Techno-economic analysis of CHP system supplied by waste forest biomass

Poland, as for Europe, is a country with an average forest cover of approximately 30%. In these forests, more than 37M m³ of wood, mostly coniferous (over 80%), is harvested per year. In 2012, 4.2M m³ of sawn timber was produced (sawn timber without factory lumber). At the same time, in Poland there are over 8000 sawmills, whereas only about 700 of them saw over 90% of the harvested timber. So much fragmentation is a major cause of low sawmills innovation, particularly of those small ones. However, in recent years, a trend of development in this sector is noticeable, and it is through rationalisation of material and energy economy. One of the methods to increase the technical and economic effectiveness of enterprises involved in woodworking is to build in the combined heat and power system (CHP) plant with the ORC system into the existing infrastructure, which will be matched to the needs of the company. This article presents an analysis of the profitability of the investment based on the example of a medium-sized company sawing approximately 50 000 m³ of timber per year, and the economic analysis was performed for prices and costs valid in Poland. The analysis made for the 1650 kW_el organic Rankine cycle (ORC) system, has resulted in a profitability index PI = 1.3, on the assumptions that the ORC system operates for 6000 h y⁻¹, will be purchased at the price of 4500 € kW_el⁻¹ and at the price of electricity sales of 130 € MWh⁻¹.