A lot of countries (as well as many U.S. states and utilities) are announcing so-called zero-carbon plans, typically with a target year around 2050. These are often reported as calling for 100% renewable energy, which is wrong.

There is a difference between zero-carbon and 100% renewables, but this is often hidden and unclear. In the new UK plan it is still hidden, but once found it is very clear. Renewables provide just 57% of the energy, which is a lot less than 100%. Perhaps most surprising is that nuclear might provide as much as 38% of the energy!

By way of introduction, the plan comes from the government’s own Committee on Climate Change ( CCC ), in a report titled “Net-Zero: The UK’s contribution to stopping global warming.” The CCC is the UK’s top climate action planning group.

The surprising numbers occur in an obscure Technical Annex, titled “Integrating variable renewables into the UK electricity system.” As the title suggests, the UK CCC is well aware of the severe limitations that intermittency creates for renewables.

These limitations are succinctly summarized right up front, in the second paragraph of this 17 page Annex. Here is what the CCC says:

“Variable (or ‘intermittent’) renewables – which are weather dependent – are different to other forms of electricity generation, and increased deployment of them could require additional system services. For example, renewables cannot be guaranteed to generate during winter peak demand periods, and renewable output is generally correlated across different sites. Similarly, wind and solar generation can change substantially over periods of just a few hours, requiring non-renewable plants to be held in reserve to meet any sudden shortfall in supply.”

The CCC therefore proposed a mix of zero emission power generating technologies, as follows:

“Our Further Ambition scenario for the power sector sees low-carbon sources providing 100% of power generation in 2050, through a mixture of variable renewables (57%), firm low-carbon power like nuclear or plants fitted with carbon capture and storage (38%) and decarbonised gas such as hydrogen (5%).”

Renewables provide just 57%. A whopping 38% comes from some combination of nuclear and fossil fuel plants fitted with carbon capture and storage (CCS), or perhaps from some unknown new technology. Another 5% comes from decarbonised gas, making fossil fuel use at least 43%.

Of these alternatives, nuclear power is the only proven technology, so it is the only sure bet.

There has been a lot of research on CCS but it may never be feasible. Existing CCS technologies require a major fraction of the power plant’s energy output, making them very expensive. Plus all this extra needed energy would jack fossil fuel use way up.

There is also the huge unresolved environmental issue of safely sticking billions of tons of CO2 down into the ground. Perhaps worst of all, it would violate the Green goal of eliminating fossil fuel use, especially if the full 43% of UK power comes from that hated stuff.

Or they could burn wood and the Annex even suggests this, except they call it “bioenergy,” so maybe it includes Indonesian palm oil. What an environmental disaster that would be! If CCS can be made to work, why not burn readily available coal, oil and gas? In fact Big Oil & Gas are spending nearly a billion dollars on CCS research.

So this plan seems to give the greens a very nasty multiple choice, between nuclear power and continued fossil fuel use and destructive bioenergy. It is hard to say which they like least.

But the CCS zero-carbon is clear, accurate and honest, which is very rare in this policy zone. It should be a lesson for every country, as well as for every U.S. state and utility. 100% renewables will not work, so you have to find a very different way to get to zero carbon emissions. Also, let’s all try being honest about it for a change.

The CCC makes it very clear that zero-carbon will be very difficult. But then, zero-carbon is an insane goal, so it should be hard to get to.