7/13/2015

Baseload Solar with Natural Gas


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).

http://daysgt.blogspot.mx/2015/05/baseload-solar.html

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.

Feel free to add to the conversation in Twitter. 





* https://en.wikipedia.org/wiki/Life-cycle_greenhouse-gas_emissions_of_energy_sources

** 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%.





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