As energy has a usefulness and intrinsic value that even gold lacks. It could be traded anonymously like cash like batteries as dollars or as energy storage and quick and efficient transfers becomes smaller and more convenient. Im thinking specifically electrical energy with batteries and capacitors but even gas could be used.
It could be created by individuals with solar panels or bike mounted generators. It could be stored as potential energy in large amounts as heat or pressure and then converted back to electrical energy when needed. It could be networked for large transfers. There could even be large banks that hold energy as a business, but they would not be able to lend more than they hold. Private individual energy storage would be the most secure from government or other seizure obviously.
Wheres the flaw?
Not really a flaw at all.
The US petrodollar has been a pseudo energy backed currency for the last 50 years. Bitcoin is also an example of a currency that is predicated on needing energy to establish its value.
The only issue, which you glossed over, is storage of energy. That is difficult and expensive. This is why it has only ever indirectly backed a currency. Gold is a better asset backing than energy, because it is more easily stored, divided and transported.
But as the 2 examples above illustrate, energy can be successfully made the basis of value.
Once you have bitcoin though, it doesnt have any intrinsic value. It has value because more than one person says it has value.
I did mention storage and the tech is getting better all the time. Batteries in their current form are more like dollar bills. You wouldnt want to carry more than 20 on you at a time. But new battery technology for walking around cash or just other forms of potential energy could be used, either chemical, something similar to a water tower for long term storage.
A very important property of money you are missing. It never has intrinsic value. It is an accounting mechanism. That is all. The salient point is what governs and restricts that accounting mechanism. It always has value only because 2 parties accept that it represents value.
Barter, on the other hand, is the exchange of intrinsic valued things that people need for daily function.
But energy is very hard to barter directly, because it can not be easily transported. Even if stored in batteries or hydro (with terrible efficiency losses mind you), you can not easily move it from one place to another. Oil is probably the best energy storage mechanism that can be easily transported, and thus, bartered.
Im thinking small scale to start with until tech catches up. Start with farmers markets and garage sales or places where bartering might already be happening. Large purchases like a car or house would be difficult currently and maybe more easily done with oil.
The point is, the energy in your battery (and the battery itself) in your pocket does have value and is currently transportable. If i anticipate tech to get better and energy density, storage efficiency, and transfer efficiency to all improve. This could be a way to get away from fiat currency and have something that wouldnt be vulnerable to market crashes.