Staw-Fired Micro Scale Cogeneration System – Numerical and Experimental Analysis
Due to simple construction and low costs of operation, straw-fired batch boilers are interesting heat sources dedicated to use in farms, residential houses and other industrial facilities. Solutions that are available include both air heaters with thermal oil jacket and typical water boilers. Temperature of thermal oil, achieving up to 200 Celsius degrees, makes possible to use straw-fired devices as a source of heat supplying micro scale cogeneration and trigeneration systems. First part of this paper shows experimental analysis of a micro combined heat-power system based on modified Rankin Cycle operation. 100 kWth straw-fired boiler with oil jacket was used as a heat source. Heated thermal oil from the boiler was transferred to the evaporator, superheater and oil/water heat exchanger in case of emergency. Steam which was generated was used to power a 20 hp engine. Cooling water which was heated in condenser was pumped to water tank which was connected with two air coolers. Controlling of the process was realized using a dedicated automation system based on the PLC controller. Second part of the study was intended to developing and modelling experimental installation in TRNSYS software. The dynamic operation conditions in terms of temperature and power were analysed for main components of the installation (steam engine, evaporator, condenser, boiler). Modifications in the system construction improve its performance were also proposed. Results of the experimental tests allows to identify main aspects of the considered system – temperature, steam pressure and power levels in all circuits and operating parameters of the steam engine. Simulations performed in TRNSYS allowed to find the nominal operation scenario for the tested system and shown high potential of the further improvements in the system construction.
Keywords - Micro Cogeneration, Renewable Energy Sources, Biomass, Straw-fired Boiler, TRNSYS, Dynamic Simulations.