Lithium-ion batteries are more suitable for home energy storage systems
With the popularity of residential energy storage systems, more and more consumers are choosing to use lithium batteries, but most residential solar users have traditionally used lead-acid batteries that are completely off-grid. Compared to lead-acid batteries, lithium-ion batteries have an advantage over lead-acid batteries in energy storage applications, and with falling costs, lithium-ion batteries are rapidly becoming the batteries of choice for many power applications.
Historically, the majority of residential solar users deploying battery storage systems have used lead-acid batteries, especially those that are completely off-grid, but over the past few years, that has begun to change as residential energy storage systems increasingly use lithium batteries. So, which is better for energy storage systems, lithium-ion or lead-acid? Here is an overview of the pros and cons of both.
Application of lead-acid batteries
Lead-acid batteries have been used as backup power for residential solar power facilities since the 1970s. While they are similar to conventional car batteries, batteries used in residential energy storage systems are called deep-cycle batteries because they discharge and charge more times than most car batteries.
Lead-acid batteries have traditionally cost less than lithium-ion batteries, making them more attractive to residential users. However, their working life is much shorter than that of lithium-ion batteries.
Lead-acid batteries have a lower operating life than lithium-ion batteries. While some lead-acid batteries can be charged and discharged up to 1,000 times, lithium-ion batteries can be charged and discharged between 1,000 and 4,000 times.
Most lead-acid batteries have a lifespan of about five years and come with warranties. As a result, residential users will have to replace lead-acid batteries several times over the lifetime of a solar power facility.
The energy storage efficiency of lead-acid batteries is lower than that of other energy storage technologies such as lithium-ion batteries. Because they are less efficient, they also cannot charge or discharge as quickly as lithium-ion battery energy storage systems.
Lead-acid batteries have a low discharge capacity, which means that consuming too much energy can cause their ability to store energy to deteriorate rapidly. Research by the National Renewable Energy Laboratory (NREL) found that releasing 50 percent of the energy in a lead-acid battery allowed it to complete 1,800 charges and discharges before its storage capacity dropped significantly. If it is discharged to 80 per cent capacity, it can only withstand 600 charges and discharges before its capacity drops significantly.
Lead-acid batteries require more storage capacity and space than lithium-ion batteries because they are relatively inefficient at storing energy and cannot be fully discharged. Lead-acid batteries are also much heavier than lithium-ion batteries, which require a stronger stand to hold them, and require more space than a lithium-ion battery pack.
Lead is a toxic heavy metal, and although it is recyclable, it can still be contaminated through improper disposal.
Application of lithium ion battery
Lithium-ion batteries are fast becoming the battery of choice for many power applications, from cordless power tools to laptops and vehicles. A growing number of residential solar power facilities are using lithium-ion battery energy storage systems. But lithium-ion batteries still have some limitations, the first and foremost being their high cost.
Lithium-ion batteries have higher upfront costs than lead-acid batteries. Tesla's Powerwall energy storage system will sell for $5,900 or $6,600 in the U.S. in 2018, including supporting hardware. It is a 14kWh battery system that can deliver up to 7kW at peak demand. The cost does not include installation costs, which typically range from $600 to $2,000.
But the cost of lithium-ion batteries is falling fast. Over the past few years, Lazard has evaluated the costs of various battery storage technologies in its Average Cost Analysis of storage. In its most recent survey report from November 2017, it found that lead-acid battery storage systems with residential solar can cost between $598 and $635 per kilowatt-hour to install. Lithium-ion batteries cost $831 to $1,089 per kilowatt-hour to install.
According to these figures, a 14kWh lead-acid battery costs as little as $8,372, while a lithium-ion battery of the same capacity costs as little as $11,634. But the low cost of lead-acid batteries hides many other costs, such as a shorter working life and higher operating costs.
All in all, lithium-ion batteries have advantages over lead-acid batteries in energy storage applications, and will become more widely used in energy storage systems as costs fall.