to obtain the characteristics of deformation and failure of slope. The time and space deformation distribution regularity of rock mass were summarized, the deformation, stress and failure of the studied slope were simulated. The results intuitively show the displacement distribution characteristics and slope plastic failure.

A network model for natural ventilation simulation in deep buried underground structures

The study of underground natural ventilation opportunities has become increasingly significant in recent years with its promise of wide application in underground structures such as underground hydro power stations, metro stations, underground parking and laboratories. It is recognized that deployment of natural ventilation constitutes a passive technology that can lead to significant energy conservation if applied judiciously. This paper focuses on underground buildings that are buried deeply and typically consist of an underground complex network of connected structures. The other characteristic is that these structures house machinery and devices that generate heat, leading to elevated internal air temperatures. Combined with the deep location, it implies that buoyancy forces are significant which make natural ventilation through vertical shaft openings a viable option. These characteristics demand a study of the heat transfer processes between ambient conditions, soil and underground buildings. In this paper, we present a dynamic flow network model with loops for multizone airflow and apply it to deep buried underground structures considering the dominant heat transfer characteristics, not only through the elements of the network but also the heat exchange with the envelope and adjacent soil mass. Finally, a small-scale experiment of occurring airflow is conducted and compared with the outcomes of the dynamic simulation of the proposed model. The comparison serves as validation and illustration of the application potential of the network model for natural ventilation investigation and consecutive optimization of its use in underground buildings.

Fracture development around deep underground excavations: Insights from FDEM modelling

Over the past twenty years, there has been a growing interest in the development of numerical models that can realistically capture the progressive failure of rock masses. In particular, the investigation of damage development around underground excavations represents a key issue in several rock engineering applications, including tunnelling, mining, drilling, hydroelectric power generation, and the deep geological disposal of nuclear waste. The goal of this paper is to show the effectiveness of a hybrid finite-discrete element method (FDEM) code to simulate the fracturing mechanisms associated with the excavation of underground openings in brittle rock formations. A brief review of the current state-of-the-art modelling approaches is initially provided, including the description of selecting continuum- and discontinuum-based techniques. Then, the influence of a number of factors, including mechanical and in situ stress anisotropy, as well as excavation geometry, on the simulated damage is analysed for three different geomechanical scenarios. Firstly, the fracture nucleation and growth process under isotropic rock mass conditions is simulated for a circular shaft. Secondly, the influence of mechanical anisotropy on the development of an excavation damaged zone (EDZ) around a tunnel excavated in a layered rock formation is considered. Finally, the interaction mechanisms between two large caverns of an underground hydroelectric power station are investigated, with particular emphasis on the rock mass response sensitivity to the pillar width and excavation sequence. Overall, the numerical results indicate that FDEM simulations can provide unique geomechanical insights in cases where an explicit consideration of fracture and fragmentation processes is of paramount importance.

Underground rockfall stability analysis using the numerical manifold method

The present study applies the numerical manifold method (NMM) as a tool to investigate the rockfall hazard in underground engineering. The crack evolution technique with crack initiation and propagation criterion, which has been successfully applied to handle cracking problems in rocks, is used in this study. A rockbolt element is introduced, which is first validated by a simple case. The mechanism of the rockbolt in reinforcing a layered rock mass is then investigated through a four-layered rock beam example. The developed NMM is then used to investigate the rockfall instability caused by either natural joints or mining induced fractures in an underground power station house or a tunnel. The results illustrate that the developed NMM can not only capture the entire dynamic process of the rockfall but also locate the keyblock successfully. As such, corresponding reinforcement methods can be chosen reasonably.

Effect of Explosion and Fire on Underground Structures

It appears that explosion in a closed space of underground works together with extreme increase of temperature influences the bearing capacity of underground structures, particularly road and rail tunnels, underground power stations, underground parkings, etc. The explosion is caused by various resources (terrorist attack, explosion of inflammable material positioned on freight cars, and such). This paper is focused on the effect of a fast change of load in tunnels and especially on the tunnel linings from fiber reinforced concrete. Shock wave caused by both the explosion and increased temperature leads to a spalling of concrete, i.e. to a reduction of thickness of the bearing structure and decrease of feasibility of the support. Relatively complicated system, describing an interaction between the air (shock wave described by gas dynamics), and the solid part (tunnel lining and the rock surrounding the tunnel obeying the equations of elasto-plasticity) is to be simplified in this paper. First, laminated cylinder describing the solid structure of the tunnel and the non-linear Winkler subsoil simulates the rock. The cylinder is loaded by the influence of explosion and change of temperature. It is to be shown that the superheated vapor together with interacting waves of the open charge inside of the underground space may cause an extensive occurrence of fissures on the surface exposed to the external loading envisaged. On the other hand the rock surrounding the underground structure interacts with the underground structure as a dumper. The simplified model starts with axisymmetric geometry and axisymmetric load by the shock wave and change of temperature, and moreover, generalized plain strain assumption is considered with a constant change of pressure in the axial direction of the tunnel. The governing equations adopt this assumption and the solution is then easier. The generalization to more complicated non-symmetric problems is straightforward. Couple of examples is to verify the theoretical considerations.

Structural Design of Giant Generator Excitation Rectifier Cabinet

A structural design scheme was proposed based on the requirements for giant generator excitation rectifier cabinet. It is described in detail from type selection, heat dissipation, to insulation and modular design. The operation in the Three Gorges Underground Power Station proved the success of the structural design.

Stability Analysis about the Impact of Soft Rock to the Underground Cavern Group

Soft rock is frequently encountered in underground excavation process. It is difficult to excavate and support in soft rock mass which has low strength, large deformation and needs much time to be out of shape but little time to be self-stabilized. Based on a large underground power station, finite element model analysis was carried out to simulate the excavation process and the results of displacement, stress and plasticity area were compared between supported and unsupported conditions to evaluate the stability of the rock mass.