NEW BUILD | UK
All change for UK to meet net-zero
How must the UK energy system adapt to achieve net zero carbon emissions by 2050? Tony Roulstone examines some scenarios
THE 2050 UK ENERGY SYSTEM will be completely different from today because of the commitment to net-zero carbon emissions. The dominant means of providing space heating and electricity –– natural gas — will be a thing of the past. The size of the UK electricity system is likely to double to more than 600TWh even with greater energy efficiencies. Electricity will replace fossil fuels for transport, space heating and many industrial needs, including producing ‘green hydrogen’. Zero-carbon electricity is forecast to be dominant by
University of Cambridge Tony Roulstone
2035. By then renewables will be providing more than 60% of supply, mostly in the form of wind and solar. The UK has good offshore wind resources to be balanced by a smaller amount of seasonal solar supply. These dramatic changes seem to provide an opportunity
for other zero-carbon forms of energy, including bio-energy and gas (both requiring carbon capture) and nuclear. How will these systems work together to keep the lights on and to minimise energy costs?
Renewable energy systems As the share of renewable energy increases, the variability of renewable supply will be felt across the whole system. Wind and solar output is completely dependent on the weather. A completely renewable UK supply for 2050 would be generating 600TWh pa to meet an expected demand that is double that of today. But it would have an ‘energy gap’ equal to 20% of annual demand, due to the miss-timing of renewable supply versus demand. When demand is higher than renewable supply, because
there is either little wind or no sun, demand will not be met. On the other hand, when supply is higher than demand, energy will be wasted.
Increasing the amount of wind and solar above that
required to provide the nominal annual demand — overcapacity — reduces the supply gap, but only slowly. Even for renewable supply twice that of annual demand (1200TWh) there are still periods when demand is not met and some form of flexible back-up supply or energy storage will be required. The current means of compensating for fluctuations in demand and supply is largely fossil-fuelled — mostly CCGT — which are incompatible with the 2050 net-zero emissions target. Current CCGT power plants will be retired, probably before 2040. As well as supply not always matching demand, the wide range of power delivered by the renewable system is a problem. This excess in power could be more than 120GW, but occurring very infrequently — less than 0.2% of the time. All the options for compensating supply that are zero-
carbon have high capital costs and therefore are economic only when run constantly. The alternative is energy storage, which can compensate for renewable supply fluctuations, storing energy when output is high and releasing it when
demand is high. The key questions are: ● How much storage will be required? ● What will renewables plus storage cost in the future?
Energy storage for 2050 Energy storage exists today in the UK grid. Pumped hydro (25GWh with potential for 90GWh) has been used for many years, “peak lopping” daily power demands. More recently, battery systems (now totalling 1.3GW) are being used to provide short term grid services. They balance supply and demand for periods of seconds, minutes and a few hours. Though important, these systems are much too small (total
Renewable energy system capacity (GW) Solar
Onshore wind
2050 2021
Offshore wind 0 10 20 30 405060 70 80 90 100
22 | January 2022 |
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