Three-phase power, on the other hand, is a type of polyphase power that uses three alternating current waveforms that are 120 degrees out of phase with each other. It is commonly used in industrial and commercial applications where the demand for electrical power is high. Three-phase power is also more efficient than one-phase power because it allows for a more balanced load distribution.

In summary, one-phase power is a single AC waveform that flows through a single conductor, while three-phase power is a type of polyphase power that uses three AC waveforms that are 120 degrees out of phase with each other.

2.2 Energy Storage Battery (LiFePO4 VS Lead-Acid Battery)

The battery is recommended to use lithium batteries. Lithium batteries are made of lithium metal or lithium alloy as the negative electrode material and use non-aqueous electrolyte solutions. They have many advantages such as high energy, long service life, and light weight. They are widely used in energy storage power systems such as hydraulic, thermal, wind, and solar power stations etc..

Self Discharge Comparison Between LiFePO4 & LA Battery

Data source:  Litime laboratory

Temperature Tolerance Comparison Between LiFePO4 & LA Battery

Data source:  Litime laboratory

LFP Example Products:

LFP-100: LiTime 12V 100Ah LiFePO4 Lithium Battery

LFP-50: LiTime 12V 50Ah LiFePO4 Lithium Battery

Learn more about LiFePO4 vs Lead Acid Battery

2.3 Working Modes

Mode 1: Load Consumption Priority: PV--Battery--Grid

1. The electricity generated by photovoltaics is given priority to the load, and the excess electricity is stored in the battery, and the excess electricity is sold to the grid; when the PV is insufficient, the battery is discharged for use by the load.

2. When the power grid fails, the load at the grid-connected output end cannot work; but the load at the off-grid output end can work normally, powered by PV and battery.

Mode 2: Economy Mode Settings

Note: The power grid in general mode will not charge the battery. If it is set to economic mode, you can set the time period for battery charging and discharging.

The main function of the economic mode is to shave peaks and fill valleys. It can use the power of the grid to charge the battery during the evening valley and use it for the load during the daytime peak. This mode can reduce the difference between peaks and valleys, thereby saving electricity costs.

Part 3: How to Configure the Battery Capacity

The load should be considered in the selection of the battery, whether it is used every day or for backup; if the battery capacity is too large, there will be waste, and if the stored electricity is used up, the battery will not be fully charged.

So, in the household energy storage scenario, how to select the best battery capacity solution in the fastest and most direct way?

At present, most households use energy storage as a way to adjust the utilization of grid power supply, which we habitually call grid-connected energy storage. For grid-connected energy storage, the main purposes can generally be divided into three categories: photovoltaic self-use (higher electricity costs or no subsidies), peak and valley electricity prices, and backup power (grid instability or important loads).

1. Increase the Self-Use Rate of Photovoltaics

The main purpose of this scenario is to install a photovoltaic energy storage system to reduce electricity bills when the electricity price is high or the photovoltaic grid-connected subsidy is low (no subsidy), so that the remaining power of the photovoltaic system except for daytime use can be stored and stored at night use.

 We divide household electricity consumption into daytime electricity consumption (periods of high photovoltaic power generation) and nighttime electricity consumption (periods of low or no photovoltaic power generation). According to the above purpose, the ideal state should be that the electricity generated by photovoltaics can meet the electricity consumption during the day, and after storage, it can just meet the electricity consumption at night.

That is, the effective capacity of the battery should be approximately equal to the photovoltaic power generation minus the daytime power consumption. But this is only an ideal state. In order to avoid redundancy of battery capacity (to avoid being exhausted at night), we also need to ensure that the effective power of the battery does not exceed the power consumption at night.

This requires us to have a more accurate grasp of the law of household electricity consumption, and to be familiar with the rules for setting the priority level of power supply in the energy storage system.

A family is equipped with a 5kW photovoltaic system, and the daily power generation is about 17.5kWh. The average daily electricity consumption of a household is about 20kWh, of which the average daily electricity consumption is 5kWh during the day and 15kWh at night. Then, the effective power of the battery should be approximately equal to 17.5-5=12.5kWh, and this also meets the condition of not exceeding the nighttime power consumption (12.5kWh≤15kWh). Therefore, the best available battery for this family is 12.5kWh.

Litime 48V 100AH Lithium Solar Battery is your best choice. For this family, you need at least 3 of this battery.

【Grade A LiFePO4 Cells】UL-certificated grade A LiFePO4 Cells deliver a higher energy density, more stable performance, and greater power.

【3-4 Times Higher Energy Density】The upgraded metal case delivers better heat dissipation and wear-resistance performance than a regular ABS case. LiTime 48V 100Ah LiFePO4 lithium batteries are the perfect drop-in replacement for your old lead-acid or AGM batteries. Less weight with a higher 133Wh/L energy density, the LiTime 48V 100Ah batteries carry 3 times the density than those of lead-acid batteries in the same dimension. With 4000-15000 life cycles and a minimum 10-year lifespan, the LiTime battery is your ideal choice to improve the off-grid living experience.

【10 Days Nonstop Power Supply】LiTime 48V 100Ah LiFePO4 lithium battery can power your home for up to 10 days without using any utility power (Ensure the demand of min. electricity per day is 0.5kWh), allowing you to avoid grid outages. The 100A BMS and 4800W output enables you to power air conditioners, dryers, and more heavy-duty appliances at the same time with ease. Support up to 4 batteries connected in parallel for higher power (Max. in 4P for 19.2kW).

2. Cut Peaks and Fill Valleys to Reduce Electricity Bills

The main purpose of this scenario is to charge the battery during the low electricity price during the day and discharge the battery during the peak electricity price at night, thereby reducing the overall electricity bill.

We divide household electricity consumption into daytime electricity consumption (low electricity price period) and nighttime electricity consumption (peak electricity price period). In this scenario, the ideal state is "to use the remaining power after the photovoltaic power supply to the load and the grid to charge the battery during the day, and the battery power is just enough to be used at night (when the electricity price peaks)".

That is, the effective capacity of the battery is approximately equal to the electricity consumption of the family at night. However, the battery capacity calculated based on the nighttime power consumption is only a maximum demand value.

In the case of battery costs, it is generally necessary to comprehensively consider the three levels of photovoltaic system capacity, battery investment, and electricity price savings to determine an optimal ratio. At the same time, it must be satisfied that the battery discharge time is not longer than the nighttime power consumption.

A family with a 5kW photovoltaic system installed has an average daily electricity consumption of about 20kWh, and at night (assuming that the electricity price peak and valley period is 17:00-22:00 for a total of 5 hours) electricity consumption is 15kWh. Assuming that according to the calculation, the effective capacity of the battery covers 2/3 of the family's nighttime electricity consumption, which is the best investment income point.

Then, the effective power of the battery should be approximately equal to 15*2/3=10kWh. At this time, the battery is about 10kWh/5kW=2h, which is less than or equal to 5h of nighttime power consumption. Therefore, the best available battery for this family is 10kWh.

3. As ABackup Power Source in Areas with Unstable Power Grids

When the energy storage system is used as a backup power source, it is mainly used in areas with unstable power grids or situations with important loads. For example, the basic lighting, refrigerators, desktop computers, etc. of the family; the data room of the commercial place, the important equipment of the industrial place, the lighting and ventilation equipment of the breeding place, etc.

When designing the battery capacity with backup power as the main purpose, the main consideration is that the battery can supply the power required by the important load alone when the battery is off-grid for the longest time (the longest expected power outage time), including the need to consider the case of no PV at night .

In this scenario, the battery capacity is relatively easy to calculate. You only need to list all important loads and calculate the power consumption of all loads during the longest power outage to determine the battery capacity initially.

Taking an important commercial place as an example, the important load is 10 cabinets in the data center, and the power consumption of each cabinet is 3kW. The expected maximum outage time is about 4 hours. According to calculations, the effective battery capacity of this project should be 10*3kW*4h=120kWh. Therefore, the effective power of the battery for this industrial and commercial project is best to be equipped with 120kWh.

The above three situations are the most common requirements for installing grid-connected energy storage systems, and there are rules to follow when selecting battery capacity. However, in practical applications, there may be a situation where two or more requirements are superimposed, which requires us to analyze in detail according to the requirements, and finally sort out the best matching capacity of the battery.

In addition, what we mentioned in the above analysis is the effective power of the battery, but the actual selection of the battery also needs to consider the impact load of the load, the DOD (depth of discharge) of the battery, the loss of system efficiency, the performance of the energy storage device, and the expected return on investment. And many other situations.

Therefore, when choosing battery capacity, it is necessary to consider the power of the whole family or usage scenarios as an overall system, and it is also particularly important to choose the best equipment and system integration suppliers.

FAQS about Home Energy Storage

A storage battery has the ability to function even in the absence of PV panels, but this is only possible if an alternative charging method is available.

If your backup battery for your home or your portable power station has the capability to charge through solar power, you can add solar panels at a later point. These power stations can typically be purchased on their own or as a package deal that includes photovoltaic (PV) panels. Additionally, you can use different types of panels for various scenarios by combining rigid PV panels on your rooftop with portable panels for outdoor activities. All of these panels can be linked to the same battery due to the universal design.

Conclusion

A home backup battery is a worthwhile investment for any homeowner who wants to ensure they have reliable power during a blackout. With the benefits of saving money, reducing your carbon footprint, and providing a reliable power source, it's no wonder why home backup batteries are becoming more popular.

This article has introduced several ways to prepare your own power storage system. Hope it would help you.

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