5 Types of Solar PV Energy Storage Systems: Off-Grid, Grid-Tied, Hybrid, and Microgrid Solutions

According to different application scenarios, solar photovoltaic (PV) power generation systems can be classified into five main types: off-grid PV systems, grid-connected PV systems, hybrid on/off-grid energy storage systems, grid-connected energy storage systems, and multi-energy hybrid microgrid systems.

1. Off-Grid Solar PV System

An off-grid solar PV system, also known as an independent PV system, is a standalone power generation system that operates without connection to the utility grid. It mainly consists of solar PV modules, a charge controller, and batteries. If it needs to supply power to AC loads, an inverter is also required.

Standalone PV systems are widely used in remote areas, including village electrification systems, residential solar power systems, communication base station power supplies, cathodic protection systems, solar street lights, and other independent PV applications equipped with battery storage.

2. Grid-Connected Solar PV System

A grid-connected solar PV system mainly consists of solar PV modules, grid-tied inverters, combiner boxes, and grid connection cabinets. The DC electricity generated by the solar modules is converted into AC electricity through the grid-tied inverter and directly fed into the public utility grid.

Grid-connected PV systems are generally divided into two categories:

1) Distributed Solar PV System

A distributed PV system, also known as distributed generation or distributed energy supply, refers to a small-scale solar power generation system installed at the user's site or near the point of electricity consumption to meet specific energy needs.

Typical applications include residential rooftops, commercial buildings, factories, and industrial facilities.

2) Utility-Scale Solar PV System

A utility-scale PV system is characterized by transmitting the generated electricity directly to the power grid, where it is managed and distributed by the utility company.

These solar power plants usually require large investments, longer construction periods, and significant land areas.

3. Hybrid On/Off-Grid Energy Storage System

A hybrid on/off-grid energy storage system mainly consists of solar PV modules, a hybrid inverter (on-grid/off-grid inverter), and battery storage.

It is widely used in areas with frequent power outages, where excess solar power cannot be exported to the grid, where self-consumption electricity prices are higher than feed-in tariffs, or where peak electricity prices are significantly higher than off-peak rates.

This system can provide backup power during grid failures while maximizing solar energy utilization.

4. Grid-Connected Energy Storage System

A grid-connected energy storage system mainly consists of solar PV modules, a grid-connected energy storage inverter, batteries, a grid-tied inverter, and current monitoring devices.

When solar power generation is lower than the load demand, the load is supplied by both solar energy and the utility grid.

When solar power generation exceeds the load demand, part of the solar energy is used to power the loads, while the surplus energy is stored in batteries through the energy management system.

5. Microgrid System

A microgrid system mainly consists of solar PV modules, grid-connected inverters, PCS (Power Conversion System), ATS (Automatic Transfer Switch), battery storage systems, generators, and other energy sources.

It integrates multiple types of distributed energy resources to achieve energy complementarity and improve overall energy efficiency.

During daylight hours, solar PV modules generate electricity to supply the loads through the inverter while simultaneously charging the batteries through the PCS.

When there is no sunlight or solar generation is insufficient, the battery system supplies power to the loads through the PCS, ensuring continuous and reliable energy supply.