Is There A Necessary Connection Between Energy Storage And Photovoltaic Systems?

Is there an inherent connection between energy storage and photovoltaic (PV) systems?

The surge in energy storage this year is undeniable. With the expansion of traditional solar power generation becoming increasingly limited, all parties are striving to find new development directions, and energy storage has almost inevitably been thrust into the spotlight.

Energy storage is a general term. Specifically, it encompasses many technological directions and branches, making it impossible to participate in every single one. For those transitioning from PV to energy storage, many are most concerned with how to perfectly integrate existing PV systems or applications with energy storage systems. So, is energy storage necessarily inseparable from PV systems? We can briefly analyze this based on several application methods of implemented PV-energy storage integration projects:

PV System Self-Provided Energy Storage: Self-provided energy storage is commonly seen in small and medium-sized enterprises with high-quality rooftops, large electricity demand, and stable production. Traditional PV systems often adopted a "self-consumption, surplus power to the grid" model, aiming to offset or reduce grid power consumption through solar power generation. This achieved considerable returns through the construction of rooftop distributed PV power stations.

Some large electricity consumers, in addition to paying for electricity based on actual metering, also bear the cost of transformer capacity and demand charges during peak electricity consumption months. In such cases, adding/expanding energy storage systems to existing photovoltaic (PV) power plants, or incorporating energy storage components into new power plants, can further reduce the company's electricity expenses.

The high-quality 380V/50Hz electricity generated by the PV system serves as the energy source for the power storage PCS (Power Storage Unit), participating in the charging and discharging of the batteries in the energy storage system. Simultaneously, high-precision anti-reverse current devices can be added to the system to maximize self-consumption and self-storage of PV energy.

Adding/expanding energy storage systems to power plants, or incorporating energy storage components into new power plants, can further reduce the company's electricity expenses.

DC-coupled energy storage system: PV modules are directly connected to the energy storage PCS, also known as an integrated grid-connected/off-grid system. The biggest advantage is that the integrated photovoltaic (PV) and energy storage system can simultaneously connect both PV modules and battery banks to the grid without requiring additional control equipment. It also has a backup power function, meaning that even if the PV system fails or the mains power is disconnected, the PV-energy storage system can still ensure the load continues to operate normally according to its pre-set output mode. With this function, in addition to peak shaving and energy time-shifting applications, it can also provide power to many areas with power shortages or no power.

Mandatory Energy Storage Allocation for PV Systems Over the past decade, the PV grid connection capacity in various regions has been continuously increasing, and the power distribution system is becoming increasingly saturated. Power departments are imposing increasingly stringent requirements on the input of PV renewable energy, and many regions have even urgently suspended PV registration. Under these circumstances, projects that have already started, are nearing completion, or are about to be launched must continue. Various regions have explored many beneficial approaches, one of which is mandating a certain proportion of energy storage capacity allocated to PV systems. For example, power departments in several prefecture-level cities in Hebei Province require that newly built PV systems must be equipped with 10% to 15% energy storage capacity, and the charging time must not be less than 2 hours; otherwise, grid connection will not be accepted. This means that for a 1MW photovoltaic project, about 15% of the module capacity needs to be connected to the energy storage system, i.e., 150KW/300KWh, in order to alleviate the pressure on the power distribution network.