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Solar farms can eat up farmland – but ‘agrivoltaics’ could mean the best of both worlds for NZ farmers

Rural News / opinion
Solar farms can eat up farmland – but ‘agrivoltaics’ could mean the best of both worlds for NZ farmers
sheep
Getty Images.

By Alan Brent & Catherine Iorns*

New Zealand plans to commission about eight gigawatts of solar photovoltaic projects – more than the maximum power demand of the whole country on a typical winter’s day – by 2028, according to the government’s latest generation investment survey.

Eight of these solar farms are already operational and spread across the country. More than 40 are in various stages of development, with the construction of the largest single project, in excess of 150 megawatts, due to start this year.

Solar farms are not without challenges, though. They can use up farmland and change the rural landscape. However, we argue that more efficient farms can integrate solar panels and agricultural production, with economic benefits for farmers.

Given Aotearoa New Zealand’s current solar generation capacity of just under 10 gigawatts, the increased generation is a significant development in the electricity sector and a positive contribution to the 2030 target of 100% electricity generation from renewables.

However, opposition has focused on the potential changes to the rural landscape and the use of productive soils.

This is especially because solar farms are likely to be proposed for fast-track consenting. Infrastructure Minister Chris Bishop has signalled the process will “make it easier to consent new infrastructure, including renewable energy”.

We advocate a suitable option for New Zealand lies in “agrivoltaics” – using agricultural land for both renewable electricity generation and farming.

Addressing concerns over land-use change

In a country where half of its area serves agricultural purposes, land-use change is an obvious concern. The answer may well be agrivoltaics, which is gaining traction globally.

It means using rural land for both electricity generation and agriculture (including horticulture). Large areas of the country have been shown to be suitable for this dual land-use approach.

A map of New Zealand showing land rated for agrivoltaics.
This map shows land considered suitable for agrivoltaics in Aotearoa New Zealand. Author provided, CC BY-SA.

The major benefit of agrivoltaics is the micro-climate created under the solar arrays, with cooler temperatures during warm days and warmer temperatures at night. This results in less heat stress and less frost damage for crops.

Soils also retain more moisture, which means certain crops grow better, even with more shading. Pastoral production has seen the greatest benefits globally because animals are better protected from the elements, need less water and can access pasture in dry conditions.

Solar grazing

The integration of solar arrays with sheep farming is a major opportunity for New Zealand. Indeed, it is common practice to utilise sheep to maintain vegetation between and underneath the solar panels. This is a growing business in its own right, known as solar grazing.

The economics are quite compelling. A case study on a Canterbury farm shows the profitability of the solar assets with an additional revenue stream for the farmer from leasing agreements.

Given the economic worries sheep farmers are facing, this should be a definite consideration.

Sheep standing in the shade under solar panels.
It’s common to use sheep to keep vegetation down between solar panels. Getty Images.

Addressing the hurdles

There are hurdles to realising this opportunity in a just manner. One is the upgrading of the grid to accommodate new generation capacity, estimated to cost NZ $1.4 billion a year until 2030. This figure is largely associated with the required high-voltage transmission network.

Transpower’s net zero grid pathways programme aims to address this issue. However, many of the smaller utility-scale solar assets will be connected to low-voltage distribution networks, which will be a significant constraint.

None of this required infrastructure upgrade is included in the 2024 budget. Lines companies are left to manage this issue. Effectively it means that not all farmers will be able to capitalise on the opportunity. It will be a case of “first come, first served” and a potential gold rush.

Consenting issues

This plays into the reforms of the Resource Management Act currently underway. The Fast-track Approvals Bill is currently going through the select committee and may limit comprehensive consultation with stakeholders and the careful consideration of any implications of solar projects.

A recent notification decision by the South Wairarapa District Council, for example, concluded that a proposed solar farm

is inconsistent with the other activities taking place in the rural (primary production) zone, and as such the amenity values of the rural environment would be adversely impacted.

Conversely, in the context of an application for a solar farm in Selwyn, a decision-making commissioner observed that our resource management system allows for, and even expects, changes in land use.

Whether changes are permissible depends on […] the planning [documents], the consideration of environmental effects and […] balanced judgement as to whether the changes meet the legislative and other requirements.

New Zealand’s national policy statement for renewable electricity generation acknowledges competing values associated with the development of renewable energy resources. But it does not identify how to resolve any conflict.

The protection of highly productive agricultural land is covered by the 2022 national policy statement for highly productive land, and planning officials may view conventional solar farms to be in conflict. We argue that well-designed agrivoltaic systems will resolve this conundrum.

Indeed, the decision-making panel in one agrivoltaic application in the Waikato commented that:

its members have seldom observed a project that delivers such significant benefits with such comparatively few adverse effects.


We would like to acknowledge the contribution Olivia Grainger and Anna Vaughan made to this research.The Conversation


*Alan Brent, Professor and Chair in Sustainable Energy Systems, Te Herenga Waka — Victoria University of Wellington and Catherine Iorns, Professor of Law, Te Herenga Waka — Victoria University of Wellington.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

We welcome your comments below. If you are not already registered, please register to comment.

Remember we welcome robust, respectful and insightful debate. We don't welcome abusive or defamatory comments and will de-register those repeatedly making such comments. Our current comment policy is here.

47 Comments

I would think that it would be relatively straight-forward to return the land back to productive use after the usable life of the solar farm? It's nowhere near as bad as building houses all over it like they did around Pukekohe.

I wonder if they could put it in as part of the consent that the land must be returned back to original condition after the farm is decommissioned? 

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Yes, the decommissioning should form part of the planning/resource consent.

The developer can also set aside funds to guarantee this is done but there may also be an insurance option available.

It is a relatively simple process to decommission the sites as the panels aren't usually driven into the land.  Additional plant such as inverters will sit on concrete slabs.

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There isn't a simple process to decommission the sites. Shipping offshore/under carpet is the only option. These projects shouldn't go ahead unless recycling costs are included and they fund the $32 billion grid stabilisation and distribution bill. It's not easy being faux green.

"End of panel life replacement and safe disposal and recycling has not been accounted for in this
analysis. At present, there are no recycling facilities for solar waste in Aotearoa New Zealand, so
it was not possible to budget a figure for this."

 

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The question was around returning the land to it's original state- a relatively simple process.

Recycling the components of a solar panel, inverters etc is a whole different issue that, I agree, needs solving

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LOL. You would have to be pretty gullible to believe NZ has the economy of scale to "recycle" its solar panels. Pro tip: stripping the aluminium, shipping the panel waste to China and planting some pine trees isn't recycling.

"For example, photovoltaic (PV) solar panels are not recycled to achieve a high material recovery yield at present, and there are no dedicated recycling service providers available in Aotearoa New Zealand. Current recovery outcomes are not likely to exceed recycling of the aluminium frame component which represents less than 20% of a typical PV solar panel by weight. The remaining components, which include glass, silicon cells, and semiconductor materials, such as silver and copper, are either stockpiled or sent to landfill."

https://techcollect.nz/wp-content/uploads/2023/06/E-Product-Stewardship…

"No commercial recycling process can yet recover all these useful materials from a PV panel, and there is no consensus about the best way to achieve that goal, says Meng Tao of Arizona State University, who works on PV recycling. “The recycling technologies we have today are still rudimentary,” he says.

...Unfortunately, old wafers cannot simply be melted and re-formed into new cells. Aside from traces of silver and aluminum, they also contain dopants such as boron and phosphorus, along with a silicon nitride antireflective coating. Removing this contamination is a crucial step toward making PV recycling economically sustainable. Metallurgical-grade silicon, with a purity of about 99%, costs roughly $4 per kilogram. But solar-grade silicon has a minimum purity of 99.9999%—known as “six nines,” or 6N purity—and costs at least eight times as much."

https://cen.acs.org/environment/recycling/Solar-panels-face-recycling-c…

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You've obviously never been in a scrapyard.  Everything(barring steel) goes straight into containers, and overseas. Why should solar panels be any different. 

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Exactly, they are not recycled. "No commercial recycling process can yet recover all these useful materials from a PV panel, and there is no consensus about the best way to achieve that goal, says Meng Tao of Arizona State University, who works on PV recycling. “The recycling technologies we have today are still rudimentary,” he says."

Have you ever been in the third world jungle where charcoal is made and exported to China for silicon manufacture? Ever been in a Chinese coking plant? The irony of felling jungle to make charcoal, and woodchips, to export to China to make solar panels so greenies can virtue signal from their roof.

"Silica is reacted with coal, to yield silicon and carbon dioxide. The process requires significant amounts of electrical energy (10–12MWh to manufacture one ton of metallurgical-grade silicon)."

...75% of Chinese polysilicon production has been implicated as involved with forced labor, and Chinese polysilicon production accounts for 75% of world production, then over half of the world’s polysilicon is being manufactured by companies using forced labor."

https://www.minespider.com/blog/know-the-source-the-polysilicon-supply-…

 

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Is your point that "woke" people who buy solar panels have the same bad impact on the environment and third world living standards as "non-woke" people?

I may have this completely wrong but it really seems you care less about the negative effects of solar panels than you care about the idea of "woke" people feeling smug. If that is the case, maybe just chill out a bit?

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I feel like you are holding solar panels up to a higher standard than for other types of power generation. How recyclable is any other power plant after a 40 year life?

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40 year life? Firstly, next year's storm force winds or a tropical cyclone isn't going to lay waste to a place like Huntly or to a hydro dam. So the life expectancy of solar is extremely unpredictable. Secondly even under best case conditions the service life of a solar farm isn't going to be anywhere close to a Huntly (in operation now for fifty years albeit with many upgrades over the decades) or a Benmore Dam (in operation sixty years now). And of course you don't "recycle" these kinds of traditional power plants because they don't break down like the electronics on solar farms. You steadily maintain and upgrade them. 

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You realise that there are already solar farms in operation that haven't been wrecked by the bad weather last year? It's almost as if they are designed for that environment. And even if you do get a few panel failures, they are very easy to replace. 

If you read the reports from MBIE, the expected lifespan of Huntly is 50 years, even with the refurbs it has received. Have a look at page41 on that report. What happens to Huntly at the end of its useful life?

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If you read the reports from MBIE, the expected lifespan of Huntly is 50 years

You mean another fifty years? So a total operational life span of one hundred years? The Huntly site is a few acres. The place will receive a superficial cleanup in the 22nd Century, any serviceable equipment will be removed and sold, anything worth scrapping scrapped, then the gates will be locked and the buildings left. It's only a couple of hectares of non-farming industrial land after all. 

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Ok if we are gonna take that approach, for a solar farm, you take down the panels, chuck them in a container and lock it.  Job done, the farmland can be productive as farmland again.

Maybe we could store the old panels inside your locked up huntly?

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Heh nice one

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Just don't mention asbestos and PCB's...

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I wonder how many PCBs and other toxic chemicals are used in the manufacture of a solar cell?

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No, read the report.

Huntly PS - (Units 1,2 & 4) - Commissioning date 1982 - 1985 - Projected decomm. date 2035

Huntly PS – U5 CCGT - Commissioning date 2007 - Projected decomm. date 2057

Huntly PS – U6 OCGT - Commissioning date 2004 - Projected decomm. date 2046

 

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And what exactly is your point? Unlike a solar panel, the entire stator/rotor components, iron, copper, magnets etc. on those generators and associated machine parts are all completely straight forward to recondition or recycle. Same with the boilers. Further, each of those turbines will have produced a simply massive amount of energy during its lifetime of operation, on the scale of GWh per day, unlike a solar farm. 

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profile,

These projects shouldn't go ahead unless recycling costs are included. I agree and that should equally apply to all other sources of energy.

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Aside from disposal of the panels themselves, there is significant cost in returning the land to conditions conducive to growing food again.  Removal of metals and herbicides from the soil, then replacement of nutrients lost during the life of the solar farm.  https://craven.ces.ncsu.edu/wp-content/uploads/2022/11/Cost-of-returnin…

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"Given Aotearoa New Zealand’s current solar generation capacity of just under 10 gigawatts"

That's just obviously not true. That's 10 x Huntley! 

 

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There is 47 MW connected to the Transpower network  at the moment. Probably less than that on homes and commercial buildings.

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I worked on farmland solar schemes during part of my time in the UK.

They are a great way of using non-arable land with income for the landowner for the life of the plant (usually 25 years). 

We need to be building more solar in this country but I would suggest the low hanging fruit is rooftop installations 

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SolarDB, your thoughts appreciated.

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Working on roofs is expensive , hence the solar farms are apparently cheaper. Its all very modular, so quick as well. From what I've heard they pay well , sparkies sub contracted at  $80 per hour or so.

The panels have a life of around 40 years , and are 98% recyclable. the reason none have been recycled in NZ until recently , is that reatively few have reached the end of their lives.  

 

 

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Thanks. Agrees with my understanding of the situation.

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 and are 98% recyclable

Please describe how the refined doped silicon is recycled, who does it, and how commercially effective it is to do that. Because I don't think it is.

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Next step is to read the google link - you don't have the app for that? Or are you supporting Colonial Vipers position? Lab scale and pilot scale research is not "98% recyclable".

"A comprehensive review on the recycling technology of silicon based photovoltaic solar panels: Challenges and future outlook

13 March 2024

...An increasing amount of academic research on recycling approaches to PV panels that suggests different technology and policy challenges remain. The present review critically evaluates a range of recycling solutions, encompassing both lab-scale and pilot-scale research, and conducts analyses of their cost and environmental implications.

...PV panels pose challenges in their end-of-life (EOL) phase, becoming hazardous waste for the biosphere after 25–30 years or due to the impact of the aforementioned factors (Aghaei et al., 2022). Projections suggest that e-waste from silicon PV panels may reach 60 to 78 million tonnes by 2050 (Song et al., 2023; Guinée, 2002), with environmental and health risks due to the presence of aluminum, silicon, lead, cadmium, and tin (Tan et al., 2022; Jain et al., 2022). Improper disposal can result in soil and water contamination (Bang et al., 2018), harming the biosphere (Zhang et al., 2023), while the polymers in PV panels release toxic gases (Rathore and Panwar, 2022)."

https://www.sciencedirect.com/science/article/pii/S0959652624011090

https://cen.acs.org/environment/recycling/Solar-panels-face-recycling-c…

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There's one currently being completed close to opotiki.

It's being put on a flood plain of a small river. They've surrounded the land with security fence. It's going to be interesting to see the results of an inevitable flood event pushing debris up against the fence.

Also notable there's extensive pine forests further up the catchment.

One of the reasons it's being put there, as with others, is the presence of a substation very close. I'd suggest for any size solar farm that would be a requirement.

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Very interesting that it got planning/resource consent if it's on a flood plain unless some form of mitigation is involved.

You are right though, proximity to a grid connection is key for these projects 

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The flood volume of the plain is not effected by the overspend modules so there are no downstream flood effects.

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Pine pollen is a bitch on solar panels, really covers them well. 

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I did the flood hazard assessment for that solar farm redcows. It will indeed flood and cause some damage in a 1% AEP flood event. However the panels themselves will be above the inundation level. The main risk is to the inverters so these will be elevated on shipping containers.

You are correct about the substation proximity. It is crucial for the feasibility. 

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I have no doubt about the panel and inverters being high enough. But putting a 2m high netting barrier from one side of the valley to within 50 metres of the other side will have some very interesting effects on the distribution of water and debris. Been a few years since the last decent flood event out this way, must be due soon.

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In my flood assessment I made the assumption the fence would be destroyed and need to be replaced. 

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We also need to consider the security factor here. It wouldn't be too hard for someone to hop a fence, slash some wires with a mate and haul off a panel or two on the ute to sell for cash, which we already see with copper wiring in parts of the country.

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No comments on the viability of farming sheep under these things. Good lambs need well fertilised soil. No value in wool...so its just the value of the lambs. Good luck with that. The first couple of years should go ok. Sheep farming aside...we need more power so thumbs up to whatever we do to create it. 

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There's an article in farmers weekly that covers that. I think what growth they lose in winter, they make up from beneficial shape on summer, so it's about the same as bare land.

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I gather you mean shade. Sorry Solardb...perhaps I didnt explain well. Lambs need quality grass. Perhaps they will figure out a way to do that. But shaded and unfertilised pasture will not grow lambs. You really need to rotationally graze and I doubt the fences required for that will be left or installed. Then of course sheep prefer groomed pasture...not the long stuff that happens in spring and if not hard grazed at sometime will become long and rank. Beef stock are generally farmed in conjunction with sheep to keep it in the condition ....shortish ...that sheep like.  Farming sheep is not for the fainthearted. Little things like finding a lambing ewe in bother would be difficult. And good luck with establishing an unshepherded flock if the media got wind of what that entails. I am not saying farming sheep under the panels cant be done. Its just got plenty of problems.

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Grass growth is ranges from 70% to 110% predevelopment 

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Would would go against 30 years of agroforestry research on pasture shading in this country. The shade will knock out the clover so will urea be added to replace this lost N - not to mention lime, P and K?  It is an heroic assumption that pasture quality, without regrassing, will be maintained over 30 years.

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I thought solar fences look quite promising. Nice production profile better matching peak demand.

https://www.gridcog.com/blog/solar-fence-vs-ground-mount-solar

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Thanks for the link, interesting. 

Yes facing panels east, or west is catching on. Especially with the bifocal panels and cheaper panels.

For an off grid system,  facing a panel or 2 east means getting charge into your batteries earlier,  facing west get a charge later. Better for the batteries,  or possibly allow for a smaller battery Bank.

I think I read one of the northland farms has the panels orientated east west, and flips them between the 2 during the day. But I may have read it wrong.

 

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It is uniaxle and slowly tracks the sun's path through the day.

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In Alaska,  they put the panels on a south facing wall, to stop snow on them, and because of the latitude.

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