Proportional processes (storage & transmission, perhaps?)

[ojdo]

Commit 0257631 (in branch haag15) and following demonstrate how to represent distributed energy conversion processes. By being able to specify that certain process output commodities must meet a constant, but flexible share of a connected demand at all times, these processes cannot be used like peak load plants. Instead they correctly represent a distributed fleet of independent units that meet "their share" of the demand.

1st open question: the obvious generalisation would be to allow storage processes (e.g. distributed hot water storage in residential buildings) to get the same feature. However, it is not obvious how such a constraint could/should be implemented exactly. How could it be done?

2nd open question: Would the generalisation to transmission processes add any value?