Energetic and economic investigation of the operation management of an Organic Rankine Cycle cogeneration plant

In the past few years a special attention has been paid to the use of renewable energy, but some negative features of these sources (low power density and unpredictable availability) bring about remarkable difficulties of economic payback. For this reason, in many countries incentives are provided to promote energy conversion plants fed by these sources. Such incentives can influence not only the design of new plants, but also their operation strategy. This paper describes the results of the energetic and economic analysis of a new plant sited in Asiago (Italy), for different operation strategies. The plant consists of 2 boilers fed by the wastes from a sawmill: one of them directly supplies hot water to a district heating grid, while the other provides heat for a cogeneration (ORC) Organic Rankine Cycle. The ORC plant has a nominal electric power of 1.25 MW and can produce 5.3 MW of heat. It is connected to the electric grid and to the local district heating grid. The emissions have been evaluated, too and compared with those of the pre-existing situation: domestic boilers fed by natural gas or diesel oil.