The variables status and status_nominal are ignored from the results,
as they are only present for non_convex investment cases

If the dictionnary containing the information about the bus contains a
key "price", its value will be applied to the variable costs of the sink
(unit of the price is currency/energy unit, default currency/kWh)

The reducable demand should be listed within sinks, and provided an
efficiency (number between 0 and 1). This efficiency correspond to the
percent of the demand which must be provided (critical demand). The
oemof-solph sinks which models the non-critical part of the demand has
very small variable_costs such that it should not influence the costs
calculations but should be fulfilled rather than dumping energy into
excess sinks.