| Title | An Improved Hybrid and Cogeneration Cycle for Enhanced Geothermal Systems |
|---|---|
| Authors | I Made Astina, Merly Pastalozi and Haruki Sato |
| Year | 2010 |
| Conference | World Geothermal Congress |
| Keywords | cooling, heating, power, thermodynamic, cycle |
| Abstract | Geothermal energy is one of alternative energies that should be used as optimally as possible. Conversion of geothermal energy to be electric energy plays important role in saving energy resource due to advantages of utilization of electric energy. Energy state of steam before entering turbine plays important role on specific output power. Shortcoming of steam quality from geothermal well is one factor causing most geothermal direct expansion power plant produces low thermal efficiency. A hybrid system is proposed to enhance geothermal system. Modification of a conventional geothermal power plant is conducted by combining with a gas turbine, a refrigeration-heat pump, and organic Rankine cycles. Quality of steam from the geothermal well should be heated before entering the steam turbine. Organic Rankine cycle is included to utilize low thermal energy of exhaust gas to generate power. Refrigeration and heat pump system is introduced to cool inlet air into gas turbine and as an additional heat source of working fluid in an organic Rankine cycle. Most evolved parameters are investigated such as temperature, pressure, working fluid, and pressure ratio. The hybrid system can improve significant efficiency from 19.69% to be 37.84%. Fossil fuel utilization factor of the hybrid system is up to 56.27%. Increment of net output power and efficiency of the direct expansion cycle in the hybrid system are 42.70% and 15.86%, respectively, compared to the conventional geothermal power plant. The best working fluid from thermodynamic aspect for organic Rankine cycle and vapor compression cycle is R-600. The preliminary results show that the new cycle increases significant efficiency of the power plant in case of comparison is made to the old fashioned geothermal power plant. Kamodjang geothermal power plant is chosen as a study case in this study, therefore data set from this power plant is used in simulation. Simulation result indicates that the total thermal efficiency rise is more than 65% compared to the old fashioned geothermal power plant. Fuel utilization factor is introduced to judge effectivity of fuel usage. This factor is defined as additional net power compared to the old fashioned geothermal power plant divided by energy input to gas turbine system. This factor can be reach as much as higher than 40%. Using R-600 as working fluid for organic Rankine cycle gives the best result. Any optimal operation condition will be furthermore discussed in full paper of this abstract. |