Incorporating energy storage into a solar batteryisn’t as easy as just picking batteries off the shelf. Certain chemistries work better in certain environments, and storage capabilities are influenced by the solar application.
The U.S. Energy Information Administration (EIA) released a trends report on the U.S. storage market in May 2018. The report found that lithium-ion batteries represented over 80% of the installed power and energy capacity of large-scale energy storage applications. Nickel- and sodium-based batteries represented around 10% while lead-acid and other chemistries rounded out large-scale battery representation.
Within small-scale battery installations (where commercial and industrial installs form up 90% of capacity), EIA was unable to pinpoint specific chemistry data, but it are often assumed that lithium-based batteries still reign supreme. Lead-acid batteries are popular within off-grid installations for many years , but lithium-ion’s longer cycle life, lighter weight and decreased maintenance have made it the well-liked choice for large-scale, EV and residential applications.
But lithium-ion isn’t the only—or best—choice out there for batteries utilized in solar-plus-storage installations. Here’s a quick rundown of the common storage technologies utilized in the industry, and which chemistries some popular brand names use.
Lithium-based energy storage systems are overwhelmingly the foremost common storage technology used within the solar market. These batteries are characterized by the transfer of lithium ions between electrodes during charge and discharge reactions. Additional materials, like cobalt, nickel and manganese, are inserted into the battery cells and may affect the battery’s performance, voltage and safety. Lithium-ion batteries are costlier than other chemistries, mostly due to their need for battery management systems to control voltage and temperature. the advantages of lithium-ion, though, include long cycle life, high charge and discharge efficiency, lighter weight and no maintenance (lithium-ion batteries are solid and don’t require refills).
Lithium Cobalt Oxide (LCO) — LCO batteries are very stable and small, making them a popular choice for cell phones and laptops. Any battery with cobalt has a higher risk of thermal runaway and fire danger, which is why some phones and hoverboards were catching fire a few years back. Their short life spans and limited load capabilities do not make them a great choice for larger energy storage applications, but LCO batteries are a good introduction point to lithium-based storage.
Lithium Manganese Oxide (LMO) — LMO batteries have fast-charging properties and increased thermal stability since there’s no cobalt. These batteries are often utilized in medical devices and power tools, although they’re entering the C&I market because they’re a safer alternative to cobalt batteries and may be optimized for longevity and high energy capacity.
LMO example: Sharp (now NantEnergy) large-scale SmartStorage system
Lithium Nickel Manganese Cobalt Oxide (NMC) — NMC batteries are a well-liked chemistry within the lithium-ion category. the mixture of nickel and manganese provides these batteries with high specific energy and stability. Their use of cobalt, though, increases the danger of thermal runaway.
NMC examples: LG Chem batteries, Tesla Powerwall
Lithium Nickel Cobalt alumina (NCA) — NCA batteries are a comparatively new chemistry and act similarly to NMC-based systems. The addition of aluminum provides the batteries with more stability.
NCA example: TrinaBESS range of systems
Lithium Iron Phosphate (LFP) — LFP batteries use iron phosphate to extend safety and thermal abilities while also experiencing an extended cycle life. Since they generate little heat, these batteries don’t require ventilation or cooling, in order that they are often installed in additional unique, indoor applications.
LFP examples: SimpliPhi Power’s line of batteries, sonnen’s residential storage systems
Nickel-based batteries, mainly nickel-cadmium (NiCd), are simple units without complex management systems. they’re rugged and reliable. NiCd especially has been utilized in large-scale energy storage due to its forgiving performance in extreme temperatures. These batteries are fitted to demanding applications where reliable backup power is important and maintenance can’t be regularly performed, but they are doing require ventilation.
NiCd examples: Saft’s Uptimax battery, EnerSys PowerSafe batteries
Sodium-based batteries use salt—sometimes saltwater—to produce nontoxic, long-duration power. Salt-based cells are often completely drained to zero charge without damaging the system. Lithium-ion batteries, as compared , always require some charge or they’re going to fail. Sodium batteries aren’t flammable or explosive (as long as other materials aren’t added to the chemistry) and may function during a wide temperature range.
Na example: Aquion Energy
Lead-acid chemistry is one among the oldest sorts of energy storage and is widely utilized in vehicles. Lead-acid batteries are known for being dependable and cheap . These batteries use a lead-based grid submerged in an acidic electrolyte which will need replenishing for long, successful life. Lead-acid batteries are heavy due to their materials. they need a limited cycle life and are inefficient when it involves charge and discharge in comparison to other chemistries. But they’re cheap to manufacture and are reliable if the owner knows the way to charge and discharge properly.
Flooded — Flooded lead-acid batteries must be flooded with a liquid. they’re not resilient to wreck and need significant care and maintenance. Flooded batteries got to be refilled regularly because the electrolytes evaporate during charging. These batteries must be housed in an enclosure with enough ventilation to stay off-gassing levels from reaching a dangerous point.
Flooded examples: Trojan Battery’s Solar Premium line, Rolls’ Flooded 2 YS series, U.S. Battery’s RE series
Valve Regulated Lead-Acid (VRLA) — VRLA batteries are often “sealed” and use valves to manage off-gassing. They require little to no maintenance in comparison to flooded lead-acid batteries and may therefore be handled a touch more aggressively or installed in hard-to-reach applications. VRLA are often further separated into two categories: absorbed glass mat (AGM) and gel. AGM batteries hold the electrolyte in its glass mats and use merely enough liquid to stay the grid wet. Gel batteries use a thick silica-based gel as its electrolyte base. AGM batteries perform better in colder temperatures, while gel batteries work better in warmer temperatures when there’s less chance for the thick paste to freeze.
AGM examples: Crown Battery’s Crown1, U.S. Battery’s Sealed AGM line
Gel examples: MK Battery’s Deka Solar Gel Monobloc batteries, Trojan Battery’s Deep Cycle Gel series
Flow batteries use two chemical components dissolved in liquids separated by a membrane to supply a charge. Both chemical liquids circulate in their own space while the flow of electrical current happens through the membrane. Flow batteries work like fuel cells, because the liquid energy sources are the weather creating the electricity. they will be instantly recharged by replacing the electrolyte liquids and store additional electrolytes externally, usually in tanks that are then pumped into the system. Flow batteries excel in long-duration storage applications and need little maintenance. rather than adding more battery units to a storage system to extend capacity, flow battery systems just need more electrolyte liquid.
Redox flow batteries (RFB) — RFB systems use a chemical reduction and oxidation reaction to store energy within the liquid electrolyte solution. During discharge, an electron is released through an oxidation reaction and accepted via a discount reaction on the opposite side of the membrane. Specific RFB types include iron flow batteries (IFB) and vanadium redox flow batteries (VRB).
RFB example: ESS Energy Warehouse
Hybrid flow batteries — Hybrid flow batteries use RFB qualities but with a solid metal additive. Specifically, zinc bromine (ZNBR) flow batteries have zinc bromide salt dissolved within the electrolyte liquid.
ZNBR example: Primus Power EnergyPod2