President Donald Trump has floated the idea of building a "solar wall" on the U.S.-Mexico border.

In a speech to a rally in Cedar Rapids, Iowa, on Wednesday, Trump reaffirmed that the proposed wall would be built and then teased the idea that it could contain solar panels.

"You know, people don't realize we're already spending a lot of money on design, but I'll give you an idea that nobody has heard about yet," the president said.

"We're thinking of something that's unique," he went on to add. "We're talking about the southern border: lots of sun, lots of heat. We're thinking about building the wall as a solar wall, so it creates energy and pays for itself. And this way, Mexico will have to pay much less money, and that's good, right?"

According to reports, the idea of using solar panels on the proposed wall has been pitched by both academics as well as businesses submitting designs for the structure. Earlier this month, Politico and Axios reported that the president had suggested placing solar panels on the wall during a meeting with Republican lawmakers.

"You're the first group I've told that to," Trump said at the rally on Wednesday. "A solar wall – it makes sense, let's see, we're working it out, we'll see. Solar wall, panels, beautiful. I mean actually, think of it, the higher it goes, the more valuable it is."

The potential of solar is considerable. In 2014, the International Energy Agency said that, by 2050, the sun could be the planet's largest source of electricity. According to The Solar Foundation's National Solar Jobs Census 2016, the solar industry was responsible for one in every 50 new jobs created in the U.S. last year, representing two percent of all new jobs.