Another Monday Message Board. Post comments on any topic. Civil discussion and no coarse language please. Side discussions and idees fixes to the sandpits, please.
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John Quiggin 
Ember on solar
There is a new team of transition pundits at NGO Ember (note the name Kingsmill Bond) who are so upbeat that they make yours truly look like Eeyore. Their latest offering is a gung-ho report on solar energy and batteries, with nice charts and maps: https://www.electrotech-revolution.com/p/harnessing-the-sun-the-solar-battery
One interesting choice they made is to ignore wind entirely. From a global perspective, this has the virtue of simplifying the message. For the majority of the world’s population it’s fair enough: solar and batteries are necessary and sufficient. The two technologies are far from equal. Wind, at 167 GW installed in 2025, is very much the junior partner to solar’s 647 GW: That still holds even when allowing for a 2x higher capacity factor, which takes the effective ratio to 2:1. The flatter learning curve, and the greater cost of firming from a longer cycle of natural variation, will steadily widen the gap. However wind will stay important in several high-latitude and high consumption countries, including the UK, Ireland, Germany, the Nordics, Poland, Korea and Japan. It also has the handy feature of weather complementarity with solar, keeping power going on “dark and stormy nights”. The total cost of a combined system will be lower.
Ember rightly pay attention to the cost of hitting 100% of net zero, and – correctly in my view – they advise against fetishising the last few percent:
“Costs rise sharply at the very end. Moving from 95% to 99% uptime might add around $15/MWh, or roughly 20%, and in harder regions $30/MWh or more. Moving from 99% to 100% can cost more than three or four times as much again. A real power system does not need to solve those final hours with solar and batteries alone. Once they provide 90–95% of annual supply, the remaining hours can be covered by a low-cost firming resource: a gas turbine, diesel generator, hydro, interconnection, demand response, or another dispatchable technology.”
The first two on this list are CO2-emitting. Diesel is expensive as well, though it’s portable and scaleable. Backup gas will be cheap, because the turbines and ancillary equipment have already been built and paid for. There are now presumably second-hand ones available from California, which has already shuttered 2 GW of them as surplus to requirements.
How much of an emissions problem will gas backup be? We can make an informed guess from current global GHG emissions, which they give as 53.2 Gt CO2eq in 2024 (without land use, land use change and forestry). 95% of this at net zero would leave 2.67 Gt a yrar of industrial emissions uncompensated. Of course the actual volume will be affected by a host of factors pushing in both directions, but the order of magnitude looks reasonable. Going for 98% cuts the number to 1.06 Gt.
This is where Ember leave out something important: my hobby-horse of carbon reduction. In 2022 I came up with a ballpark estimate of ≈250 Gt cumulative GHG overshoot at the net zero date, usually given as 2050. This is what will have to be removed to get back to the safe pre-industrial concentration of 350 ppm or so. I would welcome a professional estimate, but can’t find one, so we will go with mine. Sometime before net zero the world will have to decide how quickly to roll out the advanced, simple, cheap and scaleable CDR technology we don’t actually have yet. Arbitrarily picking a 50 year target, our modest CDR overshoot programme will have to bury 5 Gt a year, every year from then on. Compensating a 2% maximum burn from gas backup will take this to 6.1 Gt.
We can’t be sure today that 5 Gt a year will be feasible; but if it is, so is 6 Gt. Cheating in this way over the last few percent could be efficient and ethically defensible.
The differences in uncompensated energy emissions between 0% 1%, 2% and 5% are significant and need to be investigated. But they are not an urgent problem. On current schedules, we can wait a decade before deciding on the best value for money, using better information about feasibility and cost. It’s not an ethical dilemma.
Morals:
1. Get better scenarios for the last mile to net zero, with and without gas backup and CDR.
2. Spend whatever it takes on R&D to have tested gigascale CDR technology ready well before net zero day. €1 bn a year would be under 0.1% of current investment in cleantech, unnoticeable. I’m not very worried about political support for this: the peoples of the world will be screaming in vain for quick relief from intolerable climate extremes, when they are not chasing scapegoats for public executions.
3. Start now. 24 years is not a long time for a difficult technology shift on this scale. Besides, there will be enormous popular pressure to bring the net zero date forward, and technical progress will keep lowering the outlay cost of doing so. The opportunity cost against BAU is already well below zero.
My bête noire or perhaps phobia is lithium batteries. We need a Ralph Nader approach to lithium batteries: “Unsafe at any capacity, in any application.” LiFePO4 batteries are perhaps a little better.
We need the next generation of batteries now IMHO. I suppose the possible starters for various application are:
Sodium-Ion – Cheap, abundant materials, high thermal stability.
Semi-Solid – Solid-State – V. high energy density, non-flammable solid electrolyte.
Aluminium Ion – Ultra-fast charging, Sustainable, no risk of short-circuit fires.
Redox Flow – Infinite scaling, long life. Entirely non-combustible.
I started getting a few lithium battery powered gardening tools several years ago, and a lithium battery powered push mower for the one small grass area on my rough bush block. The rest I slash with an ICE mower (where there are not thickets of trees).
However, I stopped buying Lithium technology and I will NOT put a large Lithium wall-battery in my garage or on my house. I don’t trust them. The current rushed and over-subsidised rollout of these in Australia could yet end in tears (with house fires rising I predict).
We need to move fast for sure. We also need to avoid rushing in stuff that is not ultimately safe enough. Lithium batteries fall into that category.
The carbon removal technology we have now is trees
Iko, what about goats? I am told that they will eat practically anything. There are a few places here that offer goat brush clearance. It has not made it to the consumer level yet though, where I am.
Yes to carbon capture!!
N,
Goats would strip leaves and bark off too many small trees and saplings that I want to keep. Goats are browsers not grazers for the most part. Sheep are better for grass. Also, my property is only properly fenced on two sides. Putting up a couple of hundred meters of temporary fencing for the graze would be far too costly. Then there’s the (mostly) native gardens they would tear apart. Not an option, I am afraid.