Featuring uniqueness, Each Energy All-In-One Inverter Model APHS-M10 perfectly defines residential energy storage systems
With the continuation of the Russo-Ukrainian War and the energy crisis in Asian, African and Latin American countries, the demand for residential energy storage system has blossomed intensively and rises steadily. There has been heated debate as to whether to use low-voltage energy storage system or high-voltage energy storage system for residential families with single phase scenario applications.
Advantages and disadvantages of single-phase low-voltage energy storage system
The 3-12KW single-phase low-voltage inverters currently occupy a dominant position in countries like Asia, Africa and Latin America where single-phase households are the mainstay. Countries such as South Africa, Lebanon, and Pakistan are all adopting single-phase energy storage solutions.
Taking the South African market as an example, since the power outage in South Africa has exceeded 200 days in the year of 2022, energy storage inverters need to achieve the following functions in order to meet the needs of the South African market:
Off-grid parallel function, and UPS-level switching between parallel and off-grid
Example: Families tend to install a small energy storage system initially, and as the house load demand is growing, the second and third systems would then be installed, which requires the off-grid parallel function. When the national grid fails, it can achieve the function of UPS-level off-grid switching.
Diesel generator interface
When the sunlight is insufficient and the battery storage power is insufficient, the diesel generator can be automatically started through the dry contact to meet household use or to charge the battery.
Parallel off-grid with 100% load power
Taking the 8KW single-phase energy storage inverter as an example, can the inverter reach the rated charging and discharging power of 8KW per hour?
UPS Level off-grid overload capability
For some inductive loads, the instantaneous power will be overloaded when starting. Would the Inverter be able to achieve an overloading capacity for tens of seconds, so that the high instantaneous power of the inductive load can be smoothly transited to the rated power. Failure to do so will cause the relay inside the inverter to trip, and the power supply will be stopped and then restart repeatedly.
To achieve the above four functions, the low-voltage energy storage system needs to charge and discharge the battery with a large current under the rated battery voltage of 48V.
The low-voltage system composed of 48V lithium batteries developed from the early 48V colloidal batteries, which is designed with the Mos tube scheme, and the cost is much lower than the current high-voltage energy storage system with the relay and high-voltage box scheme. At present, it covers more than 80% of the market share for single-phase household storage applications, and it is the mainstream product in the single-phase household storage market. However, the larger power single-phase low-voltage household storage inverter also has some defects that cannot be avoided.
Taking a 10KW low-voltage energy storage inverter with a 48V low-voltage battery as an example, in order to achieve the rated charging and discharging power of 10KW per hour and the instantaneous overload capacity (calculation based on 10% overload), the rated and maximum charging and discharging currents need to reach 208A and 229A respectively. With a nominal voltage of 48V for the charging and discharging of the battery with high current, there will be the following four hidden dangers or defects:
Installation is cumbersome and difficult
Take Australia’s mandatory safety regulations on cable selection AS3008 as an example (The safety regulations in Europe, America, Australia and New Zealand are the same in terms of cable Selection, while other countries are similar). According to the fact that the cables carrying DC power must be covered with UV-resistant PVC pipes, a tripping DC switch must be installed between the energy storage inverter and the battery. The type of switch must be equal to or less than the maximum current that the cable can carry; The minimum size of the cable between the inverter and the battery is 120mm2, and the current of the breakable switch is between 229A and 241A.
Installers first need to fit in a 120mm2 thick cable between the inverter and the battery, and then install a PVC tube on the outside of the cable (it is very difficult to install the needed conduit for a long distance), and install a cable with a specification between 229A and 241A in the middle of the cable off switch. With the strict safety regulations imposed, such complex installation procedures even scare away many licensed electricians.
The high charging and discharging current of 208A to 229A leads to a serious temperature rise of the inverter, and the box and heat sink are above 100 degrees Celsius for a long time, which leads to the load reduction of the inverter or even shutdown due to overheating. The multi-angle fan will then be used for cooling down the temperature, which in turn makes the noise of the inverter louder.
The internal temperature of the inverter is kept at 80-100 degrees for a long time, which greatly reduces the service life of the components of the Inverter. In the context where the price of the energy storage inverter starts to decrease and the competition for 10-year warranty for Hybrid Inverter is fierce, the risk for warranty cost and customer service for the 10-year warranty period is enormous.
The Bus voltage of the single-phase inverter is between 350-400V. During the working condition in the daytime, the inverter performs DC to DC dropping on the direct current input from the PV close to the Bus voltage to 48V; under the working condition at night, When the inverter discharges the battery, it boosts the DC power stored in the battery from DC to DC to within the bus voltage range of the inverter. During the DC to DC Voltage boosting and dropping process, there will be severe the power loss, resulting in low efficiency of the entire system at 90%.
Analysis of advantages and disadvantages of high voltage energy storage systems
The high-voltage groups, represented by a leading high-voltage residential energy storage company in China, mainly promote single-phase low-voltage storage systems from 3KW and 5KW before 2021, matching Samsung’s lithium batteries. However, it was announced in 2021 that the production of 48V low-voltage single-phase storage system will be discontinued, and it will be replaced by a single-phase high-voltage energy storage inverter matching its own brand battery (single phase 3.2KWH). Australia, Italy, Spain and some other countries are representatives mainly promoting single-phase and three-phase high-voltage energy storage systems.
The battery cells for the high-voltage energy storage system generally use small cells under 50AH. The rated and maximum charge and discharge currents of most high-voltage single-phase energy storage inverters in China are between 25A and 30A, respectively.
However, the high-voltage energy storage system adopts the scheme of double the number of small cells + multi-wire harnesses and welding points + relays + high-voltage boxes, and the design of each package of 3-5 kilowatt-hours increases the structural cost. Therefore, the cost of high-voltage batteries is about 50% higher than that of 48V low-voltage batteries. Single-phase high-voltage energy storage systems currently account for 20% of the market share of single-phase energy storage systems. In some developed countries in Europe and Australia, they can be accepted by a small number of high-end customers. In countries dominated by single phase appliances, single-phase high-voltage energy storage systems have almost no market share.
Each Energy All-In-One Inverter APHS-M10 series
Looking at the advantages and disadvantages of the above low-voltage and high-voltage single-phase energy storage systems, Each Energy has specifically designed and innovatively developed the APHS-M10 series of single-phase energy storage systems. It not only combines the advantages of the above low-voltage and high-voltage Inverters and batteries, but also solves the defects of the same.
The M10 Battery in this series of products uses a large battery cell design of 100AH. The traditional two low-voltage 48V100AH batteries are changed from parallel connection to series connection of 96V 100AH. Passive current sharing + secondary protection greatly improves the stability of the entire system. Using the low-cost Mos tube solution, the cost of the M10 battery with 10 kilowatt-hours is basically similar to that of a 48V200AH low-voltage battery. It perfectly solves the shortcomings of the high cost of the current high-voltage battery systems.
In order to achieve 100% full load charging and discharging, the APHS medium and high voltage inverter can automatically adapt the corresponding current to charge and discharge according to battery models. When the APHS is matching with an M10 battery, the rated and maximum charge and discharge currents are 50A and 60A respectively; when the APHS is matching with a 50AH battery, the rated and maximum charge and discharge currents are 25A and 30A, respectively. The lower current perfectly solves the four defects of the above low-voltage system.
APHS-M10 series also has the following features:
Our Inverter can accept up to 200% of the PV input power, for which 100% of the power is transferring from the DC to AC and another 100% are for the battery charging simultaneously.
200% overloading capacity which can last for 60 seconds, solving the problem of instantaneous power when the inductive load is too large.
Off-grid parallel function, UPS level and off-grid switching.
The thickness of APHS-M10 is 17.8 cm, which takes up very little space.