Off the grid: Castle Hill’s vision to power itself

Saturday, 2 November 2024

A sleepy alpine village nestled in the foothills of Te Waipounamu is investigating going off-grid, as potential infrastructure challenges keep its growth on ice.

Castle Hill village has struggled with electricity insecurity due to its isolated location between Porters and Arthur’s passes. At Labour Weekend, heavy snow left 263 properties from Arthur’s Pass to Castle Hill without power for more than three hours.

Castle Hill hosts about 15 primary residences and almost 200 holiday homes used year-round. More than 100 extra homes and eight commercial premises were planned to join the village in the coming years under Castle Hill Developments.

Power outages are a common issue that holiday home owners Helena Parsons, Kate Hodgins and Dave Laurie are trying to tackle. They have sought help from the Community Energy Activator, a 13-week community electricity resilience programme run by Orion Group, clean energy agency Ara Ake and the Community Energy Network. Orion would not provide resources, but would provide mentoring to the community group.

The project was investigating batteries, solar panels on homes, solar arrays (a collection of solar panels) on council land, and solar networks that could see electricity shared between homes.

A feasibility study investigating cost and potential stakeholders support would be conducted in the coming months.

Hodgins said the energy needs of the nation were increasing, so finding solutions outside of the traditional power supply would help strengthen electricity security while taking the pressure off power and lines companies.

“We’re still working out exactly what that’s going to mean for the community.”

In a recent survey by the Castle Hill Community Energy Project, property owners were asked if they wanted cheaper, more resilient power that would better support emergency responses.

Almost 90% of the 64 respondents said yes, with most indicating they would consider investing their own money into the project.

Parsons said it was an incredible response from the community, most of whom were holiday makers.

Sean Moran, who has lived in Castle Hill for more than 30 years, said improving electricity security was a good idea, but he believed it would take “enormous funding” that could create a divide between property owners if some invested and others did not.

“People who put their money in will expect to get their money back, but it has to be open to the wider community to enjoy,” Moran said.

“The only way to do this properly is through taxation or rates.”

As it was early days, the specifics of how the power would be shared, or if it would be shared with properties that did not sign up to the project was yet to be determined, Parsons said.

Waste water challenges

With about 120 residential and eight commercial new sections planned by Castle Hill Developments in the coming years it was unclear how the energy project would be impacted by an expected steep increase in population.

Another question mark hangs over the capacity of the waste water treatment plant.

Castle Hill’s wastewater scheme uses gravity to send waste to an oxidation pond and it is then irrigated over farmland.

About 20 homes in the new subdivision had been developed, but Inovo Projects co-director Peter McAuley who was leading the development said work had halted due to limitations on the village’s wastewater treatment plant.

“We’ve come to a bit of a standstill because the sewage upgrade that [Selwyn District] council needs to do to their plans have not yet been done.”

However, the scheme was consented to discharge up to 435m³ of contaminants daily from May to August and 785m³ from September to April.

According to an assessment from January the average daily discharge was 45.4m³, peaking at 156m³, leaving significant space for growth.

The council planned a $2.6 million system upgrade which could be used to buy more land to irrigate treated water ($900,000), install new systems ($1.17 million), upgrade power to the plant ($169,000), and develop access ($92,500).

Almost half of the village’s 42-year-old sewer system (48%) was in poor condition, but a third (34%) of the system centred around the new subdivision to the north of Castle Hill Dr was in very good condition.

The plant was at a “significant risk” of breaching consenting conditions by over discharging wastewater onto a nearby property.

McAuley said the council was trying to buy more land to increase its capacity for irrigation and support more homes in the village, but were met with complications regarding the Department of Conservation, iwi, and landowners.

Selwyn councillor Lydia Gliddon said the council was working to purchase land, but was unable to comment further due to commercial sensitivity.