3.2. Constraints
The feasible region of the problem is bounded by a number of
constraints dictated on the decision variables. It means the constraints
limit the decision variables bound, which may be resulted
from physical, technological, energy balance, legal or economical
restrictions. The constraints in the present study are defined by
technical characteristics of the components and by matching supply
and demand sections. The first equality specifies the amount of
hot water demand that should be provided by NG boiler, biomass
boiler and heat pump.