Editing IPCC:AR6/WGIII/Chapter-9 (section)

=== 9.3.3 Energy Demand Trends ===

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Global final energy demand from buildings reached 128.8 EJ in 2019, equivalent to 31% of global final energy demand. The same year, residential buildings consumed 70% out of global final energy demand from buildings. Over the period 1990–2019, global final energy demand from buildings grew by 38%, with 54% increase in non-residential buildings and 32% increase in residential ones. At regional level, the highest increase of final energy demand occurred in Middle East and Africa in residential buildings and in all South-East Asia and Pacific in non-residential ones. By 2050, global final energy demand from buildings is projected to be at 86 EJ in IEA-NZE, 111 EJ in IEA-SDS and 138 EJ in IMAGE-LiRE. RECC-LED projects the lowest global final energy demand, at 15.7 EJ by 2050, but this refers to water heating, space heating and cooling in residential buildings only (Figure 9.7a).

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'''Figure 9.7: Final energy demand per fuel: historical based on IEA data and future emissions based on two IEA scenarios (sustainable development, and net zero emissions), IMAGE Lifestyle-Renewable scenario and Resource Efficiency and Climate Change-Low Energy Demand scenario (RECC-LED).''' RECC-LED data include only space heating and cooling and water heating in residential buildings. The IEA current policies scenario is included as a baseline scenario (IEA current policies scenario).

Over the period 1990–2019, the use of coal decreased at a global level by 59% in residential buildings and 52% in non-residential ones. Solar thermal experienced the highest increase, followed by geothermal and electricity. However, by 2019, solar thermal and geothermal contributed by only 1% each to global final energy demand, while electricity contributed by 51% in non-residential buildings and 26% in residential ones. The same year, gas contributed by 26% to non-residential final energy demand and 22% to residential final energy demand, which makes gas the second energy carrier used in buildings after electricity. Over the period 1990–2019, the use of gas grew by 75% in residential buildings and by 46% in non-residential ones. By 2050, RECC-LED projects electricity to contribute by 71% to final energy demand in residential buildings, against 62% in IEA-NZE and 59% in IMAGE-LiRE. IEA-NZE is the only scenario to project less than 1% of gas use by 2050 in residential buildings while the contribution of electricity to energy demand of non-residential buildings is above 60% in all scenarios. At regional level, the use of coal in buildings is projected to disappear while the use of electricity is projected to be above 50% in all regions by 2050 (Figure 9.7b).

Hydrogen emerged in the policy debate as an important energy carrier for the decarbonisation of the energy system. In the case of the building sector, depending on how hydrogen is sourced (Box 12.3), converting gas grids to hydrogen might be an appealing option to decarbonise heat without putting additional stress on the electricity grids. However, according to ( [[#Element%20Energy%20Ltd--2018|Element Energy Ltd 2018]] ; [[#Strbac--2018|Strbac et al. 2018]] ; [[#Frazer-Nash%20Consultancy--2018|Frazer-Nash Consultancy 2018]] ; [[#Broad--2020|Broad et al. 2020]] ; [[#Gerhardt--2020|Gerhardt et al. 2020]] ) the delivered cost of heat from hydrogen would be much higher than the cost of delivering heat from heat pumps, which could also be used for cooling. Repurposing gas grids for pure hydrogen networks will also require system modifications such as replacement of piping and replacement of gas boilers and cooking appliances, a factor cost to be considered when developing hydrogen roadmaps for buildings. There are also safety and performance concerns with domestic hydrogen appliances ( [[#Frazer-Nash%20Consultancy--2018|Frazer-Nash Consultancy 2018]] ). Over the period 1990–2019, hydrogen was not used in the building sector and scenarios assessed show a very modest role for hydrogen in buildings by 2050 (Figure 9.7).

In Developed Countries, biomass is used for generating heat and power leading to reduction of indirect emissions from buildings ( [[#Ortwein--2016|Ortwein 2016]] ) (IEA et al. 2020 c). However, according to ( [[#IEA--2019b|IEA 2019b]] ) despite the mitigation potential of biomass, if the wood is available locally, its use remains low in Developed Countries. Biomass is also used for efficient cook stoves and for heating using modern appliances such as pellet-fed central heating boilers. In developing countries, traditional use of biomass is characterised by low efficiency of combustion (due to low temperatures) leading to high levels of pollutants and CO output, as well as low efficiency of heat transfer. The traditional use of biomass is associated with public health risks such as premature deaths related to inhaling fumes from cooking ( [[#Dixon--2015|Dixon et al. 2015]] ; [[#Van%20de%20Ven--2019|Van de Ven et al. 2019]] ; [[#IEA--2019a|IEA 2019a]] ; [[#Taylor--2020|Taylor et al. 2020]] ). According to ( [[#Hanna--2016|Hanna et al. 2016]] ) policies failed in improving the use of biomass. Over the period 1990–2019, the traditional use of biomass decreased by 1% and all scenarios assessed do not project any traditional use of biomass by 2050. Biomass is also used for the construction of buildings, leading to low embodied emissions compared to concrete ( [[#Heeren--2015|Heeren et al. 2015]] ; [[#Hart--2020|Hart and Pomponi 2020]] ; [[#Pauliuk--2021|Pauliuk et al. 2021]] ).

Over the period 1990–2019, space heating was the dominant end-use in residential buildings at a global level, followed by water heating, cooking, and connected and small appliances (Figure 9.8a). However, energy demand from connected and small appliances experienced the highest increase, 280%, followed by cooking, 89%, cooling, 75%, water heating, 73% and space heating, around 10%. Space heating energy demand is projected to decline over the period 2020–2050 in all scenarios assessed. RECC-LED projects the highest decrease, 77%, of space heating energy demand, against 68% decrease in the IEA-NZE. IMAGE-LiRE projects the lowest decrease of heating energy demand, 21%. To the contrary, all scenarios confirm cooling as a strong emerging trend (Box 9.3) and project an increase of cooling energy demand. IMAGE-LiRE projects the highest increase, 143% against 45% in the IEA-NZE while RECC-LED projects the lowest increase of cooling energy demand, 32%.

There are great differences in the contribution of each end-use to the regional energy demand (Figure 9.8b). In 2019, more than 50% of residential energy demand in Europe and Eurasia was used for space heating while there was no demand for space heating in Middle East, reflecting differences in climatic conditions. To the contrary, the share of energy demand from cooking out of total represented 53% in the Middle East against 5% in Europe and Eurasia reflecting societal organisations. The highest contribution of energy demand from connected and small appliances to the regional energy demand was observed in 2019 in the Asia-Pacific Developed, 24%, followed by the region of Southern Asia, South-East Asia and Developing Pacific, with 17%. Energy demand from cooling was at 9% out of total energy demand of Southern Asia, South-East Asia and Developing Pacific and at 8% in both Middle East and North America while it was at 1% in Europe in 2019.

The increased cooling demand can be partly explained by the increased ownership of room air-conditioners per dwellings in all regions driven by increased wealth and the increased ambient temperatures due to global warming ( [[#Cayla--2011|Cayla et al. 2011]] ; [[#Liddle--2021|Liddle and Huntington 2021]] ) (Box 9.3). The highest increase, 32%, in ownership of room air-conditioners was observed in Southern Asia and South-East Asia and Developing Pacific while Europe, Latin America and Caribbean countries, Eastern Asia and Africa experienced an increase of 21% in households’ ownership of room air-conditioners. The lowest increases in room air-conditioners ownership were observed in the Middle East and North America with 1% and 8% each as these two markets are almost saturated. All scenarios assessed project an increase of ownership of cooling appliances in all regions over the period 2020–2050.

Energy demand from connected and small appliances was, at a global level, above 7 EJ in 2019 (Figure 9.8a). However, it is likely that global energy demand from connected and small appliances is much higher as reported data do not include all the connected and small appliances used by households and does not capture energy demand from data centres (Box 9.3). Over the period 1990–2019, the highest increase of energy demand from connected and small appliances, 4740%, was observed in Eastern Asia, followed by Southern Asia, 1358% while the lowest increase, 99%, occurred in Asia-Pacific Developed countries. The increase of energy demand from connected and small appliances is driven by the ownership increase of such appliances all over the world. The highest increase in ownership of connected appliances, 403%, was observed in Eastern Asia and the lowest increase in ownership of connected appliances was observed in North America, 94%. Future energy demand is expected to occur in the developing world given the projected rate of penetration of household appliances and devices ( [[#Wolfram--2012|Wolfram et al. 2012]] ). However, ( [[#Grubler--2018|Grubler et al. 2018]] ) projects a lower energy demand from connected and small appliances by assuming an increase of shared appliances and multiple appliances and equipment will be integrated into units delivering multiple services.

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'''Figure 9.8: Energy per end use: historical based on IEA data and future emissions based on two IEA scenarios (sustainable development, and net zero emissions), IMAGE Lifestyle-Renewable scenario and Resource Efficiency and Climate Change-Low Energy Demand scenario (RECC-LED).''' RECC-LED data include only space heating and cooling and water heating. The IEA current policies scenario is included as a baseline scenario (IEA current policies scenario).

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