Joe Romm, at the influential Climate
Progress blog, has hit on a formula for countering the coal
industry's claims that we need baseload power sources. Since
Concentrating Solar Power (CSP) in conjunction with thermal storage can be used
to generate 24/7 or baseload power Joe has renamed it "Solar
Baseload." This is win-the-battle-lose-the-war thinking.
While it does neatly counter the argument we need coal or nuclear, since there
are renewable power sources which can produce baseload, such as CSP,
Geothermal,
and Biomass.
I fell into this coal-industry trap myself in a 2007
article about Geothermal, as did AltEnergyStocks Editor Charles Morand in an
article
on CSP.
Dispatchable Solar, not Solar Baseload.
Continuous power from solar energy was first demonstrated at the Department
of Energy's (DOE) Solar
Two project in the late 1990s. I recently interviewed Bill Gould, CTO of CSP
company Solar Reserve. Solar
Reserve now working to commercialize the molten
salt thermal storage and solar receiver technology demonstrated at Solar
Two, where Bill Gould served as project manager.
According to Gould, DOE's intent at the Solar Two project was to demonstrate
dispatchable power, not baseload power. Dispatchable power is power
that can be called on when needed, in contrast to baseload power, which is
essentially always on. As a demonstration, Gould's team throttled back the
output from Solar Two to 10% of capacity, and this allowed the plant to produce
power continuously for a couple weeks until it was interrupted by several consecutive
days of cloudiness. But, in essence, it was a stunt: baseload power is far
less valuable than dispatchable power.
The coal
industry says that we need baseload power because our refrigerators still come
on in the middle of the night. This is like saying we should have the
water running constantly in the kitchen sink because we may get thirst at any
time and want a drink. Put in these terms, the assertion that we need
baseload power is clearly nuts: what we need is controllable power that's there
when we need it, but is not wasted when the lights are off and the fridge is not
running.
The Problem With Baseload
Last spring, I discussed one of the problems
with baseload power. The more baseload power you have, the harder it
is to use variable generation such as photovolatic (PV) solar and wind
power. Or, from the baseload generator's perspective, the more variable
generation on the grid, the less baseload power can be added. This fact has not been lost on the UK's nuclear
industry, which is fighting to get wind targets lowered.
To illustrate the incompatibility of baseload and variable energy sources, I
downloaded 4 days of real demand data (January 1-4, 2008) from ERCOT's
website. I then simulated production curves for two variable sources,
one designed to mimic solar PV (only on during the day, with some variability
due to clouds) and a more random type of generation to simulate wind.
I then fixed the amount of baseload power at 25,000 MW (68% of demand) and 5,000
MW (14% of demand) in each of two scenarios, and saw how much wind and PV the
remaining demand could accommodate with the constraint that total generation
could not exceed demand.
As you can see, when I dropped baseload power from 68% to 14% of demand, I
was able to increase the power of variable sources from 10% to 36% of
demand. Almost half of the drop in baseload power was filled by variable
power sources, with the balance requiring an increase in dispatchable
generation. If you'd like to try your own scenarios, you can download my
Excel spreadsheet here.
Better than Baseload
It should be clear that dispatchable generation is truly premium power
source. Dispatchable generation, like energy
storage, long distance transmission, and demand
response, all allow the grid to accommodate more variation in both power
supplies and in demand. In a carbon-constrained world, where we want to
use as much variable generation such as wind and PV as possible, zero carbon,
dispatchable power from CSP can do far more to help us decarbonize the grid than
CSP baseload.
Baseload power is part of the problem; it's not the solution. We should
not denigrate CSP by pretending it is only a substitute for coal or nuclear.
Concentrating Solar Power is much better than baseload.
Tom Konrad, Ph.D.
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