I heard the other night on NPR (National Public Radio in the US) a clever solution for our energy problem. This is how it goes:

1. Solar energy farm for electricity supply are developing raqpidly due to declining cost.

2. However, electric energy demand are more intense during evening/night when people are at home needing electric energy for cooling and ligthing. But that is when sunlight are not available.

3. To store energy genertated during day light hours require large battery facility which can en expensive

4. Electic vehicles are selling one to two million units per year all over the world. Each EV vehicle need batteries.

5. However, batteries gradually loses their storage capacity due to repeated charing/discharge.

6. When these batteries storage capacity  decline to 60% of their original new condition they must be replaced in the vehicles. Reconditioning these used batteries can be expensive.

7. Why not use these "useless" 60% batteries (they are very inexpensive) as storage devices for the solar energy farms. You are turning a useless object to serve useful purpose. Everyone is happy!

We call this a clever solution that is being developed by the energy industry !!!