What is the energy loss (roughly) when using a spring to store energy?

Question

Are there any, or have there been any, large scale applications of this , such as storing electricity.

Answer 1

The energy loss of a good steel spring is very low.  They are used to store energy in the suspensions of cars, trucks, trains etc.  But they store mechanical energy, not electrical.  Conversion losses would render them ineffective.

The most common mechanical storage for electric energy is a pumped hydroelectric facility.  They are economical because cheaper off-peak energy can be sold as more expensive peak energy, and the storage is cheaper than building more generating capacity to handle the peak demand.

Answer 2

When a spring is put under tension there is heat loss from friction.

Springs do not store much energy for their size and deform with use, reducing their performance.  The springs would need regular inspection and replacement which would be too costly.

Having springs around high voltages is also a recipe for short circuits.