The centralized and string based energy storage technology routes occupy important positions in the current energy storage field, each with unique advantages and disadvantages and suitable for different application scenarios.
Centralized energy storage technology route
Features and advantages
Simple control logic: The battery packs of the centralized energy storage system are directly connected in series, and then multiple packs are connected in parallel to a large inverter (PCS) on the DC side, making management and maintenance easier.
Low system cost: Due to its relatively simple structure, the initial investment and maintenance costs are low, especially in large-scale procurement to further reduce costs.
Easy to achieve large-scale scheduling: It can effectively balance the supply and demand of the power grid, improve the quality and stability of electricity, and is suitable for grid side energy storage and supporting large-scale renewable energy power stations.
Significant economic benefits: Through centralized management, equipment and operation costs have been reduced, demonstrating significant economic advantages.
Shortcoming
Barrel effect: The overall lifespan of a system depends on the weakest link, where the worst performing battery module affects the efficiency of the entire system.
Inter cluster circulation problem: Different battery clusters have inconsistent discharge depths, leading to circulation phenomena and affecting charging and discharging efficiency.
Security challenge: The formation of circulating currents between parallel battery clusters increases the risk of overcharging of battery cells, posing a threat to safety.
High complexity of operation and maintenance: When the system encounters problems, manufacturers usually need to dispatch technical personnel to the site for debugging and maintenance, which can prolong downtime and increase operation and maintenance costs.
Application examples
Taking the Huaneng Huangtai 100MW/200MWh project as an example, this is the first large-scale energy storage power station in China to adopt a centralized PCS architecture, demonstrating the potential of centralized solutions in grid energy storage and large-scale renewable energy support.
Route of string type energy storage technology
Features and advantages
Strong flexibility: Composed of multiple smaller capacity energy storage units, each unit has independent control and management functions, and can be flexibly configured according to different energy generation and consumption patterns.
Improved system efficiency: achieved single cluster one management, improved the balance and charging and discharging efficiency of battery packs.
High reliability and easy maintenance: In the event of a malfunction, it can accurately locate a single cluster without affecting the operation of other cabinets, reducing the overall shutdown risk of the system.
Higher safety: Avoiding the influence of circulating currents, achieving fault isolation, and adopting an efficient thermal management system to ensure good temperature uniformity and long battery life.
Shortcoming
The integration method is relatively complex: compared to centralized, string based integration and debugging are more complex because each energy storage unit needs to be finely configured to ensure system stability.
System cost increase: Due to the use of more optimizers and monitoring devices, the overall cost is higher.
Application examples and parameters
The 3MW/6MWh solar energy storage project in Linyang, Dezhou, Shandong is a typical case of using a string energy storage solution. This project not only improves the adaptability and economy of the system, but also proves its value in distributed energy systems.
Application performance of two technological routes on the grid side, user side, and other specific scenarios
Grid side energy storage
Centralized energy storage
Large scale application and cost-effectiveness: Centralized energy storage technology dominates in grid side energy storage due to its large single device capacity, compact structure, and ease of achieving large-scale energy allocation.
For example, it can effectively balance the supply and demand relationship of the power grid, improve the quality and stability of electricity, especially in the field of supporting energy storage in large renewable energy power plants.
Case study: The Huaneng Huangtai 100MW/200MWh project is a typical example, which utilizes a centralized PCS architecture to support grid level energy storage needs.
String type energy storage
Flexibility and reliability: Although centralized energy storage is more common in the field of large-scale storage, with the development of technology, string type energy storage is gradually penetrating into this field. Its modular design allows for more flexible handling of complex terrains and dispersed energy layouts, while reducing overall system downtime caused by wind.
Emerging trend: Some new string connected grid type energy storage systems have successfully passed technical appraisal and are suitable for various application scenarios such as strong power grids, weak power grids, and off grid, indicating that this technology is moving towards larger scale applications.
User side energy storage
Centralized energy storage
Limited applicability: For the user side, centralized energy storage has relatively few applicable scenarios due to the large volume of a single device, high transportation difficulty, and strict installation site requirements. In addition, expansion or power replenishment must be carried out on a cabin by cabin basis, which is less flexible.
Economic considerations: Although the initial investment cost is relatively low, it is not cost-effective for small users because once a failure occurs, the entire system needs to be shut down for inspection, which increases operation and maintenance time and costs.
String type energy storage
Widely adopted: In contrast, string type energy storage has been widely used in household and commercial fields. It has a small single cabinet volume, making it easy to transport and install, and can easily adjust the system's power and capacity according to actual needs.
The advantages are obvious: this technology not only supports the mixing of old and new batteries, but also can be flexibly expanded according to actual situations, making it very suitable for distributed applications such as home rooftop photovoltaics, small energy storage power stations, etc.
Specific application scenarios
The advantages of string based energy storage in distributed energy systems: In distributed energy systems such as zero carbon parks and new energy distribution and storage, string based energy storage can be accurately configured according to different energy generation and consumption patterns, improving the efficiency and reliability of the system. It achieves refined management of individual energy storage units, thereby better matching changes in local power demand.
Safety and stability: Each battery cluster is individually controlled for charging and discharging, avoiding the influence of circulating currents, achieving fault isolation, and ensuring the long-term stable operation of the system.
Complex terrain and dispersed layout
Strong adaptability: Whether in mountainous areas or urban fringe areas, string type energy storage can adapt well to complex and changing geographical environments. Even in the event of a failure in some energy storage units, the remaining units can continue to operate, reducing the overall risk of system shutdown.
