What’s the types of home energy storage products and development trend of them

Household energy storage is usually used in combination with household photovoltaic, and the installed capacity is experiencing rapid growth. The core of the residential energy storage systems, also known as battery energy storage system, is a rechargeable energy storage battery, which is usually based on lithium ion or lead-acid batteries. This article will introduce the types of home energy storage products and their development trend in detail.

Market analysis of home energy storage products

According to the different coupling modes of photovoltaic and energy storage systems, in household energy storage products there are DC coupling systems and AC coupling systems, which are respectively suitable for the incremental market of newly installed photovoltaic systems and the stock market of installed photovoltaic systems. The incremental market has more space, which is the main driving force for future market growth.

Incremental market

Incremental market refers to the newly installed photovoltaic with energy storage system in target households, which generally uses DC coupled household energy storage products. The advantage of DC coupling is that both photovoltaic and energy storage batteries are converted through hybrid inverters, and no additional photovoltaic grid connected inverter is required. The system integration is higher, installation and after-sales service are more convenient, and intelligent monitoring and control are also convenient.

Stock market

The stock market refers to the target households that have installed PV and need to add energy storage systems, generally using AC coupled energy storage products. The advantage of AC coupling is high safety: in the AC coupling mode, the energy is gathered at the AC terminal, which can be directly supplied to the load or sent to the power grid, or directly charged to the battery through the bidirectional converter.

Home energy storage product system analysis

According to whether the system is connected to the power grid, the household energy storage products system can be divided into grid connected system and off grid system. At present, most regions use the parallel off grid integrated system.

● Photovoltaic and energy storage systems

Photovoltaic and energy storage systems can be connected to the grid, and can purchase power from the grid when the photovoltaic or battery power is insufficient. It is suitable for areas with stable power system and relatively low electricity price.

● Off grid system

Off grid system is suitable for desert, island and other areas without power grid or areas where the power grid is unstable and needs self use. The off grid energy storage converter is usually equipped with a diesel generator interface to supplement power when the battery power supply is insufficient at night.

● Parallel and off grid integrated machine

The parallel and off grid integrated machine has the parallel and off grid switching function or integrates the parallel and off grid modes into one machine, which can be switched into the off grid mode in case of power failure, and is suitable for areas with unstable power systems and frequent power outages.

The core hardware equipment of the household energy storage products system includes batteries and converters. According to the degree of integration of household energy storage products, there are mainly two modes:

● Integrated machine

Some AC coupling and DC coupling energy storage products adopt the split machine mode. The battery system and inverter system are provided by pack manufacturers and inverter manufacturers respectively, and then reach the end users through the channels of integrators, dealers and installers.

● Split machine

The product is an all-in-one machine system including battery and inverter, usually an AC coupling energy storage products. The upstream battery system and inverter, as suppliers, usually adopt the OEM mode. The final energy storage products do not show the supplier’s brand, and the product sales and after-sales are all undertaken by the brand.

The current market of energy storage products is dominated by split machines, but the all-in-one machine is the development trend of the high-end market.

What is the battery type of home energy storage products

According to the voltage of the battery pack, the battery type of home energy storage products can be divided into high-voltage batteries and low-voltage batteries. The industry has shown a trend of switching to high-voltage batteries.

The main purpose is to improve efficiency and simplify system design, but at the same time, it requires higher cell consistency and BMS management capabilities of home energy storage products.

In terms of efficiency, with the same capacity of batteries, the battery current of the high-voltage energy storage products system is small, and the interference to the system is small. The efficiency of the high-voltage energy storage products system is higher; In terms of system design, the circuit topology of the high-voltage hybrid inverter is simpler, smaller, lighter and more reliable.

However, the high-voltage battery is composed of multiple cells in series and parallel. The higher the voltage, the more batteries in series, and the higher the requirement on the consistency of the cells. At the same time, it needs to cooperate with the efficient BMS management system, otherwise it is easy to have failures.

Analysis of companies in the industrial chain of household energy storage products

● Integrator

Only work for brand and all the equipment is purchased.

● Inverter manufacturer

Sell inverter separately or purchase integrated battery/all-in-one machine.

● Battery cell manufacturers

One is to supply battery cells to downstream brands, and the other is to produce battery systems for independent sales or simultaneously purchase inverter modules to complete hardware integration and software design.

The business models of participants in the industrial chain show two trends: first, inverter and cell manufacturers are integrated downward; second, some manufacturers focus on equipment supply. Take a 4.68kw photovoltaic+5.8kw/6kw Votai energy storage system in the UK as an example, the total investment is about 10000 pounds, equivalent to a unit price of 17.61/w. 

Among them, the PV system accounts for 32%, the module is 3.08 RMB/w, and the PV inverter is 2.56 RMB/w. The energy storage system accounts for 35%, and the unit price is 4.97 RMB/wh. Other materials+installation cost 3400 pounds, accounting for 33%.

How will home energy storage products develop in the future

The future development trend of home energy storage products is high capacity battery+hybrid inverter+all-in-one machine.

Battery trend

From the perspective of battery trend, batteries in energy storage products are evolving towards higher capacity. With the increase of residential power consumption, the electric capacity of each household is gradually increased, and some products realize system expansion through modularization.

Because of the penetration of new energy vehicles, the increase in the power of household appliances and the impact of home and office work, the power consumption of each household is increased, and the electrification of home power storage demand is increased.

● The electricity consumption per household has gradually increased

In terms of the regional market, the electricity consumption per household has gradually increased. Taking the German market as an example, the average electrification were 8.8 kwh in 2021, 8.5 kwh in 2020 and 8 kwh in 2019. The increase of electrification in the German market is mainly due to the development of new energy vehicles and the increase of household electricity consumption.

● The modular battery is convenient for expansion

Since the charging capacity and power of a single product are limited, the manufacturer will set that the energy storage products can be flexibly configured through modular combination to meet the needs of different capacity scenarios.

● The battery moves from low voltage to high voltage

The higher voltage battery system in energy storage products can reduce heat generation, improve system efficiency, simplify circuit structure and facilitate system installation. With the improvement of cell manufacturing technology and battery management system control technology, high-voltage battery system has become the industry trend.

Inverter trend

From the perspective of inverter trend, the demand for hybrid inverters suitable for incremental markets and off grid inverters without access to the power grid has increased. On the one hand, the newly added photovoltaic power distribution and storage is sufficient, and the demand for hybrid inverters increases. On the other hand, markets of energy storage products such as the United States and South Africa drive the demand for off grid inverters.

The United States has frequent natural disasters, high power outage risk, and the U.S. power grid is relatively fragile and aging. In order to stabilize the grid, some photovoltaic system power companies do not allow them to access the grid. Therefore, it needs to be installed off the grid and used spontaneously to replace the generator.

Terminal energy storage products trend

From the perspective of the trend of terminal energy storage products, currently, it is mainly split type, that is, the battery and inverter system are used together, and then gradually develop to the all-in-one machine. Previously, battery manufacturers usually provided battery systems, and inverter manufacturers provided hybrid inverters. In channel sales, they matched the batteries and inverters according to their adaptability.

The energy storage products of different brands are cumbersome for installation and after-sales. Therefore, pack manufacturers and inverter manufacturers have started to involve each other. At present, some inverter manufacturers (such as Huawei, Goodwe, etc.) have purchased electric cells to assemble their own packs and integrated batteries and inverters for sale.

Regional market trend

From the perspective of regional market trend, the difference of power grid structure and power market results in slight difference of mainstream products in different regions. The European grid connection mode is the main mode, the United States has many grid connection and off grid modes, and Australia is exploring the virtual power plant mode.

● Europe: There are many grid connection modes

The PV market in Europe has a high penetration rate, and the power grid is relatively stable. The use of grid connected systems can meet the demand. The energy storage system needs to interact with the power grid, so the energy storage products inverter should be grid connected certified to meet the local power grid requirements.

● US: There are many parallel and offline models

The laying of power grids in the United States was concentrated in the last century, and the power grid facilities were relatively old, laying hidden dangers for the power grid transportation capacity and load capacity. The problems of aging equipment and outdated technology were prominent.

According to statistics, American users experienced an average of 3.2 hours of interruption during major events and 1.5 hours of interruption without major events, totaling nearly 5 hours.

● Australia: Exploring virtual power plant mode

Multiple households with photovoltaic energy storage system can accept VPP protocol and power grid dispatching. Households can sell excess electricity; When there is a demand for electricity, purchase electricity through this setting, and then connect to the power grid.