There's no reason why an energy generator could not sell entitlements to 10 years' worth of production

My electricity producer recently offered a low fixed ten year price in return for an upfront payment that they could use to build another wind power plantation. So something like that then?

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But it should now be clear that there is no distinction between "delivery" and "supply". If there is any doubt that the commodity will be delivered/supplied, the sale of certificates will be difficult to say the least. So waffly language such as

'confidence accounting'. ie the probability that a particular flow will be achieved

expectation of access to delivery

there is a need for a guarantee of performance

won't cut it. You actually have to garantee investors that there is sufficient supply to cover the certificates issued -- and more importantly, investors have to be convinced of that, or they will put their money elsewhere.

The function of these certificates as a form of money would therefore be strictly limited by a quantity of kWh, or rented accommodation/duration. The difference between this and the gold standard isn't clear to me.

The social usefulness of the certificates would seem at best to be simply a form of advance subscription with an advantage attached (discount). But who is addressed by the system? People with enough money to subscribe in order to gain a future advantage. One of the privileges of those who have enough money is in fact to save money by bulk buying, for instance, while those who live from hand to mouth pay top dollar for necessities (old example of the shilling in the gas meter?). Given that those who have no money ahead of them are far more likely to be living in rented accommodation than to be home-owners, what access will they have to your proposed rental scheme? In other words, what increased equality ie power-sharing would be achieved by it?