How Lodestone’s Te Herenga o Te Rā solar farm rose to flood challenge in July

Solar panels peek above floodwaters at the Lodestone Te Herenga o Te Rā solar farm in the Waiotahe Valley on July 30. Photo / Lodestone

At the end of July an atmospheric river swept over the North Island bringing flooding to the Bay of Plenty, closing roads, causing slips and another round of misery and clean-up for farmers, businesses and residents.

For one operation near Ōpōtiki, the flooding posed an even greater problem.

Lodestone’s Te Herenga o Te Rā solar farm in the Waiotahe Valley faced total inundation as the water rapidly rose to a dangerous level, as water and electricity are not good partners.

“Meteorologists were calling what came through the Waiotahe Valley last week an ‘atmospheric river’; a significant weather phenomenon linked to extreme rainfall,” Lodestone posted to social media in the week following the event.

Fortunately, the site escaped major damage and crew remained safe as the equipment performed as intended.

“Despite the rapid escalation of water levels, it was a huge relief that our site crew and members of the community caught in the flooding remained safe, and the equipment performed as it was designed to do.”

But how was this near disaster averted?

“We planned for this type of event from the outset,” a Lodestone spokesperson said when the Herald made inquiries.

“Detailed terrain analysis and flood modelling informed every aspect of the site’s design, including 4m deep piling, elevation of critical equipment and remote panel stow capability. Design features like these protected the farm from being damaged by the floodwaters.”

As one of the sunniest parts of the motu, the Waiotahe Valley receives an average of more than 2300 sunshine hours annually, roughly 15% above the average for the country as a whole, making it an ideal location for solar power production.

When designing the plan, engineers also knew the area is prone to heavy rainfall events such as the July downpour, and had to incorporate mitigation into the planning to avoid catastrophe.

Painstaking reviews of every rise and dip in the terrain coupled with detailed analysis of rainfall for as long as records have been kept resulted in a resilient design that reduced the chances of damage and ensured a speedy return to production.

The Lodestone Te Herenga o Te Rā solar farm on July 30 (left), showing how high flood waters rose, and August 1, showing the muddy aftermath as the water receded. Photo / Lodestone

A special piling design going more than 4m deep and extra-high solar PV tables, considerations for rapid water flow, the possibility of floating debris, and the prospect of sliding embankments were all incorporated into the engineers’ thinking.

Additionally, the ability to stow the panels in a horizontal position from Lodestone’s remote control centre became a critical part of bracing during this event.

“The farm remained fully operational until the last few millimetres of rain came down, when the operations team decided, out of caution, to disconnect from the grid and ride out the storm,” Lodestone said.

“When the sun rose again, the water receded nearly as quickly as it came. The Lodestone team were able to quickly assess the site with thermal-camera drones, scanning each component and determining just how well the tracking solar technology and flood-mitigation design met the challenge.”

Lodestone says this approach to solar farm design has been applied to all their developments where a flood risk is present.

The work includes advanced climate modelling to guide site selection; investment in flood mitigation design, including extended piles, elevation of critical infrastructure and appropriate drainage and flood gate systems; remote monitoring and control systems to respond quickly to changing conditions; and robust crisis management protocol with partner networks to ensure a rapid and safe response to such an event.

The solar farm drying out after the deluge. Photo / Lodestone

While more costly than an average solar farm, raising the inverter stations and panel connection boxes high above the ground so the plant could continue to operate in more than 1m of water, turned out to be the right investment choice.

And with the area now basking in later winter sun, the Te Herenga o Te Ra solar farm is pumping out sustainable energy once again.

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