Abengoa building on storage expertise in smaller Palen proposal
Abengoa is now evaluating a new design that could reduce proposed capacity but plans Palen as a single tower including thermal energy storage.
After 4 years, the 500 MW Palen tower project being carefully shepherded through California’s exacting solar permitting process by BrightSource Energy and Abengoa as Palen Solar Holdings (PSH) was unexpectedly withdrawn in its final iteration two months ago.
Before backing out, PSH had received a provisional approval to build one 250 MW tower first, and then to separately attempt to permit a second tower - only on condition that it includes storage.
When PSH bowed out most unexpectedly after getting a conditional approval, but too late for the 2016 completion that would allow investors to take a short lived investment tax credit, BrightSource spokesman Joe Desmond made a comment that has turned out to be prescient.
“The project technically is still active at the federal level. It’s a good site for solar DNI, it has access to transmission, and it's adjacent to another solar project, so it's a good location,” he said then. “So I’m sure there will be an opportunity in the future. Hopefully sooner rather than later.”
Storage experience
Abengoa’s new proposal builds on the company’s experience with thermal energy storage at their 280 MW Solana project supplying Arizona Public Service (APS) with 6 hours of storage.
“We worked closely with Abengoa on making sure that the plant isn’t just running at full production, but that it’s running at the times that we want it to,” says APS spokeswoman Jenna Shaver. “Our peak is typically between 4 and 7 at night when our customers are getting home at night and starting to turn on the oven, the heater, the A/C in the summer.”
The announcement comes just as the company’s 280 MW Mojave CSP project is about to come online near Barstow, California. It is possibly the last CSP plant Abengoa builds without storage.
Most of Abengoa’s CSP projects include storage - 3 hours at Khi Solar One in South Africa, 4.5 hours at the 110 MW trough at Ashalim project in Israel, and 17.5 hours at the 110 MW tower at Atacama in Chile. Its bids for Morocco’s Noor II and III include storage too.
“Large-scale storage systems can provide many hours of full load capacity for base load and peaking applications, which makes this technology highly manageable, enabling it to supply electricity in a stable way, 24 hours a day,” Abengoa tells CSP Today.
“With storage, we can respond to electricity demand at any time, adapting production to grid electric power demand profiles, independently of the presence of the sun and the time of the day or night.”
Abengoa already supplies most US storage after pumped hydro
Pumped hydro accounts for most US energy storage. Surprisingly, Solana supplies the next.
The 1,680 megawatt hours of thermal energy storage at Solana actually accounts for the most storage in the US after hydro, according to Chet Lyons, Principal of Energy Strategies Group (ESG).
“I was surprised when I looked at this,” says Lyons. “That is a large amount of megawatt hours, when you compare it to the current production of battery-based stationary storage. Just that one plant. These are not little toys. These are big giant things.”
US thermal storage will almost double in early 2015 when SolarReserve’s smaller 110 MW Crescent Dunes project comes online with 11 hours of storage. Its more efficient technology provides more storage relative to capacity, providing 1,210 megawatt hours of storage.
“We directly capture and then store solar energy in molten salt at 1,050º F. Solana captures the energy in oil and then transfers the heat for storage in molten salt at 700 to 750º F,” explains CEO Kevin Smith.
“The salt freezes at below 500º, so they’ve got a relatively tight and less efficient differential from 500 to 700º F for collecting the energy, whereas we have from 500 to 1,050º F - giving us two and a half times the storage capability per pound of salt.”
But even with trough, storage demonstrably adds capacity factor. Solana generated 89,248 MWh in its first quarter, 111,128 MWh in its second, and 203,777 MWh in its third quarter.
Solana offtaker APS said early this year that they were very happy with the performance. The utility especially appreciated the ability to get power at odd hours such as before sunrise next day, on demand. APS recently asked regulators to require energy storage in lieu of at least 10% of planned peaker capacity.
CSP with storage cheaper than PV with batteries
“Power grids need extra generating capacity to work properly. For example, about 20% of New York State’s generation fleet runs less than 250 hours a year,” says Lyons.
“Because they don’t run much, “peaker plants” are by design the cheapest and least efficient fossil generators. When they do run they cost a lot to operate and produce more air pollution than other types of fossil generation.”
Lyon’s white paper, Guide to Procurement of Flexible Peaking Capacity: Energy Storage of Combustion Turbines notes the CAPEX for a 4-hour peaker amounts to $348 per kilowatt hour of installed capacity. He predicts that batteries will provide cheaper storage than simple cycle peaker plants by 2017 or soon thereafter.
“CSP thermal storage is more than an order of magnitude cheaper when compared to the benchmark, which is chemical batteries,” Lyons points out.
“Depending on location, battery energy storage on a per kilowatt installed basis might be more like $500 compared to $15 per kilowatt of installed capacity of solar thermal storage.”
Abengoa says that storage was a key consideration because it provides not just dispatchability - but also cost savings.
“An increase in storage capacity can result in lower generation costs, so storage is also a relevant component in determining the cost of our plants,” a company spokesman explains.
“Storage adds value for grid operators. Solar thermal power plants can be easily integrated in grid systems because they can deliver highly dispatchable electricity using thermal storage systems.”
New permitting for Palen
Aspects of the new Palen tower CSP project would not need new permitting. The site is on a 100-some mile stretch of Riverside County’s Hwy 10, about equidistant from Blythe at the Nevada border, and from the Indio at the other end across from Joshua Tree National Park.
A good portion of the previous permitting dealing with physical and biological aspects of the site could be recycled in a new proposal, according to a solar professional familiar with California’s CSP permitting. He does not anticipate avian mortality giving opponents ammunition.
A full year of Ivanpah tallies would be available to the next round, giving regulators an even better idea of the effectiveness of humane avian deterrents. 133 birds were singed by solar flux near the three towers at the closely monitored Ivanpah power tower CSP project over the first 6 months, and avian deterrent technologies were put in place. As the first US tower CSP, Ivanpah served as the testbed.
The new round of permitting would focus on the changed technical configuration comprising a single, lower tower and storage. Some insiders are suggesting that 150 MW might be the size chosen.