Converting Residential Solar Power Stations into Energy Storage Systems Solves the Problem of Electricity Time Mismatch!

With the continuous growth of global demand for clean energy, residential solar power stations are playing an increasingly important role in household energy supply. However, traditional residential solar power stations have a significant drawback: intermittent and unstable power generation. Solar power generation relies on sunlight and can only generate electricity during the day when there is sunshine, while household electricity demand is distributed relatively evenly throughout the day, and may even be higher at night. This leads to a time mismatch between the electricity generated by solar power and household electricity demand, resulting in low utilization of solar power for users.

Against this backdrop, converting residential solar power stations into residential energy storage systems has become an effective way to solve the above problems. Residential energy storage systems can store electricity when there is excess solar power and release it during periods of insufficient sunlight or peak electricity demand, achieving efficient utilization of solar power. Moreover, energy storage systems can also be used as emergency power sources, providing necessary power backup for households during grid outages, improving the reliability and stability of household electricity supply.

Before undertaking the conversion, a comprehensive assessment of the existing residential solar power station is necessary. This includes the type, power, lifespan, and power generation efficiency of the PV modules, as well as the performance, capacity, and compatibility of the inverter. Simultaneously, the condition of the power station's wiring, support structures, and other infrastructure must be checked. For example, if the PV modules are old and their power generation efficiency has significantly decreased, partial replacement during the upgrade may be necessary to ensure the overall power generation capacity of the energy storage system.

It's also crucial to fully understand the household's electricity demand, including daily electricity consumption and peak electricity usage times. Different electricity demands will affect the capacity configuration of the energy storage system. Furthermore, it's necessary to pay attention to local policies regarding residential energy storage, such as subsidy policies and grid connection policies. Some regions offer subsidies for residential energy storage systems; understanding these policies can reduce upgrade costs.

Converting a residential PV system to an energy storage system can be divided into two schemes: AC coupling and DC coupling.

1. AC Coupling Solution 

The AC coupling solution retains the original PV inverter. The PV modules convert sunlight into DC power, which is then converted into AC power by the PV inverter to supply the household load and the energy storage inverter. When there is excess photovoltaic energy, the energy storage inverter converts it into DC and stores it in batteries. During periods of insufficient sunlight or peak electricity demand, the energy in the batteries is converted back into AC to supply the load.

2. DC-Coupled Solution

The DC-coupled solution directly replaces the PV inverter with an energy storage inverter. The energy storage inverter converts the DC power generated by the PV string into AC power to supply the load. When there is excess PV energy, the excess energy is directly stored in batteries and supplied to the load during periods of insufficient sunlight or peak electricity demand.

Based on the household's electricity demand and the grid's electricity pricing policy, the energy management strategy of the residential energy storage system is optimized. For example, during off-peak hours and peak PV generation periods, the low-priced electricity from the grid and the excess power from PV can be used to charge the energy storage batteries; during peak hours, priority is given to using the power from both PV and the energy storage batteries to reduce electricity costs.