Best battery chemistry for “Behind-the-Meter” residential energy storage
Let’s discuss the differences in battery chemistries currently available, with a focus on the attributes with regards to residential “behind-the-meter” applications
At SPI 2017, many companies were offering residential battery storage products. The conversations between attendees and booth attendants quickly revealed a lack of knowledge in the market, on both sides of the trade show booth.
Here are the main types of battery chemistries, and what each has to offer the homeowner. It is not an exhaustive list, but the most relevant for home use.
Flooded Lead Acid has been the staple of storage for many years.
The flooded portion is H2SO4 (sulfuric acid).
It is a good option for certain applications, but not the mainstream residential market. Compared to more recent chemistries, flooded lead-acid batteries require more maintenance, more space in the home and will degrade quickly with use.
They also have lower discharge potential and are not good at storing energy for a length of time, which is essential for blackout protection use. The majority of the home market is seeking a ‘set it and forget it’ product, which lead-acid is not.
Lithium Ion (Lithium Cobalt Dioxide (LiCoO2)) is the battery chemistry that most of the residential market is familiar with.
Commercialized in the early 1990’s, these are used in nearly all of our portable electronic devices; lithium-ion batteries are seemingly everywhere. Lithium-ion provides a very favorable weight-to-storage capacity, meaning they are light relative to the amount of energy they can store.
One key benefit of lithium-ion is price, with production enjoying economies of scale that will continue to bring down the cost per kWh stored. They are virtually zero maintenance, hold their charge well and can have a life over 10 years, depending on how deeply and often they are discharged.
Lithium-Ion batteries come with drawbacks.
Most concerning is they give off heat when discharged, and in rare cases suffer from thermal runaway, a chemical condition where the chemistry inside the battery creates more heat than can be dissipated, and heat production spins out of control, resulting in a fire.
Another safety concern is their combustion if punctured.
A concerning drawback is that the battery will lose its potential to hold power if frequently discharged, and the deeper the discharge, the greater the capacity loss over time. This nuance is evident in product warranties, which reveal an expected loss of storage capacity after 5-years.