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A ground-mount solar plant with bESS – In practice

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1. Project Summary

Grid Interface: 400 V LV / 11 kV MV

This project involved the design of a ground-mounted solar PV plant paired with a battery energy storage system (BESS), combining PV generation, energy storage and grid interface equipment into a single integrated design. The headline figures for the system are summarised below.

  • PV System Capacity: 897.12 kWp DC
  • PV AC System Capacity: 400.00 kW AC
  • Battery Energy Storage Capacity: 940.40 kWh
  • PV Modules: 1,424 × 630 Wp bifacial modules
  • PV Inverters: 4 × 100 kW AC inverters
  • BESS: 4 × 235.1 kWh battery cabinets
  • Grid Interface: 400 V LV / 11 kV MV

Key Design Considerations

  • The final construction design should be checked against the applicable project-specific standards, manufacturer requirements and grid-connection requirements.
  • Array orientation, tilt, row spacing and pitch were selected as part of the overall site layout.
  • Inverter string configuration was designed around the module and inverter electrical limits.
  • Cable sizing and voltage drop were considered for DC, LV AC, MV and BESS circuits.
  • PV and BESS equipment were coordinated within the overall site and electrical layout.
  • Grid interface equipment includes LV AC combining, transformer, MV switchgear and G100 protection.

Design and Technology

The design addressed these considerations through a detailed technical specification covering the PV modules, inverters, mounting structure, array layout, inverter stringing, battery storage, cabling, monitoring, earthing and civil works.

Solar PV Modules
  • Module Type: AE SOLAR AE CMER-132BDS 630 W bifacial module.
  • Power Rating: 630 Wp.
  • Module efficiency: 23.34% at STC.
  • Voc: 50.20 Vdc; Vmp: 42.00 Vdc.
  • Isc: 16.09 A; Imp: 15.00 A.
  • Maximum system voltage: 1500 Vdc.
  • Module dimensions: 2382 × 1133 × 30 mm.
  • Module weight: 33.7 kg.
Inverter System
  • Inverter Type: SOLIS S6-GC100K.
  • Quantity: 4 units.
  • AC rating: 100 kW per inverter.
  • Nominal AC voltage: 400 V.
  • Maximum output current: 167.1 A.
  • Maximum DC voltage: 1100 V.
  • MPPT operating voltage: 160–1000 V.
  • MPPT / strings per MPPT: 10 / 2.
  • EU weighted efficiency: 98.3%.
Mounting System
  • Structure: Fixed-tilt, single-support system with driven piles.
  • Orientation: South-facing.
  • Module orientation: Portrait.
  • Azimuth: 180°.
  • Tilt angle: 20°.
  • Inter-row spacing: 6.560 m.
  • Pitch distance: 11.056 m.
  • Mounting racks: 32 × 2-row × 10-column and 56 × 2-row × 7-column configurations.

Electrical Configuration

Array Layout

  • The PV array uses a fixed-tilt, south-facing ground-mount arrangement.
  • The layout provides dedicated access roads, pedestrian routes, PV perimeter space and equipment areas.
  • The array is divided into 2-row × 10-column and 2-row × 7-column rack configurations.
  • The design uses 6.560 m inter-row spacing and 11.056 m pitch distance.
  • The layout incorporates four PV inverters and eight DC combiner boxes.

Inverter Stringing

The design documentation identifies 14 strings of 14 modules for each 100 kW inverter, giving 196 modules per inverter.

PV*SOL Performance

The supplied PV*SOL simulation provides the following performance reference for the sample PV system:

Battery Energy Storage System

  • Battery system: Alpha ESS STORION-LC235.
  • Quantity: 4 battery cabinets.
  • Battery capacity: 235.1 kWh per cabinet.
  • Total BESS capacity: 940.40 kWh.
  • PCS: PWS1-500KTL-EX-8M1, 500 kW.
  • BESS transformer: WT500K, 500 kVA, 400 V / 400 V, Dyn11.
  • DC/DC converter: PDS1-400K.
  • DC junction cabinet and BESS house are included in the design.
  • EMS and SCADA are included for control, monitoring and energy management.

BESS Electrical Configuration

Cable Selection & Voltage Drop

  • PV string cabling: 6 mm² copper cable.
  • Typical string-to-inverter voltage drop is below 1% in the supplied calculations.
  • PV inverter AC cabling: 4C × 240 mm² plus 1C × 120 mm² copper cable.
  • The supplied calculations show inverter AC voltage drops from approximately 1.10% to 2.67%, depending on cable route length.
  • PV transformer to MV switchgear: 3C × 50 mm² MV cable.
  • BESS DC cabling from the DC junction cabinet to battery cabinets uses 2C × 50 mm² cable.

Monitoring & Energy Management

  • EMS is provided for energy management and system control.
  • SCADA provides system monitoring and communication.
  • RS485, Ethernet and associated communication interfaces are shown in the supplied electrical documentation.
  • The design includes export/import metering and G100 protection/control equipment.
  • Battery management communication includes BAMS and CAN interfaces.

Earthing & Protection

  • The design includes dedicated earthing routing for PV and BESS equipment.
  • PV module frames and exposed metallic equipment are connected to the earthing system.
  • The supplied design specifies a minimum 4 mm² copper conductor for grounding exposed PV module frames.
  • G100 protection is included at the grid interface.
  • The electrical design incorporates DC and AC surge protection and isolation equipment.

Civil Works & Access

  • The design includes underground cable trenches and dedicated cable routes.
  • DC cables are routed through underground ducting where required.
  • Dedicated access roads and pedestrian access routes are provided.
  • Equipment areas are allocated for PV inverters, combiner equipment, transformer, BESS and electrical plant.
  • The layout provides a defined PV perimeter and maintenance access.

Taken together, the design demonstrates that the PV and BESS system can be engineered as a coordinated, code-compliant whole, with the key design decisions validated against performance and electrical requirements.