Solar Parking Lots a Good Idea, but Not the Slam Dunk that Some Think

“Why don’t we just put solar on rooftops and parking lots?”
You hear this question a lot – the presumption is usually that if we just covered all available urban space with solar panels, we’d solve our energy problem – and that’s simply wrong, for a lot of reasons.
One flavor of the argument is that we should put solar panels over every parking lot. Great. Let’s do it – but first let’s be aware of the barriers that exist to make it happen.
Simon Mahan is Executive Director, Southern Renewable Energy Association.

Simon Mahan on X:

There’s been a meme running around showing solar carports. Usually, the “take” is we should be installing solar carports instead of using farmland for solar. Here’s the thing: no one is stopping you from installing solar carports. So why don’t we do it more often?

First, parking lots are unusual things. They can be privately owned (a landlord), or publicly owned (city/school/etc.). Public owned lots/garages have to get budget line items through local/state appropriations. Private can go quicker, but still need permits, etc.

Next, regardless of parking lot ownership type, if the lot owner doesn’t have a way to use the solar (like a net meter agreement with a utility), or access to a wholesale market (being able to sell directly into the grid), they won’t recoup their costs.

Net metering policies have been under attack in the U.S. Many states have a cap on the size a project can be, usually well less than 100 kilowatts. That may be enough for maybe 10 houses. That ain’t nothing, but we’re not powering the U.S. economy with that.

Additionally, carports are estimated to cost upwards of $4 per watt. A rooftop system may cost just $2.5 per watt. Meanwhile, a large “farm” based system may only cost $1 watt. Carports must be tall for vehicles, tearing up asphalt is more expensive than dirt. More work and materials.

There are side benefits to carports – increased shading, happy customers. But there’s not great ways for the lot owner to monetize these benefits.

About 3 million acres of parking lots exist in the U.S. It may take 20 acres of parking lots for 1 megawatt of solar. If 100% of parking lots were covered with solar, that’d be 148,187 MW. The U.S. uses 10x that amount of power – 1.3 million MW. We need more power.

Meanwhile, 38 million acres of farmland is used for corn ethanol – fuel. Acreage that requires tons of fertilizers, herbicides, gasoline for harvesting, etc. We’re romanticizing farmland. It ain’t pure/small.10x more land is used for ethanol production than for parking lots!

Don’t misread me: carports are great, but their usefulness is highly, highly specialized. We won’t power the U.S. with parking lots. Farmland is private property, and the local owners are voluntarily leasing/selling their land. It’s a better deal for them.

Back to the meme…the “let’s do carports instead of farms” is from solar opposition groups. They’re not actively advocating FOR carports. Given the opportunity, they’d oppose carports too (eyesore! subsidies! poison!). These aren’t serious clean energy people.

This is all Nirvana Fallacy: that unless something is perfect, it should be opposed. Instead, I propose we let the markets work, let private property owners do with their property as they wish, while also pushing for improvements. This isn’t this/that, it’s yes/and. /fin 

Argonne National Laboratory:

Global insect biodiversity has been in decline due to habitat loss, pesticides and climate change. Restoration of insect habitat paired with smart land use changes toward renewable energy developments could help reverse the course.

For instance, as a carbon-neutral source of electricity, expanded PV solar energy development is critical to mitigating climate change. According to the DOE’s Solar Futures Study, approximately 10 million acres of land in the U.S. will be needed for large-scale solar development by 2050 in order to meet grid decarbonization and climate change goals. But some lands are better suited for PV solar development than others. Disturbed lands such as former agricultural fields are ideal locations to hold rows of solar panels compared to lands that have been previously undisturbed.

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The two studied solar sites were planted with native grasses and flowering plants in early 2018. From August 2018 through August 2022, the researchers conducted 358 observational surveys for flowering vegetation and insect communities. They evaluated changes in plant and insect abundance and diversity with each visit.

“The effort to obtain these data was considerable, returning to each site four times per summer to record pollinator counts,” said Heidi Hartmann, manager of the Land Resources and Energy Policy Program in Argonne’s Environmental Sciences division, and one of the study’s co-authors. ​“Over time we saw the numbers and types of flowering plants increase as the habitat matured. Measuring the corresponding positive impact for pollinators was very gratifying.”

By the end of the field campaign, the team observed increases for all habitat and biodiversity metrics. There was an increase in native plant species diversity and flower abundance. In addition, the team observed increases in the abundance and diversity of native insect pollinators and agriculturally beneficial insects, which included honeybees, native bees, wasps, hornets, hoverflies, other flies, moths, butterflies and beetles. Flowers and flowering plant species increased as well. Total insect abundance tripled, while native bees showed a 20-fold increase in numbers. The most numerous insect groups observed were beetles, flies and moths.

In an added benefit, the researchers found that pollinators from the solar sites also visited soybean flowers in adjacent crop fields, providing additional pollination services.

CNN:

CNN reached out to five of the top US retailers — Walmart, Kroger, Home Depot, Costco and Target — to ask: Why not invest in more rooftop solar?

Many renewable energy experts point to solar as a relatively simple solution to cut down on costs and help rein in fossil fuel emissions, but the companies point to several roadblocks — regulations, labor costs and structural integrity of the rooftops themselves — that are preventing more widespread adoption