Wednesday, July 6, 2022

Power to the farmers

Power bills can be a headache for farmers, especially when it comes to running an irrigation system. Anne Hardie talked to a Golden Bay farming family who have come up with a solution that not only covers the bills, but generates some extra income for the family business. A small river running through the Harwood family’s farm in Golden Bay is driving their own hydro-electric power station to run an irrigation scheme as well as exporting excess power to the local power company. In a purpose-built shed by the Waitui River in Upper Takaka, a single Francis turbine is fed water when the farm is not irrigating and that helps offset power usage. The pipes are already set up in the shed for a further two turbines to be installed once Network Tasman’s substation down the road is updated, and that’s expected in a couple of years. It’s the latest development in a business that farms 2432ha of land with dairy cows, beef cattle, deer and sheep in a balance aimed at making the most of their resources. Nigel Harwood is the general manager of the operation which milks 850 cows on around 250ha. His brother Jon manages the drystock operation including 1100 hinds with all progeny finished, 3300 ewes and 500 beef. Meanwhile, their father Dave runs a lamb and beef finishing property on the northwest coast. All up, the drystock part of the farm winters 700 cows/year. It’s a regime that benefits each segment of their business and when they looked at irrigating the dairy unit, they included a 23ha pivot and 30ha of K-Line irrigation on the drystock farm. This meant they could grow more grass through autumn for the cows to winter on, but also to finish weaner deer and lambs. Golden Bay is normally associated with high rainfall, but although Upper Takaka gets heavy doses of rain in the lee of the mountains that separate it from the West Coast, summers are dry. It’s a climate Nigel likened to Canterbury, with southwesterly winds drying off the land in l

 

Expanding irrigation

This turned the focus toward centre pivots because, unlike many farms in Golden Bay and Nelson, they had suitable space for them to travel.

"I've always been a real fan of pivots because they're a far more efficient form of irrigation," Nigel says.

Now they have six pivots of various ranges irrigating 160ha as well as 40ha of K-Line, and instead of producing 720kg milksolids (MS)/ha, they've leaped to about 1350kg MS/ha. They could have had fewer but larger pivots and chopped $300,000 from their initial cost, but Transpower pylons travel through the farm.

Though the Takaka River runs alongside much of the farm, it can be unreliable for irrigation in late summer due to the Cobb Hydro Station further up river generating on the spot market. This means the irrigation can be off for six to 10 hours/day and all weekend. The hydro station feeds off the Cobb Dam higher up in the Kahurangi National Park, so even in very dry years the station generates most days.

On one hand, the hydro station ensures the Takaka River always has enough water through summer for consent holders. But on the other hand, its on-off generation pattern makes it a challenge for those wanting to irrigate.

"The real key to irrigation is reliability and the Takaka River was unreliable because right when you need it, they generate power for the spot price."

Hydro opportunity

So when an ex-hydro worker mate of Dave’s talked about the possibility of building a power station on the smaller Waitui River running through their farm, their ears pricked up. Here was a chance to not only get water to the dairy farm, but possibly cover the farm's power costs as well.

The idea was developed and after two years in the resource consent process, the power station was completed in time for this season.

The station is being built in two stages, with stage one including an intake up river leading to a settling pond to remove sediment before the water travels 1.8km to the pump shed. Near this point, a tee in the line has been inserted and another 750mm pipe laid to the hydro station. Water is delivered by gravity to the irrigation pumps in a 400mm PVC pipe that feeds at 90 litres/second. If the irrigation is not being used, the meter is used to generate 28kW, which is about the size of the vacuum pump motor in the shed.

So when the farm is not irrigating, the water goes through the turbine to create power. While it's a small amount of power generated, it means that they’re milking, they’re importing 2-5kW and when the vacuum pump is off, they are using 10-15kW through the fridge unit or for hot water heating. That leaves 10-12kW being exported. And when the dairy is off, they can export 26-27kW.

At this stage, the scheme can't operate when the irrigation is running as the pipe is too small to provide water to both hydro and irrigation.

When they're ready for the next stage with two more turbines, a 1000mm pipe will be installed and travel 2.2km from the intake to the hydro station which will then be capable of producing 450kW of power. The addition of another pipe will allow for both generation and irrigation water at the same time.

Nigel's conversation is sprinkled with kilowatts these days and they've become part of the farming business that could generate around $200,000 of income when the scheme is completed.

"When we're milking, we're currently buying in up to 10kW and then we switch the dairy off and start exporting 26k,” he says. “And then at 8.30pm we have hot water heating come on for seven hours and at the same time I'm exporting 10kW. And when the water is up to heat we're up to 26kW."

The scheme uses 170kW/hour when the irrigators, dairy and effluent systems are all running and that adds up to about $50,000 for the annual power bill. Nigel estimated about half of that will be covered by stage one of the hydro scheme that is in place now.

Local network

When three turbines are up and running, the hydro station will have the capacity to supply enough power to cover the irrigation demands for several dairy farms covering half the Takaka Valley and that's when it should generate around $200,000. Interest on the investment cost will initially take about half of that income.

To date they have invested about $500,000 on the hydro scheme and they anticipate spending a total of $1.6 million by the time the three turbines are churning out power.

"Hydro is a large investment and as long as you get the capitalisation right it's okay, but it's not lotto,” he says. “You have to know how much they're going to generate and that's your income which has to cover your interest and running costs.

"So far it's doing exactly what we thought it would do, so we're pretty confident that if we put the next big pipe in, it will do about 450kW. But even now it's a neat wee system. Even though we're not generating a lot of power yet, what we're earning for that power is quite high."

In dry years when the southern hydro lakes are low, it will earn even more, as the cost of power will be higher.

"The advantage of hydro is that it's just going to sit here and do it. And it's a system that can be controlled from a laptop anywhere around the world.”

The hard part was tackling the barriers placed in front of them by the Resource Management Act (RMA), yet environmentally, small hydro schemes made sense in river valleys throughout New Zealand to supply part of the local power needs, Nigel says.

"A much higher emphasis on economic impact would bring balance to consents. The RMA is adversarial all the time."

Local power schemes could also benefit local areas when there was a loss of electricity through transmission. However, Nigel says power companies often didn't have the lines and infrastructure in place to import power from small hydro schemes like their own.

After overcoming the hurdles, they now have a scheme that provides reliable irrigation for the dairy unit as well as part of the drystock land with 11 soil monitors placed under the pivots to make efficient use of that water. The monitors run from 50mm deep to 500mm and 10m in length, while one remains at 50mm for 10m. The goal is to ensure water from the irrigation does not reach 500mm.

Information from each is radioed to the dairy where they could watch the soil moisture on an hourly basis if they wanted. It gives them precise details so they can react accordingly.

"So you switch on earlier and switch off earlier," Nigel says. "It cost $25,000 to put the monitors in which made me snort a bit, but I think they've really proved their worth. It's very, very easy to turn it on too late otherwise."

Irrigators are now turned on around October 20, whereas it used to be toward the end of November. Usually they turn the irrigators off around March 10, though they have irrigated to May 15 in a very dry season.

That water has been invaluable for production and the dairy unit now reaches 340,000kg MS on a largely grass-based system.

"I see irrigation as NZ's real ace in the hole, as far as doubling production and providing certainty in droughts."

Nigel Harwood and the farm's first turbine.

Managing multiple priorities

The Harwoods’ diversified farming business is all about scale and diversity.

The milking platform for the dairy cows covers the valley floor, while deer under the direction of Jon spread over some flats and through the medium hill country, finishing weaners from the 1100 red hinds. On the near-vertical slopes that rise above the valley to rocky tops, the 3300 breeding ewes are left to their own devices at lambing, with just the scanned triplets brought down to the flats where they are closely watched and fed grain if needed.

"If she can get those three lambs on the truck, they're probably worth about $70 each if they're fed well and the genetics are there," Nigel says.

The result of a 140% lambing, plus another 2000 bought in each year, add up to around 7000 lambs that travel to the Harwoods’ remote property on Golden Bay's northwest coast. At the beginning of the following spring, the tail end of those lambs are finished on the irrigated drystock block and all are gone before they cut their hogget teeth.

On top of that, another brother, Simon, sharemilks 900 cows for Manuka SA in Chile. It's been hard work in a different culture, far from New Zealand, Nigel says, but was going pretty well now.

Added into this farming mix are beef-cross calves from the dairy unit. Nigel says they targeted 120 Hereford/Friesian calves each year that headed to the coastal farm before Christmas, when all the lambs from the previous year were gone and feed was plentiful. A number resembling Friesian bulls are left entire and carried as long as three years to finish. To finish them earlier, they have been considering feeding supplements so the cattle don't drop weight over winter. It's a rugged climate on the coastal block that misses out on spring growth because of wet, cold weather and then grows consistently through the summer months. It's a valuable part of the family's farming business as it adds diversification and provides summer-safe country to the drystock operation if needed.

"Our business plan calls for scale and diversity, so any more than 850 dairy cows means we start taking more land off drystock which we want for diversity."

Working together

While each family member has their own section to govern, they all plan together for the overall business and use the land and stock for the best results. The drystock operation provides winter silage, winter grazing and raises young stock, while beef cows will sometimes run behind the milking herd instead of topping the paddocks.

It's also why the irrigation includes 21ha under a pivot and 30ha of K-Line on the chunk of deer farm used to winter the cows and finish other stock.

Between June 1 and the third week of July, the dairy cows will chomp through about 600,000kg drymatter (DM) on the drystock block that includes about 20ha of rape or kale, about 100ha of late spring silage and about 100ha of pasture.

Weaner deer follow the dairy herd and by September the last of those have left the property in time for paddocks to be locked up for silage.

"It works surprisingly well wintering the drystock on the same block as the cows," Nigel says.

Most of the silage is cut on the drystock area in late November which was not such good quality, but bulk silage for winter. The only silage cut on the milking platform was to retain pasture quality.

They're still allocating costs to different aspects of the business as it's complicated by the multi-use of the land, but it's clear that irrigation has boosted milk production dramatically and part of that is being able to carry 3.3 cows/ha.

Wintering and cutting supplements on land that benefits from irrigation is a bonus and means the only bought-in supplement is 200 tonnes of palm kernel/year that is fed in bins towed into the paddocks. It's fed just when the cows need it, depending on the season, and finishes around the end of September when the production returns to a purely grass-based system.

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