Photovoltaic Energy Storage Systems: Pioneering Green Energy Solutions for Homes

With the global focus on renewable energy and environmental preservation, household photovoltaic energy storage systems are emerging as a cutting-edge solution for sustainable energy consumption.

Principle of Photovoltaic Energy Storage Systems:

These systems operate through two main processes:

1. Photovoltaic Power Generation: Photovoltaic panels utilize the photoelectric effect of semiconductors to convert sunlight into electricity. When sunlight hits the panels, semiconductor materials stimulate electrons, generating direct current (DC) energy. An inverter then converts this DC into alternating current (AC), which can be used by households or fed back into the grid.
2. Energy Storage: During charging, the generated DC energy is transmitted to an energy storage device, typically a battery pack, through the inverter. The battery pack stores this energy for later use when demand exceeds the current photovoltaic power generation.

Types of Household Photovoltaic Energy Storage:

Hybrid Home PV + Energy Storage System:

• System Composition: Includes photovoltaic modules, lithium batteries, hybrid inverters, intelligent meters, current transformers, and grid-connected/off-grid loads.
• Working Principle: Enables direct charging of batteries from photovoltaic modules through DC-DC conversion and bidirectional DC-AC conversion for charging and discharging. During standard grid operation, the system can supply power from photovoltaic panels and the grid. In case of grid failure, it seamlessly switches to energy storage mode, providing uninterrupted power.
• Features: Offers a cost-effective transformation of grid-connected photovoltaic systems into energy storage systems. Provides reliable power backup during grid outages. Compatible with photovoltaic systems from various manufacturers.

Household photovoltaic energy storage systems represent a paradigm shift towards sustainable energy consumption, offering homeowners a reliable, eco-friendly, and cost-effective energy solution for the future.

Currently, there are two main types of home energy storage systems: grid-connected and off-grid systems.

Grid-connected Home Energy Storage System

Comprising five key components – solar array, grid-connected inverter, BMS management system, battery pack, and AC load – this system operates in a hybrid manner, drawing power from both photovoltaic and energy storage systems. In standard conditions, the photovoltaic grid-connected system and mains supply power to the load. During power outages, the energy storage system and photovoltaic grid-connected system combine to provide power. Grid-connected systems operate in three modes: mode 1 for energy storage and surplus electricity online, mode 2 for energy storage and power consumption for users, and mode 3 where PV provides partial energy storage.

Off-grid Home Energy Storage System

This system operates independently of the grid, requiring no electrical connection. Off-grid systems work in three modes: mode 1 for energy storage and user electricity on sunny days, mode 2 for providing electricity with both photovoltaic and energy storage batteries on cloudy days, and mode 3 where energy storage batteries provide electricity during evenings and rainy days.

Whether grid-connected or off-grid, both systems rely on inverters as essential components, acting as the brain and heart of the system.

Different Configurations of Home PV + Energy Storage Systems

Coupled Home PV + Energy Storage System (AC Retrofit PV + Energy Storage System):

• System Composition: Combines a photovoltaic power supply system with a battery power supply system. Includes a photovoltaic array, grid-connected inverter, battery pack, and bidirectional inverter.
• Working Principle: Photovoltaic DC power is converted to AC by the grid-connected inverter. Excess power is then converted back to DC and stored in the battery by the AC-coupled energy storage inverter, consolidating energy at the AC end.
• Features: Fully compatible with the power grid, simple installation, and expandability. Compatible with both grid-connected and independent generator sets.

Off-grid Home PV + Energy Storage System:

• System Composition: Comprises photovoltaic modules, lithium batteries, off-grid energy storage inverters, loads, and diesel generators.
• Working Principle: Operates independently of the grid, converting solar energy into electricity via photovoltaic modules and charging the battery directly. The off-grid energy storage inverter converts battery DC to AC for load usage when needed.
• Features: Ideal for remote areas or regions with unreliable power grids. Offers system independence and ensures stable and reliable power supply.

Independent Photovoltaic Energy Storage System:

• System Composition: Includes solar panels, battery packs, charge/discharge controllers, and inverters. Operates entirely independent of the public grid.
• Working Principle: Photovoltaic panels convert solar energy into DC power, managed by the controller for battery charging. The inverter converts battery DC to AC for home/device use. Excess power is stored in the battery.
• Features: Grid independence, suitable for remote or unstable grid areas. Highly reliable and environmentally friendly, utilizing clean solar energy without pollution or noise.

Summer Energy Storage System: Utilizing Seasonal Energy Variability

• System Composition: Similar to standalone photovoltaic systems, with a focus on energy storage capacity and efficiency to address seasonal electricity demand changes.
• How it Works: During summer, excess solar energy is stored in batteries. In winter or low-light periods, stored energy is used to meet electricity demand.
• Features: Seasonal energy storage strategy, requiring efficient technologies and high-capacity batteries for winter or low-light usage. Enhances sustainability and energy efficiency.

Off-Grid Energy Storage System: Flexible Energy Solution

• System Composition: Includes solar modules, off-grid integrated machine, and batteries.
• How it Works: Operates in grid-connected mode, utilizing photovoltaic power generation and grid electricity interchangeably. In off-grid mode, relies solely on solar and battery storage.
• Features: Offers flexibility, reliability during grid failures, and efficiency through effective energy storage management.

Various Applications of Household Photovoltaic Energy Storage Systems

• Residential Applications: Rooftop solar panels with energy storage ensure uninterrupted household electricity supply.
• Rural & Remote Areas: Provides reliable power supply where grid coverage is inadequate or unstable.
• Transportation & Communication: Powers electric vehicle charging stations, highway service areas, and communication base stations.
• Public Facilities & Landscape: Powers parks, squares, road lighting, enhancing green energy usage.
• Island & Marine Environments: Ideal for areas with limited grid access, ensuring reliable power supply.
• Commercial & Industrial: Enables self-contained power supply for large buildings, reducing energy costs.

Specific Practical Scenarios:

• Individual Homes & Villas: Meets daily electricity needs and ensures stability during outages.
• Remote & Off-Grid Areas: Provides reliable electricity in areas with inadequate grid access.
• Backup Power Supply: Ensures uninterrupted operation of critical equipment during emergencies.
• Self-Sufficient Communities: Reduces dependence on traditional power grids for sustainable development.
• Outdoor Activities & Emergencies: Portable power supply for camping, emergency power during disasters.
• Electric Vehicle Charging: Utilizes solar energy for charging, promoting green transportation.

Future Prospects:

• Wide Application Scenarios: From residential to commercial, with potential for further expansion.
• Efficiency & Environmental Protection: Promotes green energy usage and sustainability.
• Role in Future Energy Sector: Integral to the shift towards cleaner, more efficient energy solutions.

Household photovoltaic energy storage systems offer versatile solutions for various energy needs, ensuring stability, efficiency, and environmental friendliness. With advancing technology and cost reductions, their applications will continue to grow, contributing significantly to the future of green energy.