Technical Analysis of a 240 kW Off-Grid Photovoltaic Energy Storage System

Created on：2026-05-15

240 kW Off-Grid Solar Power and Energy Storage System Configuration Diagram

I. System Overview

This 240kW off-grid photovoltaic energy storage system is designed for commercial and industrial off-grid power supply applications. It integrates high-efficiency photovoltaic modules, intelligent combiner and control units, high-capacity energy storage batteries, and high-power off-grid inverters to establish a comprehensive energy system comprising “solar energy collection—power regulation—energy storage buffering—stable output.” The system has a total installed capacity of 240 kW and is configured with 400 pieces of 605W monocrystalline silicon solar panels, 8 6-input-1-output combiner boxes, 8 384V/80A solar controllers (SW1-80), one 240kWh high-voltage lithium-ion battery pack, and one 100kW three-phase off-grid inverter (SW-TP-100), designed for a 384V DC bus voltage, it outputs standard industrial three-phase 380V/50Hz power. Featuring high stability, reliability, and strong environmental adaptability, it meets the continuous and stable power supply needs of remote factories, standalone campuses, and areas without grid access. It also offers core functions such as peak shaving and valley filling, emergency power supply, and energy self-sufficiency, effectively reducing reliance on traditional energy sources and enabling green, low-carbon power supply.

Wiring Diagram for a 240 kW Off-Grid Solar Power and Energy Storage System

 

How a 240 kW Off-Grid Solar Energy Storage System Works

II. Technical Specifications and Selection Analysis of Core Equipment

(1) Photovoltaic Modules (605W High-Efficiency Solar Panels)

This project utilizes 400 high-efficiency 605W monocrystalline silicon photovoltaic modules to serve as the system’s primary source of solar energy. The key parameters are as follows: Open-circuit voltage 49.8V, short-circuit current 13.6A, operating voltage 41.6V, operating current 10.8A. Each module features high conversion efficiency, excellent low-light performance, and temperature adaptability, making it suitable for long-term operation in complex outdoor environments.
The module selection and string design are closely matched to the system’s DC bus requirements: a string configuration of 10 modules in series and 5 strings in parallel is adopted. With 10 modules in series, the operating voltage of a single string is 416V (41.6V × 10), and the open-circuit voltage is 498V (49.8V × 10), which is slightly higher than the system’s 384V DC bus voltage, ensuring stable voltage output even under fluctuating light conditions; When 5 strings are connected in parallel, the operating current of a single array is 54A (10.8A × 5), and the short-circuit current is 68A (13.6A × 5). These current parameters match the 80A rated current of the downstream solar controller, providing ample current redundancy to prevent the risk of overload. The 400 modules are divided into 8 arrays (50 modules per array), with each array independently connected to a combiner box and a controller. This modular design facilitates future expansion, maintenance, and fault isolation; a failure in a single array does not affect the overall system operation, significantly enhancing the system’s fault tolerance.

(2) Combiner Box and Solar Controller

1. Junction boxes (6 inputs, 1 output; 8 units)

The system is configured with 8 6-input, 1-output combiner boxes, with each combiner box connecting to 5 series strings of PV modules to achieve centralized current collection, monitoring, and protection for the PV array. The combiner boxes feature lightning protection, overcurrent protection, short-circuit protection, and reverse connection protection. They are equipped with built-in intelligent monitoring modules that collect real-time voltage and current data from each branch. In the event of an anomaly, they quickly disconnect the faulty branch to ensure the safe operation of the PV array. The 6-input, 1-output interface design precisely matches the 5-string parallel configuration of a single array, reducing line losses and improving power transmission efficiency. With 8 combiner boxes operating in parallel, the system efficiently collects power from 400 PV modules.

2. Solar controllers (SW1-80, 384 V/80 A, 8 units)

Each combiner box is equipped with one SW1-80 solar controller. The DC input voltage is compatible with a 384V busbar, and the rated current is 80A, which fully matches the 54A operating current of a single array. This provides approximately 48% current redundancy, enabling the system to handle current surges caused by peak sunlight or temperature fluctuations and preventing controller damage due to overload. The controller employs Maximum Power Point Tracking (MPPT) technology with a tracking efficiency of ≥99%, enabling real-time capture of the photovoltaic array’s maximum output power to maximize solar energy utilization. It supports dual-mode switching between solar priority and grid priority; in this off-grid scenario, solar priority is set by default, prioritizing the use of photovoltaic power for supply. Excess energy is automatically stored in the energy storage battery, and when sunlight is insufficient, the battery discharges to supplement power, achieving efficient utilization of solar energy. It also features protection against overcharging, over-discharging, overcurrent, and short circuits, precisely matching the charging and discharging requirements of 384V high-voltage lithium-ion battery packs to extend battery lifespan.

(3) High-voltage lithium-ion battery pack (240 kWh, SW-H15-240KWH)

The energy storage unit utilizes the SW-H15 series 240kWh high-voltage lithium-ion battery pack with a rated voltage of 384V, which is fully compatible with the system’s DC bus voltage. This eliminates the need for additional voltage conversion equipment, thereby reducing energy loss. The battery pack utilizes lithium iron phosphate (LiFePO₄) cells, offering advantages such as a long cycle life, high safety, high-temperature resistance, and no risk of thermal runaway. It is well-suited for the frequent charging and discharging conditions typical of long-term off-grid commercial and industrial systems, with a cycle life of ≥6,000 cycles, ensuring stable operation for over 10 years.
With a capacity of 240 kWh, the battery pack effectively matches a 240 kW PV installation and a 100 kW inverter: During periods of ample sunlight, solar energy is prioritized for powering loads, with surplus energy stored in the battery; the maximum hourly charging rate can reach 80 kWh (8 controllers × 80 A × 384 V); At night or on cloudy/rainy days, the battery discharges to provide DC power to the inverter, supporting continuous discharge for a 100kW load for approximately 2.4 hours. This effectively addresses the issue of intermittent PV power supply and ensures uninterrupted operation of the load. The battery pack features a built-in BMS (Battery Management System) that monitors individual cell voltage, temperature, and SOC (State of Charge) in real time. It includes protection against overcharging, over-discharging, overcurrent, high temperature, and low temperature. In the event of an anomaly, the system rapidly disconnects the circuit and triggers an alarm. Additionally, it supports expansion with battery inspection modules, enabling precise localization of faulty cells for rapid maintenance and reduced O&M costs.

(4) Off-grid inverter (SW-TP-100, 100 kW)

The system’s core inverter unit is the SW-TP-100, a 100 kW three-phase high-power off-grid inverter designed for 384 V DC input and three-phase 380 V/50 Hz AC output, making it fully compatible with the power supply requirements of three-phase commercial and industrial loads. It offers significant core technical advantages.
 

 

100kW Three-Phase High-Power Off-Grid Inverter
High-Efficiency and Stable Output

Inverter conversion efficiency >85%, Sixth-generation IGBT power devices feature high-speed switching, low saturation voltage drop, low losses, and low temperature rise, ensuring efficient operation under high-power conditions and minimizing energy loss; the inverter produces a pure sine wave with total harmonic distortion (THD) of the phase voltage <3% (at 100% linear load). The clean waveform is suitable for various loads, including precision instruments and industrial motors, preventing equipment damage caused by harmonic distortion.

Strong Load Adaptability

Supports 0%–100% load step changes, capable of handling complex operating conditions such as load start/stop and power fluctuations; Capable of withstanding 130% overload for 10 minutes and 130%-150% overload for 60 seconds, handling short-term surge loads; supports continuous operation with 100% load imbalance, accommodating three-phase load imbalance scenarios with stable output voltage, static error ≤±1%, and dynamic error ≤±3%, delivering power quality that meets utility grid standards.

Comprehensive Protection Mechanisms

Integrated with multiple intelligent protections, including input/output overvoltage and undervoltage, surge, phase sequence, overload, short circuit, high temperature, and battery overcharge/overdischarge. In the event of a fault, it triggers real-time alarms and cuts off the output, ensuring comprehensive system safety; Equipped with RS232/RS485 communication interfaces, supporting remote monitoring and control, allowing real-time viewing of system operating parameters and fault information, facilitating remote operation and maintenance.

Industrial-Grade Reliability

Features a three-phase, four-wire design with wide-range AC output compatibility (220V/380V/400V/415V) to meet load requirements in various regions; offers strong environmental adaptability with an operating temperature range of 0–40°C and relative humidity ≤90%, ensuring long-term stable operation in outdoor industrial environments; features a compact overall structure with dimensions optimized for high-power heat dissipation, and a moderate weight for easy installation and maintenance.

III. Overall System Architecture and Operating Principles

(1) System Architecture Design

This system employs a modular, distributed architecture and is divided into four core modules: the PV collection unit, the combiner control unit, the energy storage unit, and the inverter output unit. The architecture is clear and well-structured, facilitating installation, commissioning, expansion, upgrades, and troubleshooting.
The PV collection unit consists of 400 605W PV modules, divided into 8 arrays, each comprising 50 modules (10 strings in series and 5 in parallel). The combiner control unit includes 8 6-input/1-output combiner boxes and 8 SW1-80 solar controllers; each PV array corresponds to one set of combiner and control equipment, enabling power consolidation, maximum power point tracking, and charge management. The energy storage unit consists of one 384V/240kWh high-voltage lithium-ion battery pack, connected in parallel to the DC busbar to serve as an energy buffer and backup power source; the inverter output unit comprises one SW-TP-100 inverter, connected to the DC busbar, which converts DC power into three-phase 380V/50Hz AC power to directly supply industrial loads.

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(2) How the System Works

The system operates under four main conditions: solar power generation, battery charging, battery discharge, and fault protection, ensuring a stable power supply at all times:
Adequate sunlight conditions

Photovoltaic modules absorb light energy and convert solar energy into direct current (DC). After being collected in the combiner box, the solar controller performs Maximum Power Point Tracking (MPPT) and outputs a stable 384V DC voltage to the DC bus. At this time, the PV output power is prioritized for the inverter, which converts it into alternating current (AC) for use by the load; if the PV output power exceeds the load power, the excess energy is automatically stored in the lithium-ion battery bank via the controller until the battery is fully charged.

Low Light / Nighttime Conditions

When the PV modules produce insufficient power or no output, the lithium battery bank automatically discharges to provide 384V DC to the DC busbar, allowing the inverter to operate normally and continue supplying power to the loads. When the battery SOC drops to the preset lower limit, the system triggers low-battery protection, prioritizing power supply to critical loads to prevent battery damage from over-discharge.

Load Fluctuation Conditions

The inverter features strong load adaptability, responding in real time to changes in load power. The PV and energy storage systems work in coordination to rapidly adjust output power, ensuring stable voltage and frequency and preventing system shutdowns caused by load fluctuations.

Fault Protection Scenarios

All system devices are equipped with multiple layers of protection. In the event of abnormalities such as overvoltage, overcurrent, short circuits, overheating, or battery faults, the corresponding device rapidly disconnects the faulty circuit. The inverter issues a real-time alarm and displays a fault code, enabling O&M personnel to quickly locate the fault, ensure system safety, and prevent the fault from escalating.

IV. Technical Advantages and Innovations

(1) Highly adaptable string design for maximum light utilization

The photovoltaic modules are configured in a 10-string-by-5-module array, precisely matched to the 384V DC bus voltage. Their voltage and current parameters are highly compatible with the combiner boxes and controllers, minimizing voltage conversion and current losses. The MPPT controllers feature high tracking efficiency, and the modular array design ensures that a failure in a single string does not affect overall operation, significantly enhancing solar energy capture efficiency and the system’s fault tolerance.

(2) Synergy between Solar Power and Energy Storage: Addressing the Challenges of Intermittent Power Supply

The 240kWh high-capacity high-voltage lithium-ion battery pack is precisely matched with a 240kW photovoltaic system and a 100kW inverter, enabling a closed-loop operation that allows for on-site consumption of solar energy, storage of surplus power, and supplementation of power during shortages. This effectively addresses the intermittent and fluctuating nature of solar power, ensuring 24-hour uninterrupted power supply to the load and meeting the core requirements of off-grid applications.

(3) High-power pure sine wave inverter with industrial-grade power quality

The SW-TP-100 inverter utilizes sixth-generation IGBT technology, offering high conversion efficiency, a clean output waveform, and low harmonic distortion. It features strong overload capacity and the ability to adapt to load imbalances, delivering power quality that meets industrial utility standards. It is compatible with a wide range of industrial loads, helping to prevent harmonic pollution and the risk of equipment damage.

(4) Multiple layers of intelligent protection ensure system security and reliability

From PV modules, combiner boxes, controllers, and battery banks to inverters, the entire system is equipped with multiple protection mechanisms against overvoltage, overcurrent, short circuits, high temperatures, overcharging, and over-discharging. Dual monitoring via the BMS and inverter provides real-time alerts and rapid protection, reducing the risk of failures. Communication interfaces support remote operation and maintenance, facilitating real-time monitoring and prompt repairs, thereby enhancing system reliability and operational efficiency.

(5) Industrial-grade environmental adaptability, suitable for complex operating conditions

The system’s core components are all industrial-grade, with a wide operating temperature and humidity range, enabling long-term, stable operation in challenging environments such as outdoors, high-temperature settings, and humid conditions. The modular architecture facilitates scalability, allowing for the addition of photovoltaic modules, energy storage batteries, or inverters later on to meet load requirements, thereby flexibly adapting to various power demand scenarios.

V. Application Scenarios and Value Analysis

(1) Application Scenarios

This 240kW off-grid photovoltaic energy storage system is suitable for remote areas without grid power, independent industrial parks, mines, farms, islands, and emergency power supply sites. It provides stable, green three-phase 380V AC power for industrial motors, precision equipment, office equipment, and household use, solving power supply challenges in areas without grid power or with unstable grid power.

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(2) Value Analysis

Economic Value

By replacing traditional diesel generators, it eliminates the need for diesel fuel, significantly reducing operating costs. With a service life of ≥25 years for photovoltaic modules, ≥10 years for battery packs, and ≥15 years for inverters, the system offers low lifecycle maintenance costs and a high long-term return on investment.

Environmental Value

Utilizing clean solar energy, it produces zero carbon emissions and zero pollution, aligning with the principles of green and low-carbon development. It contributes to achieving carbon neutrality goals and reduces reliance on traditional fossil fuels.

Safety Value

Multiple intelligent protection mechanisms and end-to-end security safeguards enable rapid fault isolation, preventing equipment damage and safety incidents; off-grid independent operation ensures strong power supply stability, unaffected by grid fluctuations or power outages.

Flexibility Value

Modular design and flexible scalability accommodate varying power load requirements; remote monitoring and maintenance reduce labor costs, improve management efficiency, and meet operational needs in remote locations.

VI. Conclusion

This 240kW off-grid photovoltaic energy storage system integrates high-efficiency photovoltaic modules, intelligent combiner box control, high-capacity energy storage, and high-power inverters to deliver a technologically advanced, stable, reliable, economical, and environmentally friendly off-grid power supply solution. With precise parameter matching, a rational architectural design, and comprehensive protection mechanisms, the system offers advantages such as high solar energy utilization, strong load adaptability, a long service life, and low O&M costs. It effectively addresses the challenges of power supply in off-grid scenarios, meets the high-standard power supply requirements of commercial and industrial applications, and delivers significant economic, environmental, and safety benefits. As an ideal choice for green power supply in remote areas without grid access, it serves as an excellent model for the large-scale application of photovoltaic energy storage technology in off-grid applications.

 

 

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