Vattenfall Europe Hamburg A.G.-Wärme supplies in Hamburg ca. 390,000 residences with district heating for space and water heating. This thermal energy is generated at various locations. Besides heating plants, which are used only for generating heat, there are also two hard coal fuelled CHP plants generating simultaneously power and heat.

Through the market liberalisation in the electricity sector, the promotion of Combined Heat and Power (CHP) generation by the German Law "Gesetz für die Erhaltung, Modernisierung und den Ausbau der Kraft-Wärme-Kopplung" (KWKModG) and in view of the developments with CO₂ trading it is increasingly important for operators to optimise their plant park.

In the district heating network of Hamburg excellent optimisation potential exists, because both distribution and generation belong to the same hands and generation is not based on a single plant only. The operator is thus in a good position to economically and ecologically optimise the operation of his utility park, while still fulfilling his obligations to the customers.

Towards achieving this it is essential to simulate in a model both the district heating network with its thermal hydraulic characteristics and the generating plants. The latter are simulated using a process simulation model.

Aim of the simulation is to combine all models and consider all boundary conditions, such as

• Temperature
• Weather
• Electricity prices
• etc.

to forecast the optimal mode of operation corresponding to the instantaneous operating conditions prevailing and generate a schedule of plant operation, while considering also the availability of the units.

Apart from planning the generation schedule for the next day it is also possible to react during the day to changes in the boundary operating conditions and, if necessary, correct the operation schedule of the units.