Chatham Islands fishing outfit uses freezer as a solar battery

A Chatham Islands seafood company has found a novel way of using excess energy from its solar panels to save money - a “reverse heat battery”.

The Chatham Island Food Co (Food Co) catches blue cod, kina and paua from around the islands, then snap freeze them before sending them to the New Zealand mainland.

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During the COVID-19 pandemic there was significant pressure on the business, when demand from restaurants completely disappeared.

This led Delwyn & Gigi Tuanui (Food Co founders) to starting supply consumers directly through an online store - as well as looking for other cost savings.

Power prices were a major issue, with the cost of diesel – which powers the island’s electrical grid - rising substantially.

In response, Food Co took a Business Green Loan from ANZ in 2022 to install a 32-kilowatt solar power system on the roof of its factory in Owenga.

It was the first such loan issued by the bank and company co-owner Geoff Creighton said installing solar panels made financial sense - and has since saved the company thousands of dollars per year.

“Diesel prices were going up and up - we were paying almost $1.30 for a unit of power, while it was about 20c in mainland New Zealand,” he said.

“The actual payback on putting it in was quite compelling.”

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Setting up the system took some time, and the Food Co partners wanted to make sure it was resilient, as replacement parts and technology are difficult to source on the island.

"New Zealand's always struggled with the tyranny of distance with our markets, and the Chathams take that even further," he said.

"You have to be really well organised with your suppliers and requirements to run a business there, and you need equipment that can mostly be repaired with a spanner - people in the Chathams tend to be pragmatic problem solvers."

Food Co’s solar system didn’t include a battery, and the power system on the Chatham Islands doesn’t allow energy to be sold back to the grid.

This meant Food Co had to come up with an innovative way to use excess power from the solar panels.

They worked with refrigeration consultant Perry Hutchinson from Pacific Energy, to turn their commercial freezers into a “reverse heat battery”.

The freezers normally operate around -26C, but “when you are getting that excess solar, you can take your freezer down much, much lower – as low as -40C,” Geoff said.

When solar power production halts overnight, the freezers switch off, and are then allowed to slowly drift back up towards -26C, saving the company electricity.

Mains power is switched back on when it reaches -26C and it is kept there until morning, when solar power production resumes and takes over.

The technique works well with the company’s award-winning main product – frozen Chatham Blue™ cod fillets.

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Geoff, a fishing industry veteran, says blue cod is one of the few fish which is resistant to the flavour or texture-destroying effects of freezing.

“It actually improves from freezing it," he said, "when it's processed and frozen so quickly, you're locking in that just-caught flavour straight away.”

In recent months, Food Co have taken a second Business Green Loan to add even more solar panels to their roof, to power its new line of automatic filleting machines and staff cabins.

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With solar now installed and auto-filleting capabilities underway, Food Co also found it now had time to freeze the fish frames so they can be sold as bait to crayfishermen on the island.

This simultaneously generated another revenue stream, while also reducing their waste output, and lowering the overall carbon footprint by no longer needing to import bait from the mainland.

The company’s entire solar power output is now around 50 kilowatts, with Geoff saying they have plans to undertake a third phase soon, when even more panels will be put on the roof of its old factory.

Food Co’s solar investment forms part of a growing trend - New Zealand businesses that are increasingly looking to reduce long-term costs while also preparing for climate change, with many of them using loans like ANZ’s.

“It’s great to see customers like Chatham Island Food Co doing innovative things like this with our Business Green Loan – it’s good for them, and for the environment,” ANZ New Zealand Managing Director Business Lorraine Mapu said.

“Supporting customers as they adapt to climate change continues to be a priority for us - in particular, helping them invest in their business in ways that will make them more resilient in the future.

“About $43 million in Business Green Loan lending has been approved since the loan was launched in September of 2022.”

Meanwhile, Geoff’s advice for other businesses looking to go down a similar path is simple: do your research.

"It's not as easy as just whacking up a solar system - when we first looked at it, we thought there were quite a lot of expenses, on the technical side - but those have paid off, and we haven’t had any issues with it,” he said.

"Do your research and work with good people."