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Trump's Solar Border Wall Idea Won't Work in the Real World

Donald Trump plugging into a Solar Border Wall | Artwork: Henry Cram/KCET
Donald Trump's vision of a Solar Border Wall just doesn't quite connect with reality. | Artwork: Henry Cram/KCET

Commentary: Pundits reported Tuesday June 6 that Donald Trump, at an Oval Office meeting of high-level Republican leaders, suggested that his proposed border wall incorporate solar panels, the goal being to sell electrical power as a way of funding the Wall's construction.

According to Jonathan Swan at Axios, Trump described to assembled Republican Congressional leaders his image of a solar-paneled Border Wall up to 50 feet high, adding that "Trump told the lawmakers they could talk about the solar-paneled wall as long as they said it was his idea." (Predictably, it's not: a handful of contractors bidding on the wall have already included solar panels in the designs they've submitted to the Department of Homeland Security.)

Here are four reasons that Trump's solar border wall financing idea is a non-starter. 

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1. Covering a wall with solar isn't a great way to generate power.

Fun fact about walls: They're usually vertical. Mounting present-day solar panels on a vertical surface means they'll never generate as much power as they would if they were oriented properly. In order for a solar panel to generate as much power as possible, it has to be pointed at the sun. Along the border, that means mounting solar panels at an angle between 22 and 30 degrees off horizontal, with the north side higher. 

To be sure, vertical solar panels are often acceptable despite their less-then-ideal orientation. On existing multistory buildings with sunny, south-facing walls, where a property owner is trying to incorporate solar panels into an existing design to reduce existing power costs, they can be a great idea. If you're intending to use them to sell power to build the building in the first place, it makes a lot less sense.

And it especially makes no sense if that building will cost $15 billion or more to construct.

At least one contractor has suggested covering a slightly tilted 50-foot wall with solar panels top to bottom. The Las Vegas-based architecture firm Gleason Partners LLC provided Business Insider with some mockups of a Border Wall design incorporating a whole lot of panels that essentially make up the wall, which looks to be tilted at more than 60 degrees from the horizontal. 

Mockup of one design for a Solar Border Wall | Image: Gleason Partners, LLC
Mockup of one design for a Solar Border Wall | Image: Gleason Partners, LLC

Gleason admitted to Business Insider, in reporter Jeremy Berke's words, that "numerous variables — the Mexican border is far from a straight line and light intensity changes from month-to-month — could complicate his calculations." The biggest complication will be cost-ineffectiveness. That's a whole lot of solar panels to buy just to aim them lower than the sun gets in the winter sky, producing a fraction of the power they're capable of.

There are alternatives to having the Wall itself be solar. Instead of installing the panels a few degrees off vertical as in Gleason's plan, you could mount solar panels over the entire south-facing surface of the wall on angled brackets, which would allow the panels to work at peak productivity. It would have the additional effect of providing an excellent infrastructure for climbing, which is presumably to be avoided in a wall designed to keep people out.

You could also cant the surface of the wall to about 30 degrees off the horizontal, and mount the solar panels directly on the surface of the wall. But that would make it not so much a Border Wall as a Border Ramp. While that might be both more humane and aesthetically pleasing, it's not really what the Trump administration says it's after.

Simply attaching solar panels to the Mexico-facing side of the Wall a la Gleason would mean that only a small percentage of the panels would ever be pointed directly at the sun, cutting power generation to a fraction of the panel's capacity. That could be fine if your goal is to generate power wherever possible, but not if your goal is to sell electricity to raise funds for a wall.

2. Even if we mounted solar panels atop the wall, they won't generate all that much power

A potential solution to the mounting problem is to affix solar panels on mounts to the top of the wall along its length, an idea that in fact makes up part of Gleason's design. That would seem to offer a lot of room for power generation. Trump has suggested that 1,000 miles of the border would be fortified with his wall, and a 1,000-mile-long solar facility sounds substantial.

So let's crunch the numbers. A common utility-scale solar panel available these days has a capacity of around 300 watts, and measures 77 by 39 inches. A very common way of aiming these panels at the sun is on racks that hold six such panels, oriented in "portrait mode," in two rows of three panels each, about 14 feet high by 10 wide, depending on the manufacturer.

Border Patrol checkpoint sign | Photo: Jonathan McIntosh, some rights reserved
Advocates suggest the wall could provide power for Border Patrol activities, such as this checkpoint sign | Photo: Jonathan McIntosh, some rights reserved

Let's assume that the infrastructure holding up each of those panels adds an inch of width per panel. (It'll be more than that, and more on why in a minute, but we're trying for an absolute best-case scenario here.) 1,000 miles divided by 40 inches means 1.584 million panels along the top of the wall. If the panels are stacked in two rows, that's just under 3.2 million 300-watt panels.

That's a total generating capacity of around 950 megawatts. Sounds like a lot but it's actually less solar power capacity than you find in the often-cloudy state of North CarolinaCalifornia has more than that just on residential rooftops. 

In reality, the wall's solar output will be significantly less than that even with six-racks lined up along its 1,000-mile length. Most of the wall wouldn't let the racks be installed right up against each other, for instance. For one thing, there'll need to be gaps in the array every so often to allow electricians and other workers access to both sides of the panels. 

The cheek-by-jowl approach also works only if the 1,000-mile wall faces due south along its entire length. But it wouldn't, unless it started in San Diego and ended in the western outskirts of Abilene. The U.S.-Mexico border wanders more than 700 miles north and south on its way from Tijuana to Matamoros. In some places, as between Yuma and San Luis or along the New Mexico line, the border runs almost due north and south. 

That's important because in order for solar panels to be aimed more or less at the sun, they'd need to be spaced more widely on stretches of the wall that don't run due east-west so that they don't shade their neighbors. Atop stretches of the wall that run north-south, 15-foot-high solar racks would need to be spaced at least 30 feet apart if they're going to generate power in winter. And fewer panels per mile of wall means less power output.

Another pesky detail: Photovoltaic panels tend to produce power most efficiently when the ambient air temperature is around 75 degrees F. There are plenty of places along the border where summer temperatures are never that low, for months on end, unless it's either raining or night time. Excessive heat can cut power production by between 10 and 25 percent in normal circumstances, and more when the thermometer reaches above 120°F.

Solar panels in the California desert | Photo: Bureau of Land Management
Solar panels in the California desert | Photo: Bureau of Land Management

Panels need to be cleaned regularly, or else accumulated dust cuts down power production. (If the border is anything, it's dusty.) Panels and their associated electrical components fail and need to be found and replaced. Theft or vandalism of panels is a near-certainty, and those panels will need regular replacement. 

And even in the best circumstances, the amount of energy a solar panel puts out is significantly less than its rated output capacity. In the border states, you can usually count on about 27 percent of that output in a typical hour, when you account for things like clouds, seasonal variation, and the fact that the sun goes away every day.

Under our best-case scenario with a 950-megawatt capacity solar array atop the Wall, and no losses due to shading, heat, or other issues, our Border Wall would generate around 2.25 terawatt-hours of electrical power a year. Again, that may sound like a lot, but it's less than one percent of the power California used in 2014. The wall wouldn't generate enough power to run Rhode Island. Or Jamaica. in 2015, the city of Anaheim used 2.4 terawatt-hours of electrical power in its homes, stores, factories, theme parks, and infrastructure. That's more than our Border Wall solar design could generate even under the best circumstances.

Of course, you could increase output by making the canted solar canopy larger, but as we will see, that merely introduces a new set of complications.

3. Best case-scenario: solar panels would pay for a tiny fraction of the wall's cost

In 2015, power generated by large solar facilities sold at a national average of five cents per kilowatt-hour. Solar power is getting cheaper each year, and will likely continue to do so, but let's use the 2015 figures because the math is easier.

At five cents per kilowatt-hour, a.k.a. $50.00 per megawatt-hour, the 2.25 terawatt-hours per year our best-case scenario Solar Border Wall would generate brings in a maximum of $112.4 million dollars a year.

Memorial crosses on the wall at Nogales, Sonora | Photo: John McIntosh, some rights reserved
At today's electricity prices, you'd need more than six gigawatts of solar just to pay to maintain the existing border fence. Memorial crosses on the wall at Nogales, Sonora | Photo: John McIntosh, some rights reserved

Sympathetic Republicans such as Mitch McConnell have suggested that the cost of building the Border Wall would be around $15 billion. At $112 million dollars a year, it would take those unrealistic best-case scenario power sales 133 years to pay for the wall, not counting compounding interest. A more likely estimate for construction costs would be $25 billion or more, increasing the pay-off period to 222 years, again not counting interest. A Politico analysis of border barrier maintenance suggests that a fence the length of Trump's Border Wall would cost $750 million per year to maintain. That's almost seven times what our Solar Border Wall would generate each year, and Wall maintenance is likely to be significantly more expensive.

4. You have to buy the panels in the first place, and it'll take a decade or more to pay them off.

A clever designer might come up with ways to add more solar generating capacity to an effective wall, helping to reduce the problems we've listed so far. Technology might increase the efficiency of solar panels so that they could generate more power when mounted vertically and facing northeast. But there's an issue that neither clever design or technological breakthroughs will likely remove: Sunlight may be free, but those solar panels aren't. Panels cost money to manufacture, to transport, to install, and to connect to the grid.

This is an issue every homeowner who's bought solar panels has had to figure out: how long is it before the panels start to pay for themselves? In areas where the retail cost of electricity is very high, panels can pay for themselves in less than five years. Most places, though, it's more like a decade.

That's in the retail market, where the panels only need to be cheaper than whatever your power company charges its customers. The Solar Border Wall would be selling its power on the wholesale market, providing far less return than those retail residential panels. And that means those panels will take a lot longer to pay off.

Art on the Border Wall in Nogales, Sonora | Photo: Jonathan McIntosh, some rights reserved
And then there are the other costs of building a wall. Art on the Border Wall in Nogales, Sonora | Photo: Jonathan McIntosh, some rights reserved

This week, analyst Ben Gallagher at Greentech Media estimated that utility-scale solar installations will cost around $1.50 per watt by 2020, a significant drop from the present day.

We'll do Donald Trump a favor and figure the costs of his 1,000-mile solar array as if it was a plain-vanilla power plant with all the panels in the same few thousand acres, ignoring the costs of building transmission and substations and designing mounts capable of sitting in the sun for years at 125°F and all those special costs likely to come along with an extremely complicated project along 1,000 miles of border. 

At $1.50 per watt, the 950 megawatts of solar panels we've envisioned for the Solar Border Wall would cost more than $1.42 billion dollars.  With annual power sale revenue at an overwhelmingly optimistic $112 million per year, it would take 12 years and change just to pay for the panels. 

A larger version, as in Gleason's plan, would cost proportionately more. You can add more and more panels to the design, but the time it takes to recoup that investment won't change all that much. In fact, adding more panels might make things worse, as you'll have more power to sell and that could cause prices to drop.

To sum up: Putting solar on the Border Wall could make the Wall less effective. It won't generate that much power, would cover leas than one percent of the Wall's construction costs per year, and would take at least three Presidential election cycles to start showing a profit. 

In other words, Republican legislators would be well advised to take the Donald Trump's advice and tell everyone who'll listen that this was his idea, not theirs.

Banner: Art on the Border Wall in Nogales, Sonora. Photo: Jonathan McIntosh, some rights reserved

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