By choosing renewables alone, the state may be closing off
other decarbonization pathways.
Last week, California’s quest for a clean grid
revolution culminated in the introduction of a bill mandating 100 percent renewable energy by 2045.
Senator Kevin de León, a longtime environmental leader in
the state senate, wrote the measure, which comes on the heels of last year’s
major greenhouse gas reduction bill. Massachusetts
legislators introduced the same goal with a deadline of 2035.
Momentum behind such efforts has grown stronger in defiance
of President Donald Trump’s antediluvian approach to climate science. But it's
too early to assess the chances of these passing.
It's easier to prognosticate on the effects of passing such
a goal. And there's a lot of evidence that 100 percent renewable energy is not
the optimal way to decarbonize the grid.
Set in stone
Opponents of renewable energy incentives often use the
argument that government shouldn't pick winners and losers.
There's a big difference between giving fledgling, socially
beneficial technologies a boost so they can compete effectively in a calcified
marketplace, and using the power of government to favor one set of mature
companies over another in providing a similar service.
The legal requirement to source 100 percent renewable energy
looks more like the latter.
But let's say climate change requires massive government
investment in clean technologies. In that case, the question shifts to one of
efficacy: Since climate change justifies extraordinary measures, what is the
most effective extraordinary measure to fight it?
That’s where 100 percent renewables plans fall short, for
both structural and practical reasons.
The stated goal is to decarbonize the electric grid.
Converting all electrical generation to some combination of wind, hydro and
solar is one way to achieve this goal.
The proposals at hand would make that particular method the
endpoint. At best, this is indirect policy: Instead of saying “figure out the
best way to decarbonize the grid,” it says, “figure out how to deploy a
prescribed set of energy resources which should lead to the decarbonization of
the grid.”
At worst, it’s picking one path to the exclusion of other,
potentially better, paths.
Here's how Jesse Jenkins, an energy systems researcher at
MIT, framed this problem: “Why would we want to constrain
ourselves to a narrow set of options to confront climate change and air
pollution and other energy sector challenges when those challenges are already
quite difficult?”
This only makes sense if it's possible to prove that some
combination of wind, hydro and solar is the most practical route to a
zero-carbon grid, accounting for speed, cost and probability of success. Not
only should it beat every option currently available, but any future
possibilities based on technological progress in the next several decades.
Arguably the most prominent planners of the 100 percent
renewable approach are Mark Jacobson of Stanford University and Mark Delucchi
of UC-Berkeley, and they end up arguing that the ramp-up of renewable
production to power the whole country is possible given our nation's previous
success with World War II-era societal mobilization.
That's an inspiring precedent, but not one you'd like to see
guiding a feasibility study.
We don’t know that a 100 percent renewable approach is the
fastest, cheapest or easiest way to decarbonize the grid. We do know that it
will be expensive and hard enough that its own advocates compare it to the most
gargantuan collective effort in the nation’s history.
And now for the practical stuff
Setting aside the case for keeping options open, the
operational realities of a completely renewables-powered grid create challenges
that could be avoided with other zero-carbon configurations.
Solar and wind alone cannot be relied upon for constant
service. This requires some combination of:
1) overbuilding capacity over a
geographically dispersed region;
2) using a whole lot of storage; and
3)
dramatically improving regional import and export of electricity.
If solar and wind form the baseload, you have to prepare for
the scenario when the sun is mostly blocked and wind is weak. One way to do
this is building enough extra capacity that with all the fleet operating at its
trough of productivity, there is still enough to power the system. That
requires building capacity well beyond the reserves required of thermal plants,
which produce a much higher percentage of their potential output.
This multiplies the cost of the build-out, which is
compounded by the diminishing returns of additional renewable capacity. With so
much extra solar on the grid, grid operators have to deal with over-generation
when the weather conditions are optimal. Solar and wind plants may have to
curtail their output under such conditions.
The more solar that goes onto the grid without a productive
use, the more curtailment any additional solar facilities will face.
“Value declines due to curtailment because each unit of
potential PV production no longer displaces one unit of fossil generation,”
states a study from
the National Renewable Energy Laboratory on how to reach 50 percent PV
penetration in California. “As curtailment increases, the benefits of
additional PV may drop to the point where additional installations are not
worth the cost, creating an economic limit to deployment.”
Storage offers a hopeful way out of this conundrum, allowing
renewables to act more like traditional power plants.
California has almost single-handedly jump-started the
advanced storage industry by setting a statewide mandate, but the state is
still in the early stages of this rollout. That means utilities are still
testing how storage works on the grid, and how it performs after several years
of service -- both of which are crucial to planning a grid that is all
renewables.
Residential storage is even more nascent, with companies
scrounging for customers and small-scale pilot programs. Residential storage
could play a role in balancing the grid and shifting loads, but it needs to
reach millions more customers to fulfill that role.
Additionally, expanding California’s grid connections with
its neighbors would smooth the renewable expansion by allowing more imports and
exports at opportune times. This kind of interconnectivity of transmission
lines takes a long time and requires coordination with several states -- and
it's also quite controversial in the region.
Even with optimal grid improvements, California would still
need an estimated 15 gigawatts of additional storage just to reach 50 percent
solar by 2030, according to an NREL study.
That’s more than 11 times the amount of storage mandated currently in
California, and 66 times the total megawatts deployed in the U.S. last year.
This represents a massively expensive undertaking. A different
study from Jenkins and researchers at Argonne National Lab
demonstrates how the need for storage goes down if the grid includes some sort
of flexible baseload power in addition to intermittent renewables. More
flexible nuclear power or natural gas with carbon capture and sequestration
(CCS) could fill this role, in places where substantial hydropower isn’t
available.
Small modular nuclear reactors are still in a very
early stage of regulatory review, and CCS
has not achieved commercial success, so these are not certain options. A
lot can happen in 28 years, though, and a zero-carbon mandate for the
California market would be a powerful driver for development of such
technologies.
Again, that’s if California’s goal is to achieve a
zero-carbon grid -- rather than just solely boost renewables.
In a previous interview, Jenkins described what proposals
like the one in California will accomplish: “It’s not saying this is the
best pathway forward in terms of any metric, particularly in terms of cost.
They say, ‘How much can we push renewables and only renewables? And what will
be necessary to try to decarbonize with that pathway alone?’”
Choosing that pathway alone will mean all kinds of other
decarbonization pathways get shut out.
No comments:
Post a Comment