Time to make 2025 updates to my annual “opinions about solar” thread.
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22. Examples of real long-duration storage technologies are pumped hydro (reservoir size is decoupled from turbine capacity), or where the storage medium is big tanks of molten salt, or hot rocks. But all of these do still cost a lot of money if they are only cycling once per year.
23. Lithium-ion will probably continue to be the dominant battery technology. High prices for lithium in 2022-2023 drove interest in sodium-ion, and there are still products coming out, but new lithium production capacity has brought prices back down and so the impetus to switch has been reduced.
(The cure for high prices was, it turned out, high prices.)
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23. Lithium-ion will probably continue to be the dominant battery technology. High prices for lithium in 2022-2023 drove interest in sodium-ion, and there are still products coming out, but new lithium production capacity has brought prices back down and so the impetus to switch has been reduced.
(The cure for high prices was, it turned out, high prices.)
24. We oughtta be building more wind generation capacity. Seriously, solar will get built anyway, but wind needs some help, and wind blows in the dark and in the winter. It doesn’t help that solar pushes down power prices and generates renewable energy credits (where relevant), which hurts wind farm economics.
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24. We oughtta be building more wind generation capacity. Seriously, solar will get built anyway, but wind needs some help, and wind blows in the dark and in the winter. It doesn’t help that solar pushes down power prices and generates renewable energy credits (where relevant), which hurts wind farm economics.
25. To put it another way: when you tell an energy future model to optimise a power portfolio for clean power adequacy, it will give you more wind and less solar than when you tell it to optimise a least-cost electricity sector development.
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25. To put it another way: when you tell an energy future model to optimise a power portfolio for clean power adequacy, it will give you more wind and less solar than when you tell it to optimise a least-cost electricity sector development.
26. BNEF’s New Energy Outlook modelling doesn’t want to just solve the intermittency problem with loads of batteries. This is because the batteries get lower utilization rates the more you build. Batteries cannibalize batteries long before you get 100% clean power.
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26. BNEF’s New Energy Outlook modelling doesn’t want to just solve the intermittency problem with loads of batteries. This is because the batteries get lower utilization rates the more you build. Batteries cannibalize batteries long before you get 100% clean power.
27. Hydrogen made with renewable electricity will be used for steel and fertiliser manufacture. Some may be used to make shipping and aviation fuel. Some may even be burned for power in weeks of low renewables, which is one way to shift energy from summer to winter.
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27. Hydrogen made with renewable electricity will be used for steel and fertiliser manufacture. Some may be used to make shipping and aviation fuel. Some may even be burned for power in weeks of low renewables, which is one way to shift energy from summer to winter.
28. ...but sometimes net-zero electricity models want to put in hydrogen to cover weeks of low renewables just because the model isn’t given any other option. Deep decarbonization models do weird things. It may turn out there are easier pathways in practice.
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28. ...but sometimes net-zero electricity models want to put in hydrogen to cover weeks of low renewables just because the model isn’t given any other option. Deep decarbonization models do weird things. It may turn out there are easier pathways in practice.
29. Electrification of transport is far better than biofuels; solar plants can run an electric car on a small fraction of the land used to grow fuel to run a biofuel car.
30. Decarbonizing aviation is hard. The CEO of Lufthansa said in 2023 that running its fleet on sustainable aviation fuel made from electricity would take half Germany’s current electricity demand. BNEF thinks this an underestimate.
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29. Electrification of transport is far better than biofuels; solar plants can run an electric car on a small fraction of the land used to grow fuel to run a biofuel car.
30. Decarbonizing aviation is hard. The CEO of Lufthansa said in 2023 that running its fleet on sustainable aviation fuel made from electricity would take half Germany’s current electricity demand. BNEF thinks this an underestimate.
31. Direct electrification of aviation would be better. BNEF research did track orders for 989 electric aircraft (mostly small ones) as of early 2022, but this is a long term project. Fingers crossed. (www.bnef.com/insights/30267 ).
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31. Direct electrification of aviation would be better. BNEF research did track orders for 989 electric aircraft (mostly small ones) as of early 2022, but this is a long term project. Fingers crossed. (www.bnef.com/insights/30267 ).
32. Heatpumps are better for heating homes than hydrogen, but in seasonal climates like northern Europe will exacerbate the seasonal demand and supply mismatch for solar. We need to build wind and probably nuclear as well.
33. How mismatched is European seasonal solar supply and electricity demand? Well, here is the situation for my fully electrified house in Switzerland with 13.2kW of solar, a heatpump and an EV. I would have needed about 122kW of PV to be self-sufficient across December.
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32. Heatpumps are better for heating homes than hydrogen, but in seasonal climates like northern Europe will exacerbate the seasonal demand and supply mismatch for solar. We need to build wind and probably nuclear as well.
33. How mismatched is European seasonal solar supply and electricity demand? Well, here is the situation for my fully electrified house in Switzerland with 13.2kW of solar, a heatpump and an EV. I would have needed about 122kW of PV to be self-sufficient across December.
34. Europeans shouldn't feel guilty about using electricity for airconditioning, it'll all come from the sun anyway by 2030. Solar generation times and seasons match airconditioning demand pretty well, which is good news for really hot countries.
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34. Europeans shouldn't feel guilty about using electricity for airconditioning, it'll all come from the sun anyway by 2030. Solar generation times and seasons match airconditioning demand pretty well, which is good news for really hot countries.
35. Nuclear is safer than coal and climate change, and better than gas unless the gas plants are running very rarely. Batteries should help with the unfavourable ramping economics of nuclear (you *can* turn nuclear plants up and down, but you really don’t want to).
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35. Nuclear is safer than coal and climate change, and better than gas unless the gas plants are running very rarely. Batteries should help with the unfavourable ramping economics of nuclear (you *can* turn nuclear plants up and down, but you really don’t want to).
36. We’re finally getting serious about net zero carbon. Getting that last 5-20% of carbon out of power will be hard, and require some expensive solutions. The first 80-95% is easy-ish but we're getting on with it.
37. You can be cynical about government and corporate net zero emissions targets if you like, but they're a lot better than no net zero emissions targets.
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36. We’re finally getting serious about net zero carbon. Getting that last 5-20% of carbon out of power will be hard, and require some expensive solutions. The first 80-95% is easy-ish but we're getting on with it.
37. You can be cynical about government and corporate net zero emissions targets if you like, but they're a lot better than no net zero emissions targets.
38. Ordinary people have no idea how much progress we’ve made. Tell people at parties that UK carbon emissions in 2023 were at their lowest level since 1879, for example. Most developed economies are now reducing carbon emissions without lowering quality of life.
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38. Ordinary people have no idea how much progress we’ve made. Tell people at parties that UK carbon emissions in 2023 were at their lowest level since 1879, for example. Most developed economies are now reducing carbon emissions without lowering quality of life.
39. …It would still really help if rich people would stop pissing carbon into the atmosphere for no reason.
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39. …It would still really help if rich people would stop pissing carbon into the atmosphere for no reason.
40. There are signs that solar is reducing fossil fuel burn in poorer countries, for example Pakistan — which has no significant government support for solar but has built over 25GW just in response to high prices for power and fuel for irrigation.
41. This has interesting and not uniformly positive side effects. Pakistan may be the first market to see a true 'utility death spiral' where customers who can go solar do so, leaving other customers to pay for the grid, raising power prices..
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40. There are signs that solar is reducing fossil fuel burn in poorer countries, for example Pakistan — which has no significant government support for solar but has built over 25GW just in response to high prices for power and fuel for irrigation.
41. This has interesting and not uniformly positive side effects. Pakistan may be the first market to see a true 'utility death spiral' where customers who can go solar do so, leaving other customers to pay for the grid, raising power prices..
42. Annual build volumes of solar are rising, but they are not guaranteed to rise forever. This is a symptom of solar starting to actually make a dent in power demand, with negative feedback effects such as power price cannibalization.
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42. Annual build volumes of solar are rising, but they are not guaranteed to rise forever. This is a symptom of solar starting to actually make a dent in power demand, with negative feedback effects such as power price cannibalization.
43. Data centers are increasing power demand, but let's keep a sense of proportion. BNEF estimates total electricity demand from data centers of 373TWh in 2024 (1.2% of global generation) and expects this to increase to 1,596TWh (4.4% of global) in 2035.
This is a source of some disappointment to renewable energy project developers.
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43. Data centers are increasing power demand, but let's keep a sense of proportion. BNEF estimates total electricity demand from data centers of 373TWh in 2024 (1.2% of global generation) and expects this to increase to 1,596TWh (4.4% of global) in 2035.
This is a source of some disappointment to renewable energy project developers.
44. Demand for solar panels to sub-Saharan Africa is also strong, measured by Chinese exports, though the total was still less than 13GW in 2024 (it's hard to sell to poor people). Nigeria, Ethiopia, Congo, Kenya, Senegal and Zambia are the largest African markets in 2025 to date.
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44. Demand for solar panels to sub-Saharan Africa is also strong, measured by Chinese exports, though the total was still less than 13GW in 2024 (it's hard to sell to poor people). Nigeria, Ethiopia, Congo, Kenya, Senegal and Zambia are the largest African markets in 2025 to date.
45. Some governments are definitely out to fight against a better future.
46. Achieving a net-zero energy transition, for most countries, will not look like winning a war or marching into a capital waving flags. It will be the ability to say "no thank you, we do not want what you are selling" to the petrostates, and walking (or cycling, or taking an electric bus, or driving an EV) away.
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45. Some governments are definitely out to fight against a better future.
46. Achieving a net-zero energy transition, for most countries, will not look like winning a war or marching into a capital waving flags. It will be the ability to say "no thank you, we do not want what you are selling" to the petrostates, and walking (or cycling, or taking an electric bus, or driving an EV) away.
47. While moving to a circular economy with 100% recycling rates is essential in the long run, it’s not a challenge for PV in particular; few PV panels have been recycled to date only because the vast majority are still in use. It can be, and is, done.
Volumes are still tiny compared with most things we also have to recycle.
