Solar technology has proven a green energy game-changer. But… how can we best utilize it even when the sun isn’t shining?
One proposed solution is Solar Thermal Energy storage.
Unfortunately, one of the biggest projects that aimed to legitimize this technology, Nevada’s Crescent Dune, ended in utter failure, leaving skeptics to doubt the technology’s future.
What exactly went wrong with Crescent Dune? Is it the end of solar thermal plants altogether? And what can future projects learn from this one epic failure?
We thought these questions deserved a deeper dive today on Two Bit Da Vinci.
Crescent Dunes officially went online what seems like ages ago, but it was only 2015. Startup energy venture SolarReserve, backed by a handful of renewable energy investment groups and a sizeable bump from the US government set out to develop4 what was promised to be a truly remarkable breakthrough in energy production and storage. (Energy.GOV, 2011) (Grupo COBRA, 2016) (Real Engineering, 2021) (SWFI, 2020)
The project was not merely another solar farm using traditional PV panels, but a Concentrated Solar Power Plant with a central receiver tower and advanced molten salt energy storage technology.
What makes this kind of power plant different? Remember when you were a kid and you would use a magnifying glass to burn patches of grass, ants, or your younger brother’s arm hairs? (I still haven’t recovered from that…). A CPS Power Plant takes that idea and amplifies it but, like, 10,000… literally.
The Crescent Dune Plant was located about 200 miles northwest of Las Vegas. It featured over 10,000 moveable,motor-driven mirrors, called heliostats. Each heliostat is made up of 35 6×6 feet (1.8 m) mirror facets, yielding a heliostat overall usable area of 1,245 square feet (115.7 m2). Total solar field aperture adds up to 12,882,015 square feet (1,196,778 m2).
Each one of these mirrors is fine-tuned to bounce incoming solar radiation to a mathematically precise angle so it hits an exact spot on top of a tower containing a molten salt battery — more on that in a bit.
With these systems, all 10,347 mirrors are reflecting sunlight at pretty much the same spot. The combined concentrated solar energy can reach temperatures upwards of 1,050 degrees Fahrenheit (565.5556 Celsius)!
Because of their concentrated nature, CSP Solar Thermal Plants can capture an incredible amount of energy. Compared to traditional PV farms, CSPs are generally considered to be more efficient, operating between 30 and 40% efficiently and capable of producing 10s to 100s of megawatts of power. https://www.umasolar.com/blog/solar-thermal-vs-photovoltaic/
Crescent Dune boasted an installed capacity of 110 megawatts! (Energy.GOV, 2011) (Grupo COBRA, 2016)
But what sets these systems apart from traditional PV farms is that they also have mechanisms to store the energy they produce.
Instead of converting solar energy into electricity, CSPs convert solar energy into thermal energy which then gets stored in the molten salt core inside that 640-foot-high central tower. Once it’s melted, the salt moves into a storage tank, where it gets used to produce steam. That steam moves turbines which then produce electricity so that the folks in Vegas can spend hours playing the slots. Just one more pull, and I know I’m gonna win BIG!
The energy can stay stored in the molten salt there for up to ten hours. Once used, it can be cycled back through the receiver for reheating. The huge benefit here is that it allows the plants to harvest solar energy during peak sunlight hours, then dispatch baseload energy to the grid when sunlight isn’t available. In theory, this eliminates the need for peaker plants that rely on fossil fuels like natural gas. (Energy.GOV, 2011) (Evwind, 2020)
The prospect of Crescent Dune seemed so exciting, that the US Department of Energy gave it its full support, including some financial backing to the tune of over $500 million. Initially, the plant was expected to produce over 40,000 MWh every month, and over 480,000 MWh annually. (Leitch, 2018) (WSJ Editorial Board, 2020)
But… almost as soon as it went online… the cracks began to show.
From the get-go, construction delays offset deadlines by several months. Then, by the time it finally got up and running in September 2015, the plant only operated for eight months before it had to shut down due to a leak in the molten salt storage system. Which is basically like a flood of [https://youtu.be/8MYAFfeNO00?t=4 Dr. Evil saying “Liquid Hot Magma”] Yeah… not good. (Chamberlain & Sayles, 2020) (NREL, n.d.)
Even once all of that was sorted, by 2018, the average capacity was only around 20.3%, compared with the original projection of 51.9%. (Chamberlain & Sayles, 2020)
At its peak production in May 2019, the company only achieved about half of its original production goals, and only for about 9 months.
Regular outages and equipment failures eventually lead the plant’s sole buyer, NV Energy, to pull out of the arrangement, telling regulators that the project posed “the most significant risk” to its ability to meet its renewable portfolio goals. Ooof… that’s like when your S.O. dumps you in middle school then goes around trash talking you to everyone in your class.
Before the end of 2019, the plant officially ceased operation. (Real Engineering, 2021)
So what exactly went wrong with Crescent Dune? And what does this signal for future green initiatives?
While CSP technology boasts some benefits over other forms of energy, particularly traditional PV technology, CSP is still very much in its early phases of development.
One major factor is cost. When the technology began to debut around 2009, concentrated solar power cost per megawatt was extremely competitive compared with photovoltaics. However, over the last decade PV prices have dropped significantly,
Now, its much harder for newer, less established technology like CSPs to compete. By the end of its run, Crescent Dune was costing NV Energy $135 per MWh. 1! 3! 5! — Compare that to the roughly $30 per MWh available from a PV farm located in the same area in Nevada — it just made no financial sense. (Leitch, 2018)
It is worth pointing out that to get a better picture of the price, we need to factor int he dispatchable nature of Crescent Dune’s power. A truly levelized cost comparison has to include capacity payments for generating capacity available to supply power during peak hours. Doing that, low-to-high hourly wholesale electricity prices have been shown to vary by up to four orders of magnitude. (Joskow, 2011)
But being that the power wasn’t even always available at peak deman hours… it still proved to be a far greater liabilityfor the utility company.
So does Crescent Dune spell the end for Solar Thermal Energy — one more casualty in the growing list of failed green initiatives from the Obama era?
Well, not quite. While Crescent Duane has helped steepen the hill CSP technology already has to climb, the technology as a whole is not out of the fight just yet.
New designs include alternative welding practices and improved methods of relocating hot and cold salt pumps to reduce the need for longer pump shafts and reduce downstream infrastructure costs, which could help make CSP technology more accessible.
Endeavors like China’s Supcon Solar have exceeded its six-month output targets at its Delingha tower in Qinghai province. (Chamberlain & Sayles, 2020)
Brightsource’s solar thermal system in California’s Mojave Desert currently sits as the largest solar thermal plant in the world.
And while Crescent Dune ultimately failed, data mined from its collapse is continuing to inform current and future projects in hopes to make the technology more reliable and cost-effective.
But what do you think? Is CSP technology going to be the solar wave of the future? Should the US government place itself in the position of playing benefactor on new green technology at the taxpayers’ expense? What other green energy production storage technology are you excited about? Sound off in the comments below!
