Residential energy storage systems are becoming increasingly popular with residential solar users today. According to a recent survey of more than 1,500 U.S. households by solar power developer SunPower, about 40 percent of Americans expressed concern about frequent power outages. Among the respondents who have installed solar power generation facilities, 70% of the respondents indicated that they plan to install battery energy storage systems. But it turns out that a variety of factors can affect the life of a residential battery storage system.
In addition to providing backup power in the event of a power outage, many battery storage systems allow for intelligent scheduling of power in and out, which is to maximize the value of residential solar power systems. Also, some battery energy storage systems are optimized for integration into EV charging facilities.
Although the installed capacity of deploying energy storage systems has steadily climbed, its supporting deployment rate is still low. According to data released by Lawrence Berkeley National Laboratory (LBL), in 2020, 8.1% of residential solar systems in the United States will be equipped with battery storage systems.
There are many options for residential battery energy storage systems. But in the U.S., two players dominate the residential battery storage space. According to the Lawrence Berkeley National Laboratory (LBL) survey, LG Chem and Tesla account for more than 90% of the residential energy storage market in the United States, of which Tesla has more than 60% of the market share.
The Tesla PowerWall battery storage system has a limited warranty that claims to be free from defects for 10 years after installation. It also guarantees an initial capacity of 13.5kWh for the PowerWall battery storage system and will guarantee its storage capacity according to a degradation schedule.
LG Chem said its energy storage system will maintain more than 60% of its energy storage capacity (9.8 kWh) for 10 years. Batteries must operate between -10°C and 45°C to maintain warranty coverage.
Residential solar installer Sunrun said the batteries typically last five to 15 years. This means that during the 20- to 30-year life cycle of a solar power facility, battery storage systems will likely need to be replaced.
Battery life is primarily determined by usage cycles. As LG Chem and Tesla's product warranties attest, reaching the 60% or 70% capacity threshold is guaranteed for a certain charge cycle.
According to the Faraday Institute, there are two usage scenarios that lead to battery degradation: overcharging and trickle charging. Overcharging is the act of injecting current and fully charging the battery. Doing so can cause the battery to overheat and possibly catch fire.
Trickle charging refers to the process of continuously charging the battery to 100%. The battery capacity will inevitably be lost during this process, and this process will increase the internal temperature, which will reduce the capacity and lifespan.
Another cause of degradation over time, according to the Faraday Institute, is the loss of lithium ions from the electrolyte in the battery. Side effects in the battery trap available free lithium, gradually reducing capacity.
While low temperatures can stop lithium-ion batteries from working, they don't actually degrade the battery or shorten its useful life. According to the Faraday Institute, the overall life of the battery will be reduced at high temperatures. This is because the electrolyte between the electrodes decomposes at high temperatures, causing the battery to lose the ability to flow lithium ions. This will reduce the amount of lithium ions the electrode can accept into its structure, depleting the lithium-ion battery capacity.
The National Renewable Energy Laboratory (NREL) recommends that home users install batteries in a cool, dry location, preferably a garage, to minimize the impact of a fire. Batteries and their surrounding components should have adequate compartments for cooling, and regular maintenance checks help ensure optimal operation.
The National Renewable Energy Laboratory (NREL) said that repeated deep discharges of batteries should be avoided as much as possible, because the more discharges, the shorter the lifespan. If the residential battery storage system discharges a lot every day, it will be time to add more battery packs.
Batteries connected in series should maintain the same capacity, although the battery pack may show a total capacity of 24V, there may be different voltages between cells, which is not good for protecting the long-term operation of the battery energy storage system. Additionally, it is recommended to set the correct voltage set points for the charger and charge controller as determined by the battery manufacturer.
The National Renewable Energy Laboratory (NREL) said operators should check frequently. Things to check include leaks (accumulating outside the battery) and voltage consistency.