The ornamental design for an energystoragesystem, as shown and described.
1. Energy storage system
1.1: Front perspective view
1.2: Front
1.3: Back
1.4: Left
1.5: Right
1.6: Top
1.7: Bottom
1.8: Upper back perspective view
1.9: Lower back perspective view
The fine lines on the drawings indicate the curved surface and the display part; reproduction 1.1is a front perspective view of the energy storage system; reproduction 1.2is a front view thereof; reproduction 1.3is a back view thereof; reproduction 1.4is a left view thereof; reproduction 1.5is a right view thereof; reproduction 1.6is a top view thereof; reproduction 1.7is a bottom view thereof; reproduction 1.8is a upper back perspective view thereof; reproduction 1.9is a lower back perspective view thereof; this design is for an energy storage system with LED indicator at the front; there are holes at the rear bottom part to insert forks of a forklift, so that this design can be easily moved or installed by the forklift.