This is one of the sunniest parts of Europe,

and these were two of the first solar towers ever built.

Almost 2,000 heliostats, movable mirrors,

constantly reflect the sun onto the towers, heating up water into steam,

and powering a turbine to generate electricity.

And if you look online,

you'll see quite a few documentaries who've gotten a tour around there,

who've been incredibly impressed by the technology,

and who've been selling them as the future of power generation.

And these are impressive.

Not just visually,

the technology behind them is both very clever and very simple:

it's like bothering your teacher with the sunlight reflection off your phone,

just on a much, much bigger scale.

But there is a catch.

When these were built, Spain was in boom times,

and heavily subsidising solar power.

Investors loved it and piled in with their own money,

companies and researchers were happy to set up all sorts of things like this,

and suddenly the Spanish government had many times the amount of solar power they'd planned for...

and they had to subsidise all of it.

And then the financial crash hit.

The Spanish government cut subsidies.

Not just for the future,

not just for the plants that were under construction,

but even for the plants that were already built

and relying on those subsidies to balance the books.

The industry got cold feet: Spain had altered the deal,

and all the solar companies could do was pray they didn't alter it any further.

Or go bankrupt, one of the two.

This might still have been viable, maybe,

with some more research and development,

and that's what they were trying to do.

But now, the cost of regular,

everyday solar panels is tumbling.

Not mirrors, not like this,

just normal solar panels, the sort that you can fit to your house

or that get put out in massive fields as solar farms,

converting sunlight directly to electricity.

Whether the price of those panels is going to keep falling

depends on which team of researchers you believe,

but it's already cheaper than building a giant tower,

putting in either high pressure water or molten salt for it to heat,

and dealing with thousands of moving parts that all have to line up and track the sun

perfectly

and which might, occasionally, cook a few birds in mid-flight.

Don't get me wrong, this is a great bit of technology on paper.

It combines renewable energy with storage:

if you're heating up something like molten salt,

you can save that power for hours to get you through the night.

And there are other plants like it being built:

there's one nearly completed in the Atacama Desert in South America.

But right now,

this is expensive.

It might not have been,

if history had taken a different track,

if research had poured into these instead of regular solar panels: but as it is,

the future probably isn't quite this bright.