GRID ENERGY STORAGE MARKET MOMENTUM CONTINUES
The momentum for grid storage technologies is building. This article discusses technologies under development and attempts to make some predictions about which of these technologies might affect the residential and commercial energy markets in the short term. Chris Martell, Principal Engineer
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he grid energy storage market is buzzing and many new technologies are being thrust from the research and development realm into the commercial space. The question of which technology is going to be the big winner for the energy storage revolution is a discussion mired in speculation and clouded with preconceptions. However, it may just be possible to make some educated guesses if we read the market road signs and consider each technology independently. The technologies presented below are some of the more prevalent grid energy storage products that are currently commercially available in one form or another.
virtually the same structure, except that lithium-polymer batteries have a porous gelled electrolyte instead of a porous separator. The polymer offers slightly higher energy densities but is more expensive to produce. Some lithium-ion chemistries are: lithium iron phosphate; lithium nickel cobalt aluminium; lithium cobalt oxide; lithium manganese oxide; lithium nickel manganese cobalt oxide; lithium titanate. These chemistries have different attributes relating to safety, cost, energy, power and cycle life. Owing to their safety attributes, the two most commonly used chemistries are lithium iron phosphate and lithium nickel cobalt aluminium.
Valve-regulated lead-acid (VRLA) batteries
Nickel-based batteries are stable, robust and generally have some of the lowest costs per cycle of any battery type available. Nickel-cadmium was the most popular nickel-based chemistry from the 1950s, but more recently, it has been widely displaced by nickel-metal hydride due to the toxicity of cadmium. Nickel-metal hydride batteries are extensively available for use in consumer products and have been used in many hybrid electric vehicle (HEV) applications. Nickel-based batteries are safer and cheaper than other types of batteries with higher specific energies, such as lithium-ion batteries, but the research and development focus given to technologies such as lithium-ion may quickly change this. As well as having a lower specific energy than other technologies, nickel-based batteries have a high self-discharge rate and a tendency to ‘remember’ cycle depth unless fully discharged at regular intervals.
Unlike flooded lead-acid batteries, valve-regulated lead-acid (VRLA) batteries generally do not need to have their electrolyte refilled as it is suspended in a medium and the batteries themselves are sealed. Absorbed glass matt (AGM), gel and new types of lead-based batteries, such as the Ultrabattery by Ecoult, are examples of VRLA batteries. VRLA batteries are a mature technology, having been used in the telecommunications industry and rural stand-alone systems for decades. Their well-established position and low maintenance costs have made them the preferred choice for grid energy storage at all levels.
Lithium-ion and lithium-ion polymer batteries Lithium-ion batteries have been commercially available for over 20 years. Rapid improvements in battery chemistry and production quality have led to the universal acceptance of lithium-ion batteries for mobile applications. Lithium-ion and lithium-ion polymer (also known as just lithium-polymer) batteries have very similar chemistries and
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Nickel-based batteries
Flow (hybrid or redox) batteries Flow batteries are increasingly being used in the grid energy storage market. The two most popular types of flow batteries are the vanadium
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