They discuss how Repowering can drive decarbonisation of coal assets and explore how the RepowerScore tool can be used to assess the suitability of repowering the existing global coal infrastructure.

Please explain the ‘Repowering’ pathway

Dr. Daniel Cox: When we're talking about decarbonising the energy system, the strategy has always been about turning off the coal and then building something else, whether that's wind, solar, any renewables. This strategy ignores the elephant in the room, which is all the assets that we already have.

There are so many existing coal assets in the world. Of the ~10,000 or so coal-powered units, over 6000 of them are still operating. A good chunk of them are less than 10 years old. This is valuable infrastructure that has been the backbone of many economies. It provides so much good stuff - heat, power, employment. It provides so much to the regions where it is used.

The ‘Repowering’ concept is: how can we keep all that good stuff, but get rid of the emissions, the CO₂, which is the most pressing thing for the climate crisis. The idea is that we reuse as much of that infrastructure as possible by taking out the coal and putting a different technology in.

What technology could replace coal?

Dr. Daniel Cox: In some areas, nuclear small modular reactors (SMRs) will make sense. In some other areas, advanced geothermal drilling will be an option. Some lucky areas will be able to have concentrated solar power. In southern Spain or northern Africa, where you have sun for most of the year, concentrated solar power is a very good option.

In other places it might not be so clear cut. You might have to do a mixture of multiple options, and if you want to do it as quickly as possible, you will have to use the technologies that are available now. Building solar panels and doing test drills for geothermal are possible in the next few years. When you move out to 5-10 years away, a lot more of the SMR designs will be validated. They will have had their ‘First of a Kind’ (FOAK). Then people will be less risk averse, and that will become an option. Then eventually you can just replace all the coal boilers with clean technology.

To be honest, the choice of technology doesn't matter, as long as it's clean. The majority of electricity generation has been: you make water hot, you boil it, you have steam. Steam spins a turbine. Turbine produces electricity. It doesn't matter where that heat came from. It doesn't matter how you started. It doesn't have to be coal, it doesn't have to be gas, doesn't have to be nuclear, it doesn't have to be geothermal, but it's some source of heat that then gets turned into electricity.

Of course, when you're doing wind, you skip the heat part, you just have the spinning that gets converted into electricity, and when you're doing concentrated solar, it's a bit more complicated then, but it is heat to electricity still.

Why is coal repowering a good idea?

Dr. Joseph McKenna: It’s cool. It’s vital. It's a use of existing assets that's not really been considered. There's not been a significant number of coal power stations that have been transformed to something else. We can help empower investors, policy makers to pick and choose which power stations are best, which are most suitable.

A coal power station is going to shut at some point, but if you can repower, if you can replace components, reuse, you can keep the community around it. You can keep local communities vibrant and keep your cheap electricity.

Dr. Sebastian Svanström: Also, if you're an environmentalist, there's a lot of environmental benefits with the Repowering pathway, because there's no new site with a new grid. You don't need to cut down trees, flatten everything, and do all the groundworks, as it is using sites that are already available.

I think that's a really big point that is not emphasised enough, that with repowering, you're not clearing forests or land – it’s possible to prevent extra environmental destruction, and you can get a new power that is carbon-free much faster. Everything is ready, or at least the foundation. We often focus on climate change, but there are also all the other impacts on the environment of building completely new sites for energy production, and those, I think, are not really appreciated.

How did RepowerScore begin?

Dr. Daniel Cox: The first work was done by Staffan Qvist (the founder of Repower Initiative), Łukasz Bartela and Paweł Gładysz. They went on to then form the DEsire project in partnership with the Repower Initiative, looking at how to best repower coal plants with nuclear. They looked at how it could be done. Then they focused in on a plant, and then they expanded the scope and looked at the whole of Poland. They looked at what plants could be suitable, looked at how they could be suitable, what factors would affect the suitability, and this work has gone on to then produce case studies and investigations that are now directly informing the Polish energy policy.

After they'd worked out how to rank these plants for nuclear, it was such a good idea, Staffan Qvist suggested: ‘Why don't we do this for all the plants?’

It sounds so simple, and it is conceptually, but it has taken quite some time to put RepowerScore together.

Tell us more about how RepowerScore works?

Dr. Joseph McKenna: RepowerScore is a tool to look at all coal power stations in the world and compare their suitability for being repowered.

Dr. Daniel Cox: We've taken all of the coal fired units in the world, all ~10,000 of them, and we've ranked each one of those on ~30 different factors, ranging from the seismic activity in the region and how that makes it more or less suitable, the direct normal irradiance for concentrated solar power, the proximity to airports, the amount of people nearby, so many different factors, and we're constantly adding more of these.

Dr. Joseph McKenna: Is it old enough? Has it just been installed? Do we not want to repower it because it's got a lifespan that the investors are going to want to see paid off? Is the geology suitable for geothermal? Is geology suitable for a nuclear power station?

Dr. Daniel Cox: Once we rank them on these factors independently, we consider what factors are important for repowering with, e.g., geothermal or with nuclear? If we're repowering with nuclear, obviously we don't want to build too close to a population centre. We don't want to build right next to an airport. We don't want seismic activity. Then you build up these different factors, and then they are assigned different levels of importance depending on what pathway you're doing. You just crank the handle at that point, and a score comes out between 0 and 100. So far with RepowerScore, it's all been about the technical feasibility, so if a plant scores 100 there is absolutely no reason that it couldn't be repowered technically, on the pathway that we are looking at.

Dr. Joseph McKenna: Nuclear has a mixed amount of popularity around the world, and we need to plug in whatever would fit in which place best.

Dr. Sebastian Svanström: Right now, we're looking at, for example, concentrated solar power, where you're looking at how much direct, nice sunlight there is available - the areas where it casts a shadow. Do you have cooling? We're trying to score the site. Is this a good place to use concentrated solar power to replace the coal?

Dr. Joseph McKenna: All the data we have is open. The website is available to be played with. It's a fun toy. You can go poke around, see which power stations in which country are suitable.

What have you discovered from the data?

Dr. Daniel Cox: We recently reworked the advanced geothermal pathway. Of course, the places where it is best to use geothermal are all the countries that lie on the ‘Ring of Fire’ (a horseshoe-shaped zone of intense volcanic and seismic activity surrounding the Pacific Ocean). This is where the Earth’s crust is as thin as it is anywhere. There you've got the most heat that is closest to the surface, and it's striking how clearly this ring comes out.

 Looking at concentrated solar power, it's very clear that South Africa, the western side of the US, North Africa, South Europe, just light up.

I think one of the things that was interesting for me, which probably shows some of my naivety, is how unsuitable a lot of places in Southeast Asia are for solar or for wind. Indonesia, for example, is not windy at all, which is completely different from me coming from the UK. These largescale insights pop out, and that's the advantage of doing it for everywhere at once. You can quickly see trends like this.

Which technology is the most viable for Repowering?

Dr. Sebastian Svanström: All of them. Because if you look at the different sites, for example, if you're on a fault line, in Japan, Indonesia, where you have a lot of earthquakes, and these kind of disasters, you might not want to build nuclear power plants, but these places also have good geothermal resources, so that becomes an alternative option. Then if you look at other places where it's very dry, you might not have a lot of water available for cooling, but then you might be able to use CSP to do the repowering. If you look at these maps, usually where one thing scores poorly, the other thing scores great. So they complement each other.

‍

‍

How should multiple technologies be combined on a single site?

Dr. Sebastian Svanström: It depends on the site, if you have a lot of land available, you could bring in solar and use it as a renewable interconnection point. If you're on the coast, it could be offshore wind, for example, if it's a good wind resource. So it depends. You have to look first at what is the site, what are the resources available. It might turn out that there's three technologies that are good, and then you would probably bring in a combination of those if they complement each other.

How will RepowerScore develop next?

Dr. Daniel Cox: The factors will continue to expand. We are slowly working on adding policy and seeing how policy affects the repowering viability. If a coal unit is in a country where it's not legal to build nuclear reactors, then the score on the nuclear pathway would drop to zero. If this country has particular policy incentives for repowering with clean sources, such as geothermal, then that would make the score higher, because repowering is much more likely to work out if you have the government backing on this.

Dr. Joseph McKenna: We're fortunate enough not to be tied to any vendor, not tied to any technology. We will be adding more pathways, more different solutions. We're extending the analysis for solar facilities. Geothermal is a new technology to us, but being able to do a case study on a global scale for geothermal is super cool. That should help with maybe even solving district heating. District heating is a great use of waste heat. If you have a power station near a population, you've got a free heat source. Just pump it around the city. Kraków has a great district heating system.

Dr. Daniel Cox: We're also now looking at expanding into the economic side of things, looking at actually, how old is the plant, how much is this asset worth, how much of this could be recovered, and going in from that side to try and find the ones that are a good idea to do further work on.

The idea of RepowerScore is, we're doing all of this work on a very shallow level, but for everywhere, and that can be the pre-assessment for doing case studies. If you can say, what are the most suitable plants in this country or owned by this operator, and then you dig in on them, and do a proper case study and really investigate it, it just it saves you time and gives you a good starting point.

What’s next for the Repower movement?

Dr. Daniel Cox: The first few summits we held were almost entirely academic. We've now got vendors, Transmission System Operators, we've got so many more of the important people that need to be in the conversation hat are starting to turn up, and so the conversations get much more interesting at this point.

People are hearing about the idea and are spreading it, and more and more people are getting involved. Because it does make sense. It’s a sensible, pragmatic solution that should really be part of what we are doing. We need a concerted effort that covers countries, regions and vaster areas of the world. If big decisions were made on doing something, then the speed could be a lot quicker.

Dr. Joseph McKenna: One of the major challenges is convincing investors and banks that the repowering is a safe investment of money. We need to get a repowering project beginning to end completed so that it's so transparent that this pathway is an affordable, sensible, profitable transition to make.

RepowerScore is freely available to explore online.

We invite you to try it for yourselves!

RepowerScore is an assessment tool inactive development.

It expresses the suitability of Repowering a coal-fired power plant with clean energy sources, such as next-generation geothermal, advanced nuclear or concentrated solar power.

Coal units are scored on an expanding set of technical and geographical factors. Data is largely taken from the “Global Coal Plant Tracker, Global Energy Monitor, January 2025 release”.

‍