Technical Scheme of 50kW Grid-connected PV Energy Storage System for Industry & Commerce in Spain

Created on：2026-08-06

📋1. Project Overview

This project is implemented at an industrial and commercial plant in Spain to build an integrated hybrid PV-energy storage system featuring self-consumption, peak-valley energy storage and surplus electricity grid connection. The system is equipped with 48 pieces of 720W bifacial PV modules, a 50kW three-phase hybrid grid-tied inverter with 4 MPPT channels, and a 51.2kWh rack-mounted high-voltage lithium iron phosphate battery pack. The system achieves a daily PV power generation of 172 kWh and daily energy storage capacity of 50 kWh.

Configuration Diagram of 50kW/50kWh PV Energy Storage System

Spain boasts abundant solar irradiance and a significant gap between peak and off-peak electricity prices day and night. During the daytime, photovoltaic power supplies the factory loads preferentially, and surplus electricity is stored in energy storage batteries. At night during peak tariff periods, stored energy is discharged for power supply, and leftover electricity is fed into the local public grid. Companies cut electricity expenses by taking advantage of peak-valley price spreads. All modular equipment allows rapid on-site installation and flexible capacity expansion in later stages.

 

Video on Working Principle of 50kW/50kWh PV Energy Storage System

2. Basic Parameters of Core Equipment

2.1 PV Modules (720W Bifacial PV Modules)

Parameters under Standard Test Conditions (STC): Peak power: 720W; Open-circuit voltage Voc=50.26V; Maximum power voltage Vmp=42.24V. Temperature coefficient of open-circuit voltage: -0.24%/°C; Operating temperature range of modules: -40°C ~ +85°C.

PV Array Layout Drawing on Factory Rooftop

2.2 Energy Storage Battery Modules

Single module specification: 5.12kWh, 51.2V, 100Ah LiFePO4 battery, Model SW-G10, rated voltage 51.2V per module. A maximum of 16 modules can be connected in series. Ten modules wired in series form a 512V high-voltage battery cluster with an available capacity of 46.08 kWh.

2.3 Energy Storage Inverter (50kW Three-Phase Hybrid Grid-Tied Inverter)

This three-phase 50kW hybrid inverter comes with four independent MPPT PV input channels. MPPT operating voltage range: 200V ~ 850V. DC battery access voltage range: 420V ~ 580V, compatible with the 512V high-voltage battery cluster of this scheme. It supports CAN communication to connect with the energy storage BMS.

50kW Three-Phase Hybrid Grid-Tied Inverter

⚡3. Series & Parallel Design and Voltage Verification of PV Array

3.1 Selection of Series Quantity per PV String

The minimum winter temperature in mountainous northern Spain reaches approximately -5°C. Low temperatures raise the open-circuit voltage of PV modules. The design requires the limit open-circuit voltage under low temperature not to exceed the inverter’s maximum MPPT voltage of 850V, and the operating voltage at normal temperature to stay above the MPPT startup voltage of 200V.

12 modules in series form one PV string: Normal-temperature open-circuit voltage per string: 12 × 50.26 = 603.12 V Low-temperature voltage calculation at -5°C, temperature difference ΔT=30°C: Low-temperature open-circuit voltage = 603.12 × [1 - 0.24% × (-30)] = 646.54 V The limit low-temperature voltage 646.54V ＜ 850V, within the inverter’s safety upper limit. Normal-temperature operating voltage per string: 12 × 42.24 = 506.88V, falling within the inverter’s high-efficiency MPPT range of 200V~850V. The inverter can continuously and stably track the maximum PV power point.

Topology Diagram of 50kW/50kWh PV Energy Storage System

3.2 Layout of PV Strings

Total PV modules: 48 pieces, 12 pieces connected in series per string, forming 4 PV strings in total. The inverter is fitted with four independent MPPT channels adopting one-to-one wiring: each PV string connects to a separate MPPT channel. Even if the rooftop suffers partial shading or inconsistent orientation, the four MPPT channels operate independently without mutual interference to guarantee overall power generation efficiency. Total installed PV capacity = 48 × 720W = 34.56kW, lower than the inverter’s rated AC power of 50kW, reserving space for power expansion and avoiding waste of excess PV power.

🔋4. Wiring Scheme of Energy Storage Batteries (10 × 5.12kWh Modules)

This project deploys 10 battery modules of 51.2V, 5.12kWh. Matching the inverter’s battery access voltage range of 420~580V, all modules are wired in full series.

50kWh Rack-Mounted LiFePO4 Battery Pack (10 × 5.12kWh Modules)

Wiring logic: Ten battery modules are connected end-to-end in series. The overall rated voltage of the battery cluster = 10 × 51.2V = 512V, precisely fitting the inverter’s DC battery voltage window of 420~580V.

Capacity configuration: Total battery cluster capacity 51.2kWh; operating at 90% depth of discharge (DoD), available capacity equals 46.08kWh. The project is designed for daily energy storage of 50kWh. In actual operation, the upper charging SOC limit of the battery per day is controlled at 95%, delivering around 46kWh daily storage capacity. This meets storage demands while avoiding full deep charging to extend battery service life.

Communication & Installation: After series connection, modules integrate a unified BMS. The BMS interacts with the inverter via CAN2.0 bus. The inverter monitors real-time battery voltage, SOC and temperature, and intelligently manages charge and discharge logic. Batteries adopt floor-standing rack installation inside the power distribution room with ambient temperature maintained at 0~35°C. Battery cycle life ≥ 8,000 times.

📊5. Matching of Power Generation, Energy Storage Operating Conditions and Backup Load Duration

5.1 Power Generation Matching

Spain features excellent solar irradiation nationwide with an average annual effective sunshine duration of about 5.0 hours. With 34.56kW installed PV capacity, the theoretical daily power generation = 34.56 × 5 = 172.8 kWh, consistent with the project’s designed daily generation of 172 kWh.

System operation logic: PV power supplies factory loads with priority during daytime. When PV output exceeds load consumption, surplus electricity charges the battery with daily stored energy capped at 50kWh. Batteries discharge to power loads during night peak tariff hours to cut electricity costs. If surplus power remains after meeting loads via PV and storage, excess electricity is fed into the public grid.  

5.2 Backup Load Equipment and Continuous Supply Duration

When mains power fails and the system switches to off-grid mode, the energy storage battery provides emergency power for critical factory equipment. Load configuration and theoretical backup duration are listed below:
Backup Load Equipment Power per Unit Quantity Installed Total Load Power Theoretical Backup Duration
Office Lighting 200W 8 sets 1.6kW 28.8h
Monitoring System 400W 1 set 0.4kW 115.2h
Office Computers 350W 4 units 1.4kW 33h
Access & Fire Control System 500W 1 set 0.5kW 92.2h
Mixed Simultaneous Load (All Devices Running) — — 3.9kW 11.8h
Note: Backup duration is calculated based on 46.08kWh available battery capacity and 95% inverter efficiency. The system can satisfy basic security and office emergency power demands during factory power outages at night.

🔄6. System Operating Modes

  • PV Self-Consumption Mode: PV modules directly power factory loads in daytime and reduce mains power draw.
  • Energy Storage Charging Mode: When PV output exceeds factory power demand, surplus electricity charges the high-voltage battery cluster.
  • Energy Storage Discharging Mode: During night hours without sunlight and peak tariff periods, batteries discharge to supply factory loads and reduce peak electricity bills.
  • Grid-Tied Mode: Excess power generated by PV and storage is exported to the public grid. When the utility grid fails, the inverter automatically switches to off-grid mode to supply emergency power for key loads.

🌟7. Scheme Summary

  • PV Configuration: 48 pieces of 720W modules divided into four strings with 12 modules per string. The low-temperature open-circuit voltage is 646.54V and normal-temperature operating voltage is 506.88V, fully falling within the inverter MPPT voltage range for safe and compliant electrical operation.
  • Energy Storage Configuration: Ten battery modules connected in series form a 512V high-voltage battery cluster compatible with the inverter’s DC storage voltage window. The available capacity meets the daily storage demand of nearly 50 kWh.
  • Operating Condition Matching: The 34.56kW PV array generates 172 kWh daily, matching local solar generation indicators. Relying on Spain’s time-of-use tariff policy, the system realizes self-consumption and peak-valley cost reduction, alongside emergency backup power during grid outages.
  • Expandability: PV strings and battery modules adopt modular structures. Additional PV strings and parallel battery modules can be added later for capacity expansion to accommodate future power consumption growth of enterprises.
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