Photovoltaic system is mainly divided into five modes: “self-use, surplus power to the Internet”, “self-use, surplus power not to the Internet”, “full grid-connected”, “off-grid” and “parallel / off-grid”.
Spontaneous and self-use, and the surplus electricity is connected to the Internet
This photovoltaic system mode is one of the most common mode, and the general distributed photovoltaic power generation system mainly adopts this mode.
The power generated by the photovoltaic system can first meet its own load use, and the excess power can be sold to the grid company to avoid waste; if the power generated by the photovoltaic system is insufficient for load use, it will be supplemented by the grid power supply. However, the access of this mode needs to negotiate the relevant power sales agreement with the power grid company and take into account the interests of both sides. The grid company will install two-way smart meters to measure the power generation of the photovoltaic power station and the electricity consumption of the user respectively, and pay or collect the electricity fee according to the policy and negotiated price.
The biggest disadvantage of this operation mode is that its income model cannot be fixed, and the proportion of self-use and the proportion of surplus power to the Internet are always changing. The evaluation value of the financing and sale of power stations may be discounted than the actual output, and the capital even cannot obtain a reasonable asset value because of the worry about the future operating conditions of users.
Spontaneous self-use, surplus electricity is not on the Internet
The remarkable feature of the self-use grid connection mode is “no connected to the Internet”. The access point of this mode is at the bottom end of the grid company meter, which is the private side of the complete property right demarcation point. Theoretical power grid company will not interfere in the system access, but this pattern requires photovoltaic power generation (to the grid), so must have a set of countercurrent device, when photovoltaic power station over load power consumption, the upstream device must be signal feedback to the inverter, inverter will be down the capacity according to the load situation, to meet the load demand is not transmitted to the power grid, achieve the function of upstream photovoltaic system.
The photovoltaic system mode is generally applied to the user side power load is larger, and power load continues, a year few production or half production, or even during the holiday, the users power load size is enough to give the vast majority of electricity photovoltaic system, as far as possible the photovoltaic power used out, will not cause waste.
Full grid connection
This grid-connected mode is to connect the AC output of the photovoltaic system directly to the low voltage side or high voltage side of the grid, that is, the grid side of the property rights boundary. The electricity generated by the system in this way is directly sold to the grid company, and the sales price usually adopts the local average on-grid price, while the users electricity price keeps the original price unchanged, the so-called “two lines of income and expenditure, each calculates its own account”.
This model is also popular in photovoltaic applications; because of its simple financial model, which is relatively reliable.
Off-grid mode
This off-grid mode is also known as independent photovoltaic power station, which is a power generation system operating independently of power grid, and therefore, it is very suitable for remote ungrid areas, isolated islands, fishing boats, outdoor breeding bases, and as emergency power generation equipment in frequent blackout areas.
However, this power generation system must be equipped with batteries, and it occupies a relatively high cost of the power generation system. Moreover, due to the service life of energy storage battery, it needs to be maintained and replaced, which increases the use cost. Therefore, in terms of economy, it is difficult to get a large range of promotion and use, so it is not recommended to use electricity in convenient places.
For households in ungrid areas or frequent power failure areas, it has a strong practicality. Especially simply to solve the lighting problem during a power failure. Therefore, off-grid power generation systems are specifically used for use in ungrid areas or frequent blackout areas.
Photovoltaic street lights, lawn lights and other photovoltaic products, also belong to the photovoltaic off-grid system.
And / off-grid mode
The application scenario of this parallel / off-grid mode is frequent power failure, or the self-use electricity price is much more expensive than the feed-in electricity price, and the peak electricity price is much more expensive than the trough electricity price;
It sets the output at the peak price to reduce the electricity price. Second, it can be charged in the price valley and the peak discharge to make the peak-valley price difference. During the normal power supply to the grid, the system operates according to the normal grid-connected power system, and the surplus power can be stored or sold to the grid, the system continues to work as the backup power supply, and the battery can supply power to the important load through the inverter without causing waste.
And / off-grid mode and off-grid mode both require batteries, and the initial investment cost is relatively large.
The access of this mode needs to negotiate the relevant power sales agreement with the power grid company and take into account the interests of both sides.
In general, most will adopt the grid connection mode; which one can be selected according to the specific requirements of the project.
