Low-footprint wind farms need to be considered in big picture

Onshore wind farms can ‘pay’ for their carbon emissions within 2 years of operation, say New Zealand researchers auditing the lifecycle of the proposed Harapaki facility on the country’s North Island.

That facility is nearing completion and will become New Zealand’s second-largest wind farm generating 176MW of electricity.

While renewable energy infrastructure like on-shore wind has some of the lowest environmental impacts of any form of electricity generation, there is currently a carbon cost involved in building these facilities.

The study led by PhD researcher Isabella Pimentel Pincelli from the Victoria University of Wellington Te Herenga Waka calculates how quickly an onshore wind facility can ‘pay’ for its carbon costs incurred to build and operate it.

According to the lifecycle analysis, Harapaki would have a footprint of 10.8g of carbon dioxide equivalent, per kilowatt hour (gCO2/kWh). Based on NZ’s current energy mix, the 41-turbine facility will likely replace a combined cycle gas facility, leading to a carbon ‘payback’ of under 2 years.

Searching for more savings

This ‘cradle to grave’ assessment echoes similar studies that show most carbon emissions are tied up in the manufacture of wind turbines. A tenth of carbon emissions resulted solely from transporting and installing turbine infrastructure.

“The manufacturing of wind turbines is the primary contributor to the carbon and energy footprints, highlighting a critical area for targeted environmental mitigation strategies,” she says.

That especially extends to turbine blade recycling, says study senior author Alan Brent, who is chair in sustainable energy systems at Wellington.

Wind turbine blades are composites and notoriously difficult to separate at the end of a blade’s lifespan.

Finding feasible ways to recycle the materials used in blades is seen as one of the most important actions that the industry can take to reduce the environmental footprint of wind farms.

Brent also emphasises that viewing the carbon costs of a wind farm in isolation neglects its role as part of a larger system of connected infrastructure, which can include renewable and conventional generation technology as part of a grid.

“We always need to remember that it’s dangerous to start just comparing, or just looking, at these results of a technology in isolation,” he tells Cosmos. “We are looking at energy over the entire year that says nothing about power.”

He points to the variable nature of renewable technology and the need for fallback generation options. He argues that while renewable technology in a grid has a reduced environmental impact, it may rely on carbon-intensive backup, at least until greater storage can be built.

Brent’s group will next analyse the overcall carbon costs for complex electricity systems, like those in NZ and Australia which are bringing renewables online with legacy generation as backup.

“Now we are starting to understand the individual technologies, if we bring it all together, what does that do in terms of the overall carbon for the electricity system?” he says.

“We have onshore wind, we have utility-scale solar, we have offshore wind, and we have distributed small-scale systems. If you bring all that together, what does that mean for the overall carbon system? “Some of our colleagues out of Canterbury are saying that we are probably going to need an order of six to seven times the generating capacity, if we’re gonna go to 100% renewable and electrify everything in the economy.”

The study is published in the Journal of the Royal Society of New Zealand.

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