According to surveys conducted by research institutions, it is estimated that by 2023, more than 55% of energy storage systems will be deployed with solar power generation facilities. With the expansion and development of the market, its system architecture will become an important consideration for the development of solar + energy storage projects.
According to the latest survey report of the research organization WoodMackenziePower&Renewables, the application of DC-coupled solar + energy storage projects on the grid side (FTM) is becoming more and more common, and it is likely to occupy a dominant position in the residential market. In addition, although the eligibility for the U.S. federal investment tax credit is a factor in the growing share of DC-coupled grid-side solar + energy storage systems, its share is expected to continue to be expected under the gradual reduction of investment tax credits (ITC) in 2021 Continue to grow.
This growth is also due to the new changes brought about by the DC-coupled system architecture, making the DC-coupled solar + energy storage project the grid-side application for the first time and has received more attention. Generally, a customer-side (BTM) DC-coupled system uses a multi-port hybrid inverter associated with battery energy storage systems and solar power assets. Although these inverters are suitable for user-side (BTM) battery energy storage projects, they are not suitable for grid-side (FTM) battery energy storage projects.
The new change in the DC architecture of the grid-side (FTM) battery energy storage project involves an independent DC-DC converter connected to the battery. These new grid-side (FTM) DC-coupled systems generally have lower interconnection costs than AC-coupled systems because they only rely on a single interconnection point. The cost of interconnection will significantly affect the capital expenditure of project developers (depending on the size of the system, interconnection costs can account for 20% to 35% of the system’s balance cost stack).
This single-point interconnection in the DC coupling system also allows large-scale solar power generation facilities to store excess power generation in the battery energy storage system, making it economically feasible, thereby supporting the excess solar energy for cost-effective time shifting.
In view of the elimination of the AC acquisition system, the reduction of system balance requirements, and the ease of interconnection, the current installation cost of the DC coupling system is 3% to 10% lower than that of the AC coupling system, depending on the scale of the solar + energy storage project and the battery The duration of the discharge.
However, as the scale of the system becomes larger, the DC system begins to lose its cost advantage. The scale of solar + energy storage projects increases, and the economies of scale achieved through power conversion and other hardware components will not translate into overall system capital expenditures, because solar power generation facilities and battery energy storage systems begin to occupy more costs.
DC-coupled systems are easily eligible for federal investment tax credits. By the end of 2021, the proportion of grid-side (FTM) battery energy storage projects will drop to 10%. However, according to the report, although eligibility for the U.S. federal investment tax credit is a factor in the growing share of the DC-coupled grid-side solar + energy storage system, the investment tax credit (ITC) will gradually decrease in 2021. The share is expected to continue to grow.
Since the current DC system does not allow batteries to be charged from the grid, the AC coupling system will become the default architecture choice for battery installation systems mainly used for grid support applications.
The consumer-side (BTM) battery energy storage market in the commercial and industrial industries is the only area where DC-coupled systems have not grown. WoodMackenzie said the department continues to use AC coupling systems and will continue to do so in the short term. Although it has the advantages of easy installation and low system balance requirements, which makes the DC-coupled architecture very popular in the residential solar + energy storage market, the current multi-port hybrid inverter has some problems, such as single point failure, fixed input voltage, And the loss of flexibility makes it less attractive to the non-residential market of user-side (BTM) battery energy storage systems.
AC-coupled systems are also more suitable than DC-coupled systems for the deployment of future solar power generation facilities or battery energy storage system upgrades, as well as micro-grids that require higher reliability and flexibility.
Post time: Sep-14-2021