Trystan Lea

What might a Zero Carbon Britain look like?

Published: 7th September, 2022

Early draft, work still in progress

The following pages try to explore zero carbon scenarios at different scales. Starting with Britain as a whole and then zooming in to Wales, Gwynedd and ending with Llanberis. I have tried to keep the following as focused on the numbers as possible, minimising my own interpretation. I might come back to add that in later or add it as a seperate piece.


A breif outline of the scenario
The ZeroCarbonBritain scenario is a 100% Renewable energy scenario for the UK. In material terms it describes a modern way of living that is not that different to how we live today. It is more ambitious than many scenarios on reducing demand, building energy use is reduced by 67% through state of the art insulation and air-tightness techniques, efficient appliances, led lighting and the electrification of heat with heat pumps. Transport energy is reduced 76% through a combination of electrification, modal shifts and a particularly ambitious reduction in aviation. On the supply side, offshore wind provides the largest portion of energy supply.

Number of households: 29.0 million (2030).

Demand Summary

Current ZCB
Lighting, Appliances and Cooking 199 TWh/yr 112 TWh/yr (More efficient appliances)
Space and Water heat, fuel demand 536 TWh/yr 129 TWh/yr (Retrofit & heat pumps*)
Transport demand 661 TWh/yr 157 TWh/yr (Electrification & modal shifts)
Industry demand 229 TWh/yr 288 TWh/yr (Onshoring and economic growth)
Key progress metrics
% of heating electrified with heat pumps ? 90%
% of transport electrified ? 90%

*Heat pumps move 136 TWh/yr of heat from outside air into buildings. Total delivered heat is 129 TWh/yr + 136 TWh/yr = 265 TWh/yr.

Supply Summary

Latest offshore and onshore wind capacities from:

Latest solar capacity sum of 13,800 MW end of 2021 + 556 MW first 6 months of 2022.

Many of the other figures are based on data from 2018 national statistics.

Current ZCB Progress
Offshore Wind 12.7 GW (42.8 TWh/yr) 140 GW (529.7 TWh/yr) 9% (8.1%)
Onshore Wind 14.2 GW (32.2 TWh/yr) 30 GW (76.5 TWh/yr) 47% (43%)
Solar PV 14.3 GW (13.8 TWh/yr) 90 GW (74.4 TWh/yr) 16% (18.5%)
Tidal 2 MW (3.25 GWh) 20 GW (42 TWh/yr) 0.01%
Wave ? 10 GW (25 TWh/yr) ?
Solar Thermal 1 GW (0.8 TWh/yr) 30 GW (25 TWh/yr) 3%
Geo Thermal Electricity ? 3 GW (24 TWh/yr) ?
Geo Thermal Heat ? 2 GW (16 TWh/yr) ?
Hydro 1.9 GW (5.5 TWh/yr) 3 GW (8 TWh/yr) 63% (69%)
Biomass for biogas ? 89 TWh *
Biomass for liquid fuels ? 109 TWh
Biomass for direct heat 165.2 TWh 38 TWh
Storage, synth fuels and backup
High efficiency electricity storage ? 200 GWh
Electrolysis ? 27 GW
Hydrogen storage ? 20,000 GWh
Methanation capacity ? 5 GW
Methanation storage ? 65,000 GWh
Synth liquid fuel capacity ? 9 GW
Backup gas turbine capacity ? 61 GW (16 TWh/yr)

100% Renewable UK IAS Scenario

The 100% Renewable UK Inter Annual Storage (IAS) Scenario is an interesting scenario to compare against the ZeroCarbonBritain scenario. It has many similarities in terms of both the 100% renewable goal and a very high percentage of demand electrification but does not include the more ambitious demand reduction measures included in ZeroCarbonBritain.

Electricity supply mix (Appendix Table 38):

100% RE IAS Progress (Energy)
Offshore Wind 130 GW* (180 GW*), 681.0 TWh/yr, CF:60%* 6.3%
Onshore Wind 42 GW* (75 GW*), 191.9 TWh/yr, CF:52%* 16.8%
Solar PV 310 GW* (356 GW*), 294.0 TWh/yr, CF:11%* 4.7%
Wave 127.5 TWh/yr 0%
Hydro 5.1 TWh/yr 108%
Biomass Waste 1.0 TWh/yr
Other RE 43.3 TWh/yr
Total 1343.8 TWh/yr

* Capacities calculated based on Table 20 and 21 of report.

Different capacity factor assumptions

At first appearences it looks like the 100% RE UK IAS scenario requires less offshore wind capacity than ZeroCarbonBritain. This is due to a high capacity factor assumption of 60% vs 43%. At a 43% capacity factor the 100% RE scenario would need 181 GW of offshore wind, an additional 40 GW above the ZCB scenario. The average capacity factor of present day offshore wind farms is 38.5%, it is expected that this will improve as larger wind farms in locations with better wind resources are built alongside technology improvements such as larger turbines.

Higher capacity factors are projected for onshore wind and solar PV as well.