Mitigation of Wind Effect on Air Cooled Condenser Performance
Omri MESHULAM, Dvir MENDLER, Anton FITERMAN
[Ormat Technologies, Inc., USA]
Rankine cycle condenser thermal performance determines the turbine back pressure, thus has direct impact on power plant generation, especially in low enthalpy (geothermal heat resource) Organic Rankine Cycle application. Wind has a major effect on Air Cooled/Heated Heat Exchangers in general and Air Cooled Condensers (ACCs) thermal performance in particular. Ambient wind interferes with air flow regime, causing inefficient heat exchanger area, fans disturbance – air flow reduction and hot air recirculation for induced and forced draft air-cooled heat exchangers. Wind effect analysis was performed in Don A Campbell (DAC), an Ormat geothermal power plant in Nevada, US. Degradation of 4%-23% in net power plant generation was recorded and attributed directly to wind effects, wind velocities ranging at 3-10 m/s. In order to mitigate the deteriorating wind effect on the ACC, Wind Guiding Vanes (WGV) system was developed using computational fluid dynamics (CFD) analysis and optimization process, currently patent pending. Negligible effect on the ACC performance in no wind conditions, low manufacturing cost and zero maintenance, were key factors in the WGV system design. A two-phase implementation process was performed: First phase: an experimental WGV system was installed on 6.5% of the total ACC having a plot area of approx. 375x20 m². Field tests were executed including fan flowrate measurements and smoke tests, for aerodynamic performance validation. A dedicated fan flowrate device was designed for continuous airflow measurement and data acquisition at windy and still ambient air conditions. Results showed a significant performance improvement with the WGV system equipped bays in windy conditions. A good validation of CFD analysis was obtained via field tests. Second phase: following the proof of concept, full-scale WGV system implementation on all of DAC ACC was executed. Up to 15% of net power generation increase was achieved at windy conditions by equipping the ACC with a WGV system. This paper reviews existing wind effect mitigation methods for air cooled condensers, fundamental analysis of the problem and Ormat designed solution. The conceptual design, considering cost-effectiveness and thermal performance recovery is explained. Experimental system field tests results and full-scale implementation results are presented, as well as yearly power plant generation gain.
|        Topic: Power Generation||Paper Number: 26108|