Thermo-economic optimization of waste heat recovery Organic Rankine Cycles

Abstract

The present paper focuses both on the thermodynamic and on the economic optimization of a small scale ORC in waste heat recovery application. A sizing model of the ORC is proposed, capable of predicting the cycle performance with different working fluids and different components sizes. The working fluids considered are R245fa, R123, n-butane, n-pentane and R1234yf and Solkatherm. Results indicate that, for the same fluid, the objective functions(economics profitability, thermodynamic efficiency) lead to different optimal working conditions in terms of evaporating temperature: the operating point for maximum power doesn't correspond to that of the minimum specific investment cost: The economical optimum is obtained for nbutane with a specific cost of 2136 €/kW, a net output power of 4.2 kW, and an overall efficiency of 4.47%, while the thermodynamic optimum is obtained for the same fluid with an overall efficiency of 5.22%. It is also noted that the two optimizations can even lead to the selection of a different working fluid. This is mainly due to additional fluid properties that are not taken into account in the thermodynamic optimization, such as the fluid density: a lower density leads to the selection of bigger components which increases the cost and decreases the economical profitability.

Multi-objective optimization of organic Rankine cycles for waste heat recovery: Application in an offshore platform

“…The optimal working fluids differ from the ones suggested in previous works refs. [8][9][10][11][12][13][14][15][16][17][18] since in this paper the heat source is at around 370 ºC while in refs.…”

“…Hettiarachchi et al [10] use as the objective function the ratio of total heat exchange area to net power output. Quoilin et al [11] optimize a small-scale ORC for waste heat recovery applications; economic profitability and thermodynamic efficiency are the objective functions. Baik et al [12] employ the pattern search algorithm to maximize the net power output considering the overall heat transfer conductance and turbine inlet pressure and temperature as optimization variables.…”

“…We apply the methodology to recuperate the waste heat from the SGT-500 gas turbine installed on the Draugen platform (Kristiansund, The North Sea). Compared with previous works [8][9][10][11][12][13][14][15][16][17][18], the approach in this paper is novel in the sense that it includes the total volume of the organic Rankine cycle and the net present value as objective functions. Furthermore, in contrast to previous works, the geometry of the shell-and-tube heat exchanger is included in the optimization procedure.…”

Thermoeconomic Evaluation of Modular Organic Rankine Cycles for Waste Heat Recovery over a Broad Range of Heat Source Temperatures and Capacities

“…The total specific costs of the ORC then account for 2620 €/kW. The total costs are divided by the share of each component which is assumed to be 35% for the heat exchangers, 10% for the pump, 15% for the piping and 40% for the turbine-generator-unit [77][78][79]. For each component, a specific capacity has to be inserted into Equation (6) as follows.…”

Performance measurement of a new concept reciprocating piston expander (RPE) using a newly developed small-scale dynamometer unit

“…Although there are efficient energy conversion systems have investigated and introduced, the *Corresponding author: anuarm@uthm.edu.my fuel consumptions can no longer be reduced when the design points have been met [2], there are still the methods to increase the overall efficiency of the system with fewer fuels and lessen the pollutions. Besides, the introduction of cleaner fuels and replacement or modification of the energy conversion systems being a solution to meet the above objectives, recovering the leftover energy especially in terms of wasted heat into a useful energy has been considered and proposed as the best solution [3], [4]. Among the heat recovery systems, recovering through an Organic Rankine Cycle (ORC) system is a viable method since the ability of this system to recover the most abundant amount of heat at low to medium temperature heat [5] and for small-scale applications [6].…”