Several weeks ago we wrote an article underlining what would be required to install a one GWe solar baseload power plant using storage batteries to achieve a reliable output (from an unreliable solar input).
The conclusion was that the approach was too expensive and not environmentally friendly.
Today, we'll analyze another option: make solar PV output reliable by pairing it with a natural gas power plant.
Again, there will be some simplifications here, but bear with us.
The objective is to deliver 1 GWe of reliable electricity, thus we'll install a 1 GWe natural gas power plant plus 1 GWe of solar PV.
Let's consider the annual solar capacity factor at the selected location is 20%.
The natural gas plant will be dispatchable to be able to produce 100% of the required power at any particular moment, zero when solar PV is at peak production and all the intermediate values throughout other particular moments during the year.***
The combined solar / natural gas power plant will produce this amount of energy annually:
1 GWe x 24 hrs. x 365 days = 8,760 GWh.
Of the above, solar PV (at 20% annual capacity factor) will produce: 8,760 x 0.20 = 1,752 GWh.
And the nat gas plant will then produce the rest: 8,760 - 1752 = 7,008 GWh.
Thus, the theoretical emissions of the system per kWh would be:*
0.20 x 48 grams/kWh + 0.80 x 490 grams/kWh = 402 grams/kWh.**
Yes, 402 grams are lower (vs. an unpaired nat gas plant) but not low.
If we consider the installed cost of solar PV at $2 USD per peak watt, the 1GWe installation above would cost 2 billion dollars. Would this money be well spent to achieve a reduction of 88 grams per kWh?
As a reference, just consider that nuclear, without any pairing with solar PV, produces electricity at a carbon intensity of only 12 grams per kWh.
If nuclear replaces coal, for instance, the CO2 emission reductions per kWh should be around 808 grams.
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** However, in real life the natural gas plant will have to be idled, stopped, restarted, etc., so the combined emissions of the system will be above 402 grams per kWh.
*** To simplify, we are considering the availability of the natural gas power plant to be 100%.