Bullfrog
Ultimate Member
As others have said, solar panels and rechargeable batteries.
If you have a solar set up, you might be able to recieve goods in exchange for charging other people's batteries for them.
It would be useful to have a variety of chargers on hand. For example, chargers for 12v car batteries, 6v batteries, lithium batteries, AA, C, and D rechargeables, etc.
A large stock of the small rechargeables you could barter away could be a continuing source of income as people return to get them recharged.
ETA: oops, just saw Alan mentioned this way back on post #9.