Development and verification of a TRNSYS energy system simulation model for a combined heat and power dual-fuel system

Abstract

Many companies suffer economic losses due to unannounced, interrupted power supply caused by electricity cuts. These companies then purchase electricity generator units to supply electricity during these times. This however, is a costly exercise as diesel is expensive, CO? emissions are high and heat energy is wasted. An alternative, permanent, constant energy supply system, such as a CHP dual-fuel system thus needed to be properly investigated. The aim of this study was to develop and verify an energy system simulation model known as TRNSYS, as a means to identify an appropriate CHP dual fuel system that could replace traditional power generators and suppliers. The literature study revealed the importance of energy management with reference to the South African context. The use of CHP dual fuel systems as an alternative energy source were confirmed and the crucial components of CHP systems were described. Dual fuel, including the use of bio-gas, as an alternative energy source for CHP systems was emphasised. Based on the components installed in the CHP dual fuel demonstrator used for this study, the input data requirements for each library component TYPE, selected for modelling purposes, were entered into the TRNSYS model and output values were then generated. The TRNSYS output values were compared to the measured and calculated values obtained for the CHP dual fuel demonstrator in use at Uilenkraal farm. The TRNSYS model produced similar outputs, within a 15% deviation, to that of the CHP dual fuel demonstrator for the majority of the components selected. It was concluded that the TRNSYS energy system simulation model could be used to identify a suitable CHP dual fuel system that could provide an alternative, permanent and constant energy supply and could lead to a reduction in CO? emissions, efficiency gains and cost saving. Recommendations were made to use TRNSYS as a modelling tool, prior to the manufacturing and installation of a CHP dual fuel system. It was also recommended that TRNSYS be refined to improve the predictive validity of the TRNSYS model outputs.