The Cost of Replacing Diablo Canyon With Solar
Closing down Diablo Canyon Power Plant (DCPP) in 2025, as proposed by PG&E and others, is a fatally flawed plan. Not only will it hurt California taxpayers and ratepayers, it will also set back California’s climate goals for many years to come. Though there are many issues with the shutdown proposal, this article focuses on the exorbitant costs that taxpayers would incur in an attempt to replace DCPP with renewables and energy storage—costs that would ultimately delay California’s climate goals by many years.
To get a sense of how taxpayers and climate goals would be affected by the proposal, several CGNP scientists recently studied the costs and logistics required to replace DCPP’s 18,000 GWh per year of clean and steady electricity generation with solar PV farms. Doing so would require:
- Many new Topaz-class Solar PV farms to deliver a steady flow of 18,000 GWh per year of electricity.
- New pumped hydro-storage facilities to maintain power at night and cloudy days. (There is no battery technology capable of providing this level of storage.)
- Additional transmission lines to deliver electricity to storage facilities and ratepayers.
Replacing DCPP requires an energy source that provides power that grid operators can dispatch 24 hours a day, 7 days a week. But California solar PV farms (such as Topaz) are dispatchable for only about 5 hours per day (with a peak output that is about 6 hours early relative to peak demand), so solar PV farms alone cannot, of course, replace DCPP. To do that, California would also have to build the equivalent of 7 new Helms Pumped Storage Facilities (HPS) to store energy captured by solar PV farms at a projected cost of $35 billion. The stored energy would be used to provide electricity when the farms aren’t generating enough electricity or are are generating no electricity at all.
A further complication is storage losses; HPS facilities are only 75% efficient. For each unit of energy used to pump water to these facilities, only 0.75 units of energy are returned when the water flows back out. Therefore, to emulate DCPP’s dispatchable power, solar PV farms must make up storage losses by generating a total of 24,000 GWh of electricity per year—6000 GWh more than DCPP’s 18,000 GWh per year.
Since Topaz Solar Farm produces around 1,300 GWh of electricity per year, it would take 18 similar solar PV farms to replace DCPP at an estimated cost of $24.2 billion (using average construction costs per MW in 2016, the latest cost estimates provided by the Energy Information Administration). In addition, these 18 solar PV farms alone would require 171 square miles of land; building them at the rate of 2 per year would likely take 9 years or more to complete.
All this new electricity generation would also require building new transmission lines, adding additional costs. These lines would connect the 18 new solar PV farms to both remote HPS facilities (which must be located in the mountains) and electricity customers.
The California Energy Commission (CEC) has completed an assessment of the California’s transmission grid and its ability to bring online large amounts of additional renewable capacity. The CEC estimates that upgrades and additional High Voltage lines would cost about $5.6 billion.
The total cost of replacing DCPP with solar PV farms ($24.2 billion), HPS facilities ($35 billion) and new transmission lines ($5.6 billion) comes to $64.8 billion. Not only would this expensive venture not reduce California’s carbon emissions (since it simply replaces one zero-carbon electricity source with another), a large additional carbon cost would be incurred by building all these solar PV farms, HPS facilities and transmission lines–delaying reductions in carbon emissions even further. Given that PG&E already spent $1 billion to enable DCPP to remain operational until at least 2045, that $64.8 billion would be far better spent on projects that actually reduce California’s carbon emissions.
Since the HPS facilities alone would cost $35 billion, it is extremely unlikely that such facilities would ever be built. Instead, the most likely scenario is that DCPP would be replaced by burning natural gas to generate electricity. After all, this is exactly what has happened in the past every time a nuclear power plant has been shut down in the U.S. with the promise of replacing it with renewables.