In this Feb. 25, 2015 photo, a gas flare is seen at a natural gas processing facility near Williston, N.D. (AP Photo/Matthew Brown)
We’re at a time of deeply ambitious plans for clean energy growth. Two of the U.S.’s largest states by population, California and New York, have both mandated that power companies get fully 50 percent of their electricity from renewable sources by the year 2030.
Only,
there’s a problem: Because of the particular nature of clean energy
sources like solar and wind, you can’t simply add them to the grid in
large volumes and think that’s the end of the story. Rather, because
these sources of electricity generation are “intermittent” — solar
fluctuates with weather and the daily cycle, wind fluctuates with the
wind — there has to be some means of continuing to provide electricity
even when they go dark. And the more renewables you have, the bigger
this problem can be.
Now, a new study suggests
that at least so far, solving that problem has ironically involved more
fossil fuels — and more particularly, installing a large number of
fast-ramping natural gas plants, which can fill in quickly whenever
renewable generation slips.
The new research, published recently
as a working paper by the National Bureau of Economic Research, was
conducted by Elena Verdolini of the Euro-Mediterranean Center on Climate
Change and the Fondazione Eni Enrico Mattei in Milan, Italy, along with
colleagues from Syracuse University and the French Economic
Observatory.
In the study, the researchers took a broad look at
the erection of wind, solar, and other renewable energy plants (not
including large hydropower or biomass projects) across 26 countries that
are members of an international council known as the Organisation for
Economic Co-operation and Development over the period between the year
1990 and 2013. And they found a surprisingly tight relationship between
renewables on the one hand, and gas on the other.
“All other
things equal, a 1% percent increase in the share of fast reacting fossil
technologies is associated with a 0.88% percent increase in renewable
generation capacity in the long term,” the study reports. Again, this is
over 26 separate countries, and more than two decades.
“Our
paper calls attention to the fact that renewables and fast-reacting
fossil technologies appear as highly complementary and that they should
be jointly installed to meet the goals of cutting emissions and ensuring
a stable supply,” the paper adds.
The type of “fast-reacting
fossil technologies” being referred to here is natural gas plants that
fire up quickly. For example, General Electric and EDF Energy currently feature
a natural gas plant in France that “is capable of reaching full power
in less than 30 minutes.” Full power, in this case, means rapidly adding
over 600 megawatts, or million watts, of electricity to the grid.
“This allows partners to respond quickly to grid demand fluctuations, integrating renewables as necessary,” note the companies.
“When
people assume that we can switch from fossil fuels to renewables they
assume we can completely switch out of one path, to another path,” says
Verdolini. But, she adds, the study suggests otherwise.
Verdolini
emphasized this merely describes the past — not necessarily the future.
That’s a critical distinction, because the study also notes that if we
reach a time when fast-responding energy storage is prevalent — when,
say, large-scale grid batteries store solar or wind-generated energy and
can discharge it instantaneously when there’s a need — then the
reliance on gas may no longer be so prevalent.
Other recent
research has suggested that precisely because of this overlap between
fast-firing natural gas plants and grid scale batteries — because they
can play many of the same roles — extremely cheap natural gas prices
have helped the industry out-compete the storage sector and slowed its growth.
Two other researchers contacted for reactions to Verdolini’s study largely agreed with its findings.
“I
think policymakers haven’t really grasped what 50 percent renewables
really means in a system, without at least cheap batteries available,”
says Christopher Knittel, who directs the Center for Energy and
Environmental Policy Research at MIT, and who said he found the study’s
results quite plausible.
“It’s certainly true that as one adds
more renewables, the value of flexible generation increases, and so I
would expect to see some correlation as they found,” added Eric
Hittinger, an energy system researcher at the Rochester Institute of
Technology who like Knittel was not involved in the study.
Hittinger
and Knittel agreed that adding flexible natural gas alongside renewable
projects is not a major climate change concern because the gas plants
wouldn’t be running all the time — so it’s not like adding coal plants.
The emissions would be real, but considerably more limited. However,
they said, the principal issue is that the research suggests renewable
plants are more costly to build, because of the added backup
requirement.
“It’s a reality check now,” said Knittel of the
study. “I think it’s potentially bad news as we start to get higher and
higher penetration levels of renewables.”
The study also lends
some credence to the widespread description of natural gas as a
so-called “bridge fuel” that allows for a transition into a world of
more renewables, as it is both flexible and also contributes less carbon
dioxide emissions than does coal, per unit of energy generated by
burning the fuel. (Environmentalists like to point out that if there are
enough methane leaks from the process of drilling for and transporting
natural gas, this edge could be canceled out.)
Hittinger also questioned what the correlation found in the study actually means — does it mean that natural gas spurs on the development of more solar and wind, or vice versa?
Verdolini
said the study implies that the causation occurs with gas plants being
added first, which then makes renewable projects more easy to integrate.
“It’s an enabling factor,” she said, although she cautioned that the
study cannot fully demonstrate causation.
Verdolini agreed that
the findings are something that decision-makers hoping to add more clean
energy to the grid will have to take into account.
“If you have
an electric car, you don’t need a diesel car in your garage sitting
there,” said Verdolini. “But in the case of renewables, it’s different,
because if you have renewable electricity and that fails, then you need
the fast acting gas sitting in your garage, so to speak.”
