There is significant uncertainty surrounding the structure of the global energy system in a net-zero world.
The composition of energy in Net Zero in 2050 may provide some insight: total final energy consumption (excluding non-combusted energy) is close to 10% lower than in Rapid; electricity, hydrogen and bioenergy together account for around 85% of end energy use; and CCUS plays a significant role.
But there are myriad transition paths to a net-zero world which will affect the eventual structure of the energy system and that structure is likely to continue to evolve even once it has reached net zero.
There are (at least) five sources of uncertainty surrounding the size and structure of a net-zero energy system:
These uncertainties are discussed in the rest of this section. The analysis is aided by considering the scenarios included in the IPCC Report which reach a net-zero energy system and considering the variation in outcomes across those scenarios (see IPCC scenario sample ranges for more detail).
The nature of a net-zero energy system will depend importantly on its overall size: how much energy is required for the global economy to continue to grow and prosper?
This depends partly on the extent to which it is possible to decouple energy consumption from economic activity, through either improving energy efficiency – producing the same goods and services with less energy – or reduced energy use – changing production and consumption patterns to make less demands on the energy system, e.g. through the expansion of circular and sharing economies.
The IPCC scenarios suggest a wide range for final end use of energy between 340-620 EJ in net zero. That compares with 425 EJ in 2018 and with 340 EJ in Net Zero in 2050 which is at the bottom of this range.
Global energy demand will also depend on the equality of energy access and use globally. In Net Zero, average energy consumption per capita in the developed world by 2050 is still more than twice that in emerging economies, with billions of people living in energy deficient countries and regions. To reduce that inequality, either overall energy provision would need to increase or energy consumption in developed economies fall further.
If regions with energy consumption per capita below EU levels increased to at least EU levels, global energy demand would be over 55% higher. This required increase falls to around 45% if regions with energy consumption per capital above EU levels reduced their average consumption levels to EU levels.
The size of the energy system will also be affected by the relative importance of different energy sources and carriers. In particular, the conversion process used to produce energy carriers such as electricity and hydrogen boosts primary energy. The range of primary energy in the IPCC net-zero scenarios is 550-1210 EJ – considerably more than total final consumption of energy.
Even if the vast majority of this primary energy is zero carbon, the overall footprint of the energy system is still likely to have wider implications due to the competing demands for (and environment impacts of) the materials, land and water it requires.
A net-zero energy system is likely to be characterized by a substantial increase in the electrification of energy-consuming activities, with the electricity generated from a fully decarbonized (or net negative) power sector.
But not all energy processes and uses can be technically or economically electrified, such as high-temperature industrial processes or long-distance transportation. In the IPCC net-zero scenarios, between 40-70% of end energy use is electrified; in Net Zero, a little over 50% of end energy use is electrified by 2050.
A fully decarbonized power sector is likely to be dominated by zero- and near-zero carbon energy sources, led by wind and solar power, together with nuclear, hydro and bioenergy; and other supporting technologies to ensure reliability. The intermittency of wind and solar power means the cost of balancing the power sector is likely to increase as the share of wind and solar power grows, slowing the extent to which they penetrate the power sector.
In the IPCC net-zero scenarios, wind and solar power provides between 40-85% of global power generation. In Net Zero, the share of wind and solar reaches a little above 60% in the early 2040s after which it begins to plateau.
A power system dominated by wind and solar power generation is likely to require a range of different energies and technologies to help balance their intermittency. For short-duration, high-frequency balancing, lasting from a few seconds to a few hours, this is likely to be met largely from a combination of batteries, pumped hydroelectricity and demand-side responses.
But some of these technologies and actions are unlikely to be technically or economically feasible for longer-duration balancing across multiple days, weeks and seasons. This longer-term balancing is likely to be met by a combination of bioenergy; natural gas (or coal) combined with CCUS; hydrogen; and hydroelectricity combined with high-capacity reservoirs. In Net Zero, bioenergy, natural gas with CCUS, hydro and hydrogen collectively account for 30% of power generation in 2050.
The use of both oil and natural gas in a net-zero energy system is likely to decline substantially from current levels.
Oil consumption in the IPCC net-zero scenarios declines to between 70-10 Mb/d, around 30-90% below current levels. Oil consumption falls to around 25 Mb/d in Net Zero by 2050, of which 10 Mb/d is used in the transport sector, mainly for long-distance transportation in trucking, aviation and marine. It is likely that this use in transport will decline further over time, as legacy vehicles and infrastructure are increasingly replaced with alternative technologies and energy sources.
Outside of transport, most of the remaining oil in Net Zero in 2050 is used in the non-combusted sector for petrochemical feedstock and other industrial uses. Although this use of oil does not lead to carbon emissions at the point of use – since the oil is not combusted – the use and ultimate end of life consumption or disposal of the products which the oil is used to produce, such as plastics, may well generate carbon emissions over their life cycle. And, depending on how those activities are conducted, may also lead to other environmental issues. This may put further pressure on oil use over time.
Natural gas consumption in the IPCC net-zero scenarios in 2050 varies between 3800 Bcm – similar to 2018 – and 1000 Bcm, a decline of 75% from current levels. In Net Zero, natural gas is around 2300 Bcm in 2050 providing energy across all the main sectors of the economy – either directly or via blue hydrogen.
By 2050, around three-quarters of the natural gas which is combusted in Net Zero is used in conjunction with CCUS. This share is likely to grow further over time, either as the build out of CCUS expands or alternative low or zero-carbon energy sources become increasingly available and replace unabated natural gas.
Bioenergy and hydrogen – alongside electricity – are likely to play an increasing role in a net-zero energy system.
The use of bioenergy in the IPCC net-zero scenarios ranges from 40-155 EJ; this compares with around 55 EJ in Net Zero by 2050, where it accounts for close to 10% of primary energy.
A little over half of the bioenergy used in Net Zero is in the form of biomass, which is mainly used as a flexible feedstock in the power sector and to fuel high-temperature industrial processes. Biofuels account for almost another 30%, used largely in long-distance transportation, helped by their portability and high energy density. The remainder is biomethane which is consumed across all sectors as a replacement for natural gas.
The use of bioenergy in a net-zero energy system will depend on the cost and feasibility of producing bioenergy at scale, together with other environmental and social factors, such as the extent of competition with other land uses and its impact on biodiversity.
Hydrogen as an energy carrier reaches around 60 EJ in Net Zero by 2050, providing around 15% of total final consumption (excluding the non-combusted use of fuels). This is at the top of the range of IPCC net-zero scenarios (15-60 EJ), which may reflect that many of the IPCC scenarios were compiled before the increase in policy and private-sector interest in hydrogen over the past few years.
The versatility of hydrogen means it is used in all sectors of the economy in Net Zero by 2050, especially in high-temperature industrial processes; long-distance road and marine transportation; and as a form of storage and flexible energy source in the power and buildings sectors.
The production of hydrogen in Net Zero by 2050 is roughly even split between green and blue hydrogen (see Hydrogen).
Technologies which capture carbon emissions or extract them from the atmosphere are likely to play a material role in a net-zero environment.
In the IPCC net-zero scenarios, the use of CCUS ranges between 8-18 Gt CO2, which is roughly equivalent to capturing and sequestering between a quarter and a half of all current carbon emissions from energy use. This range is higher than in Net Zero, where CCUS reaches a little over 5 Gt CO2 by 2050.
Although CCUS facilities capture a vast majority of carbon emissions, current technologies don’t have a 100% capture rate. The average efficiency rate assumed in Net Zero is around 90%, implying residual carbon emissions from CCUS operations of around 0.5 Gt CO2.
CCUS can be combined with bioenergy (BECCS) in the power and industrial sectors to create a negative-emissions energy source. In the IPCC net-zero scenarios, the negative emissions produced using BECCS range from 5-10 Gt CO2. Again, this is higher than in Net Zero, where the negative emissions from BECCS reach around 1.5 Gt CO2 by 2050.
There are a variety of other negative emission technologies (NETs). These technologies are not modelled explicitly in Net Zero, which explores a possible pathway in which the energy system almost fully decarbonizes without significant use of NETs. Even so, these NETs may play an increasingly important role as the world seeks to reduce all GHG emissions to net zero, offsetting any continuing emissions from hard-to-abate sources in the energy system and the wider economy, such as agriculture, as well as any overshoots in the carbon budget.
In particular, natural climate solutions (NCS), which includes forest and peat restoration and various forms of enhanced land management, generate emissions savings in the IPCC net-zero scenarios ranging from -3 to +7 Gt CO2e (where the ‘negative saving’ reflect the risk that land use deteriorates over time adding to emissions).
There are other NETs, such as direct air capture and biochar which, although not explicitly included in Net Zero, may also play a material role in balancing total GHGs as the world moves to net zero.