With the increasing attention paid to energy price and energy security at all levels, as well as the increasing maturity of photovoltaic and energy storage technologies, having a stable and secure (independent) energy system in the household unit is not only a guarantee for energy security but also a financial account to be settled. At present, the life of the photovoltaic modules of mainstream photovoltaic power station products is more than 25 years (the power generation efficiency in 25 years is more than 80%). The life of the energy storage part is about 5-10 years due to the different technology and usage conditions, and the life of the main components such as inverters is about 10 years.
The energy storage scheme of a household optical storage power station is mainly divided into the:
Grid-connected energy storage:
For household photovoltaic power generation systems that have been installed before, after the cancellation of photovoltaic subsidies, another grid-connected energy storage system will generally be installed, so that photovoltaic power generation can be completely self-use.
This “external” grid-connected energy storage system can be well-compatible with the inverter of the original system (no need to replace the inverter), and the original system can be unchanged. When the energy storage system detects that there is excess electricity flowing to the power grid, the energy storage system automatically starts to work and stores the excess energy in the energy storage battery. When the energy storage battery is full, the energy storage system can also connect the user’s electric water heater to convert the excess energy into heat and store it. When the photovoltaic power generation system stops working in the evening or the user’s power consumption increases, the energy stored in the energy storage system can be used to power the load.
The grid-connected power station is for areas with stable power grid energy supply, such as most of China and major developed countries in the world, the main purpose of this kind of household power station construction is to exchange long-term low-price energy with less one-time input. In addition to self-use, the excess electricity will be transferred to the power grid. The payback period is generally 4-6 years, which is related to the specific electricity consumption and local electricity price. Due to the energy crisis, the spot price of electricity in major European power markets (Germany, France, and Italy in August 2022) has exceeded 350 euros per megawatt hour, with a payback period of fewer than two years.
Off-grid energy storage:
Suitable for areas where the power grid is relatively unstable, photovoltaic is connected to a solar controller (MPPT controller) with energy storage batteries. Off-grid energy storage does not need to rely on the power grid, nor can it be charged through the power grid. It can only be used in the mode of “storage and use” or “storage before use” as a backup independent energy system, which can realize automatic switching at a millisecond level when the power is off through the built-in UPS (uninterruptible power supply).
Off-grid energy storage:
If the budget is sufficient, it is recommended to directly use an off-grid energy storage scheme, and an off-grid photovoltaic power generation system is widely used in the application of “spontaneous self-use can not spare, self-use electricity price is much more expensive than on-grid electricity price, peak electricity price is much more expensive than trough electricity price” and other applications, is the most advanced and reasonable optical storage mode.
As the number of distributed PV projects increases and the capacity of the grid becomes saturated, many local grids have mandated that new distributed PV facilities be equipped with a certain percentage of energy storage.
Compared with the grid-connected photovoltaic power generation system, the off-grid system combines the advantages of the off-grid system and the grid-connected system, which makes the application range wider and the electricity use more flexible. First, it can be set at the peak of the electricity price with rated power output to reduce the cost of electricity; Second, it can use the valley electricity to charge the energy storage system and use it in the peak hours to gain profits by the peak-valley difference. Third, when the power grid is cut off, the photovoltaic energy storage system can be used as the standby power supply to switch to off-grid mode and continue to work.
As the off-grid energy storage system needs to adjust the price difference through charge and discharge on a daily basis, it is recommended to select an integrated lithium iron phosphate optical storage system that can cycle charge and discharge for more than 10,000 times and has a service life of more than 10 years.
Off-grid energy storage is used as a backup power supply, which does not require daily high frequency charge-discharge switching. It is suitable for matching with a more cost-effective lithium iron phosphate battery cabinet, with a life of more than 4,000 cycles. The off-grid system type power station can ensure the stability of household energy by using the off-grid system as backup energy for the area that the grid infrastructure cannot cover stably. For areas with high electricity prices or the difference between peak and valley electricity prices is relatively large, such as commercial electricity customers in Europe or our country, the integration scheme of optical storage (off-grid system) can be used to save the cost of electricity and earn the price difference on a large scale.
3KW rooftop power station (daily power generation is about 15 degrees)
Using idle roofs to build photovoltaic power stations is the most common form of power station, but also the most cost-effective way. For residential families, the need to consider is to choose the appropriate scheme and technical route, seeking a balance between practicality, beauty, and safety.
The advantages of the grid-connected power station are low one-time construction capital investment, and low technical and system difficulty; The disadvantage is that power generation and self-use time is only concentrated in the daytime, and the grid-connection conditions (requirements) and feed-in price are affected by the policies of the grid service providers in different regions.
Installed capacity: 3KW
Average daily power generation: about 15 degrees
Roof area: about 24 square meters
Number of PV modules: 30
Inverter: 3KW
Installation: bracket + fixture, no impact on the original roof
5KW ceiling power station (daily power generation is about 25 degrees)
It is also a common type to build rooftop photovoltaic power stations on courtyards and terraces. This way can give play to the building materials properties of thin-film photovoltaic products and replace ordinary glass with power-generating glass so that the power station can become not only the space ceiling for shading and rain but also the power station facilities that can generate electricity revenue, which can achieve multiple benefits with one stone. According to the needs of users, the power generation glass part can be customized for light transmittance and color, to meet the personalized needs of owners. For the customers of the closed space of the sunroom, you can choose the hollow light transmission type power generation glass, to achieve thermal insulation and sound insulation.
Installed capacity: 5KW
Average daily power generation: about 25 degrees
Roof area: about 40 square meters
Number of PV modules: 50
Inverter: 5KW
Installation: bracket + fixture, no impact on the original roof
10KW photovoltaic power station + energy storage system
The 10KW photovoltaic power station is composed of 18 550W monocrystalline silicon photovoltaic modules with a daily power generation of about 50 ° C. It is equipped with a 5KW power 10kWh energy storage system, which independently drives 7-10 electrical appliances at the same time.
Installed capacity: 10KW
Average daily power generation: about 50 degrees
Roof area: about 75 square meters
Number of PV modules: 100
Inverter: 10KW
Installation: bracket + fixture, no impact on the original roof
It can be predicted that the integrated development of light storage is the inevitable direction of household energy use. For households that have the conditions to install distributed photovoltaic power generation system (independent property rights are the best, followed by the penthouse), planning and layout of the new energy system independent of the family in advance is not only a green attitude to life but also an efficient investment in the future.
