Aviv, Super Capacitors are one of the best ways to store AC or DC electric power. Most super capacitors to work the best have to be very cold. Sometimes this is not practical. I used a gang of super capacitors inside a DC to AC inverter
I developed back in 2007. It worked great and did everything I needed to handle the spike conditions found in starting electric motors. Then I abandoned that product and found a better solution that does the same function but cost a fraction of the cost. If you are starting a 25 HP electric motor the only solution is the use of Super Capacitors. Then the cost is reasonable but to start a small 10 HP motor you need batteries. To start a small motor then you need the "Spike Supply System". It only holds 6,500 watts or during start up it is go for a electric motor that is around one HP or less. One HP equals to 746 watts for running without a load. To start a one HP motor dependent upon the motor design. A open motor design will take almost 3 KW to 3.8KW to start without a load. A enclosed electric motor or TEFC will draw twice as much to start, again without a load. Put a load on the motors and draw or demand goes higher. I really know about motors . This is how we test the output of a robust solar PV system. Once we put 400 AC 1/2 hp electric motors on a system for testing no loads. We let it run for two weeks and then after the tests we shipped the system. We could see the results for every motor that we attached to the system. This was a customer's requirements for our testing of the system. It worked without any problem for two weeks but what a loud noise we had in the back of our lab and we did get warm from all those motors running.