Sigenergy Highlights Modular DC-Coupled Storage

Energy storage is moving beyond standalone systems, and with rising renewable penetration, it is becoming central to how power systems operate. In this transition, the system architecture is becoming as important as battery capacity, particularly as grids become more dynamic and distributed.

At the TaiyangNews Inverters & Battery Storage Conference, Sebastian Fege, Senior Account Manager at Sigenergy, presented the company’s SigenStack platform, calling it a shift away from conventional storage design. In his presentation, titled Sigenstack – Innovative Modular C&I Battery Empowering Utility Projects, he noted that while the market has evolved rapidly, system architecture in C&I and utility-scale applications still follows older design principles.

The market backdrop supports this shift. Increasing PV penetration is leading to more frequent oversupply and negative electricity prices, particularly in Europe. At the same time, grid instability and outage risks are rising. Fege pointed out that storage is no longer limited to a single function, but supports multiple use cases, including self-consumption, peak shaving, arbitrage, and virtual power plant (VPP) participation, with these applications increasingly combined within a single system to maximize revenue.

He contrasted this with the current system design. While residential systems have largely transitioned to DC-coupled hybrid architectures, C&I and utility-scale installations still rely on containerized, AC-coupled solutions. These systems depend on multiple components and conversion stages, increasing complexity, cost, and failure exposure. Fege described this as an ‘old-school’ approach compared to more integrated system designs.

SigenStack adopts a DC-coupled hybrid architecture that integrates PV and storage via a single inverter. This reduces component count and streamlines system design. According to Fege, the elimination of separate PV inverters, PCS, and combiner units contributes to both lower complexity and reduced system costs, with savings of around €12,000 in a 400 kW AC / 1,000 kWh configuration.

The architecture also improves the utilization of PV capacity by managing energy flows on the DC side. Fege noted that the system supports DC/AC ratios of up to 2.0, compared to around 1.3 in conventional systems, allowing higher PV capacity to be connected without increasing grid output. This enables up to 200% DC input without the losses typically associated with AC-coupled systems.

Rather than relying on centralized blocks, SigenStack is built around smaller, modular units. Each inverter can be paired with up to 21 battery modules of 12 kWh, reaching 252 kWh per unit. Multiple inverters can then be combined to scale the system to utility-level capacities, while maintaining flexibility in system design.

This modular architecture also simplifies deployment. According to Fege, the system uses pre-configured, plug-and-play components, with cabling delivered and integrated by the manufacturer. Modules are stacked without complex wiring, and installation avoids heavy lifting requirements such as large cranes. As a result, a 20 MWh system can be deployed in around 10 days, compared to approximately 60 days for conventional container-based systems.

Safety is implemented at the module level, with each 12 kWh unit operating as an independent block. This enables localized monitoring and protection, reducing system-wide risk. Fege highlighted that the system uses high sensor density, with 8 sensors monitoring 12 cells, supported by AI-based temperature control and integrated smoke detection. Pressure relief is triggered at around 5 kPa, compared to approximately 10 kPa in conventional systems, enabling earlier response.

Thermal protection is layered across the system to prevent propagation. Insulation materials within and around each module can withstand temperatures up to 650°C, with insulation resistance reaching 800,000 MΩ. Fire protection is implemented at both pack and rack levels, improving containment compared to conventional designs.

This design was validated through an extreme test scenario. Fege noted that a module was intentionally triggered into thermal runaway and allowed to burn for 30 minutes under controlled conditions, with all safety systems disabled. No fire spread occurred between modules or across stacks. Even with one module affected, the rest of the system continued operating normally, demonstrating strong isolation and reliability.

Durability is addressed through enclosure design and reduced maintenance requirements. With IP66 protection, the system prevents dust, moisture, and water ingress. Fege emphasized that this enables a maintenance-free system, in contrast to conventional container systems that require periodic inspection and servicing, often resulting in annual maintenance costs of around €22,610 for a 1 MWh installation.

The system also integrates high-speed communication and control. According to Fege, it achieves speeds of up to 100 Mbps, compared to ~9,600 bps in conventional RS485 systems, while response times are reduced from around 2 seconds to about 100 ms. This improves system responsiveness and enables applications such as real-time grid interaction and VPP participation.

These design choices translate directly into deployment flexibility. In Belgium, a 1 MWh system was installed within a steel factory using unused space. In Bulgaria, a 20 MWh system was deployed at a site with limited access, where container-based systems could not be transported. In Germany, a 59 MWp PV project is being retrofitted with storage under grid constraints, using DC coupling to integrate more than 90 MWh of battery capacity.

The modular approach also enables new installation strategies. Storage systems can be placed beneath PV arrays, reducing land requirements and avoiding additional site development. Fege highlighted that existing AC infrastructure, including transformers and cabling, can be reused, effectively allowing storage integration with minimal additional infrastructure costs.

Founded in 2022, Sigenergy operates across 86 countries with more than 120 distributors and over 30,000 installers. More than half of its workforce is focused on R&D, and the company reports over 530 patents.

The full presentation is available on the TaiyangNews YouTube channel here.

Recently, Sigenergy introduced SigenStor Neo, an all-in-one residential system integrating PV inverter, battery, and energy management (see Sigenergy’s Residential Storage With Integrated Design And Backup Features).