1. Completely self-initiated and self-used mode
This model is generally applied when the user's electricity load is large and continuous, and there are few shutdowns or partial shutdowns throughout the year. Alternatively, even during holidays, the user's electricity load is sufficient to absorb most of the electricity generated by the photovoltaic power station.
In such systems, because the low-voltage side is connected to the grid, if the user's electricity consumption cannot be absorbed, it will be fed back to the upper-level grid through the transformer. However, the design of distribution transformers does not allow for backfeeding (short-term backfeeding is permissible, such as during commissioning, but not long-term), and their initial power flow direction is fixed. Therefore, anti-reverse flow devices need to be installed to prevent power backfeeding.
For users who cannot guarantee that their electricity consumption can continuously consume photovoltaic power, or for projects whose production cannot be guaranteed to be continuous, it is recommended not to adopt this grid connection method.
This mode is recommended for photovoltaic power plants with a single unit capacity of less than 500kW and a distribution transformer on the user side, because the additional investment required for voltage boosting accounts for a large proportion of the total investment.
2. Self-consumption and surplus electricity fed into the grid mode
For most users optimistic about distributed generation, the ideal model is to consume the surplus electricity themselves and sell it back to the grid. This allows them to obtain higher electricity prices for self-consumption and sell any unused electricity back to the grid. However, there are many obstacles in practice due to the information asymmetry between photovoltaic industry practitioners and local power grid company personnel. They lack mutual understanding of each other's professional knowledge, which is why this model has become the most difficult part of photovoltaic electricity pricing policies and the State Grid's new policies to understand.
In the self-consumption and surplus power grid-connected model of photovoltaic power generation, users (or "investors") hope that the generated electricity is consumed within their own enterprises as much as possible. If there is any unused electricity, it can be fed into the grid to avoid wasting this photovoltaic power. However, power companies prefer users to have a simple choice: either self-consumption or grid-connected with boosted voltage. This is because self-consumption and surplus power grid-connected ...
The biggest drawback of this operating model is that its revenue model cannot be fixed. The proportion of self-consumption and surplus electricity fed into the grid are constantly changing. When financing or selling the power station, the assessed value may be discounted compared to the actual output. In some cases, investors may not be able to obtain a reasonable asset value because they are worried about the future operating conditions of the electricity users.
3. Fully grid-connected electricity sales model
In the past decade of rapid development of photovoltaic power generation, selling electricity directly to the grid has been the mainstream application of photovoltaics because its financial model is simple and relatively reliable, making it attractive to capital.
This grid connection method is not only suitable for future distributed fixed-price projects, but also a good option is to sell directly to the grid at the desulfurization price (provided that the desulfurization price in the region is not lower than 0.4 yuan). This is still shorter than the payback period of future distributed power stations.
Moreover, we cannot ignore the fact that photovoltaics is a capital-driven industry, belonging to the category of fixed-income, long-term investments. Most companies, in their development phase, are unlikely to hold photovoltaic power plants, even those who currently own some. Therefore, the photovoltaic power plant transfer market has a sufficiently large future potential, and services for both buyers and sellers will become highly sought-after businesses, such as insurance, appraisal, testing, operation and maintenance, and third-party guarantee services.
Ultimately, the choice of which method to use as the grid connection mode for a photovoltaic power station is up to the investors themselves.
