The pivotal target of the Paris Agreement is to keep temperature rise well below 2 °C above the pre-industrial level and pursue efforts to limit temperature rise to 1.5 °C. To meet this target, all energy-consuming sectors, including the transport sector, need to be restructured. The transport sector accounted for 19% of the global final energy demand in 2015, of which the vast majority was supplied by fossil fuels (around 31,080 TWh). Fossil-fuel consumption leads to greenhouse gas emissions, which accounted for about 8260 MtCO_2eq from the transport sector in 2015. This paper examines the transportation demand that can be expected and how alternative transportation technologies along with new sustainable energy sources can impact the energy demand and emissions trend in the transport sector until 2050. Battery-electric vehicles and fuel-cell electric vehicles are the two most promising technologies for the future on roads. Electric ships and airplanes for shorter distances and hydrogen-based synthetic fuels for longer distances may appear around 2030 onwards to reduce the emissions from the marine and aviation transport modes. The rail mode will remain the least energy-demanding, compared to other transport modes. An ambitious scenario for achieving zero greenhouse gas emissions by 2050 is applied, also demonstrating the very high relevance of direct and indirect electrification of the transport sector. Fossil-fuel demand can be reduced to zero by 2050; however, the electricity demand is projected to rise from 125 TWh_el in 2015 to about 51,610 TWh_el in 2050, substantially driven by indirect electricity demand for the production of synthetic fuels. While the transportation demand roughly triples from 2015 to 2050, substantial efficiency gains enable an almost stable final energy demand for the transport sector, as a consequence of broad electrification. The overall well-to-wheel efficiency in the transport sector increases from 26% in 2015 to 39% in 2050, resulting in a respective reduction of overall losses from primary energy to mechanical energy in vehicles. Power-to-fuels needed mainly for marine and aviation transport is not a significant burden for overall transport sector efficiency. The primary energy base of the transport sector switches in the next decades from fossil resources to renewable electricity, driven by higher efficiency and sustainability.

Concerns related to climate change and global warming caused by anthropogenic activities and in particular fossil energy use have been increasing lately. Air pollution and volatile conventional fuel prices emphasize the need to transition the energy system towards very high shares of renewables. 100% renewable energy systems have been analyzed by many researchers starting from 1975. This bibliometric analysis reviews more than 600 scientific articles in which 100% renewable energy systems were surveyed. This study uses tools of bibliometric analysis, based on publication databases and data mining, together with review elements to understand the current status and trend of 100% renewable energy systems research. The focus of results is on quantitative parameters relating to number and publication types, collaborative links among authors, institutions, and countries. Collaborative networks provide the significant concentration of published papers within organizations and co-authorships globally. The results reveal that the dominant organizations and thus number of published papers are from Europe and the USA; however, almost all the established research organizations in the field of energy system analysis are not active in the field of 100% renewable energy systems analyses. The journals Energy and Applied Energy have the most articles, and accordingly the most citations. EnergyPLAN and LUT Energy System Transition Model have been the most active tools used to analyze 100% renewable energy systems according to numbers of articles and received citations. The topic of modeling approach indicates the term ’Energy System’ has the highest frequency due to its emergence in the articles. This research provides a holistic overview on the more than four decades of research, and it reveals dynamics within the field with a compound annual growth rate of articles of 26% for the 2010s, the trend of publications, and author growth that comprises now almost 1400 authors with articles in the field.

Globally, the heat sector has a major share in energy consumption and carbon emission footprint. To provide reliable mitigation options for space heating, domestic hot water, industrial process heat and biomass for cooking for the energy transition time frame up to the year 2050, energy system modeling relies on a comprehensive and detailed heat demand database in high spatial resolution, which is not available. This study overcomes this hurdle and provides a global heat demand database for the mentioned heat demand types and in a resolution of 145 mesoscale regions up to the year 2050 based on the current heat demand and detailed elaboration of parameters influencing the future heat demand. Additionally, heat demand profiles for 145 mesoscale regions are provided. This research finds the total global heat demand will increase from about 45,400 TWh_th in 2012 up to about 56,600 TWh_th in 2050. The efficiency measures in buildings lead to a peak of space heating demand in around 2035, strong growth in standards of living leads to a steady rise of domestic hot water consumption, and a positive trend for the worldwide economic development induces a growing demand for industrial process heat, counterbalanced by the efficiency gain in already industrialised countries. For the case of biomass for cooking, a phase-out path until 2050 is presented. Literature research revealed a lack of consensus on future heat demand. This research intends to facilitate a more differentiated discussion on heat demand projections.