How to configure home energy storage battery and its system？

Since 2022, the demand for home energy storage batteries in the world gradually fire up, as a new market, products and markets are still in the exploration stage, while considering the high cost of home energy storage batteries, how to more efficient and economical use of the home storage system is very important, Wisetree home energy storage experts based on years of experience from different dimensions to analyse and summarize the home energy storage battery systems Configuration design and requirements.

1.The structure of solar home energy storage battery system

Home solar energy storage system mainly consists of solar panels, power grids, inverters, batteries, power equipment, of which the input side of the solar panels only, called off-grid system, solar panels and utility grid input at the same time, called mixed-grid system, if the utility input only, generally as a standby power system.

2.User demand analysis

2.1 First of all, to understand the user's power equipment types, equipment power.

First of all, the user's power equipment to make a list, the maximum power to fill up, and then calculate the total power P0.

P0=P1+P2+P3+.... +Pn

2.2 Understand the number of power equipment that may be used at the same time, and calculate the total power value P1. The purpose of this step is to prepare for the subsequent more reasonable configuration of the inverter.

3. How to choose the inverter?

3.1 Power selection

 According to the results of the analysis of user needs, select the rated power higher than the P0 value of the inverter, if the customer budget is insufficient, then you can reduce the requirements, choose then select the rated power > P1 inverter. The maximum output power of the inverter determines the maximum power of the equipment that the user can use at the same time, so this choice is very critical, if the configuration is small, in actual use, there will be an overload situation, which may lead to overload protection, or burn out the inverter.

3.2 Type selection

 There are high-frequency inverters and industrial frequency inverters, and they have the following differences:

(1) In terms of reliability, the industrial frequency machine is better than the high frequency machine, the industrial frequency machine adopts thyristor (SCR) rectifier, the technology has been very mature after more than half a century of development and innovation, and its resistance to current impact is very strong, due to the SCR belongs to the half-control device, there will not be a straight-through, miscontact and other faults. High-frequency machine using IGBT high-frequency rectifier, although the switching frequency is higher, but IGBT work with a strict voltage, current working area, the impact resistance is lower, so the reliability is lower than the SCR.

      (2), in terms of environmental adaptability, high-frequency machine is better than industrial frequency machine, high-frequency machine is a microprocessor as a processing control centre, the complex hardware analog circuits burned into the microprocessor to the way the software program to control the operation of the UPS, therefore, the volume, weight and so on, there is a significant reduction, the noise is also small, on the space, the environment, the impact is small, so for the reliability of the small and medium-power occasions that do not require a high degree of reliability Commonly used high-frequency machines, such as portable power supplies.

      (3), in the load on the zero-ground voltage requirements, industrial frequency machine is better than high-frequency machine, high-power three-phase high-frequency machine zero line will be introduced into the rectifier, and as the neutral point of the positive and negative bus, this structure inevitably results in high-frequency coupling of rectifiers and inverters in the zero line, lifting the zero-ground voltage, resulting in the load side of the zero-voltage elevated, and it is difficult to meet the IBM, HP and other server manufacturers of the zero-ground voltage of less than 1V demand. In addition, in the utility and generator switching, high-frequency machine often due to the lack of zero line and must be turned to bypass work, in specific working conditions may cause a major failure of the load flash off. Industrial frequency machine because the rectifier does not need the zero line to participate in the work, in the zero line disconnect, the UPS can maintain normal power supply.

      Therefore, in the specific application of home energy storage battery system, the inverter also needs to be optimally configured according to the customer's specific application scenarios and needs.

3.3 Voltage selection

      There are two kinds of inverter systems, low voltage and high voltage, low voltage generally refers to the input voltage system below 48V, high voltage refers to the input voltage of 96V and above, generally single high power output inverter is high voltage system, such as single 10KW power above. If there is a demand for high power output, but the chosen one is a low-voltage system, it is necessary to use parallel mode to provide enough power.

Fourth, home energy storage battery energy configuration

4.1 Battery system

      In the field of household energy storage batteries, the battery types are lead-acid, ternary lithium batteries, lithium iron phosphate batteries, etc. The characteristics of these batteries are as follows:

      (1), lead-acid battery: single voltage 12V, can be freely connected in series and parallel, without BMS management. Advantages are standard, easy to replace; relatively inexpensive; safe, strong adaptability to the environment; disadvantages are relatively short life; pollution of the environment;

      (2), ternary lithium batteries: a single 3.7V, can be combined in series and parallel into the required voltage and capacity, the current 12V and 24V is the main, the need for BMS strict management. Advantages of high energy density, in the field of volume constraints have a greater advantage, the disadvantage is poor security, compared with lithium iron life is shorter.

      (3), lithium iron phosphate battery: a single voltage of 3.2V, can be combined in series and parallel into the required voltage and capacity, the current 24V and 48V is the main, the need for BMS strict management. Advantages are safety, long life, the disadvantage is that compared with the ternary, volume, weight.

      Traditional energy storage are mainly lead-acid, is also the largest amount of ternary lithium batteries are mainly used in portable energy storage systems, lithium iron phosphate batteries are mainly used in household energy storage battery systems and industrial energy storage field.

4.2 Domestic energy storage battery voltage matching

  Household energy storage battery voltage is mainly determined by the inverter, need to be matched with the input voltage of the inverter, such as 48V inverter with 48V battery, 96V inverter with 96V battery, can not be mismatched.

4.3 Home energy storage battery energy configuration

  This is decided by the user's budget, depending on how long the user wants to use under full power, for example, the total power of the user's equipment is P, the time needed to use full power is h, and the conversion efficiency of the inverter is β, then the energy of the battery is Q=P*h/β.

4.4 Output power

Generally it is decided by the design of the home energy storage battery system, which is determined by the discharge multiplier of the battery cell, the maximum current that the system structure can withstand, the maximum current of the BMS, the heat dissipation performance, etc. For example, if a 48V system is designed to have a maximum output current of 100A, then its output power will be 4,800W and so on.

4.5 Functional Requirements

This refers to some additional functions in addition to electrical performance, such as display function, mobile phone APP monitoring function, remote control function, etc., which are optional according to user requirements.

V. PV Module Configuration

5.1 Maximum Allowable Installation Power

This value is determined by the area of open space that the user can use to install solar panels, usually the roof, and this area limits the maximum allowable total power of solar panels installed. If the available area is S square, the area of each solar panel is S1, and the power is Pw then the maximum allowable solar panel power to be installed is P=S/SI*Pw.

5.2 Actual solar panel power

This value is determined by the user at the beginning of the system design, if the user needs to fill the battery time is T, assuming that the effective light time in the local area is t, then the solar panel power P = battery energy/T/t = Q/T/t. P should be less than or equal to the maximum permissible installation power Pw. This value is affected by the budget, the budget is sufficient, then P = Pw

VI. Other accessories

6.1 Mounting Bracket

Mainly refers to the solar panel mounting bracket, which is decided according to the number of solar panels and the installation method.

6.2 Wire

Various connecting wires, determined at the time of system design.

Wisetree New Energy focuses on the research and development, production and sales of lithium iron phosphate home energy storage battery national high-tech enterprises and national standards development unit. With independent R & D team and intellectual property rights to provide 5KWH and 10KWH home energy storage battery as the main product representative.