How the power station works


Using ‘state of the art’ technology, geothermal fluids are passed through a heat exchanger where energy (heat) is transferred to a working fluid (pentane). The pentane then boils to form a high-pressure vapour which then drives the turbines, turning the generator.

When the vapour has passed through the turbines, it is condensed back to a liquid and returned to the heat exchanger in a continuous cycle. The pentane is not consumed as a fuel, but is simply used as a working medium to extract energy from the geothermal water and steam.

Having given up much of their energy, the geothermal fluids are returned to the deep geothermal reservoir, via re-injection wells. This practice not only prevents geothermal fluid discharge into the environment (where adverse effects would occur) but also maintains reservoir fluid mass. This in turn enhances the long term sustainability of the geothermal resource as well as minimising the possibility of any surface subsidence.

Additionally, energy can potentially be extracted from the fluid and used as an energy source in other industrial processes (such as wood processing, dairy milk processing and aquaculture).

Top Energy has resource consents to operate its three existing power stations within strict resource consent conditions to ensure best practice management of the geothermal resource. Compliance with the conditions is monitored by independent environmental specialists and the results reported to Northland Regional Council and a Peer Review Panel.