I am often reminded by my
friends that renewable power like wind and solar are making tremendous
strides—their deployment is rising exponentially, and costs are coming down. As
a result, my friends claim, greenhouse gas emissions in the US are declining. They
note that renewable sources are a cheaper alternative than coal power in many
parts of the world. We should therefore close down the coal plants and replace
them with wind and solar farms. For backup these installations should use
batteries, whose costs, I am told, are also plummeting. Indeed, Mr. Bloomberg
has pledged $500 million to hasten such a transition.
I wish I could share their
positive outlook. Deployment of renewable power technologies has been
increasing, but even after twenty years of this exponential growth, in 2018
they provided a mere 3% of global energy, while fossil fuels accounted for over
80%. Wind and solar simply do not scale. Here’s a graphic from the BP
Statistical Review of World Energy, 2019. It shows the global primary energy
consumption various sources in MTOE, metric tons of oil equivalent. Yes, you
can see the increase in renewables, but the even larger increases in
consumption of fossil fuels has led to emission of ever-increasing amounts of
carbon dioxide.
There has indeed been a
decline in the CO2 emissions in the US electricity sector. This
decline, though, is largely a result of switching from coal to natural gas, and
not due to the rise renewables. Wind and solar contributed only a small
fraction. Here are the data from the US Department of Energy’s Energy
Information Administration that illustrate the point.
The falling price of wind
and solar power that the proponents point too does not reflect their true
costs. Policies such as Renewable Portfolio Standards, subsidies, and
alternate revenue streams such as curtailment allowances hide the costs. Wind
and solar installations must come with the disclaimer, “Batteries Not
Included.” If one includes the cost of storage and other systems for
managing their intermittency, the cost of wind and solar would be considerably
higher.
Consider closing a 1-GW
coal power plant, say the Bruce Mansfield in Pennsylvania, and replacing it
with renewables. First, to get the same number of GWh of electricity over a
year, you will have to install about 3 GW of wind or solar facilities to
account for their reduced capacity factors. Installation costs are often
reported in $/W, and so for starters we have allow for the higher installed
capacity to get the same amount energy.
Next, you will also have to
provide some storage to cover for days that wind might not blow or the clouds
obscure the sun. Currently, natural gas plants are used to provide backup power
because natural gas in cheap—thanks to fracking—and they can ramp up quickly.
But natural gas is a fossil fuel, and we do not want that; instead we want to
put in batteries for backup. If we choose to provide storage for just 100 hours,
a tad over four days; that would mean installing battery storage capacity of
100 GWh. How much lithium would that require? According to Tahil, theoretically you could
store 1 kWh of energy from 73 g Li in lithium ion batteries. Note that g/kWh
are the same as Tons/GWh. Thus, theoretically, you would need 73 Tons for
storing 1 GWh of electrical energy.
In practice, the amount
required is often 3 to 4 times higher because of several factors: discharge
rate, irreversible losses, reaction kinetics, etc. Tahil discusses these issues
in the paper and concludes by suggesting a requirement of 320 g Li per kWh of
storage. In other words, shutting down just a 1-GW coal plant and replacing it
with renewables and providing only 100 hours of storage would require 32,000
Tons of lithium. To put that amount in perspective, note that in 2018 the
global production of lithium was 62,000 Tons.
In other
words, about half the world’s lithium supply would go for backing up renewables
to replace one coal plant! Sure, we could expand the production of
lithium, but how soon could we scale it up to get millions of tons per year to
replace all the coal power? We do not have the luxury of time. As Greta
Thunberg and children all over the world implore us, we must take action to
combat climate change. Let's do right by them and not make the problem worse
than it already is.
Time to get real and
embrace nuclear power!
