Dynamic modeling for assessment of steam cycle operation in waste-fired combined heat and power plants
Journal article, 2019

As the share of non-dispatchable energy sources in power systems increases, thermal power plants are expected to experience load variations to a greater extent. Waste-fired combined heat and power has multiple products and is today primarily operated for waste incineration and to generate heat. To consider load variations in the power demand at these plants may be a way to provide system services and obtain revenue, however, the transient interaction between power and district heating generation for the type of steam systems used should be studied. This work describes the transient characteristics and timescales of cogeneration steam cycles to discuss the operational interactions between power and district heating generation. A dynamic model of the steam cycle of a 48 MW waste-fired combined heat and power plant is developed using physical equations and the modeling language Modelica. The model is successfully validated quantitatively for both steady-state and transient operation with data from a reference plant and is shown capable of characterizing the internal dynamics of combined heat and power plant processes. Simulations are performed to analyze steam cycle responses to step changes, ramps and sinusoidal disturbances of boiler load changes and variability in district heating inlet temperature and flow. The results give insight on the process timescales for the specific case studied; for example, with the present design a 10% boiler load change requires up to 15 min for responses to settle, while the corresponding time for a 10% change in district heating flow or temperature show settling times within 5 min. Furthermore, increasing the boiler ramp rate from 2 to 4%/min could reduce the rise time of power generation by 42%, which could be of economic significance in day-ahead power markets.

District heating

Modelica

Dynamic modeling

Steam cycle

Combined heat and power

Flexibility

Author

Johanna Beiron

Chalmers, Space, Earth and Environment, Energy Technology

Rubén Mocholí Montañés

Chalmers, Space, Earth and Environment, Energy Technology

Fredrik Normann

Chalmers, Space, Earth and Environment, Energy Technology

Filip Johnsson

Chalmers, Space, Earth and Environment, Energy Technology

Energy Conversion and Management

0196-8904 (ISSN)

Vol. 198 111926

Flexible Combined heat and power plants for power systems with volatile electricity prices

Swedish Energy Agency, 2017-10-01 -- 2020-11-01.

Subject Categories

Energy Engineering

Energy Systems

DOI

10.1016/j.enconman.2019.111926

More information

Latest update

9/3/2019 1