Kawerau Geothermal Station

Generation from an environmentally friendly renewable resource

The Kawerau Geothermal Station taps into a renewable energy source located in the geothermal Rotorua region in the Bay of Plenty region.

This revolutionary plant is owned and operated by Bay of Plenty Energy (BoPE).

• Station Location
• Station Purpose
• Station History
• Benefits of Station
• Generating Plant
• Station Statistics

Location

The Kawerau Geothermal plant consists of two plants. Both plants are located in the geothermal rich Rotorua area and are part of the Bay of Plenty generation portfolio.

TG1 is located at Kawerau, while TG2 is located on the opposite bank of the Tarawera River.

Purpose

The plant provides an embedded form of generation within the BoPE network. This not only saves energy transmission losses but provides energy from a renewable source with significant environmental benefits to some 5,300 residential customers.

History

TG1, the first of two developments, was commissioned in 1989 at a cost of $4.3 million and generates 2.56 MW of electricity. TOI (standing for Tarawera ORMAT Installation, but also in honour of the great explorer and Ngatiawa explorer) has two turbines, each driving a 1.3 MW generator.

TG2, or "Tarawera Geothermal 2" was commissioned in 1993 following on from the success of the TOI scheme. The $5.4 million project uses two turbines to drive a single 3.8 MW generator.

Benefits

The TOI and TG2 generating units produce little noise or visual impact and use an energy source which would otherwise be wasted. The hydrocarbon fluid used in the process is completely contained within a closed loop cycle.

The Tarawera River also benefits from the reduced temperature of the geothermal fluid discharged, lower river temperatures increasing the oxygen content and life bearing capacity of the water.

Generating Plant

Geothermal fluid from the Kawerau Geothermal field is utilised to generate electricity via ORMAT binary energy converters.

The ORMAT system passes pressurised waste geothermal water with a temperature of approximately 170 degrees celsius, through heat exchangers. The heat extracted vaporises a special hydrocarbon fluid called isopentane, which is then forced by its own pressure through turbines, in turn spinning generators to produce electricity. The isopentane vapour is then cooled by large air fin fans and condensed back into liquid for ready for revaporisation.

Operation of the generating units is automated via a computer control system at Bay of Plenty Energy's Whakatane office.

Statistics

Ownership	100% Ownership Bay of Plenty Energy (BoPE)
Systems	ORMAT Turbines Ltd binary cycle geothermal
Motive Fluid	Isopentane
Geothermal fluid inlet	172 Deg. Celsius at 8 bar
Transmission voltage	11,000 Volts
Gross Output	TOI 2 x 1.28 MW TG2 1 x 3.8 MW
Operating Pressure	TOI 16 bar TG2 13 bar
Motive fluid flow	TOI 150 tonnes/hour TG2 300 tonne/hour
Geothermal fluid outlet temperature	TOI 109 Deg. Celsius TG2 85 Deg. Celsius
Geothermal fluid flow	TOI 133 tonnes/hour per machine TG2 180 - 325 tonnes/hour
Generator type/voltage	TOI Induction at 600 volts TG2 Synchronous at 11,000 volts