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PROFESSOR: So today we're going to look
at the situation with renewables.
And I said that, in the '90s and the early 2000s,
the nuclear was the obvious path.
And then renewables just showed up and ate our lunch.
But there are a lot of people who are still
kind of skeptical about what renewables can do
for a lot of different reasons.
And we ought to have a deeper look
to try to understand some of these arguments.
So we're going to do that today.
I guess I'll just give you a heads up.
The final answer is people aren't stupid.
They're proceeding with renewables for good reasons.
So we should expect something like that.
Before I get there, I just wanted
to give an opportunity to speak, if there's
any kind of clarifying questions on previous stuff.
There are some things I've added to this lecture
that people have brought up, but I'll just--
there's no other questions before I go?
OK.
I keep reading the reading responses
and I see some ideas that have been missed.
So as they come up, I'll try to add them into the lecture.
All right.
So let's talk about this topic.
There are a number of ways of decarbonizing.
Nuclear is one.
Renewables was one.
Carbon capture and storage, which we aren't really
going to talk about, is one.
Geothermal, which you can clump into renewables, is one.
Of all of these, renewables is the cheapest.
And we saw this result from Jacopo Bongiorno's model.
This is for the Southern United States that
has good renewable capacity.
And you see that they allow carbon capture and storage
to be part of the model.
And we had a big chunk of energy coming from renewables
in this modeling simulation.
I think this is something that got missed based on,
like I said, reading people's responses.
This is a cost-optimized system.
So for any level of decarbonization,
it's telling you the optimal mix that gets you that generation
without spending too much money.
I mean, we could build a bunch of little wheels
with hamsters in them and they would
produce carbon-free energy.
It would just be very expensive.
There's all kinds of solutions, but these
are the cost-optimal ones.
But something seems to have not dropped.
Is that these are also dispatch optimized mixes.
Maybe dispatch viable mixes, like the wind and solar capacity
that makes up this chunk is not, let's say, nameplate capacity.
This is like, I don't know what, 60% of generation.
It doesn't mean that the nameplate
capacity of wind and solar is 60%
of the total electrical demand.
The capacity may actually be much, much in excess
of that in order for it to reliably produce
60% of demand on average.
So these models, despite the of non-dispatchability
of wind and solar, these are models
which keep the grid running.
These are not solutions which are not viable.
And this is an important point.
I also realized I never really talked about what
dispatchability means.
It's a nuanced thing.
So often when we say dispatchability,
we say something like, I went to your nuclear operators and said,
I want you to give me a gigawatt of electricity next week.
And you say, sure, I can do that.
And that's dispatchability.
And if I go to the solar people and I
say, I want you to give me a gigawatt of electricity,
they may say, well, we can't promise you a gigawatt.
Or if they have a lot of excess build, they'll say,
well, we have a 99% chance we can promise you a gigawatt.
And at the end of the day, the nuclear plant
also has some chance of not being able to provide it.
So you can get there.
You get towards dispatchability with excess generation.
But there's a second aspect of dispatchability
that we haven't really talked about,
and that's really maybe it's better termed as flexibility.
If I say to you, oh my gosh, it turns out,
everyone is plugged in their cars for some reason.
And I need more power now.
I need it on the grid in 10 minutes to keep the grid up.
Nuclear I can't help you.
It takes me a day to boot the plant.
And then the solar people goes oh, no problem.
And they can just turn on the power.
So that is a really important element,
same with taking power off.
You can curtail wind and solar instantaneously.
You can't generally curtail nuclear instantaneously.
This thing has got to dump the heat somewhere.
So variability is really important and arguably more
important.
It's hard to rank these things, but it's
really important to keeping the grid operating, which
is it's a just-in-time system where we're constantly trying
to balance supply and demand, and you only
have a tiny margin within which you can work.
But it's also why you don't ever see wind and solar becoming
100%, because despite the fact that it
is very flexible, in order to achieve
both flexibility and guaranteed dispatchability,
you would need so much overbuild that it just doesn't
become economically sensible.
So you always see it blended in with some storage
to deal with those times where you can't dispatch it,
and some kind of firm resource, which in this model is nuclear.
But in other models, likely that would be taken up by geothermal,
if you had it, because geothermal
is a dispatchable, low-carbon energy source,
just like nuclear.
So those were for the areas where renewables were poor.
Here in areas where renewables are not so great,
you see the total renewable capacity is closer to 20%
or total generation is closer to only 20%.
And that's kind of interesting.
That's actually just about where nuclear is today in the US grid.
So the rest has to come from something else.
And in this model, it's a lot of storage,
and some carbon capture and storage,
a lot of battery storage which I think in this model
is lithium ion, and then some carbon capture and storage
on natural gas.
This technology I don't really track it too closely,
but you could imagine there would be reasons
why this technology doesn't really reach full scale usage
is, for example, I'm not certain how
reliable the CO2 can actually be stored on long timescales.
Does it leak out, and so on?
And I'm not sure that we really have good answers to this yet,
but it would be a good paper topic for people who
really want to dig into that.
If this goes away, what happens is you see
these other things expanding.
We see more storage, more wind and solar, maybe
more nuclear, or more geothermal, depending.
So anyway, I just wanted to remind you
that these are models that keep the grid up.
They take into account the variability
of the generation source.
All right.
So let's talk about what's going on in the world with renewables.
I said they're kind of eating our lunch.
And here is an example.
This is global changes to the worldwide, not just
US, in electricity generation by source.
Every year, we see, so brown means is coal.
We see some coal coming upline, coal coming upline,
coal was built, coal was built, coal
was built, coal coming offline, coal coming offline.
Actually, I shouldn't say offline.
This is generation.
So I just say used or not used, compared to previous years.
But what you see is that basically renewables
are producing more and more and more electricity every year
globally.
And the result is that it's rapidly decarbonizing the grid.
And at least in OECD countries, developed Western world,
renewables now generates not capacity,
but actually produces watts on the grid
more so than any other source of electricity
other than natural gas.
So it's not something that's coming.
It's very much here in large amounts,
and it is growing very rapidly.
So, I don't have data.
Unfortunately, the people who published this chart
rearranged their data.
So they now clump coal and gas and they call it fossil fuels.
And so you can't really tell where
renewables are relative to these other sources.
So that's just my data only goes to 2020.
And I really don't know if renewables has now crossed gas
or not, but it may well have.
So the result of all of this generation being built
is big changes in the structure of the grid.
This is just the United States.
And this is for this year.
This gets published at the end of the previous year,
and this is what's in the queue.
And these things are typically in the queue
for about five years before they get on the grid.
So we have a pretty good idea of what's coming online.
And so it says between wind, solar, and battery storage,
the United States is scheduled to add 63 watts of capacity.
To add that much nuclear at the current
build rate in the United States would take us 315 years.
So this is happening in one year.
It's happening this year.
And we're halfway done with it.
That gives you a sense of how big you'd
have to ramp the nuclear industry to start competing
with this industry, right.
A 31,000% increase in the size of the nuclear industry,
just to break even with wind and solar.
I can't really underscore this enough.
This is not something coming.
This is already here.
So our question is like, will it keep going?
Is there something that will in the end suddenly stop this.
And there are two basic things that might do that.
One is resource constraints.
OK, it's nice, but land is going to become
an issue, something like that.
And the other two is when you put
more and more variable generation on the grid,
you have more volatility in the supply of electricity.
And the question is, will we require so much overbuild
in order to dispatch that generation that it
becomes uneconomic?
It's fine if solar that only turns on
in the middle of the day, and you only
have a little bit of solar, because in the middle
of the day, you have a little bit of extra demand.
And so it's nicely balanced.
But in the future, if you have a grid built on solar
and then you need to turn on power
in the middle of the night, maybe it doesn't work, right?
So how much overbuild do you need
to keep the grid running, and that
makes the economics less and less favorable
as you get more and more renewables.
So we'll look at both of these questions today.
So just in the basic most basic level
at the physics kind of approach, yes, there's
a lot of sun on the surface of the United States.
3,500 times annual consumption, if you put solar panels over
the entire United States, obviously that's not possible.
How much land would you have to cover with solar panels to power
the entire US electrical grid strictly from solar,
which you would never do?
But if you wanted to do that, how much land would you need?
Assuming 20% panel efficiency would
need 0.04% of land, which is a square about 60 miles per side.
And so is that a lot of land or not a lot of land?
And I think we need some context to understand that.
So if I put it all in one spot here, here it is.
It looks enormous.
It looks like it's taking up a chunk of Nevada.
This, Incidentally, is almost exactly
the same size as the Nevada test site,
where we test our nuclear weapons,
so we've devoted exactly the same amount of land
to testing bombs.
I guess we could probably devote the same amount of land
to building solar farms.
It's also important to remember that we do already devote land
to making energy.
I mean, a lot of land to making energy.
Obviously, every energy production takes some amount.
But does anyone have in mind, like the most land
intensive form of energy generation?
AUDIENCE: I'd say maybe hydro, with like the lakes.
PROFESSOR: No.
AUDIENCE: Is it solar?
PROFESSOR: Corn ethanol.
We grow corn in America strictly to turn it into ethanol,
to make gasoline, well, to dilute gasoline with ethanol.
And this is one fifth of the amount of land
that we already use to grow corn ethanol.
And on top of it, the life cycle emissions of corn ethanol
is about half that of gasoline.
So it's not a low-carbon energy source.
This is a low carbon energy source.
Right?
So we could easily cut down one fifth of corn crops,
replace them with solar panels, and significantly further
decarbonize the system by getting rid of medium polluting
ethanol and replacing it with net zero basically for CO2.
It's also about one eighth of the amount of area
that we currently devote to the emergency planning zones
for the 98 nuclear reactors in the United States.
Now, people live in emergency planning zones,
so you can do other things with that land.
But in terms of just realizing that there are constraints being
put on the large amounts of land for energy generation,
this is something we do all the time.
It looks a lot different if I spread it out.
That's the same amount of land spread out in tiny little dots.
And suddenly like oh, well, that looks fine.
So is there that much land available?
So here's a plot that shows the amount of land that belongs just
to the federal government.
No one owns.
It belongs to the government.
It's about 28% of the United States.
An enormous amount of that land is
in solar-friendly friendly regions.
And so we use this land for things like military bases,
and like I said, the Nevada test site where
we test nuclear weapons, not in principle
any reason why we couldn't also-- we
granted land, federal land, to NuScale
to build their nuclear reactor.
We could theoretically do the same for solar.
Yes question or no?
OK.
OK, so what about non-US?
I mean, the US is a big space.
What about countries like Japan?
That might be more interesting.
So here's a nice way to do the comparison.
Here are the land use in the United States.
And you see 29% of land is pasture land, and grass,
and ranges with basically nothing on it.
We have some forest.
But forest are not a great place for solar panels
because trees tend to grow there.
We don't necessarily want to displace cropland,
but we could because a lot of that
is being used for corn ethanol.
But we have a lot of what you would call
empty land that we could use.
So another potential issue with solar
might be can you build all these solar panels?
So if you look at the minerals required to make solar panels,
there doesn't appear to be a fundamental supply-chain
problem.
The biggest near-term risk is over,
which is used in these-- you see these traces on the front
of these silicon solar panels.
It's actually so the enormous growth of solar
is responsible for the current shortage in the silver market.
But there are all kinds of things
that manufacturers are doing because
of the economic pressure, the rising cost of silver.
To deal with this, they are making the traces thinner.
They are making copper traces that are just silver plated.
And the studies basically suggest
that between this thrift and substitution
for silicon-type solar panels, silver
will not be a limitation in the long run.
Everything else in a traditional silicon cell, the polysilicon,
the glass, aluminum, encapsulants,
even the copper for the wiring are
things that will require a diversified supply
and expansion of supply.
But there's not a critical mineral resource limitation.
When it comes to recycling solar panels, dealing with the waste
problem, there isn't a toxicity issue or a technology issue
with doing recycling.
The problem is really just like the sheer scale of it
and making it economic to do so.
So by 2050, we're expecting something
like 60 to 80 million tons of waste solar panels worldwide.
Most of that mass is glass and aluminum.
Both of those things are very recyclable.
The problem is that the silicon panel itself is very thin
and has virtually no intrinsic value.
Once it's used up, it's not really worth recycling.
The silver content was, but as the over content shrinks,
that becomes less interesting to recycle.
And so for now, in most markets, it's
much more economic to just trash these panels after you rip off
the aluminum in the glass.
There are programs out there to deal with this.
And Europe has a collection and recycling
program for solar panels.
A company called First Solar here
in the US, which doesn't use silicon,
they use cadmium telluride panels,
they have a closed-loop recycling plant.
There are new recycling plants in France
as well to do the silicon recovery at scale.
What's missing is really policy that
will make this economic to do.
And we have a similar problem with dealing
with the waste from nuclear.
It's there and it can sit in canisters
and it's not economically favorable to do anything
with that waste.
So in the US, what we did is we taxed
nuclear power 0.1 cents per kilowatt hour
is a tax for dealing with waste.
And we could, in principle do the same for solar.
And that would solve this waste panel problem.
For solar, resources or waste do not
appear to be a serious bottleneck.
All right.
Let's talk about wind.
So wind is more tricky because there are density limitations.
You can at most fill about 1% of your area with wind turbines
before you drag out too much energy from the air currents.
Still, even with that constraint, the United States,
cover the whole United States with wind
farms would support 17 times total electricity consumption.
All right.
And turbines are getting bigger and much more efficient.
OK, fine.
It's interesting to ask, what would wind do to--
OK, it's one thing to talk about, OK, you're
slowing down the wind and the zone
has only so much extractable energy.
That's talking about.
But what is wind doing to our climate?
Like if we do extract energy from the air movements,
does that affect climate?
So there have been a number of studies
that have looked at this.
There are studies that they start out
with just a gigantic idealized arrays,
and what they see is a temperature
effect on the order of 1%.
And what do I mean by a temperature effect?
Essentially, what happens is that there's
mixing between the cold upper troposphere and the warmer,
lower troposphere.
And the result is that the nighttime-daytime temperatures
get closer together.
That, on average, the air is more uniform in temperature.
It also pushes around the precipitation a little bit.
So there are some places that get a little bit
more precipitation, some places that get a little bit
less precipitation.
And those changes tend to be on the order of 10%.
So let's just look at some studies in high resolution.
This is a regional climate model that is probably
the best one I've seen.
These dots indicate the locations of wind farms.
And so instead of just having wind across the whole US
uniformly, they're trying to say, where would you actually
build these wind farms?
How big would they be realistically?
And this is the result of that model.
And in this model, the wind farm,
the cumulative size of the wind farms
is enough to provide 100% of the electricity to the United States
in terms of total production and total consumption.
So it's not balanced, so that you would need
a lot of batteries to do this.
But that's just to give you a sense of scale.
It's just a scale.
And so you can see that they see temperature perturbations
of up to 1 degree, which is consistent
with the large primitive studies, right in the middle.
But most of the regions have perturbations
on order of about 0.3 degrees.
I think the technical average across the United States
is 0.2, plus or minus 0.2 fluctuation.
In all the studies that have looked at this,
the authors always note a couple of things.
They say that the changes are well
below the average or interannual variability.
So one year, you're going to be a little warmer.
One year, it's going to be a little cooler.
These changes are smaller than that.
And the other thing they point out
is that these changes are way smaller than not doing anything
from greenhouse gases.
So their view is, yeah, there are some changes.
They are detectable but not disruptive.
And indeed, the largest changes tend
to be immediately in the vicinity
and downwind of the wind farms, as you can see here.
And if you put these wind farms like in croplands,
these changes regionally are actually
favorable because it prevents your crops from freezing
overnight.
So people will continue to look at this as wind farms get built.
People will be doing studies to make sure
that these predictions are correct because I
they're just predictions, we really don't know.
And it's important to keep tracking this.
So there is a non-zero but probably negligible,
I guess, is the conclusion effect on the climate.
What about these mineral constraints?
So yeah, there are some concerns about mineral constraints
for making the magnets.
These magnets use rare earths.
Particularly neodymium and praseodymium
are the two big bottlenecks.
There's also some ytterbium.
And I forget, what is it, Dy, does anyone remember?
I think it's like [INAUDIBLE] or something.
Anyway, I don't remember.
So for one, terawatts of installed capacity,
which is approximately the total which is what was actually
shown on the previous plot.
Total US consumption is about half a terawatt year, per year.
And given the capacity factor for wind,
you would need to build about 1 terawatt of wind
to get there roughly.
This is the amount of minerals that you would need.
If you want the global number, you
should multiply this by a factor of 6,
because the United States consumes about one sixth
of the global electricity.
So according to the US Geological Survey,
this is about 0.7% of known global reserves.
Known reserves used to be underlying,
because there's always more than we don't know about.
So it's not a huge amount.
If you did wind for the whole world,
that would be 4% of known global reserves.
So it will make a dent, but whether it's
in terms of being like an actual bottleneck, I don't see it yet.
Some more issues with blade waste,
it was mentioned earlier by someone a couple of weeks ago
in this class.
A lot of the existing blades are glass fiber
set in thermo, in epoxy, fiberglass, fiber-reinforced
epoxy.
The glass is in principle recyclable,
but the problem is that the entropy of the mix is obnoxious.
You can't get the glass fibers out.
And these epoxies are not re-meltable.
So for existing blades, mostly what they do
is they just grind them up and put them into asphalt
or concrete as filler.
But there are a bunch of proposals
for making recyclable blades.
So where are they?
Yeah, they have either moved to do
some research in fundamental chemistry
to find solvents that can depolymerize these epoxies
or just use different materials.
And so there are things like that
have been called recyclomine and others
that have been developed specifically
to make wind turbine blades.
I don't know how good they are.
They have been used in turbines now since 2021,
and whether they have the same lifetime or the same economics,
I actually couldn't really tell you.
But it is an issue.
People are working on it.
It would be bad if wind turbines was a major source
of microplastics.
Right?
So engineering is being done and there does
appear to be some path forward.
But I think, again, something else
that ought to be understood.
There are a bunch of other aspects about wind and solar
in terms of externalities, like impact on how useful land is,
or whether it's killing birds, or whether it's making noise.
And we will look at those, not today,
but when we do the externalities lecture,
we're going to add those all up and see how
that affects wind and solar.
So for both wind and solar, there are no showstoppers yet.
Let's talk a little bit about geothermal.
I call it a semi-renewable resource
because you're digging a hole into the ground.
You're sucking heat out of it and it cools off.
And the way it warms up again is you
have to have, essentially churn from the magma in the Earth,
and that takes time.
So they tend to recharge themselves on 100-year
timescales.
But we have something like an estimated 1,000 times US
consumption in extractable renewable heat.
So as long as this number divided by 100
is greater than 1, we can probably
call it a renewable resource, something like that.
All right.
So then the obvious question is, if this is so great
and it's dispatchable and there's plenty of it,
where is it?
So it turns out issues faced by geothermal
are not actually that different from the issues faced
by the nuclear community.
It's one of finance.
So here's how geothermal works.
You go somewhere where you think there's a good place
to drill a well, but the well that you have to drill
is about 2 to 3 kilometers underground,
and you're not really sure what is beneath you
3 kilometers underground.
So you spend a lot of money, essentially all the upfront
costs, just like building nuclear, all the upfront costs,
drilling a hole in the ground.
And you might find that the well is good,
or you might find that the well is not good.
And it's expensive to drill hot, hard rock very deep.
So investors who are looking at projects, they're saying,
we want to invest in energy for private capital,
for someone's retirement fund.
We're going to invest in some energy projects.
Would you invest in wind, or would you invest in geothermal?
They invest in wind because they know it can be built
and there's a lower risk of the individual investors losing
their money on a project.
And so this has basically slowed interest in geothermal.
It's also what slows interest in nuclear.
Because if you think back to 2005,
29 nuclear plants were going to be built in the United States.
License applications were filed.
And of those, two got built, right?
So imagine you were an investor trying to invest in nuclear,
and on average, you have a one-in-15 chance of actually
making money, and a 14 out of 15 chance of losing your money.
You probably wouldn't invest in nuclear.
And the way we've solved that in nuclear
is to have federal loan guarantees.
And if we had a similar basically saying,
we guarantee that you'll be able to pay your investors back,
and if they did something similar with geothermal,
I think we would see a lot more geothermal.
There's some other stuff related to permitting.
It slows it down and makes these projects take a long time
because you have to deal with a lot of groundwater issues
and so on.
But those are delay factors more than anything.
I had one more point I wanted to make here,
and it just slipped my mind.
All right.
Oh, the point was that investors' decision
to invest in wind and solar, which is obvious given like I
showed you these charts of how much is actually being built,
that's all being paid for by private capital or mostly
private capital.
There will come a point where the value
of building the next wind or solar farm
decreases because of so much capacity already on the grid,
that these projects, these geothermal projects,
will start to look more attractive.
So it's exactly what the economics predicts.
You're going to see basically natural gas and wind and solar.
And that's what you're going to see.
And then at some point, you're going
to see these dispatchable technologies show up
because the economics force the situation to go there.
So that's when we're going to see the geothermal.
All right.
So how much can we do or how much will be done on the grid?
I guess the answer is it appears from what I just showed you,
that wind and solar can heavily decarbonize the grid.
It's cheap.
Why aren't we decarbonized already?
It's cheaper than natural gas.
Why hasn't it displaced natural gas?
The answer is it's doing so, but it's
rate limited by something exogenous.
And what's rate limiting the deployment of wind and solar
in the United States, is not economics.
It's actually connecting to the grid.
So this is a plot which I've extended for two more years,
showing you the total amount of generation capacity from wind
and solar waiting to be connected
to the grid every year.
And you can see that by 2023, the amount waiting
to be connected to the grid is twice the amount of electricity
that we actually use.
That's the black line.
That's the existing generating capacity.
Now remember, this stuff has 30% to 40% availability capacity
factor.
And this stuff has closer to 100% capacity factor.
So this amount of capacity waiting to connect still it's
not going to provide all the electricity,
but it's getting close to providing all the electricity.
It's a really staggering amount, 2.7 terawatts
of capacity in 2023.
It's down a little bit since then.
So the bottleneck is basically getting access
to the grid and the average time that you
are stuck in this queue is about five years right now.
And there's an order from the Federal Energy Regulatory
Commission, I guess, that says that it's
a first-in, first-out queue.
So the people who signed up first
will come out first and so on.
So why are these things taking so long to connect?
Well, if you just dump all this generation on the grid,
that is variable, the people who run
the grid won't be able to keep running the grid,
because the grid is not designed to handle
all of this variability.
And there's a couple of different problems with it.
So one is related to predictability
and controllability.
Yeah?
AUDIENCE: I have a question.
So about what you mentioned that the queue is first-in,
first-out, I heard this a few times,
but I haven't looked into it a lot
myself, is that developers will put projects in,
even though they're not really sure if they're actually going
to follow through because of the queue, so they might as well put
it in and that the actual percentage, so let's say
commitment on what's in the queue, is relatively low.
If you have an idea of how low that is--
PROFESSOR: That's a very interesting point.
I don't.
That would be a really good thing to look into.
I am aware of the alternative situation where essentially
people have made real investments in projects,
and the grid operator has basically denied them access,
and they start suing for access and so on.
I really don't know.
Yeah, that's probably a hard number to come across,
but something worth looking into for sure.
Yeah.
Yeah, I guess we can't really tell anything from this data.
Yeah, I will look into that.
That's a very good point.
Let me just make a note here.
We might not really be able to tell.
I mean, I guess if people put in connection orders,
they're not going to say publicly,
we don't really have the money to do this,
but we're just putting in a connection order just in case.
AUDIENCE: Yeah, I mean, it sounds
from when I was talking to people from the MIT Energy
Initiative, et cetera, that in more of the,
let's say grid modeling community,
this is somewhat of a known thing.
But I never heard them mention any numbers
about oh, we think half of them are fake,
but it seems to be a somewhat known thing.
PROFESSOR: Interesting.
I had never heard of this, but I will look.
It makes sense that this would be done.
So OK, even if we say half of them are fake,
that's still a lot.
All right.
So, let's just talk about the problems, why these things can't
be connected right away, which, despite whether they're
real or fake, I think are our real problems.
So one is this forecasting what is
going to be actually available, how much wind
you're going to have, how much sun, you're going to have.
And the weather models and ability
to do that forecasting has gotten a lot better,
but the integration of that information
into the running of the grid has not yet happened.
Traditionally, the grid was designed to basically dispatch
most of your generation, and then you
would have these small, tiny, near-term capacity markets
to do the little adjustments.
And now we would need to redesign how that happens,
so that the dispatch is more just in time
to deal with the large amount of wind and solar.
So basically it's a control theory and software problem.
And there are people working on this.
But it is a major limitation.
The other thing that has been raised is ancillary services.
So traditionally you have one thing
is just putting watts on the grid.
But the other thing is that you need to do voltage control.
You need to have regular up and down regulation, frequency
stability.
These things come generally from synchronous spinning generators,
which are basically large moving masses that are synchronously
linked to the grid.
And they provide an inertia against unwanted change
and they stabilize the frequency, and so on.
Traditionally, the inverters used for wind and solar
or particularly for solar, don't do that.
However, there are now fancier inverters
called smart inverters, that have
software to simulate the effects of being a rotating machine.
And I think it was this last year, CAISO,
the California grid operator, gave a large-scale test of these
smart inverters, a 300-megawatt megawatt electric solar farm,
using them and to see what they could actually do on a real grid
in terms of providing these ancillary services.
And according to their report, they
performed comparable to or better than conventional units.
So it looks like the smart inverter technology will solve
the ancillary services problem.
So in short, it's basically software electrical engineering,
grid permitting, and software and software and software
that basically has to be worked out
to get large amounts of solar.
And it's coming.
A of people are working on these problems.
All right.
So I just thought to go back to our first slide or early slide,
there doesn't appear to be issues in category 1.
So let's just look a little bit at category 2.
Now, we saw something that looks like a category 2
result with this, which just says for localized grids,
this is the answer.
But what is the situation, if we really said,
let's look at across the whole United States?
We might also be interested in let's look at all across Europe.
So I wrote a paper on across Europe.
It's in the readings.
There's another group, Shaner, who's the author of the paper.
They wrote one on across the United States.
Theirs is a little bit different than mine
in that they don't have particular technologies
substituting.
But I thought, who read Shaner's paper?
Not many people actually read it yet.
A lot of people in nuclear love it because if you read it,
it sounds like wind and solar are really going to fail.
But I think it's just worth like looking at it carefully.
So let me just walk you through.
These are the solution sets from their model.
So what this plots is on the left axis,
the mean solar and wind generation
normalized by the electricity demand.
And so one indicates that the wind and solar
is providing exactly the same amount of electricity
as demanded.
But, of course, because it doesn't produce electricity
at the right moment in time, that's not enough.
You need to build more wind and solar to deal with that,
or you need to load shift it with storage, one of the two.
So if storage were free, then you could just build this,
right?
But storage is not free.
And so this is a fraction of the electricity demand that is met
with wind and solar plus storage,
and they have zero storage model, 12-hour storage model,
four-day storage model, and a 32-day storage model.
Four days and 32 days of storage is awfully expensive.
I don't consider those things to be viable.
So I'm only interested in the 12 hours of storage model.
So we're only going to look at this light green curve
here, light green curve.
This graph and this graph is the exact same graph.
It's just that this goes from 0 to 20.
And this graph is rescaled to go from 0 to 99.99/
So it's focusing on what's happening here,
which is the area of interest because we're interested
in questions of can you produce 99% of the energy from wind
and solar?
So if you are interested in running the entire grid just off
of wind and solar, and have the same grid reliability that we
have today, you would be somewhere around here, 99.9,
maybe in here, depending on how many hours of blackout
you're willing to tolerate a year.
So what my proposal is, we'll just
look at the 12 hours of storage, and we'll
look at 99.9% of electricity demand being
met by wind and solar, which is to say,
essentially the same reliability, and basically
no other technologies.
This is not an optimal system.
We know from these results, which are optimal systems,
that for a lowest cost system, you
need some kind of dispatchable stuff to make it lowest cost.
But that's not the question we're trying to answer.
We're not asking what is the optimal system.
We're just asking, is it even feasible at a reasonable price?
That's the question I want to answer right now.
So we'll look at these results.
And he has these results that are
100% wind, 75% wind, 50% wind, 25% wind, 100% solar,
different mixes between these two renewables.
So let's just pick the 50/50 mix, half wind, half solar,
and see what we can do with 50/50 mix and 12 hours
of storage.
So the first thing I want to do is note for you
that if we take the left axis, which is mean solar and wind
generation divided by demand, and we divide
that axis by the right axis, installed
capacity by mean demand, we get generation per unit capacity,
which is capacity factor.
Does that make sense?
So if we look at this intersection here, the 99.9%,
we have 1.7 divided by 6.5, which is about 25%.
Is that right?
So they're basically saying that as you move up
to these very high penetrations, the capacity
factor for the blend will be something like 25%.
And this gets to this earlier question that someone had,
because right now the capacity factors are 41% and 30%
But if you have this much, the average capacity
factor is going to drop.
So that makes sense.
So the first thing we need to do or the next thing we need to do
is to calculate the cost.
So this is now a couple of years out of date,
but the numbers are close to the same.
This is the EIA's table of cost, which remember,
comes from actual survey data of real plants, real installations.
So this is not a forecast.
It is for nuclear, but not for solar and not for wind.
So they have here some prices and they have here a total cost
and a transmission cost.
And so the first thing we want to do is subtract out,
again, I wish I had a laser pointer.
Subtract out the transmission cost just
to get the cost of the generation.
And so if you look here in this top plot,
you'll see I take this top right there,
I take the price of wind, which is $40.23
and I subtract out the transmission component $2.63
That's the cost of the wind farm, not the transmission line.
And then I multiply it by 0.41 divided by 0.25 in order
to rescale the cost for a lower capacity
factor, because the capacity factor is going
to go down from 41 to the 25.
Does that makes sense?
And so that tells me the new, whatever that number is,
that's the new, I guess the $62 per megawatt hour
is the price of the generation at the reduced capacity factor.
Same thing for solar, it's $29 per megawatt hour at the reduced
capacity factor for solar.
Now I need to add the transmission back in.
If we looked at these transmission costs,
they're about 6% and 10% of the total cost.
But I happen to know from other studies
that if you have this much wind and solar,
your transmission costs are going to be higher.
And a reasonable number, which I used to give the grid
lecture first, but now I'm going to give it later.
So you're just going to have to trust me on this for now.
A reasonable number is about 25% of the cost
will be transmission.
So we're going to add 25% to deal with transmission required
for this generation.
That gets us to this number.
Everyone's good so far?
All right, now we need to increase the storage
because Shaner says that we need 12 hours of storage
in order for this green line to be valid.
But this plot is if you read the footnote, footnote C, which
I did not put here, it's four hours of storage.
So we need to rescale the storage.
So how much does storage cost?
So what we do is we say we have to go back here to Sergeant
and Lundy's.
This used to be a part of your homework
which I'm no longer assigning.
So you don't have these numbers in your head.
So we go to the Sergeant Lundy table, which
is produced for the Department of Energy,
and they tell us how much it costs
to build all these different technologies.
And we see here they have solar and solar with storage.
And this is about four hours of storage.
So the capital cost difference is 1755 versus 1313.
So the amount of cost is roughly 25%
of the capital cost of a solar farm with storage, roughly 25%
of that cost, which is to say 1755 divided by 1313, is 25%.
Roughly 25% of that cost is going to be for the battery.
All right.
So 25% of the initial cost of solar,
so it's this number minus the transmission costs,
which is that, gives you $6.70 per megawatt hour for four hours
of storage.
We need 12 hours of storage.
So we're going to multiply that times 3.
And that comes out to $20 per megawatt hour for storage.
And we're going to add that back to not only the solar
but we're also going to add it to the wind.
So we need storage for both.
So here's your wind, plus transmission,
rescaled for lower capacity factor, add back in the storage.
And you get these numbers for each generation technology.
Yep?
AUDIENCE: Do I need to assume that the cost scales linearly
with storage?
PROFESSOR: It does assume that, yeah,
because this storage is lithium ion battery.
Yeah.
Yep?
AUDIENCE: I actually wonder.
I feel like I don't care about wind and storage as much.
Is it equally cheap for solar?
You have one battery pack and it's big,
but all your turbines are kind of scattered around.
PROFESSOR: Is it really cheap?
No, it's the same.
Yeah, and ultimately that all is going back to one node
where you're putting it on the grid.
Yeah.
And we need a 50/50 blend of these technologies.
That's what we chose, the 50/50 mix.
So we just average the two together to find the 50/50 mix.
It gets to $77 per megawatt hour.
And we need overbuild.
So I go back to this plot.
We chose the 50/50 mix.
And it says that mean generation divided by mean demand
where it's somewhere here, 1.7, we
have to generate 1.7 times the amount of electricity
in order to deal with the variability.
So we're going to take that number
and multiply it times 1.7 to deal
with the variability, where you get to $131 per megawatt hour.
So this is a grid run entirely by renewables
with 12 hours of storage and excess generation
to deal with the variability that operates 99.9% of the time.
So it's basically just as reliable as the current system.
And the cost is $131, which is essentially
the same price as base load nuclear or much cheaper
than load following nuclear.
So there's the AP1000 load following number.
And there is the MIT.
future of nuclear nominal cost estimate with 50% load
on schedule at 180 megawatt.
So it's just too cheap.
That's the problem.
If you have good wind and solar, it's
really hard to see how this becomes a problem.
So that's the bottom line.
In order to keep nuclear in the mix,
you have to find a way to get nuclear price way down.
And there are ideas and we're going
to talk about microreactors next week.
Any questions about wind and solar?
Or microreactors?
Yeah, next week.
Yeah.
Yeah?
AUDIENCE: On the study that you assigned talks about the fact
that building this amount of storage
might be unfeasible, at least with the current capacity
that there exists in the US.
Do these prices for storage for $12 storage account for that?
PROFESSOR: So I didn't do anything to account for that.
I don't know what would affect the feasibility.
Was it a lithium resource?
AUDIENCE: It was just the sheer amount
of batteries that needed to be produced
in order to supply the demand.
They argued that with the current,
for example, like gigafactories, it
would take something like 900 years
to get the amount of energy that they need.
And I'm also wondering, how this accounts
in terms of the laws of capacity over time
for these battery packs, which is what
happens with lithium batteries.
PROFESSOR: Yeah, so I believe--
I mean, this is a good question.
So these numbers, they call this four hours of storage.
I don't know how much this declines over the lifetime
of the battery packs.
So if they're calling it four hours of storage, but on average
it's really one hour, then this calculation is not correct.
And I don't have good information about that.
So we'd have to dig into what the EIA assumes
four hours of storage is.
In terms of the making of the batteries, I think first of all,
I would say that using lithium ion is a worst-case scenario.
There are lots of other storage technologies coming.
I think [? mion ?] is here, but it's expensive.
In terms of battery production, if there's a market demand,
capacity will emerge.
That is not something that particularly worries me.
What would worry me is something that I haven't looked
at in this study, which is there a lithium resource constraint?
The reason I didn't look at it is
I'm assuming that we will probably not use lithium.
We will use some kind of flow battery chemistry,
or lead battery, or something else that is cheap and abundant
but is not yet being deployed.
So I assume that this is a conservative calculation
because it uses lithium ion cost numbers.
But to answer these questions in an intelligent way
would require someone to really undertake
a study on battery technology.
I guess my final comment on this is
part of the reason why there is so much storage in Shaner's
model is that he doesn't have anything other than storage.
That's a problem in his model, and that's
why I signed the version that I did
because what we do is we say, OK, well,
why don't we have 1% dispatchable, like we
do natural gas just because it's built and it's there.
And we figure 99% decarbonization is probably
just as good as 100% decarbonization.
But you could also have 1% geothermal, something like that.
And you see the enormous cost reductions
that come about when you substitute battery
for dispatchable generation.
So again, this is not a cost optimized scenario.
This is not how it would actually be built.
This is just saying that wind and solar, in theory,
could do it.
Right?
That's all it's saying.
You wouldn't do it this way.
It would be foolish to do it this way.
You would much rather do it like this.
Yep?
AUDIENCE: When you discuss the rare earth metals as far
as the mineral resources for wind energy,
you mentioned, a total percentage of global resources.
Do you know that percentage of US resources or perhaps not?
PROFESSOR: I was looking for it, but I didn't actually
have time to look it up.
So one of the problems is the US Geological Survey
does not actually import by mineral
or just report total rare earth oxides.
And then you have to break it down by what
the average rare earth ore is.
But then that data is only available for the countries
that currently produce the rare earth.
So it turned out not to be an easy thing to do.
So I didn't have that data for you.
Yeah.
Anything else?
Yep?
AUDIENCE: Something really quick,
if you go back to the slide before--
PROFESSOR: Slide which?
AUDIENCE: The one with all the transmission costs that you
did the calculation on.
Transmission costs was rather low.
If we were actually to scale up in solar to the levels
that you're describing, wouldn't you expect it to be higher?
I mean, you said that 25% transmission to add.
I guess that kind of answers.
PROFESSOR: That is the answer.
Yeah, so I estimate that for nationwide transmission
that is needed to deal with renewables is about 25%
of the cost.
And that's based on historical transmission project costs.
I'll show you when we get to the grid talk.
I have a little regression model that tells you
how much it costs to build transmission.
AUDIENCE: And then just one more from before, you
were talking about the case when we had one gigawatt of capacity
of wind for the entire country.
You have an idea of how many wind
turbines that would actually take to do,
the number, just roughly?
PROFESSOR: 1 gigawatt of capacity
in terms of number of turbines?
We'd have to--
AUDIENCE: What the typical power of a turbine is.
PROFESSOR: Why don't you just Google
what is the average power of a current turbine?
Yeah, I mean, they've gotten very big
and I don't know enough about the mega-sized turbine turbines,
if they can be deployed anywhere.
So I don't know what the average size is.
But that's a very quick google.
You can do that yourself.
Yeah.
AUDIENCE: Let me show--
AUDIENCE: Could the expansion of solar or wind turbines
lead to deforestation, let's say,
or whatever other similar concerns about this?
PROFESSOR: I think I missed the first part.
AUDIENCE: The large scale expansion.
PROFESSOR: Of solar?
AUDIENCE: [INAUDIBLE] solar wind designs
of adverse effects on the environment,
for example, deforestation, et cetera.
PROFESSOR: Yeah.
So when I did my preparation for this talk,
I read a whole bunch of papers that have analyzed these things.
And the things that I talked about
are the things that the academics have investigated.
There are also-- and I mentioned these minor issues like noise,
and killing birds, and ecosystem repurposing,
and land use changes.
And there are people who have tried to calculate
the externalities for that.
So the way I think about these things,
and they're not limitations.
They're not technical feasibility limitations,
so I didn't put them in this talk.
But there are things that might raise the effective social cost
of wind and solar.
And so when we get to our talk on externalities,
where we're going to talk about, the safety
externalities from particulates, the safety
externalities from nuclear accidents, the safety
externalities or the social externalities
from noisy wind farms, we will come up
with numbers for all of these things
and see if things change dramatically.
Yeah.
Yep?
AUDIENCE: Is 12 hours of storage on a massive scale really
feasible, because my understanding is
that it's quite hard to get big batteries to hold a long charge
and discharge them every day without--
my understanding is 12 hours storage is actually
a pretty difficult technological line for us to get to.
PROFESSOR: Sorry.
Why would that be?
AUDIENCE: I mean, I don't know too much electrochemistry,
but there are some trade-offs in terms of how big you want
the battery to be, how quickly you want it to discharge,
and how long you want it to hold the charge.
So the longer duration storage battery you want,
it would either degrade very quickly,
if we want it to discharge at 0 to 100 every single night,
or it would be able to dispense energy at a very small--
PROFESSOR: So first of all, let me first
remind you that 12 hours of storage
is not how it will actually happen.
This is a hypothetical study that
is just to take Shaner's results and do something with them
interesting.
You wouldn't build all that storage.
You also wouldn't necessarily build it out lithium ion, so
those things aside.
So yeah, so the thing you're talking about
is basically a series parallel problem.
How many cells you put in series, how many cells you
put in parallel?
And if you want high intensity discharge,
then you wind up with the scenario where there's
a lot of internal resistance, and you
have more self-discharge.
I still think 12 hours is not that
bad from a self-discharge perspective.
That's my sense of the matter.
I think if you want to store for weeks, yeah,
your self-discharge is an issue.
I mean, this does 12 hours of storage.
But I think this is a niggle on a fake scenario.
So, I'm not worried about it.
Yeah.
All right.
Anything else?
All right.
I will see you Wednesday.