🏠Ⅰ. Project Overview

This scheme designs a single-phase photovoltaic-energy storage power supply system for rural self-built houses, private villas and small street-side shops. It adopts 14 pieces of 585W photovoltaic modules (7 modules per string, two strings in parallel), an 11kW-48V on/off-grid hybrid inverter & controller all-in-one machine, and two sets of 51.2V/300Ah lithium iron phosphate energy storage batteries. The total photovoltaic power of the system is 8.19kW with a total energy storage capacity of 30.72kWh. The designed daily power generation is 41kWh and daily energy storage capacity is 30kWh.

System Topology Diagram

The system features four core functions: self-generation & self-consumption, surplus electricity storage, peak-valley arbitrage, and emergency backup power during blackouts. It supports 220V single-phase loads including household air conditioners, kitchen & bathroom appliances, lighting fixtures and shop equipment. It greatly cuts grid electricity expenses, solves the problem of power outages without backup power in rural areas and old shops, and balances energy-saving economy and power supply reliability.

 

Video of System Working Principle

⚡II. Core Equipment Parameters & Electrical Matching Verification

2.1 PV Array Configuration & Voltage Verification

(1) Basic Parameters of PV Modules

Standard operating parameters of 585W monocrystalline PV modules: open-circuit voltage Voc=52.7V, maximum power voltage Vmp=44.02V, short-circuit current Isc=14.01A, module efficiency 22.6%. It features anti-PID performance, hail resistance and superior low-light power generation capacity.

585W Solar Panel

Total configuration: 14 modules divided into two strings with 7 modules connected in series per string. The two parallel strings connect to the dual independent MPPT channels of the inverter.

(2) String Voltage Calculation (Core Matching Validation)

MPPT operating range of the 11kW integrated inverter: 90~450VDC;

maximum allowable PV open-circuit voltage: 500VDC. Open-circuit voltage of one 7-module string: 7×52.7=368.9V Operating voltage of one 7-module string: 7×44.02=308.14V

 

Conclusion: The string open-circuit voltage 368.9V is lower than the 500V upper limit and falls within the high-efficiency 90~450V MPPT tracking range. Two independent strings connect to separate MPPT ports, so power generation of the two strings will not interfere with each other under partial roof shading, reducing power loss by over 15%. The electrical parameters of the strings fully comply with and match the inverter.

(3) Total PV Installed Capacity

14 × 585W = 8190W ≈ 8.19kW, leaving sufficient DC input margin for the 11kW inverter and allowing minor expansion of PV modules in the future.

🔋2.2 Energy Storage Battery System

Single battery specification: 51.2V 300Ah lithium iron phosphate, single unit capacity = 51.2×300÷1000=15.36kWh. Two units are connected in parallel for a total system storage capacity of 30.72kWh.

15kWh (51.2V 300Ah) Wall-Mounted Lithium Battery Pack

Core performance: Built-in intelligent BMS management; cycle life ≥6,000 times at 80% depth of discharge; supports 90% maximum depth of discharge. It is fully protected against overcharging, overdischarging, overheating, short circuits, with cell balancing function. CAN communication links directly to the inverter to synchronize real-time data including SOC, voltage and temperature. The system is designed to store 30kWh daily with reserved capacity margin to prevent battery degradation from full charging and extend service life.

2.3📟11kW Hybrid Grid-Tied Integrated Inverter

Electrical specifications: Nominal DC 48V, single-phase AC 220V, rated output 11kW, peak output 22kW; dual independent MPPT channels; maximum conversion efficiency up to 97%.

11kW Hybrid Grid-Tied Inverter

Core functions: All-in-one integration of PV charging, bidirectional battery charge/discharge and grid complementary power supply; seamless switching between grid-tied and off-grid mode within less than 20ms to ensure uninterrupted power supply to loads during blackouts. Built-in Wi-Fi enables remote monitoring of power generation, stored energy, load consumption and fault alarms via mobile APP.

Protection mechanisms: Full-link protection including anti-islanding, DC reverse connection prevention, AC leakage protection, overload protection, over-temperature protection and lightning protection, complying with residential grid connection standards.

🧩Ⅲ. System Topology & Wiring Design (For Construction Reference)

This system adopts a DC-coupled single-phase PV energy storage architecture with five interconnected units: PV array → DC combiner distribution box → integrated inverter → energy storage battery / municipal grid / terminal loads.

 

Connection Diagram of Inverter and Lithium Battery Pack

PV Side Wiring：Two series strings of 7 modules each are equipped with independent 15A DC fuses and DC500V lightning arresters. PV1-F 4mm² dedicated PV cables are used, with two strings connected separately to the dual MPPT ports of the inverter. Cables are laid along roof brackets with sun-proof and waterproof treatment, and combiner boxes are fully sealed against water.

Energy Storage Side Wiring：Two 51.2V batteries are connected in parallel with copper bars linking positive and negative poles; conductive grease is applied on contact surfaces to prevent oxidation. The total battery output connects to the inverter battery terminals via a DC disconnector. BMS communication wires and power cables are routed separately to avoid electromagnetic interference.

AC Side Wiring：AC output of the inverter, grid incoming lines and household load lines are all connected to the indoor distribution box. Neutral wire (N) and protective earth wire (PE) are strictly separated. The overall system grounding resistance is ≤4Ω. A 63A main circuit breaker is installed on the incoming side, together with AC lightning arresters and residual current circuit breakers.

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Full-Link Protection Configuration

• DC side: Lightning protection, fuses, disconnectors, reverse connection protection
• Energy storage side: BMS cell balancing, over/under voltage protection, overheating protection, short circuit protection
• AC side: Leakage protection, overcurrent protection, anti-islanding protection, AC lightning protection

📊Ⅳ. Power Generation & Operating Condition Calculation

Daily Power Generation Calculation

Installed PV capacity: 8.19kW; local average daily effective sunshine duration: 5 hours. Comprehensive system loss (including module attenuation, DC cable loss, inverter loss and AC transmission loss) totals approximately 7.2%. Theoretical daily generation = 8.19 × 5 = 40.95kWh, converted to stable actual daily power generation of 41kWh, consistent with design targets.

Daily Power Consumption & Energy Storage Allocation Logic

The PV system generates 41kWh during daytime. Villas and small shops consume about 11kWh daily for household appliances, lighting and small air conditioners, with surplus 30kWh stored in batteries to meet the daily 30kWh storage target. At night without PV power output, the battery discharges 30kWh to supply all household night loads and drastically reduce grid power consumption.

Supplementary Extreme Operating Conditions

In continuous rainy days with insufficient PV output, the system automatically switches to grid power supplementation. Users can set the grid to charge batteries during off-peak electricity hours, while batteries discharge during peak hours to take advantage of peak-valley price differences and cut power costs.

🔄Ⅴ. Four Intelligent Operating Modes

System Topology Diagram

Mode 1: Grid-Tied Self-Generation & Self-Consumption (Grid Power Available)

PV power prioritizes real-time loads, with surplus power stored in batteries. Users may customize settings to stop charging once batteries are full to protect cells, or enable minor surplus power export to the grid. When daytime loads surge and PV output is insufficient, the grid supplements a small amount of power.

Mode 2: Peak-Valley Battery Discharge Mode (Night / Peak Power Hours)

Without sunlight in evening and night, the inverter switches to battery inversion output. The 30kWh storage covers all basic night power consumption. When battery SOC drops below the 20% protection threshold, the system automatically switches to direct grid supply to avoid cell damage from deep discharge.

Mode 3: Off-Grid Emergency Backup Mode (Grid Blackout)

Upon grid power failure, the inverter disconnects the grid-tied circuit within 20ms and enters full off-grid operation. PV and batteries jointly provide continuous power to critical loads such as refrigerators, monitoring cameras, lighting and water pumps, eliminating losses caused by power outages in rural areas and shops.

Mode 4: Off-Peak Grid Charging Mode (Long-Term Rainy Weather)

When PV generation is inadequate in prolonged rainy days, the grid can be set to charge batteries during low-price off-peak hours, with batteries discharging in high-price peak hours to realize peak-valley arbitrage and further lower annual electricity bills.

⚙️Ⅵ. Load Driving Capacity & Endurance of the 11kW + 30kWh System

The inverter provides rated AC output of 11kW and short-term peak output of 22kW. The usable energy storage capacity is around 24kWh (80% safe depth of discharge for batteries). Load capacity is calculated under two operating conditions:

Condition 1: Off-Grid Pure Battery Operation (No PV, Blackout Scenario)

Effective usable battery energy: 24kWh; with 97% inverter efficiency, effective output energy ≈23.28kWh.

• Basic household loads (lighting, refrigerator, router, total 800W): Continuous operation for 29 hours
• Regular household loads (air conditioner + kitchen appliances + lighting, total 4kW): Continuous power supply for 5.8 hours
• Full rated load operation (11kW full capacity): Stable operation for 2.1 hours
• Short-term high-power equipment (water heater, induction cooker, peak 22kW): Only supports 5-second overload startup, not for long-term continuous operation

Condition 2: Coordinated PV & Battery Operation in Daytime

With peak PV generation of 8.19kW plus battery discharge, the system can stably drive 8kW loads throughout the day. It supports non-stop operation of 5-horsepower central air conditioning, full kitchen appliances and shop lighting during daytime. For commercial shops with 6kW equipment running all day, PV power alone sustains operation, and batteries only serve as power buffer backup.

Condition 3: Scenario Adaptation Summary

• Emergency power for villas during blackouts: Maintains basic power for refrigerators, lighting and security monitoring for up to 3 days
• Power failure response for small shops: Supports cash registers, lighting and freezers under 4kW to keep business running for more than 5 hours
• Under normal grid-tied operation, real-time PV generation combined with grid power enables the 11kW rated output to fully meet simultaneous power consumption of all home appliances in single-family villas.

🛡️Ⅶ. Safety Design & Environmental Adaptability

Energy Storage Safety

Lithium iron phosphate cells carry no risk of thermal runaway. The BMS monitors voltage and temperature of every cell in real time and automatically cuts off charge/discharge upon abnormalities. The inverter sets cut-off thresholds for high and low battery voltage.

Inverter Safety

Pure sine wave output compatible with all single-phase household loads. It automatically reduces power or shuts down under overload, short circuit and overheating conditions. Anti-islanding protection during grid connection prevents electric shock hazards during grid maintenance.

Outdoor PV Protection

Double-glass modules feature IP68 junction boxes with wide temperature resistance, waterproofing and anti-aging performance. DC-side lightning arresters defend against induced lightning strikes.

Environmental Adaptability

The whole set of equipment operates between -20℃ and 60℃, adapting to high-temperature summers in southern China and cold winters in northern regions.

💰Ⅷ. Benefit Analysis & Applicable Scenarios

1. Brief Benefit Calculation

The system generates 41kWh daily. After annual adjustment for sunshine fluctuations, the total annual power generation reaches approximately 13,900kWh. 30kWh of stored energy is used for self-consumption every night, enabling over 10,000kWh of clean energy self-consumption per year. Combined with tiered residential electricity prices and peak-valley commercial shop tariffs, users save substantial electricity fees every year. PV modules come with a 30-year warranty, batteries offer stable service for over 10 years, and the full system lifecycle spans 20 years. Only simple routine inspection and maintenance are required in later stages, delivering long-term significant energy-saving returns.

2. Applicable Scenarios

✅ Rural single-family self-built houses: Solve frequent blackouts and high electricity costs in remote areas

✅ High-end private villas: Guarantee 24-hour power supply for household appliances, swimming pool water pumps and security monitoring

✅ Street-side small shops & convenience stores: Avoid goods deterioration and business suspension caused by power cuts, and reduce peak-hour electricity expenses

✅Ⅸ. Solution Summary

This single-phase integrated system combining 8.19kW PV and 30.72kWh energy storage adopts a scientific string design of 7 modules per string in two parallel branches. The 368.9V open-circuit voltage per string fully falls within the MPPT operating range of the 11kW inverter, achieving excellent electrical matching between all devices.

 

Stable daily power generation of 41kWh and daily energy storage of 30kWh precisely match daily power demand of self-built houses, villas and small shops. The system integrates multiple functions including grid-tied self-consumption, peak-valley arbitrage and emergency backup power for blackouts. The DC-coupled architecture is concise and reliable; wall-mounted energy storage saves indoor space; multi-channel MPPT reduces power loss from shading. With simple maintenance and high safety performance, it is a mature, cost-effective and practical integrated PV energy storage solution for single-phase residential applications.