When critics of solar energy talk about the downsides of the
clean energy, one of the criticisms that always pops up is the
intermittent nature of solar power. The sun only shines for 12
hours a day on average around the world, and the most energy
intensive time is far shorter than that.
So, it's easy to see why a technology like
concentrated solar thermal power
could be appealing to industry observers. Designs like power
towers or parabolic trough designs concentrate the sun's energy
on a point that then heats oil or another liquid, creates steam,
and then turns a turbine to generate electricity. The energy can
even be stored in molten salt to provide power into the evening
But there's a big reason concentrated solar thermal technology
won't be more than a small player in the market, and it's not the
birds these plants are reportedly scorching
Ivanpah Solar Electric Generating System's power tower
collects solar rays from over 300,000 mirrors. Photo credit:
Craig Dietrich via
The driver of solar energy long term
For solar energy to be competitive with fossil fuels it has to
compete economically. That means that a kW-hr of electricity from
a solar plant has to be cheaper than a kW-hr of electricity from
a coal, nuclear, or natural gas plant.
It's on this basis that concentrated solar thermal energy was
at or near the industry lead in 2008 when these plants were
popular and power purchase agreements were around 21 cents per
kW-hr, according to the DOE. But today they're not economically
competitive; former leaders like Solar Millennium are going
bankrupt, and projects like BrightSource Energy Hidden Hills and
Palen projects are cancelled or delayed.
For a cost example, the Ivanpah Solar Electric Generating
System that was recently completed began construction at a
similar time to
Topaz Solar Farm and, as you can see below, cost 29% more per
Topaz Solar Farm
Thin-film solar panels
Concentrated solar thermal-power tower
Cost per Watt
Source: Ivanpah and First Solar.
The table above is even showing a favorable comparison for
solar thermal energy because these projects were both approved
years ago. Since then, the solar industry has seen panel costs
fall over 50%, and according to GTM Research the cost to install
a utility scale system is down 61%. We're even starting to see
power purchase agreements fall below 7 cents per kW-hr, with PV
technology winning those bids.
Source: GTM Research.
There aren't many concentrator projects that have begun
construction or even moved forward in the planning phase in the
last two years, so it's difficult to give an apple-to-apples cost
comparison today. But I would bet that the cost of mirrors,
turbines, and molten salt for energy storage hasn't fallen at the
same rate as thin-film or silicon based solar systems. That's the
core problem for concentrated solar thermal technology.
Small solar installations on residential rooftops are a big
part of the industry's future. Source: SolarCity.
Fighting industry trends
Cost isn't the only uphill battle for concentrated solar thermal.
To build a solar thermal power plant you need to think big. These
are plants you build on hundreds or thousands of acres in the
desert, not something you can put up in your backyard.
That's fighting the solar industry's trend of moving closer to
the demand source with smaller projects, even for utility scale
projects. Systems between 10 MW and 50 MW are now a sweet spot
because they can be built relatively close to demand sources with
standardized designs and are easier to get through the permitting
So, not only is concentrated solar thermal energy higher cost
than traditional PV solar, it's becoming hard to justify plants
that are on the scale of 500 MW, no matter the solar
Intermittent solar won't kill the grid
If you still think there's immense value in the less intermittent
design of concentrated solar thermal plants, there's one region
that shows that intermittent energy sources won't cause the grid
Germany is the closest thing we have to a solar focused
electric grid, so it's like a proving ground for the industry.
The country is a leader in both PV solar and wind, which are both
intermittent. In the first half of 2014, the country got 28.5% of
its energy from renewable sources and as much as 75% of peak
demand is now being filled by renewables.
The surprising thing is that with all of that renewable
energy, Germany also has one of the most reliable grids in the
world. The average German customer had 15.9 minutes of lost power
according to recent data compared to 244 minutes in the U.S. So,
having intermittent energy sources like solar won't kill the
Concentrated solar thermal energy is already on its last
The fact of the matter is that PV plants built with standard
solar panels are now so cheap that they make concentrated solar
thermal plants uneconomical. That's why they've had a hard time
getting off the ground in the U.S. and other places around the
world over the last few years. Most plants that are being
completed were planned and approved between 2008 and 2010 when
the technology was competitive with other solar sources. But the
solar industry changes rapidly and today PV is the future of
solar, not concentrated solar thermal energy.
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Why This Solar Technology Is Already Dead
originally appeared on Fool.com.
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