Home energy storage device

Home energy storage demand is stabilizing, and the trend of all-in-one machines is emerging

Diverse application scenarios and stable household requirements. From the perspective of the whole power system, the application scenarios of energy storage can be divided into three scenarios: power generation side energy storage, transmission, and distribution side energy storage, and power side energy storage. The application of power generation and transmission and distribution side mainly focuses on the power grid. Energy storage is often used for power peak regulation, system frequency modulation, grid connection of renewable energy, grid congestion alleviation, and delay in the expansion and upgrading of transmission and distribution equipment. In the scenario of the power side, the users are generally households, industry and commerce, and public institutions. The energy storage system is mainly used for economic needs such as self-use of electricity, peak-valley price arbitrage, capacity and electricity charge management, and improving the reliability of power supply. According to the statistics of BNEF, the household demand for energy storage applications in the world is basically stable between 20% and 30%, which is much higher than that of the industrial and commercial industries.

Profit model of household energy storage: Cooperate with photovoltaic, improve the proportion of photovoltaic self-use, and arbitrage the peak-valley price difference. Energy storage for household use is generally used in combination with rooftop photovoltaics. Currently, there are three profit models: self-use and surplus online: The FIT price in the early stage of the policy is higher than the price for household electricity, and the rooftop photovoltaic installation is promoted by “benchmark price, full Internet access”. With the increase in household electricity and the gradual decline of FIT subsidy, the price differential has widened, and overseas rooftop PV users have turned to energy storage configurations to achieve a higher proportion of self-use. Peak-valley arbitrage: California, Australia, major European countries, and China all have time-of-use pricing mechanisms. Under this mechanism, the energy storage system charges energy storage through the off-peak period of the power grid at night and discharges during the peak period of the day. The peak-valley price difference is used to save electricity costs. Virtual power plant: Based on the energy software management platform, the distributed energy storage system integrator integrates the distributed energy storage system scattered on the user side, analyzes, controls and optimizes the operation of the energy storage system, and participates in power grid services to obtain application benefits.

Dc coupling is adopted in optical storage systems, which has higher comprehensive efficiency. At present, according to the different degrees of integration, household energy storage systems can be divided into optical storage integrated machines and energy storage integrated machines for different household needs. The optical storage machine, as the name implies, integrates the photovoltaic inverter and the bidirectional converter together and is placed inside to form an integrated system. In the integrated mode, DC coupling mode is adopted in the interior, which is out of the box to realize the integrated solution of “light + energy storage”, which is suitable for the incremental market of simultaneous installation of household photovoltaic and energy storage systems. The energy storage splitter is suitable for the stock market of installed household PV. The internal mode is usually AC coupling, which is easy to connect with the photovoltaic inverter of the original PV system. The efficiency of the DC coupling mode is significantly higher than that of the AC coupling mode in the daytime power generation and the night power consumption mode, and this mode is in line with the power consumption habits of most contemporary households, with the efficiency of about 95% and 90% respectively.

Optical storage machine is highly integrated, effectively reducing the soft cost. NREL data shows that the hardware cost only accounts for less than 50% of the total cost of household energy storage systems. However, due to its highly integrated characteristics, optical storage all-in-ones do not need to install additional photovoltaic inverters. On the one hand, it reduces the hardware cost, on the other hand, it can save one-time equipment investment, simplify installation, save installation costs, and facilitate after-sales maintenance. Effectively reduce the subsequent soft cost. According to our calculation, compared with the split solution, the cost of optical storage all-in-one machine can save about $155 /kwh. According to BNEF’s prediction, the future soft cost reduction will be much lower than that of lithium batteries and inverters. Under the condition that the hardware cost of the all-in-one machine is similar to that of the split machine, the soft cost advantage of the all-in-one machine will be further highlighted in the future.

Richard Maxwell

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