The nation’s largest industrial landowner expects the investment will lower costs for local and export firms, and reduce pressure on the national grid at peak times.
Up to 170,000 solar panels are being installed across industrial rooftops over the next decade, creating up to 85MW of solar generation.
The South Otago business, privately owned after being founded by Bruce Stewart and Lance Calder in Milton in 1955, already has solar on 17 industrial sites, capable of generating up to 3.6MW at peak output.
More systems will be phased into over 900ha of zoned industrial land in Auckland, Canterbury, Otago and Southland.
Director Sam Stewart said solar would be installed in all of the company’s new industrial developments.
Most of its existing buildings were expected to be retrofitted within the next year, he said.
Reducing the delivered cost of power could help lower the cost of producing goods for local and export markets, particularly for manufacturers, logistics firms and other energy-intensive occupiers, he said.
‘‘Every percentage point matters when businesses are operating in competitive markets,’’ he said in a statement.
‘‘If we can help reduce one of the core operating costs for industrial occupiers, that ultimately supports lower-cost production, stronger margins and a more competitive export sector.’’
Network losses typically added about 5%-10% to the cost electricity users paid; industrial businesses were paying for more power than they consumed on site, he said.
‘‘If your meter says you have used 100kW hours, you may actually pay for 105kW because of the losses across the network.
‘‘By generating power above where it is used, we can take pressure off the lines network and reduce the cost of moving electricity across the system.’’
More businesses were electrifying transport, heating and production systems.
Industrial roofs had historically been an underused asset, despite their scale and nearness to large power users, Mr Stewart said.
‘‘We build these buildings and the roof is sitting there unused.
‘‘The opportunity is to turn that into a productive asset that supports the tenant, supports the grid and creates a long-term return.’’
Rooftop solar avoided some of the land-use tensions with large-scale ground-mounted solar.
Calder Stewart energy manager Ben Krieble said the company’s model would allow tenants to access cheaper solar power without needing to fund or own the solar infrastructure themselves.
Tenants would continue to buy power from their normal supplier, but received a portion of their electricity from the rooftop solar system at a lower cost, he said.
Some energy intensive tenants were signing up for power price contracts of up to 12 years.
Many businesses operate during daylight hours when solar generation is strongest.
Excess power generated in the summer at some sites would be exported to the grid.
In winter, solar would contribute to daytime demand, with tenants drawing the rest from the grid.
Mr Krieble said the economics varied by site, depending on the size of the building, the solar system and tenants’ energy use.
Battery storage was the next step in improving the economics of rooftop solar, allowing more power generated during the day to be stored and then used.
Batteries could play a wider role by reducing pressure on local lines networks during peak periods early in the morning and around 6pm, Mr Stewart said.
‘‘If power has been stored on site, or batteries have been topped up overnight when electricity is cheaper, that power can be used instead of drawing from the grid at peak times.’’
Mr Krieble said the company’s rooftop solar network could become a form of virtual power plant as soon as battery storage was added at scale.
Calder Stewart is also exploring wind generation at some of its industrial site developments.
