4 types of photovoltaic energy storage systems. Do you know them all? 1 article amazing makes it clear!

4 types of photovoltaic energy storage systems. Do you know them all? According to different application scenarios, solar photovoltaic energy storage power generation systems are divided into four types: photovoltaic off-grid power generation systems, grid-connected off-grid energy storage systems, photovoltaic grid-connected energy storage systems, and microgrid energy storage systems.

Since the Energy Bureau issued a new policy on May 31, distributed photovoltaics have only arranged a subsidy scale of about 10G. Before June 1, the installation scale of distributed photovoltaics nationwide had exceeded 10GW. Therefore, after June 2018, distributed photovoltaics may no longer have national subsidies.

If there is no subsidy, the income of projects fully connected to the grid, projects with a small proportion of self-use, and areas with low electricity prices will drop significantly and have no investment value. The investment income of pure photovoltaic projects has declined, so everyone has turned their attention to photovoltaic energy storage, hoping to make breakthroughs in this field and increase new income.

Photovoltaic energy storage is different from grid-connected power generation. It is necessary to add batteries and battery charging and discharging devices. Although the initial cost will increase by 20-40%, the scope of the application is much wider.

The difference between photovoltaics and solar energy is also very big, photovoltaics refers to the technology of directly converting light energy into electrical energy through the photoelectric effect, while solar energy refers to all technologies that use solar energy in a broad sense, including photovoltaics, solar thermal, etc. According to different application scenarios, solar photovoltaic energy storage power generation systems are divided into four types: off-grid power generation systems, off-grid energy storage systems, grid-connected energy storage systems, and multi-energy hybrid microgrid systems.

Photovoltaic off-grid power generation system

The photovoltaic off-grid power generation system operates independently without relying on the power grid and is used in remote mountainous areas, powerless areas, islands, communication base stations, street lights, and other application places. The system consists of a photovoltaic array, a solar controller, an inverter, a battery pack, a load, etc.

The photovoltaic array converts solar energy into electrical energy in the presence of light, and supplies power to the load through a solar control inverter, while charging the battery pack; when there is no light, the battery supplies power to the AC load through the inverter.

Photovoltaic off-grid power generation system is specially used for places in areas without power grids or areas with frequent power outages. It is a rigid demand. The off-grid system does not rely on the power grid. It relies on the working mode of “storing while using” or “storing first and using later”. It is a “helping in need”.

For families in areas without power grid or areas with frequent power outages, the off-grid system is very practical. The cost of photovoltaic off-grid electricity is about 1.0-1.5 yuan, which is much higher than the grid-connected system, but it is more economical and environmentally friendly than the cost of fuel generator electricity of 1.5-2.0 yuan.

Off-grid energy storage system

Off-grid photovoltaic power generation system is widely used in places where there are frequent power outages, or photovoltaic self-generation and self-use cannot be connected to the grid, the self-use electricity price is much more expensive than the grid electricity price, and the peak electricity price is much more expensive than the trough electricity price.

The system consists of a photovoltaic array composed of solar cell modules, solar off-grid integrated machine, battery group, load, etc. The photovoltaic array converts solar energy into electrical energy when there is light, supplies power to the load through the solar control inverter, and charges the battery pack at the same time; when there is no light, the battery supplies power to the solar control inverter and then supplies power to the AC load.

Advances in photovoltaic energy storage systems are making renewable energy more accessible
Advances in photovoltaic energy storage systems are making renewable energy more accessible

Compared with the grid-connected power generation system, the off-grid system adds a charge and discharge controller and a battery, and the system cost increases by about 30%, but the application range is wider. First, it can be set to output at rated power when the electricity price is peak, reducing electricity expenses. The application of solar cells not only plays a key role in the photovoltaic array but also reflects its importance in the charging process of the battery, ensuring the stable operation of the system when there is insufficient light.

Second, it can charge in the valley section of electricity price and discharge in the peak section, making money by using the peak-valley price difference; third, when the power grid is out of power, the photovoltaic system continues to work as a backup power source, the inverter can be switched to off-grid working mode, and the photovoltaic and battery can supply power to the load through the inverter.

Photovoltaic grid-connected energy storage system

The grid-connected energy storage photovoltaic power generation system can store excess power generation and increase the proportion of self-generation and self-use. It is used in places where the surplus of photovoltaic self-generation and self-use cannot be connected to the grid, the self-use electricity price is much more expensive than the grid electricity price, and the peak electricity price is much more expensive than the flat electricity price.

The system consists of a photovoltaic array composed of solar cell components, a solar controller, a battery pack, a grid-connected inverter, a current detection device, and a load. When the solar power is less than the load power, the system is powered by solar energy and the grid together. When the solar power is greater than the load power, part of the solar energy is used to power the load, and part is stored through the controller.

In some countries and regions, a photovoltaic system was installed before, and then the photovoltaic subsidy was canceled. A grid-connected energy storage system can be installed to make photovoltaic power generation completely self-generated and self-used. The grid-connected energy storage machine is compatible with inverters from various manufacturers, and the original system can be left unchanged.

When the current sensor detects that there is current flowing to the grid, the grid-connected energy storage machine starts working and stores the excess electricity in the battery. If the battery is also full, the electric water heater can be turned on. When the household load increases at night, the battery can be controlled to supply power to the load through the inverter.

Microgrid energy storage system

The microgrid system consists of a solar cell array, a grid-connected inverter, a PCS bidirectional converter, an intelligent switching switch, a battery pack, a generator, and a load.

The photovoltaic array composed of monocrystalline silicon solar cells converts solar energy into electrical energy when there is light, supplies power to the load through the inverter, and charges the battery pack through the PCS bidirectional converter; when there is no light, the battery supplies power to the load through the PCS bidirectional converter.

Microgrids can fully and effectively tap the potential of distributed clean energy, reduce unfavorable factors such as small capacity, unstable power generation, and low reliability of independent power supply, ensure the safe operation of the power grid, and are a beneficial supplement to large power grids.

Microgrids can promote the upgrading of traditional industries and play a huge role from the perspective of economy and environmental protection. Experts say that microgrids are flexible in application and can range from several kilowatts to tens of megawatts. They can be developed in factories, mines, hospitals, schools, or even in buildings.

The main advantages of microgrid systems over pure off-grid systems

  1. Wider application range. Off-grid systems can only be used without the large grid, while microgrid systems include all applications of off-grid systems and grid-connected systems, with multiple working modes
  2. Flexible system configuration. Grid-connected inverters can be selected as single or multiple units for free combination according to the actual situation of customers. String inverters or centralized inverters can be chosen, and even inverters from different manufacturers can be selected. The power of grid-connected inverters and PCS converters can be equal or different.
  3. High system efficiency. The photovoltaic power generation of the microgrid system can be directly used for the load nearby through the grid-connected inverter. The actual efficiency is as high as 96%. The bidirectional converter mainly plays a role in voltage stabilization.
  4. Strong load-carrying capacity. The grid-connected inverter and bidirectional converter of the microgrid system can supply power to the load at the same time. When the lighting conditions are good, the load-carrying capacity can be greatly increased.
Photovoltaic energy storage systems convert sunlight into electricity and store it for later use
Photovoltaic energy storage systems convert sunlight into electricity and store it for later use