In this series on energy storage, we have been looking at the important factors that consumers must understand when considering various energy storage technologies and the return on their investment. In Parts I & II, we discussed system safety and multi-service assets. (Read Part I here and Part II here.)
A third critical factor affecting the economic viability of battery storage technologies is the ongoing costs for operations and maintenance (O&M).
Aside from the up-front and “all in” costs for an energy storage system, which includes power electronics, top-level controls and auxiliary systems, ongoing operational and maintenance costs have a significant impact on the economics of an energy storage investment.
Lithium-ion battery technologies require a considerable ongoing O&M investment. The battery cells have at best a lifespan of seven to 10 years while at the same time having revenue-grade degradation performance. Compared to the estimated 20-year stable life of a zinc-iron flow battery, lithium-ion cells require replacement up to two times, adding further maintenance costs to the system when you include the price of modules, labor and the requisite hazardous materials handling. Furthermore, the above estimated life of the battery cells doesn’t calculate additional performance degradation due to improper cycling or extreme ambient temperatures which can dramatically shorten the life of lithium-ion cells.
The costs for lithium-ion typically don’t account for the auxiliary subsystems (HVAC and fire suppression) required for safety and operational requirements. These additional components, which wear out over time, are another factor contributing to system failure and increased downtime outside of maintenance for the battery, itself. Even for short-duration, high power applications for which lithium-ion is typically suitable, downtime due to required maintenance or component failure contributes to lost revenue for the end user on top of regular maintenance costs.
Current vanadium and bromine flow battery technologies incur significant O&M costs over their estimated operating life, too. The electrolyte, itself, has proven to have a relatively short life span compared to zinc-iron and requires regular replacement because of degradation. The acid electrolyte of vanadium, for example, is prone to oxidation under normal use and must be replaced every five to six years in order to maintain the battery’s functionality. The replacement of vanadium electrolyte equates to roughly 30 percent of the total system cost over the life of the battery.
The cell stacks for flow batteries can be a large part of the O&M equation because they last only eight to 10 years as a result of the acid electrolyte degrading the anodes. So, the cell stacks for this kind of system will have to be replaced at least once during the life of the battery — at a significant expense — if the battery is to last the projected 20 plus years of a zinc-iron system. Not only does the electrolyte of vanadium and bromine-based systems degrade the cell stacks, but electrolyte storage tanks, pumps, seals, gaskets and the like are affected by acidic electrolyte, accelerating the degradation of those components as well.
Alkaline zinc-iron electrolyte, which is already less expensive than vanadium, has been tested to last well over 20 years without replacement, greatly reducing O&M costs. Unlike systems using an acidic vanadium or bromine electrolyte, chemical replacement for zinc-iron systems does not require personal protective equipment like a hazmat suit; the maintenance can be done wearing only goggles and gloves.
The chart below provides estimated O&M costs per kWh for lithium-ion batteries and vanadium flow batteries compared to their zinc-iron flow battery counterparts.
The evolution of energy storage technologies is moving at a rapid clip. Utilities and governments have yet to catch up with the speed of the rapidly expanding market, but are working to figure out the safest and most efficient possible application for these assets. Likely, there will emerge a melee of restrictions, regulations and recommendations for the capabilities, siting and deployment of energy storage on the federal, state and local levels.
As these standards develop, customers will need to make adjustments in their usage of energy storage, whether it is behind-the-meter or in front-of-the-meter, to fit the future regulatory environment. The starting point, though, is to invest in an inherently safe system with the minimum level of complexity, the greatest level of flexibility, lowest ongoing costs and the smallest amount of future risk. So when considering an investment in energy storage for your specific application, it is important to ask yourself, “Do you and your energy storage system have good chemistry”?
Lead image credit: Amy | Flickr