Comprehensive Analysis of Organic Rankine Cycles for Waste heat recovery applications in Gas Turbines and IC Engines

Abstract: Executive Summary This investigation aimed to assess the true technical and environmental potential, plus economic feasibility of the ORC technology as bottoming cycles for Gas turbines and IC Engines power applications. The assessment started by creating a modeling tool using the software EES in order to model several bottoming cycle configurations and match them with the mentioned power generation technologies. This model used as inputs the operational data of small range (5.5V 50 MW) Siemens Gas Turbines and power plant recommended Wärtsila IC Engines. Thus, adding practical reliability to the model. The simulation also defined 5 control parameters: organic working fluid, operative high pressure of the cycle, minimum temperature difference in the heat exchange, degree of superheating and amount of regeneration. These 5 factors were selected because their role in defining not only the power output, but also the economical cost of an eventual application. Six different organic fluids ranging from Alkanes, Aromates and Siloxanes were analyzed in particular ranges for each of the other 4 mentioned control parameters. After the simulation a preliminary analysis was performed through comparative matrixes. This contrast intended to outstand the configuration with the highest power output and the smallest capital investment cost. Although no costs were inserted in the model, this last factor was analyzed through the cycle’s components size. Three different configurations were selected from this analytic process. The two better preforming cycles and a third option that ideally balanced the two examined factors. Further study quantified the fuel and emission reductions per unit of power when the selected ORCs were implemented and the mild environmental impacts that this additions would have were also quantified. Finally a Cost Benefit Analysis was implemented in which it was reached that although feasible, economically ORC implementation is not more attractive that Business as Usual scenario, implementation of the mentioned equipment without bottoming cycle. This investigation concluded that although ORC implementation could be a major technical improvement for IC Engine and Gas Turbine based power plants, increasing the power output up to 20% and 44% respectively, it suffers from high capital prices due to the novelty of the commercial applications and a lack of balance between output, size and reduction of its production costs. It finalizes by recommending that in order to achieve a more positive situation, a strategy towards a higher economy of scale and increased researched in component cost reduction should be performed.