Case study: Cardrona Valley Wastewater Treatment Plant
A solar thermodynamic solution for the Cardrona Valley Wastewater Treatment Plant
The new plant, designed and built by Apex Water, serves Cardrona village, the Cardrona Alpine Resort and new residential and commercial development in the valley. It was commissioned in September 2020.
The alpine environment called for some innovation. In particular, the wastewater had to be kept at the right temperature for the bacteria to do their job in the treatment process. Direct electric heating was ruled out as inefficient, gas heating was unacceptable because of its greenhouse gas emissions, and direct solar heating would be ineffective in winter. Solar thermodynamic heating was the solution.
The system
The system consists of 32 solar thermodynamic panels and a Solar Block unit. Solar thermodynamic panels take heat from the environment even in snowy winter conditions and at night. Find out more about how solar thermodynamic heating works.
The results
In his paper to the Water NZ conference, Dr Matt Savage from Apex Water Ltd says: “The solar thermodynamic heating system was able to maintain the reactor temperature above the critical nitrification temperature under all operating conditions. This included through July 2022 when the panels were covered in snow for a week.” In his conclusion he says: “Solar thermodynamic heating represents a viable low carbon emission alternative to fossil fuel heating of wastewater in extreme cold climate environments.”
Further reading
- Dr Matt Savage's full paper, 2022 Water NZ Conference and Expo
- Business South magazine feature on the Cardrona project (November 2022)
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