Three types of energy storage systems

Energy storage systems are often equated with batteries. Take, for example, portable batteries for mobile phones: energy is stored and then supplied to the phone later when needed.

While batteries are an important part of an energy storage system, it is not the only part. A complete energy storage system can be divided into three segments: battery energy storage system, power regulation system, and energy management and control system.

Battery energy storage system (BESS)

Commonly seen battery cell chemical types include lead-acid batteries, lithium iron phosphate (LFP) batteries, and ternary lithium batteries. These three battery types differ in energy density, life cycle, and material costs.

Lithium ternary batteries perform better in energy density and life cycle, while lead-acid batteries are more advantageous in terms of costs.

The packaging of battery cells can also be divided into three types: cylindrical, soft-packed, and square hardshell. Cylindrical batteries are the most mass-produced and are commonly used in computers, communications, and consumer electronics (3C) products. Soft-packed batteries are lightweight but must be reinforced with modules to be more rugged. Square hardshell batteries are the easiest to produce and more rugged but have higher costs.

In addition to cost, application, capacity requirements and construction space should also be taken into consideration when planning a BESS. If you choose a battery cell with a lower-rated capacity, you will need to deploy more cells to meet the overall capacity requirement, which will make the system more complicated and increase the risk of instability.

BESS can also be distinguished by its electrical discharge properties. They are commonly described by their charge-discharge rate (C-rate), which is the ratio of current at which a battery is charged and discharged.

Batteries are also divided into power type, balance type, and energy type based on their discharge characteristics.

Let's use a BESS with a capacity of 2,000kWh as an example. A power-type (2C) battery can support a power output of up to 4,000kWh and be discharged continuously for 30 minutes. A balance-type (1C) battery can at most discharge 2,000kWh for one hour. An energy-type battery can only support a maximum power output of 1,000kWh but can continuously discharge for two hours.

In addition to the discharge characteristics of these three battery types being different, the unit price and system price are also different. This is why the application environment must be considered when selecting different batteries in order to achieve the optimal cost-benefit.

For example, high-endurance energy batteries are often used in peak shaving and load transfer applications. Fast charging and fast discharging power batteries can be used for emergency backup power and frequency adjustment. Balance-type batteries can be used for electric vehicle (EV) charging stations and solar smoothing.

Regardless of the differences in battery cell chemistry, capacity or C-rate, safety is still the most important consideration for BESS.

From the battery cells, battery modules, to cabinets, every component must have safety protection mechanisms such as exposure protection, N-1 redundancy, and battery cell temperature monitoring. Only batteries that have passed the safety verification for energy storage systems should be used. Meeting all of these requirements is the only way to optimize cost-benefit and safety.

Power regulation system

Between the BESS and power grid, a power regulation system is required to act as a relay station for two-way power conversion. The power regulation system can perform AC/DC conversion to control power flowing in and out of the energy storage battery, and regulate real and virtual power to help strengthen grid stability and improve power quality.

Due to the diversity of battery systems, power regulation systems also focus on battery integration capabilities. The systems must be able to handle the requirements of different storage applications and have high energy conversion efficiency to avoid wasting electricity.

Furthermore, because energy storage systems are often constructed in remote suburbs and outdoor environments, the equipment must be highly reliable, have long-term adaptability to withstand harsh environments, have good security protection, and have remote management capabilities.

Energy management and control system

Within the complete architecture of the energy storage system, the energy management system acts as the administrator of the whole system.

The system controller or control panel connects to the energy storage system and power grid and has data communications capabilities. It can collect operational and energy information from the power equipment in the field, such as the renewable energy power generation system and energy storage system, and visualize the data to carry out remote monitoring and energy management and control in order to optimize energy management efficiency.

Energy management systems can be divided into different functions, such as real-time visualization of energy data, integration of renewable energy and storage systems to control charging and discharging of power and power dispatching; or through dynamic power allocation, it can fulfill the needs for peak shaving/load transfer, renewable energy spontaneous self-consumption, and backup power applications.

Predictive analysis can also be used on management and control systems to create reports on the generation and usage of electricity. It can be used to carry out renewable energy source generation predictions, power dispatch settings, and plan related schedules.

The biggest mid-to-long-term operational benefit for equipment management and maintenance services is that it can utilize big data analytics to execute predictive maintenance. Doing so allows managers to arrange maintenance in advance based on predicted equipment anomalies and lifespan.