AWARDS FINALIST: Ngāwhā Generation

Ngāwhā Generation says a surprise threat from the Climate Change Commission provided an interruption to its business model for the better.

Just a month after commissioning its third geothermal power station – OEC4 – in 2020, the commission recommended the closure of the entire Ngāwhā operation by 2030.

Although the commission’s final report withdrew that recommendation, the significant increase in the cost of carbon units foretold the closure of the business.

In response, parent company Top Energy embarked on an extensive sustainability journey enabling Ngāwhā to become the country’s first zero-emitting geothermal generator by the end of 2023.

Ngāwhā

The commissioning of OEC4 made the Far North a net exporter of electricity, providing energy independence and other flow-on benefits to a socio-economically challenged community.

Ngāwhā had been the country’s highest emitting geothermal power station at the equivalent of about 300 grams CO2/kWh.

The company is now on track to be the first zero-emitting geothermal power operator, and is set to achieve that on a geothermal field with the highest greenhouse gas content and some of the most problematic chemistry.

Decarbonisation is expected to cost $4 million in total and will have taken 18 months, against a budgeted $16.4 million and a timeline of 10 years. This work is being done while maintaining full operation and compliance.

That investment has a pay back of six months and required little financial analysis. Ngāwhā Generation says it is unusual for an initiative like this to deliver within such a short operational timeframe and small budget.

The company is producing zero greenhouse gas emissions from all but 30 per cent of one of its power stations. That last step will be completed in September and will see a total of 128,000 tonnes of CO2 equivalent gases reinjected to the geothermal field annually.

Non-condensable gas reinjection

Reinjecting greenhouse gases was previously considered a risk not worth taking. However, Ngāwhā Generation believes climate policy has made it a necessity and says the solution can be both low cost and low risk.

The company’s operational team undertook the work internally and adopted a ‘fast-fail’ approach. The results exceeded expectations.

In mid-2022, a decarbonisation trial was undertaken at the Ngāwhā geothermal power station to test the effectiveness of reinjecting non-condensable gases.

Reinjection was carried out in four stages, with initial experiments conducted on Station One, then rolled out to Stations Two and Three. The goal was to reduce or eliminate greenhouse gas emissions and the targeted date for completion was 2026.

Deloitte certified Station One and Station Two with a unique emissions factor of 0.0442 tonnes per tonne of steam for calendar year 2022, roughly half of what it was previously.

It will now audit Ngāwhā annually, with the generator targeting zero UEF across all stations in calendar year 2024.

Moving forward

The focus now is on completing the reinjection of the final 30 per cent of emissions at OEC4. The company says it is on track to achieve zero emissions from the entire fleet of power stations during the next annual shutdown scheduled for September.

If a future business case is approved, construction of the firm’s next station – OEC5 – will integrate reinjection into the station design, effectively “zero carbon by design”.

In addition to eliminating emissions from its electricity production, Top Energy Group has also committed to gaining carbon zero certification across all its operations in early 2024.

The Low Carbon Future Award category is sponsored by Energy Resources Aotearoa