Energy analysis of a CHP plant with internal combustion engines, for a district heating system, based on the information from the annual database

Building a model for consumption, production and efficiency of a combined heat and power (CHP) system can bring important data for planning and management activity of such a technological system. The results of this study will show the overall efficiency of a real cogeneration plant over a year. The study is based on the information from the daily database of an economic operator, during 2012. The CHP plant, having reciprocating internal combustion engines (RICE) as prime movers, provides the thermal energy to the district heating system of a city from Romania with 129,368 habitants. RICE are operating in simultaneous mode or in partial load. The numerical model reveals the behavior of the daily thermal, electrical and global efficiency, accordingly to the partial load. The model was applied in both calculation assumptions: using the lower heating value and the higher heating value of the natural gas. A statistical analysis of efficiencies of the CHP plant was made. Was performed the statistical analysis of the database efficiency (also called real efficiency) with the global efficiency calculated by the model (also called modelled efficiency). Linear and multiple regression equations explain the variance of the real efficiency and of the modelled global efficiency