Energy Storage Systems Overview

Study Notes

To select the best storage design solution, understanding a storage device's capacity and performance is critical.
The power range and energy capacity in relation to system autonomy are the two most significant ratings.
The power range is represented on the horizontal axis using six decades, starting from 1kW to GW.
The vertical axis shows system autonomy, measured in powers of 10h.
The product of power multiplied by time provides the energy capacity.
The surface delimited by the horizontal and vertical lines in the diagram represents the energy capacity.
Conventional technologies with real systems are represented in the lower half, with a possible autonomy of up to tens of hours.
This includes flywheels, Li-ion, and lead-acid batteries.
Long-term storage, or seasonal storage, with up to 10^3 h autonomy, is important for applications that require long-term energy storage.
For example, transforming solar power into hydrogen over three months (100 days) needs this kind of storage capacity.

Weight energy density is represented on the vertical axis.
The symbol for weight energy density is 𝒆𝐦 [𝐖𝐡/𝐤𝐠], typically expressed in 𝐖𝐡/𝐤𝐠 or 𝐤𝐖𝐡/𝐭𝐨𝐧.
The horizontal axis displays the volume energy density.
𝒆𝐯 [𝐖𝐡/𝐝𝐦𝟑 ] is the symbol for volume energy density, represented in 𝐤𝐖𝐡/𝐦𝟑 or 𝐖𝐡/𝐝𝐦𝟑.
Mobile applications prioritize weight energy density.
The "Solarimpulse" project is an example that utilizes high-performance batteries to enable overnight flight using energy stored by photovoltaic cells on its wings during the day.