Evaluasi Kinerja Menara Pending Pada Pembangkit Listrik Tenaga Panas Bumi Dieng, Wonosobo, Jawa Tengah
Dieng geothermal power plant is already known to have high silica concentration in geothermal fluids since operated in 2003. The existing problem faced by Dieng geothermal power plant is silica scaling in steam pipe as well as in geothermal wellbore. Silica formed causes decreasing turbine steam supply that impacts on electric production decreasing of Dieng geothermal power plant. Referring to the production data in this researches during April 2010 March 2011, available maximum power generated by steam turbine is only about 38,75 MWe out of 60 MWe total capacity. The decreasing electric production prompt to Dieng geothermal power plant to enforce efficiency to increase power plant output. Efficiency is aimed to decrease electric power consumption needed by existing components in geothermal power plant system. One of component that consume big power is the cooling tower. The purposes of this research are to evaluate the shifting of the tower performance as the consequences of the decreasing hot condensate flow into cooling tower and to find the best alternative to increase cooling tower efficiency. Cooling tower will be evaluated using Merkel theory. Evaluation will be performed by forming calculation models using software Microsoft Macro Excel 2007. Models are divided into 2 stages: i.e Power Plant System model and Cooling Tower model. Power plant system model is aimed to predict hot condensate flow into cooling tower or cooling tower burden based on available power generated. As cooling tower is purposed to predict temperature of air and water come out tower and to know electric power supply needed by cooling tower fan to cool hot condensate. Evaluation is carried on in varied operation condition. Evaluation result shows that the efficiency of power consumption can be increased in 2 ways, i.e. by setting operation of the cooling tower cells or by replacing the fans motor with a low-capacity motor. Setting operations can be done such as when power plant generate electricity of ≤ ±38,09 MWe, then one cell of cooling tower cells can be turned off and will get power saving of ±14,97 kW, equivalent to US$ 497,75. The lower power generated by power plant more cells can be turned off and greater power savings obtained. Another way that can be done is to replace fans motor with a capacity of 60 HP engine, it will get a savings of ±41,18 kW when all cells operate at optimum conditions.