Solar Power World _ MARCH 2017

Page 42



Calculating the TRUE COST of energy storage Differentiating between price point and cost is paramount to advancing the solar+storage discussion with regard to performance and real value over the life of the project. Whether evaluating lead acid, lithium ion, flow or others, the various combinations of battery chemistries, form factors and architecture can impact the true cost of energy delivered over the battery’s useful life. While it is common to make purchasing decisions based on published, upfront price points per watt hour (Wh), determining the Levelized Cost of Energy (LCOE) over the battery’s useable lifetime is a more accurate and reliable method for understanding the battery’s true cost and ROI for customers. To calculate the LCOE in Wh for any battery technology, use this industry standard formula: 4 0 SOLAR POWER WORLD

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The more challenging step may be collecting the data you need to fill in the blanks. All of these data points should be found on the manufacturer's specification sheets, with the exception of available capacity.

Step one: Fill in the basics Price is the published price point for the battery, regardless of stated capacity, depth of discharge or other performance parameters. Cycles is the number of full charge and discharge cycles expected over a battery’s warranted lifetime while it has at least

80% of its original published capacity left, which is the industry standard end of life definition (EOL). Be aware that some battery manufacturers do not disclose the EOL for their battery, which makes it difficult to assess LCOE accurately. Others do not hold to the EOL industry standard of 80% and allow 60% to 70% degradation during the warranted life of the battery, which negatively impacts the LCOE. Depth of discharge (DoD) is how much total energy can be drawn from the battery in one complete charge/discharge cycle. On average, 80% DoD is common. However, the DoD may be as low as 50%

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