How droughts can cause energy shortages

An exposed riverbed rock with carvings of dates visible back to 1616. Some people are resting their bare feet against it.
Image: Libor Elleder (distributed via, licensed CC-BY-3.0

Today I learned about “hunger stones“. These are rocks in the River Elbe that are submerged in all but the lowest water conditions. Carvings on them commemorate historical droughts back to the fifteenth century and warn that if the stone is visible, famine will follow. One of the most poignant inscriptions translates as “If you see me, weep”. As Europe faces what may be its worst drought in 500 years, these stones are appearing… and while famine is less inevitable in a world of globalised food supply, it’s interesting to see the knock-on effects on energy.

Shipping companies have been warning for some time that water levels on Europe’s rivers have been approaching a level at which cargo traffic would have to stop. Indeed, when I was sitting by the Rhine on holiday two weeks ago I noticed that the laden barges were sitting higher in the water than usual – that they were sailing with reduced loads to cope with a shallower river. Since then parts of the river have effectively closed as predicted, as shipping companies decide that there is not enough water to operate safely or economically.

The closure of major transport routes is concerning for supply chains in general, but one of the major cargos carried by these rivers into inland Europe is coal, for power stations. So a shortage of water can translate to a shortage of energy.

Over in France, meanwhile, the country’s major rivers are at historically low flow rates… and that, combined with high water temperatures from this summer’s heatwave, has obliged nuclear power stations that rely on rivers for cooling to reduce their output to comply with environmental regulations. With reduced outputs on top of a lot of maintenance shutdowns this year, the country most famous for embracing nuclear power has become an energy importer.

Norway is another nation that is traditionally energy-independent: while they do have a lot of oil and gas, they use little of it domestically because their electrical grid runs almost entirely off hydro power, and on top of the fossil fuels they are usually a net exporter of clean electricity. But without rainfall there’s less hydro power, and with their reservoirs at unseasonally low levels the Norwegian authorities are considering restricting electricity exports to protect their domestic supply.

None of that affects the UK directly: we don’t use inland waterways for cargo, our nuclear plants are all on the coast, and we only have a small amount of hydroelectricity. But the knock-on effects of a worsening energy shortage in Europe will certainly be felt here, in the form of higher wholesale energy prices.

I mention all of these things together because they’re a clear demonstration of the interconnectedness of the systems that we take for granted. Our power and other industrial infrastructure was designed for the time in which it was built, plus forseeable changes – and nobody (a figurative nobody) foresaw parts of the Loire running dry, or the Rhine becoming impassable to coal barges.

This is a part of something sometimes referred to as the “Energy-water nexus“: the idea that energy supplies depend on water, and water supplies depend on energy, and that developing more of one usually requires more of the other. It’s interesting to think about whether this interdependence might be weakened by increasing use of renewable energy. Wind and solar probably rely on water less than thermal plants do… but in the future, will we see drought-related curtailment of freshwater hydrogen production?

Posted by simon in The wider world

Here’s why UK tides are soon going to play a much bigger part in powering your home

I wrote this article at the request of an editor from The Conversation, who wanted to know about the current state of, and future prospects for, tidal energy. It was published there on 14th April 2022, and is licensed CC BY-NC 4.0.

The Conversation

Tidal energy has long lurked at the back of the UK’s renewable energy arsenal, outshone by its wind and solar counterparts due in part to early issues with technology readiness and high costs.

Yet with recent research showing it could provide 11% of the UK’s electricity needs – and with significant government investment in the pipeline for UK projects – its future is looking ever brighter.

Tides are large movements of water around the Earth, powered by the gravitational pull of the Sun and Moon. In areas with particularly strong tides, we can harvest some of this power using turbines – similar to wind turbines, but underwater – that turn as water flows past them. This approach is more popular at present than previous ideas of using tidal barrages which are similar to dams, mostly because its environmental impacts are less severe.

In the last decade, the global tidal energy industry has demonstrated that siphoning energy from the sea works predictably and reliably. Around a dozen experimental turbine designs have been generating electricity in Scotland, Wales, Canada, China, France and Japan, many of them supplying power to homes and businesses.

The UK’s first “commercial” tidal energy projects, led by developers SIMEC Atlantis and Nova Innovation, both have multi-turbine arrays in the water in Scotland. The largest of these can currently produce six megawatts of power: that’s about the same as two or three onshore wind turbines, providing enough energy to run a few thousand homes. Expansion of the project is already underway. Over in the Faroe Islands, tidal developer Minesto has just announced plans for a 120 megawatt array which would supply 40% of the islands’ energy needs.

A ship's crane lifting a turbine from a quay
Green Energy Futures/Flickr, CC BY-NC-SA

Tidal turbine designs tend to be divided by one big question: whether it’s best for them to float, or to be mounted on the seabed. Floating turbines are easier to access for maintenance, and they benefit from faster-flowing water near the surface. But those on the seabed are less affected by storms and – in deep enough water – could allow ships to sail freely above them. It’s not yet clear whether one approach will win out, or whether the choice will depend on the location.

Either way, now that it has working technology in its hands, the tidal power industry needs to demonstrate that it can bring costs down. Luckily, there’s precedent here in the story of offshore wind. With the help of government support in the UK and elsewhere, offshore wind developers around the world have cut costs by close to a third over the last decade, and further reductions are expected thanks to ongoing research and development.

Money Matters

The cost of tidal energy may never be as low as that of wind. That’s partly because tidal turbines can’t be scaled up in size in the same way as wind turbines (in a limited depth of water, you can only build so big), and partly because doing things under the sea is usually more expensive than doing them on the surface (it’s a harsher, less accessible environment). But matching costs may not even be necessary.

As critics are keen to point out, the wind does not always blow, the sun does not always shine, and the tide is not always flowing: so to build a resilient low-carbon electricity system, we’ll need to use a range of different energy sources rather than relying only on that which is cheapest.

A ship lowing a turbine into the water
Glen Wallace/Flickr, CC BY-ND

Tidal power offers the unique advantage that while its output will vary over time, that variation is predictable years in advance by understanding the orbits of the Earth and Moon. This means that grid operators will be able to plan for the varying output of tidal turbines, and schedule other sources to fill in the gaps.

Fortunately, the UK government seems to be stepping up to help the tidal industry. The latest round of the UK’s “Contracts for Difference” renewable energy funding contains a “pot” for tidal energy, so that it doesn’t have to compete with cheaper technologies like offshore wind – for now. And the recently published British Energy Security Strategy promises rather fiercely to “aggressively explore” tidal and geothermal energy technology.

Tidal energy is never going to be a big player at the global scale in the same way as wind or solar, because only a few parts of the world have strong tides. And unfortunately, it won’t be ready in time to help with the energy price crisis that we face right now.

But for those places with strong tides, including the UK, it has significant prospects, with a global market estimated by some analysts at £130 billion. And there may be potential in developing turbine tech further to take advantage of slower, but more consistent, ocean currents like the Kuroshio current off the coast of Japan.

Tidal energy technology works, and it’s here to stay. Now, the most efficient way to get it powering our homes and businesses is to build more of it.

Posted by simon in Publications, Written elsewhere

New website!

As you’ve probably noticed if you’re reading this, I have a new website. It’s very much like the old website, except that (a) it’s on up to date versions of everything, from WordPress to the underlying database, and (b) it works. The theme powering the old site – a theme which I liked very much, and which I paid money for years ago – had been unmaintained for a long time, and a recent WordPress update broke it beyond my capability to bodge.

Rather than just sub in a new theme, I took the opportunity to rebuild it from scratch and thus get rid of some of the background cruft from 2016. One result is that some old posts might not quite look right, or in a very few cases might actually have missing images, due to plugins that they depended on being gone. If you find anything missing, rather than just ugly, please let me know. Similarly, if you find anything that looks wrong on the main pages, please tell me about that too. If you mostly want to complain about the kerning of one or two of the Google Fonts that I’m using, join the queue – the “SIMON WALDMAN” title text has been tweaked manually and it still doesn’t look quite right. I’ll probably get used to it.

On the plus side, everything should hopefully be a bit more maintainable now. And I might even get around to writing up one or two of the posts I have drafted. Maybe. If I have time. Perhaps.

Posted by simon in Website updates

After Glasgow

I haven’t been following the negotiations at COP26 very closely. And I haven’t examined the eventual agreement in great detail, instead following the insight of commentators I trust. It seems, from what I’ve read, that while there are some incremental steps forward in the detail – strengthening of language, and so forth – mostly the parties have agreed to kick the can down the road another year. If readers have better insight and want to contradict that, they are most welcome to do so, but I think it’s fair to say that any climate summit that ends in its president apologizing and breaking down in tears is not what the world wanted to see.

On social media people have noted that the commentators who, two weeks ago, were talking about a “last chance for humanity” are now praising the small steps forward. Greta Thunburg has, of course, summed up her view with eloquence:

The #COP26 is over. Here’s a brief summary: Blah, blah, blah.

@GretaThunberg / Twitter

Twelve years ago, before I had even started studying renewable energy, I wrote a blog post on another site entitled “After Copenhagen”. That was the first COP that was a mainstream media event, and the first one – thanks partly to Barak Obama’s involvement – that felt as though it might get somewhere. In the end it achieved little for various reasons, and there was a temptation to give up. I did a lot of thinking back then, and this is what I concluded:

“I’ve spent a certain amount of time thinking “If I think that the cause is hopeless, why am I wanting to work in the renewable energy and/or energy efficiency fields?”. The answer is that… every little still helps. Yes, low-lying countries are almost certainly doomed. Yes… wars will be caused and exacerbated, many will starve or die of disease… but for every bit that we can reduce our emissions, less of this will happen. The fact that the situation is so terrifying, depressing, and hopeless, even to those of us who probably won’t suffer the worst (or at least the first) of the direct effects, doesn’t mean that we can’t try to lessen it.”

I still believe this. We missed the 350ppm and 400ppm targets that were talked about at Copenhagen. It seems very likely that we will miss the 1.5°C target that is increasingly believed to be important. But it’s still worthwhile to make things better than they otherwise would be. If global efforts get us to 2.6°C, as is suggested by the current NDCs, that’s bad, but it’s better than it could be. As I wrote in some internal training materials recently, under the heading “A note about missing targets”,

“It’s too late to prevent climate change – it’s already happening. It’s probably too late to keep to 1.5°C, and 2°C looks hard as well. But this isn’t a binary thing: it’s wrong to say “we missed the target, may as well give up”. 3°C is better than 4°C, which is better than 6°C. Some harm is locked in, but we can minimise how much more.”

That’s the thought that keeps me going now, as it does on a regular basis away from the COP cycle. In the words of Mary Heglar, “home is always worth it“.

Posted by simon in Reflective, The wider world

Fuel shortage and EVs

As UK readers will know, much of the country is currently suffering a fuel shortage. While there is, as I understand it, a small supply deficit due to a lack of tanker drivers, the main problem is that when people heard about that deficit they all filled up their cars at once, causing a large spike in demand (which will be balanced by low demand for a couple of weeks as everybody has full tanks).

I’m not here to talk about Brexit, HGV drivers, or fuel crisis management. I’m not even here to be smug about driving a partly electric car. What I want to point out is the light that this throws on an argument we sometimes see against EVs:

Sometimes one hears people saying that if everybody in the UK went electric, the grid couldn’t cope because of the load of all the cars charging at once. And that would be a reasonable concern, if we were talking about first-generation EVs that needed charging every night.

But to within a factor of two, today’s EVs have the same range as petrol cars. Most petrol cars aren’t filled every day, and there’s no reason that most EVs will be either. The grid doesn’t have to be able to cope with this eventuality, and this is demonstrated by the evident fact that the petrol network also cannot cope with this eventuality.

Posted by simon in The wider world