I grok prepay. I've been administering a prepay food coop for some years. Everything is prepaid (in euros, but it could be a local currency if everyone agreed on it). However, it's an account and not a certificate system.

The money people put in is credited to their account and the goods they receive are debited. There is no absolute guarantee of delivery: if a producer has problems and can't deliver, all concerned may decide he can keep the prepay without supplying the goods, because the aim of the system is to support local family-level quality farming. (At least, this is a principle written into our contracts -- in practice, producers prefer to waive their rights in this kind of case.)

What my comment above was getting at was that your system is certificate-based, and the certificates are bought and sold on a market. You say there is no guarantee of delivery. I can only imagine you mean dated delivery, because if the certificate is redeemable against supply (delivery? is there a difference?) and there is no supply, we'll see an almighty crash on the market for these certificates. In fact, without a guarantee of supply/delivery, no one will buy the things in the first place.

Or, as you say below in a reply to askod,

ChrisCook:

When examining and judging energy prepay unit issuance you have to have regard to the rate, and the likelihood, of a flow of energy over time.

This implies what I have heard described as 'confidence accounting'. ie the probability that a particular flow will be achieved.

In fact, a right to delivery is essential, or no one will have any confidence in the system. So I don't think you've answered Mig's question:

Migeru:

how do you prevent more money to be created than there is available energy, and how do you prevent energy certificate hoarding and "cornering the market" so to speak.