Optimisation Of A Fin Fan Condenser In A Geothermal ORC Plant

Abstract

A case study is performed on the fin fan condenser of one organic Rankine cycle (ORC) unit at the Ngawha Geothermal Power Station, Northland, to optimise the number of fans to maximise the economics of the ORC while maintaining safe operation. A practical method is shown where first, key parameters of the fin fan condenser are identified followed by the use of these parameters in a plant model to predict the effect of varying the number of fans and condenser area on the power output of the entire ORC. The number of fans is determined using a heuristic that accounts for the trade-off between capital cost and revenue as well as safety issues that arise as a result of increasing the condenser duty. Finally, the economics of investing in additional condenser equipment is evaluated by calculating the payback period. This involves calculating the increased revenue compared to existing operation, taking into account real air temperature data for the plant, and estimating the capital cost of the additional equipment.