Submitted by Bruno Prior on Thu, 17/12/2020 - 11:26

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   This is our estimate of the impact of this scenario on the carbon emissions from the combustion of fuel for the generation of electricity. It is less than many people might imagine would be the effect of 40 GW of offshore wind, 13 GW of onshore wind and 18 GW of solar, for a number of reasons, including two in particular:
   1. British electricity has already been decarbonised more than many people realise. Not so long ago, the grid-average carbon intensity of electricity was roughly 2.5X the carbon intensity of gas, per unit of final energy. Now, they are roughly on a par. There are diminishing marginal returns from further decarbonisation, as new low-carbon capacity increasingly competes with existing low-carbon capacity as well as the modest residual fossil-fuelled output.
   2. The total amount of electricity generated has increased significantly under this partial-electrification scenario. So the 27% reduction in the absolute amount of carbon emitted from this source reflects a larger reduction in the carbon emissions per unit of final energy. This will be partly reflected in the carbon emissions from other sectors below, which show the opposite effect.
   3. This chart does not include the embodied carbon in the generation facilities. It indicates only the carbon emitted in the process of generating the electricity. We do not attempt to carry out a Lifecycle Assessment in this model. But we do estimate the embodied carbon in new infrastructure separately below.
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   To avoid double-counting the carbon emissions from the electricity used to power electric heat and transport, for these uses, we calculate only the carbon emissions from the non-electric systems. This chart shows that calculation for heat.
   1. The total carbon emissions from heat will have fallen less, because a significant proportion of the fall relates to the exclusion of electricity, which is a larger proportion in the Proposed column than the Base column.
   2. But there would still be a material reduction because:
      1. the carbon intensity of electricity would have fallen below the carbon intensity of gas (and other combustion fuels) in this scenario, and 
      2.  this scenario assumes most of the electric heating is heat pumps (compared to a minimal proportion at present), which significantly reduces the amount of electricity required to deliver a given amount of heat. 
   3. The scenario also assumes that some efficiency improvements have reduced the total demand for heat, and consequently the carbon emissions from heat-production.
   4. Still, this illustrates the scale of the challenge to decarbonise the sector. There is a long way to go. We chose only one-third electrification as the starting point because of the system challenges of incorporating more (as we will examine in sensitivity analysis below).
   5. As for electricity, these figures reflect only the emissions from fuel combustion, and do not include the embodied carbon in the infrastructure. Unlike electricity, the model does not yet attempt to estimate the embodied carbon in our heating systems, and the impact of the scenario on that embodied carbon.
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   This is the impact of this scenario on carbon emissions from the combustion of transport fuel, excluding electricity. Not surprisingly, displacing half the internal combustion engines with electric vehicles has roughly halved the carbon emissions from road transport.
   1. The scenario also assumes further (but not complete) electrification of the rail network, whose carbon footprint consequently falls. But this illustrates the relative insignificance of this mode of transport.
   2. The scenario does not assume any electrification of air or water transport, and consequently does not project any significant reduction in their carbon footprint. No doubt efforts will continue to develop lower-carbon options for these modes of transport, but these options are too immature to assume anything in a base scenario. The chart illustrates the significance of air travel. Besides the technical difficulty of decarbonising air transport, it is an added problem that air is primarily about international travel, which muddies the waters both in terms of action and in terms of accounting.
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   Combining these uses, gives us the following picture of carbon emissions from the combustion of fuel. Again, this does not include carbon embodied in the infrastructure. It does not include carbon dioxide from non-energy sources. And it does not include other greenhouse gases, other than the small quantities included in the figures for the carbon intensity of energy technologies, expressed as carbon-dioxide-equivalent.
   1. In sum, the scenario reduces direct carbon emissions from the energy sector by just under one-third, relative to the position around 2017, which was already materially reduced from the turn of the century. But there is a long way to go still.
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   This is our estimate of the carbon embodied in the infastructure required to deliver this scenario in the electricity sector. It does not include the carbon embodied in the existing infrastructure (hence the non-existent Base bar).
   1. The main point to note is that this is relatively modest. It reflects the sum of all embodied emissions in the infrastructure developed to deliver this scenario, over whatever period one might assume (we have 2030 in mind for this scenario, but it is not specific). The previous charts are per annum. So the annual emissions from fuel consumption are significantly larger according to our model than the one-time emissions from constructing the infrastructure. 
   2. Nevertheless, one should take account of the net effect of all emissions in calculating the true impact of the scenario. That would marginally reduce the carbon benefit indicated in the previous charts.