A brief discussion on the application of energy storage power stations in cement plants

Abstract: For cement plants, energy storage power stations have outstanding features such as reducing energy costs, stabilizing power supply, balancing power loads, and optimizing power utilization. They not only improve the stability and reliability of factory electricity consumption, but also serve the peak load and frequency regulation of the power grid. Therefore, this paper takes energy storage power stations as the starting point and takes a cement plant energy storage power station as an example to conduct an in-depth study of the project background, engineering plan, operation mode, investment model, benefits, and construction results of the energy storage power station, in order to provide reference and inspiration for this industry and similar industries.

Keywords: energy storage power station; cement factory; lithium iron phosphate battery; peak-valley arbitrage

0. Introduction

Under the influence of the energy conservation and emission reduction plans such as carbon peak and carbon neutrality, the contradiction between electricity supply and demand has become increasingly prominent, and the price difference between electricity peak and valley has continued to widen. Peak shaving and valley filling and optimizing electricity use have become the inevitable way for industrial enterprises to reduce electricity costs. More and more industrial enterprises have begun to turn their attention to energy storage systems. These enterprises generally have the characteristics of large energy demand, and they have special requirements for the quality of electricity, the cost of electricity, and the stability of power supply. As a traditional manufacturing enterprise, cement enterprises have a relatively complex factory power environment, which requires not only stable electricity quality but also low electricity costs. Especially when a sudden power outage occurs in the factory, it may cause varying degrees of damage to key equipment such as motors, fans, rotary kilns, and grinders, which not only affects the continuous production process, but also causes huge economic losses. It is based on the above situation that the application of energy storage power stations in cement plants not only solves many practical problems for enterprises, but also brings significant economic and social benefits.

1. Project Background

Hubei Province is one of the provinces in my country with abundant cement production capacity. In recent years, my country has entered a critical period with carbon reduction as the key strategic direction. From the local level, it has gradually shifted from the traditional total energy consumption and intensity regulation to the dual control of carbon emissions and intensity. This has promoted the transformation and upgrading of the energy structure and promoted the vigorous development of new energy technologies represented by energy storage, giving it broad market prospects and huge market potential. The cement plant where this project is located currently has a 2500t/d new dry process clinker cement production line, and a 110kV substation is built in conjunction with it. It uses a 110kV/10kV main transformer for power supply. Its main transformer capacity is 25MVA, and the rated load of the main transformer is about 14.5MW. The average load of the normal operation of the equipment in the factory is about 12MW.

The entire factory operates 24 hours a day, non-stop, with an annual production period of more than 310 days and an annual electricity consumption of nearly 9,000 kWh, which is a huge amount of energy consumption.

2. Project plan

2.1 Overall Plan

This project is based on the actual situation of the cement plant, the annual electricity consumption data of the plant and the total installed capacity of the existing power supply and distribution facilities. It uses the existing open space in the plant to build a 4MW/8MWh energy storage power station without affecting the normal operation of the plant. The power station uses the actual electricity price difference between peak and valley and peak and normal periods in the plant to arbitrage and generate benefits. By flexibly adjusting the charging and discharging strategy of the energy storage power station, the energy storage electricity can be used for peak production, reducing the demand electricity fee and comprehensive electricity cost. At the same time, it also serves as a backup power source for important loads in the factory, improving the reliability of the overall power consumption of the factory.

2.2 Energy storage design scheme

2.2.1 Battery Selection

Batteries are the basis for building large-scale energy storage systems, so the selection of batteries is of great significance in the construction of energy storage power stations. This project uses lithium iron phosphate batteries, which have been widely used in the field of new energy in recent years. Compared with other electrochemical batteries, this type of battery has outstanding advantages such as high energy density, long cycle life, large discharge depth, and large discharge current. At the same time, with the rapid development of the new energy industry, not only does it provide a good guarantee for the quality of such batteries, but the price of batteries is also gradually decreasing, with a high cost-effectiveness, which can well meet the economic requirements of the energy storage system. The parameters of the lithium iron phosphate battery used in this project are shown in Table 1.

Table 1 Parameters of lithium iron phosphate batteries used in the project

2.2.2 Battery System

The battery system of this project is composed of a basic battery box connected in series with a single lithium iron phosphate battery, and then several battery boxes are connected in series to form a battery cluster, and several battery clusters are connected in parallel to form the required battery system. In this system, the battery box is the basic component module and is in a core position. Its shell is made of insulating material, and there are openings on the top, bottom, left and right to meet the needs of ventilation and heat dissipation inside the module. By installing an elliptical handle on the battery box and adopting a structural design that is easy to disassemble and replace between the fixing device, the convenience of installing and replacing the battery box module is improved. At the same time, the battery box design also adopts a series of measures such as reserving expansion gaps, adopting support column structures, and reasonably setting safety gaps, which effectively avoids the risks of internal battery module bulging and creepage short circuits, and ensures the safe and stable operation of the battery system. The composition and technical parameters of the battery system of this project are shown in Table 2.

Table 2 Project battery system composition and technical parameters

2.2.3 Energy Storage Container

Energy storage containers have the characteristics of thermal insulation, waterproof and dustproof, corrosion resistance and shock resistance. Each energy storage container used in this project has a rated capacity of 3.2MWh and a rated power of 1.5MW. It is mainly composed of two independent parts: the battery compartment and the equipment compartment. The battery compartment is mainly used to place the battery system of the project, and the equipment compartment is mainly used to place the electrical equipment supporting the battery system. This layout facilitates the centralized management of the batteries and equipment of the energy storage power station. Each battery system of this project is placed in the battery compartment of a customized 6096mm×2438mm×2591mm air-cooled container, which is rack-mounted, compact in structure and reasonable in layout. In addition to the battery system, the battery compartment is also equipped with a battery management system, automatic fire extinguishing system, automatic air conditioning system, environmental monitoring system, fault alarm system, lighting system, and monitoring system, which provide strong support for the safety and stability of the battery compartment. The equipment compartment mainly includes energy storage converter (PCS), energy management system (EMS) and power distribution system. The plan layout of the energy storage container used in this project is shown in Figure 1.

According to the scale of the energy storage power station designed for this project, the maximum power of the energy storage power station is 4MW. Under high power, 8000kWh of electricity can be fully charged in 2 hours. When configuring the capacity of this project, the discharge efficiency and discharge depth of the battery system are fully considered. A total of 3 energy storage containers are required to be connected to their own energy storage converters on the DC side and then connected in parallel on the AC side to meet the requirements of the design. The topological structure of the energy storage power station is shown in Figure 2.