energy storage
Comparable Power by Brandon Schuler
The Solar Energy Industry Association (SEIA) expect utility-scale solar capacity to double over the next couple of years. As solar energy becomes more widely used, owners are looking for affordable energy storage technologies. Utility-scale battery storage systems hold promise to enable greater penetration of variable renewable energy into the grid by storing the excess generation and by firming the renewable energy output. Compared to other technologies, batteries provide a relatively inexpensive energy storage system that offers modularization, rapid and long-term response, flexible installation, and short construction cycles. Utility-Scale- Solar-Plus-Storage Battery Technology Lithium-ion batteries The most prevalent type of utility-scale solar-plus-storage technology is Lithium-ion batteries. The two types used most commonly are Lithium Manganese Oxide (LMRNMC) and Lithium Iron Phosphate (LiFePO4). Lithium-Manganese-Cobalt-Oxide batteries currently dominate the utility-scale storage market, but Lithium-IronPhosphate batteries are on the rise. Lithium Iron Phosphate batteries are named after the organic compound used as the cathode material, along with a graphitic Carbon electrode with a metallic backing as the anode. These offer a cost-effective solution for storage durations between 30 minutes and 4 hours, flexibility in design, range of voltages, power ratings, and energy requirements. Drawbacks include smaller cell voltage levels and more cells per system, resulting in more advanced string monitoring. Also, due to a shorter life span, they require frequent replacement.
Vanadium Redox (VRB) batteries Vanadium Redox batteries are relatively new to the solar segment. They employ Vanadium ions in different oxidation states to store chemical potential energy. The VRB battery exploits the ability of Vanadium to exist in a solution in four different oxidation states, using this property to make a battery that has just one electroactive element instead of two. While VRB technology has lots of advantages – they provide longer-term storage, deliver power up to 15 hours, offer greater flexibility and applicability, and can be recharged many times – these storage systems do not scale well; for expansions, a new system may need to be installed.
Zinc-Hybrid batteries Zink-Hybrid batteries are a promising technology for utility-scale storage systems. In these batteries, a porous anode is formed by a mass of Zinc particles and then saturated with an electrolyte during discharge. Hydroxyl ions formed at the cathode by an Oxygen reaction move into the Zinc paste to create Zincate, releasing electrons that travel to the cathode. They offer up to four-to-six hours discharge with flexibility to go to a higher power, as well as longer run-times and greater fire safety than other technologies.
Lead Acid Valve Regulated VRLA & Vented Lead Acid VLA Batteries Lead Acid batteries offer a dependable and inexpensive solution, provide greater flexibility, and meet longer power demands than other technologies. Both VRLA and VLA batteries utilize a grid-like structure suspended in an acidic electrolyte solution. VRLA batteries are sealed and include Absorbed Glass Matt and jellified electrolyte. While referred to as sealed, they do have a pressure relief valve for safety. They can be mounted in any orientation and require less maintenance than VLA batteries. VRL batteries include lead-alloy substrates bathed in a reactive electrolyte solution. A vent allows the escape of evaporating electrolytes, which is a by-product of the reaction between Hydrogen and Oxygen. Consequently, they require regular replenishing of the suspension fluid and routine maintenance.
Nickel-Cadmium or -Iron Batteries Nickel-Cadmium (NiCd) batteries stand up to extreme temperatures and deep discharge situations. Nichole Iron batteries (NiFE) are specifically considered for use in warmer climates, where low temperatures are not a problem and high discharge rates are rare due to regular charging by photovoltaic modules.
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JULY• AUGUST2021 /// www.nacleanenergy.com
Ni-based battery cells usually consist of a Nickel Oxyhydroxide cathode, a separator between the electrodes, and an alkaline electrolyte (usually Potassium Hydroxide), whereas the anode consists of different minerals depending on the Nickel-based battery cell type. NiFE batteries are robust, tolerant of abuse, have a wide operating temperature range, good charge properties, low maintenance requirements, and a long life even if under-maintained. However, they contain a toxic heavy metal element known for the "memory effect", low specific energy, poor charge retention, and high manufacturing cost.
Sodium-Sulfur Batteries Sodium-sulfur batteries are a type of molten-salt battery constructed from liquid sodium and sulfur, composed of molten Sodium anodes, molten Sulfur cathodes, and Sodium+-conducting ceramic electrolytes. Sodium-Sulfur batteries have a high energy density, high efficiency of charge/discharge, and long cycle life, and are fabricated from inexpensive materials, offering a cost-efficient option. A known drawback is that the connections within the sealed battery module can corrode. Issues usually require battery module replacement.
