Fine-tuning some innovative techniques in geothermal power production led a slight production delay for U.S. Geothermal's 8.6-megawatt power plant near Gerlach.U.S. Geothermal Chief Executive Officer Dan Kunz says several problems cropped up once the plant went into commercial production on May 25. The main issue, Kunz says, was unwanted vibrations in the turbine gearbox as the turbine cycled up to full operating speed about 4,500 revolutions per minute.The refrigerant used inside the turbine is slightly heavier and denser than test fluids used when the turbine manufacturer conducted initial spins on the unit at its factory, Kunz says. To correct the …