Arizona is hot for the sun – this is without any doubts. They’ve built beauty in the desert, residential customers are powering up, the solar advocates are taking the seats of power, regulators are fighting back and the grid is evolving – even while the governor fights the inevitable, utilities settle Supreme Court bound lawsuits, the politicians quibble and the FBI watches.
The latest hot trend? Replacing coal plants with solar.
On June 7th, another step was taken as the governing body for the Central Arizona Project, a massive water diversion project that is the largest electricity user in the state, approved a 20-year power purchase agreement with the 30 MW AZ Solar 1 project at 2.49¢/kWh (PDF). The agreement was noted by Arizona regulators as being part of the expected shutdown of the Navajo Generating Station, one of the nation’s largest running coal power plants. The contract starts on December 31, 2020.
Significant contention surrounds shutting down the plant as the Navajo tribe gains significant financial gain from hosting the plant, and the jobs that come from running the site.
Emma Foehringer Merchant, writing for Greentech Media, reported that the solar plant plus other 5-year energy contracts will offset only 14% of the coal facility’s production capability. However, the coal plant is delivering said power at 5¢/kWh, twice the per-unit cost of the new solar project.
GTM also notes that an Austin deal might have a price as low as 2.1¢/kWh, but those numbers aren’t official as contract isn’t publicly disclosed.
The 30 MW plant is under development by Origis Energy USA, which will also own the plant. AZ Solar 1 is contracted to deliver an estimated 85,300 MWh. This would denote an AC capacity factor of 32%, and a DC capacity factor ranging of anywhere from 19-27% with DC:AC ratios of 1.7 and 1.2, respectively.
While the module vendor for this plant is unclear, Origis has built plants in the past using both First Solar and standard 72-cell crystalline silicon modules, along with both fixed-mount and single axis tracker configurations.
Xcel Energy of Colorado recently proposed a of a bit of coal in Pueblo for some serious solar+storage volume at amazing prices as well. The solar power bids ranged from 2.3-2.7¢/kWh, while solar plus storage ranged from 3.0-3.2¢/kWh. While it makes for an imperfect comparison as solar project costs vary, the solar vs solar+storage delta is 0.5-0.8¢/kWh.
Hot trend of the season, indeed.
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The S+S bids at 3c/kWh is a big big drop in a very short time.
The one issue that always concerns me is that there is no standard for judging anything + storage.
It would be useful if some kind of standard was created so that projects could be compared on an apples to apples basis.
The quoting of solar plus storage as xx cents per kw is meaningless for storage as it is the number of hours of storage that is important.
One project that offers .1 hours of storage per kW is very different to one that provides .3 or 1.
So, in reality, quoting one project at xx cents/kW and another at yy cents is only good at filling space as it provides zero meaningful information.
..and provides those who oppose the growth of renewables power generation ammunition to use against it.
Maybe you don’t understand what kwh means. It is 1000 watts for 1 hour. So if you want 10 hours of storage and load is only 100 watts you only need 1kwh of storage. If you have 1Mw load and need 24hours of storage then you need 24,000kwh storage. $ Per kwh is the proper metric to use.
They use $/Kwh because that is how retail ratepayers see their energy bills and it is an easy comparison. The wholesale market trade in $/MWh, so the contract is ~$25/MWh flat for 20 years. Storage is typically only good for about 2 hours and the norm is to design a system with ~10% of the total capacity covered by storage or in this case 3-5 MW, more than likely shifting energy from HE 13-14 to HE 18-19. Storage is ~$1,000 kw (not kwh) and when 10% of the total is covered by storage, it only raises the price incrementally, instead of a several X multiple. The baby math is essentially $1,000/kw of 3 MW of battery/30 MW of solar capacity. Batteries are still very expensive. Adding them into a system in small doses means spreading relatively large dollars per output over a much larger load, resulting in a small overall increase to the PPA holder or ratepayer.