This Is What Happens After A Nuclear War.

The Doomsday clock, which symbolically measures how close the world is to nuclear war, is currently at 89 seconds until midnight – the closest it’s ever been. Over the past few years, we’ve also heard two presidents discuss the “nuclear option.” This is all to say that the world is surprisingly close to nuclear war. We’ve just become numb to that reality. But what happens after the nuclear bombs go off? Let’s take a look.

Trump's Budget Cuts: Is US Science About to Collapse?

We’re more than 100 days into the new Trump administration, and the president has made a lot of changes to federal science funding in the U.S. – budgets have been slashed, people have been fired, and 75% of American scientists are apparently considering leaving the country. What does all this mean for the future of science? Let’s take a look.

Everyone Is Giving Up On Climate Goals

With the Trump administration fully in control of the U.S., it appears that the tides are changing in the climate change discussion. The White House has already withdrawn from the Paris climate agreement, Trump wants to end what he’s calling “the green new scam,” and corporations around the world are abandoning their carbon neutrality pledges. How will this affect the climate change situation? Let’s take a look.

Sam Altman Thinks We Need To Change Our Social Contract

Recently, social media has been circulating a clip of OpenAI CEO Sam Altman discussing the idea that we will need to reconfigure society as we continue to improve AI. Is that true? What does it even mean? And how will the emergence of a truly intelligent AI reshape our society? Let’s take a look.

What Everyone Gets Wrong about AI

Most politicians totally misunderstand the trouble that artificial intelligence is going to bring. This isn’t a race for profit, it’s a race for power. And that power will be in the hands of a few very rich people. Does that sound like a good future?

German Techno-Realist vs American Techno-Optimist

Billionaire and Silicon Valley venture capitalist Marc Andreessen released a 5000 word essay coined the “Techno-Optimist Manifesto”, which covers his views of the world from the perspective of a “techno-optimist”. I read it so you don't have to.

Why I'm embarrassed to be German

In this video I want to make a personal statement to explain why I'm unhappy about the way that my country has been developing. Germany is not what it used to be.

Climate Change Violates Human Rights, Court Finds

An increasing number of people and organizations have sued their governments into acting on climate change, a emerging field of law known as "climate litigation". Are their cases successful? What are the potential consequences? Let’s have a look.

Time to get real about climate change

'm tired of both overly optimistic messages from climate activists and scare stories of the impending apocalypse. It's about time we get realistic. "Net zero” by 2050 is not a realistic goal and it's about time we admit it. I am afraid that many plans that are eating up money are fuelled by wishful thinking rather than by rational thought. Let’s have a look.

Scandal over Nuclear Phase-Out in Germany: What We Know

A recent investigation has revealed that the final steps in phasing out nuclear power in Germany was partly based on false information. And doesn’t look like it was a mistake, but a deliberate rewriting of what was originally accurate information. The ministry denies everything. A quick summary of what we know.

I thought Electric Cars Were the Future. I Changed my Mind.

I thought electric vehicles were the future of transportation. Not so much because they're clean, but because many car enthusiasts love them for their powerful acceleration. However, it's becoming increasingly clear that the necessary upgrades to the electric grid aren't going anywhere near fast enough to get the transition done according to plan. This is why I believe now we'll likely see a shift to hybrids in the near future.

Institute for Extinction Risk Shuts Down: What We Know

The Future of Humanity Institute announced last week that they have shut down. Located at the University of Oxford in the UK prior to its demise, the institute was one of the few places worldwide studying the risk of human extinction and a few other controversial research areas. Let’s have a look at the events leading to the institute’s closure.

Sulphur as Energy Storage -- Gamechanger?

For decades we have seen scientists and engineers trying to outdo each other in finding more efficient and cheaper ways of storing energy. A group from the German Aerospace Center now says that sulphur is the way forward. Let’s have a look

Climate Change Mitigation Plans Unrealistic and Potentially Dangerous, New Study Says

Some people have called me a doomer. Others call me a pessimist. Personally, I think I’m a realist. If I look at the plans that most nations have made to limit their contribution to climate change, I think it just isn’t going to happen. The people making these plans are either ill-informed, delusional, or lying, or maybe all of the above.

Now there’s a new publication just out of the University of Melbourne in Australia that, according to the press release has revealed a “huge climate mitigation challenge” and claims that the IPCC has overestimated how much carbon dioxide removal can realistically accomplish. Yes. Let’s have a look.

Crack Down On New Climate Denial! Nonprofit tells YouTube

The Center for Countering Digital Hate put out a new report a few days ago, in which they warn that climate misinformation continuous to flourish on YouTube. They want YouTube to take more action. I had a look and I don't like what I read.

Nuclear Power Comeback Update: Poland Authorizes Small Modular Reactors

Nuclear power is back in fashion in many countries because of its potential to decarbonize even energy-intense industry quickly. In its latest success, Poland has authorized the construction of 24 small nuclear reactors at six sites across the country.


The quiz for this week's science news is here.

I think net zero goals are bonkers, here's why

Everyone is talking about Net Zero. But Net Zero what? What does this even mean? Is it a reasonable goal? How far are we on the way? And do we have any chance of reaching it? For this video, we have collected all facts and numbers that you need to join the discussion.


NEW: This video comes with a quiz on QuizWithIt.

We Could Beam Solar Energy Down From Space. But Should We?

Solar power is a nice idea. Except for the issue with the clouds. And the nights. So, how about we instead put solar panels up in space and then beam the energy down? This futuristic idea is known as “Space Based Solar Power”. It’s been around since the 1960s, but in recent years several nations have launched projects to make it reality. I think they’re not kidding. Space-Based Solar Power is about to become a real thing. But how is it supposed to work? Is it a good idea to beam energy down from space? What are the pros and cons? That’s what we’ll talk about today.



Transcript, references, and discussion on Patreon.

The Trouble with 5G

[This is a transcript of the video embedded below. Some of the explanations may not make sense without the animations in the video.]



Did you know that there are now more mobile devices in the world than people? Whether you knew this or not, you probably did know that mobile phones work with the next best thing to magic, which is physics. All that data flies through the air in form of electromagnetic radiation. And since video resolution will soon be high enough for you to check whether I’ve plucked my eyebrows, wireless networks constantly have to be upgraded.

The fourth Generation of wireless networks, four G for short, is now being extended to five G, and six G is in planning. But five G interferes with the weather forecast, and six G brings more problems. What’s new about those wireless networks, and what’s the problem with them? That’s what we’ll talk about today.

The first four generations of wireless networks used frequency bands from four hundred Mega Hertz to roughly two GigaHertz. But there are limits to the amount of information you can transfer over a channel with a limited bandwidth. In fact there’s maths for this, it’s called the Shannon-Hartley theorem.

If you want to transfer more information through a channel with a fixed noise-level, you have to increase either the bandwidth or the power. You can’t increase the four G bandwidth, and there are safety limits on the power. The five G generation tries to circumvent the problem by using new bands at higher frequencies, going up to about fifty Giga Hertz.

Those frequencies correspond to wave-lengths in the millimeter range, which is why they’re called millimeter waves. There’s a reason they haven’t been previously used for telecommunication, and it’s not because millimeter waves are also used as good-byes for in-laws. It’s because radiation at the previously used frequencies passes through obstacles largely undisturbed, unless maybe the obstacle is a mountain. But millimeter waves can get blocked by trees or buildings, which isn’t great if you like calling people who aren’t within line of sight. “Could you pass me the salt, please? Thank you so much.”

So the idea of five G is to collect the signals from nearby mobile phones in what’s called a small cell of the network, and pass them on at low power to a bigger antenna that sends them long-distance at higher power. The five G network technology is currently being rolled out in most of the developed world. Cisco estimates that by next year 10 percent of mobile connections will use 5G.

Five G is controversial because it’s the first to use millimeter waves and the health effects have not been well studied. I already talked about this in a previous video but let me be clear that I have no reason to think that five G will have any adverse health effects. To the extent that research exists, it shows that millimeter waves will at high power warm up tissue, and that’s pretty much it.

However, the studies that have been done leave me wanting. Last year, one of the Nature journals published a review on 5G mobile networks and health. They looked at 107 experimental studies that investigated various effects on living tissue including genotoxicity, cell proliferation, gene expression, cell signaling, etc.

The brief summary is that none of those studies found anything of concern. However, this isn’t the interesting part of the paper. The interesting part is that the authors rated the quality of these 107 studies. Only two were rated well-designed, and only one got the maximum quality score. One. Out of 107.

The others all had significant shortcomings, anything from lack of blinding to small sample sizes to poor control of environmental parameters. In fact, the authors’ conclusion is not that five G is safe. Their conclusion is: “Given the low-quality methods of the majority of the experimental studies we infer that a systematic review of different bioeffects is not possible at present.”

Now, as I said, there’s no reason to think that five G is harmful. Indeed, there’s good reason to think it’s not, because millimeter waves have been used in medicine for a long time and for all we know they only enter the upper skin layers.

But I am a little surprised that there aren’t any good studies on the health effects of long-term radiation exposure in this frequency range. The 5G network has been in the planning since 2008. That’s 14 years. That’s longer than it takes NASA to fly to Pluto!

So scientists say there’s nothing to worry. Well, they also said that smoking is good for you and alcohol doesn’t cross the placenta and that copies of you live in parallel universes. As a scientist myself, I can confirm that scientists say a lot when the day is long, and I would much rather see data than just take word for it. Only good thing I have to tell you on the matter is that the World Health Organization is working on their own review about the health risk of five G which is supposed to come out by December.

Ok, while we wait to hear what the WHO says about the idea of irradiating much of the world population with millimeter waves, let’s talk about a known side-effect of five G: It’s a headache for atmospheric scientists, that’s meteorologists but also climate scientists. And yes, that means 5G affects the weather forecast.

You see, among the most important data that goes into weather and climate models is the amount of water vapor in the atmosphere. This is measured from satellites. This movie shows the average amount of water vapor in a column of atmosphere in a given month measured by NASA's Aqua satellite. Accurate measurements of the atmospheric water content are essential for weather forecasts.

You measure the amount of water vapor by measuring electromagnetic radiation that is scattered by the water molecules in the atmosphere. Each molecule emits radiation in particular frequency ranges and that allows you to count how many of those molecules there are. It’s the same method that’s used to detect phosphine in the atmosphere of Venus which we talked about in more detail in this earlier video. The frequency that satellites use to look for water is – you guessed it! – 23.80 Giga Hertz (Table 1, first line).

The issue is now that this water vapor signal is uncomfortably close to one of the 5G bands which covers the range from 24 point 25 to 27 point 5 Giga Hertz. You might say that’s still four hundred Mega Hertz away from the water vapor measurements, and that’s right. But the five G band doesn’t abruptly stop at a particular frequency, it’s more that it tapers out. The emission outside of the assigned band is called leakage. That leakage creates noise. And this noise is the problem.

You see, the weather forecast today sensitively depends on data quality. In recent decades, weather forecast has improved a lot. In this figure you see how much more you can trust the weather forecast today than you could a few decades ago. In 1980, a three-day forecast in the Norther Hemisphere was only correct about 85 percent of the time.

Today it’s correct more than 98 percent of the time. And this isn’t just about deciding whether to bring an umbrella, it’s relevant to warn people of dangerous weather events. A 72-hour hurricane warning today is more accurate than a 24-hour warning was 40 years ago.

The reasons for this improvement have been better computers, better models, but also weather satellites that collect more and better data. And that brings us back to the water vapor signal and the 5G troubles.

The water vapor signal is weak and the strongest contribution usually comes from low altitudes. That’s right, typically the biggest fraction of water vapor in the atmosphere isn’t in the clouds but close to the ground. If you took all the water in the atmosphere and put it on the ground you’d get about 2.5 cm. The clouds alone merely make a tenth of a millimeter.

Those are average values and the details depend on the weather situation, but in any case it means that the water vapor signal is very sensitive to noise near the ground. It’s like trying to hear a whisper in a noisy room. To make matters worse, most of the 5G noise will come from densely populated areas so we’ll get the least accurate forecast where people actually live.

Meteorologists are not happy. This is partly because they had to put away the crystal balls. But the bigger reason is that in 2019, The National Oceanic and Atmospheric Organization in the United States, NOAA for short, did an internal study on the impacts of 5G. In a federal hearing, Neil Jacobs, a former NOAA Administrator, said that the current 5G regulations “would degrade the forecast skill by up to 30 percent, so, if you look back in time to see when our forecast skill was roughly 30 percent less than it was today, it’s somewhere around 1980. This would result in the reduction of hurricane track forecast lead time by roughly 2 to 3 days”

The Secretary-General of the World Meteorological Organization, Petteri Taalas, is also concerned. He said: “Potential effects of this could be felt across multiple impact areas including aviation, shipping, agricultural meteorology and warning of extreme events as well as our common ability to monitor climate change in the future.” His organization calls for strict limits on the 5G leakage.

But well, as they say, there are two sides to every story. On the other side is for example Brad Gillen, executive vice president of the CTIA, that’s a trade association which represents the wireless communications industry in the United States.

He wrote a blogpost for the CTIA website claiming that the effect of five G on the weather forecast is “an absurd claim with no science behind it” He says the study done by NOAA used an obsolete sensor that it’s not in operation. Then he pulls the China card “The Trump Administration has already made its call, and it is time we all get on the same page as China and our other rivals most certainly are today.”

That wasn’t the end of the story. The atmospheric scientist Jordan Gerthan from the University of Wisconsin at Madison, pointed out that the reason the NOAA study mentioned a sensor that isn’t being used on satellites today is that this particular design was cancelled. It was, however, replaced by a very similar one so the argument is a red herring.

In response, a different CTIA guy wrote another blogpost claiming that “5G traffic will be hundreds of megahertz away from the band used in weather data collection”, so he completely ignores the leakage problem and hope his readers don’t know any better. On the other hand, NOAA didn’t publish their study and that didn’t win them any favors either.

However, in 2020, researchers from Rutgers University did their own study. They modeled the leakage of five G into the water vapor signal and evaluated its impact on a weather forecast by using old data. They did a mock 12 hour forecast, one without 5G and then two with different levels of leakage power.

As you can see in these figures, they found that the 5G leakage can affect the forecast up to zero point nine millimeter in precipitation and 1 point three degrees Celsius in temperature at two meters altitude. And it’s not just the value that changes but also the location. That’s a significant difference which would indeed degrade weather forecast accuracy noticeably. Maybe not as dramatic as the NOAA guy claimed, but certainly of concern.

What has happened since? In July 2021, the American Government Accountability Office released a report in which they just said that the arguments about the impact of 5G on weather forecast were “highly contentious.” Despite the lack of consensus, the official US position became to adopt fairly weak rules on the power leakage. They were then adopted by the International Telecommunication Union which is based in Geneva, Switzerland and which writes the global rules.

But most countries in the European Union so far just haven’t auctioned off the troublesome frequency band. Maybe they’re waiting to see how things pan out in the USA, the guinea pig of countries.

And then there’s six G, the 6th generation of wireless networks. This is already being planned, and it’s supposed to use bands at even higher frequencies, above one hundred GigaHertz and up into the TeraHertz range. Six G is supposed to usher in the metaverse era with augmented and virtual-reality and ultrahigh-definition video so we can finally watch live streams of squirrel feeders from New Zealand on our contact lenses.

According to the tech site LiveWire “6G is just the natural progression towards faster and better wireless connectivity…Ultimately, whether it’s with 6G, 7G, or another “G”, we’ll have such incredibly fast speeds that no progress bars or wait times will be required for any normal amount of data, at least at today’s standards. Everything will just be available...instantly.” And who would not like that?

But of course the 6G range, too, is being used by scientists for measurements that could be compromised. For example, NASA measures ozone around 236 GigaHertz, and carbon monoxide at about 230.5 GigaHertz. So we can pretty much expect to see the entire 5G discussion repeat for 6G.

How can the situation be solved? For 5G, the World Meteorological Organization is trying to negotiate limits with the regulating agencies in different countries. They demand that cell towers operating close to weather satellite frequencies should be limited to transmit at minus 55 dBW (Decibel Watt) for out-of-band emission, so that’s the leakage.

The European Commission has agreed on –42 decibel watts for 5G base stations. The FCC in the US set a limit at –20 decibel watt. This is a logarithmic scale, so this is more than 30 orders of magnitude above the limit the meteorologists ask for.

What do we learn from this? When a new technology is developed, scientists usually get there first. And when everyone else catches up, they’ll interfere with the scientists, often metaphorically but sometimes literally.

This isn’t a new story of course. You only have to worry about noise from railways if you have railways and there are actually trains going on them. But a high-tech society also relies on the accuracy of data, so this is a difficult trade-off. There are no easy ways to decide what to do, but I think everyone would be better off if the worries from scientists were taken more seriously in the design stage and not grumpingly acknowledged half through a global roll-out.

No Sun, No Wind, Now What? Renewable Energy Storage

[This is a transcript of the video embedded below. Some of the explanations may not make sense without the animations in the video.]


Solar panels and wind turbines are great – so long as the sun shines and the wind blows. What if they don’t? You could try swearing at the sky, but that might attract your neighbor’s attention, so I’ll talk about the next best option: storing energy. But how? What storage do we have for renewable energy, how much do we need, how expensive is it, and how much does it contribute to the carbon footprint of renewables? That’s what we’ll talk about today.

I’ve been hesitating to do a video about energy storage because in all honesty it doesn’t sound particularly captivating, unless possibly you are yourself energy waiting to be stored. But I changed my mind when I learned the technical term for a cloudy and windless day. Dunkelflaute. That’s a German compound noun: dunkel means “dark” and “flaute” means “lull”. So basically I made an entire video just to have an excuse to tell you this. But while you’re here we might as well talk about the problem with dunkelflaute…

The renewable energy source that currently makes the largest contribution to electricity production is hydropower with about 16%. Wind and solar together contribute about 9%. But this is electric energy only. If you include heating and transport in the energy needs, then all renewables together make it to only 11%. That’s right: We still use fossil fuels for more than 80% of our entire energy production.

The reason that wind and solar are so hotly discussed at the moment is that in the past two decades their contribution to electricity production has rapidly increased while the cost per kilo-Watt hour has dropped. This is not the case for hydropower, where expansion is slow and costs have actually somewhat increased in the past decade. This isn’t so surprising: Hydropower works very well in certain places but those places have been occupied long ago. Solar and wind in contrast still have a lot of unused potential, and this is why many nations put their hopes on them.

But then there’s the dunkelflaute and its evil brother, cold dunkelflaute. That’s when the sun doesn’t shine and the wind doesn’t blow, and that happens in the winter. It’s a shame there aren’t any umlauts in the word, otherwise it’d make a great name for a metal band.

It’s no coincidence that Germans in particular go on about this because such weather situations are quite common in Germany. The German weather service estimates that it happens on the average twice each year, that the power production from wind and solar in Germany is less than 10% the expected average for at least 2 days. Every once in a while these situations can last a week or longer.

Of course this isn’t an issue just in Germany. This figure shows the average monthly hours of dunkelflaute for some European countries. As you can see, they are almost all in the winter. A recent paper in Nature Communications looked at how well solar and wind can meet electricity demand in 42 countries. They found that even with optimistic extension scenarios and technology upgrades, no country would be able to avoid the problem.

The color in this figure indicates the maximum reliability that can be achieved without storage. The darker the color, the worse the situation. As you can see, without storage it would be basically impossible to meet the demand reliably anywhere with wind and solar alone. Even Australia which reliably gets sunshine can’t eliminate the risk, and Europe is more at risk than North America.

The situation might actually be worse than that because climate change might weaken the wind in some places and make dunkelflaute a more frequent visitor. That’s because part of the global air circulation is driven by the temperature gradient between the equator and the poles. The poles heat up faster than the equator, which weakens the gradient. What this’ll do to the wind isn’t clear – the current climate models aren’t good enough to tell. But maybe, just maybe, banking on stable climate patterns is not a good idea if the problem you’re trying to address is that the climate changes. Just a thought.

Ok, so how can we deal with the dunkelflaute problem? There are basically two options. One is better connectivity of the power grid, so that the risk can be shared between several countries. However, this can be difficult because neighboring countries often have similar weather conditions. A recent study by Dutch researchers found that even connecting much of Europe wouldn’t eliminate the risk. And in any case, this leaves open the question whether countries who don’t have a problem at the time could possibly cover the demand for everyone else. I mean, the energy still has to come from somewhere.

And then there’s the problem that multi-national cooperation doesn’t always work as you want. Instead of being dependent on gas from Russia we might just end up being dependent on solar power from Egypt.

The other way to address the problem is storing the energy until we need it. First, some technical terms: The capacity of energy storage is measured in Watt hours. It’s the power that the battery can supply multiplied by the discharge time until it’s empty. For example, a battery system with an energy capacity of 20 Giga Watt hours can power 5 Giga Watt for 4 hours before it’s empty. This number alone doesn’t tell you how long you can store energy until it starts leaking; this is something else to keep in mind.

At the moment, the vast majority of energy storage is pumped hydro which means you use the energy you don’t need to pump water up somewhere, and when you need the energy, you let the water run back down and drive a turbine with it. Currently more than 90 percent of energy storage is pumped hydro. Problem is, there are only so many rivers in the world and to pump water up a hill you need a hill, which is more than some countries have. Much of the increase in storage capacity in the past years comes from lithium ion batteries. However, they still only make a small contribution to the total.

To give you a sense of the problem: At present we have 34 Giga Watt hours of energy storage capacity worldwide, not including pumped hydro. If you include pumped hydro, it’s 2 point 2 Tera Watt hours. We need to reach at least 1 Peta Watt hours, that’s about 500 times as much as the total we currently have. It’s an immense challenge.

So let us then have a look at how we could address this problem, other than swearing at the sky and at your neighbor and at the rest of the world while you’re at it. All energy storage systems have the same basic problem: if you put energy into storage, you’ll get less out. This means, if we combine an energy source with storage, then the efficiency goes down.

Pumped hydro which we already talked about has an efficiency between 78 percent and 82 percent for modern systems and can store energy for a long time. The total cost of this type of storage varies dramatically depending on location and the size of the plant, but has been estimated to be between 70-350 dollars per kilo Watt hour of energy storage.

Pumped hydro is really remarkable, and at least for now it’s the clear winner of energy storage. For example, in Bath County Virginia, they store 24 Giga Watt hour this way. But pumped hydro also has its problems, because for some regions of the world, including the united states, climate change brings more drought and you can’t pump water if you don’t have any.

A similar idea is what’s called “gravitational energy battery” which is basically pumped hydro but with solids. You pile concrete blocks on top of each, store the gravitational energy, and when you let the blocks back down, you run a dynamo with it. Fun, right? These systems are very energy efficient, about 90%, and they store energy basically indefinitely. But they’re small compared to the enormous amounts of water in a reservoir.

The Swiss company EnergyVault is working on the construction of one such plant in China which they claim will have 100 Mega Watt hours energy storage capacity. So, nice idea but it isn’t going to make much of a difference. I totally think they should get a participation trophy for the effort, but keep in mind we need to reach 1 Peta Watt hour. That’d be about 10 millions of such plants.

A more promising approach is compressed air energy storage or liquefied air energy storage. As the name suggests, the idea is that you compress or liquefy air, put it aside, and if you need energy, you let the air expand to drive a generator. The good thing about this idea is that you can do it pretty much everywhere.

The efficiency has been estimated to lie between 40 and 70 percent, though it drops by about zero point two percent per day due to leakage, and that’s the optimistic estimate. The costs lie between 50-150 dollars per kilo Watt hour, so that’s a little less than pumped hydro and actually pretty good. This one gets the convenience award. The McIntosh Power Plant in Alabama is a very large one, with capacity of almost three Giga Watt hours.

Another option is thermal energy storage. For this you heat a material, isolate it, and then when you need the energy you use the heat to drive a turbine, or you use it directly for heating. You can also do this by cooling a substance, then it’s called cryogenic energy storage.

The problem with thermal energy storage is that the efficiency is quite low; it typically ranges from only 30 percent to 60 percent. And since no insulation is perfect, the energy gets gradually lost. But being imperfect and losing energy is something we’re all familiar with, so this one gets the sympathy award.

In this video we’re looking into how to store solar and wind energy, but it’s worth mentioning that some countries use thermal energy storage to store heat directly for heating which is much more efficient. The Finnish company Helen Oy, for example, uses a cavern of 300 thousand cubic meters to store warm seawater in the summer which gives them about 11.6 Giga Watt hours. That’s a lot, and the main reason is that it’s just a huge volume.

As I mentioned previously, most of the expansion in energy storage capacity in the past decade has been in lithium-ion batteries. This one’s the runner-up after pumped hydro. They have a round trip efficiency of 80 to 95 percent, and a lifetime of up to 10 years.

But we currently have only a little more than 4 Giga Watt hours in lithium ion batteries, that’s a factor 500 less than what we have in pumped hydro. It isn’t cheap either. The cost in 2018 has been estimated with about 469 dollars per kilo Watt hour. It’s expected to decrease to about 360 in 2025 but this is still much more expensive than liquefied air.

And then there’s hydrogen. Sweet, innocent, hydrogen. Hydrogen has a very low round trip efficiency, between 25 and 45 percent, but it it’s popular because it’s really cheap. The costs have been estimated with 2 to 20 dollars per kilo Watt hour, depending on where and how you store it. So even the most expensive hydrogen storage is ten times less expensive than lithium ion batteries. In total numbers however, we currently have very little hydrogen storage. In 2017 it was about 100 Mega Watt hour. I suspect though that this is going to change very quickly and I give hydrogen the cheap-is-neat award.

Those are the biggest energy storage systems to date but there are a few fun ones that we should mention, for example flywheels. Contrary to what the name suggests, a flywheel is neither a flying wheel nor a gymnastic exercise for people who like being wheeled away in ambulances, but it’s basically a big wheel that can rotate and that stores energy because angular momentum is conserved.

Those flywheels only store energy up to 20 Mega Watt hours for a couple of minutes, so they’ll not solve the dunkelflaute problem. But they can reach efficiencies up to 95 percent, which is quite amazing really. They also don’t require much maintenance and have very long lifetimes, so they can be useful as short-term storage buffers.

There are also ultracapacitors which store electric energy like capacitors, just more of it. They have a high efficiency of 85-95 percent, but can store only small amounts of energy, and are ridiculously expensive, up to 60,000 dollars per kilo Watt hour. 

The difficulty of finding good energy storage technologies drives home just how handy fossil fuels are. Let me illustrate this with some numbers. A kilogram of gasoline gives you about 13 kilo Watt hours, a kilogram of coal a little less, about 8 kilo Watt hours. A lithium ion battery gives you only 0 point 2 kilo Watt hours per kilo gram. A kilo gram of water at one kilometer altitude is just 2.7 Watt hours, that’s another factor thousand less.

On the other hand, 1 kilo gram of Uranium 235 gives you 24 Giga Watt hours. And one kilogram of antimatter plus the same amount of matter would produce 25 Tera Watt hours. 25 Tera Watt hours! With a ton of it we would cover the electric needs of the whole world for a year.

Okay, so we have seen energy storage isn’t cheap and it isn’t easy, and we need a lot of it, fast. In addition, putting energy into storage and getting it back out inevitably lowers the efficiency of the energy source. This already doesn’t sound particularly great, but does it at least help with the carbon footprint? After all, you have to build the storage facility and you need to get those materials from somewhere, and if it doesn’t last long you have to recycle it or rebuild it.

A paper in 2015 from a group of American researchers found that carbon dioxide emissions resulting from storage are substantial when compared to the emissions from electricity generation, ranging from 104 to 407 kilo gram per Mega Watt hour of delivered energy.

This number probably doesn’t tell you anything, so let me put this in context. Coal releases almost a ton of carbon dioxide per Mega Watt hour. But the upper limit of the storage range is very close to the lowest estimate for natural gas. And remember that you have to add the storage on top of the carbon dioxide emissions from the renewables. Plus, the need to store the energy makes them less efficient.

In the case of lithium-ion batteries, the numbers strongly depend on how well you can recharge the batteries, that is, how many cycles they survive. According to a back-of-the-envelope estimate by the Chemical Engineer Robert Rapier, for 400 cycles the emissions are about 330 kilo gram carbon dioxide per Mega Watt hour but assuming 3000 cycles the number goes down to 70 kilo gram per Mega Watt hour.

A few thousand cycles seem possible for current batteries if you use them well. This estimate roughly agrees with a report that was published about two years ago by the Swedish Environmental Research Institute. So this means, depending on how often you use the batteries, the carbon footprint is somewhere between solar and natural gas.

How big the impact of storage is on the overall carbon dioxide emissions of wind and solar then depends on how much, how often and for how long you put energy into storage. But so long as it’s overall a small fraction of days this won’t impact the average carbon-dioxide emissions all that much.

Let’s put in some numbers. A typical estimate we’ve seen used in the literature is something like 10% of days that you’d put energy into storage. If you take this, and one of the middle-of-the-pack values for energy storage and assume it’s 80 percent efficient, then the carbon footprint of wind would increase from about 10 to about 30 kilogram per Mega Watt hour and that of solar from about 45 to about 65. So, they are both clearly still much preferable to fossil fuels, but the need to store them also makes nuclear power increasingly look like a really good idea.

What do we learn from this? At least for me the lessons are that first, it makes sense to use naturally occurring opportunities for storage. Our planet has a lot of water, and, unlike me, water has a high heat capacity. Gravitational energy doesn’t leak, location matters, and storing stuff underground increases efficiency. Second, liquid air storage has potential. And third, there’s a lot of energy in uranium 235.

Did you come to different conclusions? Let us know in the comments, we want to hear what you think.