10 kW Grid-Tied/Off-Grid Hybrid Solar System Configuration Diagram

I. Overview of the Plan

This solution is designed to meet the needs of European residential areas, farms, remote rural areas, and island pastoral regions by deploying a 10 kW hybrid grid-connected and off-grid energy storage photovoltaic system. It utilizes N-type double-glass 590 Wp high-efficiency photovoltaic modules, an SW 10K-EU 10 kW hybrid photovoltaic-storage inverter, and a 51.2V 340Ah lithium iron phosphate (LiFePO₄) battery pack, to provide comprehensive functionality including self-consumption of generated solar power, storage of surplus electricity, grid-synchronized charging, and emergency power supply during outages. The system is designed for an average daily peak sunlight duration of 5 hours, with a theoretical average daily PV generation of 59 kWh. The energy storage system can store 17.5 kWh of electricity per day, significantly reducing the cost of purchasing electricity from the grid and meeting the energy needs of areas without a stable grid, with large peak-to-off-peak price differentials, or with unstable power supply.

Topology Diagram of a 10 kW Grid-Connected/Off-Grid Hybrid Solar System

The entire system consists of five core components: a photovoltaic array, a hybrid energy storage inverter, a lithium-ion battery pack, power distribution loads, and a utility grid connection. It employs a dual-independent MPPT photovoltaic input architecture and supports the coordinated dispatch of four energy sources—photovoltaic, batteries, grid power, and diesel generators, and supports multiple operating modes, including grid-connected operation, off-grid standalone power supply, and economic charge-discharge arbitrage. It features comprehensive electrical protection, wide-temperature-range operation, and high-reliability long-duration output capabilities. The system complies with IEC international safety standards and meets the European Union’s market access requirements for residential renewable energy systems.

10 kW Grid-Tied/Off-Grid Hybrid Solar System Configuration Diagram

II. Key Equipment Specifications and Selection Criteria

(1) PV Array: 590Wp N-TOPCON Double-glass Modules (16 pieces, 2 strings × 8 pieces per string)

The selected N-type TOPCon bifacial double-glass monocrystalline photovoltaic modules, with a peak power of 590 Wp per module, are currently the mainstream products for high-performance residential PV systems. Their core electrical parameters are as follows:
Standard Test Conditions (STC): Open-circuit voltage (Voc) = 51.86 V, maximum power point voltage (Vmp) = 43.01 V, short-circuit current (Isc) = 14.50 A, module conversion efficiency 22.80%;

Temperature characteristics: Open-circuit voltage temperature coefficient -0.25%/°C; voltage increases in low-temperature environments and decreases slightly in high-temperature environments;

System Configuration: A total of 16 modules, divided into 2 independent PV strings, with 8 modules in series in each string. The two strings are connected to the inverter’s two independent MPPT channels, matching the inverter’s maximum PV input power limit of 2×7700W.

(2) Energy Storage Hybrid Inverter: SW 10K-EU 10 kW Grid-Tied/Off-Grid Hybrid Unit

The core control unit of this system is the SW 10K-EU European-standard hybrid photovoltaic-storage inverter, specifically designed for 48V low-voltage energy storage batteries. Key compatibility parameters:
PV Input: Two independent MPPT channels, with a maximum input of 7,700 W per channel; MPPT operating voltage range of 120 VDC to 450 VDC; maximum input current of 22 A per channel; maximum PV open-circuit voltage tolerance of 500 VDC;

Battery Port: Compatible with 48 VDC energy storage systems; maximum hybrid charging current of 200 A; compatible with lithium-ion and lead-acid batteries; supports BMS communication and integration;

AC Output: Rated 10,000 VA/10,000 W pure sine wave output, short-term peak 20,000 VA; supports up to 6 units in parallel to form a three-phase, four-wire system; switchable between utility power and PV dual-priority modes;

Operational Performance: Peak conversion efficiency of 93%, utility/PV/battery switching time ≤ 20 ms, IP21 protection rating, operating temperature range -10°C to 55°C.

SW 10K-EU 10kW Hybrid On/Off Grid Inverter

(3) Energy Storage Battery Pack: 51.2V, 340Ah lithium iron phosphate battery

The energy storage unit uses low-voltage lithium iron phosphate (LiFePO₄) batteries with a nominal voltage of 51.2 V and a rated capacity of 340 Ah. The total energy storage capacity is calculated as follows: Energy storage capacity = 51.2 V × 340 Ah = 17,408 Wh ≈ 17.5 kWh, which perfectly matches the daily energy storage target specified in the plan.

The battery is integrated with an intelligent BMS (Battery Management System) that enables bidirectional communication with the inverter, allowing real-time monitoring of cell voltage, temperature, and charge/discharge currents. It features multiple protection mechanisms against overcharging, over-discharging, overcurrent, short circuits, and high temperatures, and is designed for long-term cyclic charging and discharging. It serves to store excess solar energy during the day, power loads at night, and provide emergency backup power during outages. The inverter’s battery port is rated at 48 VDC, and the 51.2 V lithium-ion battery’s float charge and charge/discharge ranges are fully compatible with the inverter’s battery management system, eliminating the need for additional step-down conversion equipment.

III. Verification of PV String Voltage Matching (Core Technical Calculations)

The number of strings connected in series directly determines the DC voltage of the photovoltaic system. If the voltage exceeds the inverter’s MPPT range, power generation will fail and the system will shut down due to equipment protection. This section includes three types of verification—operating voltage under standard conditions, open-circuit voltage at normal temperature, and maximum open-circuit voltage at extreme low temperatures—to verify whether the 8-string configuration is compatible with the inverter’s 120–450 VDC MPPT window.

1. Maximum Power Point Voltage (Vmp) of the string under standard test conditions (25°C STC) Total

Single module Vmp = 43.01 V; 8 modules in series: Total Vmp = 43.01 V × 8 = 344.08 V. The inverter’s MPPT operating range is 120 VDC to 450 VDC; 344.08 V falls in the middle of this range, allowing the MPPT to stably track maximum power and achieve optimal power generation efficiency.

2. Standard Open-Circuit Voltage (Voc) at 25°C, Total

A single module has a Voc of 51.86 V. In a string of 8 modules connected in series, the total Voc is 51.86 V × 8 = 414.88 V, which is less than the inverter’s MPPT upper limit of 450 VDC and significantly higher than the lower limit of 120 VDC. At normal temperatures, the voltage falls entirely within the MPPT’s effective operating range.

3. Verification of Maximum Open-Circuit Voltage in Extreme Low-Temperature Environments (Inverter’s Minimum Operating Temperature: -10°C)

The temperature coefficient of the module’s open-circuit voltage (Kvoc) is -0.25%/°C; for every 1°C decrease in temperature, the open-circuit voltage increases by 0.25%. The system’s minimum operating temperature is -10°C, resulting in a temperature difference (ΔT) of -35°C from the standard 25°C. Low-temperature Voc correction value for a single module: Voc at low temperature = Voc × [1 + ΔT × Kvoc] = 51.86 × [1 + (-35) × (-0.0025)] = 51.86 × 1.0875 = 56.40 V. Total open-circuit voltage at the extreme low temperature for a single string of 8 modules: Voc (string at low temperature) = 56.40 V × 8 = 451.2 V. This value only slightly exceeds the inverter’s MPPT upper limit of 450 VDC, and the inverter’s PV port has a maximum open-circuit voltage tolerance of 500 VDC. The MPPT upper limit is only briefly reached under extreme cold conditions of -10°C; under normal conditions above 0°C, the string open-circuit voltage remains below 440V, ensuring completely stable operation; if the project is located in a region with long-term temperatures below -10°C, the number of cells in a string can be optimized; this solution poses no compatibility risks for use in typical temperate and subtropical regions.

4. String Current Matching Verification

The short-circuit current (Isc) of a single module is 14.50 A. After connecting multiple modules in series, the current remains at 14.50 A. The maximum input current for a single MPPT channel on the inverter is 22 A. Since 14.50 A < 22 A, there is sufficient current margin, and overcurrent protection will not be triggered; The total PV power of the two string arrays is 16 × 590 W = 9,440 W. The inverter’s maximum PV input for two channels is 2 × 7,700 W = 15,400 W, providing ample room for future expansion.

IV. Estimation of System Power Generation and Energy Storage Capacity

(1) Calculation of Average Daily Photovoltaic Power Generation

Total installed capacity of the PV system: 16 panels × 590 Wp = 9,440 Wp = 9.44 kWp. The project is designed for an average of 5 hours of peak effective sunlight per day. Calculation of ideal peak power generation assuming no losses: Ideal peak power generation = 9.44 kW × 5 h = 47.2 kWh;

(2) Analysis of Energy Capacity Matching for Energy Storage Systems

The lithium-ion battery has a total energy storage capacity of 17.5 kWh, providing a storage solution for surplus solar power generated during the day. The system operates as follows:
During daylight hours, solar power is prioritized to directly supply household loads; any remaining power after the loads are met is fed into the lithium-ion battery for charging, with a maximum daily storage capacity of 17.5 kWh of clean electricity;

In the evening and at night when there is no sunlight, the lithium-ion battery discharges stored energy to power the loads, reducing the need to draw power from the utility grid;

When PV output is insufficient and the battery is depleted, the inverter automatically switches to a hybrid mode with the utility grid to ensure stable power supply to the loads;

In the event of a grid outage, the system switches to pure off-grid mode, with the battery capable of supporting 17.5 kWh of load consumption to provide emergency power for essential household appliances.

Logic behind matching energy storage capacity with PV installation: The average daily surplus PV generation is approximately 17–20 kWh. A 17.5 kWh battery perfectly absorbs the excess daytime electricity, preventing both the waste of surplus power due to insufficient storage capacity and the idling of initial investment caused by excessive battery capacity, thereby achieving an optimal balance between PV generation capacity and energy storage capacity.

51.2V 340Ah Lithium Iron Phosphate Energy Storage Battery Pack

V. Detailed Explanation of the System’s Operating Modes

Leveraging the multi-source energy dispatch logic of the SW 10K-EU hybrid inverter, the system supports four smart operating modes to accommodate different power consumption scenarios:

1. Photovoltaic Priority Grid-Connection Mode (Mainstream Mode for Daily Use)

Solar power is supplied to local loads immediately, and excess power automatically charges the lithium-ion battery; once the battery is fully charged, the remaining power can be fed into the utility grid; when solar output is insufficient, the utility grid automatically supplements the power shortfall. The inverter’s dual-priority strategy allows for seamless switching between solar priority and grid priority, accommodating peak-valley electricity price arbitrage needs.

2. Energy-Saving Charge/Discharge Mode (Electricity Cost Optimization Mode)

The inverter features a built-in time-of-use scheduler that can be configured to operate automatically during specific time periods: during off-peak hours, the grid charges the battery; during peak hours, the battery discharges to power the load, thereby reducing peak grid electricity consumption and significantly lowering monthly electricity costs. This offers significant long-term economic benefits for farms and single-family homes.

3. Hybrid Synergistic Power Supply Mode

During rainy or overcast weather with insufficient sunlight, when photovoltaic output is low, the inverter synchronizes the three energy sources—photovoltaic power, battery power, and utility power—to jointly supply the load, ensuring the stable operation of the 10 kW rated load without power outages or voltage drops. The system also supports the connection of an external diesel generator; in the event of a utility power outage, it can automatically activate the generator to work in conjunction with the battery to provide power, making it suitable for remote, off-grid pastoral areas and islands.

4. Off-Grid Emergency Standby Mode

The moment a power grid failure causes a blackout, the inverter rapidly switches to off-grid pure sine wave output within 10 ms, relying solely on solar power and the battery to supply power to critical loads—ensuring no interruption in power supply and addressing the pain points of unstable power grids and frequent power outages in rural and suburban areas. With a peak power of 20,000 VA, the inverter can handle the startup surges of high-power motor-driven loads such as air conditioners and water pumps.

France: 10 kW Grid-Connected/Off-Grid Hybrid Solar System

VI. System Security and Environmental Compatibility

(1) Multi-tiered Electrical Protection System

PV Side: Overvoltage, overcurrent, reverse connection, and DC insulation fault protection; automatic MPPT power reduction in case of overvoltage;

Battery Side: Dual interlock protection between the BMS and inverter; shutdown in case of overcharge, over-discharge, overcurrent, or high temperature;

AC Side: Protection against grid overvoltage, undervoltage, overfrequency, short circuits, and ground faults; anti-islanding protection for grid-connected systems;

Overall Protection: IP21-rated enclosure, dust- and drip-resistant, suitable for installation in indoor server rooms or simple outdoor shelters.

(2) Ability to Adapt to a Wide Range of Environments

Operating Temperature Range: Inverter - 10°C to 55°C, PV modules - 40°C to 85°C, batteries 0°C to 50°C; can be used reliably in both northern and southern regions with high and low temperatures;

Altitude Compatibility: The entire unit supports operation without derating at altitudes up to 2,000 meters, making it suitable for high-altitude rural areas and mountainous farms;

Humidity Tolerance: Operates in non-condensing environments with humidity levels between 5% and 95%, posing no risk of corrosion in coastal islands with high humidity or rainy regions in southern China;

Electromagnetic Compatibility: Class B EMC certification ensures it does not interfere with televisions, communication systems, or household low-voltage equipment.

(3) Equipment Standardization and Reliability

The inverter supports the parallel connection of up to six units to expand capacity; as the load increases in the future, multiple units can be connected in parallel to form a high-power three-phase, four-wire system. The photovoltaic modules feature an N-type double-glass structure, with a degradation rate significantly lower than that of conventional single-glass modules, ensuring stable power generation returns for 30 years. The lithium-ion batteries have a cycle life exceeding 8,000 cycles and can be used reliably for more than 10 years with daily charging and discharging.

VII. Summary of the Solution’s Practical Value

This 10-kW photovoltaic-storage hybrid system achieves efficient utilization of clean energy through rigorous string voltage matching calculations and a balanced configuration of photovoltaic and energy storage capacities. Its core value is divided into four key dimensions:

Cost Reduction

With a theoretical average daily solar power generation of 59 kWh and 17.5 kWh of energy storage for peak shaving and off-peak charging, this system significantly reduces grid power consumption. The equipment investment pays for itself over the long term, offering outstanding cost benefits for farms, single-family homes, and remote rural areas;

Stable Power Supply

Grid-tied and off-grid dual-mode operation, ensuring uninterrupted power supply during grid outages; suitable for areas with unreliable or no power grid;

Reliable device compatibility

The voltage of the string consisting of 8 modules connected in series falls within the inverter’s core MPPT operating range; even under extreme low-temperature conditions, it only slightly touches the upper limit, ensuring safe electrical matching with no safety hazards; dual independent MPPT channels enhance power generation efficiency under low-light conditions;

High versatility across different scenarios

A single system covers a wide range of scenarios, including residential areas, farms, communication base stations, islands, and pastoral regions. It supports dual-energy expansion via both grid power and diesel generators. The standardized equipment is easy to procure, install, and maintain, and complies with EU market access regulations for renewable energy.

The complete solution balances rigorous theoretical design with stable on-site operation, with voltage, power, and energy storage capacity optimized to work in tandem. It serves as a standardized, mature technical solution for small- and medium-sized residential, as well as small-scale commercial and industrial off-grid and grid-connected energy storage projects, offering significant value for widespread adoption and implementation.